US20160028441A1 - System and method of wirelessly communicating with mobile devices - Google Patents

Abstract

Systems and methods for providing network access to mobile devices that travel with a vehicle, such as a train, a bus, a boat. etc. along or adjacent to a relatively fixed path that may extend over a large geographic area. Mobile devices access the network through stationary access points arranged along or adjacent to the path and communicate with a communication network. The communication network may be arranged as an asynchronous transfer mode (ATM) local area network emulation (LANE) network. One of the mobile devices may be a mobile access point which can couple other mobile devices to the network and record authentication information of other mobile devices so that fast transitions can be made from one stationary access point to another as the vehicle moves along the path.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• The instant application is a continuation under 35 USC §120 of U.S. patent application Ser. No. 12/841,491 filed Jul. 22, 2010, which is a continuation of U.S. patent application Ser. No. 11/839,992 filed Aug. 16, 2007, which claims priority under 35 U.S.C. §119(e) to U.S. provisional patent application No. 60/838,752 filed Aug. 18, 2006 and titled SYSTEM AND METHOD OF WIRELESSLY COMMUNICATING WITH MOBILE DEVICES, each of which is incorporated herein by reference. The instant application is related to the following U.S. Pat. No. 7,787,402 titled SYSTEM AND METHOD OF AUTHENTICATING MOBILE DEVICES, granted on Aug. 31, 2010, U.S. Pat. No. 8,755,804 titled SYSTEM FOR PROVIDING REDUNDANT COMMUNICATION WITH MOBILE DEVICES, granted on Jun. 17, 2014, and U.S. Pat. No. 7,916,080 titled ANTENNA SYSTEM FOR COMMUNICATING WITH MOBILE DEVICES, granted on Mar. 29, 2011.
BACKGROUND
• 1. Field of Invention
• The present invention relates to wireless communication and more particularly to wireless communication with a plurality of mobile devices.
• 2. Discussion of Related Art
• Wireless networks provide mobility and convenience to users of various mobile devices. Such networks have become pervasive and may now be found in homes, workplaces, and even public and commercial spaces such as parks and coffee shops. Wireless network access is generally limited in range to an area relatively near a wireless access point. In public or commercial spaces, the area in which a wireless network is accessible is often referred to as a wireless hotspot. One popular wireless networking technology is referred to as Wi-Fi and is defined by the various IEEE 802.11 specifications.
• A typical wireless network user may connect to a different wireless network in his or her home, at a local restaurant or coffee shop, and at his or her workplace. The user may also connect to a single wireless network through different access points as the user moves from one location to another, for example, as the user moves from one floor of an office building serviced by one wireless router to another floor of the same office building serviced by a different wireless router. Each connection to a new wireless network or a new access point generally requires establishing a new connection to the network. This may include authenticating the user and mobile device to a network authentication server before the user is allowed to fully access the network. When users are moving relatively quickly, such as when they are traveling along with a vehicle, such reauthentication may cause gaps in network connectivity.
• Moreover, wireless networking may be limited by the active range of a wireless access point. So users may experience limited mobility based on the positioning and strength of a wireless access point through which they couple to a communication network. This range may be altered by environmental features, such as tunnels, walls, buildings, geography, etc, further limiting the range of wireless networks.
SUMMARY OF INVENTION
• In accordance with one aspect of the present invention, it is recognized that establishing a new connection to a wireless network as a user moves among networks or access points may cause a break in network access leaving the user temporarily without network access. To help prevent such breaks in network access, a communication network may be configured to minimize the time needed to establish a new connection to the network. This may be accomplished, for example, by reducing the time needed to authenticate a user or mobile device with a network authentication server, or, for another example, by arranging access points into authentication groups having a shared authentication cache that may provide some authentication without communicating with the authentication server.
• To further prevent such network access breaks, access points of a communication network may be disposed so that the range of each access point overlaps with the range of a neighboring access point. The overlap may be great enough so the mobile device may complete establishing a connection through the neighboring access point before leaving the range of the access point through which the mobile device currently accesses the network. Such an arrangement may allow a user to travel among neighboring access points without experiencing a break in network access.
• In accordance with one aspect of the present invention, it is realized that mobile device users traveling on or in a vehicle along a path may desire wireless network access without access interruptions. For example, a plurality of users traveling on or in a vehicle, such as a train, boat, car, etc., moving from one location to another, such as from one train station to another, may want to access such a wireless network to check email, surf the web, access a work related virtual private network (VPN), etc. To facilitate such network access, a plurality of stationary access points may be arranged along or adjacent to the path traveled by the vehicle. The path and network may, thereby, span a large geographic area, such as from one city to another or from one state to another.
• The plurality of stationary access points may be connected to each other and the network by wired or wireless communication methods. Each stationary access point of the plurality of stationary access points may be configured to forward data among the mobile devices and the network. Each stationary access point may be arranged to maintain a line of sight and a wireless communication channel with the mobile devices while they are in a communication range of the stationary access point to improve access quality as the mobile devices move along the path.
• In accordance with one aspect of the present invention, it is recognized that establishing a new connection for a plurality of mobile devices at nearly the same time, such as when a vehicle carrying the plurality of mobile devices moves from one stationary access point to a new stationary access point, may delay the establishment of some of the new connections, for example because a bandwidth limit may be reached or an authentication server may be overwhelmed with authentication requests for each device of the plurality of mobile devices. To prevent such delay, the mobile device may include a mobile access point that is coupled to the vehicle and travels along with one or more other mobile devices, such as a mobile host device (e.g., a laptop, a PDA, a cellular telephone, etc.) or a mobile forwarding device (e.g., a router, a bridge, a switch, a repeater, etc.). The mobile access point may connect to the stationary access points disposed along the path. The other mobile devices may connect to the mobile access point in order to access the network associated with the stationary access points.
• The mobile access point may record connection information, such as authentication information, for each mobile host device of the plurality of mobile host devices so that the mobile host devices can move among the access points without needing to reauthenticate or establish a new connection to a stationary access point. Rather, in such a configuration, the mobile access point may be the only device that may need to authenticate and establish such a new connection when the mobile host devices and mobile access point move among stationary access points, thereby limiting the amount of authentication and other new connection related traffic.
• In accordance with another aspect of the present invention, it is recognized that certain types of network connection (e.g., secure socket layer (SSL), VPN, etc.) may depend upon a static network layer address (e.g., IP address) that may not be maintained as a user moves among access points of a conventional wireless network, especially a wireless network that spans a large geographic area. To maintain such network layer addresses as a mobile host device moves from one stationary access point to another of a communication network, devices of the communication network may be configured to transparently forward information through the communication network based on data link layer address information. For example, the communication network may be configured as an asynchronous transfer mode (ATM) local area network emulation (LANE) having virtual circuits connecting the mobile devices through the network. Such a configuration may allow mobile devices to maintain one network layer address as the devices travel among multiple stationary access points by updating the virtual circuits as the devices move.
• Wireless communication used in various embodiments of the present invention may include any type of wireless communication between two or more devices without any direct mechanical attachment, such as radio frequency or optical communication. An example wireless communication that may be used includes any of the well-known IEEE 802.11 protocols.
• Another aspect of the present invention includes a communication system. In some embodiments, the communication system comprises a plurality of stationary access points coupled to a communication network, and a mobile access point configured to communicate with the plurality of stationary access points and provide a plurality of host devices access to the communication network without address renegotiation, wherein the mobile access point and the plurality of host devices move relative to the plurality of stationary access points.
• In one embodiment, the mobile access point communicates with at least one of the plurality of host devices using a wireless network. In another embodiment, the mobile access point communicates with the plurality of stationary access points using a wireless network. In some implementations, the wireless network may include a wireless network using an IEEE 802.11 protocol.
• In some embodiments, the mobile access point is configured to provide the plurality of host devices access to the communication network through the wireless network to one stationary access point of the plurality of stationary access points at a time. In some implementations, the one stationary access point is a stationary access point of the plurality of stationary access points that provides a stronger wireless communication signal to the mobile access point than at least one other stationary access point of the plurality of stationary access points. In other embodiments, to provide access to the communication network to at least one of the plurality of host devices, the mobile access point communicates through a wireless network with a mobile forwarding device.
• In some embodiments, the communication network is connected to an external communication network by a forwarding device. In some implementations, the forwarding device includes an edge router. In further implementations, data addressed to a network layer address of a first host device of the plurality of host devices and received by the forwarding device from the external communication network is forwarded from the forwarding device to the first host device through the mobile access point and at least one of the plurality of stationary access points based on a data link layer address of the first host device.
• In other embodiments, the plurality of host devices includes at least one of a laptop computer, a personal digital assistant (PDA), and a cellular telephone. In still other embodiments, at least one of the plurality of stationary access points couples to the communication network through a wired connection. In further embodiments, a first stationary access point of the plurality of stationary access points couples to the communication network through a second stationary access point of the plurality of stationary access points. In some implementations, the first stationary access point couples to the communication network using a wired network to the second stationary access point. In other implementations, the first stationary access point couples to the communication network using a wireless network to the second stationary access point.
• In some embodiments, the mobile access point is coupled to a vehicle. In some implementations, the vehicle includes at least one of a boat, a train, a bus, and a car. In one implementation, the vehicle moves along a path, and the plurality of stationary access points are arranged adjacent to the path.
• Another aspect includes a method of forwarding data to a moving host device. In some embodiments, the method comprises acts of maintaining, in a first forwarding device of a plurality of forwarding devices of a communication network, forwarding information for the moving host device based on a data link layer address of the moving host device, receiving data addressed to a network layer address of the moving host device at the first forwarding device, and forwarding a representation of at least a portion of the received data along a path to the data link layer address of the moving host device based on the maintained forwarding information.
• Some embodiments further comprise an act of addressing, at the first forwarding device, the representation of at least the portion of the received data to the data link layer address of the moving host device. In other embodiments, the act of maintaining comprises an act of establishing a new virtual circuit through at least a portion of a new path from the first forwarding device to the moving host device when the path to the moving host device from the first forwarding device changes. In some implementations, the first forwarding device includes a mobile access point.
• In some embodiments, the first forwarding device includes at least one stationary access point. In some implementations, the at least one stationary access point includes a first stationary access point when the moving host device is in a first position and a second stationary access point when the moving host device is in a second position. One implementation further comprises establishing a first wireless connection between the first stationary access point and a mobile access point when the moving host device is in the first position and establishing a second wireless connection between the second stationary access point and the mobile access point when the moving host device is in the second position.
• In other embodiments, the moving host device includes at least one of a laptop computer, a personal digital assistant (PDA), and a cellular telephone. In still other embodiments, the act of maintaining includes acts of sending, responsive to the path to the moving host device from the first forwarding device changing, updated forwarding information to the first forwarding device through the communication network along at least a portion of the changed path; and associating, at any forwarding devices along the portion of the changed path and the first forwarding device, the updated forwarding information with the moving host device. In some implementations, the act of associating includes an act of establishing a new virtual circuit from the mobile host device to the first forwarding device. In some embodiments, the act of forwarding comprises an act of forwarding a plurality of asynchronous transfer mode (ATM) cells, wherein each of the cells includes at least a portion of the representation of the portion of the received data. In other embodiments, the act of forwarding comprises an act of forwarding the representation using A TM local area network emulation (LANE) to the moving host device.
• A further aspect includes a communication system comprising a first antenna system comprising a plurality of first antennas mounted to a first supporting structure, each of the plurality of first antennas having a main lobe oriented in a different direction; and a second antenna system comprising a plurality of second antennas mounted to a second supporting structure, each of the plurality of second antennas having a main lobe oriented in a different direction, the main lobe of at least one of the plurality of second antennas being oriented in a direction opposing the main lobe of at least one of the plurality of first antennas, wherein the first antenna system and the second antenna system are disposed at spaced apart positions along or adjacent to a path traversed by a vehicle, such that the vehicle does not substantially obstruct the main lobes of the plurality of first antennas or the plurality of second antennas as the vehicle traverses the path.
• In some embodiments, at least 40% of energy radiated from a first antenna of the plurality of first antennas and from a second antenna of the plurality of second antennas is not obstructed by the vehicle as the vehicle traverses the path. In other embodiments, the first antenna system includes at least one of a battery and a solar power supply configured to power the plurality of first antennas.
• Still other embodiments further comprise a mobile antenna coupled to the vehicle, wherein the first antenna system is configured to communicate with the mobile antenna through at least one of the plurality first antennas when the mobile antenna is within a communication range of the first antenna system, and the second antenna system is configured to communicate with the mobile antenna through at least one of the plurality of second antennas when the mobile antenna is within a communication range of the second antenna system. In some implementations, the communication range of the first antenna system overlaps the communication range of the second antenna system. In other implementations, each of the first and second antenna systems is coupled to a communication network. In some implementations, the first antenna system is coupled to the communication network through a wired connection. In some implementations, the second antenna system is coupled to the communication network through the first antenna system. In one implementation, the second antenna system is coupled to the communication network through the first antenna system by a wired connection to the first antenna system. In other implementations, the second antenna system is coupled to the communication network through the first antenna system by a wireless network with the first antenna system. In one implementation, the first antenna system includes at least one third antenna communicating over the wireless network to at least one fourth antenna of the second antenna system to couple the second antenna system to the communication network through the first antenna system. In another implementation, the wireless network includes a wireless network using an IEEE 802.11 protocol.
• In other embodiments, the mobile antenna is coupled to a mobile access point configured to provide a plurality of host devices access to the communication network through communication with the first and second antenna systems. In still other embodiments, the plurality of host devices includes at least one of a laptop computer, a personal digital assistant (PDA), and a cellular telephone. In yet further embodiments, the mobile access point is configured to provide access to the communication network through the first antenna system when a first signal strength of the first antenna system is stronger than a second signal strength of the second antenna system. In some implementations, the mobile access point is configured to provide access to the communication network through the second antenna system when the second signal strength is stronger than the first signal strength. In other implementations, the mobile access point is configured to authenticate with the second antenna system before the second signal strength is stronger than the first signal strength. In some other implementations, the mobile access point communicates with the first and second antenna systems through a wireless network. In one implementation, the wireless network includes a wireless network using an IEEE 802.11 protocol.
• In further embodiments, the mobile access point communicates with the plurality of host devices through at least one wireless network. In one implementations, the wireless network includes a wireless network using an IEEE 802.11 protocol.
• Yet a further aspect includes an antenna system for communicating with a mobile device, comprising a support; a plurality of first antennas mounted to the support, each first antenna of the plurality of first antennas being configured to communicate with the mobile device when the mobile device is more than a minimum communication distance from the support and less than a maximum communication distance from the support; and at least one second antenna mounted to the support and configured to communicate with the mobile device when the mobile device is less than the minimum communication distance from the support.
• In some embodiments, the communication system further comprises at least one connection device coupled to the support and configured to communicate with a communication network. In some implementations, the mobile device includes a mobile access point and the communication system is configured to provide access to the communication network to a plurality of host devices coupled to the mobile access point by communicating with the mobile access point through at least one of the plurality of first antennas and the at least one second antenna.
• In other embodiments, the at least one connection device comprises a plurality of third antennas mounted to the support. In some implementations, at least one antenna of the plurality of third antennas is configured to communicate with at least one second communication system. In some implementations, the at least one antenna of the plurality of third antennas is configured to communicate with the communication network through a wireless network with the at least one second communication system. In one implementation, the wireless network includes a wireless network using an IEEE 802.11 communication protocol.
• In other embodiments, the at least one connection device comprises a wired connection to the communication network. In one implementation, the wired connection includes at least one of a wire and an optical fiber. In other implementations, the wired connection connects the communication system to a forwarding device coupled to the communication network. In still other implementations, the wired connection to the communication network includes at least one wired connection to at least one second communication system. In another embodiment, the plurality of first antennas are parabolic dish antennas and the at least one second antenna is an omnidirectional antenna.
• A still further aspect of the present invention includes a mobile communication system comprising a first communication system configured to communicate with at least one host device; and a second communication system configured to communicate with a plurality of stationary access points and the first communication system, wherein the mobile communication system is configured to authenticate the second communication system with a first stationary access point of the plurality of stationary access points by authenticating the second communication system with an authentication server, and wherein the mobile communication system is further configured to authenticate the second communication system with a second stationary access point of the plurality of stationary access points without reauthenticating the second communication system with the authentication server.
• In some embodiments, the mobile communication system is configured to authenticate the second communication system with the second stationary access point by accessing an authentication cache indicative of whether the second communication system has previously been authenticated by the authentication server. In other embodiments, the second communication system and the plurality of stationary access points communicate wirelessly.
• In still other embodiments, the first communication system is configured to provide, to the at least one host device, access to a communication network coupled to the plurality of stationary access points. In some implementations, the first communication system is configured to communicate with the at least one host device using a wireless communication network. In other implementations, the first communication system is configured to communicate with the at least one host device through at least one mobile forwarding device.
• In yet further embodiments, the second communication system is configured to communicate with the plurality of stationary access points without address renegotiation of the second communication system. In even further embodiments, the second communication system is configured to couple to a communication network through a different respective one of the plurality of stationary access points as the mobile communication system moves. In one implementation, the second communication system is configured to select a current one of the plurality of stationary access points through which to couple to the communication network based, at least in part, on a signal strength of a communication signal between the second communication system and the plurality of stationary access points.
• In a further embodiment, the mobile communication system is coupled to a vehicle. In one implementation, the vehicle includes at least one of a boat, a train, a bus, and a car, and the at least one host device includes at least one of a laptop computer, a personal digital assistant, and a cellular telephone.
• Another aspect includes a method of authenticating a mobile device. In one embodiment, the method comprises receiving an authentication request from the mobile device at a first stationary access point; authenticating the mobile device to the first stationary access point by requesting authentication from an authentication server; storing authentication information identifying the mobile device in an authentication cache associated with the first stationary access point and at least one second stationary access point; receiving an authentication request from the mobile device at the at least one second stationary access point; and authenticating the mobile device to the second stationary access point by referencing the stored authentication information.
• In some embodiments, authenticating the mobile device to the at least one second stationary access point takes less than about 2 milliseconds. Some embodiments further comprise grouping the first stationary access point and the at least one second stationary access point so that the stored information identifying the mobile device can be provided to each at least one second stationary access point in the group by referencing the stored authentication information and without requesting further authentication from the authentication server. In one implementation, grouping includes maintaining the authentication cache in a WLCCP controller and permitting authentication access to the WLCCP controller by each of the first stationary access point and each of the at least one second stationary access point.
• Some embodiments of this aspect further comprise providing access to a communication network coupled to the first stationary access point and the at least one second stationary access point to the mobile device. In some implementations, providing access to the communication network includes maintaining forwarding information for the mobile device based on a data link layer address of the mobile device. One implementation further comprises forwarding information addressed to a network layer address of the mobile device to the mobile device based on the maintained forwarding information. In other implementations, providing access includes providing access without address renegotiation by the mobile device.
• In some embodiments, requesting authentication from the authentication server includes requesting authentication from a RADIUS server. In other embodiments, the mobile device traverses a path proximate the first stationary access point and the at least one second stationary access point at an average rate of travel, and the act of storing the authentication information includes storing the authentication information for a period of time sufficient to allow the mobile device to traverse the path at the average rate of travel. In some implementations, authenticating the mobile device with the authentication server takes less than about 100 milliseconds.
• Other embodiments further comprise providing access to a communication network coupled to the first stationary access point and the at least one second stationary access point to a plurality of host devices coupled to the mobile device. In some implementations, providing access to the communication network includes maintaining forwarding information corresponding to each respective host device of the plurality of host devices based on data link layer addresses of the respective host device. One implementation further comprises forwarding information addressed to a network layer address of a first host device of the plurality of host devices to the first host device based upon the maintained forwarding information corresponding to the first host device. In other implementations, providing access includes providing access without address renegotiation by the mobile device.
• An even further aspect of the present invention includes a communication system for communicating with a mobile device. The communication system comprises a plurality of antenna systems, each respective antenna system of the plurality of antenna systems being configured to communicate with the mobile device when the mobile device is within a communication range of the respective antenna system, wherein the plurality of antenna systems are disposed at spaced apart positions along a path traversed by the moving vehicle so that the mobile device is within a communication range of at least one antenna system of the plurality of antenna systems as it traverses the path and a line of sight is maintained between the mobile device and the at least one antenna system of the plurality of antenna systems.
• In some embodiments, the mobile device is a mobile access point configured to provide network access to a plurality of host devices by communicating with the at least one antenna system of the plurality of antenna systems. In other embodiments, the plurality of host devices includes at least one of a laptop computer, a personal digital assistant (PDA), and a cellular telephone. In still other embodiments, the mobile access point is configured to provide network access to the plurality of host devices by communicating with the at least one antenna system of the plurality of antenna systems through a wireless communication network. In some implementations, the wireless communication network includes a wireless network using an IEEE 802.11 communication protocol.
• In further embodiments, a subset of the plurality of antenna systems is configured as an antenna group that includes an antenna group controller to facilitate low latency movement of the mobile device from communication with a first antenna system of the subset of antenna systems to communication with a second antenna system of the subset of antenna systems. In some implementations, the subset of antenna systems is arranged along an external portion of a curve in the path. In other implementations, the antenna group controller facilitates movement of the mobile device from communication with the first antenna system of the subset of antenna systems to communication with the second antenna system of the subset of antenna systems by authenticating the mobile device to the second antenna system. In one implementation, the antenna group controller includes at least one WLCCP controller. In another implementation, the antenna group controller includes an authentication cache, and authenticating the mobile device to the second antenna system includes querying the authentication cache.
• In still further embodiments, the plurality of antenna systems are disposed at spaced apart positions along the path traversed by the moving vehicle so that the mobile device is within the communication range of at least two antenna systems of the plurality of antenna systems as it traverses the path and a line of sight is maintained between the mobile device and the at least two antenna systems of the plurality of antenna systems.
• Another aspect of the present invention includes a communication system for communicating with at least one mobile device, comprising: a plurality of antenna systems, each respective antenna system of the plurality of antenna systems being configured to communicate with the mobile device when the mobile device is within a communication range of the respective antenna system, wherein the plurality of antenna systems are disposed at spaced apart positions along a path traversed by the mobile device and positioned relative to one another so that when a first antenna system of the plurality of antenna systems that is closest to the mobile device cannot communicate with the mobile device, the mobile device can communicate with at least one working second antenna system of the plurality of antenna systems that is disposed adjacent to the first antenna system.
• In some embodiments, the communication range of the first antenna system overlaps with the communication range of the at least one working second antenna system. In other embodiments, the at least one working second antenna system includes a plurality of working second antenna systems. In some implementations, the communication range of each of the plurality of working second antenna systems includes a communication range overlap in which the communication range of a first of the plurality of working second antenna systems overlaps the communication range of a second of the plurality of working second antenna systems. In this implementation, the communication overlap includes an area in which the mobile device may complete a connection process to each of the plurality of working second antenna systems. In one implementation, the connection process includes an authentication process.
• Another aspect includes a mobile access point configured to provide access to a communication network to a plurality of host devices, wherein the communication system is configured to determine a geographic location of the plurality of host devices based, at least partially, on a determination of a geographic location of the mobile access point.
• In some embodiments, the determination of the geographic location of the mobile access point is based on the location of a global positioning device coupled to the mobile access point.
• In some implementations, the mobile access point is configured to provide access to the communication network by communicating with at least a subset of a plurality of stationary access points coupled to the communication network. In other implementations, the subset of the plurality of stationary network access points changes as the mobile access point moves relative to the plurality of stationary access points.
• In other embodiments, the determination of the geographic location of the mobile access point is based, at least partially, on the known geographic location of the subset of the plurality of stationary access points communicating with the mobile access point. In some implementations, the determination of the geographic location of the mobile access point is based, at least partially, on at least one characteristic of at least one wireless communication signal between the subset of the plurality of stationary access points and the mobile access point. In one implementation, the at least one characteristic of the at least one wireless communication signal is a signal strength. In another implementation, the signal strength includes a signal strength of at least one wireless network used by the mobile access point to communicate with the plurality of stationary access points.
• In some embodiments, information is delivered to the plurality of host devices based on the determined geographic location of the plurality of host devices. In some implementations, the plurality of host devices includes at least one of a laptop computer, a personal digital assistant (PDA), or a cellular telephone.
• Further features and advantages of the present invention as well as the structure and operation of various embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the drawings, like reference numerals indicate functionally similar elements. Additionally, the left-most one or two digits of a reference numeral identifies the drawing in which the reference numeral first appears.
BRIEF DESCRIPTION OF THE DRAWINGS
• The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:
• FIG. 1A illustrates an example communication network coupled to a plurality of stationary access points consistent with principles of the present invention;
• FIG. 1B illustrates a geographically wide network communicating as a local area network consistent with principles of the present invention;
• FIG. 2 illustrates a view of a first exemplary stationary access point consistent with principles of the present invention;
• FIG. 3 illustrates a view of a second exemplary stationary access point consistent with principles of the present invention:
• FIG. 4 illustrates a view of a third exemplary stationary access point consistent with principles of the present invention;
• FIG. 5 illustrates a vehicle traveling near a plurality of stationary access points consistent with principles of the present invention;
• FIGS. 6A, and6B illustrate example leaky coaxial cable hangers that may be used in some embodiments;
• FIG. 7 illustrates a train traveling near a plurality of stationary access points consistent with principles of the present invention;
• FIG. 8 illustrates a flow chart of an example process performed by a stationary access point consistent with principles of the present invention; and
• FIG. 9 illustrates a flow chart of an example process performed by a mobile access point consistent with principles of the present invention.
DETAILED DESCRIPTION
• Various aspects of the invention are not limited in their application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. Aspects of the invention are capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
• The present invention relates generally to providing network access to mobile devices. Some aspects of the invention relate to mobile devices traveling with a vehicle, such as a train, a bus, a boat, etc., along or adjacent to a relatively fixed path. Network access may be provided to the mobile devices through a plurality of stationary access points that are arranged along or adjacent to the path.
• In one aspect of the present invention, one of the mobile devices may include a mobile access point. The mobile access point may be used to couple one or more other mobile devices to the network. In another aspect of the present invention, the mobile access point may record authentication information of the one or more other mobile devices so that a relatively fast transition can be achieved among stationary access points as the vehicle and thereby the mobile devices move along the path, as described in more detail below.
• In effect, the combination of various aspects of the present invention may result in one moving network, which comprises the mobile access point and one or more other mobile devices such as mobile host devices and/or mobile forwarding devices, and one stationary network, which comprises the stationary access points and other elements, such as servers, forwarding devices, etc. The moving network may move relative to the stationary network and may couple to the stationary network to gain access to resources of the stationary network. Such coupling may result in the mobile devices coupled to the moving network having access to the stationary network without experiencing serious, if any, delays or renegotiating network addresses.
• In accordance with one aspect of the present invention, one ormore servers103 may be coupled to acommunication network101, as illustrated inFIG. 1A. The plurality ofservers103 may provide one or more network services to devices coupled tocommunication network101. The plurality ofservers103 may include anauthentication server105, aregistration server107, a dynamic host configuration protocol (DHCP)server109, a structured query language (SQL)server111, a network maintenance and/ormonitoring server113, acontent server115, and any other server configured to provide functionality tocommunication network101 and/or devices coupled tocommunication network101.
• Any of the servers may be configured as a single device, such as a single general purpose computer, or a cluster of devices, such as plurality of blades. In some embodiments of the present invention,authentication server105 may include a well-known remote authentication dial in user service (RADIUS) authentication server. According to one aspect of the present invention, it is appreciated that as any mobile device moves among networks or network access points, an authentication process may be performed by the new network or network access point. However, such an authentication may conventionally involve an unacceptable delay that may result in a loss of network access while the device awaits authentication.
• To improve speed of authentication, which may cause interruptions in network access, in some embodiments of the present invention,authentication server105 may limit responses to an authentication request to either a positive acknowledgement or a negative rejection of the authentication request. To further improve the speed of authentication,authentication server105 may be configured to perform a limited specialized set of operations, for example, receive an authentication request fromcommunication network101, convert the data of the received request directly into a SQL query, execute the SQL query locally or through anetworked SQL server111, convert the result of the SQL query into an authentication response, and transmit the response throughcommunication network101. In accordance with one embodiment,authentication server105 may be configured to respond to authentication requests at a speed sufficient to prevent an interruption of service as a mobile device moves between one stationary access point and another, as described in more detail below. The needed speed of authentication may vary based on the movement speed of the mobile device and any overlap in the communication regions of the relevant stationary access points, as is discussed below. In one implementation,authentication server101 may be configured to respond to an authentication request in less than approximately 100 milliseconds.
• A plurality of forwardingdevices117,119 may also be coupled tocommunication network101. The plurality of forwardingdevices117,119 may include routers, switches, bridges, gateways, repeaters, access points, and any other device configured to receive data and forward data towards a destination of the data. Each forwarding device may be configured to direct data from a source towards a destination throughcommunication network101. Data directed from one location to another location throughcommunication network101 may pass through many such forwarding devices.
• Each forwarding device may determine how to forward information to its intended destination. This determination may cause an unwanted delay in the transmission of the information to the destination. In some implementations of the present invention, forwardingdevices117,119 may be configured to forward data using a well-known forwarding technique based on a network layer (e.g., layer 3 of the open systems interconnection (OSI) model) whereby the direction of data may be determined by the network layer address (e.g., internet protocol (IP) address) of the destination. In other implementations of the present invention, forwardingdevices117,119 may be configured to forward data based on the data link layer (e.g., layer 2 of the OSI model) whereby the direction of data may be determined by the data link layer address (e.g., media access control (MAC) address) of the destination. Use of data link layer forwarding techniques may improve forwarding speed compared with network layer forwarding techniques because data link layer forwarding techniques may not include a step of examining network layer destination information. Further, it is appreciated that if a geographically dispersed network is created in the same network layer, client addressing using network layer information does not change as clients change location within the network. Such stable network addressing reduces lost packets and the need to renegotiate addresses as a client moves.
• Forwarding information based on data link layer information is often referred to as MAC-layer bridging or switching. Forwarding information based on network layer information is often referred to as routing. Any reference to forwarding or forwarding techniques includes directing data in any fashion, including, but not limited to, by data link and/or network layer information.
• One data link layer forwarding technique that may be used by forwardingdevices117,119 to forward data throughcommunication network101 is asynchronous transfer mode (ATM) switching. Use of ATM switching may provide a high speed method of forwarding information from one location ofcommunication network101 to another location. Forwardingdevices117,119 configured to use ATM switching may establish virtual circuits among each other through which information may be directed. The virtual circuits may map a path through which data may travel, at least a portion of the way, from a source to a destination. A virtual circuit may be established for each destination coupled tocommunication network101.
• A plurality of end nodes, including the plurality ofservers103 and other devices, may be coupled tocommunication network101 through forwardingdevices117,119. One or more of the end nodes may be configured to communicate with the forwarding devices through a direct connection using the ATM data link protocol or some other data link protocol such as Ethernet. In some embodiments, a forwarding device may be configured to communicate with end nodes using non-ATM data link protocols and convert that communication to an ATM data link protocol for transmission throughcommunication network101.
• In some embodiments, forwardingdevices117,119 may be configured to support a well-known ATM local area network emulation (LANE) allowing devices to couple tocommunication network101 as if they were part of a single local area network (e.g., a network connected on the same data link) even if they are geographically distant and actually connected to different local networks. ATM LANE may allow high speed forwarding techniques based on data link layer addresses to quickly direct data from one location ofcommunication network101 to another location of the communication network even where the locations are geographically distant from each other or separated from each other by an external communication network (e.g., the Internet). ATM LANE may also allow a forwarding of information over long distances by data link layer techniques, quality of service selections that improve performance of high priority or streaming traffic, traffic and network management based virtual circuits, and high bandwidth capabilities.
• FIG. 1B illustrates acommunication network151 spanning a large geographical area through adifferent communication network153.Communication network151 includes two physicallyseparate network sections155,157 separated by adifferent communication network153. Eachnetwork section155,157 includes a plurality ofhost devices159,161 connected to aforwarding device163,165 through adata link167,169. The data links may arranged to use any data link communication protocol that may be the same or different from each other or the protocol used to communicate through thedifferent communication network153, such as ATM, Ethernet, or Wi-Fi.
• In standard network layer forwarding techniques,first network section155 andsecond network section157 generally act as separate local area networks requiring reauthentication, and additional forwarding steps to transmit data from one section to another. However, ifnetwork sections155,157 are configured to operate using data link layer forwarding techniques such as ATM LANE, the two network sections may communicate as if they were part of the same local area network, as described above.
• To configure a network such as the one illustrated inFIG. 1B to operate using ATM LANE,first forwarding device163 may listen tofirst data link167 for data being sent to devices coupled tosecond forwarding device165 throughsecond data link169. When such data is transmitted onfirst data link167,first forwarding device163 may transparently forward data tosecond forwarding device165 through an ATMvirtual circuit171 that traversesdifferent network153.Second forwarding device165 may then transmit the data over thesecond data link169 to the destination host device.
• Forwardingdevices163,165 may be configured to forward data based on the data link address of the destination, so eachhost device159 onfirst network section155 may transmit information to thehost devices161 ofsecond network section157 by identifying the data link address of the second host device as the destination address of the data. Because, according to one embodiment, forwarding may be performed using data link addresses and no change in network layer information occurs in a packet, devices can communicate with each other as if they were locally connected within a transparently bridged/switched network. Such a configuration can be used to combine network sections even when the network sections use different data link protocols by converting one protocol to another protocol transparently.
• In some implementations,first forwarding device163 andsecond forwarding device165 may be connected through athird forwarding device173 that may be part of adifferent communication network153. For example, using ATM LANE, avirtual circuit171 may be established throughthird forwarding device173 so thatthird forwarding device173 forwards information between first andsecond forwarding devices163,165 based on data link layer destination addresses. Thethird forwarding device173 may be part of a network of a large communication provider, such as a telephone or cable provider, enablingfirst forwarding device163 to communicate over a long distance tosecond forwarding device165 using existing communication channels (e.g., fibers, cables, switches, etc.) of the communication provider.
• It should be recognized that embodiments of the invention are not limited to any particular arrangement and any particular configuration of forwarding devices, mobile devices, end nodes, or other network elements.
• Referring back toFIG. 1A, in some embodiments,communication network101 may also be coupled to anexternal network125, such as the Internet. Devices coupled tocommunication network101 may then access devices ofexternal network125. At least oneedge forwarding device127 may be configured as an edge router (e.g., a router that connects a local communication network to an external network) tocouple communication network101 toexternal network125.Edge forwarding device127 may convert received data between a communication protocol used byexternal network125 and a communication protocol used by communication network101 (e.g., ATM, Ethernet, Wi-Fi, etc.), if the communication protocols differ. The edge forwarding device may also provide security features tocommunication network101 such as firewall protection.
• Data received byedge forwarding device127 and directed to a destination device coupled tocommunication network101 may be directed throughcommunication network101 to the destination device. Similarly,edge forwarding device127 may direct data transmitted from a source device coupled tocommunication network101 toexternal network125.
• In accordance with another aspect of the present invention, a plurality ofstationary access points131,133, and149 may be coupled tocommunication network101. A stationary access point may include a wired or wireless router, an antenna-based tower structure as described below, and/or any other device configured to provide access tocommunication network101. In some embodiments, at least one firststationary access point131 may be coupled directly tocommunication network101 through awired connection139 to aforwarding device117 coupled tocommunication network101. The wired connection may include any type of mechanical connection such as fiber, cable, etc. Such a directly coupled firststationary access point131 may be configured to act as a forwarding device ofcommunication network101 to couple other devices, including other stationary access points, tocommunication network101. This configuration allowscommunication network101 to be accessed wherever a stationary access point is located.
• Various embodiments of the present invention may include at least one secondstationary access point133 that does not have a direct wired connection tocommunication network101. Such secondstationary access point133 may couple tocommunication network101 through the at least one firststationary access point131 that does have a wiredconnection139 tocommunication network101. This configuration allows multiple stationary access points to couple tocommunication network101 without requiring installation of direct wired connections tocommunication network101 at each stationary access point. This coupling may be facilitated through wired or wireless connections between stationary access points.
• Each such secondstationary access point133 that is coupled tocommunication network101 through such a firststationary access point131 may also then act as a forwarding device ofcommunication network101 to couple other devices, including other stationary access points, tocommunication network101.
• A network backbone (not designated) may be comprised bystationary access points131,133,149 and anyother forwarding devices117,119,123,127 andconnections139 used to forward data among thestationary access points131,133,149, theservers103, and theexternal network125. In some embodiments of the present invention, each device of the network backbone, includingstationary access points131,133, may be configured to use the ATM data link protocol and to forward data using ATM, as described above. In some implementations, the network backbone may include a distributed network backbone (i.e., one having a plurality of main forwarding devices directing data among the stationary access points, servers, and other devices coupled to communication network101). In other implementations, the network backbone may include a collapsed backbone (i.e., one having a singlemain router117 configured to direct data among the stationary access points, servers, and other devices coupled to communication network101). Use of a collapsed backbone may simplify forwarding decisions by concentrating the decisions into a central main router. By contrast, use of a distributed backbone may provide a more reliable network that can accommodate one or more router failures without a complete network failure.
• In accordance with another aspect of the present invention, eachstationary access point131,133 may be configured to couple at least onemobile device137 tocommunication network101.
• Mobile device137 may include a mobile access point, another type of mobile forwarding device, or a mobile host device such as a laptop, PDA, or cell phone. In some embodiments, coupling tocommunication network101 may be performed through a wireless connection between at least onestationary access point131,133 andmobile device137. The stationary access points may allow access tocommunication network101 for mobile devices (e.g.,137) that are within communication range.
• In some embodiments, before fully couplingmobile device137 tocommunication network101,stationary access points131,133 may be configured to authenticatemobile device137 withauthentication server105. After authenticatingmobile device137, thestationary access points131,133 may be configured to couplemobile device137 to communication network101 (e.g., allow communication betweenmobile device137 andcommunication network101, which may include communication to external network125).
• To facilitate communication betweenmobile device137 andcommunication network101,stationary access points131,133 may act as forwarding devices configured to forward data directed to and/or frommobile device137. Whenever a route tomobile device137 changes (e.g., whenmobile device137 couples tocommunication network101 through a newstationary access point131,133), the new stationary access point (e.g.,131,133) may be configured to update the forwarding information ofother forwarding devices119,117 and15 otherstationary access points131,133 coupled tocommunication network101 and anyexternal forwarding devices123 through whichforwarding devices117,119 ofcommunication network101 communicate, by, for example, generating and transmitting or forwarding a topology change notification (TCN) to the devices, so that data may be properly directed tomobile device137. TCNs are well known in the art of network communication.
• FIG. 2 illustrates an exemplarystationary access point201 in accordance with another aspect of the present invention that may be used as one of thestationary access points131,133,149 illustrated inFIG. 1A. In some embodiments, a stationary access point similar to that shown inFIG. 2 may be used as a primary access point to which a plurality of secondary access points may couple to thecommunication network101, as described in more detail below. The exemplarystationary access point201 comprises asupport structure207 to which a first communication system and a second communication system are mounted. In one embodiment, the first communication system includes afirst antenna system203, and the second communication system includes asecond antenna system205. Each antenna system may include one or more antennas and one or more radio devices. In other embodiments of a stationary access point, the first and second communication systems may include any other type of communication systems including wired or wireless communication systems configured to provide full or half duplex communication, such as optical communication systems or audio communication systems. The communication systems may be used by the stationary access point to communicate with other stationary access points and to provide access tocommunication network101 to mobile devices.
• Thesupport structure207 may include any type of support structure capable of adequately supporting the communication systems and may be made from any type of material including timber, fiberglass, metal, and concrete, or combinations thereof. Thesupport structure207 may be used to support other items such as advertisements (e.g., billboards), utility equipment (e.g., telephone poles), or structural elements (e.g., a bridge).Support structure207 may be coupled to afooting209 configured to upholdsupport structure207 and any devices mounted to supportstructure207 with the type and site of the footing being appropriate to the climate, environment, safety guidelines, etc. of the location in which it is used.
• In one embodiment,stationary access point201 also may include awired connection211 tocommunication network101.Wired connection211 tocommunication network101 may be used to transmit data betweenstationary access point201 andcommunication network101.Wired connection211 may include a TI connection, an optical fiber, or any other wired connection configured to provide the desired bandwidth betweencommunication network101 andstationary access point201 and couple to the at least onemobile device137. Other embodiments of a stationary access point may alternatively include a wireless connection tocommunication network101 or connect tocommunication network101 through one of the other communication systems (e.g.,203). In yet a further embodiment, a stationary access point may include both awired connection211 and a wireless connection tocommunication network101. In such an embodiment, the wireless connection could be used as a back-haul network connection tocommunication network101, or for redundancy in the event that communication via the wired connection is disrupted. Whatever connection method is used, a connection tocommunication network101 may allowstationary access point201 and any devices communicating with the stationary access point to couple tocommunication network101 with data transfer rates sufficient to satisfy the desires of a user of themobile device137. Typical sufficient data transfer rates tomobile device137 may range from approximately a few kilobytes per second to approximately many megabytes per second depending on the needs of the mobile device user.
• In one embodiment,first antenna system203 comprises twoantennas213,215 configured to wirelessly communicate with one or more directly or indirectly neighboring stationary access points.First antenna system203 may be used to couple the one or more neighboring stationary access points tocommunication network101 through firststationary access point201. Such coupling can be accomplished by forwarding data directed tocommunication network101 throughwired connection211 and forwarding data directed to the one or more neighboring stationary access points to thefirst antenna system203. Afirst antenna213 offirst antenna system203 may include a parabolic antenna, such as a 2.4 or 5.8 GHz AIRONET solid dish antenna commercially available from the Cisco Corporation, San Jose, Calif., having a main lobe oriented in a first direction and primarily propagating radio frequency (RF) energy toward a first set of neighboring stationary access points.Second antenna215 offirst antenna system203 may include a parabolic antenna, such as a 2.4 or 5.8 GHz AIRONET solid dish antenna commercially available from the Cisco Corporation. San Jose, Calif., having a main lobe oriented in a second direction and propagating RF energy primarily in the second direction, different than the first direction, toward a second set of neighboring stationary access points. It should be appreciated that any antenna type including parabolic, omnidirectional, leaky coaxial cable, or any other antenna type capable of radiating RF energy may be used for any antenna system of the present invention.
• First exemplarystationary access point201 may selectively forward data to the first set of neighboring stationary access points or the second set of neighboring stationary access points by sending the data through therespective antenna213 or215. Eachantenna213 and215 offirst antenna system203 may be configured to communicate on the same or different radio frequencies using the same or different communication protocols. For example, the first antenna may be configured to communicate using channel5 of the 802.11g communication protocol (i.e., 2434 MHz) and the second antenna may be configured to communicate using channel10 of the 802.11g communication protocol (i.e., 2457 MHz). By using such different frequencies, interference, which may occur when neighboring antennas communicate on the same frequency, may be reduced.
• Second antenna system205 may comprise threeantennas217,219,221 configured to communicate with at least onemobile device137. Exemplarystationary access point201 may forward data destined to the at least onemobile device137 by transmitting the data throughsecond antenna system205. Afirst antenna217 ofsecond antenna system205 may include a first parabolic antenna, such as a 2.4 or 5.8 GHz AIRONET solid dish antenna commercially available from the Cisco Corporation, San Jose, Calif., propagating RF energy primarily in a first direction along apath129 along which at least onemobile device137 moves. Asecond antenna219 ofsecond antenna system205 may also include a second parabolic antenna, such as a 2.4 or 5.8 GHz AIRONET solid dish antenna commercially available from the Cisco Corporation, San Jose, Calif., propagating RF energy primarily in a second direction alongpath129 along which at least onemobile device137 moves. Although the first and second directions will generally be substantially opposite to one another, it should be appreciated that they will depend upon the direction of the path along which the at least onemobile device137 moves.
• First antenna217 ofsecond antenna system205 may communicate with the at least onemobile device137 when the at least onemobile device137 is traveling in the second direction towardstationary access point201 or traveling in the first direction away from thestationary access point201 and is within a communication range offirst antenna217.Second antenna219 may communicate with the at least onemobile device137 when the at least onemobile device137 is traveling in the first direction towards thestationary access point201 or traveling in the second direction away fromstationary access point201 and is within a communication range ofsecond antenna219.
• In the illustrated embodiment, each of the first andsecond antennas217,219 ofsecond antenna system205 propagate RF energy primarily away from the first exemplary stationary access point and are disposed at a height greater than a height ofmobile device137. This configuration may leave an area near the support structure with a low level of signal from either the first of second antenna systems. The communication range of each of first andsecond antennas217,219 may cover an area from a minimum distance from exemplarystationary access point201 to a maximum distance from exemplarystationary access point201 so that the data transfer rate between the antenna system and themobile device137 is at least a minimum level within the communication range, such as between approximately a few kilobytes per second and approximately many megabytes per second depending on the needs of the mobile device user.
• Athird antenna221 ofsecond antenna system205 may include an omnidirectional antenna, such as an AIRONET omnidirectional mast antenna available commercially from the Cisco Corporation, San Jose, Calif., configured to communicate withmobile device137 whenmobile device137 is within the communication range ofthird antenna221. The communication range ofthird antenna221 may cover the area that is between the minimum distances covered by first andsecond antennas217,219 ofsecond antenna system205. This configuration of antennas insecond antenna system205 may allowmobile device137 to maintain communication withsecond antenna system205 throughout the region between the exemplary stationary access point and the minimum distance of each of the first andsecond antennas217,219 ofsecond antenna system205. Thus, the communication range of thesecond antenna system205 may cover the region extending between the maximum distance ofantenna217 andantenna219, with no gap in coverage proximate to thestationary access point201 itself. It should be appreciated that in other embodiments, thethird antenna221 may be other than an omnidirectional antenna. For example, to avoid propagating RF energy in all directions (and in particular, in directions other than toward thepath129 along which the at least onemobile device137 moves), it may be desirable to use a more directional type of antenna that is capable of propagating RF energy toward thepath129, and having a beam pattern that encompasses the region between the minimum distances ofantenna217 and219. A stationary access point configured in accordance with these embodiments of the present invention and in accordance with previously discussed aspects of the present invention may provide sufficient data transfer rates between themobile device137 and a communication network whenever the mobile device is within a communication range of one of a plurality of stationary access points that may be arranged across a large geographical area.
• To facilitate communication amongantenna systems203,205 andcommunication network101, each antenna system may be connected together by awired bus235 that also connects towired connection211. When data is received by one antenna system, it may be transmitted to another antenna system or towired connection211 through wiredbus235. Similarly when data is received throughwired connection211, it may be forwarded to one or more of the antenna systems through wiredbus235.
• First antenna system203 may include first andsecond forwarding element223,225. Each of the forwardingelements223,225 may maintain forwarding information for a plurality of devices coupled tocommunication network101, includingmobile device137 and any neighboring stationary access points. When data is received byfirst antenna213 of first antenna system203 (e.g., from the first set of neighboring stationary access points),first forwarding element223 may forward the data to eithersecond antenna215 offirst antenna system203 to be transmitted to the second set of neighboring stationary access points, tosecond antenna system205 to be transmitted to the at least onemobile device137, or towired connection211 to be transmitted tocommunication network101. Similarly, when data is received bysecond antenna215 of first antenna system203 (e.g., from the second set of neighboring stationary access points),second forwarding element225 may forward the data to eitherfirst antenna213 offirst communication system203 to be transmitted to the first set of neighboring stationary access points, tosecond antenna system205 to be transmitted to the at least onemobile device137, or towired connection211 to be transmitted tocommunication network101. Decisions of where to forward the data may be made based on forwarding information maintained by forwardingelements223,225. Such forwarding information may include, for example, a well-known forwarding table. After making the forwarding decision, the data may then be transmitted through wiredbus235.
• In one embodiment,second antenna system205 may include athird forwarding element227. Similar to first andsecond forwarding elements223,225 offirst antenna system203,third forwarding element227 ofsecond antenna system205 maintains forwarding information for a plurality of devices coupled tocommunication network101. When data is received bysecond antenna system205,third forwarding element227 forwards the data tofirst antenna system203 for transmission to a neighboring stationary access point or todirect connection211 for transmission tocommunication network101. Decisions of where to forward data may be made based on forwarding information maintained bythird forwarding element227.
• In some embodiments, the forwarding elements of theantenna systems203,205 may include the radio devices coupled to the antenna systems. For example, a radio device coupled tofirst antenna system203 of the first communication system may provide input tofirst antenna213 and forwarding functionality for incoming and outgoing information, as described above. In some implementations, an AIRONET wireless access point available commercially from the Cisco Corporation, San Jose, Calif., may be used as a radio device with such forwarding capabilities for the antenna systems.
• Afourth forwarding element229 may be coupled towired connection211. Similar to forwardingelements223,225,227 of first andsecond antenna systems203,205,fourth forwarding element229 may maintain forwarding information for a plurality of devices coupled tocommunication network101. When data is received throughwired connection211,fourth forwarding element229 forwards the data tofirst antenna system203 for transmission to a neighboring stationary access point or tosecond antenna system205 for transmission tomobile device137. Decisions of where to forward data may be made based on forwarding information maintained by the fourth forwarding element.
• In an alternative embodiment of a stationary access point, each communication system and the wired connection may be treated as a single communication system having only a single forwarding element. Any information received through any antenna may be transmitted to the single forwarding element. The single forwarding element may then determine where the received information should be directed based on maintained forwarding information. For example, the single forwarding element may forward the data to the first or second antenna offirst antenna system203 for transmission to a neighboring stationary access point, tosecond antenna system205 for transmission tomobile device137, or towired connection211 for transmission tocommunication network101.
• In accordance with one embodiment of the present invention, asolar power source231 andbattery233 may be coupled to supportstructure207 of the first exemplary stationary access point. Thesolar power source231 may be configured to supply power to the stationary access point as needed by the devices coupled to thestationary access point201, including first andsecond antenna system203,205. Thebattery233 may be configured to store excess power generated bysolar power source231 to supply power tostationary access point201 when thesolar power source231 is unable to supply sufficient power (e.g., at night or during inclement weather). Using asolar power source231 allows disposing of stationary access points in locations where power lines are not readily available or may require great cost to install. In other embodiments, a wired connection to an external power supply may power a stationary access point. In still other embodiments, multiple power sources (e.g., solar, battery, wired, and wind) may be used.
• FIG. 3 illustrates another embodiment of astationary access point301 having wiredconnections303,305 to each of its neighboring stationary access points that may be used as one or more of the stationary access points disposed along or adjacent to the path ofFIG. 1A. A first communication system is afirst antenna system307 of the second exemplarystationary access point301.First antenna system307 may be used to communicate with the at least onemobile device137 and may be substantially similar tosecond antenna system205 of previously describedstationary access point201. In other embodiments, the first communication system may include any other type of communication device including a wired or wireless communication device configured to provide full or half duplex communication. For example, the first communication system may include an optical or audio based communication device.
• Unlike the previously describedstationary access point201, thestationary access point301 ofFIG. 3 does not include an antenna system configured to communicate with neighboring stationary access points. Rather, this embodiment of astationary access point301 may communicate with neighboring stationary access points bywired connection303,305 to the neighboring stationary access points. Suchwired connections303,305 may increase the bandwidth of communication between neighboring stationary access points compared to neighboring stationary access points communicating using wireless connections. This increase in bandwidth may allow larger amounts of data to be transferred more quickly among the stationary access points and to mobile devices coupled tocommunication network101 through such stationary access points. As described above, wired communication may be by any means including a mechanical connection, such as a fiber, wire, coaxial cable, etc.
• In one embodiment, second exemplarystationary access point301 may not include a wired connection directly tocommunication network101. Instead, second exemplarystationary access point301 may be coupled tocommunication network101 through one of the neighboring stationary access points. Such a stationary access point that couples to thecommunication network101 through a neighboring stationary access point may be referred to as a secondary stationary access point, and the access point through which the secondary stationary access point couples may be referred to as a primary stationary access point. Such a configuration reduces the number of direct connects to the communication network that are needed to expand the area covered by the plurality of stationary access points. New stationary access points can be added by simply connecting them to the existing stationary access points either by wired connections as in the embodiment ofFIG. 3 or by wireless connections such as the ones described with respect to the first communication system ofFIG. 2.
• FIG. 4 illustrates yet another example of an arrangement of an exemplarystationary access point401. As illustrated, in some embodiments, stationary access points may be positioned near anobstruction403 that may obscure wireless transmission in one or more directions. Such anobstruction403 may include, for example, a bridge, tunnel, or other geographic structure. As illustrated inFIG. 4, a stationary access point may be arranged to provide access tocommunication network101 despite such an obstruction.
• As illustrated, some embodiments of a stationary access point may include multiple supports405 (e.g., two as shown inFIG. 4). One ormore antenna systems407 may be attached to each of the multiple supports405. Thesupports405 may be positioned on opposing sides of the one ormore obstructions403 and theantenna systems407 may be arranged to face substantially away from theobstruction403 to provide network access to mobile devices on respective sides of theobstruction403. Between thesupports405, anintermediate antenna system409 may be positioned to provide network access to mobile device there between. For example, in some implementations, theintermediate antenna system409 may include a length of leaky coaxial cable disposed between the poles. The leaky coaxial cable may be connected to communication systems of one or more of the respective poles to provide a communication signal to mobile devices that are within range between the poles, such as traveling over a bridge, through a tunnel, or otherwise near the obstruction. In some implementations, leaky coaxial cable may include a coaxial cable with a relatively low attenuation per foot (e.g., Radiax cable from the Andrew Corporation of Westchester, Ill.).
• It should be recognized that the previously described example stationary access points are given as non-limiting examples only. In other embodiments any type or arrangement of stationary access point may be used. Such access points are not limited to any number or type of antennas or antennas systems.
• According to various aspects of the present invention, the plurality ofstationary access points131,133 may be disposed along or adjacent topath129 traveled by avehicle501 as shown inFIG. 5 andFIG. 1A. In accordance with aspects of the present invention,vehicle501 may include any vehicle capable of transporting the at least onemobile device137 from one location to another. In various embodiments,vehicle501 may be configured to transport a plurality of mobile devices (e.g.,137,507,509,511,513) and mobile device users along the path so that the plurality of mobile devices move relative to thestationary access points131,133. In the illustrated embodiment ofFIG. 5,vehicle501 includes a train that moves along fixed train tracks (i.e., the path129). In other embodiments, a vehicle (e.g.,501) may include a boat traveling along a path (e.g.,129) of a water way (e.g., a shipping lane, ferry rout, etc.) or a bus or subway traveling along the path (e.g.,129) from one location to another. The mobile devices may include various computing devices such as cell phones, personal digital assistants, laptop computers, etc. that are used by passengers traveling aboard the vehicle, such as daily commuters on their way to and from work. Thepath129 may include a fixed path or a nearly fixed path, such as a roadway, a track, a ferry route, or a shipping lane. The path may span a long distance of many kilometers.
• In accordance with some embodiments, thepath129 may include a tunnel portion in which a supportingstructure207 is unavailable and/or difficult or costly to install. In such environments, a communication device capable of communicating with the mobile device may be attached to a portion of the tunnel wall or any other nearby existing structure (e.g., canyon wall). Such a communication device may include one or more parabolic antennas as described in the second antenna system of the first exemplary stationary access point above. A plurality of such communication devices may be wired together along the length of the tunnel portion or may communicate wirelessly through a second set of communication devices, such as the previously described first antenna system of the exemplary stationary access point illustrated inFIG. 2.
• Alternatively, other embodiments may use at least one leaky coaxial cable in the tunnel portion as an antenna to couple themobile device137 tocommunication network101 when themobile device137 is in the tunnel portion. For example, the leaky coaxial cable may be coupled to a tunnel forwarding device that is coupled tocommunication network101. The tunnel forwarding device may broadcast data along and receive data from the leaky coaxial cable. The tunnel forwarding device may authenticatemobile device137 withauthentication server105 whenmobile device137 first attempts to communicate withcommunication network101 and act as a root device (i.e. a forwarding device that maintains, at least for a certain duration of time, authentication information ofmobile device137, as will be described in more detail below) tomobile device137. The leaky coaxial cable may be arranged along or adjacent to a length of the tunnel section (e.g., attached to a tunnel wall or ceiling along the length of the tunnel). If necessary, multiple leaky coaxial segments may be used (e.g., in an extended tunnel such as the tunnel under the English Channel, etc.). Data then may be transmitted tomobile device137 as energy radiating from the leaky coaxial cable along the length of the tunnel section after transmission from the tunnel forwarding device. Likewise, energy radiated bymobile device137 may be received by the leaky coaxial cable and transmitted to the tunnel forwarding device. The leaky coaxial cable may be any coaxial cable having one or more portions of shielding removed along the length of the coaxial cable, such as a cable with a plurality of unshielded apertures, a cable with an unshielded slit, etc.
• FIGS. 6A and 6B illustrate example leaky coaxial cable hangers that may be used in various embodiments to connect coaxial cable to a desired surface. The leaky coaxial cable hanger ofFIG. 6A may be attached directly to a wall, ceiling, flooring, or other surface as desired. Similarly, the leaky coaxial cable hanger ofFIG. 6B may also be hung from any surface as desired. The hanger ofFIG. 6A may be used in situations where less clearance is available for a hanger, such as in a small tunnel. The cable may be disposed throughcable hole601 in either of the illustrated hangers.
• Returning to refer toFIG. 5, various embodiments of the present invention may include multiple vehicles or a vehicle comprising a plurality ofvehicle portions503,505. Each vehicle or vehicle portion may be configured to transport a plurality of mobile devices (e.g.,137,507,509,511, and513) and users of mobile devices alongpath129. For example, the train ofFIG. 5 comprises a plurality of cars including acafe car503 and apassenger car505. Various other embodiments may include a caravan of busses, cars, boats, or other vehicles.
• In one aspect of the present invention, eachstationary access point131,133 may be configured to allow wireless communication with the at least onemobile device137 whenmobile device137 is in a communication range of the stationary access point. The stationary access points (e.g.,131,133) may be arranged along thepath129 such thatmobile device137 is in the communication range of at least onestationary access point131,133 at all times as it travels from one end ofpath129 to another end ofpath129. Such a configuration allows a mobile device to travel the path and maintain communication with at least one stationary access point andcommunication network101.
• In some embodiments, the stationary access points may be configured in a primary-secondary configuration. For example, a primary pole, such as one illustrated inFIG. 2, may feed communication signals to a plurality of secondary poles. The primary and secondary poles in a respective group may be grouped together, for example, using a wired connection. The primary poles, however, may be connected through wireless communication. Other arrangements may be used.
• For security purposes, firststationary access point131 to whichmobile device137 attempts to connect may be configured to allow access tocommunication network101 only aftermobile device137 has been authenticated.Mobile device137 may request authentication when it enters a communication range of firststationary access point131. Firststationary access point131 may authenticatemobile device137 throughauthentication server105 by transmitting an authentication request toauthentication server105 throughcommunication network101. Whenmobile device137 moves from the communication range of firststationary access point131 to the communication range of secondstationary access point133,mobile device137 may request authentication with secondstationary access point133. Similar to the first stationary access point, the secondstationary access point133 may communicate withauthentication server105 to authenticatemobile device137 before allowingmobile device137 access tocommunication network101. By requiring authentication, thestationary access points131,133 prevent unwanted or untrusted devices from coupling tocommunication network101.
• Some embodiments of the present invention may not require authentication at all. For instance, some implementations may use wired equivalent privacy (WEP) encryption to prevent unwanted or untrusted devices from accessingcommunication network101. In one such example, a WEP key may be shared with each trusted mobile device, and only the devices knowing the WEP key may then be allowed to couple to thecommunication network101. It should be appreciated that various embodiments of the invention may use authentication or not, either alone or in connection with other methods, and the invention should not be limited to any particular type of authentication or combination of methods.
• Once amobile device137 is authenticated to the secondstationary access point133, the second stationary access point may record the authentication information in an association table. The secondstationary access point133 may remove the recorded information after a set timeout period. While the information is in the association table,mobile device137 may be allowed to couple tocommunication network101 through the secondstationary access point133 without requiring reauthorization. In some embodiments, the association table may record authentication information ofmobile device137 based on a physical address of a communication device of mobile device137 (i.e., the MAC address of a wireless adapter of themobile device137 may be recorded in an association table to indicate that themobile device137 is authenticated).
• A stationary access point that records the authentication information of an authenticatedmobile device137, for at least a minimum time period, may, in the art, be called a root device. Conversely, a mobile device that was authenticated but does not record any authentication information and acts as a client of the root device may be called a non-root device. As described above, since stationary access points may have multiple communication devices, the root/non-root distinction may be applied at the communication device level. For example, themobile device137 may be only authorized to couple to thecommunication network101 through a first communication device of a plurality of communication devices comprising a stationary access point (e.g., thesecond antenna system205 of the first exemplary stationary access point201). In that case, the first communication device may be a root device for themobile device137. In some cases, as discussed below, the mobile device may comprise a plurality of communication devices including a non-root communication device to communicate with the root communication device of the stationary access point and root communication devices to communicate with non-root communication devices of other mobile devices.
• Because root devices record the authentication information of other devices, the other devices may not need to be reauthenticated when they attempt to communicate with the root device after a first authentication. In some instances, the root devices may be configured to record the authentication information only for some predetermined period of time or timeout period when communication with the other devices is expected. In some implementations, the predetermined period of time may be a number of days such that a user of a mobile device that travels the path regularly needs to be reauthenticated only after an extended break in use, such as a vacation.
• In some embodiments, authentication may delaymobile device137 from coupling tocommunication network101 becausemobile device137 may be denied access tocommunication network101 untilmobile device137 is authenticated. If the firststationary access point131 and the secondstationary access point133 are arranged such that their respective communication ranges do not overlap,mobile device137 may be left without access tocommunication network101 when it moves from the communication range of firststationary access point131 to the communication range of secondstationary access point133 while secondstationary access point133 waits for authentication ofmobile device137.
• In various embodiments of the present invention, the plurality of stationary access points may be arranged such that each stationary access point's communication range overlaps with the communication range of at least one other stationary access point so that themobile device137 does not experience access interruption as it moves between the first and secondstationary access points131,133 of the plurality of stationary access points because of the authentication process. The overlap of communication ranges may be large enough so that authentication of themobile device137 by the secondstationary access point133 may be completed before themobile device137 moves out of the communication range of the firststationary access point131. The overlap in communication range may vary based on the speed at which the mobile device is traveling and the time needed for performing the authentication process.
• Asvehicle501 travels alongpath129, line of sight may be maintained betweenmobile device137 and a communication system of stationary access points (e.g.,131,133) communicating withmobile device137 to improve communication range. If the communication system includes an antenna system, obstruction of line of sight may diminish the reliability of services and the communication range of thestationary access points131,133. If the communication system includes an optical system, the obstruction of line of sight may completely end communication betweenmobile device137 andstationary access points131,133. To maintain line of sight, the communication system of the stationary access point that is communicating with the mobile device137 (e.g., the second antenna system of the first stationary access point) may be disposed at a sufficient height so thatvehicle501 does not obstruct the line of sight between the communication system andmobile device137. In some implementations, the sufficient height may be at least as great as the tallest portion of the vehicle. In some implementations where the communication system includes an antenna system, the antenna system may be arranged such that less than approximately 40% of the radiation pattern of the antenna system is blocked byvehicle501 as it travels alongpath129.
• To maintain line of sight as thevehicle501 travels along acurve141 ofpath129, more stationary access points may be needed than to maintain line of sight along astraight portion147 ofpath129. This may be particularly true if the stationary access points are disposed along an inner portion ofcurve141 so that they are passed quickly byvehicle501 as it travels alongcurve141. In one embodiment, to improve the line of sight of each stationary access point disposed along a curve (e.g.,141) inpath129, stationary access points may be disposed along or adjacent to the outer portion ofcurve141. Disposing stationary access points along or adjacent the outer portion of thecurve141 may ensure that as thevehicle501 traverses thecurve141, it is within communication range of at least one other stationary access point.
• Furthermore, ifvehicle501 is moving quickly alongcurve141,mobile device137 may quickly move from the communication range of the firststationary access point131 to the communication range of the secondstationary access point133. The time needed to authenticatemobile device137 may be longer than the time in which the mobile device is within the overlapping communication ranges of the first and second stationary access points thereby potentially causing a break in network access.
• To facilitate faster authentication times, according to one embodiment, the first and secondstationary access points131,133 and any other stationary access points alongcurve141 may be combined into one or more stationaryaccess point groups143, as shown inFIG. 1A. The stationaryaccess point group143 may be coupled to a stationary accesspoint group controller145. According to one embodiment,group controller145 may be configured to provide a local authentication cache that stores authentication information requested and received by any stationary access point in stationaryaccess point group143. The local authentication cache may remove this information after a timeout period has passed, which may depend, for example, on the amount of memory in the cache. Authentication by one of the stationary access points of stationaryaccess point group143 then may only involveauthentication server105 if the authentication cache does not contain the requested authentication information. Once authenticated, as thevehicle501 moves within the communication range of other stationary access points that are members of thegroup143, themobile device137 may be authenticated by reference to the cached information, thereby eliminating the need to authenticate with theserver105. In accordance with one embodiment, the amount of memory of the cache may be sufficient to permit the information to remain for several days, such that a commuter that uses the same transportation need not be re-authenticated unless he or she is away for an extended period of time (e.g., a vacation).
• In one embodiment,group controller145 may include a wireless LAN context communication protocol (WLCCP) controller coupled to each of the stationary access points in the stationaryaccess point group143. In some implementations, the WLCCP controller may include a AIRONET access point, available commercially from the Cisco Corporation, San Jose, Calif., coupled to the stationary access points of the group. Thegroup controller145 may facilitate low latency authentication of themobile device137. Authentication may be provided to the stationary access points of the stationaryaccess point group143 in less than approximately two milliseconds if the requested authentication information is cached.
• It should be appreciated that stationary access points may fail over time, leaving gaps of coverage along thepath129, which may also cause breaks in network access for the mobile device. To help prevent such gaps in coverage, in some embodiments of the present invention, the plurality of stationary access points may be arranged alongpath129 so that coverage alongpath129 is redundant. For example, firststationary access point131, secondstationary access point133, and a thirdstationary access point149 may be arranged so that the first and thirdstationary access131,149 points have a combined communication range that covers the communication range of the secondstationary access point133 and a sufficient overlap so that authentication by the thirdstationary access point149 may complete beforemobile device137 leaves the communication range of the firststationary access point131.
• In such an arrangement, the secondstationary access point133 may fail without leaving a gap in coverage between the first and thirdstationary access points131,149. Therefore, even if the secondstationary access point133 is the closest stationary access point tomobile device137, there may be no interruption in access tocommunication network101 asmobile device137 moves from the communication range of firststationary access point131 to the communication range of thirdstationary access point149, even if secondarystationary access point133 is not operating or if communication between themobile device137 and the secondarystationary access point133 is otherwise disrupted.
• In one embodiment,mobile device137 may be configured to change the stationary access point through whichmobile device137 couples tocommunication network101 asvehicle501 travelspath129. Whenmobile device137 is in communication range of a plurality of stationary access points,mobile device137 may be configured to couple tocommunication network101 through the stationary access point providing the strongest or one of the stronger communication signal strengths at a current location of the ofmobile device137. The signal strength may be measured by the well-known received signal strength indicator (RSSI).
• To facilitate a quick transition of the mobile device from coupling tocommunication network101 through firststationary access point131 to coupling through secondstationary access point133,mobile device137 may be configured to authenticate with the secondstationary access point133 whilemobile device137 is still coupled tocommunication network101 through the firststationary access point131 and prior tomobile device137 being configured to couple tocommunication network101 through secondstationary access point133. For example,mobile device137 may be configured to authenticate with secondstationary access point133 when the signal strength of secondstationary access point133 is still less than the signal strength of firststationary access point131.
• In some implementations,mobile device137 may be configured to authenticate with secondstationary access point133 relatively soon aftermobile device137 enters the communication range of secondstationary access point133. Specifically, themobile device137 may authenticate with the secondstationary access point133 when the signal strength of the secondstationary access point133 is approximately half the signal strength of the firststationary access point131.
• In one implementation,mobile device137 may be configured to authenticate with secondarystationary access point133 by wireless communication to secondarystationary access point133. For example,mobile device137 may transmit an authentication request to secondarystationary access point133 using a wireless communication system, as described below. In one implementation,mobile device137 may be configured to authenticate with secondarystationary access point133 through wireless communication with firststationary access point131. For example,mobile device137 may transmit an authentication request for secondstationary access point133 to firststationary access point131 using a wireless communication system, as described below. Firststationary access point131 may receive the authentication request and forward the request to second stationary access point133 (e.g., through the backbone). Secondstationary access point133 may authenticatemobile device137, as described above, and transmit an authentication response tomobile device137 though firststationary access point131.
• In one embodiment, firststationary access point131 may communicate an authentication request for secondstationary access point133 to secondstationary access point133 using a data link layer address of secondstationary access point133. In one embodiment, such communication may occur when firststationary access point131 and secondstationary access point133 may be geographically distant or separated by one or more external communication networks or other network layer barriers (e.g., router). For example, the first and second stationary access point may communicate using ATM LANE such that they may communicate with one another using data link layer addresses even over network barriers and large distances, as described above.
• While the authentication occurs and after the authentication finishes, themobile device137 may be configured to continue coupling to thecommunication network101 through the firststationary access point131.Mobile device137 may be configured to stop coupling to thecommunication network101 through the firststationary access point131 and begin coupling to thecommunication network101 through the secondstationary access point133 at one of the later of when the authentication completes, when the strength of the communication signal received bymobile device137 from the secondstationary access point133 exceeds the strength of the communication signal received by themobile device137 from the firststationary access point131, or both.
• In one aspect of the present invention, the at least onemobile device137 communicating with stationary access points may include a mobile access point (also referenced herein as137) configured to couple a plurality of othermobile devices507,509,511,513 to thecommunication network101 through the plurality of stationary access points. Themobile access point137 may provide access tocommunication network101 to each of the plurality ofmobile devices507,509,511,513 asmobile access point137 travels along the path near or adjacent tostationary access points131 and133, for example while on a vehicle (e.g.,501).
• In some embodiments, the stationary access points may be configured to authenticate themobile access point137 before allowing it to couple the othermobile devices507,509,511,513 to the communication network. The authentication may be performed through communication with theauthentication server105 or group controllers as described above. In some implementations, the authentication may be based on a physical address (e.g., MAC address) of a communication system of themobile access point137. Such authentication based on physical addresses allows the mobile access point to authenticate without a user or administrator entering a password or other login information.
• Themobile access point137 may be configured to communicate with the plurality of stationary access points using any communication protocol. If the network backbone is configured to communicate using ATM,mobile access point137 may be configured to communicate with the plurality of stationary access points using A TM as well. Such a configuration may allow data to be forwarded through the plurality of stationary access points tomobile access point137 without conversion from one protocol to another or reference to the network layer destination address of the data.
• In one embodiment,mobile access point137 may be configured to couple a plurality ofmobile host devices507 traveling along with themobile access point137 tocommunication network101. The plurality ofhost devices507 may include laptop computers, mobile phones, PDAs, or any other computing device configured to communicate over a computer network, such as those used by passengers of a vehicle.
• In one embodiment,mobile access point137 may be configured to allow at least one host device of the plurality ofhost devices507 to couple to thecommunication network101 after themobile access point137 authenticates the one host device with theauthentication server105. When the one host device attempts to couple tocommunication network101 through themobile access point137, a user of the one host device may be required to provide login information such as a username and password to complete authentication. After authentication, themobile access point137 may couple the one host device tocommunication network101 through one of the stationary access points. In some embodiments of the present invention,mobile access point137 may act as a root device for the one host device (i.e., the mobile access point may record the authentication information of the one host device). In such embodiments, whenmobile access point137 moves to couple itself and the one host device to thecommunication network101 through a different stationary access point, onlymobile access point137 may be required to authenticate with the different stationary access point. Becausemobile access point137 records that one host device has already been authenticated, no reauthentication may be needed between the mobile access point and the plurality ofhost devices507. Such a configuration reduces the amount of authentication requests sent to theauthentication server105 each timemobile access point137 moves to couple to thecommunication network101 through a new stationary access point thereby allowing faster authentication ofmobile access point137.
• The plurality ofhost devices507 coupled to thecommunication network101 through themobile access point137 may request IP addresses from theDHCP server109 and access devices coupled to thecommunication network101 and resources of thecommunication network101.Mobile access point137 may be configured to transmit forwarding information tocommunication network101 for each of the plurality ofhost devices507 so that other devices coupled to thecommunication network101 may communicate with thehost devices507. The forwarding information may include the IP address of each of thehost devices507 and/or the physical addresses of each of thehost devices507.
• Each time themobile access point137 moves to couple thehost devices507 to thecommunication network101 through a different stationary access point, forwarding information may be transmitted through thecommunication network101 to update the forwarding information of the other devices, including the forwarding devices, stationary access points, and servers, coupled to thecommunication network101. When the other devices receive the updated forwarding information they may record the updated forwarding information to facilitate proper forwarding of data to thehost devices507 in the future. The forwarding information may include an identification of the port on which information destined for thehost devices507 should be transmitted in order to reach the host devices. The identification of the port may include receipt of the updated forwarding information on the port. When the other devices receive information destined for one of the host devices, they can reference this updated forwarding information and transmit data to the proper port. By so maintaining the forwarding information each time themobile access point137 moves, thehost devices507 may move along thepath129 without the need to obtain a new address to receive data destined for thehost devices507.
• Communication between themobile access point137 and thehost devices507 may occur using any communication protocol known to bothhost devices507 andmobile access point137. If the network backbone andmobile access point137 are configured to communicate using ATM, thehost devices507 may be configured to communicate with themobile access point137 using ATM as well. Such a configuration may allow data to be forwarded through thecommunication network101, the stationary access points, and themobile access point137 to thehost devices507 without conversion from one protocol to another or reference to a network layer destination address of the data.Many host devices507, however, may not be configured to use an ATM connection. Themobile access point137 may be configured to communicate with thesehost devices507 using any other communication protocol, such as Ethernet or Wi-Fi. Communication betweenmobile access point137 andhost devices507 may be wired, wireless or a combination of wired and wireless. It should be recognized that information may be transmitted from one device (e.g., forwarding device, mobile device, etc.) to another device using any number of formats and/or protocols. Accordingly, as used herein, the expression “a representation of at least a portion of data” received by a device should be understood to refer to the underlying data received by a device, regardless of the formatting or other protocol information associated with that data.
• In one embodiment, themobile access point137 may not directly communicate withhost devices507. Instead, arepeater517 may be connected to themobile access point137 and direct data between themobile access point137 and thehost devices507.Repeater517 may then repeat the received information either through wired or wireless communication methods tohost devices507.
• In some embodiments of the present invention, at least onemobile forwarding device509 may couple to thecommunication network101 through themobile access point137.Mobile forwarding device509 may include a router, switch, bridge, and/or repeaters configured to allow other mobile forwarding devices and/ormobile host devices511 to couple to thecommunication network101 through themobile access point137.Mobile forwarding device509 may be used to extend the range of themobile access point137.
• Mobile forwarding device509 may be configured to communicate withmobile access point137, other mobile forwarding devices, andmobile host devices511 using any communication protocol. If the network backbone and the mobile access point are configured to communicate using ATM,mobile forwarding device509 may be configured to use ATM as well. Such a configuration may allow data to be forwarded through the stationary access points to themobile access point137 and then tomobile forwarding device509 without conversion from one protocol to another or reference to a network layer destination address of the data to provide a higher speed forwarding of data to and frommobile forwarding device509.
• Before a mobile forwarding device (e.g.,509) couples to thecommunication network101 though themobile access point137, themobile access point137 may first authenticate the mobile forwarding device based on a physical address of themobile forwarding device509. Each mobile forwarding device (e.g.,509) may be configured to authenticate other mobile forwarding devices andmobile host devices511 before coupling the other mobile forwarding devices andmobile host device511 to thecommunication network101 throughmobile access point137.
• Mobile forwarding device509 may be configured to act as a root device for other mobile forwarding devices, such as those shown coupled to other cars of the train depicted inFIG. 7. Themobile forwarding device509 may also be configured to act as a root device to themobile host devices511 coupled tomobile access point137 through themobile forwarding device509. In such an implementation, themobile forwarding device509 may maintain authentication information for these other mobile forwarding devices andmobile host devices511 so that reauthentication of mobile forwarding devices and host devices may not be required as themobile access point137 moves to couple to thecommunication network101 through a new stationary access point.
• In one embodiment,mobile forwarding device509 may include a repeater coupled to thepassenger car505 ofvehicle501 that communicates wirelessly with themobile access point137 coupled to thecafe car503 ofvehicle501. Further,mobile forwarding device509 may include a repeater to communicate withmobile host devices511 within the passenger car. If the vehicle included other passenger cars, such ascars705 and707 ofFIG. 7, anothermobile forwarding device701,703 may be coupled to each car, as is shown inFIG. 7.Mobile forwarding devices701,703couple host devices709,711 to thecommunication network101.Mobile forwarding devices701,703 in passenger cars farther away from themobile access point137 may communicate with themobile access point137 through mobile forwarding devices (e.g.,509) closer to themobile access point137 or communicate directly with themobile access point137, as is illustrated inFIG. 7.
• Themobile access point137 may be configured with a plurality of communication systems similar to the communication systems of the stationary access point described above. The plurality of communication systems may include one or more wired communication systems. The plurality of communication systems may include one or more wireless communication systems configured to provide full or half duplex communication, such as optical or RF based communication systems. A first communication system may be configured to communicate with the plurality of stationary access points to couple themobile access point137 to thecommunication network101. A second communication system of themobile access point137 may be configured to communicate with one ormore host devices507,513 to couple thehost devices507,513 to thecommunication network101. A third communication system may be configured to communicate with one or more mobile forwarding devices (e.g.,509) to couple the mobile forwarding devices to thecommunication network101. One or more of the communication systems of themobile access point137 may be an antenna system or other wireless communication system. Themobile access point137 may include a forwarding system configured to forward data received by one communication system to another communication system to reach the destination of the data. The plurality of communication systems may be connected together with a wired connection. The forwarding of data may be performed based on maintained forwarding information.
• Such a configuration allows the mobile access point to communicate with the stationary access points through one dedicated communication device, the host devices through another, and the repeaters through a third. Each communication device may communicate using the same or a different communication protocol on the same or a different channel. If the devices each communicate using different frequencies, the entire bandwidth of each communication device may be available to communicate with the set of devices assigned to the communication device (e.g., the communication device used to communicate with the stationary access points may not reduce the bandwidth or interfere with the communication device used to communicate with the host devices).
• Themobile forwarding device509 may also include a plurality of communication systems. The plurality of communication systems may include one or more wired communication systems. A first communication system may be configured to communicate with themobile access point137. A second communication system may be configured to communicate with themobile host devices511. A third communication system may be configured to communicate with one or more other mobile forwarding devices. One or more of the communication systems of themobile forwarding device509 may be an antenna system or other wireless communication system configured to provide full or half duplex communication. The mobile forwarding device may include a forwarding system configured to forward data received by one communication device to another communication device to reach the destination of the data. The plurality of communication systems may be connected together with a wired connection. The forwarding of data may be performed based on maintained forwarding information.
• It should be recognized that the above described configuration of mobile access points and mobile forwarding devices is given as an example only and that any other desired configuration may be used in other embodiments. For example, in some embodiments, no mobile forwarding device may be used, but rather, mobile devices may couple to mobile access points directly. In still other embodiments, each portion of a vehicle (e.g., car of a train) may include a separate mobile access point rather than a mobile forwarding device. Such an arrangement may be beneficial, for example, if distance between portions of a vehicle are too large and/or line of sight between portions of a vehicle are otherwise obstructed and are not sufficient for wireless transmission from a mobile forwarding device in one portion of the vehicle to a mobile access point in another portion of the vehicle (e.g., such as when going through tunnels, around curves, etc.).
• In one aspect of the present invention, amonitoring server113 may be coupled to thecommunication network101. Themonitoring server113 may be configured to determine the geographic location of thevehicle501, themobile access point137, or amobile host device511 coupled to thecommunication network101 traveling along with thevehicle501. In one embodiment of the present invention, to facilitate this determination, a global positioning device may be coupled to themobile access point137. Themonitoring server113 may receive information from the global positioning device identifying the position of themobile access point137. Since the mobile access point and host devices move along with thevehicle501, the position of the mobile access point is indicative of the position of thevehicle501 and the host devices.
• In another embodiment of the present invention, the geographic position of each of the stationary access points may be known to the monitoring server113 (e.g., they may be determined at the time of installation and input to the monitoring server113). Themonitoring server113 may be configured to monitor which stationary access points are communicating with themobile access point137. In one implementation, each stationary access point may periodically transmit information to themonitoring server113 indicating whether the stationary access point is communicating with themobile access point137. In other implementations, each stationary access point may be configured to notify themonitoring server113 whenever themobile access point137 begins or stops communicating with the stationary access point. Themonitoring server113 may approximately determine the location of themobile access point137 based on the stationary access points with which themobile access point137 is communicating. For example, the monitoring server may approximate the location of themobile access point137 to be at the known location of the secondstationary access point133 when themobile access point137 is communicating with each of the first, second, and third mobile access points because the secondstationary access point133 is between the first and third stationary access points.
• In some implementations, each stationary access point may also transmit information indicating the strength of a communication signal received frommobile access point137 to themonitoring server113. Themonitoring server113 may use this communication signal strength to improve the approximation of the location ofmobile access point137. The monitoring system may use known relationships between distance from a stationary access point and the strength of the communication signal to make these improved approximations. For example, the monitoring server may approximate the location of themobile access point137 to be closer to a known location of the firststationary access point131 than to a known location of the secondstationary access point133 when themobile access point137 is communicating with the firststationary access point131 with a stronger signal strength than with which it is communicating to the secondstationary access point133.
• In some embodiments of the present invention, acontent server115 may deliver information to at least one host device (e.g.,507) coupled to the communication network based on the location of the mobile access point137,mobile host device511, orvehicle501 determined by themonitoring server113. The information may be directed to the mobile host device in the form of a web-based pop-up. The pop-up may, for example, indicate to a user of themobile host device511 that thevehicle501 is near a certain location (e.g., a train station). The pop-up may be an advertisement for a business, museum, other tourist attraction, or special event near a current location of themobile access point137 and themobile host device511. The information may also be in the form of an email.
• In some embodiments, thevehicle501 may travel among relatively fixed locations at which passengers may load/unload the vehicle. For example, a train may travel among train stations, and a bus may travel among bus stops. Network access may be facilitated at the fixed locations through one or more antenna systems disposed at or near the fixed locations. For example, in some embodiments, one or more omnidirectional antennas which are coupled tonetwork101 may be positioned at or near the fixed location to provide access tonetwork101 to mobile devices at or near the fixed location. In some embodiments, one or more lengths of leaky coaxial cable which are coupled tonetwork101 may be positioned at or near the fixed location to provide access tonetwork101 to mobile devices at or near the fixed location.
• One or more of the fixed locations may include a large area. In such situations, multiple antennas or lengths of leaky coaxial cable may be used to provide access tonetwork101. The multiple antennas or lengths of leaky coaxial may be positioned and arranged such that all or substantially all of the large area is provided with network access. In some embodiments, for example, in which the fixed location includes a large waiting room, as is typical in train stations, one or more lengths of leaky coaxial cable may be positioned on opposing sides of the large waiting room. The lengths of leaky coaxial cable may be configured to provide network access through different wireless channels (e.g., 5 channels of separation). By so positioning and arranging the lengths of leaky coaxial cable, line of sight issues and interference problems may be eliminated or minimized.
• In some embodiments, one or more antenna systems (e.g., such as those illustrated inFIG. 2,3, or4, leaky coaxial cable, etc.) may be part of or connect to an existing or future system. For example, in some embodiments, leaky coaxial cable that may, for example, be used within a fixed location and/or a tunnel to provide network access, may be part of an existing leaky coaxial system. The existing leaky coaxial system may, for example, include an emergency communication system or other existing communication system. The antennas may also connect to a system, such as a separate communication system, and thereby be shared among multiple systems. For example, in one embodiment, the leaky coaxial may connect to a cellular system configured to provide cellular service within tunnels or at the fixed location or elsewhere.
• Having described the structure of various components, operation of an exemplary embodiment of the present invention that is configured to use an ATM LANE is described below.
• Referring to the flow charts ofFIG. 8 andFIG. 9, which illustrate processes beginning atblocks801 and901 respectively, and the system shown inFIG. 5 andFIG. 7, themobile access point137 may begin the process being coupled to thecommunication network101 through the firststationary access point131. The mobile access point may couple themobile devices507,511,709,711 to thecommunication network101 through the firststationary access point131 as is indicated inblock903 of the flow chart inFIG. 9.
• Afirst host device513 in the passenger car ofFIG. 5, may attempt to communicate with themobile access point137 to authenticate and begin coupling to thecommunication network101. When thehost device513 attempts to communicate with themobile access point137, themobile access point137 may first authenticate thehost device513. The authentication process may require a user of thehost device513 to enter a login and password. The authentication process may also be based on a physical address of thehost device513. To authenticate thehost device513, themobile access point137 transmits a request to theauthentication server105 through an ATM connection with the firststationary access point131. The firststationary access point131 may inspect the physical layer destination of the authentication request and forward it on to theauthentication server105 through thecommunication network101. Theauthentication server105 may receive the request, perform a query on the authentication database and respond to the request by transmitting an authentication response to themobile access point137 though thecommunication network101, and firststationary access point131 as ATM cells. When themobile access point137 receives the authentication response, if it includes a positive response, themobile access point137 may couple thehost device513 to thecommunication network101 through the firststationary access point131.
• Themobile access point137, having communicated with thehost device513 through one of its communication systems, now knows how to communicate with thehost device513 in the future (i.e., through that same communication system). Themobile access point137 may store this information in an address table so that the host device's physical address is associated with the proper communication system. When data directed to thehost device513 is received by themobile access point137, themobile access point137 can determine which communication system to forward the data through by referencing the address table. Themobile access point137 may then transmit a topology change notification (TCN) to the firststationary access point131. The TCN indicates that the host device513 (identified by its physical address) can be accessed though themobile access point137. The firststationary access point131 may record this information in its address table indicating that it can communicate with thehost device513 through the communication system used to communicate with the mobile access point137 (e.g., an antenna system such as thesecond antenna system205 of the first exemplary stationary access point201). The firststationary access point131 may then transmit a TCN through thecommunication network101 so other devices connected to thecommunication network101 know how to communicate with thehost device513. Each device that receives the TCN may establish an ATM virtual circuit to the host device or themobile access point137 to be used to communicate with the host device.
• Themobile access point137 may reach a location when it is within the communication range of the secondstationary access point133 as illustrated byblock905. Relatively soon after entering the communication range of the secondstationary access point133, themobile access point137 may begin the process of transitioning to coupling to thecommunication network101 through the secondstationary access point133 by authenticating itself with the secondstationary access point133 as indicated inblock907 ofFIG. 9. The secondstationary access point133 may receive an authentication request from themobile access point137 as indicated inblock803 ofFIG. 8. The secondstationary access point133 may transmit an authentication request to theauthentication server105 and/or an authentication cache if the secondstationary access point133 is part of a stationary access point group in order to authenticate themobile access point137 as indicated inblock805 ofFIG. 8. The second stationary access point may take different actions depending on whether the authentication was successful, as indicated atblock807. If the secondstationary access point133 receives a rejection from the authentication request it may deny themobile access point137 access to the communication network as indicated inblock809 ofFIG. 8. The process may then end atblock811. If the secondstationary access point133 receives a positive authentication response from theauthentication server105 or authentication cache, the secondstationary access point133 may record the authentication information, as indicated inblock813FIG. 8, and await further communication from themobile access point137.
• As thevehicle501, and themobile access point137, move towards the secondstationary access point133 and away from the firststationary access point131, the communication signal from the secondstationary access point133 may get stronger and the communication signal from the firststationary access point131 may get weaker. Themobile access point137 may monitor the signal strength of the first and second stationary access points as indicated inblock909 ofFIG. 9.
• At some point between the first and secondstationary access points131,133, themobile access point137 may request to couple to thecommunication network101 through the secondstationary access point133 instead of through the firststationary access point131. As discussed above, themobile access point137 may send this request approximately when the strength of the communication signal from the secondstationary access point133 exceeds the strength of the communication signal from the firststationary access point131. The secondstationary access point133 may receive this request, as indicated inblock815 ofFIG. 8, and update its stored forwarding information and the forwarding information of other devices coupled to thecommunication network101 as indicated inblock817 ofFIG. 8, by, for example, establishing one or more new ATM virtual circuits.
• To update the forwarding information of other devices, the secondstationary access point133 may transmit a TCN through thecommunication network101. The TCN may indicate that themobile access point137 and any other devices coupled to thecommunication network101 through the mobile access point (including the host device513) are accessible through communication with the secondstationary access point133. Any devices connected to thecommunication network101 may receive the TCN and update their address tables to reflect this change. Any ATM devices may create new virtual circuits to the mobile device based on the updated forwarding information.
• After updating forwarding information, the second stationary access point may couple themobile access point137 to thecommunication network101, as indicated inblock819 ofFIG. 8, by transferring data between themobile access point137 and thecommunication network101. When the signal strength of the secondstationary access point133 exceeds some desired threshold or level as indicated atblock911, themobile access point137 may then couple themobile host devices507,511,709,711 to thecommunication network101 through the secondstationary access133 point instead of the firststationary access point131 as indicated inblock913 ofFIG. 9. By following this procedure, data may be forwarded to themobile access point137 and any devices coupled to the communication network through themobile access point137 as it moves from one stationary access point to the next. The process ofFIG. 9 may end atblock915.
• If data is received by the communication network101 (e.g., from theexternal network125 or from a device coupled to the communication network101) destined for thehost device513, the data may be forwarded through thecommunication network101 through a plurality of forwarding devices (e.g.,117,119), as discussed above. The forwarding devices (117,119) may examine their respective address tables to determine how to forward the data based only data link layer information. Using the information in the forwarding tables, the data may be quickly forwarded to thehost device513 over long distances as if the host devices were attached to a local network of the other devices coupled to thecommunication network101.
• The second stationary access point may continue to couple themobile access point137 to thecommunication network101 until it receives a TCN indicating that the mobile access device has moved to a new stationary access point as indicated inblock821 ofFIG. 8. The process may then end atblock823.
• If themobile access point137 is coupled to thecommunication network101 through the firststationary access point131 when the data is received by thecommunication network101 but themobile access point137 moves to couple to thecommunication network101 through the secondstationary access point133 before the data reaches themobile access point137 or thehost device513, the data may not be forwarded properly to thehost device513. If the data does not reach thehost device513, data may be retransmitted to thecommunication network101 in accordance with a transport layer protocol (e.g., layer 4 of the OSI protocol), such as transmission control protocol (TCP), as is well-known in the art.
• It should be recognized that the above described embodiments are given as nonlimiting examples only. Other embodiments may include any arrangement and/or configuration desired. For example, in one embodiment of the present invention, the stationary access points may themselves be arranged on a moving platform such as a train or other vehicle. The stationary access points may be configured to communicate with a mobile device that is relatively stationary compared to the moving stationary access points. The stationary access points may be arranged such that the mobile device is in communication with at least one stationary access point as the platform or vehicle passes near the mobile device.
• Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this invention, and are intended to be within the scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.

Claims (4)

What is claimed is:

1. A communication system comprising:

a plurality of stationary access points coupled to a communication network; and

a mobile access point configured to communicate with the plurality of stationary access points and provide a plurality of host devices access to the communication network, wherein the mobile access point and the plurality of host devices move relative to the plurality of stationary access points;

wherein the plurality of stationary access points are disposed at spaced apart positions along a path traversed by the mobile device and each of the plurality of stationary access points transmits and receives signals through connection to a single leaky coaxial cable.

2. A communication system according toclaim 1 further comprising:

a first access point, a second access point, and a third access point connected to the leaky coaxial cable with the second access point being disposed between the first access point and the third access point along an extent of the leaky coaxial cable,

wherein the signal of the first access point extends beyond the second access point toward the third access point, and the signal of the third access point extends beyond the second access point toward the first access point.

3. A communication system according toclaim 1 wherein the leaky coaxial cable is placed within a tunnel.

4. A communication system according toclaim 2 wherein the leaky coaxial cable is placed within a passage under water.

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