USRE47545E1 - End-to-end delay management for distributed communications networks - Google Patents

Abstract

A method for calculating delay in a distributed antenna system includes sending a ping initiation message from a remote node to a host node in a distributed antenna system. The ping initiation message uniquely identifies a first communication port of the remote node to the host node with a unique identification. The method also includes receiving a ping reply message at the remote node. The ping reply message corresponds to the ping initiation message and also uniquely identifies the first communication port of the remote node with the unique identification. The method also includes determining, at the remote node, whether the ping reply message corresponds to the first communication port of the remote node based on the unique identification. The method also includes, when the ping reply message corresponds to the first communication port of the remote node, calculating the round-trip time delay between sending the ping initiation message and receiving the ping reply message at the remote node.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This Reissue Application is a reissue of application Ser. No. 13/165,294, filed Jun. 21, 2011, which issued as U.S. Pat. No. 8,743,718. The present application is related to commonly assigned and co-pending U.S. patent application Ser. No. 11/839,086 (hereafter “the '086 Application”) entitled “DELAY MANAGEMENT FOR DISTRIBUTED COMMUNICATIONS NETWORKS”, filed on Aug. 15, 2007 (currently pending). The present application is also related to commonly assigned and co-pending U.S. patent application Ser. No. 13/019,571 (hereafter “the '571 Application”) entitled “DELAY MANAGEMENT FOR DISTRIBUTED COMMUNICATIONS NETWORKS”, filed on Feb. 2, 2011. The '086 Application and the '571 Application are incorporated herein by reference in their entirety.

BACKGROUND

Distributed antenna systems are widely used to seamlessly extend coverage for wireless communication signals to locations that are not adequately served by conventional base stations or to distribute capacity from centralized radio suites. These systems typically include a host unit and a plurality of remote units. The host unit is typically coupled between a base station or radio suite and the plurality of remote units in one of many possible network configurations, such as hub and spoke, daisy-chain, or branch-and-tree. Each of a plurality of remote units includes one or more antennas that send and receive wireless signals on behalf of the base station or radio suites.

One common issue in distributed antenna systems is adjusting for the different delay associated with each of the remote units. Each remote unit is typically located at a different distance from the host unit. To allow the various antennas to be synchronized, a delay value is typically set at each remote unit. Unfortunately, conventional techniques used to establish the delay for the various remote units have added significant complexity and/or cost to the distributed antenna system. For example, some common network synchronization techniques involve the use of various locating technologies, such as global positioning systems (GPS), that add further complexities and cost to operating these distributed antenna systems reliably and efficiently.

For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for improvements in delay management for distributed communications networks.

SUMMARY

A method for calculating delay in a distributed antenna system includes sending a ping initiation message from a remote node to a host node in a distributed antenna system. The ping initiation message uniquely identifies a first communication port of the remote node to the host node with a unique identification. The method also includes receiving a ping reply message at the remote node. The ping reply message corresponds to the ping initiation message and also uniquely identifies the first communication port of the remote node with the unique identification. The method also includes determining, at the remote node, whether the ping reply message corresponds to the first communication port of the remote node based on the unique identification. The method also includes, when the ping reply message corresponds to the first communication port of the remote node, calculating the round-trip time delay between sending the ping initiation message and receiving the ping reply message at the remote node.

DRAWINGS

These and other features, aspects, and advantages are better understood with regard to the following description, appended claims, and accompanying drawings where:

FIG. 1A is a block diagram of one embodiment of a distributed communications network;

FIG. 1B is a block diagram of another embodiment of a distributed communications network;

FIG. 1C is a block diagram of another embodiment of a distributed communications network;

FIG. 2 is a block diagram of an application framework for a distributed communications network;

FIG. 3 is a block diagram of a data frame and detailed exemplary I and Q samples within a single timeslot within the data frame;

FIG. 4 is a flow diagram illustrating a method for calculating delay in a distributed antenna system;

FIG. 5A is a flow diagram illustrating a sub-method for calculating delay in a distributed antenna system at a remote node;

FIG. 5B is a flow diagram illustrating another sub-method for calculating delay in a distributed antenna system at a remote node; and

FIG. 6 is a flow diagram illustrating a sub-method for aiding a remote node in calculating delay in a distributed antenna system at a host node.

DETAILED DESCRIPTION

The following detailed description relates to delay management for distributed communications networks, such as a distributed antenna system. The delay management discussed here enables a network manager to establish a desired delay at a plurality of remote nodes in a point-to-multipoint or multipoint-to-multipoint communications network with a suitable high degree of repeatability and control. The desired delay can be for each of the remote nodes collectively or for each individual remote node. Advantageously, the communications network discussed here uses an end-to-end approach to determine a signal path delay from a host node to each remote node in the system. This is accomplished at each remote node by discovering a signal path delay (such as the travel time) over the link between the remote node and a host node. The signal path delay between each remote node and a host node accounts for individual processing delays of the remote nodes.

Once the signal path delays for each of the remote nodes are determined, the desired delay at each remote node can be definitively established by accounting for the signal path delay back to the host node and any known internal processing delays. In this manner, every remote node in the system is constantly aware of its distance (in signal time) from the host node. This allows each remote node to independently adjust the delay of its transmissions to maintain a selected delay in the system at each of the nodes. While much of this description describes an embodiment having a single host node, other embodiments include multiple host nodes connected to various remote nodes. In addition, signal path delays may be calculated from the remote node to a plurality of different host nodes.

Furthermore, the delay management discussed here does not require the use of additional node positioning and timing techniques (such as using GPS) to synchronize message delivery between the nodes. Rather than rely on a separate system (such as GPS timing references) to determine the timing delay between each of the nodes, the system and methods described herein provide a substantially simplified means of determining signal path delays between each of the remote nodes and a host node.

The delay management technique described herein is topology independent. The delay management technique is applicable to a wide range of network topologies, such as star, tree, and daisy-chained network configurations, and combinations thereof Moreover, this delay management is medium-independent, and functions on a plurality of network infrastructures, such as wireless, free space optics, millimeter wave, twisted pair, coaxial, optical fiber, hybrid fiber, and suitable combinations thereof.

FIGS. 1A-1B are block diagrams of embodiments of a communication network100. Each ofFIGS. 1A-1B shows a different embodiment of a communication network100. The various embodiments are labeledcommunications network100A throughcommunications network100B. It is understood that aspects of these embodiments can be combined together to create additional embodiments sharing features from any combination of the embodiments.

FIG. 1A is block diagram of one exemplary embodiment of a communications network100, labeledcommunications network100A. Thecommunications network100A represents a point-to-multipoint communications network that comprises a base station101, a host node102 responsive to the base station101, and remote nodes104-1 to104-M in communication with the host node102. The host node102 comprises a host base station interface103 and a host transport interface105 responsive to ahost node processor106. Each of the remote nodes104 (such as remote nodes104-1 to104-M) comprises a remote transport interface107 (such as remote transport interface107-1 to107-M) and an RF to digital interface109 (such as RF to digital interface109-1 to109-M), both responsive to a remote node processor108 (such as remote node processor108-1 to108-M). Each of the RF to digital interfaces109 (such as RF to digital interface109-1 to109-M) is further responsive to an antenna port110 (such as antenna port110-1 to110-M).

In some embodiments, eachhost node processor106 andremote node processor108 is configured to execute software or firmware (not shown) that causes thehost node processor106 and/or theremote node processor108 to carry out various functions described herein. The software comprises program instructions that are stored (or otherwise embodied) on an appropriate non-transitory storage medium or media (not show) such as flash or other non-volatile memory, magnetic disc drives, and/or optical dist drives. At least a portion of the program instructions are read from the storage medium byhost node processor106 and/orremote node processor108 for execution thereby. The storage medium on or in which the program instructions are embodied is also referred to here as a “program product”. In some embodiments, the storage medium is local to eachhost node processor106 and/orremote node processor108. In other embodiments, the storage medium is a remote storage medium (for example, storage media that is accessible over a network or communication link) and/or a removable media. In some embodiments, eachhost node processor106 and/orremote node processor108 also includes suitable memory (not shown) that is coupled tohost node processor106 and/orremote node processor108 for storing program instructions and data.

In some embodiments, each host base station interface103 and each RF todigital interface109 is implemented with a Digital/Analog Radio Transceiver (DART board) commercially available from ADC Telecommunications, Inc. of Eden Prairie, Minn. as part of the FlexWave™ Prism line of products. The DART board is also described in U.S. patent application Ser. No. 11/627,251, assigned to ADC Telecommunications, Inc., published in U.S. Patent Application Publication No. 2008/01101482, and incorporated herein by reference. In other embodiments, each host base station interface103 and each RF todigital interface109 is implemented with a plurality of DART boards, where one DART board is used for each port (such as D1, D2, D3) at a host node102 or aremote node104. In other embodiments, different ratios of DART boards to ports can be used. In other embodiments, some of the host base station interfaces103 do not convert between analog and digital and instead receive digital signals directly from the base station101. In these embodiments, the digital signals may be reframed, converted to a different frequency, or manipulated in other ways at host base station interfaces103, even though there is no conversion from analog RF spectrum to digitized RF spectrum.

In one embodiment, each host transport interface105 and eachremote transport interface107 is implemented with a Serialized RF (SeRF board) commercially available from ADC Telecommunications, Inc. of Eden Prairie, MN as part of the FlexWave™ Prism line of products. The SeRF board is also described in U.S. patent application Ser. No. 11/627,251, assigned to ADC Telecommunications, Inc., published in U.S. Patent Application Publication No. 2008/01101482, and incorporated herein by reference. In other embodiments, each host transport interface105 and eachremote transport interface107 is implemented with a plurality of SeRF boards, where one SeRF board is used for each port (such as T1, T2, T3) at a host node102 or aremote node104.

In one embodiment, thehost node processor106 and eachremote node processor108 are programmable processors, such as a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a field-programmable object array (FPOA), or a programmable logic device (PLD). It is understood that thenetwork100A is capable of accommodating any appropriate number ofremote nodes104 as described above incommunication network100A. In some embodiments,communication network100A includes fewerremote nodes104 than those shown inFIG. 1A. In other embodiments,system100A includes moreremote nodes104 than those shown inFIG. 1A.

The host node102 and theremote nodes104 are communicatively coupled by a plurality of signal paths in a tree-and-branch network configuration representing a plurality of levels. In the example embodiment ofcommunication network100A shown inFIG. 1A, the tree-and-branch network configuration further includes signal switches112 and113. Each of the signal paths illustrated inFIG. 1A are at least one of an electrical link, an optical fiber link, and a wireless transport link (such as millimeter wave, free space optics, or suitable combinations thereof), providing a medium-independent network architecture. It is understood that additional network configurations (such as a hub and spoke, a common bus, and the like) are also contemplated.

The host base station interface103 and each of the RF todigital interfaces109 include ports D1, D2, and D3. The ports D1, D2, and D3 are considered representative of a plurality of signal interference connections (such as RF, Ethernet, and the like) for the host base station interface103 and each of the RF todigital interfaces109. In some embodiments, the host base station interface103 converts between analog RF spectrum received from the base station101 and digitized spectrum that is communicated with theremote nodes104. In other embodiments, the host base station interface103 communicated digitized spectrum or signals with the base station101. In these embodiments, while the digitized spectrum or signals communicated with the base station101 are not converted between analog and digital, the framing of the digitized spectrum or signals may need to be converted between the digitized spectrum or signals communicated with the base station101 and the digitized spectrum communicated with theremote nodes104.

Similarly, the host transport interface105 and each of theremote transport interfaces107 include ports T1, T2, and T3. The ports T1, T2, and T3 are considered representative of a plurality of transport interface connections for the host transport interface105. Each of theremote transport interfaces107 provide an appropriate signal conversion (such as a digital to serial or serial optical fiber) for each of theremote nodes104 and the host node102 of thecommunication network100A. It is understood that the ports D1 to D3 and T1 to T3 shown inFIG. 1 are not to be considered limiting the number of signal interface and transport ports contemplated by the system discussed here (e.g., thecommunication network100A is capable of accommodating any appropriate number of instances of signal interface and transport ports).

Each remote node104 (such as remote node104-1 to104-M) introduces one or more intrinsic processing delays. For example, theremote transport interfaces107 includes a first intrinsic processing delay when passing signals between the transport interface connections T1 and T3 (commonly referred to as a “fiber-to-fiber” delay in this example). Similarly, each of the RF todigital interfaces109 includes a second intrinsic processing delay for converting signals between digital and RF. In some instances, the intrinsic processing delays in RF todigital interface109 are asymmetrical. This means that the intrinsic processing delay for upstream signals (signals going to the host node102) and the intrinsic processing delay for downstream signals (signals coming from the host node102) are different. In one embodiment, the various intrinsic processing delays are embedded in each of the remote node processors108 (such as remote node processor108-1 to108-M) for use in establishing the requested delay for the node.

In operation,communication network100A implements an end-to-end pinging process to determine the signal path delay between each port (such as D1, D2, and D3) in the RF todigital interface109 at eachremote node104 and a corresponding host base station interface103 at the host node102. In this end-to-end pinging process, each port in the RF todigital interface109 at eachremote node104 in thecommunication network100A discovers its signal path delay back to a corresponding port in the host base station interface103 of the host node102 by sending a ping message to the host node102 through thecommunication network100A. The corresponding port in the host base station interface103 of the host node102 returns the ping message to the corresponding port of the RF todigital interface109 of the pingingremote node104. The ping message is sent along a path between the pingingremote node104 and the host node102. A particular pingingremote node104 may be directly coupled with the host node102, such as with remote nodes104-1,104-2, and104-3.

A particular pingingremote node104 may also have otherremote nodes104 intervening between itself and the host node102, such as with remote node104-4 that has remote node104-1 intervening; remote node104-8 that has both remote node104-4 and104-1 intervening; remote node104-5 that has remote node104-2 intervening; remote node104-9 that has both remote nodes104-5 and104-2 intervening; remote node104-6 that has remote node104-3 intervening; and remote node104-10 that has both remote node104-6 and104-3 intervening. In addition, a particular pingingremote node104 may also have other components, or a combination of other components and other remote nodes, intervening between itself and the host node102, such as remote node104-7 that hassignal switches112 and113 and remote node104-3 intervening; and remote node104-M that has remote node104-7, signal switches112 and113, and remote node104-3 intervening. In other embodiments, any number of interveningremote nodes104 or other components (such as signal switches, etc.) may be intervening between a particularremote node104 and the host node102.

The signal path delay between a pinging port of the RF todigital interface109 of a particularremote node104 is calculated based on the elapsed round-trip ping time between sending a ping message from the pinging port of the RF todigital interface109 of theremote node104 and receiving back a corresponding reply ping message from the corresponding port of the host base station interface103 of the host node102. In some example embodiments, the signal path delay for a particularremote node104 is calculated to be this round-trip ping time. In other example embodiments, the signal path delay for a particularremote node104 is calculated to be a fraction of this round-trip ping time, such as one-half of the round-trip ping time. In other example embodiments, the signal path delay for a particularremote node104 is calculated from the round-trip ping time in other ways. While the precise method of calculation may vary from one embodiment to another, it is desirable that the method of calculation is consistent and defined for allremote nodes104 in thecommunication network100A so that the signal path delay values for eachremote node104 can be properly used to adjust the delay associated with eachremote node104 in thecommunication network100A.

Thus, each signal path delay between each pinging port of the RF todigital interface109 of eachremote node104 and the corresponding port of the host base station interface103 of the host node102 is calculated to represent the entire delay between the pinging port of the RF todigital interface109 of the particularremote node104 and the corresponding port of the host base station interface103 of the host node102, including any transport delay, internal processing delay, and other intrinsic processing delay present between the pinging port of the RF todigital interface109 of the pingingremote node104 and the corresponding port of the host base station interface103 of the host node102. By calculating the end-to-end ping between each port of each RF todigital interface109 of eachremote node104 and its corresponding port of the host base station interface103 of the host node102, it is not necessary to factor in the internal processing delay (or other intrinsic delay) at each intervening remote node between a particular pingingremote node104 and the host node102. The end-to-end ping is computationally less intensive than other methods requiring computation and aggregation of the delays associated with each hop between nodes in the network. The current system and method allow a reduction of resource usage and lower overhead at each node in thecommunication network100A.

Some embodiments of thecommunication network100A implement simulcast, where at least one of the ports of the host base station interface103 of the host node102 corresponds to a plurality of ports of at least one RF todigital interface109. For example, in some embodiments, at least one of the ports of the host base station interface103 of the host node102 corresponds to both a first port in a first RF todigital interface109 in a first remote node104 (such as RF to digital interface109-1 of remote node104-1) and a second port in a second RF todigital interface109 in a second remote node104 (such as RF to digital interface109-2 of remote node104-2 or any of the other RF todigital interfaces109 of any of the other remote nodes104). In these type of simulcast configurations, one port of the host base station interface103 of the host node102 communicates identical digitized spectrum in the forward link with a plurality of ports at a plurality of RF todigital interfaces109 at a plurality ofremote nodes104. In these type of simulcast configurations, the plurality of ports at the plurality of RF todigital interfaces109 at a plurality ofremote nodes104 communicate digitized spectrum in the reverse path that is aggregated and received at the single port of the host base station interface103 of the host node102. In some embodiments, the reverse path signal is aggregated through a series of summations. The actual method of aggregation of the simulcast may be done in various ways while still utilizing the methods and systems of end-to-end determination of delay described herein.

In some embodiments, it is necessary to add an internal processing delay and/or some other type of intrinsic delay associated with the particular pingingremote node104 and the host node102. Specifically, the host node may have some internal processing delay associated with its host base station interface103 (or any other internal processing delay not accounted for by the round-trip ping time) that can be used with the round-trip ping time and any other intrinsic delays that are not accounted for by the round-trip ping time to determine the signal path delay. In addition, the particular pinging remote node may have some internal processing delay associated with its RF todigital interface109 or the respective antenna port110 (or any other internal processing delay not accounted for by the round-trip ping time) that can be used with the round-trip ping time and any other intrinsic delays that are not accounted for by the round-trip ping time to determine the signal path delay.

The remote nodes104 (such as104-1 to104-M) use the signal path delay calculated through this process to control the overall delay selected for each RF todigital interface109 of eachremote node104. For example, a total delay for each RF todigital interface109 of each remote node may be established during network installation. Each RF todigital interface109 of each remote node sets the amount of delay that it introduces into signals based on the signal path delay learned using the above-described process. Thus, a common time base is established for RF todigital interfaces109 in theremote nodes104 incommunication network100A.

In addition to calculating signal path delay, the ping messages may be used to verify integrity of the round-trip path. Both ping messages sent from RF todigital interfaces109 ofremote nodes104 and reply ping messages sent from host base station interfaces103 of host nodes102 may be protected and validated by a cyclic redundancy check (CRC). In some embodiments, messages received at either host base station interfaces103 of the host node102 or RF todigital interfaces109 ofremote nodes104 with invalid CRCs are ignored. Specifically, when a ping message received at a hostdigital interface109 of a host node102 is identified as having an invalid CRC, the host base station interface103 of the host node102 will not send a reply ping message in response. Similarly, when a ping message received at a RF todigital interface109 of aremote node104 is identified as having an invalid CRC, the RF todigital interface109 of theremote node104 ignores the invalid message. In some embodiments, there may be other types of validity checks used to validate the integrity of the messages transmitted through thecommunication network100A.

In addition, due to the simulcast nature of thecommunication network1 OOA, a first reverse path ping message initiated by a RF todigital interface109 of one of the remote nodes104 (such as RF to digital interface109-1 of remote node104-1) might collide with a second reverse path ping message initiated by another RF todigital interface109 of another one of the remote nodes104 (such as RF to digital interface109-2 of remote node104-2). A collision between two ping messages may cause both messages to be corrupted so that neither ping message is received intact at a host base station interface103 of a host node102 (such as host base station interface103-1 of host node102-1). The corrupted message received at the host base station interface103 of the host node102 may include bits from both the first and second reverse path ping messages. Such a corrupted message will be identified as invalid by the CRC performed by the host base station interface103 of host node102 and will not be replied to by the host base station interface103 of host node102.

To detect and recover from a collision, an embodiment ofcommunication network100A may include configuration of each RF todigital interface109 at eachremote node104 to detect whether or not it has received a valid ping reply message from the replying host digital interface103 of the replyinghost node104 in response to its initial ping message within a predefined amount of time. If a ping reply message is received at the pinging RF todigital interface109 of the pingingremote node104 before expiration of a predefined response and the ping message both: (1) has a valid CRC; and (2) corresponds to the pinging RF todigital interface109 of the pingingremote node104, then the round-trip delay and signal path delay are calculated. Alternatively, if no ping reply message that both (1) has a valid CRC and (2) corresponds to the pinging RF todigital interface109 of the pingingremote node104 is received at the pinging RF todigital interface109 of the particularremote node104, then the ping message is resent when the next ping trigger occurs. Ping triggers occur at pseudo-random time intervals. The ping trigger interval may be determined at each pinging remote node based on a pseudo-random back-off algorithm to minimize the chance of a collision between other upstream messages.

While the detection, timeout, retry cycle above could repeat indefinitely, some embodiments ofcommunication network100A may further calculate how many times a particular ping message has been sent from a pinging RF to digital interface of a pingingremote node104 without a valid corresponding reply ping message having been received. If the particular ping message has been resent by the pinging RF to digital interface103 of the pingingremote node104 over a predetermined number of times without having received a valid corresponding reply ping message, then a path integrity alarm may be reported at the particular pingingremote node104 in thecommunication network100A indicating that something is wrong with the data path between the pinging RF todigital interface109 of the pingingremote node104 and the corresponding host base station interface103 of the corresponding host node102. This path integrity alarm may alert a technician to a potential data path error so that the technician can investigate and correct the issue. The number of messages that must fail before the remote node reports a path integrity alarm may be predetermined when thecommunication network100A is deployed, but may also be adjusted later. In other embodiments, a timeout period is used instead of a ping trigger.

In addition to calculating the end-to-end ping and verifying the integrity of the round-trip paths, the ping messages may also be used to mute and un-mute the transmission and reception from an antenna coupled to a port of an RF todigital interface109 on aremote node104. In some embodiments, a certain number of valid ping messages need to be received back at a pinging RF todigital interface109 of aremote node104 before the pinging RF to digital interface un-mutes a port coupled to the associatedantenna port110, allowing transmission and reception of a particular band through the data path between the port of the RF to digital interface109 (such as port Dl of RF to digital interface109-4 of remote node104-4) and a host base station interface103 (such as port D1 of host base station interface103 of host node104) coupled to a service provider interface of base station101 (such asservice provider interface1 of base station101-1). This features ensures the integrity of the path and compatibility between the pinging RF todigital interface109 and the host base station interface103 before un-muting the communications.

FIG. 1B is block diagram of another exemplary embodiment of a communications network100, labeledcommunications network100B. Thecommunications network100B represents a multipoint-to-multipoint communications network that shares many components withcommunications network100A shown inFIG. 1A and described above. The primary distinction betweencommunications network100B andcommunication network100A is thatcommunication network100B includes two or more host nodes102 (such as host node102-1 and host node102-2) coupled with two or more base stations101 (such as base station101-1 and base station101-2). Incommunications network100B, a singleremote node104 can be coupled to a plurality of host nodes102 (such as remote node104-2 which is connected to both host node102-1 and host node102-2).

In embodiments having two host nodes, a single remote unit may have two RF todigital interfaces109, where one is associated with a host base station interface103 in one host node102 (such as host base station interface103-1 of host node102-1) and the other is associated with a different host base station interface103 in another host node102 (such as host base station interface103-2 in host node102-2). In other embodiments having two hosts nodes, one port of a RF todigital interface109 of a remote node (such as D1 of RF to digital interface109-2 of remote node104-2) may be associated with one port of one host base station interface103 in a host node102 (such as D1 of host base station interface103-1 of host node102-1).

In embodiments where each remote node has multiple RF todigital interfaces109, ping messages are sent for each of the RF todigital interfaces109 to a host node102 having a hostdigital interface109 associated with the respective RF todigital interface109. In some embodiments where aremote unit104 is communicatively coupled to a plurality of host nodes102, one port of RF todigital interface109 of the remote unit104 (such as D1 of RF to digital interface109-1 of remote node104-4) may be associated with a host base station interface103 of one host node102 (such as host base station interface103-1 of host node102-1) while another port of RF todigital interface109 of the remote node104 (such as D2 of RF to digital interface109-1 of the remote node104-4) may be associated with a host base station interface103 of another host node102 (such as host base station interface103-2 of host node102-2).

An additional distinction betweencommunications network100B andcommunications network100A is thatcommunication network100B includes analog remote nodes114 (such as analog remote nodes114-1 and114-M coupled to remote node104-11). In embodiments implementing analog remote nodes, intermediate frequencies (IF) may be used to transmit multiple bands across a single analog medium. For example, a remote node104 (such as remote node104-11) includes an analog IF to digital interface111 (such as analog IF to digital interface111-1) that converts between digitized RF spectrum received from the associated host node102 and an analog IF frequency sent across the analog medium to an analog remote node114 (such as analog remote node114-1). In some embodiments, each analog remote node114 (such as analog remote node114-1 through analog remote node114-M) includes an analog IF transport interface113 (such as analog IF transport interface113-1 through analog IF transport interface113-M) and an IF to RF interface116 (such as IF to RF interface116-1 through IF to RF interface116-M) responsive to an analog remote node processor118 (such as analog remote node processor118-1 through analog remote node processor118-M). Each of the IF to RF interfaces116 (such as IF to RF interface116-1 to116-M) is further responsive to an antenna port110 (such as antenna port110-12 to110-M).

As is shown in the example embodiment shown inFIG. 1B, a plurality of analog remote nodes can be daisy chained off from a remote node in thecommunications network100B. In other embodiments, other network topologies can be used in both the digital and analog portions of thecommunications network100B. In the example embodiment shown inFIG. 1B, the end-to-end ping is only calculated in the digital portions of thenetwork100B. In some embodiments, an analog IF to digital interface111 of a remote node104 (such as analog IF to digital interface111-1 of remote node104-11) calculates an end-to-end ping to a host base station interface103 of a host node102 (such as host base station interface103-1 of a host node102-1) using the methods described herein. The remote node104-11 can then add in some intrinsic delay to account for the delay through the various portions of the analog system (such as to IF to RF interface116-1 of analog remote node114-1 and IF to RF interface116-M of analog remote node114-M). In this way, the end-to-end delay between the analog nodes can also be estimated.

In other embodiments, the additional delay in the analog portion of thecommunications network100B is disregarded because it is insubstantial compared to the delay introduced by the digital portion of thecommunication network100B. This may be the case because the distances between theremote nodes104 and the host nodes102 in the digital domain is much greater than the distances between the analogremote nodes114 and theremote nodes104 they are connected to (such as remote node104-11).

FIG. 1C is a block diagram of another exemplary embodiment of a communications network100, labeledcommunications network100C. Thecommunications network100C represents a communications network that includes the host node102-1 and the remote node104-1. Each of host node102-1 and remote node104-1 include the components describe above. In some embodiments, additionalremote nodes104 or other components lie between host node102-1 and remote node104-1 in optionalintervening component section120. In some embodiments, optionalintervening component section120 includes interveningremote nodes104, signal switches, and physical links, such as optical fibers, coaxial cables, and wireless links. Thecommunications network100C implements an end-to-end ping as described herein. The precise contents of the optionalintervening component section120 is not particularly relevant to the end-to-end ping as long as the components in the optionalintervening component section120 properly forward any ping initiation messages and ping reply messages between the host node102-1 and remote node104-1.

FIG. 2 is a block diagram of aframework200 for network applications. Theframework200 comprises multiple layers, discussed below, that provide hardware-related service to enable each node of thecommunication network100A to function as shown above with respect toFIG. 1 (e.g., the host node102 discovers the plurality ofremote nodes104 over thecommunication network100A). Theframework200 comprises anapplication layer202, anetwork layer204, adata link layer206, and aphysical layer208. Each layer of theframework200 compartmentalizes key functions required for any node of the communication network100 to communicate with any other node of the communication network100.

Thephysical layer208 is communicatively coupled to, and provides low level support for thedata link layer206, thenetwork layer204, and theapplication layer202. In some embodiments, thephysical layer208 resides on at least one of an optical fiber network, a coaxial cable network, and a wireless network. Thephysical layer208 provides electronic hardware support for sending and receiving data in a plurality of operations from the at least one network application hosted by the host node102. Thedata link layer206 provides error handling for thephysical layer208, along with flow control and frame synchronization. Thedata link layer206 further includes adata frame sub-layer210. Thedata frame sub-layer210 comprises a plurality of data frames transferred on thephysical layer208. Additional detail pertaining to thedata frame sub-layer210 is further described below with respect toFIG. 3. Thenetwork layer204 is responsive to at least one programmable processor within the network100 (for example, thehost node processor106 or at least one of the remote node processors108). Thenetwork layer204 provides switching and routing capabilities within the network100 for transmitting data between the nodes within the network100. Theapplication layer202 is responsive to at least one of a simple network management protocol (SNMP), a common management information protocol (CMIP), a remote monitoring (RM) protocol, and any network communications protocol standard suitable for remote monitoring and network management.

FIG. 3 is a block diagram of an embodiment of thedata frame sub-layer210 ofFIG. 2, represented generally by the sub-layer300. The sub-layer300 comprises at least one data frame302 (or optical fiber frame). Eachdata frame302 is composed of a plurality of slots organized into rows and columns as shown inFIG. 3. Each RF todigital interface109 of eachremote node104 is assigned at least one timeslot in the reverse path to transmit digitized RF spectrum to a host base station interface103 of a host node102. In addition, each RF todigital interface109 of eachremote node104 is assigned at least one timeslot in the forward path to receive digitized RF spectrum from a host base station interface103 of a host node102. In some embodiments, a single RF todigital interface109 is assigned multiple slots in the upstream and/or the downstream. Similarly, in some embodiments, a single host base station interface103 is assigned multiple slots in the upstream and/or downstream. In some embodiments, implementing simulcast in the forward path, a single host base station interface103 of a host node102 may transmit digitized RF spectrum in the downstream on at least one timeslot that is received at a plurality of RF todigital interfaces109 at a plurality ofremote nodes104. Similarly, in the reverse path, a plurality of RF todigital interfaces109 at a plurality ofremote nodes104 may transmit digitized RF spectrum in the upstream on the same timeslot, where the digitized RF spectrum is summed together or aggregated in some other way.

Each timeslot, such asexample timeslot304, is composed of anI sample306 and aQ sample308. In theexample timeslot304, both theI sample306 and theQ sample308 include 16 bits. In theexample timeslot304, the 16th bit of the I sample, bit310, is used to transmit the ping messages. In some embodiments, a single bit310 is used in each timeslot of thedata frame302 to transmit the ping messages. Thus, a ping message can span multiple slots in a frame and can also span across frames. In the embodiments shown inFIG. 3, where only one bit per timeslot is used to transmit the ping message, it may take multiple frames to transmit a single ping message.

For example, in some embodiments, the ping message contains approximately80 bits, requiring80 slots for transmission. Thus, in an embodiment where an RF todigital interface109 is assigned one timeslot per row of thedata frame302, it would take five frames to transmit the80 bits of one ping message. Similarly, in an embodiment where an RF todigital interface109 is assigned two timeslots per row of thedata frame302, it would take two and a half frames to transmit the80 bits of one ping message. The combined bits representing the ping message spanning multiple frames are sometimes referred to as a ping message superframe.

An example embodiment of a ping message having 80 bits may include a number of elements. First, a frame header may require 8 bits. The frame header is used to frame the message and identify the message type. Example message types include (1) messages initiated from a remote RF todigital interface109 and directed toward an analog host base station interface103, (2) messages initiated from a remote RF todigital interface109 and directed toward a digital host base station interface103, (3) messages initiated from an analog host base station interface103 and directed toward a remote RF todigital interface109, and (4) messages initiated from a digital host base station interface103 and directed toward a remote RF todigital interface109. The digital host base station interface103 is discussed above as being used when the base station outputs a digital signal to the host node102 instead of an RF signal.

Second, a time slot count may require 4 bits. The timeslot count is used to identify the number of timeslots the sending DART is programmed to. This timeslot count should agree between the RF todigital interface109 and the corresponding host base station interface103 and can be used to verify that the network is correctly configured and/or the integrity of the path the ping message is being sent on.

Third, a host base station interface ID may require 8 bits. The host base station interface ID is a unique identifier code for the host base station interface103 that may be inserted into the ping reply message by the host base station interface103. The RF todigital interface109 at the pingingremote node104 can then verify that it is compatible with the type of the host base station interface103 based on the host base station interface ID received back in the ping reply message. If the RF todigital interface109 at the pingingremote node104 is not compatible with the type of host base station interface103 identified in the host base station interface ID, the RF todigital interface109 can be muted and an alarm can be triggered to indicate a mismatch between the types of the pinging RF todigital interface109 the host base station interface103.

Fourth, a unique path code may require 37 bits. The unique path code is a unique value that identifies the path between the RF todigital interface109 and the host base station interface103. This unique value serves as a unique identifier for each RF todigital interface109 in the system100. In the example embodiment using a 37-bit path code, the system100 can have up to 8 levels of cascades between the host node and a RF todigital interface109. In other embodiments, path codes of different lengths can also be used, enabling various sizes of networks and levels of cascades. In some embodiments, this unique path code is supplied to the RF todigital interface109 by theremote transport interface107 of theremote node104.

In some embodiments, the unique path code includes a 4-bit host node ID number that identifies the host node102 that contains the corresponding host base station interface103. In embodiments having a 4 bit host node ID number, there are only 16 options for host node ID numbers. If the host base station interface103 receives a ping message that has a host node ID number that does not match its own, then the message is ignored.

In some embodiments, the unique path code also includes a 3-bit host base station interface ID number that identifies the target host base station interface103 within the host node102. In some embodiments, the base station interface ID number also identifies a particular port within the host base station interface103 of the host node102. In some embodiments, the base station interface ID number identifies a communication port, such as a low-voltage differential signaling (LVDS) port, of the target host base station interface103 within the host node102.

In some embodiments, the unique path code also includes a27 bit fiber path ID that identifies the path between the host node102 and theremote node104. This unique path code may be broken into nine 3-bit values. The first 3-bit value represents the number of levels minus one in the cascaded mesh. For example, a system that only contains a host and a remote would have “000” in this field. The next eight 3-bit values represent the fiber port number of each link in the cascade. In systems with fewer than eight levels, the corresponding 3-bits will be unused and set to “000”.

In some embodiments, the unique path code also includes a 3-bit RF to digital interface ID number that identifies the pinging RF todigital interface109 within theremote node104. In some embodiments, the base station interface ID number also identifies a particular port within the RF todigital interface109 of the pingingremote node104. In some embodiments, the RF to digital interface ID number identifies a low-voltage differential signaling (LVDS) port of the pinging RF todigital interface109 within the pingingremote node104.

Fifth, a cyclic redundancy check (CRC) code may require 15-bits. The CRC code may be used to verify the integrity of the ping message. If the CRC fails at the host node102, no ping reply message will be sent or any returned ping reply message will be incomplete.

Sixth, an additional miscellaneous control status code may require 8-bits. This miscellaneous control status code could be used for other features and functions in the system.

The above description of the components of the ping message describe an exemplary embodiment and it is understood that the amount of bits used by each component and the components included in the ping message may be adjusted as appropriate in specific embodiments.

To determine the end-to-end signal path delay between each RF todigital interface109 on eachremote node104 and a corresponding host base station interface103 on the host node102, a ping message is sent in the reverse path from each RF todigital interface109 on eachremote node104 to a host base station interface103 of ahost node104. Upon reception, the host base station interface103 of thehost node104 validates each ping message received. This validation may include validation of the message type, the host base station interface type, the host node ID number, the host base station ID number, and the CRC code. In some embodiments, a mismatch between any of these validated items and expected values causes the host base station interface103 to ignore the ping message. In other embodiments, only mismatches of some of the items listed above would cause the host base station interface103 to ignore the ping message. In other embodiments, the host base station interface103 orhost node processor106 could trigger an alarm if certain items are not validated.

If a particular ping message is validated at thehost node104, thehost node104 replies to the pingingremote node104 with a similar reply ping message in the forward direction. Both ping messages sent in the reverse path from theremote nodes104 to the host node102 and the reply ping messages sent in the forward path from the host node102 to the pingingremote nodes104 include a unique identifier that identifies the particular RF todigital interface109 uniquely from all the other RF todigital interfaces109. In some embodiments, the reply ping message is identical to the ping message. In other embodiments, the host base station interface103 edits or adds to the received ping message in its reply ping message. The replying host base station interface103 of the host node102 sends the reply ping message back toward the pinging RF todigital interface109 of the pingingremote node104.

The pinging RF todigital interface109 of the pingingremote node104 identifies that a reply ping message corresponding to its ping message has been received back by comparing the returned unique identifier with its unique identifiers. If the returned unique identifier matches a particular RF todigital interface109 at one of theremote nodes104, the pinging RF todigital interface109 of the pingingremote node104 calculates total round-trip delay time between the initial transmission of the ping message and the receipt of the corresponding return ping message.

While the RF todigital interfaces109 of theremote nodes104 are described as performing the ping message transmission, reply ping message receipt, reply ping message validation, and round-trip delay calculation, in other embodiments, some or all of these actions are offloaded to theremote node processors108 or other components of theremote node104. Similarly, while the host base station interfaces103 of the host nodes102 are described as performing the ping message receipt, ping message validation, reply ping message transmission, and alarm generation, in other embodiments, some or all of these actions are offloaded to thehost node processors106.

FIG. 4 shows an exemplary embodiment of a method flow diagram for amethod400 for calculating delay in a distributed antenna system. Themethod400 begins atblock402, with calculating a delay in a distributed antenna system at a remote node. In example embodiments, block402 is implemented using any ofmethods500A-B described below. Themethod400 proceeds to block404, with aiding the remote node in calculating delay in a distributed antenna system at a host node. In example embodiments, block404 is implemented using sub-method600 described below. It is understood that thevarious methods500A-B and600 can be combined in various ways while still being within the scope of the claims below.

FIG. 5A shows an exemplary embodiment of a method flow diagram for a sub-method500A for calculating delay in a distributed antenna system at a remote node. The sub-method500A begins atblock502, where the sub-method500A waits for the next ping trigger to occur. Ping triggers cause the method to advance. It is desirable that the ping triggers occurring at various remote nodes in a distributed antenna system are staggered so that there is less likely a collision between the ping initiation messages and ping reply messages. Thus, in some embodiments, the ping triggers occur at pseudo-random intervals so that ping messages from each of the remote units are less likely to interfere with one another. In some embodiments, block502 is optional and the sub-method500A does not wait for thenext ping trigger502 and instead immediately proceeds to block504.

Once the ping trigger occurs atblock502, the sub-method500A proceeds to block504, where a ping initiation message that uniquely identifies a first communication port of a remote node is sent from the remote node to a host node through a network. In some embodiments, the first communication port is part of a RF to digital interface and an antenna is coupled to the first communication port. In other embodiments, the first communication port is part of the transport interface that couples the remote node to the host node in the distributed antenna system.

The sub-method500A proceeds to block506, where it is determined whether a ping reply message is received before a predefined time period is elapsed since the ping initiation message was sent. Generally, this predetermined time period is selected to be long enough to allow a host node to receive and respond with a ping reply message to the remote unit. The predetermined time period is also selected to be short enough so that the ping message does not become stale. In some embodiments, block506 is optional and the sub-method500A does not determine whether the ping reply message is received before a predefined time period has elapsed and instead immediately proceeds to block508.

If it is determined atblock506 that the ping reply message is received before the predefined time period is elapsed since the ping initiation message was sent, then the sub-method500A branches to block508, where it is determined whether the ping reply message uniquely identifies the first communication port of the remote node that was identified in the ping initiation message. In some embodiments, this determination is made by comparing a first unique identification sent from the remote node in the ping initiation message with a second unique identification received at the remote node in the ping reply message. If the first unique identification and the second unique identification match, then the ping reply message uniquely identifies the first communication port of the pinging remote node.

If it is determined atblock508 that the ping reply message uniquely identifies the first communication port of the remote node that was identified in the ping initiation message, then the sub-method500A branches to block510, where it is determined whether the ping reply message has been successfully received a predefined number of times. Successfully receipt occurs each time it is determined atblock508 that the ping message uniquely identifies the first communication port of the remote node. In some embodiments, a counter keeps track of how many successful receipts have occurred. In some embodiments, requiring a certain number of successful receipts before calculating the round-trip delay allows the sub-method500A to be used to validate the integrity of the data path on which the ping messages are being sent, which increases the likelihood that the round-trip delay is accurate. In some embodiments, block510 may be used to un-mute the transmission and reception from an antenna coupled to a corresponding port of an RF to digital interface on the remote node, once the method is confident the integrity of the path is established. Until the integrity of the path is established by receiving the ping message successfully the predefined number of times, the transmission and reception from the antenna coupled to the corresponding RF to digital interface on the remote will be muted. In addition, the data path can be muted if it is determined that there is no data path integrity, such as atblock516.

If it is determined atblock510 that the ping message has been successfully received a predefined number of times, then the sub-method500A branches to block512, where the round-trip delay between last sending the ping initiation message and receiving the ping reply message at the remote node is calculated at the remote node. In some embodiments, this round-trip delay is used with round-trip delays associated with other remotes in a distributed antenna system to synchronize the delays between the various remotes in the distributed antenna system.

The sub-method500A next proceeds to block514 where the attempt count and message received count are reset and the method returns to block502, where the sub-method500A waits for the next ping trigger to occur and the method repeats. The method is continually repeated to keep the round-trip delays continually updated.

If it is determined atblock506 that the ping reply message is not received before the predefined time period is elapsed since the ping initiation message was sent, then the sub-method500A branches to block516, where it is determined whether a predefined number of unsuccessful attempts at sending the ping initiation message has been reached. If it is determined atblock516 that the predefined number of unsuccessful attempts at sending ping invitation messages has been reached, then the sub-method500A branches to block518, where an integrity alarm is reported. The integrity alarm indicates that there is something wrong with the integrity of the path between the pinging remote node and the host node. In some embodiments, the integrity alarm indicates which of test was failed, such as any of the tests in decision blocks506,508, and510. In some embodiments, the sub-method500A continues ontoblock514 and repeats according to the description above to see if a round-trip delay can still be determined. In other embodiments, once an integrity alarm is reported, the method will stop until the distributed antenna system is serviced to correct the integrity issue in the path.

If it is determined atblock508 that the ping reply message does not uniquely identify the first communication port of the remote node that was identified in the ping initiation message, then the sub-method500A braches to block516, where it is determined whether a predefined number of unsuccessful attempts at sending the ping initiation message has been reached and continues as described above.

If it is determined atblock510 that the ping reply message has not been successfully received a predefined number of times, then the sub-method500A branches to block516, where it is determined whether a predefined number of unsuccessful attempts at sending the ping initiation message has been reached and continues as described above. In other embodiments, if it is determined atblock510 that the ping reply message has not been successfully received a predefined number of times, then the sub-method500A branches directly back to block502 without going first to block516.

In addition, it is understood that some of the blocks of sub-method500A can be rearranged without departing from the scope of the claims below. Specifically, in some embodiments, blocks506,508, and510 are in different orders, such that the various tests are performed in a different order. In some embodiments, after the round trip-delay is calculated, a signal path delay (as described above) is calculated at the remote node based on the round-trip delay.

FIG. 5B shows an exemplary embodiment of a method flow diagram for a sub-method500B for calculating delay in a distributed antenna system at a remote node. The sub-method500B shares blocks504,508, and512 with sub-method500A, but omits the other steps found in sub-method500A.

Specifically, the sub-method500B begins atblock504, where a ping initiation message that uniquely identifies a first communication port of a remote node is sent from the remote node to a host node through a network. In some embodiments, the first communication port is part of a RF to digital interface and an antenna is coupled to the first communication port. The sub-method500B proceeds to block508, where it is determined whether the ping reply message uniquely identifies the first communication port of the remote node that was identified in the ping initiation message.

If it is determined atblock508 that the ping reply message uniquely identifies the first communication port of the remote node that was identified in the ping initiation message, then the sub-method500B continues to block510, where it is determined whether the ping reply message has been successfully received a predefined number of times. Successfully receipt occurs each time it is determined atblock508 that the ping message uniquely identifies the first communication port of the remote node. In some embodiments, a counter keeps track of how many successful receipts have occurred.

In some embodiments, if it is determined atblock508 that the ping reply message does not uniquely identify the first communication port of the remote node, then the sub-method500B branches tooptional block520, where the exception is handled. In some embodiments, theoptional block520 triggers errors or simply ignores the reply message that does not uniquely identify the first communication port of the remote node.

It is understood that any combination of the steps of sub-method500A that are omitted from sub-method500B could be used as optional steps insub-method500B. In addition, the sub-method500B could be repeated to send more ping initiation messages and receive more ping reply messages.

FIG. 6 shows an exemplary embodiment of a method flow diagram for a sub-method600 for aiding a remote node in calculating delay in a distributed antenna system at a host node. The sub-method600 can be implemented in concert with sub-method500A described above to implement a method of performing a complete end-to-end ping. The sub-method600 begins at block501 and proceeds to block602, where a ping initiation message is received at a host node. In some embodiments, the remote node includes a host base station interface and the host base station interface receives the ping initiation message. In some embodiments, the ping initiation message is a ping message sent from a remote unit in a network.

The method proceeds to block604, where the ping initiation message is validated. The ping initiation message can be validated in a number of ways, including but not limited to, validation of a CRC code, a message type, a host base station interface type, a host node ID number, and/or a host base station ID number. The validation of some of these values can occur by simply comparing the value received in the ping initiation message with an expected value stored in the host node102.

If the ping initiation message is validated atblock604, then the sub-method600 branches to block606, where the ping reply message that uniquely identifies a second communication port of the remote node is sent from the host node to the remote node. The sub-method600 next continues back to block602, where another ping initiation message is received and the sub-method600 is repeated. In some embodiments, this second ping initiation message is from the same remote unit as the first ping initiation message. In other embodiments, this second ping initiation message is from a different remote unit as the second ping initiation message.

If the ping initiation message is not validated atblock604, then the sub-method600 branches to block608, where the ping initiation message is ignored. In other embodiments, an alarm can be triggered by the lack of validation of the message. The triggered alarm may include an indication of how the ping initiation message failed validation. In other embodiments, there is noblock608. The sub-method600 next continues back to block602, where another ping initiation message is received and the sub-method600 is repeated. In some embodiments, this second ping initiation message is from the same remote unit as the first ping initiation message. In other embodiments, this second ping initiation message is from a different remote unit as the second ping initiation message.

In some embodiments, each of the sub-methods described above, such assub-method500A, sub-method500B, and sub-method600, are implemented as individual methods.

Claims (44)

The invention claimed is:

1. A distributed antenna system comprising:

a host node including a host node processor, the host node having a first communication port communicatively coupled to a base station of a mobile telephone network, the host node also having a second communication port;

a first remote node in communication with the host node, the first remote node including a first remote node processor, a third communication port communicatively coupled to the second communication port of the host node across a first distinct signal path, and a fourth communication port communicatively coupled to a first antenna;

a second remote node in communication with the host node, the second remote node including a second remote node processor, a fifth communication port communicatively coupled to at least one of a third communication port of the host node and a sixth communication port of the host node and a seventh communication port of the first remote node across a second distinct signal path, and a seventh an eighth communication port communicatively coupled to a second antenna;

wherein the first remote node processor comprises program instructions that:

cause the first remote node to send a first ping initiation message to the host node across the first distinct signal path as a part of a process to determine signal delay, wherein the first ping initiation message includes a first unique identification that uniquely identifies at least one of the third communication port and the fourth communication port of the first remote node to the host node;

cause the first remote node to determine whether a first ping reply message received sent as a part of the process to determine signal delay from the host node that is received from the first remote node corresponds to the at least one of the third communication port and the fourth communication port of the first remote node based on the first unique identification; and

when the first ping reply message received from the host node corresponds to the at least one of the third communication port and the fourth communication port of the first remote node, cause the first remote node to calculate a first elapsed time between sending the first ping initiation message and receiving the first ping reply message;

wherein the second remote node processor comprises program instructions that:

cause the second remote node to send a second ping initiation message to the host node across the second distinct signal path as a part of the process to determine signal delay, wherein the second ping initiation message includes a second unique identification that uniquely identifies at least one of the fifth communication port, the sixth communication port, and the seventh eighth communication port of the second remote node to the host node;

cause the second remote node to determine whether a second ping reply message received sent as a part of the process to determine signal delay from the host node that is received from the second remote node corresponds to the at least one of the fifth communication port, the sixth communication port, and the seventh eighth communication port of the second remote node based on the second unique identification; and

whereinwhen the second ping reply message received from the host node corresponds to the at least one of the fifth communication port, the sixth communication port, and the seventh eighth communication port of the second remote node, cause the second remote node to calculated calculate a second elapsed time between sending the second ping initiation message and receiving the second ping reply message; and

wherein the host node processor comprises program instructions that:

cause the host node to validate the first ping initiation message received from the first remote node;

when the first ping initiation message is validated, cause the host node to send the first ping reply message to the first remote node, wherein the first ping reply message corresponds to the first ping initiation message and also uniquely identifies the at least one of the third communication port and the fourth communication port of the first remote node;

cause the host node to validate the second ping initiation message received from the second remote node; and

whereinwhen the second ping initiation message is validated, cause the host node to send the second ping reply message to the second remote node, wherein the second ping reply message corresponds to the second ping initiation message and also uniquely identifies the at least one of the fifth communication port, the sixth communication port, and the seventh eighth communication port.

2. The distributed antenna system ofclaim 1, wherein the first unique identification is a path code that identifies a first path between the at least one of the third communication port and the fourth communication port of the first remote node and at least one of the first communication port and the second communication port of the host node.

3. The distributed antenna system ofclaim 2, wherein the path code uniquely identifies the host node, the at least one of the first communication port and the second communication port, the at least one of the third communication port and the fourth communication port, and the first distinct signal path between the host node and the first remote node.

4. The distributed antenna system ofclaim 1, wherein the first remote node is separated from the host node by at least one additional remote node.

5. The distributed antenna system ofclaim 1, wherein at least one of the first communication port and the fourth communication port is part of a radio frequency to digital interface that converts between radio frequency signals and digital signals.

6. The distributed antenna system ofclaim 1, wherein a single bit in each timeslot of a data frame is used to transmit the first ping initiation message and the first ping reply message.

7. The distributed antenna system ofclaim 1, wherein the first remote node processor program instructions further cause the first remote node to:

verify whether the fourth communication port of the first remote node is compatible with a first type of the first communication port of the host node based on the first ping reply message received from the host node.

8. The distributed antenna system ofclaim 7, wherein the first remote node processor program instructions further cause the first remote node to at least one of:

mute the fourth communication port of the first remote node when it is determined that the fourth communication port of the first remote node is not compatible with the first type of the first communication port of the host node; and

trigger an alarm to indicate a mismatch between the first type of the first communication port of the host node and the fourth communication port of the first remote node.

9. The distributed antenna system ofclaim 1, wherein the host node processor program instructions cause the host to validate the first ping initiation message received from the first remote node by validating at least one of a message type, a host base station interface type, a host node ID number, a host base station ID number, and a cyclic redundancy check code.

10. The distributed antenna system ofclaim 1, wherein the host node processor program instructions further cause the host node to:

trigger an alarm if certain items in the first ping initiation message received from the first remote node are not validated by the host node.

11. The distributed antenna system ofclaim 1, wherein at least one of the host node processor and the first remote node processor is at least one of a programmable processor, a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a field-programmable object array (FPOA), and a programmable logic device (PLD).

12. A method for calculating delay in a distributed antenna system comprising:

sending a first ping initiation message from a first remote node in the distributed antenna system to a host node in the distributed antenna system across a first distinct signal path coupling the first remote node to the host node as a part of a process to determine signal delay, wherein the first ping initiation message uniquely identifies a first communication port of the first remote node to the host node with a first unique identification;

receiving a first ping reply message at the first remote node from the host node, the first ping reply message transmitted from the host node to the first remote node across the first distinct signal path coupling the first remote node to the host node;

determining, at the first remote node, whether the first ping reply message sent as a part of the process to determine signal delay uniquely identifies the first communication port of the first remote node with the first unique identification;

when the first ping reply message uniquely identifies the first communication port of the first remote node, calculating a first round-trip time delay between sending the first ping initiation message and receiving the first ping reply message at the first remote node;

sending a second ping initiation message from a second remote node in the distributed antenna system to the host node in the distributed antenna system across a second distinct signal path coupling the second remote node to the host node as a part of the process to determine signal delay, wherein the second ping initiation message uniquely identifies a second communication port of the second remote node to the host node with a second unique identification;

receiving a second ping reply message at the second remote node from the host node, the second ping reply message transmitted from the host node to the second remote node across the second distinct signal path coupling the second remote node to the host node;

determining, at the second remote node, whether the second ping reply message sent as a part of the process to determine signal delay uniquely identifies the second communication port of the second remote node with the second unique identification; and

when the second ping reply message uniquely identifies the second communication port of the second remote node, calculating a second round-trip time delay between sending the second ping initiation message and receiving the second ping reply message at the second remote node.

13. The method ofclaim 12, wherein the first unique identification is a path code that identifies a first path between the first communication port of the remote node and a third communication port of the host node.

14. The method ofclaim 13, wherein the path code uniquely identifies the host node, the first communication port, the third communication port, and the first distinct signal path between the host node and the first remote node.

15. The method ofclaim 12, further comprising:

calculating a first signal path delay at the first remote node based on the first round-trip time delay.

16. The method ofclaim 15, wherein calculating the first signal path delay includes:

dividing the first round-trip time delay by a number to determine a one-way delay between at least one of sending and receiving the first ping initiation message and sending and receiving the first ping reply message.

17. The method ofclaim 15, wherein calculating the first signal path delay includes:

factoring intrinsic processing delays into the calculation of the first signal path delay.

18. The method ofclaim 17, wherein the intrinsic processing delays are pre-determined processing delays associated with internal processing occurring at least one of the host node and the first remote node.

19. The method ofclaim 15, wherein the first signal path delay approximates at least one of:

a forward path time delay between radio frequency spectrum being received at a radio frequency port of the host node and being output at a radio frequency port of the first remote node; and

a reverse path time delay between radio frequency spectrum being received at the radio frequency port of the first remote node and being output at the radio frequency port of the host node.

20. The method ofclaim 12, further comprising forwarding the first ping initiation message received from the first remote node toward the host node at a third remote node positioned between the first remote node and the host node; and

forwarding the first ping reply message received from the host node toward the first remote node at the third remote node positioned between the first remote node and the host node.

21. The method ofclaim 12, wherein validating the first ping initiation message includes at least one of performing a cyclic redundancy check on the first ping initiation message, validating a message type, validating a host base station interface type, validating a host node ID number, and validating a host base station ID number.

22. The method ofclaim 12, further comprising:

determining, at the first remote node, whether the first ping reply message is received before a predefined timeout period elapses since the first ping initiation message was sent before determining whether the first ping reply message uniquely identifies the first communication port of the first remote node with the first unique identification; and

wherein determining whether the first ping reply message uniquely identifies the first communication port of the first remote node with the first unique identification only occurs when the first ping reply message is received before the predefined timeout period elapses since the first ping initiation message was sent;

when the first ping reply message is not received before the predefined timeout period elapses, determining whether a predefined number of unsuccessful attempts at sending the first ping initiation message has been reached;

when the predefined number of unsuccessful attempts at sending the first ping initiation message has been reached, resending the first ping initiation message when a next ping trigger occurs.

23. The method ofclaim 22, wherein the next ping trigger occurs at a pseudo-random time determined using a pseudo-random back-off algorithm to minimize the chance of a collision between other upstream messages.

24. The method ofclaim 12, further comprising:

determining, at the first remote node, whether the first ping reply message has been successfully received a predefined number of times; and

wherein calculating the first round-trip time delay between sending the first ping initiation message and receiving the first ping reply message at the first remote unit only occurs when the first ping reply message has been successfully received a predefined number of times; and

when the first ping reply message has not been successfully received a predefined number of times, resending the first ping initiation message when a next ping trigger occurs.

25. The method ofclaim 24, wherein the next ping trigger occurs at a pseudo-random time determined using a pseudo-random back-off algorithm to minimize the chance of a collision between other upstream messages.

26. The method ofclaim 12, further comprising:

when the first ping reply message received at the first remote node does not correspond to at least one communication port of the first remote node, ignoring the first ping reply message at the first remote node.

27. The method ofclaim 12, further comprising:

determining, at the first remote node, whether a predefined number of unsuccessful attempts at sending the first ping initiation message has been reached; and

when the predefined number of unsuccessful attempts at sending the first ping initiation message has been reached, reporting a path integrity alarm.

28. The method ofclaim 12, further comprising:

converting messages received from an antenna connected to the first remote node from first radio frequency signals to first digital signal; and

converting messages to be transmitted via the antenna from second digital signals to second radio frequency signals.

29. The method ofclaim 12, further comprising:

receiving the first ping initiation message at the host node;

validating the first ping initiation message at the host node; and

when the first ping initiation message is validated, sending the first ping reply message to the first remote node.

30. The method ofclaim 29, further comprising:

when a third initiation message received at the host node is not validated at the host node, ignoring the third initiation message.

31. The method ofclaim 29, further comprising:

converting messages received from an antenna connected to the host node from first radio frequency signals to first digital signals; and

converting messages to be transmitted via the antenna from second digital signals to second radio frequency signals.

32. The method ofclaim 12, wherein a single bit in each timeslot of a data frame is used to transmit the first ping initiation message and the first ping reply message.

33. The method ofclaim 12, further comprising:

after calculating the first round-trip time delay between sending the first ping initiation message and receiving the first ping reply message at the first remote node, resetting an attempts count and a message received count, wherein the attempts count tracks how many unsuccessful attempts have been made at pinging sending an initiation message to the host node and receiving a reply message from the host node, wherein the message received count tracks how many times the message has been successfully received.

34. The method ofclaim 12, further comprising:

waiting for a next ping trigger;

once the next ping trigger has occurred, sending a third ping initiation message from the first remote node to the host node, wherein the third ping initiation message uniquely identifies a third communication port of the first remote node to the host node with a third unique identification;

receiving a third ping reply message at the first remote node;

determining, at the first remote node, whether the third ping reply message uniquely identifies the third communication port of the first remote node with the third unique identification; and

when the third ping reply message uniquely identifies the third communication port of the first remote node, calculating a third round-trip time delay between sending the third ping initiation message and receiving the third ping reply message at the first remote node.

35. A plurality of remote nodes in a distributed antenna system comprising:

a first remote node having:

a first communication port communicatively coupled to a first antenna;

a second communication port communicatively coupled to a host node; and

a first remote node processor, wherein the first remote node processor comprises program instructions that:

cause the first remote node to send a first ping initiation message to the host node across a first communication link established across a first distinct signal path between the second communication port and the host node as part of a process to determine signal delay, wherein the first ping initiation message includes a first unique identification that uniquely identifies at least one of the first communication port and the second communication port of the first remote node to the host node;

cause the first remote node to determine whether a first ping reply message received sent as a part of the process to determine signal delay from the host node that is received from the first remote node corresponds to the at least one of the first communication port and the second communication port of the first remote node based on the first unique identification; and

when the first ping reply message received from the host node corresponds to the at least one of the first communication port and the second communication port, cause the first remote node to calculate the elapsed time between sending the first ping initiation message and receiving the first ping reply message;

a second remote node having:

a third communication port communicatively coupled to a second antenna;

a fourth communication port communicatively coupled to the host node; and

a second remote node processor, wherein the second remote node processor comprises program instructions that:

cause the second remote node to send a second ping initiation message to the host node across a second communication link established across a second distinct signal path between the fourth communication port and the host node as part of the process to determine signal delay, wherein the second ping initiation message includes a second unique identification that uniquely identifies at least one of the third communication port and the fourth communication port of the second remote node to the host node;

cause the second remote node to determine whether a second ping reply message received sent as a part of the process to determine signal delay from the host node that is received from the second remote node corresponds to the at least one of the third communication port and the fourth communication port of the second remote node based on the second unique identification; and

when the second ping reply message received from the host node corresponds to the at least one of the third communication port and the fourth communication port, cause the second remote node to calculate the elapsed time between sending the second ping initiation message and receiving the second ping reply message.

36. The plurality of remote nodes ofclaim 35, wherein the first unique identification is a path code that identifies a path between the at least one of the first communication port and the second communication port of the first remote node and at least one communication port of the host node.

37. The plurality of remote nodes ofclaim 36, wherein the path code uniquely identifies the host node, the at least one communication port of the host node, the at least one of the first communication port and the second communication port of the remote node, and the first distinct signal path between the host node and the first remote node.

38. The plurality of remote nodes ofclaim 35, wherein the first remote node is separated from the host node by at least one additional remote node in the distributed antenna system.

39. The plurality of remote nodes ofclaim 35, wherein the first communication port is part of a radio frequency to digital interface that converts between radio frequency signals and digital signals.

40. The plurality of remote nodes ofclaim 35, wherein a single bit in each timeslot of a data frame is used to transmit the first ping initiation message and the first ping reply message.

41. The plurality of remote nodes ofclaim 35, wherein the first remote node processor program instructions further cause the first remote node to:

verify whether the first communication port of the first remote node is compatible with a first type of at least one communication port of the host node based on the first ping reply message received from the host node.

42. The plurality of remote nodes ofclaim 41, wherein the first remote node processor program instructions further cause the first remote node to at least one of:

mute the first communication port of the first remote node when it is determined that the first communication port of the first remote node is not compatible with the first type of the at least one communication port of the host node; and

trigger an alarm to indicate a mismatch between the first type of the at least one communication port of the host node and the first communication port of the first remote node.

43. The plurality of remote nodes ofclaim 35, wherein at least one of the first remote node processor and the second remote node processor is at least one of a programmable processor, a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a field-programmable object array (FPOA), and a programmable logic device (PLD).

44. A program product comprising program instructions, embodied on a non-transitory storage medium, the program instructions cause at least one programmable processor in each of a plurality of remote nodes within a distributed antenna system to:

cause a particular remote node to send a ping initiation message to a host node across a communication link established across a distinct signal path between the remote node and the host node as part of a process to determine signal delay, wherein the ping initiation message includes a unique identification that uniquely identifies at least one communication port of the remote node to the host node, wherein the distinct signal path between the remote node and the host node is used for data communication;

cause the particular remote node to determine whether a ping reply message received as a part of the process to determine signal delay from the host node that is received from the particular remote node across the distinct signal path corresponds to the at least one communication port of the remote node based on the unique identification; and

when the ping reply message received from the host node corresponds to the at least one communication port of the remote node based on the unique identification, calculate the elapsed time between sending the ping initiation message and receiving the ping reply message.

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