US20050009506A1 - Communication system - Google Patents

Abstract

The present invention relates to methods and means for creating a cellular radio communication system (100) out of a number of local radio networks (109, 110), e.g. piconets. The local radio networks (109,110) are unsynchronised with each other and uses a radio interface that has no broadcast channel, e.g. the Bluetooth radio interface.

A control unit (108) is connected to each local radio network to provide the basic means and methods for a cellular radio communication system (100). Radio units (101-103) can attach and retain a connection to the control unit (108) via their respective radio node (104-107). The radio units (101-103) can also perform roaming, handover, measurments and fast connection set-ups in the system (100).

Description

TECHNICAL FIELD OF THE INVENTION
• The present invention relates in general to the field of radio communication and, in particular, to methods and means for providing a cellular radio communication system comprising a number of local radio networks utilising radio interfaces that are unsynchronised with each other and have no broadcast control channel.
DESCRIPTION OF RELATED ART
• There are a number of equipments that have some sort of radio communication means. By “radio unit” is meant all portable and non-portable equipment intended for radio communication with a radio communication system. Examples of such radio units are mobile phones, cordless phones, pagers, telex, electronic notebooks, PCs and laptops with integrated radios, communicators, computers, wireless head sets, wireless printers, wireless keyboards or any other electronic equipment using a radio link as a mean of communication. These equipments can be used with any type of radio communication system, such as cellular networks, satellite or small local radio networks. They can also communicate directly with each other without using any system.
• Cellular radio communication systems are commonly employed to provide voice and data communications to a plurality of radio units or subscribers.
• Examples of such cellular radio communication systems are e.g. AMPS, D-AMPS, GSM, and IS-95 (CDMA). These systems generally include a number of base stations serving portable radio units, one or more base station controllers (BSC) and at least one mobile switching centre (MSC) or similar. All radio transmissions in the system are made via a specific radio interface that enables radio communication between the portable radio units and the base stations.
• The cellular radio communication system covers a certain geographical area. This area is typically divided into cells or regions. A cell typically includes a base station and the radio units with which the base station is in communication. The cell associated with the particular base station with which a radio unit is communicating is commonly called the serving cell.
• To each cell one or more voice/data and/or traffic/control channels are allocated. Note that “channel” may refer to a specific carrier frequency in an analogue system, e.g. AMPS, a specific carrier/slot combination in a hybrid TDMA/FDMA system, e.g. GSM or one or more assigned codes in a DS-CDMA system.
• The cellular radio communication system usually provides a broadcast channel on which all radio units can listen to system information from base stations or measure signal strength and/or signal quality at regular intervals. Such a channel is called Broadcast Control Channel in GSM and Page or Access Channel in D-AMPS.
• The process of changing cells during a call is often called a handover or handoff. As soon as one of the neighbouring cells is considered to have a better signal strength/quality than the serving cell, e.g. by signal measurements on the broadcast channel, a handover is made to that particular neighbouring cell.
• The ability to move around, changing cells and connections over the radio interface when the radio unit is switched on or is in some kind of stand by mode but not engaged in a call is called roaming. When the radio unit is roaming it listens to the broadcast channel for information about the system e.g. in which specific area of the system the radio is presently located.
• Today, a number of low-power, low-cost radio interfaces between radio units and their accessories are being developed. The intention is to replace the cables or infrared links, e.g. between a computer and a printer, with a short-range radio link (a wireless link) forming a local radio network.
• A suitable frequency band for such a radio-interface is the 2,4 GHz ISM band (the Industrial-Scientific-Medical band) which ranges from 2,400-2,483 GHz in the US and Europe and from 2,471-2497 GHz in Japan. This frequency band is globally available, licence-free and open to any radio system.
• There are some rules each radio system has to follow if they are to use this ISM band, e.g. in the ETSI standard ETS 300328. Synchronisation between different transmitters in a radio system using the ISM band is not allowed. Synchronisation is of course allowed between a transmitter and a receiver, e.g. when two radio units are communicating with each other. Another rule specifies that frequency spreading must be used for a radio interface using the ISM band. The IEEE 802.11 is an example of a specification utilising the ISM band.
• An example of such a radio interface is called Bluetooth (see the Telecommunications Technology Journal “Ericsson Review”, No. 3 1998, with the article “BLUETOOTH-The universal radio interface for ad hoc, wireless connectivity” by Jaap Haartsen). Bluetooth is an universal radio interface operating within the ISM band and enables portable electronic devices to connect and communicate wirelessly via short-range, ad hoc networks (local radio networks). Bluetooth uses a frequency-hop spread spectrum technique (FH-CDMA) where the frequency band is divided into several hop channels. During a connection, radio units with Bluetooth transceivers hop from one channel to the other in a pseudo-random fashion. Each channel is divided into a number of slots in a time division multiplexing scheme, where a different hop frequency is used for each slot.
• A radio unit with Bluetooth can simultaneously communicate with up to seven other radio units in a small local radio network called a piconet. Each piconet is established by a unique frequency-hopping channel, i.e. all radio units in a specific piconet share the same frequency hopping scheme. One radio unit acts as a master, controlling the traffic in the piconet, and the other radio units in the piconet act as slaves. Any radio unit can become a master, but only one master may exist in a piconet at any time (often the one that initiates the connection). It is often the radio unit that initiates the connection that acts as a master. Any radio unit may change its role from slave to master or vice versa (a slave to master or a master to slave switch) Every radio unit in the piconet uses the master identity and realtime clock to track the hopping channel. Hence the slaves must be informed of the identity and the clock of the master before they can communicate with the master.
• Bluetooth supports both point-to-point (master to a slave) and point-to-multipoint (master to a number of slaves) connections. Two slaves can only communicate with each other through a master or by changing one of the slaves to a master with a slave to master switch.
• There is no hop or time synchronisation between radio units in different piconets but all radio units participating in the same piconet are hop synchronised to one frequency-hopping channel and time synchronised so that they can transmit or receive at the right time. This does not contravene the rules of non synchronisation between transmitters in the ISM band because there is only one radio unit that is transmitting at any time instant in the piconet.
• A radio unit can act as a slave in several piconets. This is achieved by using the time division multiplexing scheme of the channels where e.g. a first piconet is visited in a first time slot and a second piconet is visited in a third time slot. There are three different time slots on each channel where each time slot is split in two portions, one portion for transmitting and one portion for receiving.
• There is no broadcast channel (e.g. a Broadcast Control Channel in GSM) in Bluetooth to which radio units that are not connected to or have not been connected to a Bluetooth piconet can listen to system information, “find” a base station or to measure the signal strength/quality on.
• As Bluetooth is designed to replace cables or infrared links between different electronic equipments no roaming or handover support have been incorporated in the radio interface. As soon as a radio unit connected to a piconet is moved outside the radio coverage of the master, the radio unit loses its connection (the call).
SUMMARY
• A number of problems occur when local radio networks, utilising radio interfaces that are unsynchronised with each other and have no broadcast control channel, are to be connected into and used as a cellular radio communication system.
• A radio unit that is switched on in a local radio network can not be attached to the system with the help of a broadcast channel.
• A radio unit that has established a link to one local radio network can not reach or be reached from another local radio network.
• A radio unit can not roam or perform handover to a new local radio network when it is moved outside the local radio network it was first connected to.
• The system can not measure the signal strength/quality from and keep track of neighbouring local radio networks to be able to perform high quality roaming and handover.
• A radio node/base station from one local radio network can not establish a link with a radio unit in a neighbouring local radio network.
• In light of the foregoing, a primary object of the present invention is to provide methods and means for creating a cellular radio communication system out of a number of local radio networks, where each network utilises a radio interface that has no broadcast channel and is unsynchronised compared to the other radio interfaces in the system. E.g. methods and means for attaching a radio unit to the system, retaining the connection to the system and providing measuring, roaming and handover capabilities.
• According to a first aspect of the present invention there is a method for attaching a radio unit to a cellular radio communication system comprising a number of local radio networks utilising radio interfaces that are unsynchronised with each other.
• According to a second aspect of the present invention there is a method for retaining a connection to a radio unit in a cellular radio communication system comprising a number of local radio networks utilising radio interfaces that are unsynchronised with each other.
• According to a third aspect of the present invention there is a method for collecting data for a neighbouring list in a cellular radio communication system comprising a number of local radio networks utilising radio interfaces that are unsynchronised with each other.
• According to a fourth aspect of the present invention there is a method for calculating the realtime clock of a first radio node in a second radio node in a cellular radio communication system comprising a number of local radio networks utilising radio interfaces that are unsynchronised with each other.
• According to a fifth aspect of the present invention there is a method for co-ordinating the use of time slots in different local radio networks in a cellular radio communication system comprising a number of local radio networks utilising radio interfaces that are unsynchronised with each other.
• A system according to the present invention comprises a control unit connected with a number of local radio networks and providing the basic means of a cellular radio communication system.
• A control unit according to the present invention is connected with a number of local radio networks to provide the basic means for a cellular radio communication system.
• An advantage with the present invention is that it is possible to attach and retain a radio unit that is switched on in the cellular radio communication system with no broadcast channel.
• Another advantage is that it is possible to provide roaming and handover between local radio networks having radio interfaces that are unsynchronised with each other.
• Still another advantage is that it is possible for a radio node in one local radio network to make a contact with a radio unit in another neighbouring local radio network.
• Yet another advantage is that the signalling in the respective local radio network can be coordinated to facilitate inter local radio network communication.
• Still another advantage is that it is possible for the system to keep track of neighbouring local radio networks to each radio unit.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is illustrating a block diagram of a first embodiment of a cellular radio communication system according to the present invention
• FIG. 2 is illustrating a flow chart of a first method according to the present invention.
• FIG. 3 is illustrating a flow chart of a first embodiment of a second method according to the present invention.
• FIG. 4 is illustrating an example of a BRFP_candidates list according to the present invention.
• FIG. 5 is illustrating an example of a neighbouring list according to the present invention.
• FIG. 6 is illustrating a flow chart of a second embodiment of the second method according to the present invention.
• FIG. 7 is illustrating a flow chart of a first embodiment of a third method according to the present invention.
• FIGS. 8a-bare illustrating a block diagram of a paging scenario according to the present invention.
• FIG. 9 is illustrating a flow chart of a fourth method according to the present invention.
• FIG. 10 is illustrating a flow chart of a fifth method according to the present invention.
• FIG. 11ais illustrating uncoordinated timeslots in two local radio networks.
• FIG. 11bis illustrating co-ordinated time slots in two local radio networks according to the present invention.
• FIG. 12 is illustrating a block diagram of a second embodiment of a cellular radio communication system according to the present invention
• FIG. 13ais illustrating a schematic block diagram of a first embodiment of a control node according to the present invention.
• FIG. 13bis illustrating a schematic block diagram of a second embodiment of a control node according to the present invention.
• FIG. 14 is illustrating a schematic block diagram of a radio node according to the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
• As previously stated, the present invention relates to a cellular radio communication system comprising a number of local radio networks (piconets).
• FIG. 1 illustrates a block diagram of a first embodiment of a cellularradio communication system100 for utilising the present invention. Thesystem100 comprises a control-node (BCCFP)108 connected to four radio-nodes (BRFP)104-107 respectively. TheBRFP105 is serving two radio units (BPP)101,102 respectively and theBRFP107 is serving a radio unit (BPP)103. TheBRFP105 and the twoBPPs101,102 respectively utilises a radio interface, to enable communication between them, and forms a first piconet109 (a first local radio network). TheBRFP107 and theBPP103 utilises the same radio interface and forms a second piconet110 (a second local radio network). The radio interface used inpiconet109 is not synchronised with the radio interface used inpiconet110.
• The control-node108 may be connected to a PSTN (Public Switched Telephone Network) and/or a PLMN (Public Land Mobile Network) as illustrated by the dashedcloud112. The control-node108 can also be connected to other control-nodes so as to form a bigger cellular radio communication system than illustrated inFIG. 1. Thissystem100 will be described in more detail at the end of this description.
• FIG. 2 illustrates a flow chart of a first method according to the present invention for attaching theBPP101 to the cellularradio communication system100 inFIG. 1. Attaching a BPP means that the cellular system becomes aware of that a new radio unit is switched on in the system, where in the system the new radio unit is located, if the new radio unit is authorised to use the system and to registrate the new radio unit in the system.
• According to astep201, theBPP101 establishes a link with theBRFP105 so that it becomes a part of thefirst piconet109 inFIG. 1. The BPP scans for BRFPs within its radio coverage area, at regular intervals, by transmitting inquire signals (LC_INQUIRY) including the identity and the realtime clock of theBPP101. The BRFPs in radio range answers by transmitting acknowledge signals (LC_FHS_BRFP) including their identity and realtime clocks to theBPP101. TheBPP101 can then select one of these BRFPs, in thiscase BRFP105, and transmit a page signal (LC_PAGE) to the selected BRFP and establish the link. TheBPP101 assumes the role as a master and theBRFP105 takes the role as a slave. TheBRFP105 receives identification data fromBPP101, e.g. the IEEE-identity and/or if theradio unit101 is equipped with a SIM-card the IMSI identity. TheBRFP105 also receives information regarding the class of service provided by theBPP101, authentication, and as previously stated the realtime_clock of theBPP101 which is needed to calculate the frequency hopping sequence in theBRFP105.
• TheBPP101 makes the first contact, by the LC_INQUIRY, with theBRFP105 before it can detect any signal from theBRFP105. TheBRFP105 needs to know at least the identity of the BPP101 (received by the LC INQUIRY) to be able to transmit a signal that theBPP101 can detect. This is because that there is no broadcast control channel in the radio interface utilised in thesystem100.
• According to astep202, theBRFP105 performs a Bluetooth authentication (LMP_Bluetooth_Authentication). This is performed between the Bluetooth circuits in theBRFP105 and theBPP101 in a known way.
• According to step203, theBRFP105 forwards the information and the identification data received instep201 to theBCCFP108.
• According to step204, theBCCFP108 identifies theBPP101 by the identification data.
• According to step205, theBCCFP108 authenticates theBPP101. As an example, the known authentication technique used in GSM can be used for this authentication. The IEEE identity with additional authentication information can also be used.
• According to step206, theBCCFP108 registers the identity of theBPP101 in the system. This means that theBPP101 has established a connection with thesystem100 and is ready to receive incoming calls etc.
• According to astep207, theBRFP105 initiates a Master-Slave switch so that theBRFP105 becomes the master and theBPP101 becomes the slave.
• According to step208, theBRFP105 puts theBPP101 in a parked mode by transmitting a park command. This means that theBPP101 will terminate the link to theBRFP105 but still be active and listen for signals from the BRFP105 (the master) so that it can retain the link to theBRFP105 again. This means that if the maximum number of BPPs in a piconet is 7 and theBPP101 was the 7^thone a new BPP may not be able to connect to the piconet after theBPP101 is put in the parked mode.
• FIG. 3 illustrates a flow chart of a second method according to the present invention for retaining the connection to theBPP101 in the cellularradio communication system100 inFIG. 1 after theBPP101 has been attached to the system.
• According to astep301, the BRFP105 (the master) establishes a beacon signalling to the BPP101 (the slave) at evenly spaced time instants (beacon intervals). This means that theBPP101 receives signals from theBRFP105 at the beacon intervals.
• This beacon signal can as an example comprise parameters that activates a parked slave (e.g. a channel access code for the BPP101), re-synchronises parked slaves or allows certain slaves to access the channel. This signal can as an alternative also include information regarding how busy theBRFP105 is. The beacon signal is transmitted to a number of specific radio units, in this case theBPP101, and not to all radio units within radio range of the radio node as with a broadcast channel. The beacon signal is intended as a means for a master to retain the link to slaves that are not active in any transmissions and if needed to activate parked slaves (seestep208 above).
• If, according to astep302, theBPP101 is in a parked mode the method continues withstep303, otherwise it30 continues withstep304.
• According to astep303, theBRFP105 activates the parkedBPP101 by transmitting a page with the identity of theBPP101. This can be made at evenly spaced time instants.
• According to astep304, theBPP101 measures a signal parameter, e.g. the signal quality or signal strength, on the beacon signal fromBRFP105. TheBPP101 transmits this measurement to theBRFP105 in a result signal.
• According to astep305, theBRFP105 measures the signal parameter on one or more signals from theBPP101, e.g. the result signal instep304. TheBRFP105 forwards the measurements instep304 and305 to theBCCFP108 which stores them in a BRFP_candidates list. SeeFIG. 4 which illustrates an example of such a list. TheBRFP105 puts theBPP101 in parked mode again if theBPP101 where in a parked mode instep302.
• According to step306, theBCCFP108 checks if there is a neighbouring list for theBRFP105 stored in the BCCFP. If not, the method continues withstep701 according toFIG. 7 for creating such a list. The neighbouring list forBRFP105 comprises information of which additional BRFPs in the system that a BPP connected toBRFP105 inpiconet109 should be able to hear.FIG. 5 shows an example of such a neighbouring list forBRFP105 whereBRFP104 and106 are listed as neighbours.
• According to step307, theBCCFP108 orders theBRFPs104 and106 in the neighbouring list to page theBPP101, activate the BPP if needed, establish a beacon signalling and perform measurements according to step301-305. If a BRFP on the neighbouring list is unable to establish a link to the BPP101 (theBPP101 may temporarily be out of reach) it will continue to page theBPP101 as long as theBPP101 remains in thepiconet109 associated with theBRFP105. TheBRFPs104 and106 on the neighbouring list can page (reach) theBPP101 thanks to theBCCFP108 which distributes the identity of theBPP101 to the BRFPs.
• The threeBRFP104,105 and106 respectively will now have beacon signalling ongoing with theBPP101. TheBRFP104,106 respectively will measure one or more signal parameters, e.g. the signal quality and/or signal strength, from theBPP101 whenever they have free capacity for that. As an alternative, if theBPP101 is in a parked mode, one BRFP,e.g. BRFP105, can activate theBPP101, receive measurements from the BPP and deactivate the BPP within a short interval and the other BRFPs,e.g. BRFP104 and106, can do the same but within a longer interval to reduce the signalling within the system. If this is the case, the BPP may perform measurements on theBRFPs104 and106 at the same time as on theBRFP105 and transmit these measurements to theBRFP105 at the shorter intervals.
• FIG. 6 illustrates a flow chart of a second embodiment of the second method where the measurements instep304 and305 are made during an ongoing call. This means thatstep304 and305 according toFIG. 3 may be replaced by the following steps.
• According to astep601, theBRFP105 transmits information to theBCCFP108 regarding the exact clock information and hop sequence used for the call/link to theBPP101.
• According to astep602, theBCCFP108 forwards the information received instep601 to theBRFP104 and106, i.e. to all additional BRFPs on the neighbouring list forBRFP105.
• According to astep603, theBRFP104 and106 measures the signal strength and/or signal quality on the ongoing call between theBRFP105 and theBPP101, e.g. in a separate receiver in the BRFPs dedicated for monitoring (e.g. measuring).
• According to astep604, theBRFP104 and106 transmits the measured signal strength and/or signal quality to theBCCFP108 which stores these measurements in the BRFP_candidates list for theBRFP105.
• The steps601-604 may in a third embodiment of the second method (not illustrated) be used as a complement to step304 and305 instead of replacing them. This means that steps601-604 are performed after step607 inFIG. 3.
• If the link between theBPP101 and theBRFP105 becomes bad the second method may continue to perform roaming as the described below (not illustrated in any flow charts).
• The link roams fromBRFP105 to BRFP104 that, according to the BRFP_candidates list forBRFP105, has the best signal strength and/or signal quality for the moment (seeFIG. 4). This means that theBCCFP108 selects the new BRFP for roaming with the help of the BRFP_candidates list. This selection may as an alternative or as a complement be made on free capacity in the neighbouring BRFPs.
• If theBPP101 does not respond to any signalling from theBRFP104, e.g. a page signal, the second method may end by unregister theBPP101 as described below (not illustrated in any flow chart).
• TheBRFP104 transmits an unregistered message (UNREG) to theBCCFP108 regarding a link loss to theBPP101.
• TheBCCFP108 controls if any other BRFP,e.g. BRFP105 and106, have an ongoing beacon signalling to theBPP101. This is made e.g. by checking the BRFPs on the neighbouring list. TheBCCFP108 unregisters theBPP101 in the system (all links lost to BPP101) if no BRFP in the system has an ongoing beacon signalling to theBPP101.
• If a system initiated handover is to be performed, the second method may continue with a handover as described below (not illustrated).
• TheBCCFP108 selects a new BRFP from the neighbouring list of theBRFP104 and orders the selected BRFP, e.g. theBRFP105, to initiate a handover.
• If a BPP initiated handover is to be performed, the second method may continue with a handover as described below (not illustrated).
• TheBPP101 establishes a new link with theBRFP105 which, according to the BRFP_candidates list forBPP101, has the highest signal strength and/or signal quality.
• TheBRFP105 orders theBCCFP108 to route the call to theBRFP105. Hence bothBRFP104,105 respectively are connected to theBPP101 for a short moment.
• TheBRFP105 initiates a termination of the link from theBRFP104 to theBPP101 when the new link is established. This is made via theBCCFP108.
• FIG. 7 illustrates a flow chart of a third method according to the present invention for collecting data for a neighbouring list for the respective BRFP in the system used e.g. in the second method above. The collected data is used for creating and updating the neighbouring lists for the respective BRFP. As previously been stated, the neighbouring list for theBRFP105 comprises information of which additional BRFPs in the system that theBPP101 inpiconet109 can hear. This can e.g. be performed when a new system is run for the first time, when new BRFPs are added to the system, at specified intervals, or when one or several BRFPs are moved to a new location within the system.
• According to astep701, all BRFPs in thesystem100 transmits a page signal (LC_PAGE) to theBPP101, seeFIG. 8a. The BRFPs have been given the identity of theBPP101 from theBCCFP108 which also may initiate this step.
• According to astep702, theBPP101 transmits a response-signal (BRFP_same_time list) to theBRFP105. The response-signal comprises information regarding which BRFP theBPP101 can hear (e.g. detected a page signal from) at the same time and, as an alternative, also the signal strength on the detected page signal (LC_PAGE). This response signal may be transmitted each time a new BRFP has established beacon signalling with the BPP101 (e.g. in step307).
• According to astep703, theBRFP105 forwards the information received instep702 to theBCCFP108. TheBCCPF108 collects this information and creates the neighbouring list for theBRFP105 by registrating the BRFPs (except the BRFP105) that theBPP101 have heard instep702 as neighbours to theBRFP105 or if such a list already exists updates the neighbouring list accordingly. This can as an. example be made by adding “new” neighbouring BRFPs, included in the response signal (BRFP_same_time list) but not registrated in the neighbouring list, and deleting “old” neighbouring BRFPs, registrated in the neighbouring list but not included in the response signal. A delay may be used for the deletion of BRFPs in the neighbouring list to avoid deletion of BRFPs that are just temporarily out of reach for the page. As an example, a certain BRFP on the list must be excluded from two or more consecutive response signals received according to step702 before being removed from the neighbouring list.
• TheBCCFP108 can now direct signals to the BRFP serving a specific BPP in the system and its neighbouring BRFPs, e.g. for page signals, with the help of the neighbouring list which reduce the signalling within the system as seen inFIG. 8b. This improves the performance of the system.
• FIG. 9 illustrates a flow chart of a fourth method according to the present invention where the realtime clock of a BRFP in one piconet is calculated by a BRFP in another piconet, e.g. the realtime clock ofBRFP105 is calculated by the BRFP.106, seeFIG. 1. This method is preferably performed when more than one BRFP (from different piconets) have established a link with one and the same BPP. In the steps below both theBRFP105 and theBRFP106 in thesystem100 have established a link with theBPP102.
• According to astep901, theBRFP105 calculates a first realtime_clock difference value (Δ1_CLOCK) between theBPP102 and its own realtime_clock (clock_BPP₁₀₂−clock_BRFP₁₀₅).
• According to astep902, theBRFP105 transmits the calculated Δ1_CLOCK value to theBCCFP108 which stores it in a sync-list or as an alternative in the neighbouring list.
• According to astep903, theBRFP106 calculates a second realtime_clock difference value (Δ2_CLOCK) between theBPP102 and its own clock (Clock_BPP₁₀₂−Clock_BRFP₁₀₆).
• According to astep904, theBRFP106 transmits the calculated Δ2_CLOCK value to theBCCFP108 which stores it in the sync-list. As an alternative, theBCCFP108 can distribute Δ1_CLOCK and Δ2_CLOCK values to theBRFPs104,106 and107.
• According to step905, theBCCFP108 calculates the BRFP_realtime_clock difference value (Δ3_CLOCK) between theBRFP106 and the BRFP105 (Clock_BRFP₁₀₆−Clock_BRFP₁₀₅) according to the following equation:
  Δ3_CLOCK=Δ1_CLOCK−Δ2_CLOCK=[Clock_BPP₁₀₂−Clock_BRFP₁₀₅]−[Clock_BPP₁₀₂−Clock_BRFP₁₀₆]=−Clock_BRFP₁₀₅+Clock_BRFP₁₀₆=Clock_BRFP₁₀₆−Clock_BRFP₁₀₅
• The Δ3_CLOCK value is stored in the sync-list.
• If, according to astep906, the BCCFP wants theBRFP106 to establish a link to theBPP101 in the neighbouringpiconet109, e.g. establish beacon signalling according to step305, the method continues withstep907 below, otherwise it ends.
• According to step907, theBCCFP108 transmits the Δ3_CLOCK value to theBRFP106 and orders theBRFP106 to transmit an LC_PAGE to theBPP101.
• According to astep908, theBRFP106 calculates the realtime clock of the BRFP105 (Clock_BRFP₁₀₅) to which theBPP101 is listening, e.g. during park or active mode.
• Every BPP in a piconet uses the master clock (e.g. a BRFP clock) to track the common hopping channel in the piconet when the BPPs have assumed the roles as slaves. Hence if the master clock in a current piconet is known, the BPP in the current piconet can be easily reached from other BRFPs or BPPs outside the current piconet as long as they are within radio reach. The Clock_BRFP₁₀₅is calculated according to the following equation:
  Clock_BRFP₁₀₅=Δ3_CLOCK−Clock_BRFP₁₀₆=Clock_BRFP₁₀₆−Clock_BRFP₁₀₅−Clock_BRFP₁₀₆=Clock_BRFP₁₀₅
• According to step909, theBRFP106 transmits an LC_PAGE to theBPP101 and establishes a new link and a new piconet with theBPP101.
• The calculation instep905 can as an alternative be made in theBRFP106 as well as the calculation instep908 if theBCCFP108 transmits the information regarding the BRFP_realtime differences that is stored in the sync-list to theBRFP106.
• In short, all the BRFPs in the cellular radio communication system calculates the realtime_clock differences between the BPPs they are connected to and their own realtime clocks. The BRFPs transmits the realtime_clock differences to theBCCFP108 where they are used for calculating the BRFP_realtime_clock differences between each BRFP in the system. A first BRFP associated with a first piconet can then page a second BPP in a second piconet (e.g. to establish a new piconet) very accurately and quickly with the help of the BRFP realtime_clock difference as described instep908.
• FIG. 10 illustrates a flow chart of a fifth method according to the present invention for co-ordinating the use of timeslots in -each piconet associated with the cellular radio communication system. This method is preferably performed when a call is in progress on a link in a piconet and hence one available time slot is occupied.
• According to astep1001, the BRFPs104-107 in thesystem100 calculates the realtime_clock differences between the BPPs they are connected to and their own realtime clocks as instep901 and903 according toFIG. 9.
• According to a step1002, the BRFPs104-107 transmits the calculated realtime_clock differences to theBCCFP108, as instep902 and904 according toFIG. 9.
• According to astep1003, theBCCFP108 calculates the BRFP_realtime_clock differences between the BRFP104-107, as instep905 according toFIG. 9, from the realtime_clock differences received in step1002.
• According to astep1004, theBCCFP108 selects the realtime_clock ofBRFP104 as a reference clock (ref_clock) for all piconets in thesystem100. This can as an example be made by giving the first slot fromBRFP104 the time value 0 whereby the other BRFPs are given an offset value according to their BRFP_realtime_clock difference withBRFP104 which are e.g. added to or subtracted from their own realtime clocks.
• According to astep1005, theBCCFP108 orders all BRFPs in thesystem100 to use, as long as possible, a time slot co-ordinated with the ref_clock for signalling and payload to their respective BPP.
• This means that the signalling in thesystem100 can be made more effective by increasing the probabilities of a fast connection set-up between BPPs and BRFP in different piconets, since blocked time slots (blind_spots) will be more rare. Further on the total system capacity will increase.
• FIG. 11aillustrates uncoordinated traffic and signalling inpiconet109 and107 insystem100. There are three timeslots, each with a transmit portion and a receive portion, on the hopping channel in each piconet that the BPPs and BRFPs can use.BRFP105 andBPP101 communicates on the first timeslot and BRFP105 andBPP102 communicates on the second timeslot inpiconet109, which means that the third timeslot inpiconet109 is free.BRFP107 andBPP103 communicates on the third timeslot inpiconet110, which means that the first and second timeslot inpiconet110 are free. IfBRFP107 wants topage BPP102 inpiconet109, theBRFP107 has to use the first or second timeslot in piconet110 (the free ones) but the corresponding timeslots inpiconet109 are not free. This means that theBRFP107 can not reach theBPP102 right know and have to wait until the communication on the first or second timeslot inpiconet109 stops. Hence twoblind_spots1101 and1102 have occurred.
• FIG. 11billustrates the same traffic and signalling as inFIG. 11abut co-ordinated according to the fifth method (FIG. 10). The realtime clock of theBRFP105 is selected as the ref_clock and theBRFP107 has co-ordinated its traffic toBPP103 accordingly so that theBPP102 can be reach by a page P from theBRFP107 in the third timeslot. The third timeslot inBPP102 is synchronised with the third timeslot inBRFP107 by introducing asmall pause1103 between the second and third timeslot inBPP102. This means that a part of the space where the next timeslot in BPP102 (the first one due to the three time slot scheme) where to be put is used for the third timeslot. The first timeslot can therefore not be used for the moment. As seen inFIG. 11bthe BRFPs in the respective piconet are still not synchronised to each other.
• The inventive methods according toFIGS. 2, 3,6,7,9 and10 can be completely or partially implemented as software in at least one microprocessor.
• As previously been described,FIG. 1 illustrates a block diagram of a first embodiment of a cellularradio communication system100 for utilising the present invention. The BRFPs inFIG. 1 are connected to theBCCFP108 via a local area network (LAN)111.
• FIG. 12 illustrates an alternative connection where each BRFP is circuit switched connected to aswitch1201, preferably arranged in theBCCFP108, via dedicated transmission lines. The BRFPs can as another alternative be connected to theBCCFP108 via one or more radio links, e.g. a radio-LAN or wireless-LAN (WLAN).
• Each BRFP and BPP comprises at least one Bluetooth circuit/chip for utilising the radio communication over the Bluetooth radio interface. The Bluetooth radio interface is one example of a radio interface utilised in small short range local radio network. Other radio interfaces with similar characteristics may also be used.
• Thesystem100 can as an example be an indoor cellular radio communication system where thefirst piconet109 is situated in a first room and thesecond piconet110 is situated in a second room. The BRFPs1.05 and107 can as an example be personal computers (PCs) with means for radio communication and connected to theLAN111. TheBPP101 can as an example be a cordless phone, the BPP102 a laptop with means for radio communication and the BPP103 a printer with means for radio communication. TheBRFP106 may be a phone situated in a third room and connected to the LAN by wire. If theBPP101 is moved to the third room theBRFP106 and theBPP101 establishes a connection and hence forms a new (third) piconet.
• A complete cellular radio communication system needs to have some basic functionality's to work and reach an acceptable system behaviour. Those are described in the methods according toFIGS. 2, 3,6,7,9 and10.
• All these basic functionality's are provided in the cellularradio communication system100 according to the present invention. This is achieved by the BCCFP108 (the control node) connected to all BRFPs in thesystem100.
• FIG. 13aillustrates a schematic block diagram of a first embodiment of a BCCFP1301 (control node) according to the present-invention. TheBCCFP1301 comprises a processor with amemory1302, ahard disk1303 and anetwork interface1304 connected to each other by acomputer bus1305. The processor with the memory is e.g. used for creating and updating the neighbouring lists and calculating realtime clock differences. The hard disk is e.g. used for storing the neighbouring lists, realtime clock and identity information. Thenetwork interface1304 is used for connecting the BCCFP to the BRFPs via aLAN1306. All voice and data traffic is separated from the BCCFP in this embodiment and hence processed by a separate voice/data unit1307 connected to theLAN1306.
• FIG. 13billustrates a schematic block diagram of a second embodiment of aBCCFP1308 according to the present invention where the voice/data unit1307 is integrated in theBCCFP1308. The voice/data unit1307 comprises a voice codec and means for conversion between circuit switched and packet switched information.
• FIG. 14 illustrates a schematic block diagram of a BRFP1401 (radio node) according to the present invention. The BRFP comprises a processor with a RAM memory and aflash memory1402, a bluetooth radio interface chip/unit1403 and a network orserial communication interface1404 connected to each other by acomputer bus1405. The processor with the RAM memory and flash memory is e.g. used for processing and distributing realtime clock information. The bluetooth radio interface chip/unit has previously been described. The network interface is used for connecting the BRFP to a LAN according toFIG. 1 and the serial communication interface is used if the BRFP is circuit switched connected according toFIG. 12.

Claims (20)

1-13. (Canceled)

14. A method for calculating the realtime clock of a first radio node in a second radio node in a cellular radio communication system comprising a number of local radio networks utilizing radio interfaces which, between said local radio networks are unsynchronized with each other, where each of said local radio networks comprises a radio node arranged to communicate with a plurality of radio units comprising:

establishing a link between a first radio unit and both of said first and second radio nodes:

generating a first BRFP realtime clock difference between the realtime clocks of said first radio node and said second radio node in a control node associated with said radio nodes;

transmitting said first BRFP realtime clock difference to said second radio node; and

calculating the real time clock of said first radio node in said second radio node by adding said first BRFP realtime clock difference to the realtime clock of said second radio node.

15. The method as claimed inclaim 14, wherein said step of generating a first BRFP realtime clock difference comprises the steps of:

calculating a first realtime clock difference between said first radio unit and said first radio node in said first radio node;

transmitting said first realtime clock difference to said control node;

calculating a second realtime clock difference between said first radio unit and said second radio node in said second radio node;

transmitting said second realtime clock difference to said control node;

calculating said first BRFP realtime clock difference in said control unit from said first and second realtime clock difference.

16. The method as claimed inclaim 14, wherein said step of calculating the realtime clock of said first radio node in said second radio node is followed by the step of:

paging a second radio unit from said second radio node, where said second radio unit has established a link to said first radio node.

17. A method for co-ordinating the use of time slots in different local radio networks in a cellular radio communication system comprising a number of local radio networks utilizing radio interfaces which, between said local radio networks, are unsynchronized with each other and having at least three timeslots, and where each of said local radio networks comprises a radio node arranged to communicate with a plurality of radio units the method comprising:

generating a BRFP realtime clock difference between all the realtime clocks of said radio nodes in said system in a control node associated with said radio nodes;

selecting the realtime clock of a first one of said radio nodes as a reference clock for all radio nodes in said system;

ordering all radio nodes in said system to use timeslots co-ordinated with said reference clock of said first radio node for signalling and payload by using said BRFP realtime clock differences.

18. The method as claimed inclaim 17, wherein said step of generating a BRFP realtime clock difference between all the realtime clocks of said radio nodes comprises the steps of:

calculating realtime clock differences in all radio nodes between their own realtime clocks and said radio units which they are connected too;

transmitting said realtime clock differences to said control node;

calculating said BRFP realtime clock difference from said calculated realtime clock difference in said control node.

19-24. (Canceled)

25. A control node in a cellular radio communication system comprising a number of local radio networks utilizing radio interfaces which, between said local radio networks are unsynchronized with each other, and where each of said local radio networks comprises a radio node arranged to communicate with a plurality of radio units, characterised in that said control node is connected to at least one radio node in each local radio network in said system so as to create a cellular radio communication system out of said local radio networks, and where said control node is arranged to control the communication in each of said local radio networks.

26. The control node as claimed inclaim 25, wherein said control node comprises means for establishing a connection from each one of said radio nodes to said control-node.

27. The control node as claimed inclaim 25, wherein said control node comprises means for identifying, authenticating and registrating each one of said radio units so that said control node can direct calls to and from said radio units.

28. The control node as claimed inclaim 25, wherein said control node comprises means for roaming links to radio units between said radio nodes in said system.

29. The control node as claimed inclaim 25, wherein said control node comprises means for performing handovers of connections to said radio units between said radio nodes in said system.

30. The control node as claimed inclaim 25, wherein said control node comprises means for generating a BRFP realtime clock difference between all the realtime clocks of said radio nodes in said system.

31. The control node as claimed inclaim 25, wherein said control node comprises:

means for selecting the realtime clock of a first one of said radio nodes as a reference clock for all radio nodes in the system; and

means for ordering all radio nodes in said system to use timeslots coordinated with said reference clock of said first radio node for signalling and payload.

32. The control node as claimed inclaim 25, wherein said control node comprises:

means for creating a neighbouring list by registrating said radio nodes from which said first radio unit can detect a signal as neighbours to said first radio node.

33. A control node, comprising:

a processor,

a memory in communication with the processor, wherein the memory includes instructions for calculating the realtime clock of a first radio node in a second radio node in a cellular radio communication system comprising a number of local radio networks utilizing radio interfaces which, between said local radio networks, are unsynchronized with each other, where each of said local radio networks comprises a radio node arranged to communicate with a plurality of radio units,

wherein the calculating instructions comprise instructions for:

establishing a link between a first radio unit and both of said first and second radio nodes:

generating a first BRFP realtime clock difference between the realtime clocks of said first radio node and said second radio node in a control node associated with said radio nodes;

transmitting said first BRFP realtime clock difference to said second radio node; and

calculating the real time clock of said first radio node in said second radio node by adding said first BRFP realtime clock difference to the realtime clock of said second radio node.

34. The node ofclaim 33, wherein the instructions for generating a first BRFP realtime clock difference further comprises instructions for:

calculating a first realtime clock difference between said first radio unit and said first radio node in said first radio node;

transmitting said first realtime clock difference to said control node;

calculating a second realtime clock difference between said first radio unit and said second radio node in said second radio node;

transmitting said second realtime clock difference to said control node; and

calculating said first BRFP realtime clock difference in said control unit from said first and second realtime clock difference.

35. The node ofclaim 33, wherein the instructions for calculating the realtime clock of said first radio node in said second radio node also contains instructions for paging a second radio unit from said second radio node, where said second radio unit has established a link to said first radio node.

36. A control node comprising:

a processor,

a memory in communication with the processor, wherein the memory includes instructions coordinating the use of time slots in different local radio networks in a cellular radio communication system comprising a number of local radio networks utilizing radio interfaces which, between said local radio networks, are unsynchronized with each other and having at least three timeslots, and where each of said local radio networks comprises a radio node arranged to communicate with a plurality of radio units, wherein the instructions for coordinating comprise instructions for:

generating a BRFP realtime clock difference between all the realtime clocks of said radio nodes in said system in a control node associated with said radio nodes;

selecting the realtime clock of a first one of said radio nodes as a reference clock for all radio nodes in said system; and

ordering all radio nodes in said system to use timeslots coordinated with said reference clock of said first radio node for signaling and payload by using said BRFP realtime clock differences.

37. The node ofclaim 36, wherein the instructions for generating a BRFP realtime clock difference between all the realtime clocks of said radio nodes comprises instructions for:

calculating realtime clock differences in all radio nodes between their own realtime clocks and said radio units which they are connected too;

transmitting said realtime clock differences to said control node; and

calculating said BRFP realtime clock difference from said calculated realtime clock difference in said control node.

Images