GB2396525A

GB2396525A - A communication system and method of idle state support therefor

Info

Publication number: GB2396525A
Application number: GB0229425A
Authority: GB
Inventors: Paul Mcdonald
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2002-12-17
Filing date: 2002-12-17
Publication date: 2004-06-23
Anticipated expiration: 2022-12-17
Also published as: AU2003298346A1; GB0229425D0; WO2004056143A3; EP1574094A2; AU2003298346A8; WO2004056143A2; GB2396525B; CN1726730A

Abstract

The invention relates to support of communication units (219, 221) in a communication system. One or more idle state communication units (219, 221) enter a quiescent state of reduced idle state functionality. The quiescent state communication units (219, 221) communicate with a supporting communication unit (217) over a short range air interface, typically, bluetooth (RTM) (223, 225). The supporting communication unit (217) communicates with the fixed network of the communication system through a serving base station (109). The supporting communication unit (217) supports the quiescent state communication units (219, 221) by communicating with the fixed network to perform idle state management functionality associated with the quiescent state communication unit (219, 221). Specifically, the supporting communication unit (217) communicates with a proxy processor (307), which performs a suitable interface to the communication system. The invention is particularly applicable to GSM and UMTS communication networks.

Description

1 2396525

A COMMUNICATION SYSTEM AND METHOD OF IDLE STATE

SUPPORT THEREFOR

5 Field of the invention

The invention relates to a communication system and method of idle state support therefor and in particular to support of communication units of a cellular communication system in a reduced functionality quiescent state.

Background of the Invention

FIG. 1 illustrates the principle of a conventional cellular communication 15 system 100 in accordance with prior art. A geographical region is divided

into a number of cells 101, 103, 105, 107 each of which is served by base station 109, 111, 113, 115. The base stations are interconnected by a fixed network which can communicate data between the base stations 101, 103, 105, 107. A mobile station is served via a radio communication link by the 20 base station of the cell within which the mobile station is situated. In the example if FIG. 1, mobile station 117 is served by base station 109 over radio link 119, mobile station 121 is served by base station 111 over radio link 123 and so on.

25 As a mobile station moves, it may move from the coverage of one base station to the coverage of another, i.e. from one cell to another. For example mobile station 125 is initially served by base station 113 over radio link 127. As it moves towards base station 115 it enters a region of overlapping coverage of the two base stations 111 and 113 and within this 30 overlap region it changes to be supported by base station 115 over radio link 129. As the mobile station 125 moves further into cell 107, it

continues to be supported by base station 115. This is known as a handover or handoff of a mobile station between cells.

A typical cellular communication system extends coverage over typically 5 an entire country and comprises hundred or even thousands of cells supporting thousands or even millions of mobile stations. Communication from a mobile station to a base station is known as uplink, and communication from a base station to a mobile station is known as downlink. The fixed network interconnecting the base stations is operable to route data between any two base stations, thereby enabling a mobile station in a cell to communicate with a mobile station in any other cell. In addition the fixed network comprises gateway functions for interconnecting to external l5 networks such as the Public Switched Telephone Network (PSTN), thereby allowing mobile stations to communicate with landline telephones and other communication terminals connected by a landline. Furthermore, the fixed network comprises much of the functionality required for managing a conventional cellular communication network including 20 functionality for routing data, admission control, resource allocation, subscriber billing, mobile station authentication etc. Currently the most ubiquitous cellular communication system is the 2nd generation communication system known as the Global System for Mobile 25 communication (GSM). GSM uses a technology known as Time Division Multiple Access (TDMA) wherein user separation is achieved by dividing frequency carriers into 8 discrete time slots, which individually can be allocated to a user. A base station may be allocated a single carrier or a multiple of carriers. One carrier is used for a pilot signal which further 30 contains broadcast information. This carrier is used by mobile stations for measuring of the signal level of transmissions from different base stations, and the obtained information is used for determining a suitable serving

cell during initial access or handovers. Further description of the GSM

TDMA communication system can be found in 'The GSM System for Mobile Communications' by Michel Mouly and Marie Bernadette Pautet, Bay Foreign Language Books, 1992, ISBN 2950719007.

Currently, 3rd generation systems are being rolled out to further enhance the communication services provided to mobile users. The most widely adopted 3rd generation communication systems are based on Code Division Multiple Access (CDMA) wherein user separation is obtained by allocating lo different spreading and scrambling codes to different users on the same carrier frequency. The transmissions are spread by multiplication with the allocated codes thereby causing the signal to be spread over a wide bandwidth. At the receiver, the codes are used to de-spread the received signal thereby regenerating the original signal. Each base station has a 15 code dedicated for a pilot and broadcast signal, and as for GSM this is used for measurements of multiple cells in order to determine a serving cell. An example of a communication system using this principle is the Universal Mobile Telecommunication System (UMTS), which is currently being deployed. Further description of CDMA and specifically of the

20 Wideband CDMA (WCDMA) mode of UMTS can be found in'WCDMA for UMTS', Harri Holma (editor), Antti Toskala (Editor), Wiley & Sons, 2001, ISBN 0471486876.

In contrast to conventional fixed telephone communication systems, the 25 mobile stations of a mobile communication system typically do not have a permanent and unlimited available power source. Rather, a conventional mobile station receives power from a small rechargeable battery pack.

Such battery packs need to be recharged at regular intervals, which provides a significant inconvenience to the user. Additionally, the user 30 risks that the battery of the mobile station may discharge thereby preventing normal operation of the mobile station. This may prevent the user from both receiving and making calls. Consequently, one of the main

parameters for a mobile station for use in a cellular communication system is the battery life between recharging, typically measured as a number of operational hours of the mobile station in different operating modes. Contrary to conventional telephones, a mobile station is not completely inactive when not involved in a call. Rather, when a mobile station is switched on but not participating in a call, it is in what is known as an idle state. During this idle state, the telephone performs a number of functions 10 including monitoring for paging messages indicating an incoming call, performing location updates and measuring signal strengths of surrounding base stations. The latter two functions support mobility management for the mobile station in idle state, allowing the user to move between cells.

The idle state thus supports the mobility of a user when not in a call.

However, a significant disadvantage of the idle state is that the functionality requires significant parts of the mobile station to be powered up thereby consuming power. A number of different techniques have been 20 developed in order to reduce power consumption in both the idle and active state. However, this reduction in power consumption has been offset by a desire to continually reduce the size of mobile stations and consequently the size of the battery packs. Therefore, battery life is still significantly limited. Furthermore, with the introduction of new 3rd

25 generation networks, such as UMTS, and wireless local area networking systems, new multimode wireless handsets are beginning to appear that can work with more than one type of network system. These multimode terminals may have to perform idle state monitoring of several of these network systems simultaneously thereby increasing the power demands 30 on the battery during the idle state.

s Hence, an improved system for reducing power consumption and increasing battery life would be a significant advantage.

5 Summary of the Invention

Accordingly, the Invention seeks to mitigate, alleviate or eliminate one or more of the above mentioned disadvantages singly or in any combination 10 According to a first aspect of the invention, there is provided a communication system comprising a fixed network supporting a plurality of communication units; the communication system comprising: a first communication unit operable to enter a quiescent state; and a second communication unit operable to enter a support state wherein the second 15 communication unit supports the first communication unit in the quiescent state by communicating with the fixed network to perform idle state management functionality associated with the first communication unit. 20 This provides for the significant advantage of allowing the first communication unit to perform only a reduced functionality during the quiescent state thereby allowing for a reduced power consumption and increased battery life. Specifically, the first communication unit may power down unused circuitry and/or operate circuitry in reduced resource 25 consumption states, for example by running processors of the communication unit at lower frequencies.

Preferably, the communication system is a cellular communication system.

30 According to another feature of the invention, the fixed network comprises a proxy processor operable to provide an interface between the fixed network and the second communication unit when operating in the

support state such as to provide an idle state management interface to the fixed network for the first communication unit.

The proxy processor may for example be provided as a functionality 5 embedded in an existing network element or may be a separate or distributed element. The proxy processor can provide the advantage of providing the interface to the communication system by which the first communication unit can be supported by the second communication unit.

Thus, the existing functionality of the communication system need not be 10 affected by the first communication unit being supported by the second communication unit. In this way, a standard communication system can easily be modified to provide the advantages of the invention simply by adding an additional proxy processor.

15 According to another feature of the invention, the proxy processor is operable to intercept messages from the fixed network addressed to the first communication unit and to communicate the intercepted messages to the second communication unit.

20 Hence, the invention allows for messages addressed to the first communication unit to be detected and redirected to the second communication unit by the proxy detector. Hence, other elements of the communication system may operate independently of and without any knowledge of whether the first communication unit is in an idle state or a 25 further reduced quiescent state, wherein it is supported by the second communication unit. This significantly facilitates implementation of a first communication unit being supported by a second communication unit in a communication system as it allows that only one or some network elements are operable to support this functionality.

According to another feature of the invention, the intercepted messages comprise a call activation message. This allows for the advantage that a

call can be initiated without consideration of whether the called party is in an idle state or a quiescent state. It allows for the first communication unit to be activated from the quiescent state when called, as the activation can be provided to the first communication unit through the proxy server 5 and the second communication unit.

According to another feature of the invention, the second communication unit comprises a measurement unit for performing idle state radio environment measurements for the first communication unit when in the 10 quiescent state. Hence, the second communication unit may perform some or all of the measurements required by the first communication unit in the idle state. The second communication unit may communicate the measurements to the first communication unit for further processing.

Alternatively or additionally, the second communication unit may 15 communicate the measurements to the fixed network for further processing. Hence, the first communication unit may further reduce the power consumption and may specifically power down measurement circuitry required by the first communication unit in an unsupported idle state. According to another feature of the invention, each of the first and second communication units comprises a short range wireless communication element operable to establish a short range communication link between the first and second communication unit. This allows for communication to 25 be exchanged between the first and second communication unit without having to communicate through the communication system. As the communication is short range highly efficient communication can be used with specifically low transmission powers and thus low power consumption. According to another feature of the invention, the first communication unit in the quiescent state is operable only to communicate on the short

range communication link. This allows for the power consumption of the first communication unit to be reduced. Also, communication only over short range communication links ensures that the fist and second communication units are relatively close and therefore increases 5 probability that any characteristics such as propagation characteristics determined for the second communication unit will be highly correlated with the corresponding characteristics of the first communication unit.

According to another feature of the invention, the second communication 10 unit is operable to enter the support state in response to a support request message received from the first communication unit over the short range communication link. This allows for the advantage of the first communication unit being able to control whether to enter the quiescent state or not. It furthermore allows for the first communication unit to IS monitor for suitable communication units that may be used as supporting communication units, and to request support from any suitable communication units found.

According to another feature of the invention, idle state control plane 20 messages associated with the first communication unit are communicated over the short range communication link. This provides for a low power consumption and highly reliable link to be used for maintaining the first communication unit in a quiescent state while being supported as an idle state mobile. It furthermore provides for the first communication unit to 25 have information of the processing in the fixed network as well as to respond to or issue suitable control messages.

According to another feature of the invention, idle state call management messages associated with the first communication unit are communicated 30 over the short range communication link. This allows for the first communication unit to be an active part of the call management while remaining in the quiescent state.

According to another feature of the invention, idle state mobility management messages associated with the first communication unit are communicated over the short range communication link. This allows for 5 the first communication unit to be an active part of the communication system while remaining in the quiescent state.

According to another feature of the invention, the first communication unit is operable to transmit control messages over the short range 10 communication link, and the second communication unit is operable to operate in response to the control messages of the first communication unit. This allows for the second communication unit to perform functions requested and/or controlled by the first communication unit. It also allows for messages and requests to be communicated to the fixed network at the 15 instigation of the first communication unit.

According to another feature of the invention, the second communication unit is operable to, upon receiving a call activation message for the first communication unit, forwarding the call activation message to the first 20 communication unit over the short range communication link, and the first communication unit is operable to exit the quiescent state upon receiving the call activation message. This provides an efficient and easy to implement system for returning the first communication unit to an active state from the quiescent state.

According to another feature of the invention, the idle state management functionality associated with the first communication unit comprises performing location updates. Hence, advantageously mobility management through location updates is possible for the first 30 communication unit when in the quiescent state.

According to another feature of the invention, the first communication unit is operable to power down an air interface communication element for the communication system when in the quiescent state. This provides the advantage of allowing for the power consumption of the first 5 communication unit to be reduced significantly when in the quiescent state. According to another feature of the invention, the second communication unit, when in the support state, is operable to support a plurality of 10 communication units in a quiescent state. Advantageously, a single communication unit is preferably operable to support a number of communication units in a quiescent state. Preferably, the power consumption of a number of communication units is therefore reduced.

Further, a number of functions, such as idle state measurements, will be 15 common for a plurality of communication units located within a sufficiently short range, and therefore an overall reduction in power consumption and complexity may be achieved by performing these functions centrally.

20 According to another feature of the invention, the fixed network may comprise a plurality of sub-networks and the first and second communication unit may be associated with different sub-networks. This provides the advantage that the quiescent state of the first communication unit may be supported by a second communication unit of a second 25 network thereby increasing the number of available communication units that may be used as support communication units. Further, it will frequently occur that the same user carries different communication units for accessing different communication networks and therefore a single user can use one of his communication units to support the other thereby 30 saving battery life. The different sub-networks may for example be a 3rd Generation network and a 2nd Generation network and more specifically a

first sub-network may be a UMTS network and a second sub-network may be a GSM network.

According to a different feature of the invention, the proxy processor is 5 external to a first sub-network associated with the first communication unit, and the first sub-network is operatively coupled to the proxy processor through a gateway of the first sub-network. This provides for an easy implementation as an external unit can be added to existing networks to allow for support of communication units in a quiescent state.

According to another feature of the invention, the second communication unit is operable to enter a quiescent state; and the first communication unit is operable to enter a support state wherein the first communication unit supports the second communication unit in the quiescent state by 15 communicating with the fixed network to perform idle state management functionality associated with the first communication unit; and wherein the first and second communication unit alternate between being in the quiescent state and the support state.

20 Preferably, a number of communication units in close proximity may take turns to act on behalf of the others units which enter the quiescent state.

From time to time, the supporting communication unit will offer the other units a chance to come out of the quiescent state and take over on behalf of the group. This allows for the power consumption associated with acting 25 as a supporting communication unit to be distributed over a plurality of communication units.

According to a second aspect of the invention, there is provided a communication unit for a communication system having a fixed network 30 supporting a plurality of communication units including at least a first communication unit operable to enter a quiescent state; the communication unit comprising: means for entering a support state

wherein the communication unit supports the first communication unit in the quiescent state by communicating with the fixed network to perform idle state management functionality associated with the first communication unit.

According to a third aspect of the invention, there is provided a method of idle state support for a communication system comprising a fixed network supporting a plurality of communication units; the method comprising the steps of entering a first communication unit into a quiescent state; and 10 entering a second communication unit into a support state wherein the second communication unit supports the first communication unit in the quiescent state by communicating with the fixed network to perform idle state management functionality associated with the first communication unit. Brief Description of the Drawings

An embodiment of the invention will be described, by way of example only, 20 with reference to the drawings, in which FIG. 1 is an illustration of a cellular communication system in accordance with the prior art;

25 FIG. 2 is an illustration of a communication system in accordance with an embodiment of the invention; and FIG. 3 is an illustration of a fixed network of a cellular communication system in accordance with an embodiment of the invention.

Detailed Description of a Preferred Embodiment of the Invention

The following description focuses on an embodiment for a GSM and/or

UMTS cellular communication system but it will be apparent that the invention is not limited to this application but may be applicable to many 5 other communication systems.

FIG. 2 is an illustration of a communication system in accordance with an embodiment of the invention. A fixed network comprises a plurality of base stations 209, 211, 213, 215 each defining a cell 201, 203, 205, 207.

lO The fixed network further comprises other network elements (not shown) required or desired for the operation of a cellular communication system including network elements for connecting base stations, interfacing to other communication systems, and operating and managing the communication system. For a UMTS communication system, these 15 elements include Radio Network Controllers (RNCs), Mobile Switch Centres (MSCs) and possibly Serving or Gateway GPRS Support nodes (SGSNs and GGSNs). A GSM fixed network typically comprises a number of Base Station Controllers (BSCs), MSCs and possibly SGSNs and GGSNs. In the example shown in FIG. 2, one cell 201 comprises three communication units 217, 219, 221 supported by the base station 209 of the cell 201. In the preferred embodiment, a communication unit may be any communication unit having functionality for communicating with a 25 cellular communication system. A communication unit may thus typically be a wireless user equipment, a mobile station, a communication terminal, a personal digital assistant, a laptop computer, an embedded communication processor, or any communication element having individual means for communicating over the cellular air interface.

30 1 None of the communication units 217, 219, 221 of FIG. 2 is currently actively involved in a call. In a conventional cellular communication

system, the communication units 217, 219, 221 would be in an idle state.

In the idle state, the communication units are not communicating any user data with the fixed network. However, communication units in idle state are registered on the fixed network such that the fixed network is 5 aware of the availability of the communication units. Typically, the fixed network further operates mobility management of communication units in an idle state. In UMTS and GSM, this includes location updates wherein information held in the fixed network relating to the location of the communication units is updated to reflect that a communication unit has 10 moved. The location information is typically not a specific geographical location, but rather information related to which cell the communication unit is in, and thus which base station it is supported by.

In communication systems such as GSM and UMTS, a communication 15 unit in idle state further performs a number of operations including: The communication unit periodically monitors the broadcast and paging channels of the base station it is currently attached to.

The communication unit also scans for the broadcast channels of 20 other base stations and decodes identification information of the detected base stations. It furthermore performs measurements of the link quality of these received base station signals.

Should the communication unit decide that one of these other base stations transmits a better quality signal than the one it is 25 currently monitoring, then it will switch to monitoring this new base stations without signalling to the network.

If the communication unit discovers that the location identity of the base station it is now monitoring is different to the one it is currently registered with, it will perform a location update to tell 30 the network it has moved location area.

In multimode systems, such as GSM/UMTS, the communication unit will also camp on one of the systems. If the link quality to the

camped on system degrades sufficiently, and there are no alternative base stations around for that system, the communication unit may switch to another base station technology and camp on that system. This will require communication with the 5 fixed network.

Hence, one of the functions of a UMTS or GSM communication unit in an idle state is to monitor a paging channel. Paging messages on this channel are decoded to detect if the paging message is addressed to the lO communication unit. If so, the communication unit switches to an active state, and a call set-up process is initiated. In order to receive the paging messages and to facilitate a fast call set-up, the communication unit further maintains synchronization with the serving base station. The synchronization is obtained from detection of synchronization frames 15 transmitted on the pilot signal of the serving base station. A UMTS or GSM communication unit may further exchange various control messages with the fixed network during the idle state operation.

In the example, shown in FIG. 2, one communication unit 217 is in an idle 20 state and thus performs the required functionality and operations specified for a communication unit in idle state. The fixed network of the cellular communication system thus communicates and interfaces with the communication unit 217 as specified in the technical specifications for idle

state operation.

The communication unit 217 further provides support functionality for the two other illustrated communication units 219, 221. In the described example, these two communication units 219, 221 are not independently supporting the total idle state functionality prescribed for a 30 communication unit in idle state. Rather, the two communication units 219, 221 are in a quiescent state, which in the preferred embodiment is a nonactive state wherein the communication units 219, 221 perform

reduced idle state functionality. Hence, the quiescent state communication units 219, 221 may perform none, some or most of the idle state functionality prescribed for an idle state communication unit. However, in addition, the idle state communication unit 217 functions as a support 5 communication unit providing additional idle state functionality on behalf of the two quiescent state communication units 219, 221. Hence, for a quiescent state communication unit 219, 221, the total functionality required in idle state is not performed individually by the quiescent state communication unit 219, 221 but by the combination of functionality lO performed by the quiescent state communication unit 219, 221 and the supporting communication unit 217. Specifically, the supportingcommunication unit 217 may perform all the idle state functionality required for the quiescent state communication unit 219, 221.

15 Hence, in the preferred embodiment, the quiescent state communication unit 219, 221 performs none or reduced idle state functionality and the missing functionality is made up for by the supporting communication unit 217. In the preferred embodiment, the quiescent state of a communication unit is thus a state wherein reduced idle state 20 functionality of the communication unit is performed. Typically, the reduced functionality is one associated with reduced power consumption.

Specifically, no idle state functionality may be performed.

Whereas the technical specifications standardised for a communication

25 system typically includes a specification of the idle state requirements, the

quiescent state may not be standardized but can for example be a proprietary state for a given manufacturer. Hence, if communication units are from the same manufacturer one may act as a supporting communication unit for the other in accordance with a proprietary and 30 non standardised interface and partitioning of functionality.

In the preferred embodiment, the supporting communication unit 217 thus provides one or more idle functions on behalf of one or more of the quiescent state communication units 219, 221.

5 Specifically, the supporting communication unit 217 may perform measurements of the radio environment and communicate these to the communication unit 219, 221 in the quiescent state. The quiescent state communication unit 219, 221 may then make idle mode processing decisions. Alternatively or additionally, the supporting communication lo unit 217 may perform the processing and decisions on behalf of the quiscent state communication units 219, 221. For example, it may determine that a location update is necessary and perform this by communicating with the fixed network.

15 If the communication units are sufficiently close, the measurements performed by the supporting communication unit 217 are representative of the conditions of the quiescent communication unit 219, 221.

Consequently, a significant reduction in power consumption can be achieved by powering down circuitry required for the measurements 20 without a degradation of performance. In this embodiment, the quiescent state communication unit 219, 221 may perform all other idle state functionality including communicating with the cellular communication system to transmit other messages or to receive messages. Specifically, the communication involved in a handover may be directly between the fixed 25 network and the quiescent state communication unit 219, 221.

In the preferred embodiment, both the supporting and quiescent state communication units 217, 219, 221 comprises short range wireless communication functionality for establishing a short range communication 30 link 223, 225 between the supporting 217 and quiescent state communication units 219, 221. Specifically, each of the communication units 217, 219, 221 comprises a Bluetooth transmitter and receiver. As is

known by the person skilled in the art, the Bluetooth communication standard has been developed for short range communication for ad-hoc networks, wherein communication links can be set up dynamically and quickly. As such, a Bluetooth connection is highly suitable for 5 communication between close cellular communication units, as it provides for a high data rate communication with low error rate and low power consumption. The range of a Bluetooth connection is in the order of tom, and therefore when a communication link can be set up between two communication units they will inevitably be close. Consequently, there to will be a high probability that radio environment measurements made by one communication unit will also be representative for the other communication unit.

It will be apparent that any suitable short range communication standard 15 or technique can be used including for example the WiFi, IEEE 802.11a or 802.11b protocols.

In the preferred embodiment, a communication unit 219, 221 in the quiescent state is operable only to communicate on the short range 20 communication link 223, 225. Hence, in the preferred embodiment, the quiescent state communication unit 219, 221 does not communicate directly with the fixed network but only through the short range communication link 223, 225. Consequently, the quiescent state communication unit 219, 221may power down all circuitry associated with 25 the communication over the cellular air interface. For a typical communication unit, this results in a very significant reduction in power consumption and thus a significant increase in the battery life of the communication unit.

30 In the preferred embodiment, all communication over the cellular air interface related to a quiescent state communication unit 219, 221is performed by the supporting communication unit 217. Any, information

required by or from the quiescent state communication unit 219, 221 is communicated over the short range communication link 223, 225. For example, if the fixed communication system requires specific subscriber information from the quiescent state communication unit 219, 221, the 5 supporting communication unit 217 will transmit a request for this information over the short range air interface 223, 225. The quiescent state communication unit 219, 221 will in response retrieve the required information and communicate it back to the supporting communication unit 217 over the short range air interface 223,225.

In the preferred embodiment, idle state control plane messages associated with the quiescent state communication unit 219, 221 are communicated over the short range air interface 223,225. Hence, the control functionality of the idle state can be maintained substantially unaltered even though 15 the idle state functionality is maintained through the supporting communication unit 217. Examples of such control plane messages for a UMTS cellular communication system include paging messages, location updates, authentication challenges, detach messages, cell broadcast messages (including cell broadcast SMS).

Alternatively or additionally, idle state call management messages initiated by the network, which are associated with the quiescent state communication unit 219, 221, are communicated over the short range communication link 223, 225. Such idle state call management messages 25 include paging messages or service inquiries. As a specific example for a UMTS communication system, when the network is attempting to setup a connection to the communication unit 219, it will initiate a paging message addressed to communication unit 219, which is broadcast on a base station paging channel. Communication unit 217 will decode this 30 message and forward it to communication unit 219. Communication unit 219 will then exit quiescent mode, and respond directly to the network in

response to the paging message by setting up a Radio Resource connection as normal.

Idle state call management messages initiated by communication unit 5 219, 221 are communicated directly by the relevant communication unit.

This communication unit will first exit the quiescent state and then communicate with the network directly using the normal protocols.

Alternatively or additionally, idle state mobility management messages lo for the quiescent state communication unit 219, 221 are communicated over the short range communication link 223, 225. Specifically, mobility management messages associated with changing the serving cell are exchanged by the supporting communication unit 217 on behalf of the quiescent state communication unit 219, 221. The messages are further is communicated between the supporting communication unit 217 and the quiescent state communication unit 219, 221 over the short range communication link 223, 225. Hence, the fixed network receives and transmits idle state mobility management messages as if it was communicating directly with the quiescent state communication unit 219, 20 221 in an idle state. However, instead of transmitting directly to and receiving directly from the quiescent state, the messages are transmitted to and received from the supporting communication unit 217.

In some embodiments, all messages will be communicated over the short 25 range communication link 223, 225 but in other embodiments or situations only a subset of messages are transmitted to the quiescent state communication unit 219, 221 or are received from the quiescent state communication unit 219, 221. Hence, in some embodiments, the majority of mobility messages are generated and processed by the supporting 30 communication unit 217 and messages are only communicated over the short range air interface 223, 225 when required. This reduces the complexity of the communication and allows for the quiescent state

communication unit 219, 221 to perform a minimum of functionality and communication thereby allowing for an increased power reduction. For example, messages relating to communication units 219, 221 in idle mode, that do not require authentication of either 219 or 221 may be 5 automatically handled by communication unit 217. Messages that require 219 or 221 to be authenticated, may be passed to these units by 217 for this authentication process to be performed, before the response is relayed back to the network via communication unit 217.

10 In another embodiment, communication unit 217 will perform all of the active monitoring of the radio environment, and transmission of radio messages on behalf of communication units 219, 221. However, the processing of idle state messages for 219 and 221 is still performed by 219 and 221 themselves. Communication unit 217 will inform, via the short 15 range communication link, 219 or 221 that an idle mode communication is required, and any supporting information relating to that communication message (such as details of the current radio measurements made by unit 217). Communication unit 219 or 221 will then create the necessary idle mode message, even though these units are still in quiescent mode, and 20 send the constructed message to unit 217 over the short-range link.

Communication unit 217 will relay this received message to the network on behalf of units 219 or 221.

In yet another embodiment, communication unit 217 will perform all of 25 the active monitoring of the radio environment on behalf of communication units 219, 221. However if an idle mode communication to the network is required by units 219 or 221, then these will be performed by communication units 219 or 221 themselves, who will exit the quiescent state for the duration of this communication. This process may be 30 instigated by a message sent to 219 or 221 from 217, or by 219, 221 themselves.

In the preferred embodiment, the idle state management functionality performed by the supporting communication unit 217 for the quiescent state communication unit 219, 221 comprises performing location updates.

Specifically, if the supporting communication unit 217 detects that it has 5 moved, and that it is still in communication with the quiescent state communication unit 219, 221, it can be assumed that the quiescent state communication unit 219, 221 has moved together with the supporting communication unit 217. The supporting and quiescent state communication units 217, 219, 221 may typically belong to the same lo person and thus move in a correlated way (for example, they may be carried by the same user). Hence, if the supporting communication unit 217 detects that it has moved, it performs a location update for both the supporting communication unit 217 itself as well as for the quiescent state communication unit 219, 221.

In the preferred embodiment, the quiescent state communication unit 219, 221 may provide control input to the supporting communication unit 217.

Hence, the quiescent state communication unit 219, 221 is operable to transmit control messages over the short range communication link 223, 20 225, and the supporting communication unit 217 is operable to operate in response to the control messages of the quiescent state communication unit 219, 221. The control messages may be direct control messages prescribing a specific operation of the supporting communication unit 217, or may be parameters or other information that may affect the operation 25 of the supporting communication unit 217, for example by affecting a decision criterion.

In the preferred embodiment, a communication unit in idle state, or about to enter idle state, will monitor the Bluetooth communication system to 30 detect if there are any communication units available, which are capable of operating as a supporting communication unit. Specifically, it may transmit a general request message inquiring if any suitable

communication units are within range. A suitable communication unit will comprise functionality for receiving this request message and in response generating an acknowledgement message comprising identification data.

Upon receiving this message, the first communication unit will establish 5 the short range communication link to the identified communication unit, exchange the required information and subsequently enter the quiescent state. It will be apparent, that any suitable method and protocol for establishing 10 a supporting communication unit for a quiescent state communication unit may be used without subtracting from the invention.

The quiescent state communication unit may exit the quiescent state in any suitable way. Typically, the quiescent state communication unit will IS exit the quiescent state when becoming involved in a communication service over the cellular communication system, or if the link between the quiescent unit and its supporting communication unit degrades unacceptably. If the communication service is instigated by the quiescent state communication unit, it transmits an exit message to the supporting 20 communication unit over the short range communication link. The exit message causes the supporting communication unit to cease to support the quiescent state communication unit, which subsequently enters and active state. If the short-range communication link between the units is terminated before the quiescent mode has been specifically exited, then 25 both the devices will detect this condition, and both will autonomously exit the quiescent state and quiescent support state.

If the quiescent mode is being exited for any reason, the supporting communication unit may send to the quiescent communication unit 30 information that may help it synchronies with the network and enter idle mode more quickly. This information could include the current base station identity, frequency, timing advance and frame time information,

access codes and CDMA codes. Hence, preferably, the messages communicated over the short range communication comprise the minimum information required for the quiescent state communication unit to enter an active state, wherein it can support a communication service.

5 Preferably, the information communicated is sufficient for the quiescent state communication unit to enter this active state as easily and speedily as it would from a conventional independent idle state.

If the supporting unit decides to initiate the exit of the quiescent mode 10 support, it may also send to the quiescent mode communication unit a reason for why this mode is being terminated, and may also append the message received from the network that caused the exit of the quiescent mode. An example of such a message is a paging message indicating call setup. The quiescent mode communication unit can synchronize back to 15 idle state, and pass the received network message to its normal call processing software as if it had directly received it from the network as normal. If the communication service is instigated from the fixed network, the 20 supporting communication unit detects that it has received a call activation message on behalf of the quiescent state communication unit. It then forwards the call activation message to the quiescent state communication unit over the short range communication link. The supporting communication unit then exits the supporting state for the 25 quiescent state communication unit. Upon receiving the call activation message, the quiescent state communication unit exits the quiescent state and enters an active state. The call activation message of the short range communication link may be identical with the call activation message on the cellular air interface, or any suitable call activation message may be 30 used.

In some embodiments, network elements of the cellular communication system are adapted to communicate with a supporting communication unit for a communication unit in a quiescent state. Hence, the network elements may have dedicated functionality for this purpose including 5 means for redirecting messages or for generating alternative messages for supporting communication units. However, in other embodiments, one or more network elements supporting a nonactive communication unit does not have dedicated functionality or knowledge of whether a given communication unit is in a idle state or a quiescent state. Indeed, some or lo most network elements may not have any knowledge that a possibility of a communication unit entering a quiescent state even exists. Such an embodiment may comprise means for intercepting messages for a communication unit in a quiescent state and redirecting these to the supporting communication unit. Specifically, the supporting l 5 communication unit may itself be operable to receive air interface messages directed to the quiescent state communication unit. In other embodiments, the fixed network may comprise additional functionality for intercepting messages in order to enable or facilitate the deployment of a supporting communication unit.

FIG. 3 is an illustration of a fixed network of a cellular communication system in accordance with an embodiment of the invention. The fixed network comprises the four base stations 201, 203, 205, 207 and three communication units 217, 219, 221 of the example of FIG. 2. One of the 25 communication units 217 acts as a supporting communication unit for the two other communication units 219, 221. Two of the base stations 201, 203 are connected to a first Radio Network Controller (RNC) 301. The two other base stations 205, 207 are connected to a second RNC 303. The RNCs 301, 303 are connected to a Mobile Switch Centre (MSC). The base 30 stations 201, 203, 205, 207, the RNCs 301, 303 and the MSC 305 are all standard UMTS network elements comprising no dedicated functionality

for supporting a communication unit supporting another communication unit in a quiescent state.

Each of the RNCs 301, 303 are coupled to a proxy processor 307, 309. The 5 proxy operator provides an interface between the fixed network and the supporting communication unit 217. Hence, the proxy processor 307 provides an idle state management interface to the fixed network for the quiescent state communication unit 219, 221. Thus, the proxy processor 307 and the supporting communication unit 217 together provide idle to state management functionality for the quiescent state communication units 219, 221.

Specifically, the proxy processor 307 may communicate with the supporting communication unit 217 through the cellular communication 15 system. The proxy processor 307 and the supporting communication unit 217 may communicate using any suitable protocol and specifically they may exchange all information required for the idle state management function of the quiescent state communication units 221, 223.

20 In the preferred embodiment, the proxy processor 307 monitors the communication from and to the RNC 301. Whenever a communication is detected that is directed to the quiescent state communication units 219, 221, it is intercepted and transmitted to the supporting communication unit 217. Likewise, whenever a communication is received from the 25 supporting communication unit 217, this is converted to a suitable communication format and fed to the RNC 301. Specifically, it is fed to the RNC 301 such that the RNC 301 processes it in exactly the same way as it would the corresponding message from an idle state communication unit.

In this way, both base stations, RNCs and the MSC function in a 30 conventional way without any consideration of the presence of supporting or quiescent state communication units.

As a specific example, a call may be initiated for a quiescent state communication unit 219 through the MSC 305. This will cause a paging message to be generated for the quiescent state communication unit 219.

This may be processed by the RNC 301 and transmitted by the base 5 station 201. However, as the communication unit 219 is in a quiescent state, it will be ignored by the communication unit 219. Nevertheless, the paging message will be intercepted by the proxy processor 307, which will forward it to the supporting communication unit 217. Upon receiving the call activation message, the supporting communication unit 217 will 10 forward it to the quiescent state communication unit 219, which will then enter an active state and initiate call set-up exactly as if it had received the original paging message.

In some embodiments, the proxy processor not only communicates with 15 the supporting communication unit but may also itself perform some of the idle state functionality and processing associated with a quiescent state communication unit. For example, Proxy Processor 307 may detect the normal idle state messages from communication unit 217. However if Proxy Processor 307 knows that communication unit 217 is supporting the 20 quiescent state of units 219 and 221, then 307 could perform the idle state procedures on behalf of 219 and 221 without further intervention from 217. If Proxy Processor 307 is trusted by the mobility management protocols of the mobile networks controlling units 219 and 221, authentication issues of the proxy process can be avoided.

In some embodiments, the cellular communication system comprises a plurality of sub-networks. For example, a cellular communication system may be a combination of a 2nd Generation communication system and a 3rd Generation communication system. Specifically, a cellular 30 communication system may comprise both a GSM cellular communication system and a UMTS cellular communication system. A given communication unit may be capable of communication on only one of the

GSM and UMTS communication systems or on both communication systems. The fixed network will thus comprise a GSM sub network and a UMTS sub-network. Typically, some network elements will be shared between the two sub networks.

In some such embodiments, the supporting and quiescent state communication units may be associated with different sub-networks.

Thus, the quiescent state communication unit may be a GSM communication unit whereas the supporting communication unit may be a 10 UMTS communication unit. In one preferred embodiment, the supporting communication unit communicates with a proxy processor that is associated with both the GSM and UMTS communication network. Hence, if the proxy processor intercepts a GSM message for the GSM quiescent state communication unit, it communicates this message to the UMTS 15 supporting communication unit through the UMTS communication system. The UMTS supporting communication unit may generate a message in reply to the received message, and communicate this to the proxy processor. The proxy processor converts this to an appropriate GSM message and feeds it to the GSM sub-network.

The different sub-networks may comprise different technologies and/or be differentiated administratively, for example by having different network operators. 25 The proxy processor may directly be interfacing with the mobility management functionality of one, more or all sub-networks. Specifically, it may be an integrated part of the network or sub network it is serving. In other embodiments, the proxy processor may be external to one, more or all of the sub-networks. The proxy processor may in this case be accessed 30 through a suitable gateway or suitable interface function. In some embodiments, the proxy processor may emulate a different network with respect to one or more of the sub-networks, and supporting of a

communication unit through the proxy processor is similar to a roaming situation with a different network.

5 In one embodiment most communication units are operable both to enter into a quiescent state and a supporting state. In this embodiment a group of communication units may alternate between being supporting and quiescent state communication units.

10 Specifically, when several communication units are in close proximity, and are capable of acting on behalf of the other communication units, a cyclical scheme of operation may be implemented. When connected by means of the short range communication network, each communication unit will have communicated it's ability to act as a proxy on behalf of the others.

15 One communication unit will be elected to be the supporting communication unit according to criteria such as: the communication unit with the longest available battery life, the communication unit with the longest time since it entered proxy mode. This communication unit will enter the supporting state for a period of time whilst the other devices will 20 enter the quiescent state. This period of time for acting as a supporting communication unit may be a fixed time, or depend on other criteria such as battery life remaining. Once this time expires, the communication unit will offer to exit the supporting state and the negotiation of who should take over the supporting state will be renegotiated between the 25 communication units. The supporting state negotiation process may be repeated any time a new device joins or leaves the local communication network. According to another feature of the invention, a single communication unit 30 may be capable of accessing more than one of the available sub-networks, and this invention may be used internally to put some sub-network modes of the communication unit into a low power quiescent state, thus only

keeping a smaller proportion of the communication unit's capabilities in the idle state.

According to another feature of the invention, a group of multimode 5 communication units, which can talk to each other via a local short-range network, may distribute amongst themselves the job of monitoring all of the different network technologies that need to be monitored. For example, consider three communication units that can each access three different radio communication technologies that need idle state monitoring. Each 10 unit could be set to only monitor one radio interface and place the other two interfaces into a quiescent state. For the radio interface the communication unit is monitoring, it does so on behalf of the other two units, which are in quiescent mode for this interface type, and viceversa.

This reduces each communication unit's overall power consumption 15 compared to running three radio technology idle mode systems simultaneously, and may improve performance as the unit only needs to monitor one technology, instead of finding time when it can monitor all three (including savings in excessive radio synthesizer retuning, etc.).

20 The invention can be implemented in any suitable form including hardware, software, firmware or any combination of these. However, preferably, the proxy processor of the invention is implemented as computer software running on one or more data processors. Various elements and components of an embodiment of the invention may be 25 located in a communication unit, the core network, the radio access network and/or any suitable physical or functional location. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the invention may be implemented in a singleunit or may be physically and functionally 30 distributed in the communication system and/or the communication units.

Although the present invention has been described in connection with the preferred embodiment, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims.

Claims

1. A communication system comprising a fixed network supporting a 5 plurality of communication units; the communication system comprising: a first communication unit operable to enter a quiescent state; and a second communication unit operable to enter a support state wherein the second communication unit supports the first communication unit in the quiescent state by communicating with the fixed network to 10 perform idle state management functionality associated with the first communication unit.

2. A communication system as claimed in claim 1 wherein the fixed network comprises a proxy processor operable to provide an interface 15 between the fixed network and the second communication unit when operating in the support state such as to provide an idle state management interface to the fixed network for the first communication unit. 20

3. A communication system as claimed in claim 2 wherein the proxy processor is operable to intercept messages from the fixed network addressed to the first communication unit and to communicate the intercepted messages to the second communication unit.

25

4. A communication system as claimed in claim 3 wherein the intercepted messages comprise a call activation message

5. A communication system as claimed in any previous claim wherein the second communication unit comprises a measurement unit for 30 performing idle state radio environment measurements for the first communication unit when in the quiescent state.

6. A communication system as claimed in any of the previous claims wherein each of the first and second communication units comprises a short range wireless communication element operable to establish a short range communication link between the first and second communication 5 unit.

7. A communication system as claimed in claim 6 wherein the first communication unit in the quiescent state is operable only to communicate on the short range communication link.

8. A communication system as claimed in claim 6 or 7 wherein the second communication unit is operable to enter the support state in response to a support request message received from the first communication unit over the short range communication link.

9. A communication system as claimed in any of the previous claims 6 to 8 wherein idle state control plane messages associated with the first communication unit are communicated over the short range communication link.

10. A communication system as claimed in any of the previous claims 6 to 9 wherein idle state call management messages associated with the first communication unit are communicated over the short range communication link.

11. A communication system as claimed in any of the previous claims 6 to 10 wherein idle state mobility management messages associated with the first communication unit are communicated over the short range communication link.

12. A communication system as claimed in any of the previous claims 6 to 11 wherein the first communication unit is operable to transmit control

messages over the short range communication link and the second communication unit is operable to operate in response to the control messages of the first communication unit.

5

13. A communication system as claimed in any previous claim wherein the second communication unit is operable to upon receiving a call activation message for the first communication unit forwarding the call activation message to the first communication unit over the short range communication link, and the first communication unit is operable to exit 10 the quiescent state upon receiving the call activation message.

14. A communication system as claimed in any previous claim wherein the idle state management functionality associated with the first communication unit comprises performing location updates.

15. A communication system as claimed in any previous claim wherein the first communication unit is operable to power down an air interface communication element for the communication system when in the quiescent state.

16. A communication system as claimed in any previous claim wherein the second communication unit when in the support state is operable to support a plurality of communication units in a quiescent state.

25

17. A communication system as claimed in any previous claim wherein the fixed network may comprise a plurality of sub-networks and the first and second communication unit may be associated with different sub-

networks. 30

18. A communication as claimed in claim 16 as dependent on claim 2 wherein the proxy processor is external to a first sub-network associated

with the first communication unit and the first sub-network is operatively coupled to the proxy processor through a gateway of the first sub-network.

19. A communication system as claimed in any previous claim wherein 5 the second communication unit is operable to enter a quiescent state; and the first communication unit is operable to enter a support state wherein the first communication unit supports the second communication unit in the quiescent state by communicating with the fixed network to perform idle state management functionality associated with the first 10 communication unit; and wherein the first and second communication unit alternate between being in the quiescent state and the support state.

20. A communication unit for a communication system having a fixed network supporting a plurality of communication units including at least a 15 first communication unit operable to enter a quiescent state; the communication unit comprising: means for entering a support state wherein the communication unit supports the first communication unit in the quiescent state by communicating with the fixed network to perform idle state management 20 functionality associated with the first communication unit.

21. A method of idle state support for a communication system comprising a fixed network supporting a plurality of communication units; the method comprising the steps of 25 entering a first communication unit into a quiescent state; and entering a second communication unit into a support state wherein the second communication unit supports the first communication unit in the quiescent state by communicating with the fixed network to perform idle state management functionality associated with the first 30 communication unit.