Abstract:
There is disclosed a method of supporting location services in an unlicensed mobile access network, comprising transferring location related information between one or more mobile stations and a network control element.

Description:
BACKGROUND TO THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to unlicensed mobile access networks, and more particularly to the support of location services in such networks.  
         [0003]     2. Description of the Related Art  
         [0004]     “Unlicensed Mobile Access” (UMA) is a proposal to create a BSS (base station sub-system) look-alike access system architecture for “tunneled GSM” over two existing unlicensed-band radio interfaces: Bluetooth and WiFi (802.11). It is proposed that UMA may be used, for example, for coverage extensions in indoor applications (such as home or office applications) to capture otherwise fixed line traffic for cellular operators. In the US, UMA is perceived as a cheaper way to provide missing coverage to domestic users at home than via a macro network.  
         [0005]     There is a current European proposal to use UMA architectures in combination with a GSM (global system for mobile communication) RAN (radio access network), known as a GERAN. The unlicensed mobile access network (UMAN) is proposed to consist of UMA network controllers (UNCs), and access points (APs), which APs conform to a BlueTooth or WiFi standard as appropriate.  
         [0006]     The UMA signaling protocol architecture for circuit switched domain (between a mobile station, an access point, and an UNC) is shown in  FIG. 1 .  
         [0007]     A consortium of companies (reference can be made to http://www.umatechnology.org/) have drafted specifications for UMANs. Location Services in UMA  
         [0008]     At least some of these UMAN specifications include some discussion of location services (LCS).  
         [0009]     The published document “UMA Architecture (Stage 2) R1.0.2” discusses LCS support. Specifically discussed is emergency service support for United States Federal Communications Code (FCC) E911 Phase 2 requirements. A number of ways in which the location of a terminal performing an emergency call may be obtained are discussed (in chapter 9.17.2.1). In one way the UNC may maintain a database of AP locations. The AP location is provided from a terminal via a known URR REGISTER REQUEST/URR REGISTER UPDATE message or via some management interface. In another way the terminal may provide its current location (e.g. obtained via the A-GPS interface) in a URR REGISTER/UPDATE message. In another way the UNC can look up a location database based on a public IP address and/or MAC address of a terminal.  
         [0010]     Location services are discussed in chapter 9.18 of the published document “UMA Architecture (Stage 2) R1.0.2”. Cell information (of possibly available GSM coverage) may be used by the UNC to determine the location of a terminal. As another possibility, the AP identity is mentioned. Cell and AP information can be provided from the terminal to the UNC using URR-REGISTER and URR-REGISTER UPDATE messages.  
         [0011]     Likewise, the document “UMA Protocols (Stage 3) R1.0.2” discusses LCS support. URR REGISTER REQUEST and URR REGISTER UPDATE UPLINK messages are identified as including the following information elements (IE) useful for location purposes: AP radio identity; cell identity; Geographic Location; and AP location. AP radio identity IE is used for transmission of Bluetooth Device address (BD_ADDR) or WLAN MAC Address of AP. There is a field called “Type of Identity” which contains only a value “IEEE MAC-address format”. Other values are for future use. A cell identity IE identifies the cellular cell. A geographic location IE can be used to deliver, for example, an A-GPS location estimate from the terminal. An AP location IE is for indicating the location of a terminal or an AP to the network.  
         [0012]     T-Mobile USA has proposed in the UMA Forum that the Lb interface should be used between a UMA network controller (UNC) and a serving mobile location centre (SMLC). The Lb interface is the 3GPP GERAN standardized interface between a base station controller (BSC) and the SMLC. The Lb interface and the protocol stack between a SMLC, BSC, and Mobile Station (MS) (as described in 3GPP TS 43.059 v6.4.0) is shown in  FIG. 3 .  
         [0013]     The RRLP (Radio Resource LCS Protocol) is a protocol that defines the location related information exchanged directly between a MS and the SMLC. Currently the RRLP supports Enhanced Observed Time Difference (E-OTD), Global Positioning System (GPS), and Assisted GPS (A-GPS) location methods.  
         [0014]     The proposal from T-Mobile USA to use the 3GPP standardized Lb interface between an UNC and a SMLC provides for the possibility to reuse existing GERAN SMLCs in the UMAN. However a problem with UMA specifications, as can be seen from the document “UMA Protocols (Stage3) R1.0.2, is that there is no mechanism to deliver E-OTD, GPS, or A-GPS related information from the UNC towards mobile stations. There are no messages or information elements available that could include such information.  
         [0015]     While E-OTD, which requires that the mobile station can receive signals from at least three separate base station sites, may not usually be a feasible location method with UMA, A-GPS can be expected to be an important solution for UMA.  
       SUMMARY OF THE INVENTION  
       [0016]     A method of supporting location services in an unlicensed mobile access network, comprising transferring location related information between one or more mobile stations and a network control element.  
         [0017]     The location related information may include one or more of: enhanced observed time difference information; global positioning system, GPS, information; or assisted GPS location information.  
         [0018]     The location information may be transferred by inclusion in a unlicensed mobile access message. The location information may be transferred in an information element in a unlicensed mobile access message.  
         [0019]     The location related information may be transferred in a new unlicensed radio resource, URR, message. The location related information may be transferred in a modified existing unlicensed radio resource, URR, message. The location related information may be transferred in a modified existing unlicensed radio resource, URR, message enhanced to contain one or more new information elements.  
         [0020]     An unlicensed radio resource message including a measure position request may be transmitted from the network control element to a mobile station. An unlicensed radio resource message including a measure position response may be transmitted from a mobile station to a network control element.  
         [0021]     An unlicensed radio resource message including assistance data may be transmitted from the network control element to a mobile station. An unlicensed radio resource message including an assistance data acknowledgement may be transmitted from a mobile station to a network control element.  
         [0022]     There may be provided an unlicensed mobile access network including a network control element and a network access point, in which there is supported location services, in which one or more mobile stations and a network control element are adapted to transfer location related information therebetween.  
         [0023]     The transfer of location information may comprise inclusion of location information in an unlicensed mobile access message. The transfer of location information may comprise inclusion of location information in an information element of an unlicensed mobile access message.  
         [0024]     The invention may provide a mobile station for connection in an unlicensed mobile access network, the mobile station being adapted to communicate location related information between with a network control element of the unlicensed mobile access network.  
         [0025]     The location information may be received and transmitted by the mobile station in an unlicensed mobile access message, such as in an information element in a unlicensed mobile access message.  
         [0026]     The location related information may be received and transmitted by the mobile station in a new unlicensed radio resource, URR, message. The location related information may be received and transmitted by the mobile station in a modified existing unlicensed radio resource, URR, message. The location related information may be received and transmitted in a modified existing unlicensed radio resource, URR, message enhanced to contain one or more new information elements.  
         [0027]     An unlicensed radio resource message including a measure position request may be received by the mobile station from the network control element. An unlicensed radio resource message including a measure position response may be transmitted from the mobile station to a network control element.  
         [0028]     An unlicensed radio resource message including assistance data may be received by the mobile station from the network control element. An unlicensed radio resource message including an assistance data acknowledgement may be transmitted from the mobile station to a network control element.  
         [0029]     The invention may provide a network access point for an unlicensed mobile access network, the network access point being adapted to communicate location related information with one or mobile stations of the unlicensed mobile access network.  
         [0030]     The location related information may be received and transmitted by the access point in a new unlicensed radio resource, URR, message. The location related information may be received and transmitted by the access point in a modified existing unlicensed radio resource, URR, message. The location related information may be received and transmitted in a modified existing unlicensed radio resource, URR, message enhanced to contain one or more new information elements.  
         [0031]     An unlicensed radio resource message including a measure position request may be transmitted by the network access point to the mobile station. An unlicensed radio resource message including a measure position response may be received by the access point from the mobile station.  
         [0032]     An unlicensed radio resource message including assistance data may be transmitted by the network control element to the mobile station. An unlicensed radio resource message including an assistance data acknowledgement may be received by the access point from the mobile station. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0033]     The invention is described by way of example with reference to the accompanying figure in which:  
         [0034]      FIG. 1  illustrates a UMA signaling protocol architecture for circuit switched domain;  
         [0035]      FIG. 2  illustrates signaling between a serving mobile location centre and a target mobile station in the circuit switched domain in a GERAN;  
         [0036]      FIG. 3  illustrates a proposed unlicensed mobile access architecture in which the invention and embodiments thereof may be implemented;  
         [0037]      FIG. 4  illustrates RRLP over UMA-RR signaling protocol architecture for a circuit switched domain;  
         [0038]      FIG. 5  illustrates RRLP measure position procedure with new RRLP carrying URR message; and  
         [0039]      FIG. 6  illustrates RRLP assistance data procedure with new RRLP carrying URR message. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0040]     The invention is described herein by way of example with reference to a number of embodiments. The invention is described in the context of an unlicensed mobile access system operating in conjunction with a licensed mobile access system, and specifically, in exemplary embodiments, a GERAN system.  
         [0041]     With reference to  FIG. 3 , there is shown a GERAN  102  including at least one base station  104  and at least one base station controller  106 . A mobile station  108  is connected, via a licensed air interface  110 , to the base station  104  of the GERAN  102 . The base station  104  is connected to the base station controller  106  via a communication link  116 . The base station controller  106  is connected to a core network  112  via an A/Gb interface connection  114 .  
         [0042]     With further reference to  FIG. 3 , there is shown a UMA  122  including at least one standard access point  124 , or network access point, and at least one UMA network controller (UNC)  126 , or network control element. A mobile station  128 , being a UMA terminal, is connected, via an unlicensed air interface  120 , to the standard access point  124  of the UMAN  122 . The standard access point  124  is connected to the UNC  126  via a communication link  136 . The UNC  126  is connected to the core network  112  via an A/Gb interface connection  134 .  
         [0043]     The architecture of network arrangements as illustrated in  FIG. 3  is known to those skilled in the art. It should be noted that the mobile stations  108  and  128  are preferably configured to connect in either a GERAN or a UMAN, in accordance with available network coverage and implementation requirements.  
         [0044]     A SMLC  150  is provided as part of the UMAN  122 .  
         [0045]     The invention and embodiments thereof provides for an enhancement to unlicensed mobile access so that it is possible to transfer E-OTD, GPS, and A-GPS related information between mobile stations and UNCs.  
         [0046]     In embodiments this is preferably done either by: including in UMA messages specific information elements; or by allowing RRLP messages to be transported in UMA signaling, i.e providing containers for RRLP messages.  
         [0047]     Refering to the  FIG. 1 , the preferred layer for this is the UMA-RR layer. There are two alternatives for this. In a first possibility a new Unlicensed Radio Resources (URR) message is created that contains A-GPS and other information. In a second possibility some existing URR messages are enhanced to contain new information elements.  
         [0048]     By way of an implementation example, a case may be considered with new URR messages that contain RRLP messages. The protocol stack would then be as shown in  FIG. 4 .  
         [0049]     One possible signaling scenario is as shown in  FIG. 5 , for an RRLP measure position procedure.  
         [0050]     As represented by message  502 , the SMLC  150  sends a RRLP Measure Position Request to the UNC  126  over the Lb interface. This RRLP message may, for example, carry a request for location information, and it may also contain GPS assistance data.  
         [0051]     The UNC  126  packs the RRLP Measure Position Request into a new “URR RRLP” message  504  that it sends to the MS  128 . URR RRLP is a specific URR message intended to carry RRLP messages between the UNC and MSs.  
         [0052]     The MS  128  responds with a RRLP Measure Position Response message, that may contain for example an A-GPS location estimate, embedded in a URR RRLP message  506 .  
         [0053]     The UNC  126  forwards the RRLP Measure Position Response  508  to the SMLC  150 .  
         [0054]     In a similar fashion, the RRLP Assistance data procedure according to an embodiment of the invention is described with reference to  FIG. 6 .  
         [0055]     The SMLC  150  sends a RRLP Assistance Data message  602  to the UNC  126  over the Lb interface. This RRLP message may for example carry GPS assistance data.  
         [0056]     The UNC  126  packs the RRLP Assistance Data into a URR RRLP message  604  that it sends to the MS  128 .  
         [0057]     The MS  128  responds with a RRLP Assistance Data Ack. message embedded in a URR RRLP message  606 .  
         [0058]     The UNC  126  forwards the RRLP Assistance Data Ack. Message  608  to the SMLC  150 .  
         [0059]     The above discussion of the problem addresses by embodiments of the invention, and discussion of the embodiments themselves, has been given assuming usage of the Lb interface between an UNC and a SMLC.  
         [0060]     However, the problem and the embodiments of the invention are also valid with other possible interfaces between the UNC and the SMLC. For example the Iu-PC interface, that is defined for UTRAN between a SMLC and a RNC, may be adapted with RRC messages corresponding to RRLP messages.  
         [0061]     The problem and embodiments of the invention are also valid even in the case where there is no interface, i.e. where there is provided a combined UNC and SMLC.  
         [0062]     The invention, and embodiments thereof, advantageously provide an A-GPS and E-OTD location method which can be used with UMA, without needing new hardware.  
         [0063]     As A-GPS is the main location method in 3G and 2G mobile communication standards, a mechanism to carry A-GPS assistance data from the UNC to the mobile is advantageous.  
         [0064]     The invention, and embodiments thereof, provide for various advantages and improvements to the art. These advantages include improved location information. The uncertainty of location information can be estimated. Potential large location estimation errors due to invalid assumption of proximity of a terminal to an access point are avoided. Easy implementation is allowed for. No new hardware is needed.  
         [0065]     Various modifications to the described embodiments will be understood by one skilled in the art. The scope of protection afforded by the invention is defined by the appended claims.