Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Definitions

• the present invention relates to localization in a heterogeneous radiocommunication system. It relates more particularly to the location of a mobile terminal in a radiocommunication system comprising two separate subsystems.
• Many location services are known. Within the framework of these services, location information is generally required, from a client to a location server, for a given mobile terminal.
• the location information which is an estimate of the positioning of the mobile terminal, is determined by the location server, on the basis of measurements made by base stations or, in the case which interests us later, by the mobile terminal following the location request. This information is finally returned to the customer at the origin of the location request.
• Location services are for example provided in the second generation (2G) radiocommunication system called GSM ("Global System for Mobile communications") or in the extension of this system to packet data transmission, called GPRS ("General Packet Radio Service ").
• GSM Global System for Mobile communications
• GPRS General Packet Radio Service
• FIG 1 shows a 2G radiocommunication system capable of implementing such a location service.
• the system represented comprises in particular two base stations or BTS ("Base Transceiver Station") 11 and 12, connected to a base station controller or BSC ("Base Station Controller") 14, itself connected to a network core or CN (“Core Network”) 16.
• a mobile terminal 10 is also in radio link with the BTS 11.
• the system shown also includes a location center for mobile or SMLC ("Serving Mobile Location Center") 15, which can be integrated into the radio subsystem or else be independent equipment as illustrated in FIG. 1, where it is connected to the BSC 14 via an Lb interface.
• the SMLC implements a location service for the terminal 10 at the request of a client 17 which can be internal or external to the radiocommunication system to which the terminal 10 is attached.
• the protocol used between the SMLC and the mobile terminal is the RRLP. It is used in particular to command the terminal to make measurements with a view to localization, then to transmit these measurements to the SMLC for processing, via the radio subsystem.
• the protocol is defined in the technical specification TS 44.031, version 6.1.0, "Location Services (LCS); Mobile Station (MS) - Serving Mobile Location Center (SMLC); Radio Resource LCS Protocol (RRLP)", published in September 2003 , by 3GPP.
• Three main localization methods can be implemented by the system of Figure 1.
• the first localization method is based on the Timing Advance parameter.
• the BTS 11 which has a radio link with the terminal 10 measures a time difference between the reception of a frame from the terminal and a reference instant, which allows it to have an estimate of the propagation time of the frame between terminal 10 and BTS 11.
• E-OTD Enhanced Observed Time Difference
• LMU Location Measurement Unit
• the LMU can either be integrated in a BTS of the system, or be an independent equipment whose position is well identified, as illustrated in figure 1.
• SMLC 15 can then estimate a positioning of the mobile terminal 10 by subtracting RTD from OTD.
• a third location method is based on the GPS positioning system ("Global Positioning System”).
• the position of the mobile terminal 10 is then estimated by the SMLC 15 according to the GPS system.
• Location services are also provided in the third generation (3G) radiocommunication system called UMTS ("Universal Mobile Telecommunication System").
• FIG. 2 shows schematically a 3G radiocommunication system capable of implementing such a location service.
• the system represented comprises in particular two base stations or Nodes B 21 and 22, connected to a radio network controller or RNC ("Radio Network Controller") 24, itself connected to a core network or CN ("Core Network ") 26.
• RNC Radio Network Controller
• a mobile terminal or UE (“ User Equipment ”) 20 is also in radio link with Node B 21.
• the system shown also includes a location center (SMLC), which can be integrated into the subsystem radio or be independent equipment.
• SMLC location center
• the SMLC is then called SAS ("Stand-Alone SMLC").
• a SAS 25 connected to the RNC 24 via a PCAP interface is thus represented in FIG. 2.
• the PCAP interface is described in technical specification 25.453, version 6.2.0, "UTRAN lupc interface Positioning Calculation; Application Part (PCAP) signaling” , published in September 2003 by the 3GPP.
• PCAP Application Part
• the RNC 24 which is responsible for the implementation of the location procedure, at the request of a client 27 which may be internal or external to the radiocommunication system to which the UE 20 is attached.
• the SAS 25 is then used as a simple location calculation server, when the RNC 24 does not perform the calculation itself.
• the protocol used for exchanges between the RNC 24, which is then a Serving RNC, and the UE 20 is the RRC protocol, as defined in the technical specification TS 25.331, version 5.6.0, "Radio Resource Control (RRC) protocol specification ", published in September 2003 by 3GPP.
• RRC Radio Resource Control
• This protocol notably provides messages to command the terminal to make measurements with a view to localization, as well as for the feedback of these measurements to the RNC.
• RRC Radio Resource Control
• This protocol notably provides messages to command the terminal to make measurements with a view to localization, as well as for the feedback of these measurements to the RNC.
• a first localization method is based on a cell identification or Cell ID. The UE is thus located by knowing the identity of the Node B with which it is linked, the position or the coverage area of the Node B being known.
• the network can then probe it for example by paging, so that it is attached to a Node B.
• This cell identification can be supplemented by other measurements such as RTT ("Round Trip Time”) measurements which give an approximation of the round trip propagation time between the UE and its Node B with which it is in association.
• RTT Random Trip Time
• a second location method is called OTDOA-IPDL
• Each Node B can optionally introduce periods of silence (IPDL), so as to improve the listening quality of neighboring Nodes B by the UE, and to avoid the phenomenon of dazzling of the UE by a Node B close from which it receives a signal with a strong level of field.
• IPDL periods of silence
• a third location method is based on measurements of the GPS type performed by the EU, as in the 2G case described above.
• a multimode UE with capacities to operate according to several systems, for example 2G or 2.5G and 3G (third generation) can perform measurements on command of the radiocommunication system to which it is attached at a given time. If, at a given time, the UE is in connection with a BTS 2G, it will be able to carry out measurements of type 2G on the order of an SMLC.
• the UE If, at another time, the UE is in connection with a 3G Node B, it can carry out 3G type measurements on the order of its SRNC (Serving RNC).
• SRNC Serving RNC
• a location based on measurements made by such a UE according to its sub-system (2G-2.5G or 3G) of attachment is not always optimal. This is particularly noticeable in a heterogeneous radiocommunication system comprising a 2G (or 2.5G) subsystem and a 3G subsystem, the two subsystems having different service areas. For example, 2G coverage is almost uniform, while 3G coverage is more disparate.
• a UE located in the 3G coverage area will then go back to measures for a 3G type location, while a 2G location would have benefited from the higher density of radio equipment and would therefore have resulted in a finer location .
• the 3G location method implemented uses the IPDL functionality described above, the implementation of a 2G location method would have avoided the presence of periods of silence on the part of the Node B received by the EU with the strongest signal, and the degradation of the link, or even the momentary interruption of communication that results.
• the location of a UE in connection with a BTS 2G, but also close to a Node B 3G from which it receives a slightly weaker signal may be less precise than if it had been carried out in 3G.
• the accuracy of the location which is a random quantity, is inversely proportional to VB c, where B represents the bandwidth of the system and ⁇ represents an observation period. Since 3G bandwidth is approximately 15 times greater than 2G bandwidth, localization in 3G is approximately 4 times more precise than localization in 2G, for equal observation time. At almost equivalent radio conditions in the two subsystems, a 3G type location is therefore generally preferable to a 2G type location.
• the location methods offered by each of the two subsystems based on measurements made by a dual-mode UE, are currently compartmentalized, so that the location performed is sometimes imprecise.
• An object of the present invention is to overcome these drawbacks, and to improve the accuracy of the location of mobile terminals in a heterogeneous radiocommunication system. Another object of the invention is to take advantage of the location methods provided in different radiocommunication systems, in order to obtain an improved location according to the methods available.
• the invention thus provides a method of localization in a radiocommunication system comprising at least a first and a second subsystem and means for locating a mobile terminal, the mobile terminal being able to communicate and to carry out measurements relating to localization.
• the means for locating the mobile terminal being arranged to take into account at least some of the measurements made by the mobile terminal.
• the method comprises the following steps when the mobile terminal is in connection with the first subsystem: - carrying out, at the mobile terminal, measurements relating to the location on the second subsystem; - transmit the measurements made to the first subsystem; and - implement the means for locating the mobile terminal by taking into account at least some of said measurements transmitted to the first subsystem.
• a location is thus obtained based on measurements of the second subsystem, and possibly also of the first subsystem. This improves the reliability of the location.
• the measurements are carried out at the mobile terminal on command of the first subsystem with which the mobile terminal is linked. This command can also be prompted by a request from location issued on the initiative of a customer internal or external to the radiocommunication system, which may be the mobile terminal itself if necessary.
• a sounding mechanism is implemented in order to create such a link.
• said first and second subsystems can be second generation (2G or 2.5G) radiocommunication systems for one and third generation (3G) for the other.
• the first subsystem is capable of processing the measurements made on the second subsystem by the mobile terminal, it advantageously takes them into account in its location algorithm, in the same way as the location measurements possibly performed on the first subsystem -system by the mobile terminal. This case can arise in particular when the measurements carried out on the second subsystem are compatible with a localization method used by the first subsystem.
• the first subsystem is not capable of processing the measurements made on the second subsystem by the mobile terminal itself, it then advantageously transmits them to the second subsystem so that they can be processed there. using an appropriate localization method.
• the result of this processing gives location information which is returned to the first subsystem, in order to be taken into account in a location carried out further by taking into account measurements made by the mobile terminal on the first subsystem.
• the invention further provides a location system for locating a mobile terminal, the location system being arranged to implement the above method.
• the invention also provides a location device for locating a mobile terminal, in a first subsystem of a communication system. radiocommunication further comprising a second subsystem, the mobile terminal being capable of communicating and of carrying out measurements relating to the location on either of the first and of the second subsystems.
• the location device comprises, relative to a mobile terminal in connection with the first subsystem: - means for commanding the mobile terminal to carry out measurements relating to the location on the second subsystem; - means for receiving the measurements made; and - means for locating the mobile terminal.
• the 3 represents a heterogeneous system comprising a 2G or 2.5G subsystem and a 3G subsystem.
• the 2G or 2.5G subsystem includes a BTS 31, connected to a BSC 33, itself connected to a core network switch 37 which can be an MSC ("Mobile Switching Center”) if one is in a context of communication in circuit mode, or a SGSN ("Serving GPRS Support Node”) if you are in a communication context in packet mode.
• the 3G subsystem includes a Node B 32, connected to an RNC 34, itself connected to a core network switch 38 which can be an MSC or an SGSN.
• a UE 30 is also capable of communicating with each of the two subsystems.
• a radio link can be established with either of the BTS 31, in the case of 2G, or of the Node B 32, in the case of 3G.
• the system shown in Figure 3 also includes locating means. Among these, there is in particular an SMLC 35 connected to the BSC 33 and a SAS 36 connected to the RNC 34.
• a GMLC (“Gateway Mobile Location Center”) 39 is also connected to the two radiocommunication subsystems via their respective switches 37 and 38.
• This GMLC 39 is a platform which constitutes the first access point for an external client 40 which wishes to require the implementation of a location service in one of the subsystems (it will be noted that the location request can also be made by a client internal to the radiocommunication system, which can moreover be the mobile terminal 10 itself).
• the GMLC can then interrogate the HLR 41 to find the location area in which the UE 30 is located, if this is not being communicated.
• the UE 30 has a radio link with the BTS 31, that is to say that the UE 30 is in 2G (or 2.5G) mode. This can happen in particular when the signal received at UE 30 from BTS 31 is greater than that received from Node B 32.
• UE 30 is either during communication via the BTS 31, the communication being carried by a radio channel, either in a mode where it receives signaling from the BTS 31 without a real communication being in progress.
• This poll may for example consist in paging the UE 30, after having determined the location zone in which the UE 30 is located, as indicated above.
• a location required by a client 40 can then be made from measurements carried out in 3G, possibly in addition to 2G measurements.
• this request is received by the GMLC 39, then transferred to the SMLC 35, for example via the MSC / SGSN 37.
• An RRLP request is then transmitted from the SMLC 35 to the UE 30 so that the latter performs useful measurements for localization. It reaches the UE 30, via the radio equipment 33 and 31.
• This request indicates to the UE 30 that measurements must be carried out on Nodes B of the 3G subsystem, possibly in addition to measurements on the BTS of the 2G subsystem, like BTS 31.
• the UE 30 returns to SMLC 35 measurements made on the 3G subsystem, for example from signals received from Node B 32.
• the measurements performed are of the 3G type and correspond to one of the 3G location methods presented in the introduction. It may for example be OTDOA type measurements. If the RRLP request transmitted to the UE 30 specifies a specific location method, the measurements carried out by the UE 30 will preferably conform to the specified method.
• the SMLC 35 supports the implementation of a location method corresponding to the 3G measurements carried out. This can in particular be the case, when a shared location center is used for the 2G and 3G subsystems, combining the functions of SMLC 35 and SAS 36, and therefore capable of locating a UE from 2G, 3G or mixed 2G + 3G. If the SMLC 35 is not capable of processing 3G type measurements itself, it advantageously retransmits them to SAS 36 of the 3G subsystem.
• This transmission can be done directly if a communication interface is available between the SMLC 35 and the SAS 36 (for example an Lp type interface as it currently exists between two SMLCs and that is described in the technical specification TS 48.031, version 5.0.0, "Technical Specification Group GSM EDGE Radio Access Network; Location Services (LCS); Serving Mobile Location Center - Serving Mobile Location Center (SMLC-SMLC); SMLCPP specification", published in July 2002 by 3GPP ), or via GMLC 39 which is connected to SMLC 35 and SAS 36.
• the SAS 36 then has 3G type measurements which it can use to implement a 3G type location method as presented in the introduction. It thus plays its role of calculation server for the location of the UE 30.
• the result of this location is then advantageously returned to the SMLC 35 which has subcontracted the location calculation based on 3G measurements, so that it provide it to the client 40 at the origin of the location request, via the GMLC 39.
• the SAS 36 can return the result of its location calculation directly to the client 40.
• both 2G type measurements on the 2G subsystem and 3G type measurements on the 3G subsystem these measurements are advantageously processed by SMLC 35 or SAS 36, if the one of these two pieces of equipment is capable of processing such mixed measurements.
• 3G type measurements are transmitted to SAS 36, while 2G type measurements are processed at SMLC 35.
• 3G measurements transmitted to SAS 36 can be the subject of a first location calculation. It is then advantageous to transmit the result of this calculation to the SMLC 35, so that the latter possibly supplements it from the measurements carried out on the 2G subsystem.
• the UE 30 has a radio link with Node B 32. This can happen in particular when the signal received at UE 30 from Node B 32 is greater than that received from BTS 31. A communication is then in progress on the 3G infrastructure, or the UE 30 receives signaling from the 3G subsystem. As in the previously described case, if such a link does not exist, we probe then the UE 30 to establish one, for example by paging, in order to be able to command the UE 30 to carry out location measurements.
• a location required by a client 40 can then be made according to a 2G location method, starting from 2G type measurements possibly supplemented by 3G type measurements.
• the request from the client 40 is thus transmitted to the GMLC 39 which returns it to the RNC 34.
• the latter transmits to the UE 30 a RRC message, via the Node B 32, commanding it to take measures capable of being used according to a 2G type location method, possibly in addition to 3G type measurements.
• the type 2G measurements made by the UE 30 can be of a type specified in the RRC request, for example OTD measurements.
• the latter returns them to the RNC 34.
• the latter can then transfer the measurements to the SAS 36 via a PCAP interface, so that the SAS implements a localization method taking into account 2G measurements performed.
• 3G type measurements made and reported by the UE 30 to the RNC 34 these are advantageously taken into account in the location calculation carried out by the SAS 36, in addition to the 2G type measurements. Similar to the previous case, we can rely on the SMLC 35 to determine a location based on the measurements made on the 2G subsystem, if the SAS 36 is not able to do this calculation itself, for example because the location methods implemented by the SAS 36 do not take as input parameters 2G measurements of the type of those reported by the UE 30.
• the location is then made by the SMLC 35 according to a method of 2G localization corresponding to the type of measurements carried out. It can also be supplemented by a location based on measurements made on the 3G subsystem, the determination of which is advantageously entrusted to SAS 36 by the RNC 34.
• the final location which can be that which has been determined on the a either of the 2G or 3G subsystems, or else according to a combination of the results obtained for each of these subsystems is then supplied to the GMLC 39 so that it communicates it to the requesting client 40.

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  • 2004-11-10 EP EP04821062A patent/EP1698203A2/de not_active Withdrawn
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