WO2005053347A1

WO2005053347A1 - Method and network system for establishing peer to peer communication between two users equipments camping in different cells

Info

Publication number: WO2005053347A1
Application number: PCT/IB2004/052399
Authority: WO
Inventors: Li Sun; Dan Shang; Robert James Davies
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2003-11-27
Filing date: 2004-11-16
Publication date: 2005-06-09
Also published as: CN1622678A

Abstract

A method to be performed in a network system is provided, for establishing P2P communication between two UEs, comprising steps of: receiving a call request from the calling UE of the two Ues (s102); judging whether the two UEs are camping in the same cell (s105); sending a paging message to the called UE if the two UEs are camping in different cells (s106); receiving a paging response from the called UE (s108); determining whether the two UEs meet the requirement for P2P communication according to the call request and the paging response (s109). In an embodiment, system information is sent to a UE so that said UE can switch to the same cell (s203), and radio resource information for peer to peer link probing is sent to the two Ues after they are accessing the same cell (s207). The cells can be managed by different network systems, and the cell request, paging response and a connection message from another network can include P2P communication capability of the respective calling or called UE.

Description

METHOD AND NETWORK SYSTEM FOR ESTABLISHING PEER TO PEER COMMUNICATION BETWEEN TWO USERS EQUIPMENTS CAMPING IN DIFFERENT CELLS

5 Field of the Invention The present invention relates generally to a method and apparatus for establishing P2P (Peer-to-Peer) communication, and more particularly, to a method and apparatus for establishing P2P communication between UEs in different cells. Background of the Invention In conventional cellular mobile communication systems, a UE (user equipment) has to communicate with the other UE only through the relaying of base stations regardless of the distance between the two UEs. Fig. 1 illustrates the conventional communication mode, where UE1 and UE25 exchange information through the UTRAN consisting of the base station transceiver (namely Node B) and the Resource Network Co ntroller (RNC), and this communication mode is also called UP -UTRAN-DOWN mode. However, in some cases when the distance between two UEs in the same cell is very close, it can be a more reasonable way for them to communicate directly, rather than through th e relaying of base stations. This method is the so-called peer-to-peer communication, abbr. as P2P. Fig. 2 illustrates a P2P communication mode, where the dashed line represents signaling link, the solid line represents data link and the arrowhead represen ts direction of information flow. Only signaling link exists between the UTRAN and the UE (user equipment) , while only data link exists between the two communicating UEs. Assume that only resource for maintaining basic communication is needed. A direct link is taken as one unit of radio resource (with fixed frequency, timeslot and spreading code), it can be easily drawn that P2P communication mode only needs two units of radio resource to maintain basic communication. If additional signaling cost for management is ignored, P2P communication can save about 50% radio resource than conventional communication mode. Meanwhile, the UTRAN still holds control over P2P communication, especially over how to use radio resources, so that network operators can easily charge for the radio resources used in P2P communication. It is commonly accepted that a Time Division Duplex ( TDD) air interface is a communication standard that offers a more flexible adaptation to different uplink and downlink traffic requirements. Among existing 3G systems based on TDD communication mode, TD-SCDMA (Time Division - Synchronization Code Division Multiple Access) system is an ideal communication system to be the most suitable for the combination of P2P communication with conventional communic ation mode, because the same carrier frequency is applied in both uplink and downlink communications, which can simplify the RF (Radio Frequency) module of the UE. A method and apparatus for establishing P2P communication in wireless communication networks , as described in a patent application entitled "A Method and Apparatus for Establishing P2P Communication in Wireless Communication Networks ", filed by KONINKLIJKE PHILIPS ELECTRONICS N.V., on March 7, 2003, with the application Serial NO.as 03119892.9, is suitable to any TDD CDMA communication system including TD -SCDMA systems, and the disclosures of which are hereby incorporated as reference. A method and apparatus for radio link establishment and maintenance with P2P communication in wireless communicat ion networks, as described in a patent application entitled "A Method and Apparatus for Radio Link Establishment and Maintenance with P2P Communication in Wireless

Communication Networks ", filed by KONINKLIJKE PHILIPS ELECTRONICS N.V., on March 7, 2003, with the Application Serial No. as 03119895.3, is suitable to any TDD CDMA communication system including TD -SCDMA systems, and the disclosures of which are herby incorporated by reference . After establishing uplink synchronization with the UTRAN through the same random access procedure as existing TD -SCDMA systems, the UE can establish a P2P direct link with the other UE, in accordance with the method and apparatus as described in the application whose application Serial NO. is 03119892.9, i.e.: allocate corresponding dedicated resource for two P2P Ues ; then, the P2P link between the two UEs can be established and maintained in accordance with the method and apparatus as described in the application whose application Serial NO. is 03119895.3, so that the two UEs can receive and transmit P2P signals in the allocated timeslots respectively, and thus P2P communication between two UEs can be achieved. The method and apparatus as described in the application document with the application Serial NO. as 03119892.9, is suitable for two UEs camping on the same cell to establish P2P communication. If two UEs are not camping on the same cell, when the application is applied to the two UEs in different cells to establish P2P communication, some problems ; as following will arise: (i) In P2P communication, if there is no additional RF transceiver, the transceivers of the two UEs are required to work at the same carrier frequency to receive and transmit P2P signals. But for TD -SCDMA systems, the adjacent cells may use diffe rent carrier frequencies , which means that one of the two UEs must move the carrier frequency of receive and transmit signals to the carrier frequency used by the cell where the other UE is camping if P2P communication is to be established between the two UEs camping in different cells. (ii) The radio resource used for current P2P communication in

TD-SCDMA systems, is allocated to the UEs by the network system via the base station in the cell where the UEs are camping. When a UE moves the carrier frequency of receive and transmit signals to the carrier frequency used by the cell where the other UE is camping, it may not be able to access the cell which the base station belongs to due to a too long distance away from its base station, poor propagation enviro nment of wireless communication or traffic overload of the cell. (iii) As described above, the P2P communication requires the two communicating UEs use the same radio resource . The radio resource used by each cell is allocated and managed by the RNC. As for different cells managed by different RNC, even the different cells of different Core Network (CN) operated by different operators or covered by PLMN , allocating the same radio resource for the different cells managed by different RNC also requires the reasonable adjust and allocation of the network resource and radio resource managed by operators. As described above, it can be seen that modifications are necessary to the method and apparatus as described in the application with the application Serial NO. as 03119892.9 if the P2P communication is to be established between the two UEs who camp on different cells. Summary of the Invention An object of the present invention is to provide a P2P communication establishment method and apparatus for UEs who camp on different cells. This method and apparatus can save radio resource and increase system capacity, as well as reduce interferences and improve system communication quality. To establish P2P communication between two UEs that are very close with each other but within different cells, e.g. to establish P2P communication between two UEs who camp on the borders of two close cells or in the overlapped coverage area of two different cells (existence of overlapped coverage area between two cells is due to network planning by different operators or the consideration of the operators about the traffic load balance in the network ), can save radio resource .increase system capacity, and also mitigate interferences and improve communication quality. The reasons are: (a) when the two UEs are in the borders of two different cells, each UE is far away from the access node B of its cell, so performance of the link between each UE and its access node B is poor. To guarantee a certain communication quality, each UE has t o increase its transmission power to maintain its conventional link with access node B, which will inevitably produce signal interference to other communication links in its cell and adjacent cells, (b) When the two UEs who camp on different cells are in the overlapped area, each UE communicates with its own access node , so interference between systems will be caused no matter than the overlapped area is due to network planning of different operators or the consideration of network operators about the traffic load balance of the network . In the above case of (a) and (b), when the two UEs who camp on different cells are very close, P2P communication mode can be a more reasonable option if the distance between the two UEs satisfies the requirement for P2P communication . A method for establishing P2P (Peer-to-Peer) communication between two UEs in accordance with the present invention, performed by a network system, comprises: (a) receiving a call request from the calling UE of the two UEs; (b) judging whether the two UEs are camping on the same cell; (c) sending a paging message to the called UE if the two UEs are camping on different cells; (d) receiving a paging response from the called UE; and (e) determining whether the two UEs satisfy the requirement for P2P according to the call request and the paging response; (f) establishing P2P link for P2P communication between the two UEs if the requirement for P2P communication is satisfied. A method to be performed by a UE, for the UE to establish P2P (Peer-to-Peer) communication with the other UE, comprises: sending a call request to a network system for establishing P2P communication with the other UE in a different cell; receiving radio resource for P2P link probing sent by the network system via the downlink of the cell where the UE is camping; utilizing the radio resource to carry out P2P link probing; performing P2P communication with the other UE after P2P connect probing succeeds. Brief Description of the Drawings Amore detailed explanation and description of the present invention will be made referring to the accompanying drawings and in conjoint with the embodiments as following, wherein : Fig.1 is a schematic diagram illustrating a TD -SCDMA system employing conventional communication mode; Fig.2 is a schematic diagram illustrating a TD -SCDMA system employing P2P communication mode; Fig.3A is a schematic diagram illustrating two UEs are camping on the borders of two adjacent cells managed by the same RNC respectively ; Fig.3B is a schematic diagram illust rating two UEs are camping on the overlapped area of two different cells managed by the same RNC; Fig.4A is a schematic diagram illustrating two UEs are camping on the borders of two adjacent cells those are not managed by the same RNC but belong to the same CN; Fig.4B is a schematic diagram illustrating two UEs are camping on the overlapped area of two different cells those are not managed by the same RNC but belong to the same CN; Fig.5A is a schematic diagram illustrating two UEs are camping on the borders of two adjacent cells those are managed by different RNCs and belong to different CNs; Fig.5B is a schematic diagram illustrating two UEs are camping on the overlapped area of two adjacent cells those are managed by different RNCs and belong to different CNs; Fig.6A and Fig.6B show the procedures for establishing P2P communication between UEs in different cells to be executed by the network system and the UE in accordance with the present invention; Fig.7 is a block diagram illustrating the network system proposed in the present invention, wherein the network system performs the procedure for establishing P2P communication between UEs in different cells. Detailed Description of the Invention When two UEs are camping on two different cells, depending o n whether the two cells are managed by the same RNC, belong to the same CN and belong to the PLMN of the same network operator, it can be classified into several cases as follows: (1) The two UEs are camping on two different cells, more specifically, the two UEs access two different nodes as NodeBI and NodeB2, but the two nodes are controlled by the same RNC. This means the two UEs belong to the same UTRAN . Meanwhile, If the two UEs are respectively camping on the borders of the two adjacent cells, as shown in Fig.3A. Due to network planning of different network operators or the consideration of network operator about traffic load balance, the two UEs may also camp on the overlapped area of the two cells respectively, as shown in Fig.3B. (2) The two UEs are camping on two different cells, more specifically, the two UEs access two different nodes as NodeBI and NodeB2, and the two nodes are controlled by two different RNCs as RNC1 and RNC2 respectively but RNC1 and RNC2 belong to the same CN. This means the two UEs are controlled by two different UTRAN s in the same CN . If the two UEs are camping on the borders of two adjacent cells respectively, it can be shown as Fig.4A; if the two UEs are camping on the overlapped area of the two cells respectively, it can be shown as Fig.4B. (3) The two UEs are camping on two different cells, more specifically, the two UEs access two different nodes as NodeBI and NodeB2, and the two nodes are controlled by two different RNCs in different CNs. That means the two UEs belong to different CNs. The different CNs may be run by the same network operator or different operators. If the two UEs are respectively camping on the borders of two adjacent cells, it can be shown as Fig.5A; if the two UEs are camping in the overlapped area of tw o adjacent cells respectively, it can be shown as Fig.δB. (4) The two UEs are camping on different cells, more specifically, the two UEs access two different nodes as NodeBI and NodeB2, NodeBI and NodeB2 are controlled by two different RNCs as RNC1 and RNC 2, RNC1 and RNC2 belong to different CNs as CN1 and CN2, and CN1 and CN2 are run by different network operators. This means the two UEs are registered in different PLMNs. This case is similar to those shown in Fig.5A and Fig.δB, but CN1 and CN2 belong to d ifferent PLMNs. In the following, descriptions will be given to the procedure for establishing P2P communication between UEs in different cells to be executed by the network system and the UE in accordance with the present invention, in a TD-SCDMA system, in conjunction with Fig.4B. According to the signal processing procedure between UE1 and UE2 and respective RNC1 and RNC2 and signal exchange between RNC1 and RNC2, the procedure for establishing P2P communication between UE1 and UE2 in different cells in accordance with the present invention, can be divided into four parts . First, determine whether to start the P2P establishment procedure in the present invention; second, determine whether UE1 and UE2 satisfy the requirement for establishing P2P communication; third, UE1 and UE2 attempt to establish P2P communication link by using the allocated radio resource; fourth, subsequent work after P2P communication link is established successfully. A detailed description will be given below to the four parts in conjunction with Fig.6A and Fig.δB. I Determining whether to start the P2P communication establishment procedure The same as in conventional mode, UE1 and UE2 respectively select their suitable cells to register through cell search procedure after powering on (step S101). As shown in Fig.4B, after successful registration, UE1 will camp on the cell managed by NodeBI and UE2 will camp on the cell managed by NodeB2. When UE1 wants to communicate with UE2, it will send a call request to NodeBI for communicating with UE2, via random access procedu re, as the same as in conventional mode (step S102). The call request should at least include information about whether UE1 has P2P communication capability and UE1 's location information. The same as in conventional mode, NodeBI sends the call request to its RNC1 (step S103). After receiving the call request, RNC1 judges whether

P2P communication mode should be preferred (step S104). If RNC1 doesn 't prefer P2P communication mode, it will establish conventional communication link between UE1 and UE2 accordi ng to conventional communication mode (step S503). If P2P communication mode is preferred, RNC1 queries the CN and related HLRA/LR (Home Location RegisterΛ isitor Location Register) according to UE2 's identification number such as IMSI (International Mobil e Subscriber Identity) or MSISDN (Mobile Station's ISDN Number) included in the call request, to obtain UE2 's registration information. Then, RNC1 judges whether UE1 and UE2 are camping on the same cell according to UE2 's registration information (step S10 5). If UE1 and UE2 are in the same cell, P2P communication will be established and maintained between UE1 and UE2, by using the methods and apparatuses as described in the application with the application Serial NO. as 03119892.9 and 03119895.3. If UE1 and UE2 are in different cells, the method in the present invention will be started to establish P2P communication between UEs camping on different cells. II Determining whether UE1 and UE2 satisfy the requirement for establishing P2P communication RNC1 transfers the call request from UE1 to RNC2 to which UE2 belongs. The transferred call request should at least include the information about whether UE1 has P2P communication capability and UE1 's location information. If UE1 's location information is not include d in the call request from UE1 , RNC1 can obtain UE1 's location information, through GPS for instance, and add it into the transferred call request. After receiving the transferred call request, RNC2 will send a paging message to UE2 via NodeB-2 (step S 106). The routing procedure for transferring the call request from RNC1 to RNC2 , can transfer signals between RNC1 and RNC2 according to the provisions in communication protocols. After receiving the paging message, UE2 sends a paging response to RNC2 via NodeB-2 (step S107). The paging response should at least include information about whether UE2 has P2P communication capability, and UE2's location information can also be included. If UE2 's location information is not included in the paging response, RNC2 ca n also obtain UE2's location information, through GPS for instance. After receiving the paging response from UE2 (step S108), RNC2 determines whether P2P communication can be established between UE1 and UE2, according to the transferred call request, the information about whether UE1 and UE2 have P2P communication capability, UE1 and UE2's location information, and the P2P policy of the network to which RNC2 belongs (i.e.: whether RNC2 permits P2P communication mode and etc), (step S109). If the requirement for establishing P2P communication between UE1 and UE2can't be satisfied, conventional communication link will be established between UE1 and UE2 according to conventional communication mode (step S503). If the requirement for establishing P2P communicati on between UE1 and UE2 can be satisfied, RNC2 sends a connect message to RNC1 , indicating that UE2 has accepted the call request (step S110). The connect message should include a flag for indicating UE1 and UE2 satisfy the requirement for P2P communication, and may also include information about whether RNC2 is willing to provide radio resource for P2P link. RNC1 receives the connect message from RNC2 (step S11), and learns whether UE1 and UE2 satisfy the requirement for P2P communication according to the connect message. The above procedure for judging whether UE1 and UE2 satisfy the requirement for P2P communication can be accomplished in RNC1. When the judging procedure is executed in RNC1, the connect message sent to RNC1 by RNC2 should include information about whether UE2 has P2P communication capability, UE2's location information, the information about the P2P policy of the network to which RNC2 belongs, such as whether RNC2 permits to adopt P2P communication mode , and the information about whether RN C2 is willing to provide radio resource for P2P link. RNC1 determines whether P2P communication can be established between UE1 and UE2, according to the call request from UE1 and the information included in the connect message from RNC2, which includes whether UE1 and UE2 have P2P communication capability, UE1 and UE2's location information, and the P2P policy of RNC2 's network , and sends the judgment result to RNC2. Ill UE1 and UE2 attempts to establish P2P communication by using the allocated radio resourc e After it is determined that P2P communication can be established between UE1 and UE2, RNC1 and RNC2 identify the system synchronization shift between NodeB -1 and NodeB-2 (step S201), to guarantee that UE1 or UE2 can access the corresponding cell correctl y when switching to the cell managed by NodeB -2 or NodeB-1. The procedure for identifying synchronization shift is similar to the procedure for identifying synchronization shift between cells during cell handover in conventional protocols. In TD-SCDMA systems, adjacent cells use completely different carrier frequencies, so RNC1 and RNC2 should negotiate about who provides radio resource and manages P2P link after synchronization shift is determined (step S202). During negotiation, the current radio resource utilization, the cell coverage range , current traffic load in the cells managed by NodeB -1 and NodeB-2 and the mobility of UE1 and UE 2 should be sufficiently taken into consideration. Assume that RNC1 takes charge of providing P2P radio resource and P2P link management after negotiation, then RNC1 provides specific system information to UE2 via RNC2-NodeB-2 (step S203). The system information includes the carrier frequency, code group used by the cell managed by NodeBI and the above determined synchronizat ion shift information. If RNC2 takes charge of providing radio resource for P2P communication and P2P link management after negotiation, the system information that should have been allocated and provided by RNC1 will be provided by RNC2, while the followi ng steps that should have been executed by RNC1 and RNC2 respectively will be accomplished by the corresponding RNC2 and RNC1 (step S204). After acquiring the system information provided by RNC1 via

RNC2-NodeB-2, UE2 will start a random access procedure (s tep S205), and attempts to access the cell managed by NodeB -1 by using the system information provided by RNC1 (step S206). That is: UE2 will move the carrier frequency from that used by the cell managed by NodeB -2 to that by NodeB-1. Meanwhile, UE2 record s its current state in NodeB -2. If UE2's access to NodeB-1 fails, UE2 returns back to its former state in NodeB-2, and acquires radio resource allocated by RNC2 via RNC2-NodeB-2 (step S502), then continues with conventional communication (step S503). If UE2's access to NodeB-1 is successful (In Fig.4B, UE2 is in the overlapped area of the cells managed by NodeB -1 and NodeB-2, so UE2 should be able to access NodeB -1), RNC1 sends radio resource for P2P link probing to UE1 and UE2 via NodeB -1 respectively , such as information about timeslots allocated for P2P communication and etc (step S207). After receiving the radio resource for P2P link probing from RNC1 via NodeB -1, UE1 and UE2 move to the allocated P2P dedicated channel P2P -DCH (step

S208), and start P2P connect probing (step S209), to determine whether

P2P communication can be conducted between UE1 and UE2 by using the allocated P2P-DCH (step S210). If P2P connect probing fails, UE2 returns back to its former state in

NodeB-2, and acquires the radio resou rce allocated by RNC2 via

RNC2-NodeB-2 (step S502), and then continues conventional communication with UE1 (step S503). If P2P connect probing succeeds, UE1 or UE2 sends a P2P connect probing success message to RNC1 via NodeB -1 (step S211), indicating that

UE1 and UE2 have established P2P communication link successfully by using the allocated radio resource. rv Sequent work after P2P communication link is established successfully After receiving the P2P connect probing success message, RNC1 sends a P2P connect confirm message to RNC2, to inform RNC2 that UE1 and UE2 are ready to start P2P communication (step S 301). After receiving the P2P connect confirm message from RNC1, RNC2 records UE2's state, and updates UE2 's related information in HLR/VLR (step S302), so that the network system can get UE2 's correct location information from HLR/VLR after UE2 alters the registered cell when UE2 's location information is needed. Then, RNC2 reclaims the radio resource occupied by the control link between NodeB-2 and UE2, and UE2 is managed by NodeB -1/RNC1 (step S303). UE1 and UE2 start P2P communication in the same cell a naged by

NodeB-1 (step S304). During P2P communication procedure, the maintenance of the P2P link can refer to the application with the application

Serial NO. as 03119895.3, how to reduce the possible interferences caused by introducing P2P communication c an refer to the technical details as disclosed in the application with the application Serial NO. as 03119894.5, 03128689.5, 03110415.0 and 03123740.1 , with the applicant as Royal Philips Electronics . If UE1 and UE2 can 't satisfy the requirement for P2P communication, a switching can be made between P2P mode and conventional mode, by referring to the method as described in the patent application document entitled "A Method for Supporting P2P Communication Switching in Wireless Communication Networks ", submitted along with the present application document, with the assignee as Royal Philips Electronics whose archive ID is CN030056. When P2P communication ends, UE2 will be forced to carry out a routine cell search and location update procedure, to ensure that it registers in the most suitable cell and update location information in HLR VLR (step S401). The above description is given to the procedure for establishing P2P communication between UE1 and UE2 in different cells that are managed by different RNCS but belong to the same CN as shown in Fig.4B, in conjunction with Fig.δA and Fig.δB. Based on the above embodiments as described in Fig.δA and Fig.δB, the present invention provides different solutions for the above -mentioned cases about whether two UEs are ca mping on two cells managed by the same RNC, whether the two cells belong to the same CN and whether the two cells belong to the PLMN runby the same network operator.

1. If UE1 and UE2 are camping on different cells managed by the same RNC This case (as shown in Fig.3B) is just like RNC1 and RNC2 in the above embodiment are converged into one RNC. In this case , all operations executed respectively by RNC1 and RNC2 in above procedures will be carried out by the RNC.

2. If UE1 and UE2 are camping on different cells managed by different RNCs as RNC1 and RNC2, but RNC1 and RNC2 belong to the same CN In this case (as shown in Fig.4B), RNC1 sends the call request to RNC2 via CN, RNC2 sends message to UE2 via NodeB -2 after receiving the call request, and vice versa . The P2P communication establishment procedure is the same as the procedure as described in above embodiment. 3. If UE1 and UE2 are camping on different cells managed by different

RNCs as RNC1 and RNC2, and RNC1 and RNC2 belong to different CNs as CN1 and CN2 In this case (as shown in Fig.5B), RNC1 sends the call request to RNC2 via CN1 and CN2, RNC2 sends message to UE2 via NodeB -2 after receiving the call request, and vice versa.

4. If UE1 and UE2 are camping on different cells managed by different PLMNs In this case (as shown in Fig.5B), RNC1 sends the call request to RNC2 via CN1, inter -connecting gateway ( if inter-connecting gateway exists between two PLMNs ) and CN2, RNC2 sends message to UE2 via NodeB -2 after receiving the call request, and vice vers a. From the above analysis, it can be seen that P2P communication between UE1 and UE2 in different cells can be achieved based on the above embodiments, in all above cases where the two cells are managed by the same RNC, or by different CNs or by different PLMNs, except that the routing situation between each RNC may be different. The method for establishing P2P communication between UE1 and UE2 in different cells as proposed in the present invention, can be implemented in computer software, or hardware mod ule with software functions, or in combination of software and hardware. When computer hardware is adopted to implement the method for establishing P2P communication between UE1 and UE2 in different cells as proposed in the present invention, the network s ystem structure is shown in Fig.7, wherein the components the same as in conventional network systems are not given. As Fig.7 shows, network system 100 comprises: a receiving unit 101 , for receiving a call request from the calling UE (e.g. UE1) of UE1 and UE2 who attempt to establish P2P communication, wherein the call request at least includes information about UE1 's P2P communication capability; a judging unit 102, for judging whether the two UEs are camping in the same cell; a sending unit 104, for sendi ng a paging message to the called UE (e.g. UE2) when the judging unit judges that the two UEs are camping on different cells; after receiving unit 101 receives a paging response sent by the called UE2, judging unit 102 will determine whether the two UEs sa tisfy the requirement for P2P communication according to the call request and the paging response, wherein the paging response at least include information about the called UE2's P2P communication capability; if the judging unit judges that P2P communicati on requirement is satisfied, establishing unit 103 will establish P2P link for P2P communication between the two UEs. When establishing unit 103 establishes P2P link, sending unit 104 sends the system information of the cell where the other UE (such as UE1 ) camps to one UE of UE1 and UE2 (such as UE2) , so that UE2 can switch to the same cell as UE1, wherein the system information at least includes the carrier frequency used by the cell where UE1 camps, synchronization shift between the cells where UE1 and UE2 camp. After UE1 and UE2 accessed the same cell, sending unit 103 sends radio resource for P2P link probing to the two UEs, wherein the radio resource at least includes information about the timeslots allocated for P2P communication. When receiving unit 101 receives the P2P connect probing success message sent by UE1 or UE2, updating unit 105 will update the location information of UE2 who changed a cell to camp on HLRA LR to its location information in current cell. When above judging unit 102 judges th at UE1 and UE2 are camping on two different cells and the two cells are managed by different network systems, the negotiating units and management units in the network systems decide which network system will take charge of the above system information sent to UE2 and radio resource provided to UE1 and UE2 for P2P communication. If the calling UE1 belongs to network system 100, transferring unit 106 in network system 100 first transfers UE1 's call request to the called network system to which the called UE2 belongs (the called network system can have basically same modules as the calling network system 100). The receiving unit in the called network system receives the forwarded call request, and sends a paging message to the called UE2 via the sending unit. After receiving the called UE 2's paging response, the sending unit in the called network system will send a connect message to the calling network system 100 according to the paging response. Negotiating unit 107 in the calling network system 100 negotiate s with the negotiating unit in the called network system about the calling network system 100 or the called network system provides the above system information and radio resource for P2P communication. After establishing unit 103 establishes P2P link betw een UE1 and UE2, the management unit in the network responsible for providing radio resource for P2P communication (e.g. if network system 100 is responsible for providing system information and P2P radio resource, it will be management unit 108 in network system 100), manages the P2P link between UE1 and UE2 during P2P communication course according to the negotiation result.

Beneficial Results of the Invention As described above, the present invention proposes a method and apparatus for establishing P2P c ommunication between UE1 and UE2 in different cells. UE2 in the cell managed by NodeB -2 can obtain system information such as the carrier frequency of the cell where UE1 camps via the route between RNC1 to which UE1 belongs and RNC2 to which UE2 belongs and the link between RNC2 and NodeB2, thus accesses the same cell as UE ln this way, the present invention skillfully converts the problem of establishing P2P communication between UE1 and UE2 in different cells into a procedure for establishing P2P communication between UE1 and UE2 in the same cell, moreover it can continue to use the various schemes for avoiding interferences caused by introducing P2P communication as described in the above application documents. Thus, radio resources of the communication system can be saved to increase system capacity and mitigate interferences so as to improve communication quality of the communication system. It is to be understood by those skilled in the art that the method for establishing P2P communication between UE1 and UE2 in different cells as disclosed in this invention is not limited herein for TD -SCDMA systems, but also applicable to other TDD radio systems. For example, when it 's applied in TSM (TD-SCDMA for Mobile) systems, the above operations performed, by Node B, RNC and CN in the present invention will be executed by BSS (Base station transceiver and controller) and MSC (Mobile Switching

Center). It is to be understood by those skilled in the art that the method for establishing P2P communication between UEs in different cells as disclosed in this invention can be modified considerably without departing from the spirit and scope of the invention as defined by the appended claims .

Claims

WHAT IS CLAIMED IS:

1. A method to be performed in a network system, for establishing P2P communication between two UEs (user equipment), comprising steps of: receiving a call request from the calling UE of the two UEs; judging whether the two UEs are camp ing in the same cell; sending a paging message to the called UE if the two UEs are camping in different cells; receiving a paging response from the called UE; determining whether the two UEs meet the requirement for P2P communication according to the call request and the paging response.

2. The method in claim 1 , further comprising: establishing P2P link for P2P communication between the two UEs if the requirement for P2P communication is met.

3. The method in claim 1 or 2, wherein said call request at leas t includes the information about the P2P communication capability of said calling UE, and said paging response at least includes the information about the P2P communication capability of said called UE.

4. The method in claim 3, wherein step (f) includes: sending to a UE of the two UEs the system information about the cell where another UE is camping, so that said UE can switch to the same cell with said another UE; sending radio resource for P2P link probing to said two UEs after said two UEs access the same cell.

5. The method in claim 4, wherein said system information at least includes the frequency of the carrier used by said same cell and the information about synchronization shift between said different cells, and said radio resource for P2P link prob ing at least includes the information about the time slot allocated for P2P communication.

6. The method in claim 4, further comprising: receiving the message about success of P2P connection probing sent by any one of said two UE; updating the location information of said UE who alters cell to camp in HLR VLR, to the location information about being within the same cell.

7. The method in claim 3, wherein step (c) further includes: the calling network system which said calling UE belongs to, forwards said call request to the called network system which said called UE belongs to, if said different cells are managed by different network systems.

8. The method in claim 7, further comprising: receiving a connection message from said called network system.

9. The method in claim 8, wherein step (e) includes: determining whether said two UEs meet the requirement for P2P communication according to said call request and said connection message, wherein said connection message at least includes the information about the P2P communication capability of said called UE.

10. The method in claim 7, further comprising: receiving said call request forwarded by said calling network system; sending said paging message to said called UE; receiving said paging response from said c ailed UE; sending said connection message to said calling network system according to said paging response.

11. The method in claim 10, further comprising: determining whether said two UEs meet the requirement for P2P communication according to said call r equest and said paging response.

12. The method in claim 11, wherein said connection message at least includes the judgment information about whether said two UEs meet the requirement for P2P communication.

13. The method in claim 7, further comprising: negotiating about providing said system information by one of said calling network system and said called network system; managing said P2P link established between said two UEs by the network system determined through negotiation; wherein said radio resourc e for P2P link probing is sent to said two

UEs by said network system determined through negotiation via the downlink of the cell it governs.

14. The method in claim 13, further comprising: receiving said message about success of P2P connection probing; sending an ACK message of P2P connection to said another network system so that said another network system updates the location information about the UE who formerly camped in the cell belonging to said another network system to the location information abo ut the cell belonging to said network system determined through negotiation.

15. The method in claim 14, further comprising: receiving said ACK message of P2P connection; updating the location information of the UE who formerly camped in the cell belonging to the network system, to the location information about the cell belonging to said network system determined through negotiation. withdrawing the radio resource occupied by said UE who formerly camped in the cell belonging to the network system.

16. The method in claim 1 , further comprising: judging whether P2P communication is preferred; wherein it's to be determined whether said two UEs can establish P2P link when P2P communication is preferred.

17. The method in claim 6, wherein radio resource is alloc ated to said two UEs so that said two UEs can communicate in conventional mode when said two UEs can 't meet the requirement for establishing P2P communication or said two UEs can 't access said same cell or P2P link probing between said two UEs fails.

18. A method to be performed by a UE, for said UE to establish P2P communication with another UE, comprising: sending a call request to a network system to establish P2P communication with said another UE in a different cell; receiving radio resource for P2P li nk probing sent by said network system via the downlink of the cell where said UE is camping; utilizing said radio resource for P2P link probing; performing P2P communication with said another UE after P2P connection probing succeeds.

19. The method in claim 18, further comprising: receiving the system information about the cell where said another UE is camping sent by said network system; accessing the same cell with said another UE by using said system information; wherein said system information at least includes the frequency of the carrier used by said same cell and the information about synchronization shift between different cells.

20. The method in claim 19, further comprising: sending a message about success of P2P connection probing to said network system after P2P connection probing succeeds.

21. The method in claim 18, wherein said call request at least includes the information about the P2P communication capability of said UE.

22. The method in claim 18, further comprising: receiving a paging mes sage from said network system; sending a paging response to said network system; wherein said paging response at least includes the information about the P2P communication capability of said UE.

23. The method in claim 18, further comprising: performing a cell search and location information updating procedure after P2P communication ends.

24. The method in claim 18, wherein said two UEs return to the state in the cells where they formerly camped and communicate in conventional mode by utilizing the acquired radio resource allocated by the network system to which the cells where said two UEs formerly camped belong, when said two UEs can 't access said same cell or the P2P link probing between said two UEs fails.

25. A network system for performing the method of establishing P2P communication between two UEs, comprising: a receiving unit, for receiving a call request from the calling UE of said two UEs; a judging unit, for judging whether said two UEs are camping in the same cell; a sending unit, for sending a paging message to the called UE when said judging unit judges that said two UEs are camping in different cells; wherein: said receiving unit receives a paging response sent from the called UE; said judging unit determines whether said two UEs meet the requirement for P2P communication according to said call request and said paging response; an establishing unit, for establishing P2P link for P2P communication between said two UEs when said judging unit judges that the requirement for P2P communication is me t.

26. The network system in claim 25, wherein said sending unit sends to a UE of said two UEs the system information about the cell where another UE is camping so that said UE can switch into the same cell with said another UE when said establishing unit establishes P2P link, and said sending unit sends radio resource for P2P link probing to said two UEs after said two UEs access the same cell.

27. The network system in claim 26, wherein said call request at least includes the information about the P2P com munication capability of said calling UE, said paging response at least includes the information about the P2P communication capability of said called UE, said system information at least includes the frequency of the carrier used by said same cell and the information about synchronization shift between different cells, and said radio resource for P2P link probing at least includes the information about the time slot allocated for P2P communication.

28. The network system in claim 27, further comprising: an updating unit, for updating the location information of said UE who alters cell to camp in HLR/VLR, to the location information about being within the same cell.

29. The network system in claim 27, further comprising: a forwarding unit, for the calling ne twork system to which said calling UE belongs, to forward said call request to the called network system to which said called UE belongs, when said different cells are managed by different network systems; wherein: said receiving unit receives said call re quest forwarded by said calling network system; said sending unit sends said paging message to said called UE; said receiving unit receives said paging response from said called UE; said sending unit sends said connection message to said calling network system according to said paging response.

30. The network system in claim 29, further comprising: a negotiating unit, for negotiating about providing said system information by one of said calling network system and said called network system; a managing unit, for managing said P2P link established between said two UEs; wherein said radio resource for P2P link probing is sent to said two