WO2006016330A1

WO2006016330A1 - Method and apparatus for dynamic frequency reuse

Info

Publication number: WO2006016330A1
Application number: PCT/IB2005/052593
Authority: WO
Inventors: Li Sun; Dan Shang; Sheng Pan
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2004-08-10
Filing date: 2005-08-03
Publication date: 2006-02-16
Also published as: JP2008510343A; EP1779602A1; CN1735256A; KR20070046845A; TW200708145A

Abstract

A dynamic frequency reuse method and apparatus for use in P2P communication to be executed in a communication network system is proposed in the present invention, comprising steps: determining a group of candidate frequencies for use in P2P communication in a cell according to the predefined radio resource management scheme of the communication network; sending said group of candidate frequencies to a UE in the cell so that the UE can detect the strength of signals using said group of candidate frequencies, thus to determine the frequency for the UE to carry out P2P communication.

Description

METHOD AND APPARATUS FOR DYNAMIC FREQUENCY REUSE

FIELD OF THE INVENTION

The present invention relates generally to a communication network, and more particularly, to a dynamic frequency reuse method and apparatus for UEs to carry out direct communication, like P2P communication.

BACKGROUND ART OF THE INVENTION

In conventional cellular mobile communication systems, only through the relaying of base stations can a UE (user equipment) communicate with another UE. Fig.l illustrates this conventional communication mode used in TD-SCDMA systems, in which UEl and

UE2 exchange information through UTRAN consisting of a base station transceiver (Node B) and a RNC (radio network controller). But in some cases where two UEs camping in a cell are very close to each other, it can be a more reasonable way for them to communicate directly, and this is the so-called peer-to-peer communication, abbreviated as P2P. Typically, P2P communication is applied to TDD radio systems where the same carrier frequency is adopted in both uplink and downlink. In the following, TD-SCDMA system will be taken as an example to describe two P2P communication modes.

Fig.2 shows a P2P communication mode. As shown in Fig.2, P2P direct links can be established as represented by the solid line to transfer traffic data between UEl and UE2, whereas UTRAN monitors direct links through control links as represented by the dashed line between it and UEs. This P2P communication mode controlled by the base station is called as online P2P communication. Without the relaying of base stations, online P2P communication can save up to 50% radio resource, and meanwhile UTRAN still keeps control of the P2P communication. Descriptions as how to realize online P2P communication are disclosed in the patent applications filed by KONINKLIJKE PHILIPS

ELECTRONICS N.V. on March 7, 2003, Application Serial No. 03119892.9 and 03119894.5, and incorporated herein as reference.

Based on the above online P2P communication mode, a new communication mode can further be built for the UEs to carry out P2P communication in a self-organizing way without support of base stations, and this is called as offline P2P communication mode.

Fig.3 shows a schematic diagram of the offline P2P communication mode. As shown in the figure, before starting offline P2P communication, UEl and UE2 first register offline P2P communication service at UTRAN in conventional communication mode and obtain the P2P communication identification of their peer. The detailed procedure in which a UE obtains the P2P communication identification, is described in the patent application filed by KONINKLIJKE PHILIPS ELECTRONICS N.V., Attorney's Docket No. CN030003, along with the present application and incorporated herein as reference. Then, two UEs establish P2P communication independently according to the P2P communication identification of their peer obtained during the registration procedure, without control and support of UTRAN. Finally, UEl and UE2 return to idle mode in conventional communication after the P2P communication is completed.

Compared with online P2P communication, signaling cost can be saved further in offline P2P communication, and P2P communication link can be established even when the UEs are located outside the coverage area of wireless networks, such as ocean, mountain, battlefield and etc. Furthermore, the offline P2P communication mode can also be applied in the case where two UEs are very close to each other in a cell. At this time, no control link exists between UTRAN and UEs, so users can enjoy offline P2P communication service much cheaper than conventional communication as long as the transmit power of UEl and UE2 decreases to low enough to be ignored by the network system. When two UEs camping in a cell inside the coverage area of the communication network adopts online or offline P2P communication mode to establish P2P communication link, they usually use the frequency for conventional communication in the cell to conduct P2P communication. The frequency for conventional communication is the radio frequency resource assigned to the cell when the network operator sets up the communication network. Therefore, in the cell, there may be two communications sharing the same frequency: P2P communication and conventional communication.

In the same cell, interference occurs not only between P2P communication and conventional communication sharing the same frequency, but also between different pairs of P2P communicating UEs sharing the same frequency. The interference still lingers between different pairs of offline P2P communicating UEs in a certain area(namely the range that signals transmitted from P2P UEs can reach) outside the coverage area of the communication network. Some methods have been put forward to cancel or mitigate interference, such as uplink/downlink synchronization and scrambling code reuse, and so on, but they still fail to fully solve the interference between P2P communication and conventional communication and between pairs of P2P communicating UEs sharing the same frequency.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dynamic frequency reuse method and apparatus for use in P2P communication, which can effectively cancel interference between P2P communication and conventional communication sharing the same frequency within the coverage area of the communication network.

A dynamic frequency reuse method for use in P2P communication to be executed in a communication network system is proposed according to the present invention, comprising: (a) determining a group of candidate frequencies for use in P2P communication in a cell according to the predefined radio resource management scheme of the communication network; (b) sending said group of candidate frequencies to a UE in the cell so that the UE can detect the strength of signals using said group of candidate frequencies, thus to determine the frequency for the UE to carry out P2P communication.

A dynamic frequency reuse method for use in P2P communication to be executed in a UE is proposed according to the present invention, comprising: receiving a group of candidate frequencies for the UE to carry out P2P communication sent from a communication network system, wherein said group of candidate frequencies is determined by the communication network system according to the frequency planning information and radio resource management policy information; detecting the strength of signals using said group of frequencies to determine the frequency for the UE to carry out P2P communication.

A communication network system is proposed according to the present invention, comprising: a determining unit, for determining a group of candidate frequencies for use in

P2P communication in a cell according to the frequency planning information and the predefined radio resource management policy information of the communication network; a sending unit, for sending said group of candidate frequencies to a UE in the cell so that the UE can detect the strength of signals using said group of candidate frequencies, thus to determine the frequency for the UE to carry out P2P communication.

A UE is proposed according to the present invention, comprising: a receiving unit, for receiving a group of candidate frequencies for the UE to carry out P2P communication sent from a communication network system, wherein said group of candidate frequencies is determined by the communication network system according to the frequency planning information and radio resource management policy information; detecting the strength of signals using said group of frequencies to determine the frequency for the UE to carry out P2P communication

Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of the conventional communication mode in the communication system;

Fig. 2 is a schematic diagram showing a TD-SCDMA system adopting P2P communication mode;

Fig.3 is a schematic diagram showing a TD-SCDMA system adopting offline P2P communication mode;

Fig.4 is a schematic diagram illustrating the frequency allocation in a cell in accordance with an embodiment of the present invention;

Fig.5 is the flowchart diagram showing the dynamic frequency reuse method for use in P2P communication in accordance with an embodiment of the present invention; Fig.6 is the block diagram illustrating architecture of the UE and network system implementing the dynamic frequency reuse method for use in P2P communication in accordance with an embodiment of the present invention.

Throughout the drawing figures, like reference numerals will be understood to refer to like parts and components. DETAILED DESCRIPTION OF THE INVENTION

According to the dynamic frequency reuse method as proposed in the present invention, RNC determines the candidate frequencies in each cell to be used for P2P communication according to the frequency planning and radio resource management policy of the current communication network, and broadcasts the candidate frequencies of each cell via base stations to each UE in the cell. According to the candidate frequencies for use in P2P communication in the serving cell, a UE in the cell detects the strength of signals using the candidate frequencies to communicate, and notifies RNC of the detection result. According to the detection result in conjunction with the usage of all current candidate frequency resource of the UE 's serving cell, RNC selects a frequency suitable for the UE to carry out P2P communication from the candidate frequencies and sends it to the UE. The UE performs P2P communication with this frequency, or namely dynamically reusing frequency resource.

TD-SCDMA system will be taken as an example below to describe the dynamic frequency reuse method for use in P2P communication as proposed in this invention, in conjunction with accompanying drawings. Fig.4 is a schematic diagram showing frequency allocation of a cell in a communication network, and it's supposed that the network operator has 10 frequencies available: Fl, F2, F3,F4, F5, F6, F7, F8, F9 and FlO. Assumed that the frequency reuse factor adopted by the frequency planning of the current network is 7, Fl is the primary frequency of the serving cell Al of the UE, and adjacent cells of Al are A2, A3, A4, A5 and A6, with primary frequency as F2, F3, F4, F5, F6 and F7 respectively. The network operator reserves frequencies F8, F9 and FlO, not yet allocated as primary frequency of any current cell.

Fig.5 illustrates the procedure of acquiring P2P communication frequency using signaling link between UEl and UTRAN, taking UEl in cell Al as an example. As shown in Fig.5, first of all, UTRAN determines the UE's candidate frequencies for use in P2P communication in cell Al according to the frequency planning information and frequency resource management policy information (step SlO).

When determining the UE's candidate frequencies for use in P2P communication in cell Al, UTRAN first excludes primary frequency Fl for conventional communication in cell Al from the 10 available frequencies Fl to FlO owned by the network operator. Then, according to the frequency planning information and frequency resource management policy, UTRAN further excludes those frequencies that have been defined not to be used for P2P communication. For instance, F 8 is defined as the frequency to be used in emergency, so it's forbidden to be used for P2P communication in cases not urgent; the adjacent cell A2 is a hot-spot cell with extraordinarily high overload of conventional communication traffic and its primary frequency F2 is forbidden to be used as the candidate frequency for P2P communication in other cells. Accordingly, UTRAN can determine that in cell Al the UE can use candidate frequencies F3, F4, F5, F6, F7, F9 and FlO for P2P communication.

After determining the candidate frequencies for the UE to carry out P2P communication in the cell Al, UTRAN encapsulates a list of these candidate frequencies into a system information message, and broadcasts the system information message via a common control channel such as BCCH (step S20).

Wherein, the information entity including these candidate frequencies can alone form a system information message and be broadcasted to the UEs in the cell, or as a part of other system information message, be broadcasted to the UEs in the cell along with other system information messages. Furthermore, UTRAN can regularly update and broadcast the system information message including the candidate frequencies according to the management policy information and the operation status of the network (idle or busy).

UEl reads the system information message over BCCH and extracts the candidate frequencies from the system information message (step S30). According to the extracted candidate frequencies, UEl detects the strength of signals using these candidate frequencies to communicate (step S40).

Wherein signals using these candidate frequencies to communicate can be signals for conventional communication in adjacent cells or signals for ongoing P2P communication including signals for P2P communication in the current cell and signals for P2P communication in adjacent cells as well. So, in addition to detect the pilot signals in adjacent cells to get the strength of signals for conventional communication using the candidate frequencies, UEl also needs to detect the strength of signals for P2P communication using these candidate frequencies in the current cell.

According to the detected signal strength, UEl ranks these candidate frequencies (step S50). Generally speaking, the lower the strength of pilot signals in adjacent cells detected is, the higher is the possibility that UEl is faraway from the base stations of the adjacent cells, and thus the lower is the interference between UEl 's P2P communication link and conventional links in adjacent cells if the primary frequency of the adjacent cells is taken as UEl 's P2P communication frequency. The lower the strength of P2P signals detected is, the higher is the possibility that UEl is faraway from the pairs of P2P communicating UEs, and thus the lower is the interference between UEl and the pairs of P2P communicating UEs if the candidate frequencies used by the pairs of P2P communicating UEs are taken as UEl' s P2P communication frequency.

UEl sends the ranked candidate frequencies as the detection result to UTKAN (step S60). Admittedly, UEl can also send the strength of the signals detected using these candidate frequencies as the detection result to UTRAN directly. Furthermore, UEl can also send its location information to UTRAN if possible, to be taken as a reference when UTRAN determines the P2P communication frequency suitable for UEl.

Upon receipt of the above detection result provided by UEl, UTRAN checks the current operation status of the communication network, that is, current usage of all candidate frequencies. According to the detection result provided by UEl in conjunction with the current operation status of the communication network, UTRAN selects a suitable frequency as UEl 's frequency for P2P communication (step S70). For example, from the current usage of candidate frequencies it can be known that F3 should be excluded from being UEl 's P2P communication frequency among the candidate frequencies for UEs to carry out P2P communication in Al if the number of UEs selecting F3 as P2P communication frequency in Al is above the predefined threshold.

When determining UEl 's P2P communication frequency, UTRAN can also refer to UEl 's notified location information such as UEl 's location information obtained by UEl through GPS, to determine P2P communication frequency for UEl. For example, according to UEl 's location information, F4 should be excluded from being UEl 's P2P communication frequency as much as possible if other UEs are using F4 to perform P2P communication around UEl .

After a suitable P2P communication frequency (usually the candidate frequency whose signal strength is the weakest) is selected for UEl according to the detection result notified by UEl in conjunction with the current usage of candidate frequencies and UEl 's location information likely obtained, UTRAN sends the selected frequency to UEl and updates the present frequency usage information of the communication network (step S80). In the above embodiment of the present invention, UTRAN should choose the frequency whose signal strength is the weakest as UEl 's P2P communication frequency from F5, F6, F7, F9 and FlO as possible as it can on the premise that Fl, F2 and F8 have been excluded and F3 and F4 have been excluded as possible as it can. Upon receipt of the suitable frequency sent from UTRAN, UEl establishes P2P communication link with another UE using this frequency (step S90).

After UEl completes P2P communication using this P2P communication frequency, UEl sends a request for releasing the P2P communication frequency it uses to UTRAN (step SlOO). After receiving the release request, UTRAN reclaims the P2P communication frequency and updates the current frequency usage information of the communication network (step SI lO).

In the above embodiment, UEl in Al is taken as an example to describe the procedure as how UEl in online P2P communication mode obtains P2P communication frequency, which is also applicable to the case where a UE to adopt offline P2P communication mode in a cell obtains P2P communication frequency via UTRAN first and then performs offline P2P communication.

When UEl in Al attempts to perform offline P2P communication, it can choose offline P2P communication frequency independently besides obtaining P2P communication frequency via UTRAN. During the independent selecting procedure, UEl first obtains candidate frequencies that are broadcasted by UTRAN and can be used for the UEs in Al to carry out P2P communication. But different from the above steps, after UEl searches signals according to the candidate frequencies and ranks the signal strength corresponding to the candidate frequencies, the process doesn't go to step S60 afterwards,. ^: but goes to a step where the candidate frequency corresponding to the signal with the weakest strength detected from the ranked candidate frequencies is determined as the suitable frequency for P2P communication and P2P communication is initiated with another UE using the suitable frequency.

In practical applications, when UEl falls within the cell, for offline P2P communication, whether to determine UEl 's P2P communication frequency via UTRAN or by UEl itself is determined by the P2P communication parameter broadcasted via UTRAN. As to the P2P communication parameter, full descriptions are disclosed in the patent application filed by KONINKLIJKE PHILIPS ELECTRONICS N.V., Attorney's Docket No. CN040035, along with the present application and incorporated herein as reference. If there is no explicit indication in the P2P communication parameter, it can be decided by UEl itself or through negotiation with UTRAN when UEl registers offline P2P communication. IfUEl falls outside the network coverage area of Al, UEl itself can decide the frequency for offline P2P communication. In this case, UEl can take advantage of the candidate frequencies obtained via BCCH before leaving the network coverage area or those obtained when registering offline P2P communication service and stored in UEl 's SIM card, to detect the strength of the pilot signals corresponding to the candidate frequencies and that of the signals of the ongoing P2P communication, and choose the candidate frequency corresponding to the weakest signal strength detected (the candidate frequency corresponding to the weakest signal strength is also likely to be the candidate frequency whose signal has not been not found) as the offline P2P communication frequency, thus to mitigate and avoid interference with other UEs in offline P2P communication during P2P communication.

The above dynamic frequency reuse method for P2P communication is applicable to the case where the planned frequency reuse factor is above 1, and also applicable to the case where the frequency reuse factor is equal to 1 but different frequencies are used in different sectors within the same cell. In the latter case, a different frequency can be selected for the UE in a sector to perform P2P communication dynamically from the frequencies allocated in the adjacent sectors, which is similar to the above method.

The above dynamic frequency reuse method for P2P communication can be applied in P2P communication between two UEs, and equally can be applied in multi-cast communication between a sending terminal and multiple receiving terminals and direct communication between two UEs in any hop of a multi-hop communication.

The above dynamic frequency reuse method for P2P communication as proposed in the present invention can be implemented in software or hardware, or in combination of both. Fig.6 is the block diagram illustrating architecture of the UE and network system in a procedure where the UE performs P2P communication based on the P2P communication frequency acquired from the network system in accordance with an embodiment of the present invention, wherein components same as those in conventional network system and UE are not shown in Fig. 6. As shown in Fig.6, the communication network system UTRAN 100 comprises: a determining unit 120, for determining candidate frequencies useable for P2P communication of each cell according to the frequency planning information and radio resource management policy of the communication network. Wherein, excluding unit 122, for excluding the frequencies for conventional communication in a cell from the frequencies allocated to the communication network according to the frequency planning information, and excluding those frequencies that can't be used for UEs in the cell to perform P2P communication according to the radio resource management policy information so as to determine the remained frequencies allocated to the communication network as said candidate frequencies that can be used for the UEs in the cell to perform P2P communication.

Sending unit 130 in UTRAN sends the candidate frequencies decided by determining unit 120 to UE 1 via BCCH.

After receiving unit 10 in UEl receives the candidate frequencies, detecting unit 20 detects the strength of the signals using the candidate frequencies, wherein, the signals of the candidate frequencies include: pilot signals in adjacent cells and P2P communication signals in the cell where UEl camps. Through sending unit 30, UEl notifies UTRAN of the detection result.

After receiving the detection report from UEl, receiving unit 150 in UTRAN provides the detection report to selecting unit 124. According to the detection report, selecting unit 124 selects a suitable frequency from the candidate frequencies in conjunction with the current usage of the candidate frequencies checked by checking unit 140, and sends the suitable frequency to UEl via sending unit 130, so that UEl can perform P2P communication using the suitable frequency.

Upon receipt of the suitable frequency from UTRAN, receiving unit 10 in UEl provides it to P2P communicating unit 40 so as to carry out P2P communication with another UE. Furthermore, UEl also comprises a determining unit 50, for determining the candidate frequency corresponding to the weakest signal strength as the suitable frequency for P2P communication according to the detection result of detecting unit 20, and providing the P2P communication frequency to P2P communicating unit 40, which then performs P2P communication with another UE using the suitable frequency UEl provides. ADVANTAGEOUS EFFECTS OF THE INVENTION

With regard to the detailed description to the embodiments of the present invention taken in conjunction with accompanying drawings, it can be seen that: with the dynamic frequency reuse method as proposed in the present invention, the communication network system can dynamically choose a suitable frequency for the UE in the cell to perform P2P communication according to the management policy information, strength of pilot signals of adjacent cells the UE detects, strength of P2P communication signals in the serving cell of the UE and frequency usage of the communication network, so that P2P communication and conventional UPLINK-DOWNLINK communication use different frequencies in the coverage of the serving cell of the UE. Thus, interference between P2P communication and conventional communication sharing the same frequency can be mitigated effectively. Further, with regard to the dynamic frequency reuse method as proposed in the present invention, P2P interference between pairs of P2P communicating UEs caused by reusing frequency is also taken into consideration when selecting P2P communication frequency for the UE. Therefore, using the P2P communication frequency as provided in the method of the present invention, interference between pairs of P2P communicating UEs within the radio range of P2P communication can be avoided and lowered as much as possible no matter inside or outside the coverage area of the communication network and no matter in online or offline P2P communication mode.

Moreover, with regard to the dynamic frequency reuse method as proposed in the present invention, a UE can establish P2P communication link using the dynamically obtained reused frequency and it's not necessary for the network system to allocate new frequency resource for it, thus the capacity of the communication network can be further improved with the dynamic frequency reuse method provided in the present invention.

It is to be understood by those skilled in the art that the proposed dynamic frequency reuse method and apparatus for P2P communication can be applied in the P2P communication between two UEs, and equally applicable to multi-cast communication between a sending terminal and multiple receiving terminals and direct communication between two UEs in any hop of the multi-hop communication.

It is to be understood by those skilled in the art that the dynamic frequency reuse method and apparatus for P2P communication as disclosed in this invention can be made of various modifications without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

CLAIMS:

1. A dynamic frequency reuse method for use in P2P communication to be executed in a communication network system, comprising steps of: (a) determining a group of candidate frequencies for use in P2P communication in a cell according to a predefined radio resource management scheme of the communication network;

(b) sending the group of candidate frequencies to a UE in the cell so that the UE can detect strength of signals using the group of candidate frequencies, thus to determine a frequency for the UE to carry out P2P communication.

2. The dynamic frequency reuse method according to claim 1, wherein the predefined radio resource management scheme includes frequency planning information and radio resource management policy information of the communication network.

3. The dynamic frequency reuse method according to claim 2, wherein step (a) includes:

(al) excluding frequencies used for conventional communication in said cell from frequencies allocated to the communication network according to said frequency planning information;

(a2) excluding frequencies that can't be used for P2P communication by UEs in said cell according to said radio resource management policy information;

(a3) determining remained frequencies allocated to the communication network as said group of candidate frequencies that can be used for P2P communication by the UEs in said cell.

4. The dynamic frequency reuse method according to claim 1 or 2, wherein said communication network system sends said group of candidate frequencies to said UE via broadcasting channel.

5. The dynamic frequency reuse method according to claim 4, further comprising:

(c) receiving a detection report from said UE, the detection report including the strength of the signals using said group of candidate frequencies that said UE detects;

(d) determining a suitable frequency from said group of candidate frequencies according to the detection report;

(e) sending the suitable frequency to said UE so that said UE can perform P2P communication using the suitable frequency.

6. The dynamic frequency reuse method according to claim 5, wherein step (d) further comprising: checking current usage of said group of candidate frequencies; determining said suitable frequency according to the checking result.

7. The dynamic frequency reuse method according to claim 5, wherein step (d) further comprising: determining said suitable frequency according to location information of said UE obtained through receiving location report from said UE.

8. The dynamic frequency reuse method according to claim 4, further comprising: receiving a message from said UE for releasing said suitable frequency; reclaiming said suitable frequency according to the releasing message.

9. A dynamic frequency reuse method for use in P2P communication to be executed in a UE(user equipment), comprising steps of: receiving a group of candidate frequencies for the UE to perform P2P communication sent from a communication network system, wherein the group of candidate frequencies is determined by the communication network system according to frequency planning information and radio resource management policy information; detecting strength of signals using said group of candidate frequencies, to determine a frequency for the UE to perform P2P communication.

10. The dynamic frequency reuse method according to claim 9, wherein said signals using said group of candidate frequencies include pilot signals of adjacent cells and P2P communication signals in a cell where the UE camps.

11. The dynamic frequency reuse method according to claim 9 or 10, further comprising: sending the detection result to said communication network system; receiving a suitable frequency sent from said communication network system, the suitable frequency is determined from said group of candidate frequencies by said communication network system according to the detection result; performing P2P communication with another UE using the suitable frequency.

12. The dynamic frequency reuse method according to claim 11, further comprising: sending a location report to said communication network system so that said communication network system can determine said suitable frequency according to the location report.

13. The dynamic frequency reuse method according to claim 9 or 10, further comprising: determining a candidate frequency corresponding to the weakest signal strength in said group of candidate frequencies as the suitable frequency for the UE to perform P2P communication, according to the detection result; performing P2P communication with another UE using the suitable frequency.

14. A communication network system, comprising: a determining unit, for determining a group of candidate frequencies for use in P2P communication in a cell according to a predefined radio resource management scheme of the communication network; a sending unit, for sending the group of candidate frequencies to a UE(user equipment) in the cell so that the UE can detect strength of signals using the group of candidate frequencies, thus to determine a frequency for the UE to carry out P2P communication.

15. The communication network system according to claim 14, wherein said determining unit includes: an excluding unit, for excluding frequencies used for conventional communication in said cell from frequencies allocated to the communication network according to said frequency planning information; and excluding frequencies that can't be used for P2P communication by UEs in said cell according to said radio resource management policy information; and determining remained frequencies allocated to the communication network as said group of candidate frequencies that can be used for P2P communication by the UEs in said cell.

16. The communication network system according to claim 15, further comprising: a receiving unit, for receiving a detection report from said UE, the detection report including the strength of the signals using said group of candidate frequencies said UE detects; a selecting unit, for determining a suitable frequency from said group of candidate frequencies according to the detection report; wherein said sending unit sends the suitable frequency to said UE so that said UE can perform P2P communication using the suitable frequency.

17. The communication network system according to claim 16, further comprising: a checking unit, for checking current usage of said group of candidate frequencies; wherein said selecting unit determines said suitable frequency according to the checking result.

18. A UE(user equipment), comprising: a receiving unit, for receiving a group of candidate frequencies for the UE to perform P2P communication sent from a communication network system, wherein the group of candidate frequencies is determined by the communication network system according to frequency planning information and radio resource management policy information; a detecting unit, for detecting strength of signals using the group of candidate frequencies, to determine a frequency for the UE to perform P2P communication.

19. The UE according to claim 18, wherein said signals using said group of candidate frequencies include pilot signals of adjacent cells and P2P communication signals in a cell where the UE camps.

20. The UE according to claim 19, further comprising: a sending unit, for sending the detection result to said communication network system; wherein said receiving unit receives a suitable frequency sent from said communication network system, the suitable frequency is determined from said group of candidate frequencies by said communication network system according to the detection result; and the UE further includes: a P2P communicating unit, for performing P2P communication with another UE using the suitable frequency.

21. The UE according to claim 19, further comprising: a determining unit, for determining a candidate frequency corresponding to the weakest signal strength in said group of candidate frequencies as the suitable frequency for the UE to perform P2P communication, according to the detection result; a P2P communicating unit, for performing P2P communication with another UE using the suitable frequency.