CN1768547A - Method and apparatus for supporting P2P communication in TDD CDMA communication system - Google Patents

Abstract

A method for supporting P2P communication between two user equipments in TDD CDMA systems, performed by user equipment, comprising: receiving signals transferred via the downlink control channel from network system; acquiring the timeslot allocation information and the spreading code allocation information of other active user equipments allocated in the specific downlink timeslot associated with the direct link used by said user equipments, according to the received signals; and synchronizing the P2P communication signals received by the user equipment and signals from network system, according to the acquired timeslot allocation information and spreading code allocation information, so as to reduce the interference caused by the downlink signals transmitted from network system to other user equipments during the P2P communication process.

Description

Method and device for supporting P2P communication in TDD CDMA communication system

technical field

The present invention relates to a method and device for supporting P2P (point-to-point) communication in a TDD CDMA (Time Division Duplex Code Division Multiple Access) communication system, and in particular to a method and device for reducing user terminals performing P2P in a TDD CDMA communication system. Method and apparatus for interference from conventional communication signals encountered during communication.

technical background

In the traditional cellular mobile communication system, a user terminal must communicate with another user terminal through the relay of the base station. Even if the two user terminals are very close to each other, the relay of the base station is still required to communicate with each other. In Figure 1 This traditional communication pattern is shown in . However, in some cases, such as when two user terminals residing in the same cell are very close to each other, it should be a more reasonable choice for the two user terminals to communicate directly without the relay of the base station, which is the so-called P2P communication.

Figure 2 shows a P2P communication between two user terminals. As shown in Figure 2, assuming that both user terminals reside in the same cell and the distance between them satisfies the conditions for establishing a P2P link, the dotted line in the figure indicates the signaling link between UTRAN and the user terminal during P2P communication , while the solid line indicates the data link between the user terminals, and the arrows of the dotted line and the solid line indicate the direction of information flow. Obviously, it can be seen from the figure that there is only a signaling link between UTRAN and a user terminal, and only a data link between two user terminals. If some extra signals for management are ignored, then the use of P2P communication can save 50% of wireless resources in the process of direct communication. In addition, since there is a control channel between the UTRAN and the user terminal, during the P2P communication, the operator of the wireless network can still control the use of the radio frequency by the user terminal through the base station.

Time Division Duplex (TDD) air interface is a communication standard that is generally considered in the field of communication to be able to flexibly adapt to different service requirements of uplink and downlink. In the third generation communication system adopting the TDD communication mode, the TD-SCDMA communication system becomes more suitable for combining P2P communication and An ideal communication system combining traditional communication modes.

In the TD-SCDMA communication system that can adopt the P2P communication mode, in addition to the two operating modes defined in the traditional TD-SCDMA communication system: idle mode and connected mode, a direct mode is also introduced to describe the connection between two user terminals. direct communication between. A communication link in direct mode can be defined as a forward (FORWARD) link (for example: user terminal UE1 to user terminal UE2 Link between) and backward (BACKWARD) link (for example: link between user terminal UE2 and user terminal UE1). Since the P2P communication mode is established in conjunction with the existing TD-SCDMA communication system, during direct communication, UTRAN and other traditional user terminals allocated in the same time slot with the user terminal in P2P communication can overhear the forward link Or the information transmitted in the reverse link, that is: because P2P communication has changed the UP-UTRAN-DOWN communication mode in the traditional TD-SCDMA communication system, from the perspective of UTRAN, even if the user terminal is not connected to UTRAN, the forward link The reverse link is also related to a specific uplink time slot or downlink time slot (according to different resource allocation schemes, the forward link and reverse link correspond to different uplink time slots or downlink time slots) time slot), so P2P communication will cause signal interference to traditional communication. By the same token, since during P2P communication, two user terminals performing P2P communication can also overhear the signal transmitted in the uplink time slot or downlink time slot related to their forward link or reverse link, therefore, When the traditional link and the P2P link share the same time slot, the traditional uplink or downlink communication will interfere with the P2P forward link or reverse link communication, which will seriously reduce the performance of the TDD CDMA communication system using the P2P communication mode. performance.

In order to improve the performance of the TD-SCDMA communication system using the P2P communication mode, it is necessary to effectively eliminate these signal interferences brought by the introduction of the P2P communication mode to the TD-SCDMA communication system.

In the following, the interference signal brought by the introduction of the P2P communication mode will be analyzed first, and then how to eliminate the interference signal will be described. For the convenience of analysis and discussion below, the time slot for transmitting a signal from one user terminal to another user terminal via the above-mentioned forward link or reverse link is now referred to as a transmission time slot, and the user terminal is referred to as a transmission time slot via the forward link. The time slot for receiving signals from another user terminal on the road or reverse link is called a receive time slot, and the transmit time slot and receive time slot are respectively related to an uplink time slot or a downlink time slot in a subframe of traditional communication. Gap related.

1. Interference related to uplink timeslot between P2P link and legacy link

Figure 3 shows the mutual interference between P2P and traditional links in the TD-SCDMA communication system where P2P communication is introduced when the P2P link is related to the uplink time slot. As shown in FIG. 3 , it is assumed that user terminals UE1 and UE2 work in a P2P communication mode, and user terminal UE3 works in a traditional communication mode. Wherein, the transmitting time slot of UE1 is related to the uplink time slot of UE3, that is, UE1 and UE3 are allocated to send signals to UE2 and UTRAN respectively in the same uplink time slot. S1 is the P2P link information transmitted by the user terminal UE1 to the user terminal UE2 via the direct link (referred to here as the forward link), and S2 is the uplink information transmitted by the user terminal UE3 to the UTRAN via the uplink. S1 and S2 have different spreading codes.

In the TD-SCDMA communication system, maintaining the synchronization of the uplink is one of the most important features, because only when signals from different user terminals arrive at UTRAN at the same time, can it be ensured that the signals received by UTRAN are transmitted via the main path of different user terminals The spreading codes of the signals are orthogonal. For traditional communication systems, in connection mode, UTRAN monitors and controls the uplink transmission time of user terminals according to the specific signal burst structure to keep the uplink synchronization of each user terminal; however, for P2P communication mode, due to the UTRAN It only participates in the P2P link establishment process and does not participate in the P2P communication process after the P2P link establishment. Therefore, during the P2P communication period, the two user terminals participating in the P2P link have no dedicated channel to connect with UTRAN. In this case, even if UTRAN can By listening to and estimating the uplink synchronization offset of the two user terminals in the P2P link, the UTRAN has no way to use a specific signal burst to adjust the synchronization advance of the two user terminals in the P2P communication. To maintain uplink synchronization with UTRAN.

Specifically in Figure 3, when user terminals UE1 and UE3 transmit signals in the same allocated uplink time slot, UTRAN can overhear the information S1 sent from user terminal UE1 to UE2 (for UTRAN, S1 can be regarded as an interference signal I1), but as mentioned above, since there is no dedicated channel between UTRAN and user terminal UE1, even if UTRAN overhears S1 information and can estimate the synchronization offset information of UE1, the traffic burst in the traditional communication mode cannot be utilized. This means that the user terminal UE1 working in the P2P communication mode may lose uplink synchronization with UTRAN (the user terminal UE3 working in the traditional communication mode can maintain uplink with UTRAN through the traditional mode) Link synchronization), that is to say, I1 and S2 may not be able to reach the UTRAN synchronously, which will potentially damage the synchronization of the uplink, resulting in a decrease in system performance.

In the same way, when user terminals UE1 and UE3 transmit signals in the same allocated uplink time slot, user terminal UE2 can also overhear the signal S2 sent by user terminal UE3 to UTRAN (for user terminal UE2, S2 can be regarded as Interference I2), the interference signal I2 also affects the reception of S1 by the user terminal UE2, which may potentially damage the quality of the P2P communication.

2. Interference related to downlink time slot between P2P link and legacy link

Figure 4 shows the mutual interference between P2P and traditional links in the TD-SCDMA communication system where P2P communication is introduced when the P2P link is related to the downlink time slot. As shown in FIG. 4 , it is assumed that user terminals UE1 and UE2 work in a P2P communication mode, and user terminal UE3 works in a traditional communication mode. Wherein, the receiving time slot of UE1 is related to the downlink time slot of UE3, that is, UE1 and UE3 are assigned to receive signals from UE2 and UTRAN in the same downlink time slot respectively. S3 is the P2P link information from UE2 received by UE1 and transmitted via the direct link (referred to here as reverse link), and S4 is the downlink information from UTRAN received by UE3 via the downlink. Information, S3 and S4 have different spreading codes.

In FIG. 4, the downlink information S4 sent by UTRAN to UE3 will cause interference to other UEs receiving signals in the same time slot as UE3 but using different spreading codes. This interference is also called Multiple Access Interference (MAI).

Specifically in Fig. 4, when user terminal UE1 and user terminal UE3 receive signals in the same assigned downlink time slot, user terminal UE1 can overhear the information S4 sent by UTRAN to user terminal UE3 via downlink (for user terminal UE1 In general, S4 can be regarded as an interference signal I4), and generally the signal from UTRAN has a strong transmission power, therefore, the interference signal I4 may seriously damage the quality of direct communication.

In the same way, when user terminal UE1 and user terminal UE3 receive signals in the same assigned time slot, user terminal UE3 can also overhear the information S3 sent by user terminal UE2 to user terminal UE1 (for user terminal UE3, S3 It can be regarded as the interference signal I3, at this time, the user terminal UE2 can be regarded as a pseudo UTRAN transmitting information in the downlink time slot), the interference signal I3 will damage the user terminal UE3 and the same user terminal located near the user terminal UE2 The communication quality of other user terminals that receive signals in the same time slot as the user terminal UE2 is the same as that of UE3.

3. Interference between two P2P link pairs

Figure 5 shows the interference between two P2P link pairs in the TD-SCDMA communication system using the P2P communication mode, where the user terminal in one of the two P2P link pairs is connected to the other P2P link pair The user terminals in receive or transmit signals in the same allocated time slot. As shown in FIG. 5 , it is assumed that user terminals UE1 and UE2 work in one P2P link pair, and user terminals UE3 and UE4 work in another P2P link pair.

Due to the symmetry of the P2P link, in the relevant time slot, a signal S5 or S6 from user terminal UE1 to user terminal UE2 will become an interfering signal I5 or I6 for user terminal UE4 which is receiving a signal from user terminal UE3. Obviously, interfering signals I5 or I6 may also greatly impair the quality of direct communication.

To sum up, it can be seen that after the P2P link is introduced into the traditional TD-SCDMA communication system, there are 6 possible interference signals in the communication system: I1, I2, I3, I4, I5 and I6. According to whether these interference signals will involve UTRAN, the above 6 types of interference signals can be divided into two categories. The first category is interference between user terminals, such as I2, I3, I5 and I6; the second category is interference involving UTRAN. , such as I1 and I4.

In order to ensure the communication quality of the TD-SCDMA communication system with P2P communication mode, it is necessary to study effective methods to eliminate the above six kinds of interference (preferably without changing the physical layer of the current communication system). Among the 6 kinds of interference signals analyzed above, by effectively limiting the wireless communication range supported by P2P and adopting intelligent wireless resource control strategies, the first type of interference can be reduced or eliminated, namely I2, I3, I5 and I6; Regarding the interference signal I1 in the second type of interference, the applicant submitted on March 7, 2003 is Royal Philips Electronics Co., Ltd., the applicant's file number is CN030004, and the application number is 03119894.5. The method and device for uplink synchronization maintenance of peer-to-peer communication" patent application describes in detail the method and device for eliminating the interference signal I1, and hereby inserts the content disclosed in the application; however, for For the interference signal I4 in the second type of interference, no effective solution has been proposed so far.

From the above analysis of the interference signal, it can be known that the interference signal I4 is the interference signal brought to the user terminal UE1 receiving the signal in the same downlink time slot as the user terminal UE3 when the UTRAN transmits the signal to the user terminal UE3 via the downlink. Usually, the transmission power of the signal sent by UTRAN is high (high enough to be heard by all user terminals sharing the same downlink time slot in the same cell), and the signal is a signal that includes many other user terminals The mixed signal of redundant information, so I4 usually cannot be ignored. In the user terminal UE1, the method of multi-user detection or joint detection must be adopted to eliminate the interference signal to ensure the quality of direct communication.

Contents of the invention

The purpose of the present invention is to provide a method and device for supporting P2P communication in the TDD CDMA communication system, so as to effectively reduce the time-consuming downlink with the user terminal in the same downlink as the user terminal in the traditional communication process received by the user terminal during the direct communication process. Interference with downlink signals transmitted in slots.

In order to realize the purpose of the present invention, a method for supporting the user terminal to carry out P2P (point-to-point) communication with another user terminal carried out by a user terminal in a TDD CDMA communication system according to the present invention comprises steps: Receive the signal transmitted by the network system through the downlink control channel; obtain time slot allocation information according to the received signal; obtain other working state allocated in a specific downlink time slot according to the received signal Spreading code allocation information of the user terminal, wherein the specific downlink time slot is: the downlink time slot used by the user terminal for signal reception via a direct link between it and the other user terminal; And according to the obtained time slot allocation information and the spreading code allocation information, the interference caused by the network system transmitting downlink signals to other user terminals received by the user terminal during the P2P communication process is reduced.

According to a method for supporting P2P communication between two user terminals performed by a network system in a TDD CDMA communication system according to the present invention, the method includes the steps of: via a downlink control channel, sending to two P2P communication The user terminal sends time slot allocation information; generates spreading code allocation information corresponding to each downlink time slot in the time slot allocation information; and sends the two user terminals respectively via a downlink control channel. Spreading code allocation information, so that the signal of P2P communication received by each of the two user terminals is synchronized with the signal from the network system.

Brief description of the drawings

FIG. 1 is a schematic diagram of two user terminals communicating via a relay of a base station in a traditional communication mode;

FIG. 2 is a schematic diagram of using a P2P communication mode between two user terminals;

Fig. 3 is in the TD-SCDMA system that introduces P2P communication mode, the schematic diagram that adopts the interference signal generation between the conventional link and the direct link of uplink time slot communication;

Fig. 4 is in the TD-SCDMA system that introduces P2P communication mode, the schematic diagram that adopts the interference signal generation between the conventional link and the direct link of downlink time slot communication;

Fig. 5 is in the TD-SCDMA system that introduces P2P communication mode, the schematic diagram that mutually produces interference signal between two direct link pairs;

Fig. 6 is a schematic diagram of time slot allocation information adopted by the present invention;

Fig. 7 is a schematic diagram of spreading code allocation information adopted by the present invention;

FIG. 8 is a schematic diagram of the time relationship of receiving downlink signals from the base station and UE2 at the user terminals UE2 and UE1, respectively, using the UTRAN as the time reference point when the downlink time slot is used for communication;

Fig. 9 is a flow chart of a method for enabling downlink synchronization of a receiving user terminal in direct mode performed by the present invention.

Detailed description of the invention

According to the above analysis of the interference signal in the TD-SCDMA communication system that introduces the P2P communication mode, the present invention mainly focuses on solving the problem of the interference signal from the downlink of the traditional base station received by the receiving user terminal undergoing P2P communication.

In fact, in the base station subsystem (UTRAN) of the TD-SCDMA communication system, an advanced receiver is adopted, that is, the method of multi-user detection or joint detection is used to eliminate multiple access interference. In an article by S. Moshavi entitled "Multiuser Detection for DS-CDMA Communications" disclosed in IEEE Communications Magazine, pp. 124-136, October 1996 and in IEEE Transactions on Vehicular Technology, May 1996 Disclosed in Vol. 45, No. 2, pp. 276-287, by A. Klein, G.K. Kaleh, and P.W. Baier, entitled "Zero-forcing and minimum mean square error equalization for multiuser detection in code division multiple access channels There is a detailed description in the article of "Apparatus", and the technical content disclosed in the above-mentioned article is incorporated here by way of insertion. However, if the method of eliminating interference such as multi-user detection or joint detection is applied to the receiver of the user terminal, the following two conditions need to be met in advance:

1. Obtain the spreading code information of all user terminals in the working state allocated to the same time slot as the user terminal;

2. When the user terminal in the direct mode receives the signal from the direct link, it keeps synchronization with the related downlink signal from UTRAN, because only the signal synchronization can effectively reduce the complexity of receiver implementation.

In the following, the above two conditions will be discussed separately:

1. Obtain spreading code allocation information

In a communication system taking TD-SCDMA as an example, the spreading codes used by all user terminals in working mode are controlled by the base station subsystem UTRAN. In the communication process, radio frequency signals transmit information in the form of frames. Each radio frequency frame is divided into 2 subframes, and each subframe is composed of 7 time slots. Each user terminal allocated in the same time slot uses the time allocated by the base station subsystem. Different spreading codes, transmit or receive respective signals.

Since the downlink control channel, such as BCCH (Broadcast Control Channel), has a fixed position in each radio frame or subframe, and whether it is working in the traditional communication mode or in the P2P link mode, the user terminal can receive Information from the downlink control channel, therefore, the user terminal can obtain the spreading code assignment information of all user terminals sharing the same time slot with it according to the control information from the UTRAN transmitted via the downlink control channel.

Among them, the spreading code allocation information includes two parts: (i) in each frame or subframe, whether each time slot is used for uplink or downlink; Spreading code allocation information related to each downlink time slot.

In the embodiment of the present invention, the above-mentioned time slot allocation information and spreading code allocation information respectively adopt the mode of mapping, and relevant information is stored in the corresponding time slot allocation diagram and spreading code allocation diagram, specifically:

(1) About time slot allocation information

In the communication system taking TD-SCDMA as an example, each subframe contains 7 time slots, which are respectively marked as TS0-TS6. Therefore, in the time slot allocation diagram, only one eight-bit long byte can be used to achieve the same Mapping of 7 slots in a subframe.

Wherein, a time slot corresponds to a bit in a byte, as shown in FIG. 6 , time slots TS0-TS6 correspond to Bit6-Bit0 in a byte respectively, and Bit7 of a byte is reserved. For each bit in the byte Bit6-Bit0, it is assumed that: when its value is 1, it means that the time slot corresponding to this bit is used as a downlink time slot; when its value is 0, it means that it is associated with this bit The corresponding time slot is used as an uplink time slot. In the TD-SCDMA system, TS0 is always allocated for downlink and TS1 is always allocated for uplink. Therefore, the value of Bit6 in the byte is always 1, and the value of Bit5 is always 0.

(2) Spreading code allocation information related to each allocated downlink time slot

After the allocation of time slots in a radio frequency frame or subframe is completed, the base station subsystem (UTRAN) can generate corresponding extensions related to each allocated downlink time slot according to the downlink time slots contained in the subframe. For frequency code allocation information, the TD-SCDMA system is still taken as an example below.

In this communication system, a downlink time slot can have up to 16 spreading codes for different user terminals or different code channels of the same terminal, so in order to represent each spreading code in a downlink time slot In the case of usage, 16 bits are needed, namely: 2 bytes of eight bits long, to represent the spreading code allocation information. It can be seen from the foregoing that among the 7 time slots included in each subframe, TS1 is always used as uplink, so each subframe has at most 6 time slots used as downlink. Frequency code usage information requires a total of 12 octets long.

The spreading code allocation information included in one downlink time slot will be described below through a specific example. Assuming that in the time slot allocation diagram shown in Figure 6 above, bytes Bit4 and Bit1 are equal to 1, that is: TS2 and TS5 are used as downlink time slots, then in the corresponding spreading code allocation diagram shown in Figure 7 It shall contain 4 octets long, where: the two bytes of the first group correspond to the allocation information of each spreading code of the TS2 time slot, and the two bytes of the second group correspond to the allocation information of each spreading code of the TS5 time slot. Assignment information of spreading codes. The part with a lighter background color in Figure 7 is the first group of two bytes, from Bit15 to Bit0 respectively corresponding to the information of spreading codes Code15 to Code0 that can be used by up to 16 user terminals or code channels in the TS2 time slot and the darker part of the background is the second group of two bytes, which respectively correspond to the information of the spreading codes Code15 to Code0 that can be used by up to 16 user terminals or code channels in the TS5 time slot from Bit15 to Bit0. For the value of the bit corresponding to each spreading code in the total four bytes of the above two groups, the definition is as follows: when the value of the bit corresponding to the spreading code is 1, it means that the spreading code is in The corresponding time slot is being used by the user terminal; and when the value of the bit corresponding to the spreading code is 0, it means that the spreading code has not been allocated to the user terminal in the corresponding time slot, for example: when the first group When Bit8 and Bit0 in the two bytes are 1 and other bits are 0, it means that in the time slot TS2 corresponding to the first group, only the spreading code corresponding to Bit8 and Bit0 is being used by the user terminal, while Other spreading codes have not been assigned to user terminals yet.

As described above, by mapping the allocation information of each time slot of the subframe and the allocation information of each spreading code contained in each downlink time slot in the subframe to the time slot allocation map and the spreading code allocation map respectively, the base station subframe The system UTRAN can send the information contained in the time slot allocation map and spreading code allocation map to each user terminal via the downlink control channel, so that the user terminal obtains the time slot allocation information and related downlink time slot spread spectrum Code allocation information.

Of course, if necessary, the user terminal can also use a method similar to the above to acquire time slot allocation information and spreading code allocation information related to uplink time slots.

2. A user terminal in direct mode maintains synchronization with the associated downlink signal from UTRAN when receiving the signal from the direct link

In the traditional TD-SCDMA system, if the effect of multipath delay is neglected, the downlink mixed signal sent by UTRAN should arrive at each user terminal synchronously; however, in the TD-SCDMA system introducing P2P communication, the The transmission paths of the useful signal S3 of the P2P communication user terminal and the interference signal I4 from UTRAN are very different, (see Figure 4), so the time when the signals S3 and I4 arrive at the user terminal UE1 will be different, that is, in the direct mode When the user terminal UE1 in receives the signal S3 from the direct link, it will not be able to guarantee synchronization with the downlink signal I4 from UTRAN. In this case, even if the user terminal UE1 can obtain the time slot allocation information and spreading code allocation information transmitted by the UTRAN from the downlink control channel, since the signals S3 and I4 do not arrive at the user terminal UE1 at the same time, although at this time The traditional joint detection method can still be used to eliminate the interference signal I4 in the user terminal UE1, but the complexity of channel estimation and joint detection implementation will be greatly increased due to time asynchronous reasons.

In order to greatly simplify the operation of the receiver in the user terminal UE1 and effectively eliminate the downlink interference signal I4, the synchronization between the direct link signal S3 and the interference signal I4 at the receiving user terminal UE1 becomes the key to ensure the quality of P2P communication. a necessary link.

It can be seen from Fig. 4 that in the case that the useful signal S3 and the interference signal I4 cannot reach the user terminal UE1 synchronously, there are two ways to make them reach the user terminal UE1 synchronously: one is to adjust the transmission signal (I4) of UTRAN Timing advance, so that the transmitted signal I4 and the signal S3 transmitted by the user terminal UE2 arrive at the user terminal UE1 synchronously. The second is to adjust the time advance of the transmitted signal (S3) of the user terminal UE2, so that the signal S3 transmitted by the user terminal UE2 and the The signal I4 transmitted by the UTRAN reaches the user terminal UE1 synchronously. Among them, the first method—adjusting the transmission timing advance of UTRAN so that I4 and S3 reach the user terminal UE1 synchronously is impossible to realize, because, in the communication process, there are usually multiple The P2P link pair of slots, and through a common signal timing advance (TA) transmitted by UTRAN, the downlink interference signal I4 is synchronized with the signals (such as S3) received by all these user terminals in P2P communication, Therefore, it is necessary to adjust the timing advance of the useful signal S3 at the user terminal UE2, so as to ensure that each user terminal in the direct mode maintains the same signal from the different direct links when receiving signals from different direct links. UTRAN related downlink signal synchronization.

Before describing the above synchronization process in conjunction with accompanying drawing 8, there are two points that need to be explained first:

(i) Establish and maintain synchronization with UTRAN by conventional means of communication

In the cell search phase, each user terminal first establishes downlink synchronization with UTRAN in the traditional communication way, and then tracks the pilot channel in the subframe and uses the detected pilot channel as the Time reference to maintain downlink synchronization with UTRAN.

(ii) In P2P communication mode, keep synchronized with the associated downlink time slot

When the user terminal UE2 and UE1 are in the direct mode of P2P communication, there is a dedicated channel between UE2 and UE1, and the traffic burst structure of the dedicated channel is different from that of the dedicated channel in the traditional TD-SCDMA communication system Likewise, this means that the power control information and synchronization offset information are also included in the forward and reverse link traffic bursts of the dedicated channel of the P2P link. In the traditional TD-SCDMA communication system, the synchronization offset information contained in the traffic burst can be used to keep the uplink signal synchronization at UTRAN. Similarly, in P2P communication, the traffic burst contained in the direct link The synchronization offset information transmitted can also be used by P2P user terminals to maintain synchronization with the associated legacy downlink when receiving direct link signals.

It can be known from the above two points that since at the beginning of communication establishment (cell search stage), each user terminal has established synchronization with the downlink of UTRAN in a traditional way, so when establishing P2P communication, two user terminals can have A common time reference point to further determine the synchronization of the direct link signal and the downlink signal; at the same time, since the business burst of the P2P dedicated channel contains the same synchronization offset information as the traditional method, the P2P establishment and During the communication process, the user terminal can use the synchronization offset information to set and adjust the timing advance of its transmitted signal, so as to ensure the synchronization of the direct link signal and the downlink signal.

The process of ensuring the synchronization of the direct link signal and the downlink signal at the receiving user terminal will be described below with reference to FIG. 8 and FIG. 4. Here, it is assumed that for the user terminal UE1, the useful signal S3 and the interference signal I4 share the same downlink Link slot.

Firstly, UTRAN is taken as a common reference point, and the time relationship between the time when each user receives a signal and the common time reference point in UTRAN is shown in FIG. 8 . In FIG. 8, T0 is the downlink transmission time reference point at UTRAN in the relevant downlink time slot, and T1 and T2 are the reception time points when signals are received at user terminals UE1 and UE2 respectively, as described above As mentioned above, user terminals UE1 and UE2 can identify T1 and T2 by discovering and tracking the pilot channel from UTRAN. The time period T _URTAN-UE2 (with a value equal to T2-T0) and the time period T _URTAN-UE1 (with a value equal to T1-T0) are transmission times of signals transmitted from UTRAN to UE2 and UE1, respectively. T _UE2-UE1 (its value is equal to T21-T2) is the time period between the assumption that user terminal UE2 sends a test signal to UE1 at time T2 and the test signal arrives at UE1 at time T21 and the time point T1 when the conventional base station signal arrives at UE1 , here, in order to ensure that the useful signal S3 and the interference signal I4 arrive at the UE1 at the same time, the time T21 should coincide with the time T1.

Then, the user terminal UE1 calculates the timing advance by estimating the channel impulse response of each training sequence transmitted by UE2, and includes the calculated timing advance as synchronization offset information in the transmission from the user terminal UE1 to the user terminal UE2. business emergencies. Since the training sequence used to measure the timing advance is included in the traffic burst, even if both UEs are in a moving state, UE1 and UE2 can estimate and adjust the timing advance of the transmitted signal at any time.

The above-mentioned traditional downlink synchronization process for the direct link mainly includes the following steps:

(1) UE1 and UE2 respectively establish and maintain downlink synchronization with UTRAN

User terminals UE1 and UE2 establish downlink synchronization during the cell search phase, and maintain downlink synchronization through tracking pilot channels (step 1).

(2) UE2 determines the time when it transmits the signal

In the process of establishing the direct link, the user terminal UE2 uses time T2 as the time to transmit a signal to the user terminal UE1 in the relevant downlink time slot, and transmits a signal to the user terminal UE1 at the time T2 in the downlink time slot. Emit a signal (step 2).

(3) UE1 measures the time difference between the direct link signal and the downlink signal

During the establishment of the direct link, when the user terminal UE1 receives the service burst sent by UE2 at T2, according to the training sequence information included in the service burst, calculate T _UTRAN-UE2 +T _UE2-UE1 -T _UTRAN-UE1 (T21-T1) time difference, and send the measurement result to the user terminal UE2 as feedback information (step 3).

(4) UE2 sets the timing advance of sending signals

The user terminal UE2 sets the time advance of its signal transmission according to the feedback information from the user terminal UE1, and adjusts the time of signal transmission of the user terminal UE2 according to the time advance. (step 4)

(5) UE1 estimates and sends synchronization offset information to UE2

User terminal UE1 calculates the synchronization offset information by estimating the channel impulse response of each training sequence transmitted by UE2, and sets the calculated synchronization offset information in the traffic burst sent from user terminal UE1 to user terminal UE2 , where the synchronization offset information based on the channel impulse response can be calculated according to the standard disclosed in the 3GPP TS 25.928, "1.28McpsUTRA TDD physical Layer" protocol, and the technical content disclosed in the standard is incorporated here by way of insertion. (step 5)

(6) UE2 adjusts the timing advance of sending signals

The user terminal UE2 adjusts the timing advance of its transmitted signal according to the synchronization offset information contained in the traffic burst from the user terminal UE1 (step 6).

(7) Repeat step 5 and step 6

Judging whether the P2P communication ends (step 7), if the direct communication has not ended yet, as long as the direct link is also relevant to the downlink time slot, that is: the direct link shares the same time slot with the downlink time slot, the Steps 5 and 6 above are repeatedly performed to ensure that the direct link signal S3 is synchronized with the associated downlink signal I4.

Through the above steps, the useful signal S3 from the user terminal UE2 and the interference signal I4 from the UTRAN can reach the receiving user terminal UE1 at the same time, so that the user terminal UE1 can use methods such as multi-user detection or joint detection to eliminate the downlink interference signal (I4) from UTRAN to ensure the communication quality of the TDD CDMA system that introduces P2P communication.

Of course, when the two UEs in the direct communication mode are very close to each other, that is, when UE1 and UE2 receive the signal from UTRAN at almost the same moment T1 and T2, the direct link signal S3 and the downlink The time difference between the arrival of the signal I4 at the user terminal UE1 is almost negligible. At this time, the above synchronization process can be omitted, and only the spreading code allocation information is needed, and the user terminal UE1 can eliminate the adverse effects of the interference signal I4 through joint detection.

In addition, it should be pointed out that the timing advance of the transmitted signal set and adjusted by the user terminal UE2 through the above steps can only ensure that the useful signal S3 and the interference signal I4 arrive at the user terminal UE1 at the same time, but cannot guarantee that the useful signal S3 and the interference signal I4 arrive at the user terminal UE1 at the same time, but cannot guarantee S4 and the interference signal I3 arrive at the user terminal UE3 at the same time. Therefore, in the user terminal UE3, its receiver cannot effectively eliminate the influence of the interference signal I3 in the user terminal UE3 according to the obtained spreading code allocation information (or use The asynchronous joint detection method eliminates the influence of I3 on the basis of increasing complexity). Fortunately, in actual communication, when the user terminal UE3 uses the traditional synchronous joint detection (JD) method to extract the desired information from S4, most of the interference it receives comes from the received mixed signal S4 At this time, the influence of the interference signal I3 on the useful signal S4 is negligible.

The above-mentioned method for supporting downlink timeslot P2P communication in the TD-SCDMA system of the present invention can be realized by computer software, computer hardware, or a combination of computer software and hardware.

Beneficial effect

To sum up, in the method and device for supporting P2P communication in the TD-SCDMA system provided by the present invention, since the user terminal in the direct communication mode can obtain the spreading code allocation information via the downlink, Therefore, the user terminal can use the spreading code allocation information that is being used by other user terminals in the same downlink time slot allocated to it, and adopt methods such as multi-user detection or joint detection to effectively eliminate the user terminal's interference during direct communication. interference from downlink signals transmitted in the same time slot as the user terminal in conventional communications.

In addition, since in the method and device for supporting P2P communication in the TD-SCDMA system provided by the present invention, the step of synchronizing the direct link signal and the downlink signal in the relevant time slot is adopted, greatly It simplifies the operation process of eliminating downlink signal interference at the user terminal according to the spreading code allocation information, and simplifies the hardware configuration of the user terminal receiver.

Although the present invention takes TD-SCDMA as an example to describe the method and device for supporting P2P communication in the TD-SCDMA system, those skilled in the art should understand that it should not be limited to the application in the TD-SCDMA system. The communication method and device are also applicable to other TDD CDMA systems.

Those skilled in the art should understand that the method and device for supporting P2P communication in a TDD CDMA system disclosed in the present invention can also be improved in various ways without departing from the contents of the present invention. Therefore, the protection scope of the present invention should be determined by the contents of the appended claims.

Claims (22)

1, a kind ofly in TDD cdma communication system, support this user terminal and another user terminal to carry out P2P (point-to-point) method for communicating, comprise step by user terminal being used to of carrying out:

The signal that reception is transmitted by downlink control channel by network system;

According to the signal that is received, obtain time slot allocation information;

According to the signal that is received, obtain the spreading code that is distributed in other the in running order user terminals in the specific downlink time slots and distribute information, wherein this specific downlink time slots is: employed downlink time slots when this user terminal carries out the signal reception via the direct link between it and this another user terminal; And

Distribute information according to this time slot allocation information that is obtained and this spreading code, the interference that when other user terminals transmit down link signals, brings from network system that reduces that this user terminal is subjected in the P2P communication process.

2, communication means as claimed in claim 1, wherein said spreading code distribute information to comprise the spreading code information of being used by other user terminals in the described downlink time slots at least.

3, communication means as claimed in claim 1 or 2, the step that wherein reduces interference signal are at least a methods of carrying out in Multiuser Detection (MUD) and the joint-detection (JD).

4, communication means as claimed in claim 3, at least a method in wherein said Multiuser Detection (MUD) and the joint-detection (JD) are to disturb by utilizing the spreading code information of being used by other user terminals in the described downlink time slots to reduce signal.

5, communication means as claimed in claim 4 also comprises step:

Carry out stage of Cell searching at this user terminal, set up the downlink synchronization with network system, and keep downlink synchronization with network system by following the tracks of pilot channel;

In described downlink time slots, when this user terminal transmitted via described direct link, the step of its execution comprised:

(i) in the process that described direct link is set up, according to receive from the time that network system transmitted, set this user terminal sends signal to this another user terminal in described downlink time slots time;

(ii) this time in described downlink time slots, send test massage to this another user terminal;

(iii) receive feedback signal from this another user terminal, this feedback signal be this another user terminal after receiving described test signal, will receive that time of this test signal and this another user terminal receive that the time that transmits from network system compares and the difference that obtains;

(iv), set this user terminal sends Timing Advance from signal to this another user terminal according to this feedback signal; And

(v) according to this Timing Advance, adjust this user terminal to the time that this another user terminal transmits, thereby make this another user terminal receive from the signal of the down link of network system and signal Synchronization from the described direct link of this user terminal.

6, communication means as claimed in claim 5 further comprises:

(, send the P2P signal of communication to this another user terminal vi) in described adjusted launch time;

(vii) receive synchronization shift information from this another user terminal, this synchronization shift information be this another user terminal after receiving described P2P signal of communication, according to this P2P signal of communication, the synchronisation offset that obtains of estimation; And

(, adjust this user terminal sends Timing Advance from signal to this another user terminal viii) according to this synchronization shift information.

7, as claim 5 or 6 described communication meanss, also comprise step: in the P2P communication period, according to synchronization shift information from this another user terminal, this user terminal is adjusted it to the time that this another user terminal transmits, thereby makes the P2P signal of communication of this user terminal emission and the downlink signal synchronization of network system emission arrive this another user terminal.

8, as claim 5,6 or 7 described communication meanss, wherein: in described downlink time slots, when this user terminal during via described direct link received signal, the step of execution comprises:

(a) in the process that described direct link is set up, when this user terminal is received described another user terminal to the detection signal of its transmission, poor from time that network system transmitted that this user terminal calculates that its time of receiving this detection signal receives with it, and the difference that calculates sent to this another user terminal as feedback signal.

9, communication means as claimed in claim 8, wherein: in described downlink time slots, when this user terminal during via described direct link received signal, the step of execution also comprises:

(b) in the process that described direct link is set up, when this user terminal is received the P2P signal of communication of this another user terminal emission, according to this P2P signal of communication, estimate the synchronization shift information of this another user terminal, and this synchronization shift information is sent to this another user terminal.

10, communication means as claimed in claim 8 or 9 also comprises step:

In the P2P communication period, according to P2P signal of communication, calculate the synchronization shift information of this another user terminal, and this synchronization shift information is sent to this another user terminal from described another user terminal.

11, a kind ofly in TDD cdma communication system, be used to be supported between two user terminals and carry out the P2P method for communicating, comprise step by what network system was carried out:

Via downlink control channel, to two user terminal sending time slots assignment information of carrying out P2P communication;

The corresponding spreading code of each downlink time slots distributes information in generation and this time slot allocation information; And

Via downlink control channel, send described spreading code respectively to these two user terminals and distribute information, so that the signal of the P2P that each user terminal in these two user terminals is received communication and signal Synchronization from this network system.

12, communication means as claimed in claim 11, wherein said spreading code distribute information to be included in the spreading code information of being used by other user terminals in the described downlink time slots at least.

13, a kind of user terminal that can carry out P2P (point-to-point) communication in TDD cdma communication system comprises:

A signal receiving/transmission device is used for receiving and sending wireless signal;

A time slot allocation information deriving means is used for obtaining time slot allocation information according to the information via the downlink control channel transmission;

A spreading code distributes information acquisition device, be used for according to information via the downlink control channel transmission, obtain the spreading code that is distributed in other the in running order user terminals in the specific downlink time slots and distribute information, wherein this specific downlink time slots is: employed downlink time slots when this user terminal carries out the signal reception via the direct link between it and another user terminal; And

A device that reduces interference signal, be used for distributing information the interference that when other user terminals transmit down link signals, brings from network system that reduces that this user terminal is subjected in the P2P communication process according to this time slot allocation information that is obtained and this spreading code.

14, user terminal as claimed in claim 13, wherein said spreading code distribute information to comprise the spreading code information of being used by other user terminals in the described downlink time slots at least.

15, as claim 13 or 14 described user terminals, at least a method that the device of wherein said reduction interference signal is carried out in Multiuser Detection (MUD) and the joint-detection (JD) reduces interference signal.

16, user terminal as claimed in claim 15, at least a method in wherein said Multiuser Detection (MUD) and the joint-detection (JD) are to disturb by utilizing the spreading code information of being used by other user terminals in the described downlink time slots to reduce signal.

17, user terminal as claimed in claim 16 also comprises:

A synchronizer is used for carrying out at this user terminal stage of Cell searching, sets up the downlink synchronization of this user terminal and network system, and keeps downlink synchronization with network system by following the tracks of pilot channel;

The time-setting mechanism that transmits, be used for process in described direct link foundation, according to receive from the time that network system transmitted, set this user terminal sends signal to this another user terminal in described downlink time slots time;

A test signal dispensing device is used for this time at described downlink time slots, sends test massage to this another user terminal;

A feedback signal receiving system, be used to receive feedback signal from this another user terminal, this feedback signal be this another user terminal after receiving described test signal, will receive that time of this test signal and this another user terminal receive that the time that transmits from network system compares and the difference that obtains;

A Timing Advance setting device is used for according to this feedback signal, sets this user terminal sends Timing Advance from signal to this another user terminal; And

The time adjusting device that transmits based on above-mentioned feedback signal, be used for according to this Timing Advance, adjust this user terminal to the time that this another user terminal transmits, thereby make this another user terminal receive from the signal of the down link of network system and signal Synchronization from the described direct link of this user terminal.

18, user terminal as claimed in claim 17 also comprises:

A synchronization shift information receiving system, be used to receive synchronization shift information from this another user terminal, this synchronization shift information be this another user terminal after receiving described P2P signal of communication, according to this P2P signal of communication, the synchronisation offset that obtains of estimation; With

The time adjusting device that transmits based on synchronization shift information is used for according to this synchronization shift information, adjusts this user terminal sends Timing Advance from signal to this another user terminal.

19, as claim 17 or 18 described user terminals, also comprise:

A feedback signal generating means, be used for process in described direct link foundation, when this user terminal is received described another user terminal to the detection signal of its transmission, poor from time that network system transmitted that this user terminal calculates that its time of receiving this detection signal receives with it, and the difference that calculates sent to this another user terminal as feedback signal.

20, user terminal as claimed in claim 19 also comprises:

A synchronization shift information generating apparatus, be used for when this user terminal is received the P2P signal of communication of this another user terminal emission, according to this P2P signal of communication, estimate the synchronization shift information of this another user terminal, and this synchronization shift information is sent to this another user terminal.

21, a kind ofly in TDD cdma communication system, can support two user terminals to carry out the network system of P2P communication, comprise:

A time slot allocation information dispensing device is used for via downlink control channel, to two user terminal sending time slots assignment information of carrying out P2P communication;

A spreading code distributes information generation device, is used for generating with the corresponding spreading code of each downlink time slots of this time slot allocation information distributing information; And

A spreading code distributes information transmitting apparatus, be used for via downlink control channel, send described spreading code respectively to these two user terminals and distribute information, so that the signal of the P2P that each user terminal in these two user terminals is received communication and signal Synchronization from this network system.

22, network system as claimed in claim 21, wherein said spreading code distribute information to comprise the spreading code information of being used by other user terminals in the described downlink time slots at least.

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