CN1582001A - Method for high-frequency amplifying station to gain switching point in TD-SCDMA system - Google Patents

Abstract

The invention discloses a method for a repeater to obtain a conversion point in a TD-SCDMA system, which is used for enhancing and forwarding the uplink signal between the first and second conversion points of the same subframe, and enhancing and forwarding the subframe The downlink signal between the second transition point and the first transition point in the next subframe. The method comprises the following steps: a. placing the position information of the second switching point in the broadcast channel for transmission; b. the repeater acquiring the time of the first switching point of the subframe; c. The first two code channels; d. Extract the information of the position of the second conversion point from the demodulated result in step c, and obtain the time of the second conversion point. Wherein, the information of the position of the second switching point transmitted by the broadcast channel is dynamically updated, and the repeater repeats steps c and d while enhancing and forwarding the uplink and downlink signals. The invention overcomes the shortcoming that the existing repeater cannot work under the condition that the uplink and downlink time slot allocation modes configured by the TD-SCDMA system are constantly changing.

Description

The Method of Repeater Obtaining Switching Point in TD-SCDMA System

technical field

The invention relates to a TD-SCDMA system, in particular to a method for a repeater in the TD-SCDMA system to obtain a conversion point.

Background technique

Time Division Synchronous Code Division Multiple Access (TD-SCDMA) is one of the three main standards of the third generation mobile communication (3G) approved by the International Telecommunication Union (ITU) and 3GPP. TD-SCDMA is called a low chip rate (1.28MCps, 1.28 megachip/second) time-division multiplexing technical solution in the ITU standard.

As shown in Figure 1, in time, TD-SCDMA signals are divided into periodic time units. A basic time unit is called "radio frame", and the length of each radio frame is 10ms. Each radio frame is divided into two "subframes" of equal length, and the length of each subframe is 5ms. Each subframe is divided into several different parts, among which there are 7 time slots (TS) with the same time length, each time slot is 0.675ms long, and the downlink position between time slot TS0 and time slot TS1 Pilot time slot (DwPTS), uplink pilot time slot (UpPTS) and a guard interval (GP), their time lengths are 75μs, 125μs and 75μs respectively.

According to different signal directions, each time slot is divided into two types: uplink direction and downlink direction. The uplink direction means that the wireless signal transmitted in the time slot is transmitted by the user terminal equipment (UE) and received by the base station (Node-B); the downlink direction means that the wireless signal transmitted in the time slot is transmitted by the Node-B , the UE receives.

In the TD-SCDMA standard, TS0 is always designated as the downlink direction, and TS1 is always designated as the uplink direction. TS2, TS3, ..., TS6 will be dynamically designated as the uplink direction or the downlink direction according to the needs of the business. In addition, DwPTS is the downlink direction, and UpPTS is the uplink direction. The time slots in the uplink direction and the time slots in the downlink direction are separated by a switching point. In each subframe, there are two transition points: the first transition point is from the downlink direction to the uplink direction, the GP located between DwPTS and UpPTS; the second transition point is from the uplink direction to the downlink direction, The position is between the last uplink time slot and the second downlink time slot (TS0 is the first downlink time slot) in each subframe. Among them, the first transition point is fixed relative to the start time of each subframe; the second transition point is designated as different numbers of uplink time slots and downlink time slots along with TS2, ..., TS6, which are relative to each subframe The start time of the frame, will vary.

Figure 2 lists several cases where the positions of the transition points are different. As shown in Figure 2, in a), the second conversion point is located between the time slot TS1 in the uplink direction and the time slot TS2 in the downlink direction; b) the second conversion point is located between the time slot TS2 in the uplink direction and the time slot TS3 in the downlink direction; c ) The second switching point is located between the time slot TS3 in the uplink direction and the time slot TS4 in the downlink direction.

In a TD-SCDMA network, a certain number of repeaters and base stations are required for combined use. The repeater enhances and forwards the signals sent by the base station and the mobile phone, thereby expanding or supplementing the coverage of the communication network. In the current application of repeaters, wireless repeaters have been widely used due to their cheap price, convenient site selection and simple transmission.

The working principle of the existing wireless repeater is that in the downlink direction, the donor antenna of the repeater receives the downlink signal from the base station, amplifies and processes it through its own radio frequency system, and then forwards it to the At the same time, in the uplink direction, the retransmission antenna of the repeater receives the uplink signal from the mobile phone, and after the same processing, it is forwarded to the base station through the donor antenna of the repeater. The existing repeater can run in GSM, IS95, CDMA2000, W-CDMA and other mobile communication systems. In these systems, uplink radio signals and downlink radio signals are at different frequencies. Therefore, the existing repeater generally includes two sets of processing systems, which respectively perform processing such as receiving, amplifying, and transmitting the uplink signal and the downlink signal. The two processing systems operate on different frequencies.

However, in the TD-SCDMA system, the uplink signal and the downlink signal are at the same frequency, and the uplink and downlink signals are distinguished by time multiplexing. If the existing repeater is used in the TD-SCDMA system, the uplink and downlink processing systems of the repeater will work on the same frequency, and the uplink and downlink signals will generate positive feedback, resulting in signal deterioration, and the repeater will not be able to use.

It can be known from the previous description that Node-B will constantly adjust the state of its transmitter and receiver between two switching points. In each subframe, before the first switching point, Node-B is in the transmitting state; between the first and second switching point, Node-B is in the receiving state; after the second switching point, Node-B is in the transmitting state.

Therefore, the idea to solve this problem is that, in each subframe, the repeater only enhances and forwards the uplink signal between the first and second switching points, and between the second switching point and the first switching point of the next subframe Only the downlink signal is enhanced and forwarded between one switching point, so as to avoid the simultaneous work of the uplink and downlink processing systems.

The existing technology is implemented in this way: the repeater matches the signal in the received DwPTS through one or more matched filters, and knows the time when the DwPTS arrives at the repeater. Since the first switching point of each subframe It is in the GP time period between DwPTS and UpPTS, so that the repeater can calculate the time of the first switching point. However, the time of the second transition point cannot be obtained by a similar method. The repeater can simply default that the second conversion point is between TS3 and TS4 (or other time slots). If the allocation of uplink and downlink time slots configured by the mobile network system is fixed as TS1~TS3 for uplink, TS4~TS6 for uplink Downlink, you can use such a repeater.

If the uplink and downlink time slot allocation configured by the mobile network system is in other ways, or the uplink and downlink time slot allocation mode configured by the mobile network system is constantly changing, the repeater will not be able to use because it cannot obtain the position of the second switching point .

Contents of the invention

The purpose of the present invention is to provide a method for the repeater to obtain the second conversion point in the TD-SCDMA system.

The broadcast channel (BCH) is a downlink transmission channel for broadcasting system and cell-specific information. The BCH is mapped to two basic common control physical channels (P-CCPCH1 and P-CCPCH2) at the physical layer. In the TD-SCDMA system, the time slots of P-CCPCH1 and P-CCPCH2 are fixed TS0, which are mapped to the first two code channels (0 code channel and 1 code channel) whose spreading factor of TS0 is 16.

The method proposed by the present invention is to use at least 3 bits in the BCH channel to represent the information of the second switching point of the local cell. For example, the number n is used to indicate that the second switching point is between the nth time slot and the n+1th time slot of each subframe. The value range of n is 1, 2, ..., 5, and the value n is added to the information carried by the BCH channel.

Since the first switching point of each subframe is in the GP time period between DwPTS and UpPTS, the repeater can calculate the time of the first switching point. Thus, the repeater can know the positions of the two switching points in each subframe.

Therefore, the present invention provides a method for a repeater to obtain a conversion point in a TD-SCDMA system, which is used to enhance and forward the uplink signal between the first and second conversion points of each subframe, and to enhance and forward For the downlink signal between the second conversion point of the subframe and the first conversion point in the next subframe, the method includes the following steps:

a. Place the position information of the second conversion point in the broadcast channel for transmission;

b. The repeater obtains the time of the first conversion point of the subframe;

c. Demodulate the first two code channels of time slot 0 in the subframe;

d. Extracting information on the position of the second switching point from the demodulated result in step c to obtain the time of the second switching point.

Wherein, using the idle part of the broadcast channel to indicate the information of the position of the second switching point is completed by Node-B or RNC.

Wherein, the information indicating the position of the second switching point by using the broadcast channel is dynamically updated; while the repeater is continuously enhancing and forwarding the uplink or downlink signal, the second switching point is obtained by repeatedly executing steps c and d Changes in location.

The invention overcomes the shortcoming that the existing repeater cannot work under the condition that the allocation mode of uplink and downlink time slots configured in the TD-SCDMA system is constantly changing.

Description of drawings

Fig. 1 is TD-SCDMA frame structure;

Fig. 2 is the schematic diagram of conversion point position;

Fig. 3 is the burst format of DwPTS time slot;

Fig. 4 is P-CCPCH physical channel wireless burst format;

Fig. 5 is a flow chart of the present invention for the repeater to obtain the conversion point information.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

Figure 3 is the burst format of the DwPTS time slot, which includes 32 chips (chips) of GP and 64 chips of SYNC_DL, and the total time length is 75 μs. Among them, SYNC_DL is a 64-bit PN sequence predetermined by the system, and SYNC_DL has a maximum of 32 possible choices.

Figure 4 is the wireless burst format of the P-CCPCH physical channel, which includes two pieces of 352chips data (Data symbols), 144chips user training sequence (Midamble) and 16chips GP. Among them, the midamble code is the result of different cyclic displacements of a basic midamble code, and the displacement interval can be an integer multiple of 8. Only one fixed displacement method is used in the same cell. There are 128 basic midamble codes in the system.

In the TD-SCDMA system, from starting up to sending out the first random access request, the mobile station is divided into four processes: downlink synchronization capture, system information reading, uplink synchronization establishment, and random access. The repeater in the present invention Using the first two steps of the process, that is, downlink synchronous acquisition and system information reading, the position information of the second switching point of the subframe is obtained.

Fig. 5 is a flow chart of the present invention for the repeater to obtain the conversion point information. As shown in Figure 5, the process for the repeater to obtain the conversion point information is as follows:

In step 01, the repeater receives subframe information. Since the repeater is only responsible for enhancing and forwarding the signal sent by Node-B, the repeater itself cannot use at least 3 bits in the idle part of the BCH to represent the position information of the second conversion point. This function can only be performed by Node-B completed, or completed by the RNC controlling Node-B.

Step 02, calculate the time when the DwPTS arrives at the repeater. The repeater matches the received signal in the DwPTS through one or more matched filters to obtain the time.

The burst format of the DwPTS time slot is shown in Figure 3. The SYNC_DLs of adjacent cells in the system are different from each other. SYNC_DL is included in the DwPTS time slot in the TD_SCDMA wireless burst. According to the wireless frame structure of TD-SCDMA, SYNC_DL is sent once every subframe time (5ms) in the system, and the information is sent at a constant full power value each time. When the UE accesses the system, the 32 SYNC_DL codewords are searched one by one (that is, the received signal is cross-correlated with the 32 possible SYNC_DL codewords one by one). Since the codewords have good orthogonality with each other, the correlation peak value can be obtained The largest codeword is considered to be the SYNC DL used by the currently accessed cell. At the same time, the downlink timing of the system can also be preliminarily determined according to the time position of the correlation peak. The repeater uses the UE access system method to determine the arrival time of the DwPTS in each subframe to the repeater.

Step 03, get the time of the first conversion point. As shown in Figure 1, DwPTS has a fixed time relationship with the first transfer point (GP), so the time of the first transfer point can be directly obtained according to the result of step 02.

Step 04, demodulate code channel 0 and code channel 1 of the TS0 time slot. The BCH carrying the position information of the second conversion point is mapped to two basic common control physical channels (P-CCPCH1 and P-CCPCH2) at the physical layer. In the TD-SCDMA system, the time slots of P-CCPCH1 and P-CCPCH2 It is a fixed TS0, and mapped to the first two code channels with a spreading factor of 16 in TS0, that is, code channel 0 and code channel 1.

To extract the system broadcast message from the Data symbols field, four pieces of information need to be obtained: a) the parameter model of the wireless channel; b) the scrambling code (Scrambling code) used by the current cell; c) the system frame number; d) the use of BCH information The spreading factor and spreading code.

a). The wireless channel parameters are obtained by decoding the training sequence (midamble code) in the wireless burst structure. Each SYNC_DL sequence corresponds to 4 basic midamble codes. Since the SYNC_DL has been obtained in step 01, the repeater only needs to test the different phases of these 4 basic codes one by one with relevant methods, and can find the midamble code used by the current system and at the same time Estimate the parameters of the current wireless channel.

b). There is a one-to-one correspondence between the scrambling codes used by the cell and the midamble codes, which are used to distinguish users in different cells. In the same cell, the scrambling codes and midamble codes used by all users are the same.

c). In order to correctly decode the information in the BCH, the repeater must know the system frame number of each frame. The system frame number is reflected in the arrangement pattern of the phase change during the 4-phase phase-shift keying (QPSK) modulation of the physical channel. By performing phase detection on n consecutive DwPTS time slots, the system frame number can be found, that is, multi-frame synchronization can be obtained. In this way, the position of the BCH information in the P-CCPCH channel frame structure can be determined.

d). According to the system requirements, the spreading factor of the BCH message is 16, and the code channel uses 0 code channel and 1 code channel.

According to the above information, the repeater completes the demodulation of P-CCPCH and the decoding of BCH, and interprets the system information.

Step 05, get the time of the second conversion point. Extract the position information of the second transition point from all the information carried by the BCH demodulated in step 04, because the length of each time slot is 0.675ms, so according to the position of the second transition point, the second transition point can be directly obtained time. Since the allocation of uplink and downlink time slots is constantly changing, the repeater needs to repeat steps 04 and 05 while boosting and forwarding the uplink or downlink signals, so as to continuously obtain the updated time information of the second conversion point.

After the repeater obtains the conversion point information of each subframe, it only enhances and forwards the uplink signal between the first and second conversion points of the subframe, and between the second and the first conversion point of the next subframe It only enhances and forwards the downlink signal, thus avoiding the simultaneous work of the uplink and downlink processing systems.

Claims (7)

1. A method for a repeater to obtain a conversion point in a TD-SCDMA system, which is used to enhance and forward the uplink signal between the first and second conversion points of the same subframe, and to enhance and forward the second subframe of the subframe A downlink signal between a transition point and the first transition point in the next subframe, characterized in that the method comprises the following steps: a. Place the position information of the second conversion point in the broadcast channel for transmission; b. The repeater obtains the time of the first conversion point of the subframe; c. Demodulate the first two code channels of time slot 0 in the subframe; d. Extracting information on the position of the second switching point from the demodulated result in step c to obtain the time of the second switching point. 2. The method for the repeater to obtain the switching point in the TD-SCDMA system according to claim 1, is characterized in that: the information of utilizing the broadcast channel to transmit the second switching point position described in step a is completed by the base station. 3. the method that repeater obtains switching point in the TD-SCDMA system according to claim 1 is characterized in that: the information that utilizes broadcast channel to transmit the second switching point position described in step a is by wireless network controller Completed. 4. the method that repeater obtains conversion point in the TD-SCDMA system according to claim 1 is characterized in that: the information of the second conversion point position described in step a is to be recorded in at least 3 of the idle part of the broadcast channel in bits. 5. the method that repeater obtains conversion point in the TD-SCDMA system according to claim 1 is characterized in that: step b is to obtain subframe by the time that downlink pilot time slot arrives at repeater in calculating subframe The first conversion point time. 6. The method for the repeater to obtain the switching point in the TD-SCDMA system according to claim 1, characterized in that: the information of utilizing the broadcast channel to transmit the second switching point position described in step a is dynamically updated. 7. The method for the repeater to obtain the conversion point in the TD-SCDMA system according to claim 1, characterized in that: the steps c and d are repeatedly executed to obtain the change of the second conversion point position.

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