WO2004066532A1

WO2004066532A1 - Implement method and apparatus for downlink synchronization subsystem

Info

Publication number: WO2004066532A1
Application number: PCT/CN2003/000061
Authority: WO
Inventors: Li Fang; Chen Ji; Jingbo Liu; Yongsheng Zhang
Original assignee: Linkair Communications,Inc.
Priority date: 2003-01-23
Filing date: 2003-01-23
Publication date: 2004-08-05
Also published as: AU2003211659A1; CN1640041A; WO2004066532A8

Abstract

The present invention relates to an implement method and apparatus for downlink synchronization subsystem, which can detect the boundary of initial frame, and the initial frequency can be catched by using the result of initial frame boundary detection, Then, it can carry the cell search and selection, the multipath signal searching and tracing, the carrier frequency tracking, and timing frequency tracking, In CDMA system, by implementing the frequency catching, downlink synchronization acquisition and cell identification, providing multipath information of traffic channel, and running the carrier frequency tracking, the present invention can ensure the accuracy of timing frequency, and have the characteristic of simplicity and utility.

Description

TECHNICAL FIELD The present invention relates to the field of wireless communication technologies, and in particular, to a CDMA system, and in particular, to a method and an apparatus for implementing a downlink synchronization subsystem. Background technique

At present, the technology of C picture A is developing rapidly. During the research on the TDD mode of CDMA systems using LAS codes (such as in the LinkAirll l TD-LAS experimental system of Lianyu Communication Co., Ltd.), we can draw: System design and achieved initial carrier frequency offset value is smaller than the specification ^{5 00Hz,} LA at this time sequences of different polarity can be accurately identified cells, the downlink synchronization and physical channels may despread across the 874Tc, and therefore adapted to the respective cells using the downlink physical synchronization channel Filter, it can realize downlink synchronization acquisition and cell identification at the same time, without the need to adjust the carrier frequency. In a commercial LAS-CDMA TDD system, the frequency accuracy of a mobile station crystal oscillator is generally around a few ppm, and it operates in the 2GHz frequency band, and the carrier frequency deviation is generally between 1KΗζ to 10KΗζ. Under this condition, LA polar sequences of different cells cannot be accurately identified, and despreading up to 874Tc cannot be used. Therefore, it is necessary to find an implementation method and device for implementing downlink synchronization acquisition and cell identification in the TD-LAS system. Furthermore, a method and device for implementing downlink synchronization acquisition and cell identification that are generally effective for a general CDMA system are obtained. Summary of the invention

An object of the present invention is to provide a method and a device for implementing a downlink synchronization subsystem, which are used to implement frequency acquisition in a CDMA system, and simultaneously realize downlink synchronization acquisition and cell identification, and provide multipath information for receiving a service channel, and Carrier frequency tracking is performed to ensure the accuracy of the timing frequency and has the characteristics of simplicity and practicality.

The technical solution of the present invention is: A method for implementing a downlink synchronization subsystem includes the following steps: detecting an initial frame boundary;

Use the result of initial frame boundary detection to perform initial frequency capture;

Perform cell search and selection;

Search and track multipath signals;

Carrier frequency tracking;

Perform timing frequency tracking.

The detection of the initial frame boundary refers to: In the initial frame boundary detection, the relevant peaks are extracted through a filter that matches the physical channel downlink synchronization of all cells to implement frame boundary detection; because all cells use different bipolar LAs Polarity sequence, so the downlink synchronization matching filter can only perform matching filtering on time slots, and perform LA non-coherent combining on the entire downlink synchronization physical channel.

The initial frequency acquisition refers to: After the initial frame boundary detection is completed, the mobile station can obtain the starting timing positions of one or more downlink synchronization physical channels from different cells that may exist; The frame boundary information of a cell is strong, the carrier frequency deviation is obtained by using the downlink synchronization physical channel, and the VC0 of the radio frequency needs to be adjusted to complete the initial carrier frequency acquisition

The performing cell search and selection refers to: searching all cells / sectors with sufficient signal strength, and establishing downlink synchronization with the selected cell.

The searching and tracking of multi-path signals refers to: Multi-path searching and tracking refers to receiving signals received by a mobile station through multiple paths after receiving frame synchronization, code synchronization, and carrier synchronization and determining a target cell. Select the appropriate path and provide it to the RAKE receiver.

The carrier frequency tracking means that: the initial carrier frequency acquisition unit reduces the initial frequency difference to less than 500 Hz, and the cell identification unit obtains the LA + LS combination used by the cell; the mobile station uses the downlink continuous pilot channel for frequency tracking , Reduce the remaining frequency difference to less than 100Hz, to meet the needs of demodulation.

The described timing frequency tracking refers to: The timing frequency tracking is detected by using a mobile station The frame period is compared with the exact period to extract the clock error.

The method according to the present invention is characterized in that its steps further include:

After the mobile station is powered on, it first performs initial frame boundary detection. If no downlink synchronization physical channel can be detected, it will always perform frame boundary detection;

After the frame boundary detection is completed, initial carrier frequency acquisition and cell search and selection are performed until the cell search and selection is successful. If the time for cell search and selection is greater than a certain parameter M, the initial frame boundary detection is performed again;

After the initial carrier frequency acquisition and cell search and selection are successful, the polar sequence of the serving cell, the Cel ID, is obtained, and the LS + LA code group of the cell / sector is obtained;

The multipath search and tracking loop starts to work, and transmits the multipath information of the received signal to the upper layer. The timing tracking loop, carrier tracking loop, and BCH channel reception can run and perform CRC check.

The invention also provides a device for implementing a downlink synchronization subsystem, which is characterized by comprising: an initial frame boundary detection device, an initial carrier frequency acquisition device, a cell search and selection device, a multipath search and tracking device, and a carrier frequency tracking device , Timing frequency tracking device;

An input signal enters the initial frame boundary detection device, and after detecting a downlink synchronization physical channel, the information of the initial frame boundary is sent to the initial carrier frequency acquisition device and the cell search and selection device;

The initial carrier frequency acquisition device and the cell search and selection device perform initial carrier acquisition and cell search selection by using information of an initial frame boundary and a received signal of a downlink synchronization channel, until the cell search and selection succeeds, the initial carrier frequency The output signal of the capture device is the initial carrier frequency difference; the output signal of the cell search and selection device is the energy and arrival delay of each cell searched, and this information is reported to the upper layer;

The multipath search device and tracking device use the time of arrival of the frame and the received signal of the downlink synchronization channel to find multipath information for the timing frequency tracking device and the carrier frequency tracking device.

The initial frame boundary detection device includes: Input: the received signal (4 / c) after passing through the baseband filter;

Output: The position of the initial frame boundary of the searched cell with the strongest energy, range: (0, 30720 * 4 The initial frequency acquisition device includes:

Input: the downlink synchronization channel received signal (4 / c) passing the baseband filter, the position of the frame boundary;

Output: carrier frequency deviation, range: (-5 z, 5KHz).

The cell search and selection device includes:

Input: the downlink synchronization channel received signal (4c) after passing through the baseband filter, the position of the frame boundary;

Output: Frame boundary position and energy of each cell.

• The multi-path signal searching and tracking device includes:

Input: receive the signal (4) through the downlink synchronization channel of the baseband filter, the frame boundary position of the selected cell;

Output: position of two paths;

Multi-path search and tracking is performed after the mobile station obtains frame synchronization, code synchronization, and carrier synchronization, and determines the target cell, then selects an appropriate path among the received signals that reach the mobile station through multiple paths, and provides it to the RAKE receiver.

The carrier frequency tracking device includes:

Input: The received signal (4 / c) of the downlink traffic channel through the baseband filter, the position of the two paths; Output: the carrier frequency deviation (-500Hz, 500Hz);

The initial carrier frequency acquisition unit reduces the initial frequency difference to less than 500Hz, and the cell identification unit obtains the LA + LS combination used by the cell; the mobile station uses the downlink continuous pilot channel for frequency tracking, and reduces the remaining frequency difference to less than 100Hz To meet the needs of demodulation.

The timing frequency tracking device includes:

Enter: the position of the first path;

Output: Timing frequency deviation (-200Hz, 200Hz); Timing frequency tracking uses the frame period detected by the mobile station to compare with the accurate period to extract the clock error. .

The device according to the present invention further comprises: a baseband filter, a splitter, an RF VC0, a BB VCO, and a CRC check device;

After the mobile station is powered on, the baseband received signal passes through the 4fc baseband filter and enters the initial frame boundary detection device. After detecting the downlink synchronization physical channel, the information of the initial frame boundary is sent to the initial carrier frequency acquisition device and A cell search and selection device, the initial carrier frequency acquisition device and the cell search and selection device use initial frame boundary information and a received signal of a downlink synchronization channel to perform initial carrier acquisition and cell search selection until the cell search and selection is successful, The output signal of the initial carrier frequency acquisition device is an initial carrier frequency difference, which is used to adjust the VC0 of the radio frequency. The output signal of the cell search and selection device is the energy and arrival delay of each cell that is searched. To the upper layer, the downlink multipath search and tracking device uses the frame arrival time and the received signal of the downlink synchronization channel to find multipath information for the timing frequency tracking device, the carrier frequency tracking device, and the reception and detection of the BCH channel. Said CRC checking device, said An output signal of the frequency tracking means for adjusting the timing of the baseband VC0; of the carrier frequency tracking apparatus using multi-path information and the downlink pilot signals received continuous pilot channel, to calculate the carrier frequency difference, for adjusting the radio frequency VC0.

A beneficial effect of the present invention is that, by providing a method and device for implementing a downlink synchronization subsystem, the method is used for frequency acquisition in a CDMA system, and simultaneously realizes downlink synchronization acquisition and cell identification, and provides multipath information for receiving a service channel. The carrier frequency is tracked to ensure the accuracy of the timing frequency, and has the characteristics of simple and practical. among them:

Initial frame boundary detection: A frame boundary of a cell may be detected;

Initial frequency acquisition: Use the result of the initial frame boundary detection to obtain the frame start position of the downlink synchronization physical channel, perform partial despreading of the LS code, use the FFT algorithm to implement frequency acquisition, and reduce the carrier frequency deviation from the KHz range to less than 500Hz;

Cell search and selection: When the carrier frequency deviation drops below 500Hz, use the LS + LA Matching filtering, the downlink synchronization physical channel is despread over the entire 874Tc, which can simultaneously achieve downlink synchronization acquisition and cell identification;

Multi-path signal search and tracking: After cell search and selection, the mobile station uses the downlink synchronization channel to search and track multi-path signals to provide multi-path information for the reception of traffic channels;

Carrier frequency tracking: Since the reception of the service channel requires the deviation of the carrier frequency to be less than 100Hz, it is necessary to continuously track the carrier frequency. Using continuous pilot channels and using differential detection to track the carrier frequency is simple and practical;

Timing frequency trace: VC0 used by the mobile station for baseband timing and sampling has an initial deviation from the VC0 of the base station. Large deviations are likely to cause slip codes and affect the reception quality of the service channel. Therefore, the frequency of VC0 needs to be constantly adjusted to ensure the timing frequency. Accurate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a subframe structure diagram of a downlink synchronization channel;

Figure 2 is a control flowchart of the downlink synchronization subsystem;

Figure 3 is a structural block diagram of the downlink synchronization subsystem. DETAILED DESCRIPTION The present invention provides a method and device for implementing a downlink synchronization subsystem, including algorithms such as initial frame boundary detection, initial carrier acquisition, cell search and selection, multipath signal search and tracking, carrier tracking, and timing tracking. Through simulation, the feasibility is verified, which provides a reference and basis for the synchronization implementation of the CDMA system. The following uses the TD-LAS system as an example and in conjunction with the drawings to explain the specific implementation of the present invention in detail.

The downlink synchronization subsystem of the TD-LAS system needs to complete the following tasks:

1) Initial frame boundary detection;

2) initial carrier acquisition;

3) cell search and selection;

4) search and tracking of multipath signals; 5) Carrier frequency tracking;

6) Timing frequency tracking.

The specific implementation of the present invention is mainly a set of solutions for the downlink synchronization subsystem designed for the physical layer specification of the TD-LAS system, including initial frame boundary detection, initial carrier acquisition, cell search and selection, multipath signal search and tracking. , Carrier tracking, timing frequency tracking, etc.

In the TD-US system, the structure of the downlink synchronization channel is shown in Figure 1. The algorithms of all cells use the same LS spreading code (see Table 1) and different modulation symbol code groups to distinguish the cells. The downlink synchronization sub-frame has a total of 8 time slots, and the length of each time slot refers to Table ^2. Each time slot transmits a downlink synchronization pulse of 72 Chips in length, which includes the C code of 24 chips and the S code of 24 chips. A guard band of 24 chips is reserved in the middle. The downlink synchronization pulse is transmitted at the beginning of each time slot. The LS code used for the downlink synchronization channel is complex digital, and the corresponding spreading and despreading is similar to QPSK, as shown in Table 4. The 8 slots of the downlink synchronization subframe can transmit 8 modulation symbols. A total of 8 bipolar mutually orthogonal code sequences can be obtained, such as each row or column of the 8 x 8 Wal sh matrix. In the TD-LAS system These code sequences are called LA polar sequences (see Table 3). 8 orthogonal LA polar sequences can support 8-cell / sector networking; to support a larger network size, consider combining with other cell identification methods such as continuous pilot cell identification, or you can Make different cell / sector clusters use different LA guard intervals to expand the signal set of D-SYNPCH. Table 1. Spreading code (LS code) of the downlink synchronization channel ( _{j =} ^ I)

Where: A = (+ j + + +-), = (-j-+ +-), C = (-j—— +), D = (· _ + +-) Table 2. Frame slot length

LA slot (TS,) 0 1 2 3 4 5 6 7

Length (Tc) 96 98 100 102 104 106 108 80 Table 3. LA Polarity Codes for Downlink Synchronization Channels

Table 4. LA Polarity Codes for Downlink Synchronization Channels

In the system, the initial carrier frequency offset is less than 500Hz. At this time, the LA polarity sequence of different cells can be accurately identified, and the downlink synchronization physical channel can be despread over the entire 874Tc. Therefore, the downlink synchronization physical channel matching each cell is used. The filter can implement downlink synchronization acquisition and cell identification at the same time, and does not need to adjust the carrier frequency. However, in commercial CDMA systems, the frequency accuracy of a mobile station crystal oscillator is generally around a few ppm, working in the 2GHz band, and the carrier frequency deviation is generally between ΙΚΗζ to ΙΟΚΗζ. Under this condition, the LA polar sequences of different cells cannot be accurately identified, and despreading up to 874Tc cannot be used. Therefore, the initial carrier must be performed before the algorithm for downlink synchronization acquisition and cell identification is implemented in the TD-LAS system. Capture so that the frequency deviation is less than 500Hz. The process of the downlink synchronization subsystem is as follows:

1) Initial frame boundary detection: detecting a possible cell boundary;

2) Initial frequency acquisition: Use the result of the initial frame boundary detection to obtain the frame start position of the downlink synchronization physical channel, perform partial despreading of the LS code, use the FFT algorithm to implement frequency acquisition, and reduce the carrier frequency deviation from the KHz range to 500Hz the following;

3) Cell search and selection: When the carrier frequency deviation drops below 500 Hz, use LS + LA Matching filtering, and the downlink synchronization physical channel is despread over the entire 874Tc, which can simultaneously achieve downlink synchronization acquisition and cell identification;

4) Multi-path signal search and tracking: After the cell is searched and selected, the mobile station uses the downlink synchronization channel to search and track the multi-path signal to provide multi-path information for the reception of the service channel;

5) Carrier frequency tracking: Because the reception of the service channel requires the deviation of the carrier frequency to be less than 100Hz, it is necessary to continuously track the carrier frequency. The continuous pilot channel is used to track the carrier frequency by differential detection. It is simple and practical ;

6) Timing frequency tracking: The VC0 used by the mobile station for baseband timing and sampling has an initial deviation from the VC0 of the base station. The large deviation easily generates slip codes and affects the reception quality of the service channel. Therefore, the frequency of VC0 needs to be constantly adjusted to ensure the timing. Accurate frequency.

The control of the downlink synchronization subsystem process is shown in Figure 2. The mobile station first performs initial frame boundary detection after power-on. If no downlink synchronization physical channel can be detected, frame boundary detection will always be performed. After the frame boundary detection is completed, initial carrier frequency acquisition and cell search and selection are performed until the cell search and selection is successful. If the time for cell search and selection is greater than a certain parameter M, the initial frame boundary detection is performed again. After the initial carrier frequency acquisition and cell search and selection are successful, the LA polar sequence of the serving cell, the Cel ID, and the LS + LA code group of the cell / sector are obtained. After that, the multipath search and tracking loop began to work, and the multipath information of the received signal was transmitted to the upper layer. The timing tracking loop, the carrier tracking loop, and the BCH channel reception could be run, and a CRC check was performed.

The structure of the receiver of the downlink synchronization subsystem is shown in Figure 3. After the mobile station is powered on, the baseband received signal passes through the 4 / c baseband filter and enters the IFBD (Initial Frame Boundary Detection) unit. After detecting the downlink synchronization physical channel, the information of the initial frame boundary is sent to the initial carrier frequency acquisition unit and cell. Search and selection unit, initial carrier frequency acquisition unit and cell search and selection unit use initial frame boundary information and received signals of the downlink synchronization channel to perform initial carrier acquisition and minimization. Zone search and selection, until the zone search and selection is successful, the output signal of the initial carrier frequency capture unit is the initial carrier frequency difference, which is used to adjust the vco of the radio frequency, and the output signal of the zone search and selection unit is the energy and arrival of each cell searched The delay is reported to the upper house. The downlink multipath search and tracking unit uses the frame arrival time and the received signal of the downlink synchronization channel to find multipath information for the timing frequency tracking unit, the carrier frequency tracking unit, and the reception and CRC of the BCH channel. The output signal of the checking unit and the timing frequency tracking unit is used to adjust the baseband timing VC0; the carrier frequency tracking unit uses the multipath information and the received signal of the downlink continuous pilot channel to calculate the carrier frequency difference and is used to adjust the VC0 of the radio frequency; downlink The description of each point in the receiver structure of the synchronization subsystem is shown in Table 5, and the input and output description of each module is shown in Table 6. Table 5. Explanation of points in the receiver structure of the downlink synchronization subsystem

Table 6. Description of the outputs and inputs of each module in the receiver structure of the downlink synchronization subsystem Module Input Output

Received signal (4 / _C ) of the initial frame edge passing through the baseband filter The position detected by the initial frame boundary of the cell with the strongest energy searched, Range: (0,30720 * 4) The initial carrier is received through the downlink synchronization channel of the baseband filter Signal carrier frequency deviation (_5KHz, 5KHz) capture (4c), position of frame boundary

Cell search Received signals on the downlink synchronization channel after passing through the baseband filter Frame position and energy of each cell and selection (4 / c), the position of the frame boundary

Multipath search Position of the two paths received by the downlink synchronization channel through the baseband filter

And tracking (4 / c), frame boundary position of selected cell

Carrier frequency Received signal through downlink traffic channel of baseband filter Carrier frequency deviation (_500Hz, 500Hz) Tracking (4 / c), position of two paths

Position of the first path of timing frequency Deviation of timing frequency (-200Hz, 200Hz) Tracking In the initial frame boundary detection algorithm, the relevant peaks are extracted through a filter that matches the physical channel downlink synchronization of all cells to implement frame boundary detection. Because all cells use different LA polar sequences, the downlink synchronization matching filter can only perform matching filtering on time slots and perform LA non-coherent combining on the entire downlink synchronization physical channel.

As shown in Figure 1, the despreading length of the downlink synchronization physical channel on the time slot is 72Tc, and the corresponding 3dB performance loss point is 8KHz. Therefore, the maximum frequency deviation tolerated by this algorithm is [-8KHz, 8KHz].

After the initial frame boundary detection is completed in the first step, the mobile station can obtain the starting timing positions of one or more downlink synchronization physical channels from different cells that may exist. The mobile station selects the frame boundary information of a cell with the strongest energy, uses the FFT algorithm to calculate the carrier frequency deviation, and constantly adjusts the VC0 of the radio frequency to complete the initial carrier frequency acquisition. After this step is completed, the carrier frequency deviation will drop below 500Hz.

The signal despreading length used in the algorithm is 48Tc, and the multiplied signal is estimated, so the frequency deviation range that the algorithm can estimate is [-5KHz, 5KHz].

The purpose of cell search is to find all cells / sectors with sufficient signal strength and establish downlink synchronization with the selected cell. In the TD-LAS system, the service channels of different cells use different LS spreading code groups and different LA intervals. In order for a mobile station to correctly demodulate the signal of a certain cell / sector and establish communication, it must obtain the information of the LS code group and LA interval arrangement of the traffic channel of this cell / sector. Therefore, in the cell search, the mobile station must search all possible cell ID sequences in the downlink synchronization physical channel, detect all cells / sectors with sufficient signal strength, and further obtain the destination cell / sector use. To improve reliability, the algorithm uses matched filtering on the entire downlink synchronization channel 874chip. Therefore, the frequency deviation range required by the algorithm is [-500Hz, 500Hz].

The prerequisite for carrier frequency tracking is that timing synchronization has been established between the mobile station and the base station, and the initial downlink carrier acquisition has reduced the carrier frequency deviation from a maximum of 6KHz to less than 500Hz. There are already some carrier frequency tracking algorithms, including FFT, DMP-FED, DD (differential frequency Rate detection). Because downlink continuous pilot channels are used in the TD-LAS system, frequency tracking can be achieved by using downlink continuous pilot channels.

LA initial carrier frequency capturing unit by the initial frequency difference is reduced to less than ^{5 00Hz,} cell-cell recognition unit used to obtain the present composition + LS. In this way, the mobile station can use the downlink continuous pilot channel for frequency tracking, reduce the remaining frequency difference to less than 100Hz, and meet the demodulation requirements.

In a mobile communication environment, a transmitter sends signals to a receiver via different paths. The signal of each path undergoes different random amplitude attenuation and phase rotation, and different time delays. After these signals reach the receiver, the complex signals cause fading due to the addition of the complex numbers. The existence of signals on these paths is also random. It exists at some moments, disappears at some moments, some moments are stronger than other path signals, and some moments may have stronger path signals. In a CDMA communication system, a RAKE receiver including multiple branches can be used to combat multipath fading.

The RAKE receiver uses a search unit to detect multiple paths with strong signals and assigns them to each branch. Each branch is responsible for synchronizing with a path signal and demodulating the signal in it, and then combining the path information according to certain rules.

Timing frequency tracking uses the frame period detected by the mobile station to compare with the accurate period to extract the clock error.

Let the frame period of the downlink signal be T. In the TD-LAS system, T = 30720T _C. When the clock frequency of the mobile station and the base station is the same, the frame period measured by the mobile station is also T. When the clock frequency difference between the mobile station and the base station is 4, the sampling rate will change and the measured frame period will also change. Let the periodic change be l, then ί, where f is the exact clock frequency. Therefore, through detection, l can be used to modify the sampling clock.

In the TD-LAS system, the multipath search unit uses a code matching filter to detect the position of the D-SYNCH channel corresponding to each path in the received signal sampling sequence. Since D-SYNCH is in every downstream The signal frame position is fixed. When there is no clock error, the detected position is also unchanged. Therefore, using the position change given by the multipath search unit, the clock change can be detected, and the clock frequency difference can be calculated.

Due to the random variation of the multipath channel, the multipath search unit should always give the information of the path that arrives first, and assume that the corresponding ^ is the same path, otherwise errors will be introduced. The clock frequency tracking unit must also perform multi-frame accumulation and smoothing on the calculated frequency difference to reduce the influence of the multipath position error.

A beneficial effect of the present invention is that, by providing a method and device for implementing a downlink synchronization subsystem, the method is used to implement frequency acquisition, and simultaneously realize downlink synchronization acquisition and cell identification, provide multipath information for receiving a service channel, and perform carrier The frequency tracking ensures the accuracy of the timing frequency and has the characteristics of simple and practical.

The above specific embodiments use the TD-LAS system as an example to describe the present invention, but this specific embodiment is not intended to limit the present invention, because the present invention is not limited to the TD-LAS system, its general principles and technologies, and corresponding implementations The method and device are effective for general CDMA systems.

Claims

Rights request

1. A method for implementing a downlink synchronization subsystem, comprising the following steps: detecting an initial frame boundary;

Perform cell search and selection;

Search and track multipath signals;

Carrier frequency tracking;

Perform timing frequency tracking.

2. The method according to claim 1, wherein the detecting the initial frame boundary refers to: in the initial frame boundary detection, extracting correlation peaks by using a filter that matches physical downlink synchronization channels of all cells, Realize frame boundary detection; Since all cells use different bipolar LA polarity sequences, the downlink synchronization matching filter can only perform matching filtering on time slots and perform LA non-coherent combining on the entire downlink synchronization physical channel.

3. The method according to claim 1, wherein the initial frequency acquisition refers to: after the initial frame boundary detection is completed, the mobile station can obtain one or more downlinks from different cells that may exist. The starting timing position of the synchronization physical channel; the mobile station selects the frame boundary information of a cell with the strongest energy, uses the downlink synchronization physical channel to obtain the carrier frequency deviation, and needs to adjust the VC0 of the radio frequency to complete the initial carrier frequency acquisition.

4. The method according to claim 1, wherein the performing cell search and selection refers to: searching all cells / sectors with sufficient signal strength, and establishing downlink synchronization with the selected cell.

5. The method according to claim 1, wherein the performing search and tracking of multipath signals refers to: multipath search and tracking is to obtain frame synchronization, code synchronization, and carrier synchronization at a mobile station, and determine After the target cell, a suitable path is selected from the received signals that reach the mobile station through multiple paths and provided to the RAKE receiver.

6. The method according to claim 1, wherein the performing carrier frequency tracking refers to: reducing an initial frequency difference to less than 500 Hz by an initial carrier frequency acquisition unit, and the cell identification unit obtains the information used by the cell. LA + LS combination; The mobile station uses the downlink continuous pilot channel for frequency tracking, and reduces the remaining frequency difference to less than 100Hz to meet the demodulation requirements.

7. The method according to claim 1, wherein the performing timing frequency tracking refers to: timing frequency tracking uses a frame period detected by the mobile station to compare with an accurate period to extract a clock error.

8. The method according to claim 1, further comprising: first performing an initial frame boundary detection after the mobile station is powered on, and if no downlink synchronization physical channel can be detected, the frame boundary detection will always be performed;

After the initial carrier frequency acquisition and cell search and selection are successful, the LA polar sequence of the serving cell, the Cel ID, and the LS + LA code group of the cell / sector are obtained;

The multipath search and tracking loop starts to work, and transmits the multipath information of the received signal to the upper layer. The timing tracking loop, the carrier tracking loop, and the BCH channel reception can run and perform a CRC check.

9. A device for implementing a downlink synchronization subsystem, comprising: an initial frame boundary detection device, an initial carrier frequency acquisition device, a cell search and selection device, a multipath search and tracking device, a carrier frequency tracking device, and a timing frequency Tracking device

The initial carrier frequency acquisition device and the cell search and selection device perform initial carrier acquisition and cell search selection by using information of an initial frame boundary and a received signal of a downlink synchronization channel, until the cell search and selection succeeds, the initial carrier frequency The output signal of the capture device is the initial The initial carrier frequency difference; the output signal of the cell search and selection device is the energy and arrival delay of each cell searched, and this information is reported to the upper layer;

The multi-path search device and tracking device use the time of arrival of the frame and the received signal of the downlink synchronization channel to find multi-path information for the timing frequency tracking device and the carrier frequency tracking device.

10. The device according to claim 9, wherein the initial frame boundary detection device comprises:

Input: the received signal after passing through the baseband filter;

Output: The position of the initial frame boundary of the searched strongest cell, range: (0, 30720 * 4

11. The device according to claim 9, wherein the initial frequency acquisition device comprises:

Input: Received signal through the downlink synchronization channel of the baseband filter, the position of the frame boundary; Output: Carrier frequency deviation, Range: (-5KHz, 5KHz).

12. The device according to claim 9, wherein the cell search and selection device comprises:

Input: the signal received through the downlink synchronization channel of the baseband filter, the position of the frame boundary; output: the position and energy of the frame boundary of each cell.

13. The device according to claim 9, wherein the searching and tracking device for multipath signals comprises:

Input: Receive signals through the downlink synchronization channel of the baseband filter, the frame boundary position of the selected cell;

Output: position of two paths;

14. The apparatus according to claim 9, wherein the carrier frequency tracking The device includes:

Input: the signal received by the downlink traffic channel through the baseband filter, the position of the two paths; output: the carrier frequency deviation (-500Hz, 500Hz);

15. The device according to claim 9, wherein the timing frequency tracking device comprises:

Enter: the position of the first path;

Output: Timing frequency deviation (-200Hz, 200Hz);

16. The device according to claim 9, further comprising: a baseband filter, a splitter, an RF VCO, a BB VCO, and a CRC check device;

After the mobile station is turned on, the baseband received signal passes through the 4 baseband filter and enters the initial frame boundary detection device. After detecting the downlink synchronization physical channel, the initial frame boundary information is sent to the initial carrier frequency acquisition device and Cell search and selection device;

The initial carrier frequency acquisition device and the cell search and selection device perform initial carrier acquisition and cell search selection by using information of an initial frame boundary and a received signal of a downlink synchronization channel, until the cell search and selection succeeds, the initial carrier frequency The output signal of the capture device is the initial carrier frequency difference and is used to adjust the VC0 of the radio frequency;

The output signal of the cell search and selection device is the energy and arrival delay of each cell searched, and this information is reported to the upper layer. The downlink multipath search and tracking device uses the frame arrival time and the received signal of the downlink synchronization channel to find Multipath information is used for the timing frequency tracking device, the carrier frequency tracking device, and the reception of the BCH channel and the CRC check device; the output signal of the timing frequency tracking device is used to adjust the baseband timing VCO. ; The carrier frequency tracking device uses multipath information and a received signal of a downlink continuous pilot channel to calculate a carrier frequency difference, which is used to adjust the vco of the radio frequency.