WO2005069649A1 - Procede de recherche de la position du signal synchrone de liaison descendante dans un systeme de communication mobile - Google Patents

Procede de recherche de la position du signal synchrone de liaison descendante dans un systeme de communication mobile Download PDF

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Publication number
WO2005069649A1
WO2005069649A1 PCT/CN2005/000041 CN2005000041W WO2005069649A1 WO 2005069649 A1 WO2005069649 A1 WO 2005069649A1 CN 2005000041 W CN2005000041 W CN 2005000041W WO 2005069649 A1 WO2005069649 A1 WO 2005069649A1
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WIPO (PCT)
Prior art keywords
downlink synchronization
synchronization signal
gain
frequency point
search
Prior art date
Application number
PCT/CN2005/000041
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English (en)
Chinese (zh)
Inventor
Shihe Li
Wensheng Xu
Jian Jing
Hailin Cong
Jiachen Sun
Original Assignee
Da Tang Mobile Communications Equipment Co., Ltd.
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Filing date
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Application filed by Da Tang Mobile Communications Equipment Co., Ltd. filed Critical Da Tang Mobile Communications Equipment Co., Ltd.
Publication of WO2005069649A1 publication Critical patent/WO2005069649A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/04—Speed or phase control by synchronisation signals
    • H04L7/10—Arrangements for initial synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7073—Synchronisation aspects

Definitions

  • the present invention relates to mobile communication technology, and more particularly to a method for quickly completing an initial cell search in a mobile communication system by searching for a position of a downlink synchronization signal.
  • the initial cell search refers to a process in which a user terminal (UE) searches from a start-up and logs in to a suitable cell. This process may be referred to as ICS.
  • a mobile communication system such as a time division duplex-synchronous code division multiple access (TD-SCDMA) system
  • TD-SCDMA time division duplex-synchronous code division multiple access
  • the UE can only log in to the cell after Only then can it obtain more detailed information about the local cell and neighboring cells, and further monitor paging on the network or initiate calls to establish a connection.
  • Fig. 1 shows a 5ms subframe structure of TD-SCDMA.
  • DwPTS downlink pilot time slot
  • every 16 chips are taken as a symbol length. Therefore, the 64 chips of the downlink synchronization signal (SYNC) segment can be considered as 4 symbols, and the GP on the left side of the SYNC segment has 48 chips and 3 symbols, and the GP on the right side of the SYNC segment has 3 symbols. There are 96 chips totaling 6 symbols. Because the SYNC signal can be transmitted at full power, the power of the received SYNC segment signal is high, while the received GP segment signal is only noise and interference signals, and the power is very small.
  • DwPTS downlink pilot time slot
  • SYNC1 is an uplink pilot time slot (UpPTS).
  • the current initial cell search process is shown in FIG. 3, and includes the following steps: Step 301: Put a terminal receiver under a condition of an appropriate gain. Under the appropriate gain, the terminal receiver Frequency points receive and record data for multiple subframes transmitted by the base station.
  • Step 302 Use a characteristic window determination method to search for positions of downlink pilot time slots (DwPTS) in a plurality of subframe data.
  • DwPTS downlink pilot time slots
  • Step 303 Determine whether the approximate position of DwPTS can be obtained. If the approximate position of DwPTS can be obtained, proceed to step 305; if the approximate position of DwPTS cannot be obtained, proceed to step 304.
  • Step 304 It is further determined whether the receiver is saturated, and if the receiver is saturated, step 306 is performed, otherwise step 307 is performed.
  • Step 305 Continue to perform other steps in the initial search of the cell, such as further determining the exact position of DwPTS, etc., that is, fine adjustment of the accurate position of DwPTS is completed, and then this processing flow is ended.
  • Step 306 Reduce the current gain of the receiver by a large step, and return to step 301, continue to receive and record data of multiple subframes transmitted by the base station. At this time, the initial cell search process of steps 301 to 305 will be repeatedly performed until the reception. Machine is not saturated.
  • Step 307 It is determined that there is no working base station at the current carrier frequency, then another frequency point is selected to continue receiving and recording data of multiple subframes transmitted by the base station, that is, selecting another frequency point and performing steps 301 to 306 again.
  • the algorithm used in the initial cell search is to first adjust the receiver gain to an appropriate value. Then the feature window determination method is used to find the position of the synchronization signal (SYNC), and multiple frequency points are searched, and each frequency point is searched multiple times, such as five times.
  • the multiple frequency points can be sorted in advance according to the received power, and the search starts from the frequency point with the highest power.
  • the biggest disadvantage of this search method is: it does not consider the effect on search when there is large signal interference around the terminal receiver, so the initial success rate of the cell is low, that is, there is large signal interference around the user terminal receiver, such as When a mobile user is talking nearby, the uplink signal of the user will erroneously reduce the gain of the receiver to the lowest level, thereby flooding the downlink synchronization signal, making it difficult for the initial search of the cell to succeed.
  • the main object of the present invention is to provide a method for searching for the location of a downlink synchronization signal in a mobile communication system, which can not only quickly complete the initial search of the cell, but also avoid large signal interference and improve the success rate of the initial search.
  • a method for searching a position of a downlink synchronization signal in a mobile communication system the key is to adjust the gain of a terminal receiver to a maximum value, and the method further includes the following steps:
  • the adjusting the gain of the terminal receiver to the maximum value is specifically: dividing the gain control of the terminal receiver into one gear or more, and setting the initial gain of the terminal receiver to the maximum gear of the terminal receiver; If the search fails in C, before reselecting the frequency point, the method further includes: determining whether the current gain is the lowest level of the terminal receiver gain, and if not, then Decrease the gain by one step and return to step A; otherwise, select a new frequency point and return to step 1.
  • the method further includes: performing a correlation operation by using a correlation code to perform a downlink synchronization signal on the approximate position of the largest possible downlink synchronization signal found in step B. Precise position adjustment.
  • step A specifically includes:
  • A1 Receive the complete data of a subframe and calculate the power Pci of each chip in each symbol of the subframe;
  • the method further includes: calculating a logarithm of each power ratio Ri calculated in step A2 with a base of 10 to obtain Ri expressed in dBm.
  • the method further includes: setting the number of consecutively received subframes; after step A3, the method further includes: determining whether a downlink synchronization signal corresponding to the subframe data has been selected for the set number of subframe data at the currently selected frequency point; The approximate position of, if it is, go to step B; otherwise go back to step Al.
  • the set number of consecutive receiving subframes is five.
  • step A2 The step of establishing a feature window described in step A2 is as follows: At each chip position, a feature window is formed with 2 symbols on each side and 4 symbols in the middle.
  • the method further includes: sorting more than one frequency point according to the principle of receiving power from high to small; then the currently selected frequency point is selected from the frequency point with the highest power; re-selecting a frequency point as described in step C is Select the next highest power frequency in sequence.
  • step B specifically includes:
  • B1. Record the minimum power ratio of the downlink synchronization signal of the set number of subframe data and its approximate position; B2. Compare the approximate position of the downlink synchronization signal of the data of the subsequent subframe with the data of the previous subframe;
  • B3. Determine whether the difference between the approximate positions of the two subframes before and after is less than or equal to the set position difference threshold. If so, the downlink synchronization signals in the data of the two subframes are at the same position. The number of subframes, otherwise, the downlink synchronization signals in the data of the two subframes are not in the same position, and the number of subframes with different positions of the downlink synchronization signals is recorded;
  • step B4 Determine whether the set number of subframe data has been compared, and if so, perform step B5, otherwise, return to step B2;
  • B5. Determine whether the number of subframes with the same downlink synchronization signal position is greater than the set required value. If it is greater, the search is successful, and the position of the downlink synchronization signal corresponding to the count value greater than the required value is used as the maximum possibility. The approximate position of the downlink synchronization signal, if not greater than, the search fails.
  • the set number of consecutive received subframes is 5; the threshold of the position difference is 3 chips; and the required value is 2.
  • step B5 the method further includes: setting a success or failure flag.
  • the method for searching the position of the downlink synchronization signal in the mobile communication system is to complete the downlink synchronization by saturating the received signal at the beginning of the initial search of the cell. Therefore, it is a method for searching the approximate position of the synchronization signal DwPTS by using the saturation method. Because the received signal is saturated, the characteristics of the synchronization header are obvious, while the signals on other time slots are also large, but do not have the characteristics of the synchronization header, so it will not affect the search; and because the terminal receiver is in the maximum gain state, it is avoided due to the surrounding The large uplink signal affects the receiver's gain and overwhelms the downlink synchronization signal, so it can effectively avoid the surrounding large signal interference. With the present invention, the initial search of a cell can be completed quickly, conveniently, accurately, and effectively, and the efficiency and accuracy of the initial search of a cell can be improved. Brief description of the drawings
  • FIG. 1 is a structural diagram of a 5ms subframe
  • FIG. 2 is a structure diagram of a feature window with a window length of 8 symbols and 16 chips per symbol
  • FIG. 3 is a block diagram of an initial terminal receiver's initial cell search process
  • FIG. 4 is a flowchart of searching a synchronization signal position by a saturation method according to the present invention
  • Figure 5 is a waveform diagram of time slot TS0 and downlink pilot time slot DwPTS when the received signal is saturated.
  • the method of the present invention is to search the approximate position of DwPTS through the saturation feature window method to complete the downlink synchronization.
  • the core idea of the method is: first lock the frequency to the frequency to be synchronized; then use automatic gain control to make The terminal receiver gain reaches the maximum. At this time, the signal may be saturated, but the saturation does not affect the search of the downlink synchronization feature window. In this case, several subframe data received by the receiver and transmitted by the base station are continuously taken, and the feature window is used.
  • Method to search the synchronization header to determine the approximate position of DwPTS use the correlation code to perform the relevant operation to determine the exact position of DwPTS.
  • each frequency point can be sorted in advance according to the principle of receiving power from large to small, and the search is started from the frequency point with the highest power.
  • the present invention searches the approximate position of DwPTS by using the saturation feature window method, and completes the method for downlink synchronization, including the following steps:
  • Step 401 Adjust the automatic gain control (AGC) of the terminal receiver so that the receiver gain reaches the maximum.
  • AGC automatic gain control
  • the specific method is: The maximum gain of the terminal receiver is achieved through automatic gain control, and the signal may be saturated at this time. In fact, judging whether the receiver is saturated is to judge whether the signal before the receiver's analog-to-digital conversion (A / D) exceeds the full-scale of the digital-to-analog converter. If the received signal exceeds the full-scale of the digital-to-analog converter, the receiver is considered to be receiving The machine is saturated. Signal saturation does not affect the characteristics of the synchronization header. As shown in Figure 5, although the received signal is saturated, the characteristics of the synchronization header are still obvious. The so-called synchronization header characteristics are: The signal power on the SYNC segment in the DwPTS time slot is significantly higher. Yu Qi Signal power on both sides. Although the signal on time slot TS0 is also large, it does not have the characteristics of a synchronization header, so it will not affect the search.
  • tailing occurs when the signal is severely saturated, which affects synchronous search.
  • the gain control can be divided into several levels. First, set the gain to the maximum level and complete the steps.
  • step 402-408 synchronous search, and then determine whether the search is successful, if the search is successful, go to step 410; if the search fails, then reduce the gain by one step, repeat steps 402 ⁇ 408, so that until the receiver gain reaches the lowest level or The search is successful. If the search still fails when the gain is reduced to the lowest range, reselect the frequency point.
  • Steps 402 to 403 Receive a complete data of a subframe length of 400 symbols; and calculate the power Pci of each chip in each symbol in the subframe.
  • Step 404 Establish a feature window at each chip position, that is, at each chip position, a feature window is formed by 2 symbols on each side and 4 symbols in the middle; calculate the power ratio Ri of each feature window, that is: calculate The ratio of the sum of the power of the two symbols on each side to the sum of the power of the middle 4 symbols, where i represents any one chip in each symbol.
  • Step 405 Find the logarithm of the power ratio Ri of each feature window calculated in step 404 with 10 as the base, that is, perform LoglO operation and express Ri in dBm.
  • the logarithm calculation can be implemented by calling the LoglOfloat module in the terminal receiver.
  • Step 406 Select a minimum value minimun (Ri) from all Ri.
  • the chip position corresponding to the minimum value minimun (Ri) is the approximate position sync_pos of the downlink synchronization signal DwPTS, and the accuracy can reach ⁇ 1 symbol.
  • the selection of the minimum value can be performed by the find most module in the terminal receiver.
  • Steps 402 to 406 are performed for each subframe, that is, to determine the approximate position of the downlink synchronization signal DwPTS sync__pos using the saturation feature window method.
  • N subframe data should be fetched continuously, where N is greater than 2. Therefore, after obtaining the approximate position sync_pos of the downlink synchronization signal DwPTS for each subframe, step 407 is performed for judgment.
  • Step 407 Determine whether the approximate position of the downlink synchronization signal DwPTS sync_pos is determined by using the saturation characteristic window method for the received data of the N sub-frames. If yes, go to step 408, otherwise return to step 402.
  • step 408 is performed; otherwise, return to step 402 and continue to take the next sub-frame data.
  • N is equal to 5.
  • Step 408 Find the most probable position from the approximate positions of the N downlink synchronization signals DwPTS.
  • N ⁇ is equal to 5.
  • a feature header method is used to search the synchronization header to find the Ri minimum value of each subframe data, and record the position i where the Ri minimum value is located; compare the i obtained by the next subframe data with the i obtained by the previous subframe data
  • the positions of the downlink synchronization signals in the two sub-frame data are the same, that is, they are considered to be the same position; if the positions of the two i are different from the set position difference threshold, the two sub-frame data are considered to be in the two sub-frame data.
  • the positions of the downlink synchronization signals are different.
  • the threshold of the set position difference can be within 3 chips (including 3 chips), and the alarm value can be arbitrarily set.
  • the number of subframes with the same downlink synchronization signal position is counted, and the number of subframes with different downlink synchronization signal positions is also counted. After a complete comparison of the data positions i of all five subframes is made, it is finally determined that they have the same Whether the number of subframes of the downlink synchronization signal position is greater than the set required value. If the count value of a certain downlink synchronization signal position is greater than the set required value, it means that the search is successful and the count value is greater than the required value. The position of the downlink synchronization signal corresponding to the value is determined as the approximate position of the maximum possible downlink synchronization signal.
  • the set required value may be set to 2, and the required value may be arbitrarily set, as long as it is less than the set number of consecutive received subframes.
  • the position i of the second sub-frame data and the data of the first sub-frame are compared for the first time and there is a difference of 3 chips, then the number of sub-frames having the same downlink synchronization signal position is counted as one; the second comparison of the third sub-frame The position i between the frame data and the second sub-frame data is 4 chips away, and the number of sub-frames having different downlink synchronization signal positions is counted as 1.
  • the third comparison of the fourth sub-frame data and the third sub-frame data Position i with a difference of 3 chips the number of subframes with the same downlink synchronization signal position is counted as 2; the fourth comparison of the i of the .5th sub-frame data and the 4th sub-frame data differs by 3 chips , The number of subframes with the same downlink synchronization signal position is counted as 3 (greater than 2); finally, it is determined that the 3rd, 4th, and 5th subframes have the same downlink synchronization signal position, and the count value is greater than 2, indicating that the initial search of the cell was successful,
  • the positions of the downlink synchronization signals in the 3rd, 4th, and 5th subframes are the approximate positions of the maximum possible downlink synchronization signals.
  • finding the most probable position from the approximate positions of multiple DwPTS is performed in the find most module of the terminal receiver.
  • the find most module can further mark the success or failure of the search, such as the success or failure mark. Represented as Icsfailflag.
  • Step 409 Determine whether the success or failure flag Icsfailflag is equal to 0. If it is equal to 0, the search is successful, and step 410 is performed; otherwise, the search fails, and step 411 is performed.
  • Step 410 Search successfully to find the position of the downlink synchronization signal DwPTS, and save the found The frequency corresponding to the downlink synchronization signal DwPTS, and then ends the processing flow.
  • the found frequency points can be saved in a table, and the frequency points are used in the subsequent steps of the cell search, and the DwPTS position is further fine-tuned by using a correlation code to perform a related operation to determine the precise position of the DwPTS.
  • Step 411 If a synchronization header that meets the conditions is not found, the login fails, that is, the search fails, then this frequency point is filtered, the next next high power frequency point can be selected, and the next high power frequency point can be searched, and steps 401 409 are repeated. Until the sync header is found and login is successful.
  • step 401 If the gain of the terminal receiver is divided into several stages in step 401, and the search is started from the highest stage, in step 411, before selecting the next next high-power frequency point to perform the search again, it is necessary to increase the corresponding judgment to determine whether the current gain is the terminal. Step of the lowest gain of the receiver. If the current gain is the lowest gain of the terminal receiver, select the next next high power frequency point and repeat steps 401-4409; if the current gain is not the lowest gain of the terminal receiver, then Do not change the frequency first, but decrease the gain of the terminal receiver by one step, and repeat steps 402 to 409.
  • the traditional method is to let the receiver work at an appropriate gain when searching for the position of the downlink synchronization signal, because once the receiver is saturated, it will affect the received signal, causing waveform distortion and demodulated signal errors to increase rapidly.
  • the method of the present invention uses the maximum gain of the receiver to complete the downlink synchronization. Specifically, the downlink synchronization is completed when the signal may be saturated under the condition of the maximum gain of the terminal receiver, and the downlink synchronization signal is found before receiving. The receiver works at an appropriate gain. In this way, because the receiver at the maximum gain will not be affected by the surrounding uplink signals to adjust the gain by mistake and overwhelm the downlink synchronization signal, interference from large surrounding signals can be avoided.
  • the method of the present invention Conveniently, accurately and effectively complete the initial search of the cell, and improve the efficiency and accuracy of the initial search of the cell.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)

Abstract

Cette invention concerne un procédé de recherche de la position du signal synchrone de liaison descendante dans un système de communication mobile, lequel procédé consiste à régler le gain du récepteur du terminal sur son niveau maximum. Le procédé de cette invention comprend également les étapes suivantes consistant: A) à rechercher et à obtenir la position approximative du signal synchrone de liaison descendante d'au moins des données de trame au moyen du procédé d'évaluation de fenêtre caractéristique; B) à trouver la position approximative la plus probable du signal synchrone de liaison descendante parmi toutes les positions approximatives obtenues du signal synchrone de liaison descendante; C) à évaluer si la recherche de la position du signal synchrone de liaison descendante est fructueuse et, le cas échéant, à sauvegarder le point de fréquence correspondant au signal synchrone de liaison descendante trouvé; sinon, à sélectionner à nouveau un point de fréquence et à retourner à l'étape A. du fait que le signal de réception est saturé, et à terminer la recherche synchrone de liaison descendante au début de la recherche, ce qui permet de rendre la caractéristique de l'entête synchrone évidente et d'éviter la saturation du signal synchrone de liaison descendante provoquée par un signal de liaison montante plus important affectant le gain du récepteur. Cette invention permet ainsi d'éviter efficacement la perturbation du grand signal et de terminer la recherche initiale de cellule de façon pratique, précise et efficace.
PCT/CN2005/000041 2004-01-12 2005-01-12 Procede de recherche de la position du signal synchrone de liaison descendante dans un systeme de communication mobile WO2005069649A1 (fr)

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CNB2004100005340A CN100337508C (zh) 2004-01-12 2004-01-12 移动通信系统中搜索下行同步信号位置的方法
CN200410000534.0 2004-01-12

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CN1988415B (zh) * 2005-12-21 2010-04-14 大唐移动通信设备有限公司 在cdma通信系统中判断下行导频信号发送方式的方法
CN1972156B (zh) * 2006-12-06 2011-03-23 重庆重邮信科通信技术有限公司 低信噪比条件下下行同步时隙的准确判定方法
CN102255651B (zh) * 2010-05-17 2014-07-02 中兴通讯股份有限公司 一种复帧同步的接收端及方法
CN106102136B (zh) * 2016-08-23 2019-11-05 成都国恒空间技术工程有限公司 一种频分双工移动通信系统下行同步信号的搜索方法

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WO2001067620A2 (fr) * 2000-03-10 2001-09-13 Telefonaktiebolaget Lm Ericsson (Publ) Transmission de signaux de synchronisation liaison montante dans des systemes duplex a repartition dans le temps
CN1315808A (zh) * 2000-03-27 2001-10-03 信息产业部电信科学技术研究院 一种码分多址数字移动通信系统的小区初始搜索方法
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