JP2007521681A - Frame synchronization method using soft decision in general mobile phone system receiver - Google Patents

Abstract

  A Universal Mobile Telephone System (UMTS) receiver performs frame synchronization according to soft decision techniques. As an example, the UMTS receiver first forms a matrix of correlation peak values from at least one received frame. Each row of this matrix represents a possible SSCH code, and each column represents a slot position of the SCH frame. The UMTS receiver then forms a metric for each individual cyclic shift of each of the 64 scrambling code groups that can arise from the matrix of correlation peak values and identifies the metric with the highest value. After the UMTS receiver identifies this highest metric value, it completes frame synchronization using the scramble code group and the corresponding offset.

Description

  The present invention generally relates to a radio receiving apparatus, and more particularly, to a UE (User Equipment) in a radio system based on a spread spectrum such as a universal mobile telephone system (UMTS).

  A basic time unit in a UMTS radio signal is a radio frame of 10 milliseconds (ms), and one frame is divided into 15 slots, and one slot is 2560 chips long. The UMTS radio signal from the cell (ie, base station) to the UMTS receiver is referred to as the “downlink signal” and the reverse radio signal is referred to as the “uplink signal”. When the UMTS receiver is first powered on, it performs a “cell search” to search for a cell to communicate with. In detail, the UMTS receiver first looks for a downlink synchronization channel (SCH) transmitted from a cell and synchronizes with that cell at the slot level and frame level, as described below. A unique scramble code group for the cell is identified. Only after this cell search is successful, voice / data communication can be started.

  For cell search, the SCH (Synchronization Channel) is a sparse downlink channel that is active only during the first 256 chip periods of each slot. The SCH includes two subchannels, that is, a primary SCH (Primary SCH: PSCH) and a secondary SCH (Secondary SCH: SSCH). The PSCH 256 chip sequence, ie, the PSCH code, is the same in all slots of the SCH for all cells. In contrast, the 256-chip sequence of SSCH, ie, the SSCH code, is different in each of the 15 slots of the radio frame and is used to identify one of the 64 possible scramble code groups. In other words, each SCH radio frame repeats a scramble code group sequence corresponding to each transmission cell. Each SSCH code is used from a code system consisting of 16 possible SSCH codes.

  The UMTS receiver first implements slot synchronization by PSCH as part of the cell search. In this regard, the UMTS receiver correlates each received sample of the received PSCH with a 256-chip sequence of known PSCH (which is the same for all slots) and determines the slot reference time based on the position of the correlation peak. . Once this slot reference time is determined, the UMTS receiver can be slot synchronized to identify when each slot starts in the received radio frame.

  After slot synchronization, the UMTS receiver stops PSCH processing and starts SSCH processing. As described above, the SSCH channel repeats the scramble code group sequence corresponding to the transmission cell. Thus, in order to achieve frame synchronization, the UMTS receiver first identifies which of the 64 possible scrambling code groups are received, and then the frame estimated by the UMTS receiver. It is necessary to find the number of slots at the offset between the start and the actual frame start. A common method uses a hard decision technique. For example, in each slot, a correlation between the received signal and 16 SSCH codes of the above code system is taken. The SSCH code with the strongest correlation is used as an estimate of the received SSCH code for that slot. The resulting estimate of 15 SSCH codes over 15 slots is compared with all 15 possible shifts of all 64 possible scramble code groups to obtain a received scramble code. Groups are identified and frame offsets are identified. (In UMTS, each scramble code group sequence has its own cyclic shift, that is, any scramble code group sequence has a cyclic shift and any other scramble code group sequence has a cyclic shift. If not equal, defined a priori.) By identifying the scramble code group, the UMTS receiver allows other downlink channels of the cell (eg, Common Pilot Channel (e.g., Common Pilot Channel ( All of the CPICH) etc. can be descrambled and voice / data communication can be started.

  Unfortunately, the above-described SSCH part of the cell search process is the most time consuming part. In particular, because of the low signal-to-noise ratio when the UMTS system is operating, the UMTS receiver can determine a predetermined number, eg, 10 in order to better estimate the transmission sequence of 15 SSCH codes from the cell. 20 received radio frames need to be processed. Therefore, since the length of each radio frame is 10 ms, the user may feel a delay of at least about 100 to 200 ms before voice / data communication can be started.

(Summary of Invention)
As described above, the UMTS receiver performs the SSCH portion of the cell search by processing a predetermined number of received radio frames. However, using a hard decision technique that identifies the received SSCH code in each slot can degrade performance under severe channel conditions, and the cause of this decrease is It has been found that when a determination is made as to which SSCH code has been received, information about other possible SSCH codes received for that slot is discarded. For example, the hard decision technique selects the SSCH code corresponding to the largest correlation peak. Thus, if the received signal is compared to one of the 16 possible SSCH codes, the value of the largest correlation peak is 1025, which may correspond to the next largest correlation peak (and the correct SSCH code). If the value of (correlation peak) is 1020, subsequent information regarding the next largest correlation peak (and correct SSCH code) is discarded. Thus, in some situations (particularly when operating under severe channel conditions), an incorrect SSCH code will be identified when it is received by the wireless receiver.

  Thus, in accordance with the principles of the present invention, a wireless receiver receives a plurality of codewords, i.e., synchronization words comprised of symbols, over a fixed number of time slots. At this time, S symbols (S> 1) correspond to one synchronization word adopted from a set of M (M> 1) synchronization words. Further, the wireless receiver implements frame synchronization for the fixed number of time slots by estimating the one synchronization word as a function of the metric value corresponding to each of the M synchronization words.

  According to an embodiment of the present invention, a UMTS receiver is part of a UMTS user equipment (UE) and incorporates a processor and a corresponding memory. The processor first performs slot synchronization using the PSCH. After implementing slot synchronization, the processor implements frame synchronization by forming a matrix of correlation peak values from at least one received frame in the corresponding memory. Each row of this matrix represents a possible SSCH code, and each column represents a slot position of the SCH frame. The processor then forms a metric for each individual cyclic shift of each of the 64 possible scramble code groups from the matrix of correlation peak values and identifies the metric with the highest metric value. After identifying this highest metric value, the processor completes frame synchronization using the scramble code group and the corresponding offset.

  In accordance with another embodiment of the present invention, the UMTS receiver performs frame synchronization according to a soft decision (soft decision) method. As an example, the UMTS receiver first forms a matrix of correlation peak values from at least one received frame. Each row of this matrix represents a possible SSCH code, and each column represents a slot position of the SCH frame. The UMTS receiver then forms a metric from the matrix of correlation peak values for each individual cyclic shift of each of the 64 possible scramble code groups and identifies the metric having the highest value. After identifying this highest metric value, the UMTS receiver completes frame synchronization using the scramble code group and the corresponding offset.

  Except for the concept of the present invention, each element shown in each figure is well known, and detailed description thereof will be omitted. In addition, it is assumed that the wireless communication system based on UMTS is familiar, and detailed description thereof is also omitted. For example, except for the concept of the present invention, spread spectrum transmission / reception, cell (base station), UE (user equipment), downlink channel, uplink channel, and RAKE receiver are well known and described. Is omitted. Furthermore, the concept of the present invention can be implemented using conventional programming techniques, but the description of the conventional programming techniques is also omitted. Moreover, the same number in each figure represents the same element.

  FIG. 1 illustrates a portion of a UMTS wireless communication system 10 in accordance with the principles of the present invention. The cell (ie, base station) 15 broadcasts a downlink synchronization channel (SCH) signal 16 including the aforementioned PSCH and SSCH subchannels. As mentioned above, the SCH signal 16 is used by UMTS UEs to synchronize as a prerequisite for voice / data communication. For example, the UE processes the SCH signal during the “cell search” operation period. In this example, the UE 20, for example, a cellular phone, starts a cell search, for example, when the power is turned on. The purpose of the cell search operation includes (a) identifying the scramble code group of the cell (eg, cell 15) and (b) synchronizing to cell transmission at the slot and frame level of the UMTS radio frame. . According to the principle of the present invention, as will be described later, the UE 20 identifies a scramble code group by a soft decision technique and realizes frame synchronization. In the following, the concept of the present invention will be described as an example of this initial cell search, that is, an example based on the cell search when the UE 20 is powered on. The present invention is not limited and can be applied to other cell search cases, for example, when the UE is in the “idle mode”.

  FIG. 2 illustrates a block diagram of a portion of UE 20 in accordance with the principles of the present invention. The UE 20 includes a front end 105, an analog / digital (A / D) converter 10, a cell search unit 115, a searcher unit 120, a RAKE receiver 125, a host interface block 130, and a processor 135. Yes. In addition to the concept of the present invention, each block shown in FIG. 2 may include other elements well known to those skilled in the art, but the description thereof will be omitted for the sake of brevity. . For example, the A / D converter 110 may include a digital filter, a buffer, and the like.

  The front end 105 receives a radio frequency (RF) signal 101 transmitted from the cell 15 (FIG. 1) via an antenna (not shown), and a baseband analog signal representing the PSCH and SSCH subchannels. 106 is output. The A / D converter 110 samples the baseband analog signal 106 and outputs a stream of received samples 111. The received sample 111 can be supplied to three components, that is, the cell search unit 115, the searcher unit 120, and the RAKE receiver 125. Cell search unit 115 processes PSCH and SSCH subchannels in accordance with the principles of the present invention, as described below. If the cell search is successful, then the searcher unit 120 obtains the value of the received sample and assigns the multipath to each finger of the RAKE receiving device 125. For example, the RAKE receiving device 125 combines data from a plurality of transmission paths and outputs each symbol. Each symbol is then decoded by a decoder (not shown) for voice / data communication. Since only the cell search unit 115 is related to the concept of the present invention, further description of the searcher unit 120 and the RAKE receiving device 125 is omitted. The host interface block 130 exchanges data between the above-described three components and the processor 135. In this example, the processor 135 transmits the processing result of the cell search unit 115 via the signal path 134. Receive. In this example, the processor 135 is a processor controlled by a stored program, for example, a microprocessor, and includes a memory 140 that stores the program and data.

  FIG. 3 illustrates a block diagram of the cell search unit 115. Cell search unit 115 includes PSCH unit 205 and SSCH unit 210. Also, FIG. 4 shows an example of a flowchart representing a process in which the cell search unit 115 of FIG. 3 processes the downlink PSCH and SSCH subchannels according to the principle of the present invention. The processor 135 of the UE 20 initiates a cell search and, in step 305, attempts to achieve slot synchronization by processing the downlink PSCH subchannel. Specifically, the processor 135 activates the PSCH unit 205 via the signal path 206 to process the received samples 111 as is well known to those skilled in the art. For example, since the downlink PSCH subchannel is a known PSCH 256 chip sequence, i.e., a PSCH code, that occurs periodically (i.e., repeats in each slot of the downlink SCH signal), the PSCH portion 205 includes the received samples 111 and The correlation with the PSCH code is taken and the corresponding peak correlation value is output. In this regard, the PSCH unit 205 includes a matched filter (not shown) and a buffer (not shown) that stores an output signal of the matched filter. The PSCH unit 205 supplies the peak correlation value to the processor 135 via the signal path 206. This peak correlation value may be averaged over several slots of the received radio frame, eg, 4 to 20 slots, to reduce the possibility of “false lock”. (Since PSCH synchronization uses several slots instead of several frames, it is much faster than the above-mentioned prior art SSCH frame synchronization.) If the peak correlation value is below a predetermined threshold, the processor 135 controls the PSCH unit 205 to continue processing the received signal and continue searching for cells. On the other hand, when the peak correlation value is larger than the predetermined threshold, the UE 20 completes the slot synchronization. Alternatively, slot synchronization can be considered complete when the peak correlation value exceeds the next highest correlation value by a predetermined additive or multiplicative factor.

When slot synchronization is achieved in step 305, the UE 20 needs to identify which of the 64 scramble code groups are being used by the cell 15. At this time, each scramble code group is identified by a unique sequence of 15 SSCH codes. Here, one set of scramble code groups is formed by 64 scramble code groups. When one scramble code group is formed, each SSCH code, that is, an SSCH symbol, is used from 16 symbols of one code system from 1 to 16, for example. Accordingly, in one scramble code group example, for example, group 1 may include the following 15 SSCH symbols.
[1, 1, 2, 8, 9, 10, 15, 8, 10, 16, 2, 7, 15, 7, 16]
On the other hand, in another example of the scramble code group, for example, group 2 may include the following 15 SSCH symbols.
[1, 1, 5, 16, 7, 3, 14, 16, 3, 10, 5, 12, 14, 12, 10]

  In accordance with the principles of the present invention, the processor 135 identifies the scramble code group and implements frame synchronization in step 310 of FIG. 4 according to the soft decision based technique. Specifically, the processor 135 forms one metric set for each of the scramble code groups, as described below. Here, each metric set includes a plurality of metric values, and each metric value corresponds to an individual cyclic shift of the respective scramble code group. The processor 135 then selects the largest metric value from all metric sets. The specific metric set with the largest value selected identifies the scramble code group and the cyclic shift corresponding to the selected metric value, identifies the frame offset, and implements frame synchronization. For the sake of brevity, error conditions are not shown in the flowchart. For example, if the UE 20 loses slot synchronization while attempting frame synchronization, the cell search described above unfortunately starts over from the beginning.

FIG. 5 shows a configuration example of the SSCH unit 210 according to one feature of the present invention. The SSCH unit 210 includes a correlator bank 220 including K correlators, that is, correlators 220-1 to 220 -K, and a memory 230. Each correlator correlates each received sample 111 in one time slot with a certain number of codewords C ₁ to C _K. Accordingly, correlator bank 220 provides K correlator values to memory 230 for each time slot. The memory 230 stores the correlator values over S reception time slots. That is, the memory 230 stores S × K correlator values. Note that these correlator values may be stored in another memory, for example, the memory 140. For example, in this example, the codeword is an SSCH code and K = 16, ie, one correlator is provided for each possible value of the SSCH code, and S = 15, and the memory 230 stores correlator values for one frame, that is, 240 values. An example of storing correlator values in the memory 230 over one frame can be organized as a matrix of correlator values or a table 212 as shown in FIG. For the sake of brevity, only the form of the matrix 212 is shown in FIG. That is, the actual correlator peak value is not shown in each individual cell of the matrix 212. Each row of matrix 212 corresponds to 16 SSCH codes, i.e. one of SSCH1 to SSCH16, and each column of matrix 212 has 15 time slots, i.e. one of slot 1 to slot 15. It corresponds. In other words, each column of the matrix 212 stores each correlator value, and further, each correlator value is the probability that a particular one of the SSCH codes was received in that time slot, or a confidence A measure of confidence is substantially represented. For example, if SSCH code 1 has 1000 correlation peaks for a time slot and SSCH code 2 has only 500 correlation peaks for that same time slot, the time In the slot, the reliability of transmission of SSCH code 1 instead of SSCH code 2 is remarkably high. Thus, according to one aspect of the invention, the matrix of correlator values collects and maintains information about all possible SSCH codes received over at least one frame, and thus, as described below, this correlation The instrument matrix improves the ability to acquire the SSCH channel when operating under severe channel conditions.

  FIG. 7 shows an example flow chart used in implementing step 310 of FIG. 4 and in accordance with the principles of the present invention. Specifically, in step 350, the SSCH unit 210 determines a plurality of correlation values for each of the possible SSCH codes received over at least one frame, ie, 15 time slots, from the correlator value matrix 212 described above. To remember. (It should be noted that correlation data for a plurality of frames may be accumulated and stored in the correlator value matrix.) In step 355, the processor 135 stores in the memory 230 via the signal path 211 of FIG. Access and use each value stored in the correlator value matrix 212 to determine a table of metrics values, ie a matrix (metric matrix). In this regard, FIG. 8 illustrates a metric matrix 213. Also in FIG. 8, only the structure of the matrix 213 is shown for the sake of brevity of description, that is, the actual metric value is not shown in each individual cell of the matrix 213. Each row of the metric matrix 213 corresponds to one of the predetermined scramble code groups, and each column of the metric matrix 213 corresponds to an individual cyclic shift of the scramble code group. As can be seen from FIG. 8, each term in the metric matrix 213 associates metric values with individual cyclic shifts of individual scramble code groups. Therefore, each row of the metric matrix 213, that is, each scramble code group, corresponds to one metric set, and this metric set includes, for example, a scramble code as shown in FIG. A plurality of metric values corresponding to different cyclic shifts of the group are included. The processor 135 determines each metric value as a sum of each confidence value for the sequence for a given shift of a given scramble code group. After determining the metric matrix, processor 135 selects the highest metric value in the metric matrix at step 360. Since each metric value corresponds to an individual cyclic shift of an individual scramble code group, processor 135 in step 365 scrambles the code group corresponding to the highest metric value (ie, the corresponding scramble code group). In step 370, the slot offset corresponding to the highest metric value (ie, the corresponding column) is determined to complete frame synchronization.

  As a further illustration, consider the following simplified example. Assume that one SSCH code system consists of four codes, that is, symbols {1, 2, 3, 4}, and the number of time slots in each frame is two. Further, assume that each scramble code group is defined as follows. Group 1 = [1,4], Group 2 = [1,2], Group 3 = [3,1], and Group 4 = [2,3]. For example, from this assumption, group 1 is defined as SSCH symbol sequences 1 and 4.

  Therefore, the SSCH unit 210 includes four correlators, each correlator for each received sample 111 in each time slot with four possible symbols {1, 2,. Compare with 3, 4}. According to step 350 of FIG. 7, SSCH section 210 stores a plurality of correlation peak values for each possible SSCH code received in each of the two time slots in the correlator value matrix. FIG. 9 illustrates a matrix of correlator values for two specific time slots. As shown in FIG. 9, for example, for symbol 1, a correlator value of 2 corresponds to the probability that symbol 1 was received in the first time slot, and a correlator value of 7 Corresponds to the possibility that symbol 1 was received in the second time slot. Next, according to step 355 of FIG. 7, the processor 135 forms a metric matrix as shown in FIG. 10 for each scramble code group. For example, for group 1, processor 135 first determines a metric corresponding to a 0 cyclic shift. This process is performed as follows. That is, referring to the correlator value matrix, the correlator value (value 2) corresponding to symbol 1 in the first time slot and the correlator value (6 corresponding to symbol 4 in the second time slot). And a metric value of 8 is obtained. Further, this calculation is shown in FIG. Next, the processor 135 similarly determines the remaining metric values. For example, for group 1, the metric corresponding to one cyclic shift, ie the probability that the received sequence is actually [4,1] is equal to 10.

  This example will now be described. Returning to FIG. 7, after the metric matrix is determined, the processor 135 selects the highest metric value in the metric matrix at step 360. This is a value of 33 in this example. As can be seen from FIG. 10, this value of 33 corresponds to a row corresponding to group 4 and a column corresponding to a shift of 0. Accordingly, processor 135 selects group 4 as the scramble code group at step 365 and identifies at step 370 that a shift of 0 is required for frame synchronization.

  Upon successful completion of the SSCH process in step 370, the UE 20 is used for other downlink channels (eg, frequency synchronization of the cell) by identifying the scramble code group of the cell 15, and All of the common scramble codes (including the common pilot channel (CPICH) that can specify the actual scramble code for the cell) can be descrambled from the identified scramble code group, and voice / data communication can be started.

  FIG. 12 shows an embodiment of a pseudo code according to the principle of the present invention. In the pseudo code of FIG. 12, the notation rx_data is 256 received samples for a given slot, SSC [i, j] is the jth sample in the i th SSCH code, and group_seq is all possible occurrences. A matrix look-up table of 64 scramble code group sequences, group is the identified transmit code group, and offset is the frame slot offset.

  FIGS. 13 and 14 illustrate simulation results for a UMTS receiver according to the principles of the present invention. FIG. 13 shows a simulation result when there is no noise. In FIG. 13, each value represents each metric value of the metric matrix. The large peak 401 represents the largest metric value and identifies the correct group and the scramble code group number 10 having an offset of 0 which is an offset. In contrast, FIG. 14 shows simulation results for a very low signal to noise ratio. Also in FIG. 14, each value represents each metric value of the metric matrix. The large peak 402 represents the largest metric value, which also identifies the correct group and the scramble code group number 10 having an offset of zero. Although each metric in FIG. 14 appears to be accompanied by noise, the highest peak 402 is actually 11% higher than this next highest peak. In the case of the same simulation as illustrated in FIG. 14, the general hard decision algorithm did not work well, and a group 2 having an offset of 1 was mistakenly identified. Therefore, unlike the method based on the hard decision, the technique based on the soft decision described above does not discard the received information about the possible SSCH code, that is, the data. Therefore, the soft decision method according to the concept of the present invention can achieve good performance even under severe channel conditions.

  As described above, according to the principle of the present invention, the radio receiver can identify the scramble code group by a technique based on soft decision and realize frame synchronization. This soft decision based technique provides a method and apparatus for implementing a robust secondary cell search in a UMTS receiver. In fact, the storage device, i.e. memory expansion and space expansion is required, but the SSCH channel is acquired when the wireless receiver operates under severe channel conditions (e.g. when the signal to noise ratio is very low). Function to improve. Although the inventive concept has been described based on the case of the initial cell search process, the inventive concept can be applied to any part of a radio processing operation that processes a downlink channel, such as an SSCH subchannel. Applicable.

  The foregoing description is merely illustrative of the principles of the present invention and those skilled in the art will not be explicitly described herein but embody the principles of the present invention and depart from the spirit of the invention. Various alternative configurations could be devised without falling within the scope of the present invention. For example, although each functional part has been described as individual, a processor (eg, a microprocessor or digital) controlled on one or more integrated circuits (ICs) and / or stored programs. Signal processor (DSP)). Similarly, the concept of the present invention has been described for systems based on UMTS, but can also be applied to other communication systems. Accordingly, various modifications can be made to the above-described embodiments, and other configurations can be devised without departing from the spirit and scope of the present invention as defined by the claims of the present application. It will be possible.

FIG. 1 is a diagram illustrating a portion of an example of a wireless communication system in accordance with the principles of the present invention. FIG. 2 is a diagram illustrating an embodiment of a wireless receiver in accordance with the principles of the present invention. FIG. 3 is a diagram illustrating an embodiment of a wireless receiver in accordance with the principles of the present invention. FIG. 4 is a diagram showing an example of a flowchart according to the principle of the present invention. FIG. 5 is a diagram showing an embodiment of the configuration of a correlator according to the principle of the present invention. FIG. 6 is a diagram illustrating an example of a matrix configuration for storing correlator values in accordance with the principles of the present invention. FIG. 7 is a diagram illustrating an example of another flowchart in accordance with the principles of the present invention. FIG. 8 is a diagram showing a configuration example of a metric matrix according to the principle of the present invention. FIG. 9 is a diagram for further explaining each matrix in FIG. 6 and FIG. FIG. 10 is a diagram for further explaining each matrix in FIGS. 6 and 8. FIG. 11 is a diagram for further explaining each matrix in FIGS. 6 and 8. FIG. 12 is a diagram showing an example of a pseudo code according to the principle of the present invention. FIG. 13 is a diagram illustrating an example of a simulation result. FIG. 14 is a diagram illustrating an example of a simulation result.

Claims (14)

A method used for a wireless receiver,
A signal (111) representing S (S> 1) symbols corresponding to one synchronization word used from a set of M (M> 1) synchronization words is transmitted over a certain number of time slots. Receiving, and
Realizing frame synchronization for the fixed number of time slots by estimating the one synchronization word as a function of a metric value corresponding to each of the M synchronization words;
Said method. Said step of realizing frame synchronization comprises:
K units each representing the received signal in one of the S time slots and each one of K (K> 1) received possible symbols Storing a value for each time slot;
Obtaining a set of metrics for each of the M synchronization words from the stored instrument values;
Selecting the highest metric value of all of the determined sets of metrics;
From the selected highest metric value, (a) one of the M synchronization words is determined as an estimate of the received synchronization word, and (b) a time slot offset is determined to determine the constant Realizing frame synchronization for a number of time slots;
The method of claim 1 comprising: Each of the M sync words includes a unique sequence of symbols, and the step of determining a set of metrics for each of the M sync words comprises:
Performing S cyclic shifts of the synchronization word;
For each cyclic shift, adding a respective instrument value corresponding to the pattern of symbols in each of the S time slots;
The method of claim 2 comprising:   The method of claim 1, wherein the symbols are Universal Mobile Telephone System (UMTS) Secondary Synchronization Channel (SSCH) symbols and the M synchronization words are 64 scramble code group sequences. Said step of realizing frame synchronization comprises:
Forming a matrix of correlator peak values from received synchronization words, wherein each row of the matrix corresponds to one of a plurality of received possible SSCH symbols, and each column of the matrix is the fixed number of Corresponding to one of the time slots, each of the correlator peak values being a respective one of the S received symbols and a respective one of a plurality of received possible SSCH symbols in the corresponding time slot, The matrix forming step representing the correlation of:
Forming a metric value for each cyclic shift of each of the 64 scramble code groups from the matrix of correlator peak values;
Identifying the highest metric value;
From the identified highest metric value, (a) one of the 64 scramble code group sequences is identified as an estimate of the received synchronization word; and (b) frame synchronization for the fixed number of time slots. Identifying a corresponding cyclic shift used to achieve
The method of claim 4 comprising: Said step of forming a metric value comprises:
Forming a metric matrix, wherein each row of the metric matrix corresponds to one of the 64 scramble code groups, and each column of the metric matrix corresponds to one cyclic shift. The metric matrix forming step;
Determining each metric value by adding each corresponding correlator peak value associated with an individual cyclic shift of an individual scramble code group; and
The method of claim 5 comprising: A method used for a universal mobile telephone system (UMTS) receiver comprising:
Receiving a signal representative of a secondary synchronization channel (SSCH) transmitted from a UMTS transmitter, wherein the SSCH represents a sequence of S SSCH symbols corresponding to a scramble code group corresponding to the UMTS transmitter; Receiving the signal, transmitting over S time slots, wherein the corresponding scramble code group is adopted from a set of 64 scramble code groups;
Storing data representing the probability that each of the K (K> 1) SSCH symbols was received in each of the S time slots;
Obtaining each metric value representing the probability that an individual cyclic shift of each of the 64 scramble code groups has been received from the stored data;
Identifying the highest metric value;
From the highest metric value, (a) a scramble code group corresponding thereto is identified as a scramble code group of the UMTS transmitter, and (b) a time slot offset from a cyclic shift corresponding to the highest metric value. Realizing frame synchronization for the S time slots by identifying
Said method. Said step of storing data comprises:
Correlating each of the K SSCH symbols with the received signal in each of the S time slots and providing K corresponding correlator values;
Storing the K corresponding correlator values associated with the S time slots;
The method of claim 7 comprising: A universal mobile telephone system (UMTS) device comprising:
A front end (105) for receiving a radio signal representing a secondary synchronization channel (SSCH) transmitted from a UMTS transmitter and supplying a stream of samples, wherein the SSCH is a scramble code group corresponding to the UMTS transmitter Transmitting a sequence of S SSCH symbols corresponding to S over time slots, wherein the corresponding scramble code group is adopted from a set of 64 scramble code groups. (105)
A memory (230) storing data representing the probability that each of the K (K> 1) SSCH symbols was received in each of the S time slots;
(A) obtaining each metric value representing the probability that an individual cyclic shift of each scramble code group of the 64 scramble code groups is received from the stored data; and (b) obtaining the highest metric value. Identifying (c) from the highest metric value, (1) identifying the corresponding scramble code group as the scramble code group of the UMTS transmitter, and (2) cyclic shift corresponding to the highest metric value A processor (135) that implements frame synchronization for the S time slots by identifying a time slot offset from
Said UMTS device.   The data representing probability is a correlator value, and (a) K corresponding correlations are obtained by correlating each of the K SSCH symbols with each sample corresponding to each of the S time slots. 10. The UMTS of claim 9, further comprising: a bank of correlators that provides a correlator value and (b) stores the K corresponding correlator values associated with each of the S time slots in the memory. apparatus.   The processor determines a metric value for an individual cyclic shift for each scramble code group by adding each correlator value corresponding to a pattern of symbols in each of the S time slots. 10. The UMTS device according to 10. A device used in a wireless receiver,
Each frame receives a radio signal representing a sequence of a plurality of frames for transmitting a symbol sequence corresponding to a priori as a radio signal source over a certain number of time slots. A front end (105) for supplying a stream of
A memory (140) for storing a table of metric values, wherein each row of the table corresponds to one of M (M> 1) synchronization symbol sequences, and each column of the table is M The memory (140) corresponding to a cyclic shift of the sequence of:
(A) identifying the highest metric value stored in the table of metric values; (b) from the identified highest metric value, (1) one of the M synchronization symbol sequences is received symbols A processor (135) that implements frame synchronization for the received radio signal by identifying as a sequence estimate and (2) identifying a corresponding cyclic shift;
Including the device.   A memory (230) for storing a table of correlation values, each row of the table corresponding to one of a plurality of received possible symbols, wherein each column of the table is for the fixed number of time slots; Said memory (230) corresponding to one, wherein each of said correlation values is a correlation between each sample in a corresponding time slot and a respective one of said plurality of received possible symbols. 13. The apparatus of claim 12, wherein the metric value table is obtained from the correlation value table.   The processor determines a metric value for each individual cyclic shift of the M sequences by adding each correlation value corresponding to a pattern of symbols in each of the S time slots. Item 14. The device according to Item 13.

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