KR100313928B1 - Random Access Channel Synchronized Method in Communication System - Google Patents

Abstract

The present invention relates to a random access channel synchronization method in a mobile communication system in which a peak position for a PN code used in a conventional preamble section is searched and then a random access channel is synchronized using timing information obtained at this time. As described above, according to the present invention, a correlation between an input signal and a PN code is performed, and then a correlation between the preamble sequence and the maximum correlation value obtained in the first step is performed. A second step of selecting, a third step of performing timing estimation using the maximum correlation value, and at the same time performing the first step during the remaining period of the preamble, and a predetermined threshold value obtained in the third step. A fourth step of determining whether there is a correlation value including the maximum correlation value among excess correlation values; and a fifth step of transmitting timing information estimated in the third step if it is determined that the correlation value is included. Is done.

Description

Random Access Channel Synchronized Method in Communication System

The present invention relates to a random access channel synchronization method in a mobile communication system. In particular, the conventional random access channel synchronization method is improved in an asynchronous CDMA mobile communication system to reduce the timing error during synchronization of a random access channel to find an accurate offset position. A random access channel synchronization method in a mobile communication system suitable for betting.

In general, when a user of a mobile terminal applies power to a terminal to make a phone call, synchronization of a random access channel must be preceded before another operation between the terminal and a base station that manages the location of the terminal. The synchronization for the random access channel is performed using a random access burst receiver provided in the base station.

1 is a diagram showing the configuration of a frame used in a conventional random access channel.

In FIG. 1, each frame of the random access channel is allocated to 16 slots, and each slot is transmitted with an offset of 1.25 ms.

In addition, each frame of each random access burst is composed of a 1 ms preamble, a 0.25 ms pause, and a 10 ms message part as shown in FIG. 1. The preamble is a preamble sequence structure composed of symbols having a length of 16.

According to the current communication standard, 16 preamble sequences are provided, and each preamble sequence has a property that is orthogonal to each other. In addition, each symbol has a characteristic of spreading with a PN code having a period of 256. At this time, the spreading method is performed by taking a binary product of 256 PN codes for each symbol.

The conventional random access channel synchronization method is performed by despreading data transmitted from a terminal and using the result to determine which preamble sequence the received signal has.

2 is a block diagram of a conventional random access burst receiver.

Referring to FIG. 2, a conventional random access burst receiver includes a matched filter 10 for correlating an input signal with a PN code used for spreading, and a correlator for correlating a signal output from the matched filter 10 with a specific preamble sequence. (20), a peak detector (30) for detecting the largest value of the correlation value output from the correlator (20), and a timing estimator (40) for estimating timing information using the output signal of the peak detector (30). And a rake receiver 50 which combines and receives the signals sequentially provided from the timing estimator 40.

The operation of the conventional random access channel synchronization method configured as described above is as follows.

The received received data is applied to the matching filter 10 to perform correlation on the entire PN code. The matched filter 10 correlates with the input signal and the PN code (256 cycles of PN codes in the present invention) used for spreading. The output signal of the matched filter 10 is applied to the correlator 20 to be multiplied by a preamble sequence and accumulated in symbol units. The accumulated value is applied to the peak detector 30 after 16 symbols of the preamble sequence period. The peak detector 30 extracts a correlation value having the largest value among the input correlation values and provides the extracted value to the timing estimator 40. The timing estimator 40 uses the output of the peak detector 30 to find the preamble sequence and the peak timing to start timing estimation for estimating timing information to be used by the RAKE receiver 50.

For this operation, since the DLL (Delay Locked Loop) tracking method is generally used, peak timing information must be received. As shown in FIG. 1, the operation of the DLL does not occur during the preamble and there is no signal in the pause period. It starts with wealth.

Here, the timing information found by the peak detector 30 is made in units of PN codes. It is important to find more precise timing information, because the accuracy of this timing information decisively affects the reception sensitivity. The operation of finding such timing information is called time tracking.

The rake receiver 50 transmits each peak timing information to the rake receiver 50 by using the timing estimator 40 to output not only the maximum value but also the N maximum values of the timings of the peak detectors 30 of FIG. 2. The receiver 50 is a receiver that receives the combined signal, and thus has a better sensitivity, that is, a high signal-to-noise ratio.

However, in the conventional method of synchronizing a random access channel signal, since the operation of the DLL estimating timing is started in the message portion after the timing offset, there is not enough time to track more precise timing during the timing estimation period. Therefore, the sensitivity of receiving the data transmitted from the terminal is likely to be lowered because the offset position for each slot is not accurately sensed. After all, this problem causes a failure to provide a good quality communication service.

An object of the present invention is to improve the prior art described above, the mobile communication for synchronizing the random access channel using the timing information obtained at this time after searching the peak position for the PN code used in the conventional preamble section It is to provide a random access channel synchronization method in a system.

In order to achieve the above object, according to a feature of the present invention, a first step of performing a correlation on the preamble sequence for a portion of a given preamble section, and then performing correlation with the input signal PN code, and the first step A second step of selecting a maximum correlation value among the correlation values obtained from the above step, a timing estimation using the maximum correlation value, and a third step of performing the first step for the remaining period of the preamble, A fourth step of determining whether there is a correlation value including the maximum correlation value among correlation values exceeding the predetermined threshold value obtained in step 3, and if it is determined that the determination result is included, The fifth step is to transmit the timing information.

1 is a diagram showing the configuration of a frame used in a conventional random access channel.

2 is a block diagram of a conventional random access burst receiver;

3 is a view showing the configuration of a frame used for a random access channel according to the present invention.

4 is a block diagram of a random access burst receiver in accordance with the present invention.

* Description of Symbols for Important Parts of Drawings *

100: matching filter 200: correlator

210: multiplier 220: adder

230: delay 300: peak detector

400: Timing Estimator 500: Rake Receiver

Hereinafter, an operation of a random access channel synchronization method according to an embodiment of the present invention will be described.

3 is a diagram showing the configuration of a frame used for a random access channel according to the present invention.

Referring to FIG. 3, each frame of the random access burst according to the present invention has a 1 ms preamble, a 0.25 ms pause, and a 10 ms message part, but the preamble is a peak searcher 60. ), The preliminary 70 and the timing estimator 80 are further subdivided.

In an embodiment of the present invention, the start point of the DLL is advanced before the end of the preamble sequence so that the reception performance of the message unit is not deteriorated until the timing tracking is stabilized, and the peak timing is accelerated for this purpose.

4 is a block diagram of a random access burst receiver according to the present invention.

Referring to FIG. 4, the random access burst receiver of the present invention includes a matched filter 100 for correlating an input signal with a PN code used for spreading, and a correlation for correlating a signal output from the matched filter 100 with a specific preamble sequence. A peak detector 300 that detects the largest value of the correlation value output from the correlator 20, the output signal of the peak detector 300, and an initial input signal to estimate timing information. The timing estimator 400 and the rake receiver 500 which combines and receives the signals sequentially provided from the timing estimator 400 are configured.

In the random access burst receiver according to the present invention configured as described above, the output of the matched filter 100 is provided to the correlator 200 during the peak searcher 60 of the preamble to perform correlation (ST1). In this case, after L symbols of the 16 symbols of the preamble have elapsed, the peak detector 300 generates peak timing which is the maximum timing information among the correlation values correlated by the correlator 200 during the L symbol period. It is determined whether or not (ST2). At this time, the number of the maximum value may be one or more as required by the rake receiver 500. At this time, it manages by giving priority to several maximum values.

After the peak searcher 60 is finished, the preliminary searcher 60 has the preparator 70 corresponding to M symbol intervals according to the operation of the hardware, which may be zero.

After the preparator 70 ends, the timing estimator 400 starts timing estimation using the received received data (ST3). However, during the peak searcher 60, it is limited to just picking the peak position for the PN code so that the preamble sequence itself may be accurate and the preamble sequence is not synchronized. Also, the peak information for only PN codes may be inaccurate between short peak seekers. Thus, the correlation is continued during the remaining preparer 70 and the timing estimator 80. In other words, the entire preamble period is correlated (ST4).

Then, after the timing estimation is completed, if the peak timing whose maximum allowable correlation value among the correlated values includes the peak timing detected by the peak searcher 60, that is, the peak timing detected by the peak searcher 60 is given. It is determined whether or not the threshold is exceeded (ST5). At this time, if the peak timing detected by the result of the determination step ST5 exceeds the given threshold, the peak detector 300 sends the verified peak signal to the timing estimator 400 and simultaneously transmits timing information of the found preamble sequence. 400 and the rake receiver 500. If the verified peak signal is received by the timing estimator 400, the timing estimator 400 sends the timing information estimated by the timing estimation to the rake receiver 500 until then (ST6). However, otherwise, a new peak timing is sent to the rake receiver 500. That is, when the determination step ST5 does not exceed the threshold value, the maximum value of peaks exceeding another predetermined threshold value among the correlation values obtained in the timing tracking step is selected or returned to the beginning (ST7).

As described above, according to the random access channel synchronization method in the mobile communication system according to the present invention, the timing error component can be reduced because the time estimation is started before the start of the message unit, and the time estimation is performed using the obtained time information. have. Therefore, the reception sensitivity is improved because the spread spectrum signal is received with the correct offset position before demodulating the data transmitted from the terminal.

Claims (3)

Performing a correlation on the input signal with a PN code, and then performing correlation on the preamble sequence during a portion of a given preamble section; A second step of selecting a maximum correlation value among the correlation values obtained in the first step; A third step of performing timing estimation using the maximum correlation value and simultaneously performing the first step for the remainder of the preamble; A fourth step of determining whether there is a correlation value including the maximum correlation value among correlation values exceeding a predetermined threshold value obtained in the third step; And a fifth step of transmitting the timing information estimated in the third step, if it is determined that the result is included in the determination result. The mobile communication system of claim 1, wherein if it is determined that the determination result is not included in the fourth step, the maximum value is selected from the correlation values obtained in the third step or the mobile communication system returns to the first step. Random access channel synchronization method 2. The method of claim 1, wherein the maximum correlation value of the second step comprises a plurality of large values close to the maximum correlation value.