KR20010091162A - Method and apparatus for finding Walsh index of communication system receiver - Google Patents

Abstract

PURPOSE: An apparatus and method for searching a Walsh index in a receiver of a communication system is provided to improve the performance of a demodulator by quickly searching the Walsh index of a signal received from the receiver. CONSTITUTION: A receiver receives a Walsh function in which a length is M and an index is m(S1). The receiver judges whether the Mth/2 bit of the received Walsh function is identical to a 0th bit(S2). If the Mth/2 bit of the received Walsh function is identical to the 0th bit, the Walsh function has a lower index(S3). If the Mth/2 bit of the received Walsh function is not identical to the 0th bit, the Walsh function has an upper index(S4). If the received Walsh function has the lower index, it is judged whether the Mth/4, the Mth/8,..., the second, and the first bit are identical to the 0th bit(S5). If the Mth/4, the Mth/8,..., the second, and the first bit are identical to the 0th bit, an index of the received Walsh function is searched(S7).

Description

Method and apparatus for finding Walsh index of communication system receiver

The present invention relates to a communication system receiver, and more particularly, to an apparatus and method for finding Walsh indexes in a receiver of a communication system.

In general, in a communication system, a reverse CDMA channel is composed of an access channel and a traffic channel. The access channel can correspond to a maximum of 32 access channels per paging channel, and the reverse CDMA channel has no limitation in channel capacity by design. The total number of channels that can be used is determined by the interference noise between mobile stations.

In this case, the access channel has a fixed information rate of 4800bps while the traffic channel has a variable information rate of 1200, 2400, 4800, 9600bps depending on the amount of voice and data.

In the channel coding of the reverse link, a convolutional encoder with a code rate of 1/3 and a constraint length of 9 and a block interleaver are used. The Walsh function is used for orthogonal modulation in the forward link to demodulate at the base station. Use as a way to improve.

Here is the Walsh function:

In a communication system in which the M-ary Walsh code modulation scheme is used, the signal information is aggregated into groups of N symbols (= M here), each of which is mapped onto one of the finite numbers (M) of Walsh functions. For example, when a 64-phase modulation scheme is used (M = 64), signal information is aggregated into groups of six symbols each.

Here, each Walsh function is represented by 64 Walsh 'chips', where each Walsh chip is '0' and '1'. Here it is used to select one Walsh function corresponding to each group of six symbols, which are transmitted on behalf of the data symbols. Each transmitted Walsh function (or code) is represented by a Wn index where n is 0 to 63.

Thus, to decode the received modulated signal, the FHT compares the received signal modulated with a particular Walsh function with each Walsh function in a predetermined set of Walsh functions to determine which function has been received.

Hereinafter, a Walsh index search method in a receiver of a communication system according to the prior art will be described in detail.

Conventionally, in the standards of IS-95 and IS-2000, orthogonal modulation is used for a part of access channel and traffic channel of reverse link.

It modulates six symbols into a 64-phase orthogonal sequence, and the receiver demodulates the signal by finding the Walsh index of the received signal.

The FHT has been conventionally used to find the Walsh index of the received signal.

That is, the FHT method obtains the energy for all sequences of the received signal and then takes the index of the sequence with the largest energy, and requires a mathematical operation to obtain the energy. It takes a lot of time to operate on very long sequences because of the overhead of finding energy to get an index.

As a result, when the sequence index of the received signal is not known, in order to know the index of the sequence, it is necessary to wait a long time until the index result of the received M-phase sequence is output by using the FHT for the long M-phase sequence, and the lookup table ( The problem arises that a look-up table must be compared for up to M sequences bit-by-bit for M-bits.

Accordingly, an object of the present invention is to solve the above problems, and to provide an apparatus and method for finding a Walsh index in a receiver of a communication system for improving the performance of a demodulator by quickly finding a Walsh index of a signal received at a receiver of a communication system. Its purpose is to.

In the receiver of the communication system according to the present invention for achieving the above object, the Walsh index finder in the communication system receiver, receives the Walsh chip rate clock signal to count the number of bits of the Walsh sequence value of the input signal A decoder which generates a clock signal by decoding the bits of the Walsh sequence output to the counter, and a Walsh sequence which receives the clock signal output from the decoder and outputs Walsh bits according to a signal applied from a Walsh function. It includes a plurality of flip-flops for generating the index of.

The Walsh index finding method in the receiver of the communication system according to the present invention configured as described above includes a Walsh function having a length M and an index m in the communication system receiver, and the M / 2th bit of the received Walsh function is '0'. Determining whether the second bit is the same, and if the M / 2th bit is the same as the '0' bit, the received Walsh function has a lower index, and M / 4, M / 8,. ... determining whether the '2', '1' th bit is the same as the '0' th bit to obtain the index of the received Walsh function. Finding can improve the performance of the demodulator.

1 is a block diagram illustrating a configuration of a Walsh index finder in a receiver of a communication system according to the present invention.

2 is a flowchart illustrating a Walsh index finding method in a communication system receiver according to the present invention.

Explanation of symbols for main parts of the drawings

1: Counter 2: Decoder

3a to 3n: flip flop

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Referring to the accompanying drawings, a preferred embodiment of the Walsh index finding apparatus and method in the receiver of the communication system according to the present invention will be described.

1 is a block diagram illustrating a configuration of a Walsh index search apparatus in a receiver of a communication system according to the present invention, and FIG. 2 is a flowchart illustrating a Walsh index search method in a receiver of a communication system according to the present invention.

As shown in FIG. 1, first, the counter unit 1 receives a Walsh chip rate clock signal and counts the number of bits of the Walsh sequence value of the input signal.

The decoder 2 then decodes the bits of the Walsh sequence output to the counter unit 1 and applies them as clock signals to the plurality of flip-flops 3a to 3n so that the plurality of flip-flops 3a to 3n recognize them. do.

The plurality of flip-flops 3a to 3n receive the clock signal of the decoder 2 and output Walsh bits according to a signal applied from a Walsh function so that the indexes of the received Walsh sequence are the highest bit (MSB) and the lowest. Generated by bit (LSB) and output.

As described above, the Walsh index search method in the receiver of the communication system according to the present invention will be described below.

As shown in FIG. 2, a method for obtaining an index of a Walsh function that is sequentially input will be described in detail. Denoted by the mth column of the M * M Hadamard matrix. At this time, the Hadamard matrix is created in the following way.

= 0, = , , ..., =

Where M is 2 ^ k (k = 0,1,2,3, ...), silver Binary complement of.

First, the receiver of the communication system receives a Walsh function of length M and index m (S1).

Then, it is determined whether the 'M / 2' th bit of the received Walsh function is the same as the '0' th bit (S2).

As a result of the determination (S2), if the 'M / 2' th bit of the received Walsh function is the same as the '0' th bit, the Walsh function has a lower index (S3).

On the other hand, if the determination result S2 is not the same bit, the Walsh function has a higher index (S4).

The lower index is an index of 0 to M / 2, and the upper index is an index of M / 2 to M / 2-1.

Subsequently, if the received Walsh function has a lower index, the 'M / 4', 'M / 8', ..., '2', and '1' bits of the Walsh function are again the same as the above method. It is determined whether they are the same by comparing with the '0' th bit (S5).

As a result of the determination (S5), if each bit is equal to the '0'-th bit, the index of the received Walsh function is found (S7).

Meanwhile, as a result of the determination, if each bit is not the same as the '0' th bit, the received Walsh function has a corresponding upper index (S6).

Here, the 'M / 2' bit is referred to as the most significant bit MSB, and the '1' bit is referred to as the least significant bit LSB. Extracting the bits is the index of the Walsh function received.

Also, for the Walsh function of all indexes, the '0' th bit is always zero. If the '0' bit is not 0, it can be seen that the Walsh function is coming in by exclusive OR (XOR) to the data value '1'. In this case, apply the above method after inverting all the bits. To find the index of a sequence.

As described above, an apparatus and method for finding Walsh indexes in a receiver of a communication system according to the present invention have the following effects.

It is possible to improve the performance of the demodulator by finding the index of the received sequence within M / 2 + 1 clock as a Walsh chip rate clock signal without a mathematical operation on the received M phase Walsh function. .

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (5)

In the receiver of the communication system, A counter unit for receiving a Walsh chip rate clock signal and counting which bit the Walsh sequence value of the input signal is; A decoder for decoding a bit of the Walsh sequence output to the counter to generate a clock signal; And a plurality of flip-flops for generating an index of the received Walsh sequence by receiving a clock signal output from the decoder and outputting a Walsh bit according to a signal applied from a Walsh function. Walsh index finder device in receiver. The method of claim 1, And a Walsh index finder in a receiver of a communication system, characterized in that if a signal applied from the Walsh function is sequentially received, an index of the Walsh sequence received within an M / 2 + 1 clock may be found. A communication system receiver, Receiving a Walsh function of length M and index m, and determining whether the 'M / 2' th bit of the received Walsh function is equal to the '0' th bit; If the 'M / 2' th bit is the same as the '0' th bit, the received Walsh function has a lower index, and the 'M / 4', 'M / 8', .... '2 of the corresponding Walsh function. And determining the index of the received Walsh function by determining whether the '1' th bit is the same as the '0' th bit. The method of claim 3, wherein And if the 'M / 2' th bit of the received Walsh function is not equal to the '0' th bit, then the index of the received Walsh function further comprises having a higher index. How to find Walsh index. The method of claim 3, wherein And the 'M / 2' th bit is the most significant bit (MSB), and the '1' th bit is the least significant bit (LSB).