KR100442427B1 - CDMA demodulation system and method of finger signal management - Google Patents

Abstract

The present invention relates to demodulation of CDMA, the CDMA demodulator system according to the present invention, an analog receiver for receiving a signal from a plurality of users to generate a baseband digital signal, an input for storing the output signal from the analog receiver A demodulator for receiving a signal stored in a sample buffer and the input sample buffer, and sequentially demodulating finger signals according to a time difference of each user's received signal by using a time multiplexing method; and sequentially demodulating in one demodulator And a demodulation engine comprising one combiner for accumulating and combining the received finger signals for each user.

According to the present invention, as many demodulators as the number of users are required to demodulate a plurality of existing signals of a user, and a large amount of deskew buffers are compensated for time difference compensation of each finger signal by processing finger signals in parallel. By using a demodulation engine that can store a large number of user's signals with an input sample buffer and process them at high speed, a demodulator can process demodulation of a large number of existing users. By processing the finger signals in series, an effect that can process the finger signals of multiple users with only a small buffer size is expected.

Description

CDM demodulation system and method of finger signal management

The present invention relates to a CDMA demodulator system, and more particularly, to a CDMA demodulator system and a finger signal processing method for demodulating a CDMA baseband signal of multiple users.

Code division multiple access (CDMA) scheme allows multiple users to share a frequency and time while assigning a random sequence to each user so that each user spreads and transmits the transmitted signal. It is a multi-communication method of the current mobile communication system that generates and synchronizes a random sequence as used on the transmitting side, despreads the received signal, and recovers the signal. In the present mobile communication system, TIA using spread spectrum technology is used. IS-95C CDMA system is used.

The IS-95C system is a direct sequence CDMA method using a Pseudo Noise (PN) chip of 1.2288 MHz. The base station, which is the receiver of the reflective link, removes the carrier frequency from the received RF signal and digitalizes it using an analog-to-digital converter. Therefore, the received signal is transmitted through the CDMA baseband channel configuration, the received baseband signal is despread by the short-PN, and then despreaded by the long-code.

1 and 2 illustrate a conventional demodulation method, and FIG. 1 is a block diagram showing a configuration for processing a finger signal of a conventional CDMA demodulator system, and FIG. 2 is a block diagram illustrating a demodulator of FIG. It is also.

Referring to FIG. 1, a base station, which is a reception unit of a reflection link, includes a demodulator 200-1 to 200-n for demodulating signals from an analog receiver 100 and a plurality of users received from the analog receiver 100, respectively. It is configured to include).

In addition, the demodulators 200-1 to 200-n are demodulators A, called fingers, which demodulate signals of various paths (that is, signals received directly and signals reflected and received) received from the same user. It comprises four, and comprises a combiner 207 for combining the demodulated finger signal from each demodulator.

On the other hand, the demodulator (A) has the configuration as shown in Figure 2, referring to Figure 2, in order to despread in a quadrature phase shift keying (QPSK) method, in-phase and size information (quadrature) ), The despreader 202 for despreading the signal received from the switch matrix 201, the despreader 202, and the despreader 202 are despreaded. Receiving a signal from the despreader 202 and the receiver 209 and time tracking 210 for calculating the time difference between the PN code generator 208 and the PN code generator 208 for generating and inputting the PN code. Store the converted signal through the pilot filter 203, the accumulator 204, the phase shifter 205, and the phase shifter 205 until another phase-delayed finger signal is converted. Deskew buffer 206 and channel flat The go 211 and the lock detector 212 is configured.

The operation of the conventional CDMA demodulation system configured as described above is as follows.

1 and 2, signals received through the analog receiver 100 are input to different demodulators 200-1 to 200-n according to users of the signals.

The signals input as described above have time differences with each other even if they are signals received from the same user according to the input path. By compensating these time differences and adding the demodulated signals, a signal closer to the original transmitted signal can be made. Current systems use a system that demodulates and combines signals from up to four different paths. Also, a demodulator A for demodulating a signal transmitted from the same user having this time difference is called a finger, and a signal demodulated from each finger is a finger signal.

On the other hand, since each finger signal is connected in parallel and combined in a combiner, in order to overcome the time difference between each other, four finger signals must be waited until they are completely output. After temporarily storing all four finger signals, the combiner 207 adds them together.

For example, if the time difference from the original signal of the directly transmitted signal is delayed by 4PN chips and the reflected signal is delayed by 8PN chips, the two signals must be compensated by the time of the 4PN chips. Can be. To this end, it is stored in each of the deskew buffer 206, and is coupled through the combiner 207 at a predetermined point in time when all the finger signals are processed to be decoded by the deinterleaver. In this case, the 'constant time' is defined as a worry delay profile between the first received signal and the latest received signal.

In other words, assuming that the difference between the fastest incoming signal and the latest incoming signal is 40PN chip time, and there are 128 fingers in total, one symbol consists of two PN chip samples. Since we need a deskew buffer that can store = 20 symbols, and we need 128 such deskewers, it's like having to store all 128 × 20 symbols.

In order to process the finger signal by despreading in the above manner, each demodulator A must have a deskew buffer, and different demodulators 200-1 to 200-n are required for each user. .

As described above, in order to process signals of a plurality of users, there is a disadvantage that a plurality of demodulation circuits for processing the same signal must be provided.

In order to solve the above problems, the present invention temporarily stores a transmitted signal, and has a demodulation engine having a processing speed much faster than that of a conventional demodulator, so that multiple demodulations of the same signal can be continued with one demodulator. A CDMA demodulator system and many that have a high-speed engine to reduce the number of circuits required by the system, and to reduce the deskew buffer by providing a serial processing method rather than parallel processing for finger signal processing. It is an object of the present invention to provide a method for treating a finger.

1 is a block diagram showing a configuration for finger signal processing of a conventional CDMA demodulator system.

2 is a block diagram showing the configuration of the demodulator of FIG.

3 is a block diagram illustrating a configuration of a CDMA demodulator system according to an embodiment of the present invention.

4 is a block diagram showing the configuration of a demodulation engine in FIG.

5 is a flowchart illustrating an operation procedure of a finger signal processing method of a CDMA demodulator system according to an exemplary embodiment of the present invention.

6 is a diagram illustrating the contents of a combiner buffer by finger signal processing in a CDMA demodulator system according to an embodiment of the present invention.

<Brief description of the detailed parts of the drawings>

100: analog receiver 200-1 ,,, 200-n: demodulator

300: input sample buffer 400: demodulation engine

201, 401: switch matrix 202, 402: despreader

203, 403: pilot filter 204, 404: accumulator

205, 405: phase shifter 206: deskew buffer

207, 406: combiner 208, 407: PN code generator

209, 408: receiver 210, 409: time tracking

211, 410: Channel Evaluator 212, 411: Lock Detector

412 combiner buffer

According to an aspect of the present invention, there is provided a CDMA demodulator system, comprising: an analog receiver configured to receive signals from a plurality of users and generate a baseband digital signal; an input sample buffer to store an output signal from the analog receiver;

A demodulator that sequentially receives the signals stored in the input sample buffer and sequentially demodulates the finger signals according to the time difference of the respective user-received signals using a time multiplexing scheme; and a finger signal sequentially demodulated by the one demodulator. It characterized in that it comprises a demodulation engine consisting of one combiner to accumulate them by user.

Preferably, in order to process a signal by time-multiplexing, the input sample buffer is referred to as an 'N PN-chip' as a time delay interval between the fastest received signal and the latest received signal, and per unit time in one finger. When processing the M PN-chip, it is possible to store as much as N + M PN-chip.

Preferably, the demodulation engine is configured to include a combiner buffer for storing the size of data that can be processed per unit time in one finger, for the combination of the serially processed finger signal.

In addition, the finger signal processing method of the CDMA demodulator system according to the present invention,

In the standby state, receiving a user's request for use and searching for the presence of a first finger signal;

Despreading the retrieved finger signal with an M PN-code and storing it in a combiner buffer, and retrieving the presence or absence of a second finger signal of the user;

Despreading the retrieved second finger signal with an M PN-code, accumulating the first finger signal stored in the combiner buffer, and storing the second finger signal again in a combiner;

Searching for the last finger signal of the user, despreading with an M PN-code, combining the accumulated value between the upper finger signals of the combiner, transmitting the decoded step, and searching for a finger signal of the next user; The despreading is performed using a time multiplexing scheme.

The CDMA demodulator system and finger signal processing method according to the present invention configured as described above will be described with reference to the accompanying drawings.

3 is a block diagram showing a configuration of a CDMA demodulator system according to an embodiment of the present invention, Figure 4 is a block diagram showing a configuration of a demodulation engine in Figure 3, Figure 5 is a CDMA demodulator according to an embodiment of the present invention FIG. 6 is a flowchart illustrating an operation procedure of a method for processing a finger signal of a system, and FIG. 6 is a diagram illustrating contents of a combiner buffer by finger signal processing of a CDMA demodulator system according to an exemplary embodiment of the present invention.

Referring to FIG. 3, a CDMA demodulator system according to an embodiment of the present invention includes an analog receiver 100 for receiving signals from a plurality of users, and an input sample buffer 300 for storing signals received from the analog receiver 100. And a demodulation engine 400 for demodulating the signal stored in the input sample buffer 300 at high speed. The demodulation engine 400 further includes a signal stored in the input sample buffer 300. And a combiner 406 for coupling a demodulated finger signal from the demodulator (B).

Referring to FIG. 4, the demodulator B inversely despreads phase information of an input signal, a switch matrix 401 for controlling quadrature information, and a signal input through the switch matrix 401. A spreader 402, a PN code generator 407 for providing a PN code for the operation of the despreader 401, a combiner 406 for combining finger signals, and a receiver 408 for time delay information. And a time tracking 409, a lock detector 411, a pilot filter 403 for obtaining a signal phase of the despread signal, an accumulator 404, and a channel estimator 410 for symbol generation. It is configured to include.

In addition, the combiner 406 includes a combiner buffer 412 for compensating and combining the time difference of a finger signal. As described above, in the CDMA demodulator system according to the present invention, each finger signal has four discs. Unlike conventional parallel processing schemes, which are stored in the queue buffer 206 and coupled to the combiner 207, the finger signals are sequentially cumulatively combined in one combiner 406 using the input sample buffer 300 to serialize the signals. In addition, unlike the conventional method in which a different demodulator is required for each user, a signal processing circuit of a user who has multiple user signals through a single input sample buffer 300 and a demodulation engine 400 is performed. It can be configured to be large enough to be processed.

In the CDMA demodulator system according to the present invention configured as described above, referring to FIGS. 3 and 4, the CDMA signal received through the analog receiver 100 is a signal used by a plurality of users, and the signal is input sample buffer. And the demodulation engine 400 demodulates the data.

At this time, the amount of the signal to be stored in the input sample buffer 300, 'N' PN-chip, which is the delay difference between the finger signal received the earliest, and the finger signal received the latest received ' The size is equal to the 'N + M' PN-chip combined with the M 'PN-chip.

That is, if the delay difference of the last received finger signal is 40 PN-chip, and if one finger processes 16 PN-chips per unit time, the input sample buffer 300 may store 40 + 16 = 56 PN-chips. Space is needed.

As described above, the sample data stored in the input sample buffer 300 is referred to as C1 to C56. The first finger signal 1 has a time delay of 4 PN chips, and the next finger signal 2 is 8 PN chips. If there is a delay, the finger signals 1 are C4 to C19, and the finger signals 2 are C8 to C23.

Such a finger signal is sequentially received by the demodulation engine of FIG. 4 and then despread by the despreader 402 along with the PN code provided from the PN code generator 407 via the switch matrix 401. At this time, the PN code is generated by synchronizing the signal received through the receiver 408 with the time tracking 409 and distinguishing the first and last signals of the finger signal.

The despread signal passes through a pilot filter 403 to obtain a phase of the signal, and when a phase is converted by a phase shifter and demodulation is completed, the combiner buffer 406 in the combiner buffer 412 receives a respective finger signal. Each time a received signal is accumulated and stored, all finger signals are received, accumulated and combined, and one demodulated signal is output. That is, each finger signal is serialized and combined in the combiner buffer 412. In this case, in order to combine the finger signals in the combiner 406, the time tracking 409 and the lock detector 411 check the time when the last signal is received with the time difference information of the finger signals, respectively, Check that it is done and print it out.

The above-described finger signal processing will be described in more detail with reference to FIG. 6. As shown in the symbol diagram in which a symbol of user A is input to the combiner of FIG. 6, the finger signal of user A is finger 0 (S0 to S15). Assuming that there are four signals from S0 '' 'to S15' '', the combiner buffer contents are first stored in the demodulated signal of the finger 0 (S0 to S15) and (a). When the finger 1 symbol to be demodulated is accumulated and stored (S0 + S0 'to S15 + S15') and (b), the cumulative finger is accumulated and demodulated to the last finger 3 symbol (sum S0 to sum S15) through an interleaver to decode. Will be sent to the decoder. In other words, the content of the combiner buffer is changed to a-b-c-d.

The size of the combiner buffer 412 is only the size of a symbol that can be processed per unit time in one finger, unlike the deskew buffer, which is required as the size of a finger signal that can be processed per one finger signal.

The reason is that the method of processing the finger signal is a serial processing method by time-multiplexing. Referring to FIG. 5, it is detected whether a user is present in the standby state (S501) (S502), and the retrieved user's finger. The signal is searched for (S503).

If the finger signal is found as a result of the search, processing is performed by despreading with 16 PN codes (504), and after increasing the number of the finger (S505), searching whether there is another finger signal of the same user (S506). If a finger signal from the same user is found, the process is repeated from step S504. If there is no finger signal from the same user, the number of the user is increased (S507) to search for another user (S502).

Through the above operation, a finger signal received irregularly is searched, and a finger signal from the same user is sequentially arranged to have an effect of being serially input.

That is, in the case of the finger signal described above as an example, the C4 to C19 of the finger signal 1 is processed and stored in the combiner buffer 412, and then the signals of C8 to C23 of the next finger signal 2 are processed. The data is accumulated and stored again in the combiner buffer 412.

That is, if the processed signal of the finger signal 1 is S1 to S16, the processed signals S17 to S32 of the finger signal 2 are combined with the previously stored S1 to S16, and the values of S1 + S17, ~, S16 + S32 are combined in the combiner buffer ( 412).

As described above, since the next finger signal is accumulated and stored, the size of the combiner buffer 412 is sufficient if the size of the data that one finger can process per unit time is equal to the size of the data.

As described above, the CDMA demodulator system and the finger signal processing method according to the present invention require as many demodulators as the number of users to demodulate a plurality of existing user signals, and process the finger signals in parallel to each finger. In order to compensate for the time difference of a signal, a large amount of deskew buffer is required by storing a plurality of user signals with an input sample buffer and using a demodulation engine capable of processing at high speed. Conventionally, demodulation of a large number of users can be performed, and since the finger signal processing is serialized, only one buffer is required per unit time, and thus, the finger signal can be processed with only a few buffers.

Claims (6)

An analog receiver for receiving signals from a plurality of users and generating baseband digital signals; An input sample buffer for storing an output signal from the analog receiver; A demodulator that sequentially receives the signals stored in the input sample buffer and sequentially demodulates the finger signals according to the time difference of the respective user-received signals using a time multiplexing scheme; and a finger signal sequentially demodulated by the one demodulator. CDMA demodulator system comprising a demodulation engine consisting of a combiner for accumulating and combining them for each user. The method of claim 1, In order to process the signal by time-multiplexing, the input sample buffer is referred to as 'N PN-chip' as the time delay interval between the fastest received signal and the latest received signal, and M PN− per unit time in one finger. CDMA demodulator system, characterized in that it can store as much as N + M PN-chip when processing a chip. The method of claim 1, The one combiner comprises a combiner buffer for storing the size of data that can be processed per unit time in one finger for combining the serially processed finger signal, CDMA demodulator system Sequentially searching whether a finger signal exists for each user with respect to the received signal according to a plurality of user request signals; Despreading the finger signals for each user if there is a finger signal as a result of the search, and then combining and decoding the despreaded finger signals to accumulate for each user, the finger of the CDMA demodulator system comprising: Signal processing method. The method of claim 4, wherein Storing the signal received from the receiver in an input sample buffer for time multiplexing; And outputting to a demodulator to sequentially demodulate the signals stored in the input sample buffer. The method of claim 4, wherein The despreading is a finger signal processing method of a CDMA demodulator system, characterized in that performed using a time multiplexing scheme.