JP2003304217A - Device and method for correcting transmission signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the reliability of data transmission by evading the increase of a transmission signal error ratio caused by a status change of a transmission line. <P>SOLUTION: A received transmission-unit signal is stored in a memory 233 of a correction part 164 and corrected and demodulated and the corrected/ demodulated signal is supplied to a CRC error detection part. The transmission- unit signal from which no error is detected is encoded/modulated and fed back to the correction part 164. The correction part 164 finds out new correction data by comparing the uncorrected transmission unit signal stored in the memory 233 with the fed-back transmission unit signal. The new found correction data are reflected to a known correction data stored in a data storage part 237. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission signal correction apparatus and method applied to a wireless system using a digital modulation method.

[0002]

2. Description of the Related Art Generally, in a wireless communication system using digital modulation such as wireless LAN or wireless access, a signal transmitting side and a receiving side operate independently of each other, but the transmitting frequencies of these transmitting sections are predetermined. If it deviates significantly from the value or if the signal transmission distortion is large, the receiving side cannot accurately demodulate the received signal. Therefore, on the transmitting side, a preamble for use in carrier recovery, timing extraction and propagation distortion correction is added in frame or slot units and the signal is transmitted.

The above-mentioned preamble is a signal determined based on the same definition on the transmitting side and the receiving side, and since the signal pattern is devised, the receiving side should perform signal processing based on this preamble. Due to
Carrier wave reproduction, timing extraction, and propagation distortion correction can be accurately performed.

[0004]

Conventionally, when a received signal is demodulated, the received signal sampling clock, propagation distortion, etc. are corrected by the correction data calculated based on the most recently received preamble, and then demodulated. . However, in the conventional method described above, when the propagation path state changes after receiving the preamble, the sampling timing shift or propagation distortion newly caused by the change in the propagation path state is used as the correction data. Since it cannot be reflected, there is a problem that the transmission signal cannot be corrected accurately and the error rate of the transmission signal increases.

The present invention has been made in view of the above circumstances, and corrects the transmission signal accurately by increasing the update frequency of the correction data to increase the error rate of the transmission signal due to the change in the propagation path state. An object of the present invention is to provide a transmission signal receiving apparatus and method for avoiding it and improving the reliability of data transmission.

[0006]

In order to achieve the above object, according to the present invention, data following a preamble is sent in a transmission unit, and the data in the transmission unit can be correctly demodulated. A transmission signal correction apparatus applied to a wireless communication system to which error detection information for confirming that the received signal is transmitted, the storage unit holding correction data for correcting a received signal, and a received transmission unit. Correction means for correcting the signal of the above-mentioned signal based on the correction data held in the storage means, demodulation means for demodulating the corrected transmission unit signal, and whether or not the demodulated transmission unit signal is erroneous. Error detection means for making a judgment based on the error detection information added to the transmission unit, coding means for coding and modulating a correctly demodulated signal of the transmission unit, and output from the coding means. Correction data calculating means for calculating correction data on the basis of the signal of the transmission unit thus obtained and the signal of the transmission unit before correction, and stored in the storage means on the basis of the correction data calculated by the correction data calculating means. And a correction data updating means for updating the correction data that has been corrected.

According to the present invention, the information of the correction data calculated by comparing the correctly demodulated signal of the transmission unit with the signal of the transmission unit before correction is reflected in the correction data currently held. Therefore, the correction data can be updated more frequently than before. As a result, even if the propagation path state changes after the correction data is once calculated,
The existing correction data can be updated according to the change, and the reliability of correction of the received signal can be improved. The present invention is based on MMAC HiSWANa and ETSI BRAN HI.
It is possible to confirm whether or not the data following the preamble such as PERLAN type2 has a certain transmission unit such as a physical channel, and an error has occurred in demodulation data such as CRC (Cyclic Redundancy Check) for that transmission unit. It can be applied to a wireless communication system to which a code is added.

The invention described in claim 2 is the same as claim 1.
In the transmission signal correction device according to claim 1, at the time of preamble reception, the correction data calculation means calculates correction data based on the received preamble signal and a known preamble signal, and the calculated correction data is stored in the storage means. It is characterized by being retained.

Further, in the invention described in claim 3, the data following the preamble is sent in a transmission unit, and the data of the transmission unit is an error for confirming that the data of the transmission unit can be correctly demodulated. A transmission signal correction method applied to a wireless communication system to which detection information is respectively added, which is a process of holding correction data for correcting a received signal and a correction of holding a signal of a received transmission unit. The process of correcting based on the data, the process of demodulating the corrected transmission unit signal, and determining whether the demodulated transmission unit signal is an error based on the error detection information added to the transmission unit Process, the process of encoding and modulating the correctly demodulated transmission unit signal, and the correction data based on the encoded and modulated transmission unit signal and the uncorrected transmission unit signal. A process of calculating the data, based on the calculated the correction data, to provide a transmission signal correction method comprising the step of updating the correction data held at the present time.

As the radio system to which the transmission signal correction apparatus and the transmission signal correction method of the present invention can be applied, for example, a radio access system using 4.9 GHz to 5.0 GHz or 5.03 GHz to 5.091 GHz in the 5 GHz band, and 5.15 MMAC HiSWANa using GHz to 5.25 GHz, ETSI BRAN HIPER in Europe
An example is a wireless communication system based on the LAN type 2 standard.

[0011]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. In the present embodiment described below, the modulation method is OFDM (Orthogonal Freq).
uency Division Multiplexing)
Using MMACHiSWANa (ARIB STD-
The case where the transmission signal correction device of the present invention is applied to T70) will be described.

FIG. 1 shows an example of the structure of a HiSWANa transmission frame. As shown in the figure, the transmission frame is
Data having a certain transmission unit and CRC, which is error detection information for confirming that the data of the transmission unit can be correctly demodulated, are alternately arranged with the preamble PR at the head. This one frame has data of 2 msec length.

The preamble PR has information necessary for the receiving apparatus to perform reception level adjustment, carrier frequency error detection, OFDM symbol timing detection, propagation distortion detection and the like. In addition, CRC (Cyclic Redunda
The ncy check) is information added to the data of each transmission unit on the transmission side for error detection on the reception side. This CRC regards a data string as a high-order polynomial (called a message polynomial), and regards this as a predetermined generator polynomial G.
It is the remainder obtained as a result of dividing by (x) (Checking Polynomial).

The CRC is a physical channel (data string)
16-bit CRC-16 or 24 depending on the type of
It is divided into CRC-24 having a bit length. CRC-16
Generates transmission data polynomial G (x) = x ¹⁶ + x ¹² + x
^{8 + x 7 + x 6 +} x 3 + x + 1 and the result divided by the modulo operator is obtained residue, whereas, CRC-24
Is a transmission data generation polynomial G (x) = x ²⁴ + x ¹⁰ + x
It is the remainder obtained as a result of dividing by ⁹ + x ⁶ + x ⁴ + x ³ + x + 1 by the modulo operator.

Next, a transmission signal correction apparatus according to an embodiment of the present invention will be described. FIG. 2 is a diagram showing an overall configuration of a transmission signal correction device according to an embodiment of the present invention.
In the figure, reference numeral 161 is an analog-to-digital converter (ADC: Ana) for converting an analog signal into a digital signal.
log-Digital Converter). Reference numeral 162 is a preamble detection unit that detects a preamble from the received transmission signal and performs reception level adjustment, carrier frequency error detection / correction, and OFDM symbol timing detection. Reference numeral 163 is a fast Fourier transform unit (FF) for OFDM demodulation.
T). Reference numeral 164 is a correction unit that detects and corrects the OFDM symbol timing deviation and detects and corrects the propagation distortion. Reference numeral 167 is a decoding unit, which includes a decoder 165 that performs de-interleaving, de-puncturing, Viterbi decoding, and de-scramble, and a CRC error detecting unit 166 that detects an error based on the CRC.

Reference numeral 142 is an encoding unit, which performs CRC on the input transmission unit signal based on a predetermined algorithm.
And a CRC adding unit 143 for adding, and an encoder 144 for performing scrambling, convolutional coding, puncturing, and interleaving. Reference numeral 145 is a mapping unit that performs primary modulation, preamble, and pilot subcarrier generation on a signal in transmission units.

Next, the internal structure of the correction section 164 will be described with reference to FIG. In the figure, reference numeral 231
Is a C field data generator, which generates a normal signal of the known preamble C. Reference numeral 232 indicates the phase comparison unit 23 according to the information input from the input terminal 242.
4 is a switch for switching the signal input to the reference terminal X of No. 4. Reference numeral 233 is a memory that stores a signal of a transmission unit input from the input terminal 243 in a FIFO (First In First
Out) format and outputs the held transmission signal at a predetermined timing to the input terminal Y of the phase comparison unit 234.

The phase comparator 234 detects the OFDM symbol timing deviation and the propagation distortion by comparing the reference signal input from the reference terminal X and the input signal input from the input terminal Y. Reference numeral 235 is a correction data calculation unit that calculates correction data for matching the input signal with the reference signal based on the information acquired from the phase comparison unit 234. Reference numeral 236 is a correction data updating unit,
The correction data calculated by the correction data calculation unit 235 and the correction data held in the correction data holding unit 237 are acquired, and new correction data is generated based on these two correction data. The correction data holding unit 237 holds the latest correction data calculated by the correction data updating unit 236. Reference numeral 238 is a correction calculation unit, which corrects the transmission signal input from the input terminal 243 based on the correction data stored in the correction data holding unit 237 and outputs the corrected transmission signal via the output terminal 244. It outputs to the decoder 165 shown in FIG.

Next, the operation of the transmission signal correction apparatus according to the embodiment of the present invention will be described with reference to FIG. First, when the transmission signal is received by the reception interface 171 (“YES” in step SP202),
This transmission signal is converted into a digital signal by the ADC 161, and is output to the preamble detection unit 162.
The preamble detection unit 162 detects a preamble from the input transmission signal (step SP203). As a result, if the preamble is detected (“YES” in step SP202 in FIG. 4), the detected preamble is subjected to reception level adjustment, OFDM symbol timing detection, carrier frequency error detection / correction, and then the preamble is detected. Output to FFT.

Next, the FFT 163 performs OFDM demodulation on the preamble signal and converts the time domain signal into frequency domain subcarrier I and Q signals (hereinafter, the signal after the conversion is referred to as a subcarrier signal). , And outputs the subcarrier signal to the correction unit 164. In addition, FFT16
From 3, 52 subcarrier signals are obtained. Less than,
Various processes will be described taking one subcarrier signal (α1 in FIG. 5A) as an example.
Naturally, similar processing is performed on the remaining subcarrier signals.

Subsequently, the subcarrier signal α1 is input from the input terminal 243 of the correction section 164 to the input terminal Y of the phase comparison section 234. On the other hand, the reference terminal X of the phase comparator 234 receives the C field data generator 2 as a reference signal.
The known subcarrier signal of the preamble generated by 31 is input. Here, the known subcarrier signal of the preamble is shown as α0 in FIG.

The phase comparison unit 234 detects the OFDM symbol timing deviation and propagation distortion of the subcarrier signal α1 with respect to the subcarrier signal α0 input as the reference signal (steps SP205 and SP206), and the detection result is the correction data calculation unit 235. Output to. The correction data calculation unit 235 calculates correction data (complex I and Q vectors) for correcting the OFDM symbol timing shift and the propagation distortion based on the detection result received from the phase comparison unit 234, and corrects the calculated correction data. The data is output to the data updating unit 236.

The correction data updating unit 236 calculates the latest correction data S based on the following equation (1). S = (k × S0 + (1-k) × S1) (1) In the above formula (1), S is the latest correction data, S0 is the existing correction data read from the correction data holding unit 237, and S1 is the correction data. The correction data is obtained from the calculation unit 236, and k is a weighting value, which is an eigenvalue that is arbitrarily set.

When the correction data updating unit 236 calculates new correction data S by the above equation (1), the correction data updating unit 236 stores this correction data in the correction data holding unit 237 (step S).
P206). As a result, the correction data stored in the correction data holding unit 237 becomes the correction data obtained based on the preamble received this time. When the correction data is obtained based on the preamble, the value of S0 in the above equation (1) is set to “0” and new correction data S
Therefore, the correction data calculated by the correction data calculation unit 235 is actually held in the correction data holding unit 237 as it is. Therefore, here
The correction data α2 shown in FIG. 5 is held in the correction data holding unit 237 as correction data.

Next, the transmission signal DA following the preamble
CRC added to TA1 and DATA1 (see Figure 1)
Is received via the input interface 171 (“YES” in step SP202 of FIG. 4), the transmission signal is similarly supplied to the preamble detection unit 162 via the ADC 161. Preamble detection unit 16
In 2, it is determined that the transmission signal is not the preamble (“NO” in step SP203), the reception level of the signal is adjusted and the carrier frequency error is corrected based on the preamble received earlier, and then the FFT16 is performed.
3 is output.

In the FFT 163, OFDM demodulation is performed, the transmission signal DATA1 is converted from a time domain signal into frequency domain subcarrier I and Q signals, and then output to the correction unit 164. The subcarrier signal here is shown as α3 in FIG. 6B.

When a transmission signal (subcarrier signal α3) that is not a preamble is input to the correction unit 164, this transmission signal is stored in the memory 233 in the correction unit 164 (step SP207) and supplied to the correction calculation unit 238. To be done. The correction calculation unit 238 includes a correction data holding unit 237.
The correction data held in is read, and the amplitude and phase errors of the subcarrier signal α3 due to the OFDM symbol timing deviation and propagation distortion are corrected by this correction data (step SP208). As a result, as shown in FIG. 6B, α4 is obtained as the corrected subcarrier signal.

Then, the corrected subcarrier signal α4
Is output to the decoder 1 via the output terminal 244 of the correction unit 164.
65 (“YE in step SP209”
S "). The decoder 165 decodes the subcarrier signal α4 to obtain binary data as shown in FIG. 5 (c). Then, this binary data is supplied to the CRC error detection unit 166. The CRC error detection unit 166 performs error detection based on the CRC added to the signal of the transmission unit, and if no error is detected (“YES” in step SP210), the signal of the transmission unit is interfaced. In addition to outputting via 172, it outputs to the CRC adding unit 143.

That is, the signal of the transmission unit in which no error is detected is output through the interface 172 and the CRC adding section 143. On the other hand, when the error is detected, the signal of the transmission unit is detected. Is output via the interface 172, but CR
It is not output to the C addition unit 143.

When the CRC adding section 143 receives the signal of the transmission unit in which no error is detected, that is, the demodulated correctly, it adds the CRC to the signal of the transmission unit. For example,
Based on the signal of the transmission unit, either CRC-16 or CRC-24 described above is calculated, and the calculated CRC is added to the signal of the transmission unit. Then, the transmission unit signal to which the CRC is added is encoded by the encoder 144 and output to the mapping unit 145. Mapping unit 1
In 45, the primary modulation is performed to convert the binary data from the time domain signal to the frequency domain subcarrier I and Q signals, and the subcarrier signals are corrected via the input terminal 242 of the correction unit 164. Sent to section 164. The subcarrier signal obtained here is shown in FIG.
Shown as α5 in (d).

The subcarrier signal α5 output from the mapping unit 145 is input to the reference terminal X of the phase comparison unit 234 via the switch 232. On the other hand, the memory 233
From the subcarrier signal α input as the reference signal
5, the subcarrier signal α3 corresponding to the subcarrier signal α3, that is, the subcarrier signal α3 that is a signal of the transmission unit from which the subcarrier signal α5 is generated and is a signal before correction is read out, and the phase comparison unit It is input to the input terminal Y of H.234 (step SP211). The phase comparison unit 234 detects the OFDM symbol timing deviation and the propagation distortion of the subcarrier signal α3 with respect to the subcarrier signal α5 input as the reference signal (steps SP212 and SP21).
3), the detection result is output to the correction data calculation unit 235.

The correction data calculation unit 235 includes a phase comparison unit 2
Based on the detection result received from 34, the correction data for correcting the OFDM symbol timing deviation and the propagation distortion is calculated, and the calculated correction data is used as the correction data updating unit 1.
To 26. The correction data here is shown in FIG.
Shown as 6. The correction data updating unit 236 calculates new correction data in which the correction data α6 input from the correction data calculating unit 235 is reflected in the correction data α2 stored in the correction data holding unit 237. Specifically, the correction data α2 is added to the correction data S0 of the above equation (1),
The new correction data S is calculated by substituting the correction data α6 received this time from the correction data calculator 235 into the correction data S1. As a result, the correction data α7 as shown in FIG. 5 (e) is calculated.

Then, the calculated new correction data α7 is stored in the correction data holding unit 237 (step SP21).
4). As a result, the correction data α2 stored in the correction data holding unit 237 is the correction data α7 in which the correction data α6 obtained from the subcarrier signals α3 and α5 is reflected.
Will be updated. Then, similarly to the above, for the signal of the transmission unit that is subsequently received, the processing of steps SP202 to 214 is repeated for each signal of the transmission unit.

As described above, according to the transmission signal correction apparatus according to the present embodiment, the received signal of the transmission unit is held in the memory 233 of the correction unit 164, corrected and demodulated, and the CRC error detection unit 166. Is supplied to. Then, the signal of the transmission unit in which no error is detected is encoded and modulated, and is fed back to the correction unit 164. Then, in the correction unit 164, the memory 233
New correction data is obtained by comparing the signal of the transmission unit before correction held in the above-mentioned and the signal of the fed-back transmission unit. Then, the newly obtained correction data is reflected in the existing correction data currently held in the correction data holding unit 237. As a result, the correction data held in the correction data holding unit 237 is updated frequently, and even if the propagation path state changes during the reception of the data of the transmission unit following the preamble. It is possible to reflect the propagation distortion, the clock timing deviation, and the like due to the change in the correction data, so that the reliability of data transmission can be improved and the transmission error rate can be remarkably reduced.

It should be noted that, in the receiving apparatus according to the present embodiment shown in FIG. 3, each section related to the correction processing shown in FIG. 3 (a phase comparing section, a correction data calculating section, a correction data updating section, a correction data holding section, A program for realizing the functions of the correction calculation unit, etc.) is recorded in a computer-readable recording medium, and the program recorded in this recording medium is read into a computer system and executed to execute various processes. May be. The “computer system” mentioned here includes an OS and hardware such as peripheral devices.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific structure is not limited to this embodiment, and includes a design etc. within the scope not departing from the gist of the present invention. Be done.

For example, the coding unit 142 and the mapping unit 145 shown in FIG. 2 are the functions that a transmitting device normally has. Generally, a communication device has both a transmission / reception function, and thus the encoding unit 142 and the mapping unit 145 are used.
May be diverted from that of the transmitter. Also,
Each unit shown in FIG. 2 corresponds to a component forming a baseband signal processing unit in a so-called communication device.

[0038]

As described above, according to the transmission signal correction apparatus and the correction method of the present invention, the correction data is calculated for each correctly demodulated transmission unit, and this correction data is reflected in the existing correction data. Therefore, the correction data can be updated frequently. As a result, it is possible to reduce the correction error particularly in the latter half of the frame, prevent an increase in the error rate of the transmission signal due to a change in the propagation path state, and improve the reliability of data transmission.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a transmission frame according to an embodiment of the present invention.

FIG. 2 is a diagram showing an overall configuration of a transmission signal correction device according to an embodiment of the present invention.

FIG. 3 is a block diagram showing an internal configuration of a correction unit in FIG.

FIG. 4 is a flowchart showing processing contents of the transmission signal correction device according to the embodiment of the present invention.

FIG. 5 is a diagram for specifically showing processing contents of data of the transmission signal correction apparatus according to the embodiment of the present invention.

[Explanation of symbols]

161 ... ADC, 162 ... Preamble detection unit, 163
FFT, 164 correction unit, 165 decoder (demodulation unit), 166 CRC error detection unit (error detection unit),
167 ... Decoding section, 142 ... Encoding section (encoding means), 1
43 ... CRC addition section, 144 ... Encoder, 145 ... Mapping section, 231 ... C field data generation section, 23
2 ... Switch, 233 ... Memory, 234 ... Phase comparison section (correction data calculation means), 235 ... Correction data calculation section (correction data calculation means), 236 ... Correction data update section (correction data update means), 237 ... Correction data Holding unit (storage unit) 238 ... Correction calculation unit (correction unit)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyasu Ishikawa             2-15-1 Ohara, Kamifukuoka City, Saitama Stock             Company CAD Research Institute (72) Inventor Hideyuki Shinonaga             2-15-1 Ohara, Kamifukuoka City, Saitama Stock             Company CAD Research Institute F-term (reference) 5K014 AA01 BA06 EA07                 5K022 DD01 DD13 DD18 DD19 DD33                       DD34

Claims (3)

[Claims] 1. A radio in which data following a preamble is sent in a transmission unit, and error detection information for confirming that the data in the transmission unit has been correctly demodulated is added to the data in the transmission unit. A transmission signal correction apparatus applied to a communication system, comprising storage means for holding correction data for correcting a received signal, and a received transmission unit signal based on the correction data held in the storage means. Correction means for correcting, demodulation means for demodulating the corrected transmission unit signal, and error for judging whether or not the demodulated transmission unit signal is an error based on error detection information added to the transmission unit A detection unit, an encoding unit that encodes and modulates a correctly demodulated signal of the transmission unit, a signal of the transmission unit output from the encoding unit, and a signal of the transmission unit before correction. Correction data calculating means for calculating correction data based on the correction data, and correction data updating means for updating the correction data held in the storage means based on the correction data calculated by the correction data calculating means. Transmission signal correction device. 2. Upon reception of a preamble, the correction data calculation means calculates correction data based on the received preamble signal and a known preamble signal, and the calculated correction data is held in the storage means. The transmission signal correction device according to claim 1, wherein 3. A radio in which data following a preamble is sent in a transmission unit, and error detection information for confirming that the data in the transmission unit has been correctly demodulated is added to the data in the transmission unit. A transmission signal correction method applied to a communication system, comprising a step of holding correction data for correcting a received signal, and a step of correcting a received signal of a transmission unit based on the held correction data, The process of demodulating the corrected transmission unit signal, the process of determining whether the demodulated transmission unit signal is an error based on the error detection information added to the transmission unit, and the correctly demodulated transmission unit A step of encoding and modulating the signal of, and a step of calculating correction data based on the encoded and modulated signal of the transmission unit and the signal of the transmission unit before correction, It has been based on the correction data, the transmission signal correction method comprising the step of updating the correction data held at the present time.