JP2003101601A - Modulation scheme selection apparatus and modulation scheme selection method, base station apparatus and mobile station apparatus including modulation scheme selection apparatus, wireless communication system, and modulation scheme selection program - Google Patents

Abstract

(57) [Problem] To provide a modulation method selection device and a modulation method selection method capable of accurately determining a quality state of a transmission path and thereby selecting an optimum modulation method. SOLUTION: An error correction unit 101 for correcting an error of convolutionally encoded received data, an error in the error corrected data is determined for each frame, and if no error is included, an H pulse is output. A CRC detector 103 that outputs L pulses as a CRC detection result, a convolution encoder 105 that convolutionally encodes error correction data, and a comparison between the convolutional code data and the received data. A data comparing unit 107 for outputting an error pulse, a counter unit 109 for counting the error pulses and outputting an error pulse count value, and integrating the error pulse count value into the count value according to the CRC detection result, for each predetermined frame And a modulation scheme selection section 111 for selecting a modulation scheme according to the magnitude of the count value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modulation method selection device, a modulation method selection method, and a modulation method selection method which select an optimum modulation method from a plurality of modulation methods according to the quality condition of a transmission line and switch to it. The present invention relates to a base station apparatus and a mobile station apparatus each provided with an apparatus, a wireless communication system, and a modulation scheme selection program.

[0002]

2. Description of the Related Art In a conventional wireless communication system compatible with a plurality of modulation systems, a quality condition of a transmission line (hereinafter, simply referred to as transmission quality) is constantly monitored, and if the transmission quality is good, a high rate transmission modulation system. (For example, 16QAM),
When the transmission quality deteriorates, a low rate transmission modulation method (for example, BPSK) is used. By doing so, it has been possible to maintain QoS (Quality of Service) and allow more users to communicate in a limited band. 16Q
AM is less susceptible to deterioration due to multipath compared to BPSK, but has a feature that it can transmit more data at one time, and BPSK is more resistant to deterioration due to multipath than 16QAM but can be transmitted at one time. It is characterized by a small amount.

In mobile terminals, base stations, etc. used in such conventional radio communication systems, received data is compared with data after error correction, and if there is an error in the received data, the error (bit error) is detected. There is provided a circuit that monitors the deterioration of the transmission quality by creating an error pulse signal indicating that the pulse number of the error pulse signal is determined based on a predetermined threshold value. The "bit error rate monitoring circuit" described in Japanese Patent Laid-Open No. 5-160795 corresponds to the above circuit, and a circuit for reducing the circuit scale has been proposed.

As shown in FIG. 5, the circuit described in the publication has a holding means 11 for holding an alarm signal in each cycle,
The selection means 13 for selecting any one of a plurality of threshold values according to the stored alarm signal, and the number of bit errors are counted for each cycle, and the count value and the selected threshold value are selected. A bit error number accumulating unit 15 that outputs an alarm signal according to the magnitude relationship is provided, and the degree of deterioration or restoration of the bit error rate is determined every predetermined period according to the error pulse signal indicating the bit error of the received data. The alarm signal indicating is output.

[0005]

However, in the above-mentioned conventional bit error rate monitoring circuit, since the error pulse is simply counted for every certain period, the transmission quality is largely deteriorated and the error correction is performed. When an error exceeding the capability occurs, the error pulse itself causes an error, so that the transmission quality cannot be accurately evaluated.

The present invention has been made in view of the above-mentioned problems of the prior art, and is a modulation system selection device capable of accurately obtaining the quality condition of a transmission path and thus selecting an optimum modulation system. And a modulation method selection method, a base station apparatus and a mobile station apparatus provided with a modulation method selection device, a wireless communication system, and a modulation method selection program.

[0007]

In order to solve the above problems, a modulation method selection device according to the present invention is a modulation method that supports a plurality of modulation methods and selects a modulation method according to the quality condition of a transmission line. A selection device, which counts error pulses indicating a bit error in received data and outputs an error pulse count value for each frame, and for each frame whether the received data contains a bit error. Judgment, an error detection unit that outputs a pulse of a different level depending on the presence or absence of a bit error, and a count value that is an integrated value of error pulse count values according to the level of the pulse output from the error detection unit. The error pulse count value or a predetermined value output from the counting unit is integrated,
A modulation scheme selection unit that selects a predetermined modulation scheme for each predetermined frame from the plurality of modulation schemes based on the count value.

Further, the modulation system selection device according to the present invention is
An error correction unit that corrects an error in the received data, a data comparison unit that compares the error-corrected data in the error correction unit with the received data, and generates the error pulse whenever there is a mismatched bit, It is equipped with.

Therefore, even when an error occurs that exceeds the error correction capability of the error correction unit due to a large deterioration of the transmission quality, the quality state of the transmission path can be accurately obtained. As a result, the optimum modulation method can be selected.

Further, the modulation system selection device according to the present invention is
When the received data is convolutionally encoded data,
A convolutional encoding unit for convolutionally encoding the received data is provided, and the convolutional encoding unit convolutionally encodes the data that has been error-corrected by the error correction unit and outputs the data to the data comparison unit.

Further, the modulation system selection device according to the present invention is
The modulation scheme selection unit compares the count value with a first threshold value, and determines that the quality state of the transmission path has deteriorated if the count value exceeds the first threshold value. A low-rate transmission modulation method is selected, the count value is compared with a second threshold value, and the count value is compared with the second threshold value.
If it is less than the threshold value of, it is judged that the quality condition of the transmission line has improved, and the modulation system for high rate transmission is selected.

Further, the modulation system selection device according to the present invention is
The first threshold value and the second threshold value set in the modulation method selection unit are variable according to a threshold value setting signal input to the modulation method selection unit. If the threshold value can be set arbitrarily, the transmission quality can be more accurately performed, so that the optimal modulation method can be more accurately selected.

Further, the modulation system selection device according to the present invention is
The predetermined number of frames that determines the period for selecting the modulation scheme set in the modulation scheme selection unit is variable according to the monitoring cycle setting signal input to the modulation scheme selection unit. If the monitoring cycle can be arbitrarily set, it is possible to prevent the modulation system from changing at a timing that normally does not need to change, and prevent unnecessary switching of the modulation system. As a result, it is possible to accurately monitor the transmission quality and maintain stable communication.

The modulation method selection method according to the present invention is
A modulation method selection method that supports multiple modulation methods and selects the modulation method according to the quality of the transmission path.The error pulse count value is counted for each frame by counting the error pulses indicating the bit error of the received data. A step of outputting a pulse having a different level depending on the presence / absence of a bit error by determining for each frame whether the received data contains a bit error, and the error detecting step. In accordance with the level of the pulse output in, the error pulse count value or a predetermined value output in the counting step is added to the count value, which is an integrated value of the error pulse count value, A modulation method selection step of selecting a predetermined modulation method from among the modulation methods for each predetermined frame.

The modulation method selection method according to the present invention is
An error correction step of correcting an error in the received data, a data comparison step of comparing the data corrected in the error correction step with the received data, and generating the error pulse each time there is a mismatched bit, Have.

The modulation method selection method according to the present invention is
When the received data is convolutionally encoded data,
The method further includes a convolutional encoding step of convolutionally encoding the received data, and the convolutional encoding step convolutionally encodes the data that has been error-corrected in the error correction step.

The modulation method selection method according to the present invention is
In the modulation method selection step, the count value is compared with a first threshold value, and if the count value exceeds the first threshold value, it is determined that the quality condition of the transmission path is deteriorated. Select a modulation method for low-rate transmission,
The count value is compared with a second threshold value, and if the count value is less than the second threshold value, it is determined that the quality condition of the transmission path is improved, and a modulation method for high-rate transmission. And a step of selecting.

A base station apparatus according to the present invention comprises the modulation method selection apparatus according to the first, second, third, fourth, fifth or sixth aspect.

A mobile station apparatus according to the present invention comprises the modulation method selection apparatus according to the first, second, third, fourth, fifth or sixth aspect.

The radio communication system according to the present invention also comprises
The base station apparatus according to claim 11 or the mobile station apparatus according to claim 12 is provided.

Further, the modulation method selection program according to the present invention is for realizing a computer as each unit included in the modulation method selection device according to any one of claims 1 to 6.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a modulation system selecting apparatus according to the present invention will be described in detail below with reference to the drawings. In the following description of the embodiments, the modulation scheme selection device and the modulation scheme selection method according to the present invention will be described in detail, but the modulation scheme selection program according to the present invention is a program for executing the modulation scheme selection method. Therefore, the description is included in the description of the modulation method selection method below.

FIG. 1 is a block diagram showing a modulation system selection device according to an embodiment of the present invention. In the figure, the modulation scheme selection apparatus of the present embodiment is provided with an error correction unit 101,
CRC detection unit 1 corresponding to the error detection unit in the claims
03, the convolutional coding unit 105, and the data comparison unit 10
7, a counter unit 109, and a modulation method selection unit 111.

The respective constituent elements of the modulation method selection device of this embodiment will be described below. First, the error correction unit 1
Reference numeral 01 is an error correction decoding circuit that performs Viterbi decoding or the like on the convolutionally encoded received data. Also, CRC
The detection unit 103 detects an error (bit error) in the data corrected by the error correction unit 101, and determines for each frame whether or not the error detection data includes a bit error. The CRC detection unit 103 outputs a pulse (H pulse) having a constant amplitude when it determines that the error correction data does not include a bit error as the CRC detection result, that is, if the data is correct, the error correction is performed. When it is determined that the data contains a bit error, that is, when the data is not correct, no pulse is output (L pulse). The CRC is a redundancy code check (Cyclic Redundancy Check) method. In addition, the convolutional encoding unit 105 includes an error correction unit 10
The data decoded in 1 is convolutionally encoded.

The data comparison unit 107 also performs an exclusive OR (EXOR) on the convolutional code data output from the convolutional coding unit 105 and the convolutionally coded received data before being input to the error correction unit 101. ), The error pulse indicating a bit error in the received data is output when these two data are erroneous.
Further, the counter unit 109 counts the error pulses output from the data comparison unit 107 to integrate the number of errors, and outputs an error pulse count value that is the integrated value of the number of errors.

Further, the modulation method selection unit 111 integrates a new error pulse count value with the count value which is the integrated value of the error pulse count values according to the CRC detection result output from the CRC detection unit 103. The modulation method is selected according to the size of the count value for each predetermined frame. More specifically, when the count values are integrated, if the CRC detection result is H pulse (received data is correct), the error pulse count value output from the counter unit 109 is added to the existing count value. When the CRC detection result is L pulse (received data is incorrect), a predetermined value is added to the existing count value. The count value thus obtained is used to determine the modulation method.

When the count value exceeds the first threshold value, it is determined that the quality condition of the transmission path (hereinafter referred to as transmission quality) is deteriorated, the low rate transmission modulation method is selected, and the count value is set to the second value. When it is below the threshold value, it is judged that the transmission quality has improved, and the modulation method for high rate transmission is selected. When the modulation method is selected, the modulation method selection unit 111 outputs a modulation method selection signal. The transmission mode signal, which is information about the modulation method, is input to the modulation method selection unit 111.

Next, a modulation method selection method performed by the modulation method selection device having the above-described components will be described in detail with reference to FIG. FIG. 2 is an example of a timing chart of each signal using the modulation method selection method of the present embodiment.

As an example, the following five modulation methods can be used by the modulation method selection device. 1. BPSK R = 1/2 (1 Mbps) 2. BPSK R = 3/4 (1.5 Mbps) 3. QPSK R = 1/2 (2 Mbps) 4. QPSK R = 3/4 (3 Mbps) 5.16 QAM R = 3/4 (6 Mbps)

The modulation system selection signal is represented by the following binary 3 bits. 000 = BPSK R = 1/2 (1 Mbps) 001 = BPSK R = 3/4 (1.5 Mbps) 010 = QPSK R = 1/2 (2 Mbps) 011 = QPSK R = 3/4 (3 Mbps) 011 = 16QAM R = 3/4 (6 Mbps)

The received data has been orthogonally transformed into the quadrature component (Q) and the in-phase component (I), and the number of data in one frame is 18 bits for each of I and Q. Also, the first threshold value for transitioning to the low-rate transmission modulation method is set to "1.
20 ", and the second threshold value for transitioning to the high-rate transmission modulation method is" 100 ". Further, the frame cycle for selecting the modulation method in the modulation method selection unit 111 is 10 frames. Furthermore, the initial modulation method is QPS
Let K R = 3/4 (3 Mbps).

First, as shown in FIG.
When the received data I (a) and Q (b) are input to 1, the error correction unit 101 outputs error-corrected data (c). This error correction data is stored in the convolutional encoder 10
5, the convolutional coding unit 105 outputs convolutional coded data I (d) and Q (e). The convolutionally encoded data I (d), Q (e) and the received data I (a), Q (b) before error correction are input to the data comparison unit 107, and the orthogonal components and the in-phase components are compared. . The data comparison unit 107 outputs error pulses I (f) and Q (g) at the position (timing) of the error bit. The error pulses I (f) and Q (g) are input to the counter unit 109, and the counter unit 109 counts the number of error pulses for each clock (h) and (i) to count the error pulse for each frame. The values I and Q are obtained. The error pulse count values I and Q are input to the modulation method selection unit 111.

On the other hand, the error correction data (c) output from the error correction unit 101 is input to the CRC detection unit 103,
After error detection is performed by the CRC detection unit 103, C
An H pulse or an L pulse (j) is output as the RC detection result. The CRC detection result (H pulse or L pulse) is input to the modulation method selection unit 111.

The modulation method selection unit 111 integrates the error pulse count values I and Q sent from the counter unit 109 with the count values I and Q which are the integrated values of the error pulse count values (k) and (l), respectively. . However, the error pulse count values I and Q when the CRC detection result is the H pulse are directly added to the existing count values I and Q.
When the detection result is the L pulse, a predetermined value (for example, 15) is added to the existing count values I and Q, respectively. The modulation method selection unit 111 uses the count values I and Q for every 10 frames.
(M) is compared with the first threshold value and the second threshold value, and the modulation method is selected according to the magnitude relation (n).

In the example shown in FIG. 2, the count values up to the 9th frame are I = 70 and Q = 58, and the CRC detection result is the L pulse (received data is incorrect) at the 10th frame. Therefore, 15 is added to each count value. Therefore, the count value of the 10th frame is
I = 85 and Q = 73. Here, since the total value of the count values I and Q of the 10th frame is “158”, which exceeds the first threshold value “120”, the modulation scheme selection unit 111 causes the modulation scheme selection unit 111 to perform the modulation scheme for low-rate transmission. QPSK R
= 1/2 (2 Mbps) modulation method selection signal "01
0 ". Therefore, the modulation method is QPSK R
= 3/4 (3 Mbps) to QPSK = 1/2 (2M
bps).

Further, the count values up to the 19th frame are I = 30 and Q = 26, and the CRC detection result is the H pulse (the received data is correct) at the 20th frame, so the count values I and Q are obtained. , The error pulse count values I = 8 and Q = 6 of the 20th frame are integrated. Therefore, the count values of the 20th frame are I = 38 and Q = 3.
It becomes 2. Here, the count values I and Q of the 20th frame
Is 70, and the second threshold value is “100”.
Therefore, the modulation method selection unit 111 determines that QPSK R = 3/4 (3 Mb) which is a modulation method for high rate transmission.
The modulation method selection signal “011” indicating the ps) is output.
Therefore, the modulation method is QPSK R = 1/2 (2 Mb
ps) to QPSK R = 3/4 (3 Mbps).

As described above, in the modulation method selection device and the modulation method selection method of this embodiment, the error pulse count is performed for each frame, and the modulation method is performed for each predetermined frame based on the accumulated count value of the error pulse count values. Is selected, and based on the error detection result (CRC detection result) by the CRC detection unit 103, when the received data is incorrect, a predetermined value is added to the count value instead of the error pulse count value. Therefore,
Even if the transmission quality is greatly deteriorated and an error that exceeds the error correction capability of the error correction unit 101 occurs, the quality state of the transmission path can be accurately obtained. As a result, the optimum modulation method can be selected.

When the received data input to the error correction unit 101 is not convolutional coded data, the modulation scheme selection apparatus of this embodiment has a convolutional coding unit 105.
The error correction data output from the error correction unit 101 is directly input to the data comparison unit 107.

Further, as shown in FIG. 3 which is a block diagram showing a modulation system selection device according to another embodiment, the modulation system selection unit 111 is provided with a first threshold value and a second threshold value. A threshold setting signal for changing may be input. If the threshold value can be set arbitrarily, the transmission quality can be more accurately performed, so that the optimal modulation method can be more accurately selected.

Further, as shown in FIG. 4 which is a block diagram showing a modulation system selection apparatus according to another embodiment, the modulation system selection unit 111 is provided with a frame number interval (monitoring period) for selecting a modulation system. A monitoring cycle setting signal for changing may be input. If the monitoring cycle can be arbitrarily set, it is possible to prevent the modulation system from changing at a timing that normally does not need to change, and prevent unnecessary switching of the modulation system. As a result, it is possible to accurately monitor the transmission quality and maintain stable communication.

The above-described modulation method selection device is used in mobile stations such as mobile phones, base stations, and radio communication systems.

[0042]

As described above, the modulation system selection device and the modulation system selection method of the present invention, the base station device and the mobile station device provided with the modulation system selection device, the wireless communication system, and the modulation system selection program are provided. According to this, even when an error exceeding the error correction capability of the error correction unit occurs due to a large deterioration in transmission quality, the quality state of the transmission path can be accurately obtained. As a result, the optimum modulation method can be selected.

[Brief description of drawings]

FIG. 1 is a block diagram showing a modulation scheme selection device according to an embodiment of the present invention.

FIG. 2 is an example of a timing chart of each signal using the modulation method selection method according to the embodiment.

FIG. 3 is a block diagram showing a modulation scheme selection device according to another embodiment.

FIG. 4 is a block diagram showing a modulation scheme selection device according to another embodiment.

FIG. 5 is a block diagram showing a bit error rate monitoring circuit described in Japanese Patent Laid-Open No. 5-160795.

[Explanation of symbols]

101 Error correction unit 103 CRC detector 105 Convolutional Coding Unit 107 Data comparison unit 109 counter section 111 Modulation method selection section

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04L 1/00 H04L 27/00 F 27/20 H04B 7/26 C F term (reference) 5K004 AA05 AA08 FD01 FD05 FE00 JD01 JD05 JE00 JF00 5K014 AA01 AA02 BA06 BA10 FA11 FA15 GA02 5K042 AA06 CA18 DA27 FA11 GA02 GA12 JA01 NA03 5K067 AA01 AA23 BB04 DD01 DD46 EE02 EE10

Claims (14)

[Claims] 1. A modulation method selection device which supports a plurality of modulation methods and selects a modulation method according to the quality condition of a transmission path, wherein error pulses indicating a bit error of received data are counted and each frame is counted. A count unit that outputs an error pulse count value, and an error detection unit that determines, for each frame, whether or not a bit error is included in the received data, and outputs a pulse of a different level depending on the presence or absence of a bit error. According to the level of the pulse output from the error detection unit, the error pulse count value or the predetermined value output from the count unit is added to the count value that is the integrated value of the error pulse count value, and the count value is added to the count value. A modulation method selecting section for selecting a predetermined modulation method from the plurality of modulation methods for each predetermined frame based on the modulation method. Expression selection device. 2. An error correction unit that corrects an error in received data, and data that has been error-corrected by the error correction unit and the received data are compared, and the error pulse is generated whenever there is a bit that does not match. The modulation method selection device according to claim 1, further comprising a data comparison unit. 3. When the received data is convolutionally encoded data, a convolutional encoding unit that convolutionally encodes the received data is provided, and the convolutional encoding unit is error-corrected data by the error correction unit. 3. The modulation method selection device according to claim 2, wherein the modulation method is convolutionally encoded and output to the data comparison unit. 4. The modulation method selection unit compares the count value with a first threshold value, and if the count value exceeds the first threshold value, the quality state of the transmission path is determined. It is judged that the signal has deteriorated, a low-rate transmission modulation method is selected, the count value is compared with a second threshold value, and if the count value is less than the second threshold value, the transmission line is 4. The modulation system selection device according to claim 1, wherein the modulation system for high-rate transmission is selected on the basis of the judgment that the quality state has improved. 5. The first threshold value and the second threshold value set in the modulation method selection unit are variable according to a threshold value setting signal input to the modulation method selection unit. 5. The modulation method selection device according to claim 4, wherein. 6. The predetermined number of frames for determining a cycle for selecting a modulation method set in the modulation method selection unit is:
The variable according to the monitoring cycle setting signal input to the modulation method selection unit.
Alternatively, the modulation method selection device according to item 5. 7. A method for selecting a modulation method corresponding to a plurality of modulation methods and selecting the modulation method according to the quality condition of a transmission path, wherein error pulses indicating a bit error of received data are counted and each frame is counted. A counting step of outputting an error pulse count value to, and an error detecting step of determining whether or not a bit error is included in the received data for each frame, and outputting a pulse of a different level depending on the presence or absence of the bit error. In accordance with the level of the pulse output in the error detecting step, the error pulse count value or the predetermined value output in the counting step is added to the count value that is the integrated value of the error pulse count value, and the count value is added to the count value. Based on the plurality of modulation schemes, a modulation scheme selection step of selecting a predetermined modulation scheme for each predetermined frame is performed. A method for selecting a modulation method, which comprises: 8. An error correction step of correcting an error in received data, comparing the data corrected in the error correction step with the received data, and generating the error pulse whenever there is a mismatched bit. The method according to claim 7, further comprising a data comparing step. 9. When the received data is convolutionally encoded data, the method further comprises a convolutional encoding step of convolutionally encoding the received data, wherein the convolutional encoding step is error-corrected in the error correction step. 9. The modulation method selection method according to claim 8, wherein the data is convolutionally encoded. 10. The modulation method selecting step compares the count value with a first threshold value, and if the count value exceeds the first threshold value, the quality state of the transmission path is determined. Comparing the count value with a second threshold value and determining that the modulation method for low rate transmission is judged to have deteriorated, and if the count value is less than the second threshold value. 10. The modulation method selection method according to claim 7, further comprising the step of determining that the quality condition of the transmission path is improved and selecting a modulation method for high-rate transmission. 11. A base station apparatus comprising the modulation scheme selecting apparatus according to claim 1, 2, 3, 4, 5 or 6. 12. A mobile station apparatus comprising the modulation scheme selection apparatus according to claim 1, 2. 13. A radio communication system comprising the base station apparatus according to claim 11 or the mobile station apparatus according to claim 12. 14. A modulation system selection program for realizing a computer as each unit included in the modulation system selection device according to claim 1.