JP2001024575A - Variable frame length wireless communication system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce transmission errors that cannot be removed even by a diversity reception system. SOLUTION: In a wireless communication apparatus having a diversity receiving function, a receiver estimates a state of a transmission path based on a reception level and a bit error rate, generates a frame length control signal, and sends the signal to a transmitter. The transmitter changes the frame length in accordance with the frame length control signal and transmits. If the reception level is low or the error rate is high, the frame length is shortened, and if the reception level is high and the error rate is low, the frame length is lengthened. The constant communication quality can be maintained by reducing the influence of the constantly changing state of the wireless transmission path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable frame length wireless communication system, and more particularly, to a variable frame length wireless communication system that changes a frame length according to a state of a wireless transmission path.

[0002]

2. Description of the Related Art In a conventional radio communication system, a reception state is estimated from one or a plurality of conditions such as an electric field strength, a distortion rate, and an error rate of a received signal, and the best reception result is obtained at regular time intervals. Diversity reception for selecting a reception antenna is performed. Furthermore, to ensure communication quality,
Data retransmission, interleaving, error correction codes, and the like are employed.

[0003]

However, in the conventional wireless communication system, even when the state of the wireless transmission path is good, redundant control data that is not the original transmission data, such as a synchronization word necessary for diversity reception, is added. Frame must be transmitted, which causes a reduction in transmission efficiency.
Also, strong error-correcting codes were used to ensure a certain level of communication quality even when the state of the wireless transmission path deteriorated, so the circuit became complicated and large-scale, and power consumption increased. However, there is a problem that the processing time also increases.

An object of the present invention is to solve the above-mentioned conventional problems, improve transmission efficiency according to the state of a wireless transmission path, and suppress an increase in power consumption and an increase in processing time.

[0005]

In order to solve the above-mentioned problems, the present invention provides a variable frame length wireless communication system comprising: an estimating means for estimating a state of a wireless transmission path and generating a transmission path state estimation signal; A diversity receiving apparatus comprising: a control signal generating unit that generates a frame length control signal based on a transmission path state estimation signal; and a unit that transmits a frame length control signal; a unit that receives a frame length control signal; The transmitting device is provided with variable means for changing the frame length based on the control signal.

With this configuration, the transmission efficiency can be improved by changing the transmission period of the frame information such as the synchronization word added to the frame and the frame size according to the state of the wireless transmission path. Furthermore, by changing the number of codewords per frame according to the state of the wireless transmission path, it is possible to convert a burst error into a random error by interleaving, and to maintain a constant communication quality with a simple small-scale circuit error correction code. Thus, an increase in power consumption and an increase in processing time can be suppressed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION
Estimating means for estimating a state of a wireless transmission path to generate a transmission path state estimation signal; control signal generating means for generating a frame length control signal based on the transmission path state estimation signal; and transmitting the frame length control signal Means for receiving the frame length control signal, and a variable means for changing a frame length based on the frame length control signal. When the condition of the road is bad, the frame length is shortened to lower the error rate, and when the condition is good, the frame length is lengthened to increase the transmission efficiency.

[0008] The invention described in claim 2 of the present invention is claimed in claim 1.
In the wireless communication system described above, the estimating means is means for estimating a state of a wireless transmission path based on a reception level and generating a transmission path state estimation signal. It has the effect of reducing the error rate by shortening it, and increasing the frame length if it is high to increase the transmission efficiency.

The third aspect of the present invention is the second aspect of the present invention.
In the wireless communication system according to the aspect, the control signal generation unit is a unit that generates a frame length control signal based on the number of changes of the transmission path state estimation signal, and the frame length is reduced each time the reception level decreases. It has the effect of shortening the frame length and increasing the frame length each time it becomes higher.

The fourth aspect of the present invention is the first aspect of the present invention.
In the wireless communication system described above, the estimating means is means for estimating a state of a wireless transmission path based on a code error detected at the time of decoding a received signal to generate a transmission path state estimation signal. When the number is large, the frame length is shortened, and when the number is small, the frame length is lengthened.

[0011] The invention according to claim 5 of the present invention is the invention according to claim 4.
In the wireless communication system according to the aspect, the control signal generation unit is a unit that generates a frame length control signal based on the number of changes in the transmission path state estimation signal, and reduces the frame length each time a code error increases. Then, each time it is reduced, it has the effect of increasing the frame length.

The invention according to claim 6 of the present invention is the invention according to claim 1.
In the wireless communication system described above, the estimating unit estimates a state of a wireless transmission path based on a reception level of a current frame to generate a first transmission path state estimation signal, and decodes a reception signal of a previous frame. A means for estimating the state of the wireless transmission path based on the detected code error and generating a second transmission path state estimation signal. The method estimates a transmission path state estimation signal in consideration of both the reception level and the code error. It has the effect of generating.

The invention according to claim 7 of the present invention is the invention according to claim 6
In the wireless communication system described above, the control signal generation means is a means for generating a frame length control signal based on the number of changes of the first transmission path state estimation signal, and each time a reception level becomes low. This has the effect of shortening the frame length and increasing the frame length each time the frame length increases.

The invention according to claim 8 of the present invention is directed to claim 6
In the wireless communication system described above, the control signal generating means is a means for generating a frame length control signal based on the number of changes of the second transmission path state estimation signal. It has the effect of shortening the length and increasing the frame length each time it is reduced.

According to the ninth aspect of the present invention, there is provided the sixth aspect.
In the wireless communication system described above, the control signal generating means is means for generating a frame length control signal based on the number of changes of the first and second transmission path state estimation signals, and includes a reception level and a code. It has the effect of changing the frame length regardless of which of the errors changes.

[0016] The invention according to claim 10 of the present invention is directed to claim 6.
In the wireless communication system described above, the control signal generating unit is a unit that generates a frame length control signal based on the number of changes of one of the first and second transmission path state estimation signals, This has the effect of changing the frame length by changing either the reception level or the code error.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described in detail with reference to FIGS.

(First Embodiment) A first embodiment of the present invention relates to a radio communication system which estimates a state of a transmission line based on a reception level and changes a transmission frame length according to an estimation result of a state of a radio transmission line. It is a method.

FIG. 1 is a configuration diagram of a wireless communication system according to an embodiment of the present invention. In FIG. 1, a transmitting device 1
Encodes information such as audio and images captured from the information input 8 by the error correction encoding unit 7 and
This is a device that assembles into a frame, modulates it with the modulation unit 5 and the quadrature modulation unit 4, and transmits from the transmission antenna 2 via the transmission high frequency unit 3. The control signal receiving antenna 9 is an antenna that receives the frame length control signal and passes it to the control signal receiving unit 10. The control signal analysis unit 11 is a circuit that extracts a frame length and passes it to the frame generation unit.

The receiving apparatus 20 receives radio waves with the receiving antennas 21-1 to 21-Y, and receives the reception level signals 23-1 to 23-Y and the IF signal 24-1 with the reception high frequency sections 22-1 to 22-Y. To 24-Y, a reception level determination unit 25 determines a reception level, generates a diversity switching signal 28, a diversity switching unit 26 selects an IF signal, and a demodulation unit 27 demodulates the signal. An apparatus that reproduces a frame at 29 and decodes it at an error correction decoding unit 33 to obtain an information output 35. The error rate is determined by the error determination unit 32, the frame length control signal is generated by the control signal generation unit 30, and transmitted via the control signal transmission unit 31 and the control signal transmission antenna.

FIG. 2 is a diagram showing the structure of a frame.
FIG. 3 is a diagram showing an interleaving method. FIG.
FIG. 3 is an explanatory diagram of a method of estimating a transmission path state from a reception level.

The operation of the wireless communication system according to the first embodiment of the present invention configured as described above will be described.

Information such as voice and image transmitted by the transmitting device 1 is taken in from the information input 8. The information fetched by the information input 8 is used by the error correction coding unit 7 by using an error correction code such as a block code (n, k, m) BCH code,
Perform encoding processing. The (n, k, m) BCH code is an n-bit code word obtained by adding (nk) bits of check bits to k-bit information, and corrects a random error within m bits of n bits. This code has the ability to detect an error of (m + 1) bits or more.

In the frame generation section 6, a plurality of codewords (here, a) in accordance with the control signal from the control signal analysis section 11, are subjected to the (n, k, m) BCH coding processing by the error correction coding section 7. Collectively form an (n × a) -bit data portion, perform an interleaving process for rearranging the (n × a) -bit bit sequence, and add frame information such as a synchronization word and a frame size. Then, the frame (a) shown in FIG. 2 is generated. FIG. 3 shows an example of interleaving.

The frame (a) generated by the frame generator 6 is digitally modulated by the modulator 5, then orthogonally modulated by the quadrature modulator 4, converted into a transmission frequency by the transmission high frequency unit 3, and received by the transmission antenna 2. Transmit to device 20.

The receiving apparatus 20 receives the transmission wave from the transmitting apparatus 1 with the receiving antennas 21-1 to 21-Y,
-1 to 22-Y, and the respective reception level signals 23-1 to 23-Y and I
Generate F signals 24-1 to 24-Y. The reception level determination unit 25
The reception level signals 23-1 to 23-Y are compared, and the reception high-frequency unit having the highest reception level is determined. From this determination result, a diversity switching signal 28 is generated. Diversity switching section 26 that has received diversity switching signal 28 selects the IF signal of the reception high-frequency section and connects it to demodulation section 27.

Generally, diversity switching is performed during a reception period of a redundant portion that is not original transmission information such as a frame synchronization signal, and is held until the next reception period. In this example,
It is assumed to be performed during the reception period of the frame information having the frame configuration shown in FIG. The demodulation unit 27 performs quadrature demodulation on the IF signal selected by the diversity switching unit 26, performs digital demodulation,
Output the frame (a). The frame reproducing unit 29 performs frame synchronization, performs deinterleaving processing on the (n × a) -bit data portion obtained by removing frame information such as a synchronization word and a frame size from the frame (a), and performs a (n, k, m) Output the BCH codeword.

The error correction decoding unit 33 includes a number of (n, k,
m) Perform error detection of the BCH codeword, and
In addition to notifying the error determination unit 32, if the detected error is within the correction capability, the error is corrected, and if the error exceeds the correction capability, the information included in the codeword is subjected to mute processing, and the information output is performed. Output from 35.

In such a diversity receiving apparatus, a control signal generation unit 30 generates a control signal for changing the number of codewords per frame by using a transmission path state estimation signal,
The control signal transmitting section 31 transmits the control signal from the control signal transmitting antenna. The transmitting device 1 receiving this control signal at the control signal receiving antenna 9 and the control signal receiving unit 10 transmits the control signal to the control signal analyzing unit 11.
, The number of codewords per frame is extracted from the control signal, and the frame generation unit 6 changes the frame length.

Although the modulation method used for transmitting / receiving the control signal is not particularly specified, it is assumed that the influence of the control signal from the transmission path is extremely small and negligible compared to the effect of the frame. The variable range of the frame length is limited by the precision of the clock used for the internal operation and the capacity of the storage device used for the interleave processing. Control for changing the frame length outside this range is invalid, and such control is invalid. If it occurs, it shall remain at the current frame length. A channel state estimation signal used by the control signal generation unit 30 to generate a control signal that changes the number of codewords per frame is:
It is generated by the reception level judgment unit 25 or the error judgment unit 32.

More specifically, the control signal generator 30 generates a control signal for changing the number of codewords per frame using the transmission path state estimation signal generated from the reception level after the diversity is switched by the reception level determiner 25. .

Next, how the state of the transmission path is estimated and reflected on the frame length will be described. About the method of estimating the state of the transmission path from the reception level and changing the frame length,
This will be described with reference to FIG. In the diversity reception, the determination of the best reception level from among the plurality of reception level signals 1 to Y and the diversity switching are performed during the reception period of the frame information in FIG. By such diversity reception, a plurality of reception level signals are regarded as one reception level signal. That is, it can be regarded as one transmission line connecting the transmitting device 1 and the receiving device 20.

The diversity reception level signal is compared with a preset threshold by a reception level determination section 25 to generate a transmission path state estimation signal. The threshold value is set within a range of a reception level at which correct information can be reproduced by interleaving and error correction code even if the received signal contains an error. The transmission path state estimation signal is set to “H” when the reception level is higher than the threshold, and is set to “L” when the reception level is lower than the threshold. If the transmission path state estimation signal thus generated is “H” until the next diversity determination, it is determined that the state of the transmission path is stable, and the frame length is increased. That is, the number of codewords per frame is increased. If “L”, it is determined that the state of the transmission path is not stable, and the frame length is shortened. That is, the control signal is generated by the control signal generator 30 so as to reduce the number of codewords per frame.

As described above, in the first embodiment of the present invention, the diversity receiving apparatus estimates the state of the transmission path based on the reception level in the diversity receiving apparatus, and the transmitting apparatus estimates the frame in accordance with the state estimation result. Since the length is changed, even if the radio environment is deteriorated and the reception level is lowered, the frame length can be shortened and stable communication can be performed.

(Second Embodiment) In a second embodiment of the present invention, the diversity receiving apparatus estimates the state of the transmission path based on the bit error rate, and the transmitting apparatus estimates the frame length according to the state estimation result. Is a wireless communication method that changes

The basic system configuration of the wireless communication system according to the second embodiment of the present invention is the same as that of the first embodiment.

The control signal generator 30 generates a control signal for changing the number of codewords per frame using the transmission path state estimation signal generated from the code error at the time of decoding the received signal in the error determiner 32.

The state of the transmission path is estimated from the code error detected when decoding the received signal, and the frame length is changed. The frame reproducing unit 29 detects the number a of codewords per frame from the frame information included in the frame (a) shown in FIG.
The data part subjected to the interleave processing by the transmission device 1 is deinterleaved to generate a number of (n, k, m) BCH codewords. In the example of interleaving shown in FIG. 3, the burst error caused by the change in the state of the transmission path is {2, n + 2, 2n + 2.
, (A-2) n + 3, (a-1) n + 3}, m
× a = 2a bits or less, the correction capability m = 2 (n,
(k, m) BCH codeword can be corrected as a 2-bit random error. That is, the error correction decoding unit
Detecting an error exceeding the correction capability at 33 is presumed that the state of the transmission path has changed so much that a burst error that cannot be dispersed into random errors occurs in the deinterleaving process. Therefore, error determination section 32 uses the error detection signal notified from error correction decoding section 33 to generate a transmission path state estimation signal. The transmission path state estimation signal is set to “H” when there is no error or within the correction capability, and is set to “L” when an error exceeding the correction capability is detected. If the transmission path state estimation signal thus generated is “H” until the next diversity determination, it is determined that the state of the transmission path is stable, and the frame length is increased. That is, the number of codewords per frame is increased. If “L”, it is determined that the state of the transmission path is not stable, and the frame length is shortened. That is, the control signal generation unit 30 generates a control signal so as to reduce the number of codewords per frame.

As described above, according to the second embodiment of the present invention, the diversity receiving apparatus estimates the state of the transmission path based on the bit error rate in the diversity receiving apparatus, and the transmitting apparatus according to the state estimation result. Since the frame length is changed, even if the radio environment deteriorates and the code error rate increases, the frame length can be shortened and stable communication can be performed.

(Third Embodiment) In a third embodiment of the present invention, a diversity receiving apparatus estimates a state of a transmission path based on a reception level and a bit error rate, and a transmitting apparatus estimates a state of a transmission path. Is a wireless communication system that changes the frame length according to the following.

The basic system configuration of the wireless communication system according to the third embodiment of the present invention is the same as that of the first embodiment.

The reception level determination section 25 generates a first transmission path state estimation signal from the reception level of the current frame after the diversity switching. The error determination unit 32 generates a second transmission path state estimation signal from a code error at the time of decoding the received signal of the immediately preceding frame delayed by deinterleaving processing or the like as compared with the current frame. Using the first and second channel state estimation signals,
The control signal generator 30 generates a control signal for changing the number of codewords per frame.

The state of the transmission path estimated from the reception level of the current frame and the state of the transmission path estimated from the code error detected when decoding the received signal of the immediately preceding frame are reflected in the frame length. The number of times each transmission path state estimation signal changes between “H” indicating the stability of the transmission path and “L” indicating the instability of the transmission path until the next diversity judgment is counted, and both of them are counted. If the number does not reach the preset number, it is determined that the state of the transmission path is stable, and the frame length is increased. That is, the number of codewords per frame is increased. If both of them reach a preset number of times, it is determined that the state of the transmission path is not stable, and the frame length is shortened. That is, the control signal is generated by the control signal generator 30 so as to reduce the number of codewords per frame.

As described above, according to the third embodiment of the present invention, the diversity communication apparatus estimates the state of the transmission path based on the reception level and the bit error rate in the diversity reception apparatus. Since the frame length is changed according to the estimation result, even if the radio environment deteriorates and the reception level and the bit error rate deteriorate, the frame length can be shortened and stable communication can be performed.

[0045]

As is apparent from the above description, according to the present invention, the radio communication system is provided with estimating means for estimating the state of the radio transmission path to generate a transmission path state estimation signal, and A diversity receiving device comprising: a control signal generating unit that generates a frame length control signal based on the frame length control signal; and a unit that receives the frame length control signal. The transmission device is provided with a variable means for changing the number of bits, so that transmission efficiency can be improved, and a long interleaving process can be performed by increasing the number of codewords per frame, and burst errors can be dispersed into random errors. Therefore, it is possible to secure a certain communication quality with the error correction code of a simple small-scale circuit, and suppress an increase in power consumption and an increase in processing time. The effect is obtained that that.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a wireless communication system according to first to third embodiments of the present invention;

FIG. 2 is a diagram illustrating a frame configuration of a wireless communication system according to the first to third embodiments of the present invention;

FIG. 3 is an explanatory diagram of an interleaving process of a wireless communication system according to the first to third embodiments of the present invention;

FIG. 4 is an explanatory diagram of a method of estimating a transmission path state from a reception level of a wireless communication system according to the first and third embodiments of the present invention.

[Explanation of symbols]

 Reference Signs List 1 transmitting device 2 transmitting antenna 3 transmitting high-frequency unit 4 orthogonal modulating unit 5 modulating unit 6 frame generating unit 7 error correcting coding unit 8 information input 9 control signal receiving antenna 10 control signal receiving unit 11 control signal analyzing unit 20 receiving device 21- 1 ~ 21-Y Receive antenna 22-1 ~ 22-Y Receive high frequency section 23-1 ~ 23-Y Receive level signal 24-1 ~ 24-Y IF signal 25 Receive level judgment section 26 Diversity switching section 27 Demodulation section 28 Diversity Switching signal 29 Frame playback unit 30 Control signal generation unit 31 Control signal transmission unit 32 Error determination unit 33 Error correction decoding unit 34 Control signal transmission antenna 35 Information output

Continued on the front page (72) Inventor Terumi Hakamada 2-5-5 Meidori, Izumi-ku, Sendai, Miyagi Prefecture Inside Matsushita Communication Sendai Laboratory Co., Ltd. (72) Inventor Shohei Taniguchi 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture No. Matsushita Communication Industrial Co., Ltd. F-term (reference) 5K059 CC03 DD02 DD05 EE02 5K067 AA13 AA14 AA23 AA43 CC04 CC24 DD44 DD46 FF16 HH26 KK03

Claims (10)

[Claims] An estimating means for estimating a state of a wireless transmission path to generate a transmission path state estimation signal; a control signal generation means for generating a frame length control signal based on the transmission path state estimation signal; Means for transmitting a length control signal in the diversity receiver, and means for receiving the frame length control signal, and variable means for changing a frame length based on the frame length control signal are provided in the transmitter. Wireless communication system. 2. The wireless communication system according to claim 1, wherein said estimating means is means for estimating a state of a wireless transmission path based on a reception level and generating a transmission path state estimation signal. 3. The wireless communication system according to claim 2, wherein said control signal generating means is means for generating a frame length control signal based on the number of changes of said transmission path state estimation signal. 4. The apparatus according to claim 1, wherein said estimating means is means for estimating a state of the wireless transmission path based on a code error detected at the time of decoding the received signal and generating a transmission path state estimation signal. The wireless communication system described. 5. The wireless communication system according to claim 4, wherein said control signal generating means is means for generating a frame length control signal based on the number of changes of said transmission path state estimation signal. 6. The estimation unit estimates a state of a wireless transmission path based on a reception level of a current frame to generate a first transmission path state estimation signal, and detects the state at the time of decoding a reception signal of a previous frame. 2. The wireless communication system according to claim 1, wherein the wireless communication system is means for estimating a state of the wireless transmission path based on the code error and generating a second transmission path state estimation signal. 7. The wireless communication system according to claim 6, wherein said control signal generating means is means for generating a frame length control signal based on the number of changes of said first transmission path state estimation signal. . 8. The wireless communication system according to claim 6, wherein said control signal generating means is means for generating a frame length control signal based on the number of changes of said second transmission path state estimation signal. . 9. The control signal generating means according to claim 6, wherein said control signal generating means is means for generating a frame length control signal based on the number of changes of said first and second transmission path state estimation signals. Wireless communication method. 10. The control signal generating unit according to claim 1, wherein the control signal generating unit generates a frame length control signal based on the number of changes of one of the first and second transmission path state estimation signals. Item 7. The wireless communication method according to Item 6.