JP2007295404A - Receiving quality measuring apparatus and communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiving quality measuring apparatus which measures a receiving quality accurately in the case of a low CNR at which an error correction is difficult. <P>SOLUTION: The receiving quality measuring apparatus exists in a communication apparatus of a receiving side constituting a communication system using an error correction code. For example, the receiving quality measuring apparatus is provided with a hard-decision means (corresponding to Code 81) to perform hard-decision to an input signal in the case that a prescribed error correction decoding is conducted to the error correction code and a receiving quality calculating means (corresponding to Codes 82 to 88) to conduct a parity check by using a parity check row of the error correction code, to calculate by using the check result a ratio at which the parity becomes zero, and to regard the ratio as an index of the receiving quality. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reception quality measurement apparatus capable of measuring reception quality even in the case of a low CNR, and more particularly to a reception quality measurement apparatus provided in a communication apparatus constituting a communication system using a linear code.

  In order to perform communication with high quality and high efficiency in mobile communication, communication control such as transmission power control, communication channel / cell switching, adaptive modulation, and retransmission control is performed. The quality of the received signal at the receiver is used as a judgment material for communication control, and the re-encoding error rate, the received power, the carrier power to noise power ratio (CNR), etc. are used as the index indicating the received quality.

  In Patent Document 1 below, a first CNR is estimated by vector calculation by a first CNR estimation unit using a plurality of orthogonal vectors obtained as a detection result of a received signal. The second CNR estimation means estimates the second CNR using the accumulated metric value obtained at the time of Viterbi decoding. Then, the CNR selection means selects the CNR value with higher reliability. Thereby, a plurality of CNRs can be measured.

JP 2001-156865 A

  Conventional reception quality measurement processing uses a metric and CNR after decoding of an error correction code. However, since CNR is calculated based on received signal variation and average level, measurement is performed when CNR is low. Have difficulty. In addition, with respect to the metrics after decoding, when the quality is so bad that error correction becomes difficult, the quality cannot be expressed correctly. As a result, there has been a problem that communication control cannot be performed correctly and communication quality and efficiency are lowered.

  The present invention has been made in view of the above, and obtains a communication device and a reception quality measurement device capable of accurately measuring quality and correctly performing communication control even in a low CNR in which error correction is difficult. For the purpose.

  In order to solve the above-described problems and achieve the object, a reception quality measurement device according to the present invention is a reception quality measurement device in a communication device on a reception side constituting a communication system using an error correction code, Hard decision means for hard-decision of an input signal when performing predetermined error correction decoding on the error correction code, and parity check using a parity check matrix of the error correction code, and using the check result, the parity is Reception quality calculation means for calculating a ratio of 0 and using the ratio as an indicator of reception quality.

  According to the present invention, it is possible to accurately measure the quality even in the case of a low CNR in which error correction is difficult and to perform communication control correctly.

  Embodiments of a communication apparatus and a reception quality measuring apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a communication system (a data transmission side communication device (transmitter) and a data reception side communication device (receiver)) that implements reception quality measurement processing according to the present invention.

  The transmitter includes error correction coding means 1 for error correction coding of transmission data, transmission means 2 for modulating error correction coded data into a radio signal, antenna sharing means 3 for separating transmission and reception, antenna 4 and A receiving means 5 for receiving a signal from the receiver via the antenna sharing means 3 and a communication control means 6 for performing communication control by a signal from the communication control means 12 of the receiver included in the received signal are provided. .

  The receiver includes an antenna sharing unit 8 for separating transmission and reception, a receiving unit 9 for receiving a radio signal via the antenna 7 and the antenna sharing unit 8, an error correction decoding unit 10 for performing error correction decoding, and reception quality. A reception quality measurement unit 11 for measuring the communication quality, a communication control unit 12 for generating a signal for communication control and communication control based on the reception quality measurement result, and a transmission unit for converting the control signal generated by the communication control unit 12 into a radio signal 13.

Next, error correction coding processing by the transmitter will be described. The error correction coding means of the present embodiment uses a convolutional code, a linear code such as a turbo code or an LDPC code. In these linear codes, if the generator matrix is G, there is a parity check matrix H having the relationship of the following equation (1).
GH ^T = 0 (1)

  For example, in the case of an error correction code having an information length of 3 bits and a codeword length of 6 bits, the parity check matrix H is a matrix shown in the following equation (2), and the codeword output from the error correction encoding means 1 is (a0, (a1, a2, a3, a4, a5), the following equation (3) is satisfied. The calculation uses the calculation on GF (2).

…（２）

... (2)

a1 + a3 = 0
a0 + a3 + a4 = 0
a1 + a2 + a4 + a5 = 0
... (3)

For example, if there is an error on the receiver side, the above relationship does not hold and one of the following expressions (4) becomes 1.
a1 + a3
a0 + a3 + a4
a1 + a2 + a4 + a5
... (4)

  If there are many errors, the number of formulas that become 1 increases, so a ratio of 0 can be used as an index of quality. Since these calculations are calculations on GF (2), it is equivalent to determining whether the number of 1s at the 1 position of the parity check matrix is an even number or an odd number. This calculation is called a parity check, and the calculated value is called a parity.

  Next, reception quality measurement processing by the receiver will be described. Here, the reception quality measuring means 11 makes a hard decision on the signal before error correction decoding (the output of the receiving means 9), and measures the reception quality using a parity check matrix.

  FIG. 2 is a diagram showing a configuration example of the reception quality measuring unit 11. The hard decision unit 81, the buffer unit 82, the parity check matrix storage unit 83, the logical product 84, the exclusive OR 85, the D-FF 86, the counter 87, codeword length division means 88 is provided.

  First, the hard decision means 81 makes a hard decision on the output signal of the reception means 9 to be a binary value of 0 if positive and 1 if negative, and accumulates the codeword length in the buffer means 82. If the hard decision is already made at the output of the receiving means 9, the hard decision means 81 is not necessary.

  Next, the buffer means 82 sequentially outputs hard decision values. In conjunction with this, the parity check storage means 83 outputs a parity check matrix, and the logical product 84 calculates the logical product of them. The exclusive OR 85 calculates an exclusive OR using the logical product output and the previous D flip-flop 86 output, and inputs the result to the D flip-flop 86 again. Thereby, the parity is calculated.

  The counter 87 measures the number of parity calculation results of 0, and the codeword length division means 88 divides the measured value by the codeword length to calculate the ratio of parity 0. The codeword length may be changed by communication control. Also, the parity check matrix may be changed by communication control.

  Thereafter, in the present embodiment, communication control such as transmission power control, communication channel / cell switching, adaptive modulation, and retransmission control is performed based on the reception quality obtained as described above. In particular, since reception quality can be measured even when error correction fails, the amount of data required at the time of retransmission can be controlled by multiplexing quality information at the time of retransmission control NACK transmission and feeding it back to the transmission side.

  As described above, in the present embodiment, the parity of the hard decision value input to the error correction coding means is calculated using the parity check matrix of the error correction code, and the ratio of 0 parity is calculated. Is used as an indicator of communication quality. Thereby, even in a situation where the quality is so bad that error correction cannot be performed, accurate communication control can be performed by measuring the reception quality, and the communication quality can be improved.

Embodiment 2. FIG.
In the first embodiment, the parity is calculated by the hard decision, but in the second embodiment, the probability that the parity becomes 0 is calculated by the soft decision, and the quality measurement accuracy is further improved.

  FIG. 3 is a diagram showing a configuration example of the second embodiment of the reception quality measuring unit 11, and includes buffer unit 82 a, parity check matrix storage unit 83 a, parity 0 probability calculation unit 84 a, integration unit 87 a, codeword length division unit. 88a. The operations other than the reception quality measuring unit 11 are almost the same as those in the first embodiment.

  In this embodiment, instead of calculating the parity, the parity 0 probability calculation means 83a calculates the probability that the parity is zero. Further, the obtained probabilities are integrated and averaged by dividing by the codeword length, and the result is used as an indicator of reception quality. The calculation method of the probability that the parity is 0 is shown below.

For example, when parity: c0 is expressed by the following equation (5), it is assumed that a0, a1, a2, 0, 1 are arbitrarily selected, and probabilities are obtained for eight patterns shown in FIG. Find the probability that is zero.
a0 + a1 + a2 = c0 (5)

Assuming that a0, a1, and a2 indicate the probability of 0 in bit units, the probability of “c0 = 0” is expressed by the following equation (6).
p (c0 = 0) = a0a1a2 + (1-a0) (1-a1) a2 + (1-a0) a1 (1-a2) + a0 (1-a1) (1-a2) (6)

When the output a from the receiving means 9 is a log likelihood ratio, it can be converted into a probability p by the following equation (7). Note that e is the base of the natural logarithm.
p = e ^a / (1 + e ^a ) (7)

Furthermore, the following equation (8) can also be used as an approximate calculation when a0, a1, and a2 are log likelihood ratios.
b = max (a0 + a1 + a2, -a0-a1 + a2, -a0 + a1-a2, a0-a1-a2)-
max (-a0 + a1 + a2, a0-a1 + a2, a0 + a1-a2, -a0-a1-a2)
p (c0 = 0) = e ^b / (1 + e ^b )
(8)

  As described above, in this embodiment, the probability that the parity is 0 is calculated by the soft decision. Thereby, in addition to the effects of the first embodiment described above, the quality can be measured with higher accuracy, the accuracy of communication control can be improved, and the communication quality can be improved accordingly.

  As described above, the reception quality measurement apparatus according to the present invention is useful in the case of low CNR, and is particularly suitable for a communication apparatus constituting a communication system using a linear code such as a convolutional code, a turbo code, or an LDPC code. ing.

It is a figure which shows the structural example of the communication system which implement | achieves the reception quality measurement process concerning this invention. It is a figure which shows the structural example of Embodiment 1 of a reception quality measurement means. It is a figure which shows the structural example of Embodiment 2 of a reception quality measurement means. It is a figure which shows the calculation method of the probability that a parity will be set to 0.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Error correction encoding means 2 Transmission means 3 Antenna sharing means 4 Antenna 5 Reception means 6 Communication control means 7 Antenna 8 Antenna sharing means 9 Receiving means 10 Error correction decoding means 11 Reception quality measurement means 12 Communication control means 13 Transmission means 81 Hard Judgment means 82, 82a Buffer means 83, 83a Parity check matrix storage means 84 AND 84a Parity 0 probability calculation means 85 Exclusive OR 86 D-FF
87 Counter 87a Integration means 88, 88a Code word length division means

Claims (3)

A reception quality measuring device in a communication device on the receiving side constituting a communication system using an error correction code,
Hard decision means for making a hard decision on an input signal when performing predetermined error correction decoding on the error correction code;
A parity check using a parity check matrix of an error correction code, a ratio at which parity is 0 is calculated using the check result, and reception quality calculation means using the ratio as an indicator of reception quality;
A reception quality measuring apparatus comprising: A reception quality measuring device in a communication device on the receiving side constituting a communication system using an error correction code,
Based on a soft decision signal that is an input signal when performing predetermined error correction decoding on the error correction code and a parity check matrix of the error correction code, a probability that parity is 0 is calculated, and the probability Reception quality calculation means using the average value of as an indicator of reception quality,
A reception quality measuring apparatus comprising: A communication device on the receiving side that constitutes a communication system using an error correction code,
A communication apparatus comprising the reception quality measuring apparatus according to claim 1.

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