JP5375801B2 - Diversity receiving apparatus, diversity receiving system, and diversity receiving method used therefor - Google Patents

Description

  The present invention relates to a diversity receiving apparatus, a diversity receiving system, and a diversity receiving method used therefor, and more particularly to a diversity receiving apparatus that receives a certain transmission signal by a plurality of antennas.

  The diversity combining method in the above diversity receiver includes a selective combining method for selecting an input signal with the maximum reception level, an equal gain combining method for combining the phases of the input signals, and an SNR after combining the input signals. There is a maximum ratio synthesis method in which (Signal to Noise Ratio) is maximized (see, for example, Patent Document 1). The configuration of the diversity combining method is disclosed in Patent Document 2 below.

  In wireless communication, maximum ratio combining diversity using a decision feedback equalizer (DFE: DFE) is proposed (for example, see Non-Patent Document 1). In this method, transmission / reception data is divided into a training signal and a data signal. During the training signal, the tap coefficients of the DFE are controlled so as to cancel the interference wave according to an adaptive algorithm [LMS (Least Mean Square), etc.], and are further controlled so that the combined SNR becomes maximum.

Japanese Patent Laid-Open No. 08-172390 JP-A-10-051366

“Interference Cancellation Characteristics of DFE Transversal Combining Diversity in Mobile Radio—Comparison with Metric Synthesis—” (Jin Yoshino, Hiroshi Suzuki, IEICE Transactions B-II Vol. J 76-B-II No. 7 pp.584-595 July 1993)

  In the above maximum ratio combining diversity method, if the training signal is sufficiently long, when the SNR of one system deteriorates, the tap coefficient of that system converges to a small value, and the contribution of the system having a poor SNR almost disappears. The performance at the time of maximum ratio synthesis does not deteriorate.

  However, in the maximum ratio combining diversity method described above, convergence of DFE tap coefficients may be insufficient in a system with a short training signal. In that case, when the SNR of one of the systems deteriorates, the tap coefficient of that system is not sufficiently small, so performing maximum ratio combining may degrade the performance compared to the selected diversity.

  In the case of the diversity combining method described above, as shown in FIG. 7, the performance is in the order of maximum ratio combining diversity> equal gain combining diversity> selective combining diversity, and when the SNR of one of the above systems deteriorates By performing the maximum ratio combining, the performance is degraded from the selection diversity having the lowest performance.

  Accordingly, an object of the present invention is to provide a diversity receiving apparatus, a diversity receiving system, and a diversity receiving method used for them that can solve the above-described problems, shorten the training signal, and increase the transmission rate.

The diversity receiver according to the present invention is:
A diversity receiver that receives a transmission signal by a plurality of antennas,
A decision feedback type equalizer including a decision error output means for outputting a decision error representing a difference between a signal to be originally obtained and an equalization result every time one symbol is processed, and after combining an input signal from the antenna Maximum ratio combining diversity means for combining so that SNR (Signal to Noise Ratio) is maximized;
Selection diversity means that uses the decision feedback equalizer and selects a signal having the maximum reception level among the input signals from the antenna;
Selection means for selecting one of said maximum ratio combining diversity means and an output signal from the selection diversity means respectively,
Have a selection control means for controlling said selection means to select the best signal among said maximum ratio combining diversity means and an output signal from the selection diversity means respectively,
The selection control means takes an average of one burst with respect to the determination error from each of the determination feedback equalizers, and controls to select an output signal having the minimum average value.

  A diversity reception system according to the present invention includes the diversity reception apparatus described above.

The diversity reception method according to the present invention includes:
A diversity receiving method used in a diversity receiving apparatus for receiving a transmission signal by a plurality of antennas,
A decision feedback type equalizer including a decision error output means for outputting a decision error representing a difference between a signal to be originally obtained and an equalization result every time one symbol is processed, and after combining an input signal from the antenna Maximum ratio combining diversity processing for combining SNR (Signal to Noise Ratio) to the maximum;
Selective diversity processing that uses the decision feedback equalizer and selects a signal that has a maximum reception level among the input signals from the antenna;
A selecting process for selecting one of said maximum ratio combining diversity processing and the selection diversity processing each processing result,
Have a selection control processing for controlling so as to select the best results among the maximum ratio combining diversity processing and the selection diversity processing each processing result,
In the selection control process, an average of one burst is averaged with respect to a determination error from each of the determination feedback equalizers, and control is performed so as to select a result having the minimum average value.

  The present invention has an effect that the training signal can be shortened and the transmission rate can be increased by adopting the configuration and operation as described above.

It is a block diagram which shows the structural example of the diversity receiver by embodiment of this invention. It is a block diagram which shows the structural example of DFE11,12 shown in FIG. It is a block diagram which shows the structural example of DFE21 shown in FIG. It is a block diagram which shows the structural example of the selection control part shown in FIG. It is a figure which shows an example of the determination error in embodiment of this invention. It is a figure which shows the other example of the determination error in embodiment of this invention. It is a figure which shows the BER result corresponding to FIG.

  Next, embodiments of the present invention will be described with reference to the drawings. First, the outline of the diversity receiver according to the present invention will be described. The diversity receiving apparatus according to the present invention is an apparatus that receives a transmission signal by a plurality of antennas, performs both maximum ratio combining diversity and selection diversity, and selects the best result among them. Thus, it is possible to shorten the training signal described in the background art and increase the transmission rate.

  That is, in the diversity receiver according to the present invention, it is possible to eliminate the case where the performance is deteriorated as compared with the selected diversity as a result of performing the maximum ratio combining diversity in the system with a short training signal.

  Here, the selection diversity is a method of selecting an input signal that maximizes the reception level, and the maximum ratio combining diversity is a combination that maximizes the SNR (Signal to Noise Ratio) after combining the input signals. (For example, refer to Patent Document 1).

  In the diversity receiver according to the present invention, a decision feedback equalizer (DFE) is used for the maximum ratio combining diversity and the selection diversity, respectively.

  Each DFE outputs a determination error every time one symbol is processed. The determination error represents the difference between the signal to be originally obtained and the equalization result, and it can be said that the smaller the determination error, the better the SNR.

  In the diversity receiver according to the present invention, the average of one burst (one group of burst-like received signals) is averaged with respect to the determination error from each DFE, and the average value of the results of each DFE is the smallest. By selecting, the training signal can be shortened and the transmission rate can be increased.

  FIG. 1 is a block diagram showing a configuration example of a diversity receiver according to an embodiment of the present invention. In FIG. 1, the diversity receiver according to the embodiment of the present invention includes a selection diversity unit 1, a maximum ratio combining diversity unit 2, a selection control unit 3, and a selector 4.

  DFEs 11 and 12 are arranged in the selection diversity unit 1, and DFEs 21 are arranged in the maximum ratio combining diversity unit 2. In each of these DFEs 11, 12, and 21, each time one symbol of an input signal from two antennas (not shown) of systems # 1 and # 2 is processed, the determination error used for the processing is sent to the selection control unit 3. Output.

  The selection control unit 3 averages one burst for the determination error output from each of the DFEs 11, 12, and 21, and among the results from each of the DFEs 11, 12, and 21, obtains the result whose average value is minimum. The selector 4 is controlled to select. The selector 4 selects and outputs one of the processing results of each of the DFEs 11, 12, and 21 based on the control from the selection control unit 3.

  FIG. 2 is a block diagram showing a configuration example of the DFEs 11 and 12 shown in FIG. FIG. 2 shows a configuration of a decision feedback equalizer (DFE 11, 12) used in the selection diversity unit 1. In the following description, the DFE 11 will be described, but the DFE 12 has the same configuration and operation as the DFE 11.

  In FIG. 2, the DFE 11 includes FF (Feed Forward) taps 111 and 112, multipliers 113 to 115 and 120, an adder 116, a data determination unit 117, a switch 118, an FB (Feed Back) tap 119, and , A determination error output unit 121, a coefficient update algorithm [LMS (Least Mean Square), RLS (Recursive Last Square), etc.] 122, and a memory 123.

  Next, processing in the DFE 11 will be described. Usually, the FF taps 111 and 112 have a tap interval of T / 2, and the FB tap 119 has a tap interval of T (T = symbol period).

  In the DFE 11, when signals (y [n], y [n + 1], y [n + 2]) are input, the multipliers 113 to 115 multiply the input signal and the output signals of the FF taps 111 and 112 by the tap coefficient. And the adder 116 takes the sum (z [n]) of the multiplication results of each tap.

In the training section, the training signal is taken out from the memory 123 (output r [n] from the switch 118. In the data section (tracking mode), the data determination unit 117 is closest to z [n] (= transmission). Output signal point (output r [n] from the switch 118).

  R [n] from the switch 118 is input to the FB tap 119. The determination error output unit 121 calculates r [n] −z [n] and outputs the determination error e [n] to the coefficient update algorithm 122 and the selection control unit 3.

  In the coefficient update algorithm 122, the tap coefficient is updated according to the algorithm (LMS, RLS, etc.) and output to the multipliers 113 to 115, 120.

  The DFE 11 returns to the signal input process. However, in the next process, the data of y [n + 4], y [n + 3], y [n + 2] are input to the DFE 11 in order from the left.

  FIG. 3 is a block diagram showing a configuration example of the DFE 21 shown in FIG. FIG. 3 shows a configuration of a decision feedback equalizer (DFE 21) used in the maximum ratio combining diversity unit 2. The DFE 21 has the same processing method as the DFEs 11 and 12 used for the selection diversity unit 1 except that there are two FF taps.

  In FIG. 3, the DFE 21 includes FF taps 211 to 214, multipliers 215 to 220, 225, an adder 221, a data determination unit 222, a switch 223, an FB tap 224, a determination error output unit 226, The coefficient update algorithm 227 and a memory 228 are included.

  FIG. 4 is a block diagram showing a configuration example of the selection control unit 3 shown in FIG. In FIG. 4, the selection control unit 3 includes average calculation units 31 to 33 and a minimum determination error detection unit 34.

  The average calculation unit 31 averages one burst of the determination error e [n] of the system # 1 from the DFE 11 of the selection diversity unit 1 and outputs the average value to the minimum determination error detection unit 34.

  The average calculation unit 32 averages one burst of the determination error e [n] of the system # 2 from the DFE 12 of the selection diversity unit 1 and outputs the average value to the minimum determination error detection unit 34.

  The average calculation unit 33 averages one burst of the determination error e [n] from the DFE 21 of the maximum ratio combining diversity unit 2 and outputs the average value to the minimum determination error detection unit 34.

  The minimum determination error detection unit 34 compares the average values from each of the average calculation units 31 to 33, detects the minimum determination error among the average values, and displays the detection result as a control signal (DFE 11 of the selection diversity unit 1, 12 and a signal that controls which of the DFE 21 of the maximum ratio combining diversity unit 2 is selected) is output to the selector 4.

  FIG. 5 is a diagram showing an example of the determination error in the embodiment of the present invention, FIG. 6 is a diagram showing another example of the determination error in the embodiment of the present invention, and FIG. 7 corresponds to FIG. It is a figure which shows a BER (Bit Error Rate) result. 5 and 6, the vertical axis represents the determination error and the horizontal axis represents the symbol. In FIG. 7, the method of the present embodiment, the selected diversity # 1, the selected diversity # 2, and the maximum ratio combining. The relationship between diversity BER and Eb / N0 is shown.

  In FIG. 5, for example, the training error is 3 symbols, the data is 40 symbols, and the determination error when the SNR of the input signal of the system # 2 is not extremely deteriorated is shown. In FIG. The determination error when the SNR is extremely deteriorated is shown.

  In FIG. 5, among the three types of determination errors of the selection diversity of the system # 1, the selection diversity of the system # 2, and the maximum ratio combining diversity, the average value is the minimum, which is the determination error of the maximum ratio combining diversity. The maximum ratio combined diversity result is selected.

  In FIG. 6, among the three types of determination errors of the selection diversity of the system # 1, the selection diversity of the system # 2, and the maximum ratio combining diversity, the average value has the smallest determination error of the selection diversity of the system # 1. The selection diversity result of system # 1 is selected by the selector.

  This is because the determination error of the maximum ratio combining diversity is affected by the determination error of the selection diversity of the system # 2 in which the SNR is extremely deteriorated, so that the average value of the determination errors of the selection diversity of the system # 1 is minimized. It is.

  As described above, in the present embodiment, both the maximum ratio combining diversity and the selection diversity are performed, and the best result among those results is selected, thereby shortening the training signal and increasing the transmission rate. be able to.

  That is, in the diversity receiver according to the present embodiment, it is possible to eliminate the case where the performance is deteriorated more than the selected diversity as a result of performing the maximum ratio combining diversity in the system with a short training signal.

  In the above description of the embodiment of the present invention, the input signals from the two antennas of the system # 1 and the system # 2 are described, but the input signals of the n systems (n is an integer of 3 or more). Is also applicable.

  The present invention can be applied to diversity reception of an aircraft radio, a mobile communication device, a digital TV (television) relay device, and the like.

1 Selective Diversity Department
2 Maximum ratio combining diversity section
3 Selection control unit
4 Selector 11, 12, 21 DFE
31-33 Average calculator
34 Minimum determination error detection unit 111, 112,
211 to 214 FF taps 113 to 115, 120,
215-220,225 multiplier
116,221 adder
117, 222 Data judgment unit
118,223 switches
119,224 FB tap
121,226 judgment error output unit
122,227 Coefficient update algorithm
123,228 memory

Claims (5)

A diversity receiver that receives a transmission signal by a plurality of antennas,
A decision feedback type equalizer including a decision error output means for outputting a decision error representing a difference between a signal to be originally obtained and an equalization result every time one symbol is processed, and after combining an input signal from the antenna Maximum ratio combining diversity means for combining so that SNR (Signal to Noise Ratio) is maximized;
Selection diversity means that uses the decision feedback equalizer and selects a signal having the maximum reception level among the input signals from the antenna;
Selection means for selecting one of said maximum ratio combining diversity means and an output signal from the selection diversity means respectively,
Have a selection control means for controlling said selection means to select the best signal among said maximum ratio combining diversity means and an output signal from the selection diversity means respectively,
The selection control means takes an average of one burst with respect to the determination error from each of the determination feedback equalizers, and controls to select an output signal having the minimum average value. apparatus. 2. The diversity receiver according to claim 1, wherein in the decision feedback equalizer, a tap coefficient of DFE is controlled to cancel an interference wave according to an adaptive algorithm during a training signal . A diversity receiving system comprising the diversity receiving device according to claim 1. A diversity receiving method used in a diversity receiving apparatus for receiving a transmission signal by a plurality of antennas,
A decision feedback type equalizer including a decision error output means for outputting a decision error representing a difference between a signal to be originally obtained and an equalization result every time one symbol is processed, and after combining an input signal from the antenna Maximum ratio combining diversity processing for combining SNR (Signal to Noise Ratio) to the maximum;
Selective diversity processing that uses the decision feedback equalizer and selects a signal that has a maximum reception level among the input signals from the antenna;
A selection process for selecting one of the processing results of the maximum ratio combining diversity process and the selection diversity process;
A selection control process for controlling to select the best result among the processing results of the maximum ratio combining diversity process and the selection diversity process,
In the selection control process, a diversity reception method is characterized in that an average of one burst is taken with respect to a determination error from each of the determination feedback equalizers, and control is performed so as to select a result having the minimum average value. . 5. The diversity reception method according to claim 4, wherein in the decision feedback equalizer, a tap coefficient of DFE is controlled to cancel an interference wave according to an adaptive algorithm during a training signal .

Images