JPH10215211A - Diversity receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the bit error rate by adopting weighted combining in response to a reception-desired signal power to interference wave power ratio(SIR) even when the SIR is high. SOLUTION: Correlation values C1, C2 between specific pattern reception outputs S1, S2 and specific patterns are found (20), square sums K1, K2 of in-phase components and quadrate components of the C1, C2 are found, respectively (22), and an SIR estimate section 23 estimate the SIR based on SIR1(t)=k1(t)/(1-k1(t)) and on SIR2(t)=k2(t)/(1-k2(t)) in the case of synchronization detection and based on SIR1(t)=√k1(t)/(1-√k1(t)) and on SIR2(t)=√k2(t)/(1-√k2(t)) in the case of delay detection respectively and estimated values of the SIR estimate section 23 are used for weight coefficients ω1, ω2 for demodulation outputs S1, S2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity receiver for demodulating received signals from a plurality of antennas and combining the demodulated outputs by a maximum ratio combining method.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional diversity receiver (Fumiaki Maehara, Osamu Nakamura, Hitoshi Takanashi, "Examination of maximum ratio combining diversity using a correlator", 1996 IEICE Autumn Conference, B-469). The radio signal received by the antenna 11 is detected by the receiver 13,
The output R1 is input to the demodulator 15. The radio signal received by the antenna 12 is detected by the receiver 14,
The output R2 is input to the demodulator 16. Demodulator 15,
16, the output signals R1, R2 from the respective receivers
Are normalized by a limiter, and then demodulated and output.

The weighting factor control unit 17 comprises a correlator 20 and a weighting factor output unit 21.
The demodulators 15 and 16 evaluate the ratios of the desired signals included in the radio signals received by the demodulators 15 and 16 and output S1 and S2.
(S1, S2 are complex signals) and weight coefficients ω1, ω2
Is calculated. The correlator 20 utilizes the fact that a signal of a specific pattern, for example, a unique word is inserted on the transmission side, and uses the output signal S
1, S2 and the signal of the specific pattern, respectively, and output correlation values C1, C2. More specifically, the correlation between the in-phase component SI1 and the quadrature component SQ1 of the output S1 (S2) of the demodulator and the signal of the specific pattern is performed to obtain the in-phase component CI1 and the quadrature component CQ1 of the correlation value C1 (C2). .

On the other hand, the weighting coefficient output unit 21
By calculating the sum of squares of the in-phase component CI1 and the quadrature component CQ1 of the output signal C1 (C2) of 0, weight coefficients ω1 and ω2 for the outputs S1 and S2 of each demodulator are obtained. From the weight coefficients ω1 and ω2 obtained here, it is possible to know the ratio of the desired wave power to the signal power received in each antenna system.

In the diversity combining section 18, each demodulator 1
The outputs S1 and S2 are multiplied by the weighting factors ω1 and ω2 obtained by the weighting factor control unit 17, respectively, and the multiplied values are combined and output. The decoder 19 decodes the combined signal obtained by the diversity combining unit 18 into binary data.

[0006]

In the conventional diversity receiving apparatus using the correlator as described above, the weighting factors ω1 and ω2 obtained by the weighting factor control unit 17 are determined by the signal power received in each antenna system. Of the desired wave power. Therefore, in the conventional diversity receiving apparatus that performs weighting synthesis on the outputs S1 and S2 of the respective demodulators based on the ratio of the desired signal power to the received signal power, the reception desired signal power / interference signal power ratio When the (reception SIR) is large, the weighting factors converge to 1, so that the outputs S1 and S2 of each demodulator cannot be weighted in proportion to the reception SIR, and the reception SIR
There is a problem that diversity gain cannot be obtained when weighting is performed in proportion to IR.

For example, when an interference signal due to co-channel interference is included, the outputs S1,
In order to perform weighting on S2 in proportion to the received SIR, the weighting control unit 17 shown in FIG. 5 uses D for the desired signal power, U for the interference signal power, and N for the noise generated in the receiver.
Then, D / (U + N) should be measured. However, in the conventional diversity receiving apparatus, the weighting control unit 17 outputs the outputs S1 and S2 of the demodulators,
D / (D + U + N) is to be measured in order to perform weighted synthesis based on the ratio of the desired signal power to the received signal power. FIG. 5 shows the relationship between the reception SIR and the weight coefficient. In FIG. 5, the weighting factor calculated by the weighting control unit 17 of the conventional diversity receiving apparatus is:
It can be seen that when the received SIR is larger than 10 dB, it converges to 1 (0 dB). That is, in the conventional diversity receiving apparatus, when the reception SIR is larger than 10 dB, the outputs S1 and S2 of each demodulator cannot be weighted in proportion to the reception SIR, and the weighting is performed when the reception SIR is used. Diversity gain cannot be obtained.

In view of such a conventional problem, the present invention estimates a reception SIR using a correlation value between output signals of a plurality of demodulators in which a specific pattern is inserted and a specific pattern on a transmission side, By using the estimated value as a weighting factor, the reception S
An object of the present invention is to increase the contribution of the output of the antenna demodulator having a large IR.

[0009]

According to the present invention, the correlation value between the demodulated output of each antenna-based demodulator and the specific pattern with respect to the received signal in which the specific pattern is inserted on the transmitting side is calculated by each correlator. From the sum of the squares of the in-phase and quadrature components of the correlation values obtained by these correlators, the estimated value of the desired signal power to interference signal power ratio (SIR) is calculated as SI
These are calculated by the R estimating means, and these calculated values are used as weighting factors for the corresponding decoded output in the maximum ratio combining.

According to the present invention, the weight coefficient output unit does not output the sum of squares of the in-phase component and the quadrature component of the correlation value obtained by the correlator as the weight coefficient corresponding to the output of each demodulator. It differs from the prior art in that a desired signal power to interference signal power ratio is obtained from the sum of squares of the in-phase and quadrature components of the correlation value obtained by the correlator, and that value is output as a weight coefficient. Due to this difference, the present invention can increase the contribution of the output of the antenna demodulator having a large reception SIR to the diversity-combined signal, and obtain the effect of improving the transmission characteristics by the diversity reception.

[0011]

FIG. 1 shows an embodiment of the present invention, in which parts corresponding to those in FIG. 4 are denoted by the same reference numerals. In the present invention, the weight coefficient output unit 21 in the weight coefficient control unit 17 includes a square calculation unit 22 and an SIR estimation unit 23. The correlator 20 utilizes the fact that a signal of a specific pattern, for example, a unique word is inserted on the transmission side, as in the related art, and uses the output signals S1, S
2 and the signal of the specific pattern, the in-phase component CI1 and quadrature component CQ1 of the correlation value C1 (C1 is a complex signal), and the in-phase component C2 of the correlation value C2 (C2 is a complex signal).
Obtain I2 and orthogonal component CQ2.

The weighting coefficient output unit 21 includes a square calculating unit 22
Then, for each of the output signals C1 and C2 of the correlator 20, the square sums k1 and k2 of the in-phase component and the quadrature component are obtained. The SIR estimator 23 calculates the reception SIR of each antenna system from the output signals k1 and k2 of each square calculator 22, and obtains weight coefficients ω1 and ω2 for the outputs S1 and S2 of each demodulator. From the weighting coefficients ω1 and ω2 obtained here, the SIR in each antenna system can be known. The processing in the diversity combining unit 18 using the weight coefficients ω1 and ω2 is the same as in the related art.

Hereinafter, the operation of the weight coefficient control section 17 of the embodiment will be described in more detail. First, the demodulators 15, 1
The case where the received signal is detected by synchronous detection in 6 will be described. Output signals S1 (t) and S2 (t) of each demodulator input to the correlator 20 are normalized by a limiter in the demodulator, and when an interference signal due to co-channel interference is included, (1) It can be expressed as an equation.

S1 (t) = (D1 (t) + U1 (t)) / | D1 (t) + U1 (t) | S2 (t) = (D2 (t) + U2 (t)) / | D2 (t) + U2 (t) | (1) where S1 (t), S2 (t), D1 (t), U1
(T), D2 (t) and U2 (t) are complex signals, and D
1 (t) and U1 (t) are the desired wave component and the interference wave component of the output of the demodulator when the limiter of the antenna 1 is not used, and D2 (t) and U2 (t) are the antenna 2 respectively. The desired wave component and the interference wave component of the output of the demodulator when the limiter of the system is not used. By the correlator 20,
Since the ratio of the level of the desired wave component can be known, the output of the correlator 20 can be expressed as in the equation (2).

S1 (t) = D1 (t) / | D1 (t) + U1 (t) | S2 (t) = D2 (t) / | D2 (t) + U2 (t) | (2) Weight coefficient output unit In the square calculating unit 22 in 21, the correlator 2
The output of 0 is squared and measured in the power dimension.
Therefore, the output signals S1 (t), S2 of each demodulator
The output signal k1 of the square calculator 22 corresponding to (t)
(T) and k2 (t) can be expressed by equation (3).

[0016] k1 (t) = | D1 ( t) | 2 / | D1 (t) + U1 (t) | 2 k2 (t) = | D2 (t) | 2 / | D2 (t) + U2 (t) | ² (3) From the equation (3), the output signals k1 (t),
From k2 (t), the ratio of the desired signal power to the signal power received in each antenna system can be known.

The SIR estimator 23 calculates the SIR of each branch (antenna system) from the output signals k1 (t) and k2 (t) of the square calculator 22, and the procedure will be described below. In equation (3), if the desired signal and the interference signal are orthogonal, equation (3) can be transformed into equation (4).

[0018] k1 (t) = | D1 ( t) | 2 / (| D1 (t) | 2 + | U1 (t) | 2) k2 (t) = | D2 (t) | 2 / (| D2 ( ^{t) | 2 + | U2 (} t) | 2) (4) SIR of each antenna system (SIR1 (t), SIR2
(T)) can be expressed as equation (5) by modifying equation (4). SIR1 (t) = | D1 (t) | ² / U1 (t) | ² = k1 (t) / (1-k1 (t)) SIR2 (t) = | D2 (t) | ² / U2 ( t) | ² = k2 (t) / (1-k2 (t)) (5) As described above, in the SIR estimating unit 23, the respective antennas from the output signals k1 (t) and k2 (t) of the square calculating unit 22 are obtained. It is possible to estimate the SIR of the system (SIR1 (t), SIR2 (t)).

Next, the case where the received signal is detected by the demodulators 15 and 16 by delay detection will be described.
Output signal S1 of each demodulator input to correlator 20
(T) and S2 (t) are normalized by a limiter in the demodulator, and when an interference signal due to co-channel interference is included, can be expressed as in equation (6).

S1 (t) = (D1 (t) + U1 (t)) · (D1 (tT) + U1 (tT)) / | (D1 (t) + U1 (t)) · (D1 (tT) + U1 (tT) )) | S2 (t) = (D2 (t) + U2 (t)). (D2 (tT) + U2 (tT)) / | (D2 (t) + U2 (t)). (D2 (tT) + U2 (tT) )) | (6) where S1 (t), S2 (t), S1 (t-T), S1
2 (t−T), D1 (t), U1 (t), D1 (t−
T), U1 (t-T), D2 (t), U2 (t), D2
(T-T) and U2 (t-T) are complex signals, and D1
(T), D1 (t-T) and U1 (t), U2 (t-
T) is a desired wave component and an interference wave component of the output of the demodulator when the limiter of the antenna 1 system is not used, and D2
(T), D2 (t-T) and U2 (t), U2 (t-
T) is a desired wave component and an interference wave component of the output of the demodulator when the limiter of the antenna 2 is not used. Since the level ratio of the desired wave component can be known by the correlator 20, the output of the correlator 20 can be expressed as in equation (7). Here, it is assumed that the change of the desired wave component and the interference wave component between one symbol is sufficiently small.

[0021] S1 (t) ≒ D1 (t ) 2 / | D1 (t) + U1 (t) | 2 S2 (t) ≒ D2 (t) 2 / | D2 (t) + U2 (t) | 2 (7) In the square calculator 22 in the weight coefficient output unit 22, the correlator 2
The output of 0 is squared and measured. Therefore, the output signals k1 (t) and k2 (t) of the square calculator 22 corresponding to the output signals S1 (t) and S2 (t) of each demodulator can be expressed by the equation (8).

K1 (t) = (D1 (t)) ⁴ / | D1 (t) + U1 (t) | ⁴ k2 (t) = (D2 (t)) ⁴ / | D2 (t) + U2 (t) | ⁴ (8) From equation (8), the output signals k1 (t),
From k2 (t), the ratio of the desired signal power to the signal power received in each antenna system can be known.

The SIR estimator 23 calculates the SIR of each branch (antenna system) from the output signals k1 (t) and k2 (t) of the square calculator 22, and the procedure will be described below. In equation (8), if the desired signal and the interference signal are orthogonal, equation (8) can be transformed into equation (9).

[0024] k1 (t) = | D1 ( t) | 4 / (| D1 (t) | 2 + | U1 (t) | 2) 2 k2 (t) = | D2 (t) | 4 / (| D2 ^{(t) | 2 + | U2} (t) | 2) 2 (9) SIR of each antenna system (SIR1 (t), SIR2 ( t)
Can be expressed as equation (10) by modifying equation (9).

SIR1 (t) = | D1 (t) | ² / UI (t) | ² = k1 (t) / (1-√k1 (t)) SIR2 (t) = | D2 (t) | ² / | U2 (t) | ² = √k2 (t) / (1−√k2 (t)) (10) As described above, in the SIR estimating unit 23, each of the output signals k1 and k2 of the square calculating unit 22 is used. Antenna SIR (SI
R1 (t), SIR2 (t)) can be estimated.

FIG. 2 is a diagram showing a simulation result of the output distribution of the weight coefficient control unit 17 in the apparatus of the present invention shown in FIG. 1 in comparison with that of the conventional apparatus shown in FIG. The specifications of the simulation are described below. The modulation and demodulation method is π / 4-QPSK differential detection, and the transmission speed is 3
84 kbps, fading is flat Rayleigh,
The Doppler frequency was 10 Hz. In addition, a period 31-M sequence was used as a unique word. From FIG. 2, FIG.
In the output of the weighting factor control unit of the conventional device, when the SIR is increased, it converges to approximately 1 (0 dB). However, according to the present invention, it is understood that the output of the weighting factor control unit 17 is proportional to the output of the SIR.

FIG. 3 is a diagram showing a simulation result of the floor error rate of the device of the present invention shown in FIG. 1 in comparison with the conventional device of FIG. The number of antenna systems was four. FIG. 3 shows a calculation example when the thermal noise can be ignored. According to the present invention, as shown in this figure, when thermal noise can be neglected, the required SIR at the point of the floor error rate of 1 × 10 ⁻³ can be improved by 1 dB, and as the SIR increases, the floor error rate can be improved. It can be seen that the difference becomes larger.

[0028]

As described above, the present invention estimates the SIR of each antenna system from the correlation value between the output signal of each demodulator and the specific pattern when a specific pattern is inserted on the transmitting side. By providing means for outputting the estimated values as weighting coefficients, there is an advantage that when there is co-channel interference, the SIR in each antenna system can be known.

Furthermore, the diversity receiving apparatus of the present invention, as compared with the conventional diversity receiving apparatus, makes the contribution of the output of each of the antenna demodulators to the signal synthesized by the diversity synthesizing section different from that of the conventional antenna. , There is an advantage that the bit error rate can be greatly improved as shown in the embodiment.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a simulation result of a weight coefficient characteristic.

FIG. 3 is a diagram showing a simulation result of a bit error rate.

FIG. 4 is a block diagram showing a conventional diversity receiving apparatus.

FIG. 5 is a diagram showing weight coefficient characteristics of a conventional diversity receiving apparatus.

Claims (1)

[Claims] 1. A plurality of receivers for receiving a reception signal via a plurality of antennas, a plurality of demodulators for demodulating respective outputs of the plurality of receivers, and a reception side in which a specific pattern is inserted on a transmission side. A plurality of correlators for respectively obtaining a correlation value between a demodulated output of each of the demodulators and the specific pattern with respect to a signal; and a sum of squares of an in-phase component and a quadrature component of each correlation value obtained by the plurality of correlators. A weighting factor output unit for outputting a weighting factor corresponding to the demodulation output of each demodulator, and a product of the product of the output of each demodulator and the weighting factor corresponding to the output of each demodulator. In a diversity receiving apparatus including a diversity combining unit and a decoder that decodes an output of the diversity combining unit, the weighting factor output unit obtains a desired signal power versus an interference signal power from each of the square sums. (SI
A diversity receiver comprising: SIR estimating means for calculating respective estimated values of R) and outputting the calculated values as the weighting coefficients.