JPH0219034A - Diversity reception method - Google Patents

Abstract

PURPOSE:To improve transmission quality by measuring the reception level with plural frequencies and selecting a branch with the excellent frequency characteristic by using the result of measurement. CONSTITUTION:Level measuring circuits 5, 6 of receivers 3, 4 measure respectively reception levers R1, R0, R2 at a designated frequency in the reception band and the result is given to a branch selection control circuit 7. Moreover, the output of the receivers 3, 4 is led to detectors 8, 9 where it is detected respectively, the detection output is led to a branch selection circuit 10, which selects the branch based on the output of the branch selection control circuit 7. The output of the branch selection circuit 10 is led to a clock recovery circuit 11 and an identification deciding circuit 12, and the recovered clock obtained by the clock recovery circuit 11 is given to the identification deciding circuit 12, identification and decision are applied in the identification timing and a demodulation data is outputted to a demodulation terminal 13. Thus, a detection output with less waveform distortion is obtained at the receiver and the transmission quality of a high speed digital signal is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a reception method that ensures good transmission quality in wireless communication between a wireless base station and a mobile station.

(Prior Art) In land mobile communications, as a mobile station moves, received signals undergo fading due to multipath propagation of radio waves, resulting in significant deterioration in transmission quality. Application of diversity reception technology is effective as a countermeasure against this fading, and equal gain combining methods, selection methods, etc. have been proposed, and the effects of application are being studied. Conventional diversity reception methods mainly have a bit rate of several kilobytes where frequency selective fading can be ignored.
It was intended for transmission at speeds of about 1/2 seconds or less.

On the other hand, when transmitting high bit rates of several tens of kilobytes or more, it is necessary to consider the influence of propagation delay time dispersion.
That is, if the delay time difference between arriving waves via multiple propagation paths from the base station to the mobile station is larger than the data repetition period, frequency selective fading occurs and sufficient improvement effects cannot be obtained.

Figure 4 shows an example of the configuration of the conventional Diversina reception method, 1 and 2.
is a receiving antenna, 3 and 4 are receivers, 5 and 6 are level measurement circuits, 7 is a branch selection control circuit, 8 and 9 are detectors, 1
0 is a branch selection circuit, 11 is a clock recovery circuit, 12
Reference numeral 13 indicates an identification determination circuit, and 13 indicates an output terminal.

In the conventional two-branch detection-post-selection diversity reception method as shown in Fig. 4, the reception level (R
o) Select the detection output of the large branch. Figure 3 (
A) shows how branches are selected by the 5wltch and 5tay algorithm.

This means that the branch indicated by the bold line is selected.

(Problem to be Solved by the Invention) In this case, if each branch has distortion in frequency characteristics due to propagation delay time dispersion as shown in FIGS. 5(b) and (c), the central reception Even if a branch with a high reception level in the frequency (branch 1 having the frequency characteristic of (b) in this case) is selected, waveform distortion will occur in the detection output and the transmission quality will deteriorate.

The present invention aims to improve this point.

(Means for Solving the Problems) A feature of the present invention for achieving the above-mentioned object is that in a diversina reception method that uses a plurality of antennas and receivers and selects and outputs one of them, Measure the reception levels for multiple frequencies within the reception band, and if the ratio of the measured levels in all branches is within a predetermined value range, select the branch with the highest reception level relative to the center frequency of the reception band. and when the ratio of the levels in some branches is within the range and the ratio of the levels in other branches is outside the range, the ratio of the levels in the branches whose ratio is within the range is selects the branch with the highest reception level relative to the center frequency of the reception band, and when the ratio of the levels in all branches is outside the range, selects the branch with the ratio of levels closest to the range. It's in the reception method.

(Operation) In the present invention, as described above, the reception level is measured at a plurality of frequencies, and the measurement results are used to select a branch with good 0 frequency characteristics. Therefore, sufficient improvement effects can be obtained even in the case of high-speed lines, and the object of the present invention can be achieved.

(Embodiment) FIG. 1 shows an embodiment of the present invention for post-detection selection diversity with a two-branch configuration.The basic configuration is the same as the conventional system, and the same reference numbers as in FIG. 1
In the figure, for each branch (branch 1.branch 2),
This method differs from the conventional method in that reception levels (R, , R, , R) are constantly measured at multiple frequencies (f2°fa=ft). here.

A case will be described in which measurement is performed at three frequencies within the reception band. Signals received by receiving antennas 1 and 2 are input to receivers 3 and 4, respectively.

In the receivers 3 and 4, the level measurement circuits 5 and 6 measure the reception level at a specified frequency within the reception band (here, the center reception frequency f, f□ higher than fo by Δf, and frequency fi lower by Δf). R□.

Ro and R3 are each measured and the results are input to the branch selection control circuit 7. Further, the outputs of the receiver 3.4 are led to and detected by detectors s8 and 9, respectively. The detection output is guided to a branch selection circuit 10. At step 10, a branch is selected based on the output of a branch selection control circuit 7 which operates according to an algorithm as will be described later. The output of the branch selection circuit 10 is sent to the clock recovery circuit 11. and is led to the identification determination circuit 12. The regenerated clock obtained by the clock regeneration circuit 11 is input to the identification judgment circuit 12, which performs identification judgment at the identification timing, and outputs the signal to the demodulation terminal 1.
3, the demodulated data is output.

FIG. 2 shows an example of the configuration of the level measuring circuit (5, 6). The signal from the high frequency stage or intermediate frequency stage of the receiver input to the level measuring circuit input terminal 21 is input to band pass filters 22, 23 and 24 whose center frequency is a predetermined frequency within the receiving band (here, falfttfz). Ru. The output of each bandpass filter is a log amplifier 25, 2, respectively.
6.27, the voltage corresponding to the reception level at each frequency is output to the level measurement circuit output terminals 28, 29.30.
Output each. For example, if the output voltage of the filter at frequency f is Et, the output voltage R1 of the level measuring circuit output terminal is given by log(Et).

An example of a branch selection algorithm in the branch selection control circuit 7 is shown below.

(1) In each branch, the reception level is measured at the center reception frequency f0 and at a frequency f2 higher than fo by Δf and lower by Δf. Let the measured values be R6, R1 and R2, respectively, and the level ratios Ri/RO and Rz/
Calculate Ra.

(2) When the deviation of the level ratio R, R, /R, from the specified value determined from the frequency spectrum characteristics of the transmitted signal is within a predetermined range for both branches, Ro is large. Select a branch.

(3) If the deviation of the value of the level ratio Rt/Ra=R2/Ro from a specified value determined from the frequency spectrum characteristics of the transmitted signal is within the specified value for only one branch, select that branch.

(4) When the deviation of the value of the level ratio R/R0,R,/R, from the specified value determined from the frequency spectrum characteristics of the transmitted signal is outside the predetermined range for both branches, R1/R, , R, /R0 is close to the specified value.

FIG. 3(b) shows an example of branch selection according to the above algorithm. (1) is the reception level RO at fo, (2
) and (3) indicate the deviation from the reference value RI1/R,=1 for the ratio of the reception level R2 and Ro at the reception level R1 and f2 at fl, respectively.

This means that the branch indicated by the thick line in (1) is selected. The specified value of the level ratio varies depending on the filtering format and modulation method on the transmitting side.

In Fig. 3(b), in section (1), R2/R of branch 1
, is outside the allowable range, and branch 2 has R2/R- and R□/
Since R, are both within the permissible range, branch (2) is selected. In intervals (2) and (3), the ratio of all levels is within the allowable range, so the one with the higher level (Ro) is selected (branch 2 in interval (2) and branch 1 in interval (3))
In interval 0 (4), R1/Ro of branch 1 is out of range, so branch 2 is selected. Interval (5), (
6) and (7), the ratio of all levels is within the allowable range, so the branch with the higher level is selected (interval (5)
branch 1 in interval (6), branch 2 in interval (7), branch 1 in interval (8), R of branch 1 in interval (8), /R
In interval 0 (9) where branch 2 is selected because o is outside the allowable range, R2/Ro of branch 1 and branch 2
Although both Rz/R- of branch 1 are outside the allowable range, branch 1 is selected because R1/RO of branch 1 is closer to the allowable range.

In sections (10) and (11), all the level ratios are within the allowable range, so the one with the higher level of Ro is selected.

The above algorithm basically selects a branch with good frequency characteristics, and a receiver that operates based on this algorithm can obtain a detection output with little waveform distortion, so it is suitable for the transmission of high-speed digital signals where delay time dispersion is a problem. Quality can be improved.

In this embodiment, the case where the present invention is applied to mobile communication has been described, but it is also possible to apply the present invention to a general wireless communication system using a fixed communication list. Further, by increasing the number of reception level measurement points, it is expected that the characteristics of the negative layer will be improved. Furthermore, the conventional 5w1tch and 5 with fixed switching levels
A selection method using a combination of algorithms such as tay, 5wltch and examins may also be considered.

(Effects of the Invention) As described above, according to the present invention, good transmission quality can be ensured even when distortion of frequency characteristics due to propagation delay time dispersion exists.

[Brief explanation of the drawing]

Fig. 1 shows an example of the Diversina reception method according to the present invention, Fig. 2 shows an example of the configuration of a level measurement circuit, Fig. 3 shows the timing of branch selection in the conventional method and the present method, and Fig. 4 shows the conventional method. FIG. 5 is a diagram showing the frequency characteristics of the received signal. 1.2... receiving antenna, 3, 4... receiver, 5.
6...Level measurement circuit. 7... Branch selection control circuit, 8.9... Detector, 10... Branch selection circuit, 11... Clock regeneration circuit, 12... Identification judgment circuit, 13... Demodulation output terminal, 21...Level measurement circuit input, 22.23.24...Band pass filter. 25.26.27...Log amplifier, 2g, 29.30...Level output terminal.

Claims (1)

[Claims] In a diversity reception method that uses a plurality of antennas and receivers and selects and outputs one of them, the reception level for a plurality of frequencies within the reception band is measured for each receiver, and all When the ratio of the measured levels in the branches is within a predetermined value range, select the branch with the highest reception level with respect to the center frequency of the reception band, and select the branch whose level ratio in some branches is within the range. and when the ratio of the levels in other branches is outside the range, select the branch with the highest reception level with respect to the center frequency of the reception band among the branches whose level ratios are within the range, A diversity reception method characterized in that when the level ratios of all branches are outside the range, the branch whose level ratios are closest to the range is selected.