JPH09214409A - Diversity method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the time required for switching processing in the case of diversity reception using lots of branches through the use of a single reception circuit. SOLUTION: In the diversity method executed by using plural antenna branches, a learning function of a prescribed length for each frame is provided to measure reception quality of each of antennas 20a-20l and a branch providing excellent reception quality for the learning period is selected in advance as an advance branch object among all the branches. For other periods than the learning period of each frame, the one selected branch is used to conduct actual communication and when the reception quality of the branch used at present after a diversity output is deteriorated more than a prescribed quality, a branch among the branch objects is selected for communication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to diversity communication using a plurality of antenna branches to improve communication quality.

[0002]

2. Description of the Related Art Conventionally, many types of diversity have been put into practical use, which have a branch number of about 2 or 3. When the number of branches is small in this way, it is easy to successively measure the quality of all branches and switch or combine the branches.

However, in order to ensure stable communication quality even in a propagation path where multiple reflections are likely to occur,
It is effective to use an antenna with a narrow beam, and it is inevitable that a large number of branches are provided in order to widen the coverage range of the arrival direction of radio waves. Therefore, many processes are required to select a branch to be used for communication from many branches.

For example, "mobile radio reception system" (Japanese Patent Laid-Open No. Sho 5
6-60123) discloses an antenna switching algorithm for a threshold diversity reception system in which all branches are circulated until a branch satisfying the threshold is found.

According to this method, since a branch in use is deteriorated and a branch needs to be switched, the branches are sequentially switched to search for a usable branch, and therefore communication cannot be performed until the switching is completed. It had the disadvantage of increasing the time.

Also, "angle diversity receiver"
(Japanese Patent Laid-Open No. 60-223336) describes an antenna switching algorithm of an angle diversity receiving device.
Disclosed is a method of preparing for the deterioration of the receiving circuit side in use by using one receiving circuit and circulating all the branches connected to the receiving circuit not in use until a branch satisfying the threshold value is found. doing.

According to this method, since the best receiving system is always learned by the receiving system other than the active system, the disadvantage that the incommunicable time becomes long as in the above system is improved. However, there is a drawback that the receiving system is duplicated and the device is complicated and expensive.

On the other hand, "High bit rate communication system for overcoming multipath" (Japanese Patent Laid-Open No. 2-79628).
For the antenna selection algorithm between the radiotelephone and the node using the 6-sector antennas, the quality is sequentially measured for 36 combinations of 6 × 6, the necessity of the route change is judged, and if necessary, A method for switching to the best antenna combination is disclosed.

In this method, the frame is always received while learning is performed while changing the combination of the antennas, and the learning is controlled so that the combination of the antennas always has a good quality. Even if it deteriorates, at least the learning of the next 6 frames must be completed in order to judge the necessity of the route change, and there is a drawback that the switching becomes slow.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a diversity method that solves the drawback that switching processing takes time when performing diversity reception using a large number of branches using a single receiving circuit. And

[0011]

SUMMARY OF THE INVENTION The present invention provides a pre-branch candidate group for selecting a limited number of good branches in advance from a large number of branches by learning performed for each learning period provided in a frame. The most main feature is to have a switching means or a synthesizing means for selecting or synthesizing a branch from the pre-branch candidate group or synthesizing and outputting. It differs from the conventional technique in that the number of branches is limited in advance by learning.

Since the present invention is provided with a pre-branch candidate group selecting means, it is possible to select a limited number of good branches from a large number of branches by learning.
Therefore, the substantial number of branches can be narrowed down to about 2 or 3 as in the conventional case, and the switching time after detecting the deterioration of quality can be shortened.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows an antenna system arranged to cover 360 degrees in a horizontal plane. FIG. 2 (a) is composed of 3 branches and FIG. 2 (b) is composed of 12 branches. As the number of branches increases, the beam of each antenna can be narrowed down, and multiple reflected waves and irregular reflection can be suppressed, so that communication quality is improved. On the other hand, since the number of options increases, the processing required to select one branch increases.

FIG. 1 shows an embodiment of a diversity receiving system of the present invention. 20a to 20l are individual antennas, 21 is a branch changeover switch, and 22 is a TDD switch (a switch for switching transmission and reception in time division). ), 23 is a receiver, 24 is a signal strength detection circuit, 25
Is a code error measuring circuit, 26 is a branch changeover switch control circuit, and 27 is a transmitter.

The branch changeover switch 21 is 20a.
It is possible to connect any one branch from 20 to 20 l to 22, and the reception output is input to the receiver 23 via the TDD switch 22. In the receiver 23, the received signal is frame-synchronized, and the signal (learning period) of a required portion of the frame is branched and output to the signal strength detection circuit 24. The signal strength detection circuit 24 inputs the signal branched and output from the receiver 23 and detects the signal strength of the received signal. On the other hand, the code error measuring circuit 25 takes in the digital data series from the receiver 23 and measures the number of code errors. It is easily understood by those skilled in the art that in the reception system using FEC (forward error control), the error correction pulse of the FEC decoder is used for an equivalent purpose instead of the code error detection circuit 25. is there.

The measurement results of the signal strength detection circuit 24 and the code error measurement circuit 25 are input to the control circuit 26, and the control circuit 26 digitizes the quality of the branch selecting both pieces of information by an appropriate function. Further, the control circuit 26 ranks individual branches based on the evaluation result and selects a limited number of good branches.

The deterioration of the quality of the branch used in the actual data communication by the receiver 23 is detected by the control circuit 26 by the information of the signal strength detection circuit 24 and the code error measuring circuit 25, and is described above. It is selected from the branch candidate group selected in advance, and is switched by controlling the switch 21.

In this embodiment, TD with 12 branches is used.
Although an example of the D transmitter / receiver is shown, the number of branches can be set to an arbitrary number, and the TDD switch 22 and the transmitter 2 can be set.
7 is not necessarily a requirement of the invention.

FIG. 3 shows an embodiment of an algorithm for selecting a prior branch candidate group according to the present invention. In this embodiment,
For each frame, a bit string for antenna learning is transmitted from the transmitting side at an appropriate position in the frame, and a certain number of frames are received to measure the quality of each branch. The quality can be a received signal strength, a code error number or code error rate, a waveform distortion amount, or at least one of these functions. In blocks 31, 32 and 33,
In the switching of the learning period, a frame number counter, a signal strength cumulative value for adding the signal strength of each time corresponding to each branch, and a code error cumulative for adding the number of code errors corresponding to each branch Reset the value.

After the initialization is completed, the block 34 receives the bit string for antenna learning described above, and the block 3
The signal strength is measured at 5 and 36 and added to the cumulative value. Further, the code error is measured in blocks 37 and 38 and similarly added to the cumulative value.

The processing of blocks 34-38 is repeated while cycling through the branches at block 312 until a fixed number of frames have been received. After a fixed number of frames have been received, at block 310 the individual branches are ranked. The ranking is determined by an appropriate functional calculation of the signal strength cumulative value and the code error cumulative value of each branch. In block 311, receiving the result of 310,
Select a limited number of branches from the higher ranked branches. After the branch selection, the next learning cycle is started and the cycle is repeated to block 31.

FIG. 4 shows an embodiment of the branch switching algorithm using the branches of the pre-branch candidate group.
In this embodiment, an example is shown in which three branches are selected as a pre-branch candidate group. Blocks 42, 44 and 46 detect the degradation of the received signal from the branch currently in use and determine the need to switch. If the switching condition is satisfied, the branch is switched to the next branch candidate. In this embodiment, as shown in blocks 41, 43 and 45, a method is shown in which the branch candidates 1, 2 and 3 are sequentially switched and patrolled for each switching activation condition.

As shown above, compared with the conventional technique,
The receiving device remains simple, and even in a receiving system having a large number of branches, it is possible to quickly detect deterioration of the communication path and switch the branches.

In the learning period for each frame, all the branches may be measured in the learning period of one frame, or only some of the branches may be learned and all the branches may be measured in a plurality of frames.

[0025]

As described above, since it is possible to select a limited number of branches in advance from a large number of branches by learning, it is possible to multiplex by using a receiving system composed of a large number of narrow beam antennas. The effect of the reflected wave is reduced, and it is possible to cope with the rapid fluctuation of the propagation path, which has the effect of improving the communication quality.

[Brief description of drawings]

FIG. 1 shows an embodiment of a diversity receiver according to the present invention.

FIG. 2 shows an embodiment of an antenna system.

FIG. 3 shows an example of an algorithm for selecting a prior branch candidate group.

FIG. 4 shows an example of a branch switching algorithm.

[Explanation of symbols]

 20a-20l Individual antenna 21 Branch changeover switch 22 TDD switch 23 Receiver 24 Signal strength detection circuit 25 Code error measurement circuit 26 Branch changeover switch control circuit 27 Transmitter

Claims (3)

[Claims] 1. In a diversity method implemented by using a plurality of antenna branches, a reception period of a predetermined length is provided for each frame to measure the reception quality of each antenna, and the reception quality during the learning period is selected from all the branches. Is selected as a pre-branch candidate in advance, and during the period other than the learning period of each frame, actual communication is performed using one selected branch, and the branch currently in use after diversity output is selected. A diversity method, wherein when the reception quality deteriorates below a predetermined value, one branch of the branch candidates is switched to perform communication. 2. The diversity method according to claim 1, wherein the learning period is periodically repeated,
The pre-branch candidate group preselected during the learning period is
A diversity method, which is updated every learning cycle and is effective until learning in the next learning period is completed. 3. The diversity method according to claim 1, wherein the quality of each antenna branch is determined by the received signal strength, the number of code errors or the code error rate during the learning period,
A diversity method characterized by being given by a waveform distortion amount or a function of at least one of these physical amounts.