JPH02189042A - Diversity reception system - Google Patents

Abstract

PURPOSE:To surely decide which antenna system has the best reception state with a simple constitution independently of an external factor by monitoring an error number itself depending on an error detection code added in advance to a transmission data in a digital mobile object communication. CONSTITUTION:An error number at every system is fetched by an error number comparator 16, where a signal from which antenna has the least error number is compared and calculated, and the information is outputted to a switching control circuit 18. A demodulated data except the error detection code being the output of each error detection section 14 is also fed to a switching circuit 20 and the switching circuit 20 selects the demodulated data with the least error number from the demodulated data sent from each error detection section 14 based on a command signal from the switching control circuit 18 and the selected data is outputted as the demodulated data after diversity. Thus, the received signal from which antenna is the best is quickly and surely recognized independently of other external factor such as fading.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diversity reception system, and in particular to digital mobile communications with spatial diversity.

[Conventional technology] Telephone calls from moving objects such as cars and ships, or from moving people,
BACKGROUND ART Mobile communications that handle data and the like are well known, and have become more and more familiar to society in recent years as the field of radio wave use expands and advanced radio frequency utilization technology develops.

In mobile communications as well, there are demands for sophistication, diversification, higher quality, effective use of frequencies, economicization, etc.
The trend toward digitalization is increasing.

However, propagation characteristics in digital mobile communications, especially land mobile communications, exhibit characteristics of multiple wave propagation paths due to reflected waves and scattered waves from surrounding buildings and terrain. That is, since it is a mobile station, a large number of waves with different propagation paths arrive and interfere with each other, resulting in complex standing waves.

At this time, there is a problem in that the comprehensive line and phase of the mobile station received wave fluctuate randomly, resulting in so-called fading, in which the field strength of the radiated radio wave changes over time.

Furthermore, as a result of the formation of multiple wave propagation paths, that is, multipaths, data signals in transmission waves are often dropped, which often leads to code errors in digital communications.

The most effective technique for reducing the negative effects of fading and multipath is diversity reception. If two or more received waves whose fading fluctuations have a small correlation with each other are used, there is a high probability that one of the envelopes will not fall, so the error rate can be suppressed.

Spatial diversity is well known as a reception method for obtaining fading waves whose fluctuations are independent of each other.

Spatial diversity is a method of installing antennas that are optically separated spatially to obtain received waves with a small correlation between fluctuations. In general, the effect can be obtained by separating the wavelength by more than half the wavelength.
Because of its simple configuration, it is most commonly used unless there is a limit to the size of the device.

In this type of spatial diversity, when it comes to selecting which received signal from among a plurality of antennas is to be adopted, usually the branch (antenna) with the highest reception level is simply selected.

However, under multiple wave propagation environments such as urban areas,
Even if the reception level is high, the code error rate may increase due to multiple wave distortion.

For this reason, switching by monitoring the reception level is undeniably difficult in terms of reliability.

In order to deal with these inconveniences, we
No. 35 adopts a method in which when the average reception level is lower than a certain value, a branch with a high instantaneous reception level is selected, and when it is higher, a branch with the least delay distortion is selected.

[Problems to be Solved by the Invention] However, this system also has the same disadvantages as the above-described method in which branches are selected based only on the reception level.

That is, just as a branch with a higher reception level does not necessarily have a lower error rate, a branch with less delay distortion does not necessarily have a lower error rate. In addition, this device requires a large number of components such as a reception level detection circuit, delay distortion detection circuit, low-pass filter, bypass filter, or comparison circuit, which increases the circuit scale and makes the control complicated. There is a drawback that there is no

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a diversity receiving system that is simple in configuration and can realize reception with a low error rate.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a diversity reception system that performs reception under optimal conditions by combining or switching the outputs of a plurality of antennas arranged at predetermined intervals. A plurality of demodulators are provided corresponding to each of the antennas and demodulate the received signal from each of the antennas, and detect errors in the demodulated data output from each of the demodulators based on error detection codes contained therein. a plurality of error detection units for detecting errors; and an error number comparison circuit for mutually comparing the number of errors for each antenna obtained in each of the error detection units; It is characterized by the fact that it is adopted.

[Operation] In the present invention configured as described above, after the received signals from a plurality of antennas are demodulated, the number of errors thereof is directly detected by the error detection section provided for each antenna, and the number of errors is detected by the error number comparison circuit. Then, the received data from the antenna with the least number of errors is adopted.

Therefore, according to the present invention, since the antenna with the best reception condition is selected for the error detection code regardless of the reception level, it is possible to effectively avoid deterioration of code error rate characteristics due to fading.

Furthermore, in the present invention, it is possible to determine which antenna is in the best receiving condition using only the error detection section corresponding to each antenna and its comparison circuit, and there is no need for a complicated and expensive circuit configuration.

[Example] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a block diagram of the overall configuration of a diversity receiving system according to the present invention.

n arranged with an interval of λ/2 (λ: wavelength) from each other
A system antenna 10 is disposed on a vehicle, ship, or other moving object. This interval λ/2 means a necessary and sufficient distance to perform spatial diversity reception of modulated electromagnetic waves containing error detection codes.

The signals received by each antenna 10 are supplied to the corresponding demodulator 12, where they are subjected to detection using either synchronization, delay, or frequency.
Obtain predetermined demodulated data.

At this demodulated data stage, the error detection code is still included in the demodulated data, and this is similarly supplied to the error detection unit 14 provided corresponding to each antenna system, so that errors occurring during the transmission and reception process can be detected. The number will be known.

The number of errors for each system is calculated by the error number comparison circuit 16.
Here, the signal from which antenna has the smallest number of errors is compared and calculated, and this information is output to the switching control circuit 18.

The demodulated data excluding the error detection code, which is the output of each error detection section 14, is also supplied to the switching circuit 20, and the switching circuit 20 receives the data sent from each error detection section 14 in response to a command signal from the switching control circuit 18. The demodulated data with the least number of errors is selected from the received demodulated data and outputted as demodulated data after diversity.

The characteristic feature of the present invention is that instead of controlling the phase amount using the monitored error rate as a medium or targeting the reception level or the high and low levels of delay distortion as in the past, The present invention is configured to directly determine the quality of the reception state of the received signal based on the error detection code itself and the magnitude of the number of errors.

This makes it possible to quickly and reliably determine which antenna receives the best quality signal without being affected by facing or other external factors using a simple configuration.

Now, if a code with a code length n (bits), information bits k (bits), and check bits n-k (bits) is used as an error detection code, the number of errors in each system is detected for every n bits, and the most This means switching to a system with fewer errors.

For example, consider a cyclic code with code length n-20 given by G (x)mx''+x'2+x' +1 as the generator polynomial G (x).

This error detection code can detect any random error of 3 or less and any burst error of length 16 or less.

Therefore, excellent transmission quality can be obtained by comparing the number of errors every 20 bits and selecting the demodulated data branch with the smallest number of errors.

According to the device of the present invention, only the number of errors needs to be monitored, and the best quality received signal can be obtained by simply switching to the branch with fewer errors, making control extremely easy. Simplified.

Additionally, there is no need to monitor reception levels, delay distortion, etc.
The control circuit can be composed only of digital circuits without spanning analog circuits and digital circuits, and manufacturing of the control circuit is greatly facilitated.

[Effects of the Invention] As explained above, according to the system of the present invention, in digital mobile communications, errors are detected using error detection codes added in advance to transmitted data, rather than detecting reception levels and delay distortion. Since it monitors the number itself, it is possible to reliably determine which antenna system has the best reception condition without being influenced by external factors with a simple configuration, and can significantly improve reception quality. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of the system of the present invention. 10... Antenna 12... Demodulator 14... Error detector 16... Error number comparison circuit 18... Switching control circuit 20... Switching circuit

Claims (1)

[Claims] (1) In a diversity reception system that performs reception under optimal conditions by combining or switching the outputs of a plurality of antennas arranged at predetermined intervals, a reception signal from each antenna is provided corresponding to each of the antennas. a plurality of demodulation units that demodulate the demodulated data; a plurality of error detection units that detect errors in the demodulated data output from each of the demodulation units based on error detection codes included therein; an error number comparison circuit that mutually compares the number of errors for each antenna, and employs demodulated data from the antenna with the smallest number of errors and switches between antennas.