JPH0418494B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In a mobile communication system using digital transmission technology in which each wireless device independently selects a wireless line for communication, when interference waves of the same frequency exist, the reception level The present invention relates to a detection method that allows interference waves to be detected even when fluctuations in the interference waves are large.

Conventionally, this type of system is based on the premise that a wireless transmission line, such as a microwave line, is designed so that the fluctuations in the reception level are relatively small or very slow, and the influence of interference at the same frequency is small. As a result, there are constant reception level fluctuations and each wireless device selects a wireless channel independently, so interference occurs when interfering stations with the same frequency always exist or when wireless devices with the same frequency approach each other due to movement. In some mobile communication systems, the level fluctuations of both desired waves and interference waves are random, making it impossible to stably distinguish between quality deterioration due to interference waves and deterioration due to received level fluctuations.

In order to solve these drawbacks, the present invention aims to improve the ability to detect interference at the same frequency using digital transmission technology in a wireless transmission path where the reception level constantly fluctuates greatly and there is radio wave interference at the same frequency. The drawings will be described in detail below.

FIG. 1 shows an example of the configuration of a transmitter having the same configuration as the conventional one, in which 1 is a voice encoding device, 2 is a
3 indicates a modulating device, and 3 indicates a transmitting device. To operate this, the audio signal from the transmitter 20 is encoded by the audio encoder 1 into a digital signal, and the modulator 2 creates a modulated wave. This modulated wave is converted into a carrier wave by the transmitter 3, amplified to the required transmission power, and transmitted from the antenna.
In the present invention, a configuration similar to that of a conventional transmitter is used, and since interference detection is performed in a receiver, signal processing for interference detection is not required in the transmitter.

FIG. 2 shows the configuration of a receiver according to an embodiment of the present invention, where 4 is a receiving device, 5 is a main demodulating device, 6 is a secondary demodulating device, 7 is a reception level detecting device, and 8 is a clock signal extracting device. , 9 is a decoding device, 10 is a code comparator, 11 is an error pulse detection device, and 12 is a device for determining the presence or absence of co-frequency interference.

FIG. 3 shows the relationship between the code error rate and the desired signal power to interference signal power ratio of the main demodulator 5 and the secondary demodulator 6 in FIG. Curve 14 is the characteristic of the secondary demodulator 6 with low sensitivity.

In the characteristics shown in FIG. 3, when the bit error rate is 10 ^-3 , the desired signal power to interference signal power ratio is
10 dB, and 20 dB for the secondary demodulator 6.

The operation will be explained below. Assuming that you are currently on a call and are receiving only the desired signal with a sufficient reception level,
The radio carrier wave received by the receiving device 4 has its reception level detected by the reception level detection device 7, and is demodulated into a digital signal train by the main demodulation device 5 and the secondary demodulation device 6. A clock signal extraction device 8 extracts a clock signal from the demodulated signal train from the main demodulation device 5 and supplies it to the main demodulation device 5 and the secondary demodulation device 6.
Further, the demodulated signal string from the main demodulator 5 is decoded into audio by the decoder 9, and the decoded audio signal is sent to the receiver 23. Furthermore, the signal train from the main demodulator 5 is compared with the signal train from the secondary demodulator 6 in a code comparator 10 . If both demodulators 5 and 6 demodulate without code errors, the code error pulse will not be detected by the error pulse detector 11 and no alarm will be issued. Also, the same frequency interference/disturbance determination device 12 determines that there is no interference wave based on the reception level information from the reception level detection device 7 and the code error value or alarm information of the error pulse detection device 11.

Next, consider a case where interference waves of the same frequency are generated due to the movement of another wireless device. Here, even if the level of the interference wave is considerably lower than the level of the desired wave and the reception level detected by the reception level detection device 7 hardly changes, the secondary demodulation device 6 detects the interference wave as shown in FIG. As shown in the code error rate characteristic 14, code errors occur and a correct digital signal sequence cannot be demodulated. On the other hand, the main demodulator 5 outputs a demodulated digital signal sequence with few code errors. Therefore, when both signal trains are compared in the code comparator 10, the correctly demodulated pulses are the same in both signal trains, so the error pulses are not output to the error pulse detection device 11, but the incorrectly demodulated pulses are An error pulse is output. Therefore, errors based on the code error rate characteristic 14 in FIG. 3 are detected by the error pulse detection device 11 without using a pseudo-random signal for error rate measurement. If the alarm is set to be output at a bit error rate of 10 ^-3 , the interference wave power increases and the bit errors increase, and when the error rate reaches 10 ^-3 , an alarm is sent to the determination device 12. When the determination device 12 detects that the error rate exceeds 10 ^-3 without changing the reception level, it determines that co-frequency interference has occurred. When the level of the interference wave is high, the reception level detected by the reception level detection device 7 also changes, and this change in level is sent to the interference determination device 12, which collects data to reliably determine the presence of interference waves. becomes.

FIG. 4 shows a receiver according to another embodiment of the invention.
15 is a first receiving device; 16 is an antenna that is independent of the antenna of the first receiver;
a second receiving device having a sensitivity equivalent to that of the receiver of 1;
7 is a switching device for selecting the output of the receiving device; 18;
Reference numeral 19 indicates a receiving device switching control device, and 19 indicates an interference/disturbance determination device.

This operation will be explained below. Assuming that only the desired wave is received and a call is in progress, the determination device 19 determines that if the reception level is sufficiently high as in the above example, the signal is received without error and there is no interference wave, and the determination device 19 determines that the reception device output switching device No command to switch the receiving device is issued to 17.

Here, if weak interference waves of the same frequency occur as in the above example, the reception level detected by the reception level detection device 7 will not change, a code error will be detected by the error detection device 11, and the determination device 19 will detect a code error.
The respective detection outputs are sent to the respective detection outputs. Therefore, the interference determination device 19 sends a receiving device switching command to the switching control device 18 in order to further confirm that same frequency interference has occurred, and the receiving device switching control device 18 operates the receiving device output switching device 17. to switch the receiving device. That is, receiving device 1
5 to the receiving device 16. From the time the receiving device is switched, the determining device 19 again monitors the received level and code error using the signals from the received level detecting device 7 and the error pulse detecting device 11. Repeat this operation several times at appropriate time intervals, and if similar reception levels and code errors are detected, the judgment device 1
9 determines that same frequency interference has occurred.

As explained above, by constantly detecting the reception level and using a demodulator with low sensitivity in addition to the main demodulator, it is possible to easily detect code errors without using pseudo-random signals. This has the advantage that interference can be detected efficiently. Further, there is an advantage that there is no need for the transmitter and the receiver to insert a pseudorandom signal into the audio digital signal for detecting code errors, or to perform digital signal processing operations for separating the signal.

Furthermore, there is an advantage that interference can be determined more reliably by switching the antenna and the receiving device when interference occurs.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a transmitter used in an embodiment of the present invention having the same configuration as the conventional one, FIG. 2 is a diagram showing the configuration of a receiver in an embodiment of the present invention, and FIG. FIG. 2 is a diagram showing the code error rate characteristics of the demodulator used in the demodulator used in the desired signal power to interference signal power ratio, and FIG. 4 is a diagram showing the configuration of a receiver according to another embodiment of the present invention. 1... Audio encoding device, 2... Modulation device, 3...
...Transmitter, 4...Receiver, 5...Main demodulator, 6...Secondary demodulator, 7...Reception level detector, 8...Clock signal extractor, 9...
Audio decoding device, 10... code comparator, 11...
Error pulse detection device, 12... Co-frequency interference/disturbance determination device, 13... Code error rate characteristic for desired wave power to interference wave power ratio of main demodulator, 14...
. . . code error rate characteristic of the secondary demodulator for desired signal power to interference signal power ratio, 15 . . . first receiving device,
16... Second receiving device, 17... Receiving device output switching device, 18... Receiving device switching control device, 19...
...Same frequency interference/disturbance determination device, 20...Telephone transmitter,
21... Transmitting antenna, 22, 24, 25... Receiving antenna, 23... Receiver.

Claims (1)

[Scope of Claims] 1. In a wireless communication system having a base station wireless device connected to a subscriber line and a mobile station wireless device communicating via a wireless line, between the base station wireless device and the mobile station wireless device Interference from other wireless devices on the same frequency occurs when any one wireless line is selected from a group of multiple wireless lines using digital transmission technology and is in the state of transmitting and receiving, independently of other wireless devices. In order to detect interference, the receivers of the base station radio equipment and the mobile station radio equipment are provided with means for detecting the reception level and a secondary demodulation device with low sensitivity in parallel with the main demodulation device, and these devices are simultaneously operated. and a means for detecting a code error in the digital signal by comparing the demodulated digital signals of the main demodulator and the secondary demodulator, and by constantly monitoring the reception level and the code error of the demodulated signal. , an interference detection method characterized by detecting the occurrence of interference on the same frequency from other wireless devices. 2. A plurality of receiving antennas and a plurality of receiving devices each connected to each of the plurality of receiving antennas are provided, and each output of the plurality of receiving devices is selectively switched, and the presence or absence of interference waves is checked each time the switching is performed. 2. The interference detection method according to claim 1, wherein the presence of interference waves is determined more reliably than in the case of one receiving antenna and one receiving device.