JPS58150344A - Interference detecting system - Google Patents

Abstract

PURPOSE:To facilitate the detection of a code error without using a pseudo random signal and to detect with high efficiency the interference disturbance of the same frequency under calling, by detecting the receiving level at all times and, at the same time, by using a demodulator having a low level sensitivity in addition to a primary demodulator. CONSTITUTION:For a radio carrier wave received at a receiver 4, the receiving level is detected by a receiving level detector 7. At the same time, the radio carrier wave is demodulated into a digital signal train by a primary demodulator 5 and a secondary demodulator 6. The clock signal is extracted out of the signal train demodulated by the modulator 5 through a clock signal extracting device 8 and supplied to the demodulators 5 and 6. The signal train demodulated by the demodulator 5 is decoded to voices by a decoder 9 and sent to a telephone receiver 23. Furthermore, the signal train is compared with the signal train given from the demodulator 6 at a code comparator 10. No alarm is generated from an error pulse detector 11 if the demodulators 5 and 6 perform demodulation with no code error.

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, if interference waves of the same frequency exist, the reception The present invention relates to a detection method capable of detecting interference waves even if the level fluctuations are large.

Conventionally, this type of system uses a wireless transmission line, such as a microwave line, installed in such a way that the fluctuations in the received level are relatively small or very slow, and the influence of interference at the same frequency is small. Because the reception level is constantly fluctuating and each wireless device selects a wireless channel independently, interference can occur due to the constant presence of interfering stations with the same frequency or the proximity of wireless devices with the same frequency due to movement. In mobile communication systems in which noise may occur, level fluctuations of both desired waves and interference waves are random, and there is a drawback that it is not possible 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 waves 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 modulation device, and 3 is a transmitter.
indicates a transmitting device. To operate this, an audio signal from a transmitter 20 is encoded into a digital signal by an audio encoder 1, and a modulated wave is generated by a modulator 2. Although this modulated wave is converted into a carrier wave by the transmitter 3, amplified to the required transmission power, and transmitted from the antenna, the present invention uses the same configuration as a conventional transmitter.
Since interference detection is performed at the receiver, there is no need for signal processing for interference detection at the transmitter.

FIG. 2 shows the configuration of a receiver according to an embodiment of the present invention, with four
is a receiving device, 6 is a main demodulation device, 6 is a secondary demodulation device, 7 is a reception level detection device, 8 is a clock signal extraction device, 9 is a decoding device, 10 is a code comparator, and 11 is a false 9 pulse detection device , 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 16 in FIG. 2, and the curve 13 shows the main demodulator core characteristic; Curve 14 is the characteristic of the secondary demodulator 6 with low sensitivity.

In the characteristics shown in FIG. 3, the ratio of desired signal power to interference signal power when the bit error rate is 10 is l OdB in the main demodulator 5.
, 20(lit) in the secondary demodulator 6.

The operation will be explained below. Assuming that only desired waves with a sufficient reception level are being received and a call is being made, the reception level of the radio carrier wave received by the reception device 4 is detected by the reception level detection device 7, and the reception level is detected by the main demodulation device 5. and is demodulated into a digital signal train by the secondary demodulator 6. A clock signal is extracted from the demodulated signal train from the primary demodulator 5 by the click signal extractor W8, and the clock signal is then demodulated by the primary demodulator 5 and the secondary demodulator. It is supplied to the device 6. Further, the tm-coded signal string from the main demodulator 6 is decoded into audio by the decoder 9, and the decoded audio signal is sent to the receiver 23. Further, the signal train from the main post-modulator 5 is compared with the signal train from the secondary demodulator 6 in a code comparator 10 . If there is no code error and the signal is being adjusted by the rain adjustment device 5.6, the error pulse detection device 11 will not detect the code error pulse, and no alarm will be generated. Further, the same frequency interference/disturbance determining device i12 uses the received level information from the received level detecting device 7 and the lit pulse detecting device 11.
It is determined that there is no interference wave from the sign error value or alarm information.

Next, consider a case where interference waves of the same frequency are generated due to the movement of another wireless device. Here, the level of the interference wave is considerably lower than the level of the desired wave, and the reception level detection device 7
1 even if the reception level detected by
When interference waves occur in the secondary post-adjustment device 6, a code error occurs as shown in the code error rate characteristic 14 in FIG. 3, and a correct digital signal sequence cannot be demodulated. On the other hand, the main demodulator 6 outputs a demodulated digital signal sequence with few code errors. Therefore, both 1M code sequences are compared in the code comparator 10. Since the correctly demodulated pulses are the same in both signal sequences, the error pulses are detected by the error pulse detection device 10.
1, but a reflected pulse is output for the erroneously demodulated Nogle. Therefore, without using a pseudo-random signal for measuring the error rate, the code error rate characteristic 14 in Fig. 3 is output.
An error based on this will be detected by the error detection device 11. If the alarm is set to be output at a code ttb rate of 1Ω-1, the interference wave power will increase, the code error will increase, and when the S ridge rate reaches 10-3, an alarm will be sent to the determination device 12. When the determination device 12 detects that the error rate exceeds 10 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 also changes, and this change in level is detected by the interference determination device 1.
2, and serves as data for reliably determining the presence of interference waves.

FIG. 4 shows a receiver according to another embodiment of the invention.

15 is a first receiving device, 16 is a second receiving device which has an antenna independent of the antenna of the first receiver and has the same sensitivity as the first receiver, and 17 is an output of the receiving device. A switching device for selection, 18 a receiving device switching control device, and 19 an interference determining 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 example described above, there is no error and that there is no interference wave, and the determination device 19 determines that the reception device outputs No command to switch the receiving device is issued to the switching device 17.

If weak interference waves of the same frequency are generated in the same way as in the above example, the passive level detected by the reception level detection ha7 will not change, and code reflection will be detected by the overcast detection device 11, and the determination device 19 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, the receiving device 15 is also switched to the receiving device 16. From the moment when this receiving device is switched, the determining device 19 receives the signal again.
The signal level and code reflection are monitored using signals from the reception level detection device 7 and the error pulse detection device 11. This operation is repeated several times at appropriate time intervals, and if similar reception levels and code errors are detected, the determination device 19 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 reflections without using pseudo-random signals. It has the advantage of being able to efficiently detect interference and disturbances. Also, the transmitter and receiver have the ability to insert or separate pseudo-random signals into the audio digital signal to detect code errors. There are advantages that do not require.

Furthermore, there is an advantage that interference can be determined more reliably by switching the antenna and μ 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, which has the same configuration as the conventional one, Fig. 2 is a diagram showing 11 configurations of a receiver in an embodiment of the invention, and Fig. 3 2 is a diagram showing the code error rate characteristic of the demodulator used in FIG. 2 with respect to 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... Variation device, 3... Transmitting device, 4... Receiving device 4.5......・Main demodulator, 6...
Subordinate demodulator, 7... Reception level detection device,
8... Clock signal extraction device, 9...
Audio decoding device, lO... code comparator, engineering 1.
. . . Yield pulse detection device, 12 . . . Same frequency interference determination device, 13 . . . . Code error rate characteristic for desired wave power to interference wave power ratio of secondary demodulator, 15 . . . 1st receiving device, 16 . . . 2nd receiving device, 17・・・
... Receiving device output switching device 118... Receiving device switching control device, 19... Same frequency interference and disturbance determination device, 20... Transmitter, 21...・・・・・・
Transmitting antenna, 221.24.25...Receiving antenna, 23...Receiver agent Patent attorney Takashi Honma

Claims (2)

[Claims] (1) In a wireless communication system that has a base station wireless device connected to a subscriber line and a mobile station wireless device that communicates via a wireless line, digital transmission technology is used between the base station wireless device and the mobile station wireless device. When any one wireless line is selected from a group of wireless lines with the number of TIs used and is in a transmitting/receiving state independently of other wireless devices, interference on the same frequency from another wireless device is detected. In order to do this, the receivers of the base station radio equipment and the mobile station radio equipment are provided with means for detecting the reception level and means for comparing parallel digital signals in addition to the main demodulator to detect code errors in the digital signals. 1. An interference detection method characterized in that the occurrence of interference on the same frequency from another wireless device is known by constantly monitoring the reception level and code errors of demodulated signals. (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 determined each time the switching is performed. By checking, the presence of interference waves can be determined more reliably than in the case of one receiving antenna and one receiving device, according to claim (1). Detection method.