JPS6355819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a mobile communication system using digital transmission technology in which the reception level constantly fluctuates greatly.
This invention relates to a method for detecting interference waves of the same frequency when co-frequency interference exists.

Communication methods using conventional digital transmission technology are
Because it was based on a wireless transmission line, such as a microwave line, designed so that the reception level fluctuates relatively little or very slowly and is less susceptible to co-frequency interference, constant reception was not possible. In mobile communication systems, where there are level fluctuations and interference stations with the same frequency always exist, or where interference sometimes occurs due to the movement of interfering stations with the same frequency, the level fluctuations of both the desired wave and the interference wave are random. Therefore, there was a drawback that quality deterioration due to interference waves and quality deterioration due to received level fluctuations could not be stably distinguished.

In order to solve these drawbacks, the present invention aims to improve the ability to detect interference waves at the same frequency by using digital transmission technology in a mobile radio transmission channel where the received level always fluctuates greatly and there is interference at the same frequency. The drawings will be described in detail below.

FIG. 1 shows an example of the configuration of a digital signal train during a call according to an embodiment of the present invention, in which 1 is a frame signal;
2 indicates a coded audio signal, and the audio signal 2 is a frame signal 1 consisting of one or several bits.
is added at regular intervals. Furthermore, a configuration in which an identification signal, a pseudorandom signal, or an error correction code is added to the frame signal 1 is also conceivable.

FIG. 2 shows an example of the configuration of a transmitter according to an embodiment of the present invention, in which 3 is a voice encoding device, 4 is a signal configuring device that configures the digital signal string of FIG. 1, 5 is a modulating device, and 6 indicates a transmitting device. This transmitter operates as follows. First, the analog voice signal from the transmitter is encoded by the voice encoding device 3 to become a digital signal, and the signal configuring device 4 adds a frame signal 1 consisting of one to several bits to the first signal.
Perform the signal configuration shown in the figure. The signal train as shown in FIG. 1 enters the modulator 5, where it modulates a radio carrier wave as a modulation signal, and is transmitted from the transmitter 6.

FIG. 3 shows an example of the configuration of a receiver according to an embodiment of the present invention, in which 7 is a receiving device, 8 is a demodulating device, 9 is a reception level detecting device, 10 is a clock signal extracting device, and 11 is a frame signal extracting device. 12 is a signal separation device for separating audio signals from the signal train shown in FIG. This is an interference determination device that determines the presence or absence of co-frequency interference.

This receiver operates as follows. Assuming that a desired wave has been received and a call is being made, the radio carrier wave received by the receiving device 7 is level-detected by the received level detecting device 9, and converted into a digital signal string by the demodulating device 8. demodulated. A clock signal extraction device 10 extracts a clock signal and a frame signal extraction device 11 extracts a frame signal from the demodulated signal sequence, and these signals are used to separate a signal corresponding to an audio signal in a signal separation device 12. The signal is then decoded into voice by the decoding device 13, and the decoded analog signal is sent to the receiver.

On the other hand, the interference determination device 14 detects a plurality of frame signals from the frame signal extraction device 11 for a certain period of time, measures the detection rate of the frame signals, and constantly monitors the reception level detection results in the reception level detection device 9. I'm monitoring it. If co-frequency interference occurs, the reliability of the signal transmission on the wireless transmission path will deteriorate even though the reception level is high, and the frame signal detection rate will also deteriorate. When it is determined that the measured value of the reception level by the reception level detection device 9 is high and the frame signal detection rate in the frame signal extraction device 11 has deteriorated, it is determined that there is interference at the same frequency.

In order to detect that the detection rate of a frame signal has deteriorated, for example, when detecting an error rate of 10 ^-2 , it is necessary to observe at least 100 frames. If there is one frame error in it,
This results in an error rate of 10 ^-2 . However, in order to ensure this value, it is necessary to observe and average frame errors over a longer period of time.

Therefore, in order to shorten the time for detecting the deterioration of the wireless line using only the frame signal mentioned above, a signal in which an identification signal is added to the frame signal, a signal in which a pseudo-random signal is added to the frame signal, or an error correction code is added to the frame signal. A configuration example using an added signal can be considered.

In these configurations, the transmitter is provided with a device for adding the above-mentioned signal to the audio signal, and the receiver is provided with a device for extracting or identifying the above-mentioned signal in addition to the frame signal extraction device.

When these configuration examples are used, deterioration of the wireless line is detected as follows.

When an identification signal is added, it is assumed that the wireless line has deteriorated if the identification signal of the own station cannot be detected for one frame or several frames consecutively, or if the identification signal of another station is extracted.

When a pseudorandom signal is added, it is assumed that a code error in the pseudorandom signal unique to each station is detected within one frame or several frames, and the wireless line is degraded.

When an error correction code is added, it is assumed that an error in the error correction code in one frame or several frames is detected and the wireless line has deteriorated.

As explained above, by constantly detecting the reception level, periodically adding a signal such as a frame signal to the encoded audio signal and transmitting it, and evaluating the signal reliability of the added signal, Since the status of the wireless line is constantly monitored, deterioration in the signal reliability of the wireless line is detected when another interfering station on the same frequency approaches or when a call is started, even if the reception level is sufficiently high. Therefore, there is an advantage that interference of the same frequency during a call can be efficiently detected.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a signal sequence during a call according to an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a transmitter according to an embodiment of the present invention, and FIG. FIG. 2 is a diagram showing the configuration of a receiver according to an embodiment. DESCRIPTION OF SYMBOLS 1... Frame signal, 2... Coded audio signal, 3... Audio encoding device, 4... Signal configuration device, 5... Modulation device, 6... Transmission device, 7... Receiving device, 8 ...Demodulator, 9...Reception level detection device, 10...Clock signal extraction device, 11...
Frame signal extraction device, 12...signal separation device,
13...Audio decoding device, 14...Interference determination device.

Claims (1)

[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, digital transmission technology is used between the base station wireless device and the mobile station wireless device. When any one wireless line is selected and set from a group of multiple wireless lines and a call is in progress, in order to detect interference of the same frequency from other wireless devices, the transmitter of the wireless device: A signal string in which a frame signal is added at regular intervals between encoded audio signals, a signal string in which a frame signal and an identification signal are added, a signal string in which a frame signal and a pseudorandom signal are added, or a frame signal and an error. A signal string with a correction code added is configured and transmitted from a transmitter, and the receiver of the wireless device detects the reception level and demodulates the signal string, and from the demodulated signal string, a signal is sent at regular intervals. Extract the frame signal, identification signal, pseudorandom signal, or error correction code that appears, and check the deterioration of the detection rate of the frame signal due to interference waves, the identification signal of the interfering station, a code error in the pseudorandom signal, or an error in the error correction code. An interference detection method characterized by detecting an increase in the detection rate of codes to determine the occurrence of interference on the same frequency from other wireless devices.