JP2553286B2 - Asynchronous interference avoidance method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to digital radio communication of a plurality of channels by time division time slots, and more particularly,
Asynchronous interference avoidance method for detecting and avoiding an interference wave that is asynchronous with the signal wave existing in the digital signal wave of the desired channel in digital mobile radio communication such as an automobile telephone, in particular, before the reception failure occurs in the desired information signal. It is designed so that it can be detected quickly and reliably by the eyes.

[0002]

2. Description of the Related Art In this type of digital mobile radio communication,
There are a frequency division method that allocates communication channels with different carrier frequencies and a time division method that allocates communication channels in bursts at different timings by providing respective time slots. In mobile radio communication using a band, the same channel in the allocated frequency band is reallocated in regions spatially separated to make effective use of frequencies. However, with the movement of moving bodies such as automobiles, the strength of received radio waves changes momentarily due to so-called fading,
Occasionally, the strength of the re-assigned radio waves from the distant area reverses and becomes stronger, and the communication information by the desired signal wave may not be obtained. Therefore, it is necessary to constantly monitor whether or not the reception quality of the desired signal wave is interfered with by another communication wave of the same frequency that has been reassigned, and how Whether or not to avoid is an important issue in this type of mobile radio communication.

[0003]

In time-division digital mobile radio communication, conventionally, when communication channels are allocated in a time-division manner, the communication timings of signal waves of a plurality of channels are synchronized with each other. It is assumed that they are switched so that they do not overlap each other. However, when the number of originating base stations is extremely large like in a home digital cordless telephone, it is difficult to synchronize all the base stations with each other. Will be performed.

In such a state of asynchronous time division communication, as shown in FIG. 1, when there is a time difference t of t = T at the beginning between the burst frame of the own station and the burst frame of the asynchronous interfering station, a plurality of The same time difference T is not held for each cycle of time slot allocation in the time division of the channel, but the two asynchronous digital signals are compared with each other at a speed corresponding to the difference between both clock frequencies. It will slowly shift relative to each other. That is, if the difference in clock frequency accuracy between the desired wave and the interference wave is η, and the elapsed time is Δt, the time difference between both burst frames in the elapsed time is Δt × η seconds. Clock frequency accuracy difference η
= 5 × 10 ^-6 and the clock frequency is 384 kbps, it takes about 1 bit to shift both burst frames.
It will take 0.5 seconds. As a result, even if communication is first started in a state in which the desired signal wave is not interfered with, interference may start to occur over time, and the interference may increase gradually. In addition, when interference is caused by a strong interference wave, even if an attempt is made to exchange control information signals to avoid the interference, a code error based on the interference interference is detected by the collation of the error detection code. Then, as a result of the error detection, all the received information signals are discarded as having an error, so that there is a problem that the control information signal for avoiding interference cannot be exchanged.

[0005]

When the desired signal wave starts to be interfered with by the asynchronous interference wave as described above,
The bit deteriorated by the interference wave does not extend over the entire length of the burst frame of the desired signal wave, but is generally only a part of the burst frame at the beginning. For example, when asynchronous interference is received from the rear of the burst frame, the ramp bit added to the information bit for the fall of the burst frame is transmitted before the information signal bit is interfered. It will be. As described above with reference to FIG. 1, since the relative time lag of the asynchronous interference wave is extremely slow, it takes some time from when the ramp bit starts to interfere to when the information signal bit starts to interfere. It takes. Therefore, if the interference avoidance operation is performed in the meantime, the information signal bit is not interfered with, and the information signal bit can be restored without error.

The object of the present invention is to solve the above-mentioned problems of the prior art, to detect an asynchronous interference immediately before the interference due to the asynchronous interference wave reaches the information signal and with good accuracy or accuracy. An object of the present invention is to provide an asynchronous interference avoidance method for performing avoidance control operation.

That is, the asynchronous interference avoidance method of the present invention is
In the bit pulse that forms the transient response ramp bit at the falling edge of the burst frame transmitted by being added to each of the digital information signals of the multiple channels that are time-division-multiplexed by digital phase modulation corresponding to each channel About one bit in the bit pulse, in order to detect whether or not there is asynchronous interference in the digital information signal of the channel, a specific phase transition such that the bit becomes specific data is added and transmitted. Then, on the receiving side, the received signal wave of the channel is demodulated, and 1 bit in the bit pulse forming the ramp bit for transient response is separated from the demodulated signal and taken out. By detecting that they are different, transmission is performed with a phase transition different from the specific phase transition. The possible senses, is characterized in that to trigger the control for avoiding interference is determined that asynchronous interference digital information signal the received exists.

[0008]

Therefore, in the asynchronous interference avoidance method of the present invention, the interference avoidance operation is performed particularly effectively and accurately by detecting the interference caused by the asynchronous interference wave from the rear of the burst frame in the desired signal wave of the time division digital mobile radio communication. Can be efficiently started.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. First, FIG. 2 shows the structure of a communication time slot in a digital cordless telephone as an example of digital mobile radio communication suitable for applying the asynchronous interference avoidance of the present invention. In the illustrated time slot, a 4-bit ramp bit (R) for transient response (for rising), a 2-bit start symbol (SS), a 6-bit preamble (PR), and a 16-bit unique word for synchronization (UW) ) Followed by a 180-bit information signal is encoded in the form of a cyclic code (CRC), and then a 16-bit CRC coded bit is further added for code error detection.
Ramp bit for transient response of bit (R) (for falling)
Is added. Normally, when a code error occurs in the information signal bit, the C received after the information signal bit is received.
When the RC coded bit and the CRC coded bit generated on the reception side are compared with each other, they do not match each other, and the code error in the immediately preceding information signal bit can be detected reliably and easily. In this way, when an error is detected in the CRC coded bit, all the received information signal bits are discarded as having a code error, and the information is not sent to the upper information processing process. As a result, when strong interference waves are interfering, almost all CRC coded information signal bits have similar CRC code errors after the error detection by the CRC coded bits. It becomes impossible to send and receive the control information signal for. Therefore, in order to solve this problem, it is necessary to detect the occurrence of interference quickly and reliably before the interference occurs on the CRC coded bit and further on the preceding information signal bit.

However, the rising and falling edges in the burst frame shown in FIG. 2 gradually change the amplitude of the bit pulse over the period of 4 bits of the transient response ramp bit (R) to spread the spectrum. Suppressed, and no particular data transmission is typically imposed on the rising and falling four bits, and no particular phase transition is given. However, in the present invention, with respect to the four bits of the trailing edge, specific data transmission is imposed on at least one bit of the trailing edge so that the presence of interference can be detected easily and reliably. At the point of time, a specific phase transition is given to the 4-bit pulse with a gentle change in amplitude.

FIG. 3 is a schematic diagram of a burst frame transmission system configured to perform detection of such asynchronous interference using the method of the present invention and avoidance control according to the detection result.
Shown in On the transmission side of the transmission system with the configuration shown,
An information signal to be transmitted is supplied to the signal synthesizing circuit 1, and a rising ramp bit (R), a start symbol (SS), a preamble (PR), a unique word (UW), a cyclic code (CRC), and a phase transition of a specific pattern. Ramp bit (R) of trailing edge with at least 1 bit added to
2 to synthesize the burst frame having the configuration shown in FIG. 2, supply the synthesized signal to the modulation circuit 2 to modulate the carrier, and supply the modulated output carrier signal to the amplitude control circuit 3 to supply the control signal. The rising and falling pulse amplitudes are controlled by to form a transmission signal wave, which is transmitted from the antenna 4. On the other hand, on the receiving side, the burst frame of the demodulated output signal obtained by supplying the received signal wave from the antenna 5 to the demodulation circuit 6 is supplied to the reception processing circuit 8 to perform processing such as synchronization of the received frame and error detection. Is supplied to the separation circuit 7, and under the control of the processing output signal of the reception processing circuit 8, if no code error is detected, only the information signal portion is extracted and output as a reception information signal. . In the separation circuit 7, a ramp bit pulse given a specific phase transition at the falling timing of the burst frame is taken out and supplied to the comparison / determination circuit 9, and the specific phase transition given to the ramp bit pulse is taken out. Is compared with a specific phase transition provided on the receiving side to determine the presence / absence of a transmission error, and the result of the error determination is supplied to the control circuit 10 together with the processing output of the reception processing circuit 8, and the falling ramp bit pulse When there is a transmission error in a specific phase transition, an interference avoidance control signal is output to activate a separately required interference avoidance operation.

[0012]

As is apparent from the above description, according to the present invention, when performing time division digital mobile radio communication, an asynchronous interference wave causes interference from the rear of a burst frame in a desired signal wave. The interference can be detected accurately while the interference avoidance operation is efficiently performed.

Further, when the interference is exerted from the front of the burst frame, a circuit for detecting an error generated in the preamble of the known pattern provided at the front end of the burst frame is provided to detect asynchronous interference and Since the avoidance operation can be performed, when combined with the interference detection from the rear side according to the present invention described above, asynchronous interference from either the front side or the rear side of the frame burst can be detected rapidly and the interference avoidance operation can be effectively and accurately performed. There is a remarkable effect that can start.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of timing of occurrence of interference in asynchronous time division communication.

FIG. 2 is a diagram showing an example of the configuration of a time slot of a digital cordless telephone.

FIG. 3 is a block diagram showing a configuration example of a mobile radio communication system configured by using the method of the present invention.

[Explanation of symbols]

 1 signal synthesis circuit 2 modulation circuit 3 amplitude control circuit 4,5 antenna 6 demodulation circuit 7 separation circuit 8 reception processing circuit 9 comparison judgment circuit 10 control circuit

Claims (1)

(57) [Claims] 1. A transient response ramp bit at the falling edge of a burst frame transmitted by being added to each of a plurality of channels of digital information signals which are divided by digital phase modulation corresponding to each channel and time division multiplexed. One bit in the bit pulse in the formed bit pulse has a specific phase transition such that the bit becomes specific data in order to detect whether or not there is asynchronous interference in the digital information signal of the channel. Is added and transmitted, the receiving side demodulates the received signal wave of the channel, and one bit of the bit pulse forming the transient response ramp bit is separated from the demodulated signal and taken out, and the bit pulse Is detected to be different from the specific data, thereby detecting a position different from the specific phase transition. A non-synchronized interference avoiding method, which detects transmission of a phase transition, determines that there is asynchronous interference in the received digital information signal, and activates control for avoiding interference.