JPH0779190A - Digital mobile body communications system - Google Patents

Abstract

PURPOSE:To improve the communication efficiency and to decrease an error rate by approximating the distance between a base station and a mobile station based on a received input level loss and calculating a phase lag so as to match a phase of the input signal with a phase of a standby clock. CONSTITUTION:An input level detector 27 of a base station 2 detects an input level of a received signal and discriminates it to be an input signal when the input level exceeds a predetermined threshold level and to be noise when less than the threshold level and uses an input signal/clock control section 28 to interrupt the input signal to a MODEM 23 in the case of noise. Furthermore, the input signal/clock control section 28 approximates a distance with a mobile station 3 based on the strength of the input signal level and calculates a phase delay of the input signal based on the distance and delays a demodulation reference clock 29 by the delay. Through the operation above, the demodulation reference clock 29 whose phase is almost coincident with the phase of the input signal is fed to a demodulation MODEM 23 independently of the distance from the mobile station 3 and the phase of the input signal is matched with the phase of the standby clock.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital mobile communication system for communicating between a mobile station and a control station via a base station, and more specifically, between a mobile station and a radio base station or a control with a mobile base station. The present invention relates to a communication synchronization method between stations whose distances are not constant such as between stations.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing a configuration of a conventional digital mobile communication system. In the figure, 1 is a control station, 2 is a base station, 3 is a mobile station, and 4 is a communication line connecting the control station 1 and the base station 2. Further, 21 is a clock synchronization circuit for generating a synchronization clock inside the base station from the reference clock, 22 is a modulation modem for transmission, 23 is a demodulation modem for reception, 24 and 25 are clocks for modulation and demodulation input to each modem, and 26 is demodulation. Clock 25 input to the modem 23 for
Phase adjuster for adjusting the phase of, 41 is a reference clock, 4
Reference numeral 2 denotes a transmission data line from the control station 1 to the base station 2, and 43 denotes a reception data line from the base station 2 to the control station 1.

TDMA (Time Division Multiple Acces)
In the digital mobile communication system adopting the s) method, the burst signals transmitted from each mobile station 3 to the base station 2 do not collide with each other in order to prevent the base station 2 from colliding with each other.
It is necessary to synchronize the transmission time of. Further, it is necessary to control the transmission time so that the signal from the base station 2 does not collide with the signal from the mobile station 3. Therefore, the transmission / reception time is controlled with a common time reference for the entire system. This time reference is set by the transmission of the synchronization reference burst signal from the base station 2, but in mobile communication, the distance (propagation path length) between the base station 2 and the mobile station 3 changes every moment. When the average distance between the base station 2 and the mobile station 3 changes between the center of the zone and the periphery of the zone, synchronization control becomes difficult.

FIG. 2 is a time chart for explaining the present invention. The conventional method will be described with reference to FIG. The following three cases are considered as the standby phase of the input signal in the conventional base station 2. (I). When the standby phase is at a fixed position. That is, when the standby phase is at a fixed position by the standby phase fixing method that fixes the standby phase at the center position calculated from the service range of the base station 2 (in the case shown in (3) of FIG.
It is fixed assuming 0 km). This fixed waiting phase is fixed in the clock synchronization circuit 2 in the base station 2 shown in FIG.
At 1, the clock having a frequency synchronized with the reference clock 41 is generated, supplied to the transmission modulation modem 22 as the transmission reference clock 24, and sent to the phase adjuster 26. The phase adjuster 26 delays the phase by a predetermined phase and receives the reference reference. Clock 2
5 is supplied to the reception demodulation modem 23. (B). When the standby phase is not controlled. That is, FIG.
As shown in (4) of the above, the phase at the time of the immediately preceding incoming call is the standby phase, which is a so-called floating type. In this case, in the base station 2 shown in FIG.
Is omitted. (C). In the case of (a) or (b) above, there is no guard against interference waves (noise). In this case,
As shown in (5), the PLL frequency in the modem 23 fluctuates in order to synchronize with the input noise, so that the standby phase fluctuates randomly. In terrible cases,
The frequency of the PLL in the modem 23 is pulled up to the upper limit or the lower limit of the VCO, which becomes the standby phase.

[0005]

In the conventional digital mobile communication system, the standby phase of the base station with respect to the mobile station is determined as described above, and therefore the difference in the distance between the mobile station and the base station is caused. There is a problem that it takes time to pull in.

That is, even if the standby phase is fixed and there is no noise, when the mobile station is located at a close range to the base station or at the far end, the standby phase for bit synchronization is established. And the input phase is significantly different (up to 180 degrees), and it takes time to pull in. Further, if the standby phase is pulled to the upper limit or the lower limit by noise, it generally takes more time to pull in than the fixed value. Therefore, in the conventional method, it is necessary to take a long bit stream for synchronization, communication efficiency is poor,
In addition, the error rate becomes high, the chances of retransmission due to erroneous reception increase, and the incommunicable area expands.

The present invention has been made to solve the above problems, and reduces the difference between the standby phase and the input phase due to the difference in the distance between the mobile station and the base station and noise. It is an object of the present invention to provide a digital mobile communication system capable of shortening a bit stream for synchronization pull-in having no significant signal, improving communication efficiency, and reducing an error rate.

As a prior art technique for synchronizing digital communication, a synchronization pulse sent from the control station is delayed in order to synchronize the control station with each base station. "Digital mobile communication system", Japanese Patent Laid-Open No. 2-238732 "Digital mobile communication system" in which the amount of line delay between a switch and a base station is adjusted in each base station, a central station based on digital signals from satellites There is Japanese Patent Laid-Open No. 59-6642 "Mobile Communication Satellite Synchronization System" for correcting the phase of transmission signal data transmitted from a base station.

[0009]

In a digital mobile communication system according to the present invention, a base station approximates a distance between a base station and a mobile station from a received input level loss from the mobile station, and a propagation delay time, that is, a phase. Calculate the delay amount and match the phase of the standby clock.

In the case of a system in which the output power of the mobile station is controlled by the input level of the signal from the base station, the output level of the mobile station is controlled so as to change every integer multiple of the phase difference 2π. .

Further, in the mobile station, the distance between the base station and the mobile station is approximated from the received input level loss from the base station,
The propagation delay time, that is, the phase delay is calculated, and the phase of the output modulation signal output by the mobile station is controlled by this delay.
In this case, when changing the output power of the mobile station,
Control is performed so that the change in the output phase due to the change in the output power is corrected.

In a system in which the output power of the mobile station is controlled by the input level of the signal from the base station, when the mobile station controls the output power, the change in the output phase due to the change in the output power is corrected. Including the above, the mobile station controls the phase. When the mobile station does not control the output power, the base station controls the phase.

When the base station or the mobile station performs phase control, it is determined that there is a phase difference only when the phase difference between the phase of the input signal and the phase of the standby clock is close to an integral multiple of π in the base station. Then, either phase is shifted by π.

Further, the effective reception level is determined so that the standby frequency and phase of the base station do not fluctuate due to the interfering wave, and control is performed so as not to change the standby phase below that level.

[0015]

With the digital mobile communication system of the present invention having the above-mentioned configuration, a signal (burst signal) input to the base station in burst such as a calling signal from the mobile station.
On the other hand, by eliminating the phase difference between the standby phase and the received signal, the bit synchronization can be performed quickly and surely, the error rate can be reduced, and the transmission time of the sync pull-in bit stream placed before the significant signal can be shortened.

[0016]

【Example】

Example 1. Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 7 indicate the same or corresponding portions. In the base station 2, 27 is an input level detector, 2
Reference numeral 8 is an input signal / clock control unit, and 29 is a demodulation reference clock. In the mobile station 3, 31 is a clock reproduction circuit for reproducing a clock signal from an input signal, 32 is a demodulation modem for reception, 33 is a modulation modem for transmission, 34 is a control unit, 35 is a power amplifier, and 36 is an input level detection. The output level of the output from the power amplifier 35 is controlled by the detection output of the input level detector 36 so that the output phase changes every 2π minutes.

Next, the operation will be described. The general transmission / reception operation between the base station 2 and the mobile station 3 is the same as the conventional method, and the description thereof is omitted here, but in the present embodiment, the base station 2 and the mobile station 3 communicate with each other. It operates so as to automatically reduce the difference between the input phase and the standby phase due to the difference in the distance and the noise. That is, in the base station 2, the input level of the received signal is detected by the input level detector 27, and when the input level exceeds a certain threshold, the input signal is detected. If there is noise, the input signal / clock control unit 28 cuts off the input signal to the modem 23. By this operation, it is possible to prevent a phenomenon in which the frequency of the PLL in the modem 23 is pulled by noise and the standby phase greatly differs from the input phase.

The input signal / clock controller 28 approximates the distance to the mobile station 3 based on the strength of the input signal level, and calculates the phase delay amount of the input signal from this distance.
The demodulation reference clock 29 is delayed by this delay amount. By this operation, the modem 23 regardless of the distance from the mobile station 2
A demodulation reference clock 29 whose phase is substantially the same as that of the input signal can be supplied to the demodulation modem 23, the phase of the input signal and the standby phase can be matched, and the lead-in time can be shortened.

The above operation will be described with reference to FIG. Figure 2
Is a diagram showing the phase of the modulation clock of 4 kHz.
(1) is the output phase of the base station, and (2) of FIG. 2 is the input phase of the base station. This base station input phase causes a phase delay depending on the distance between the base station and the mobile station. At that point, a phase difference of 180 degrees occurs. Therefore, when the standby phase shown in (3) of FIG. 2 is fixed to a distance of 10 km, a phase difference occurs when the distance from the mobile station is other than 10 km, and so-called floating shown in (4) of FIG. Even in the case of the formula, a phase difference occurs when the mobile station 2 has not moved since the last incoming call or other than coincidence. Further, as shown in (5) of FIG. 2, when the standby phase changes randomly following noise, the input signal phase and the standby phase rarely coincide with each other. Therefore, in the case as shown in (3) to (5) of FIG.
In both cases, it takes unnecessary time to pull in. According to the present invention, as described above, if the input level is less than or equal to the predetermined threshold value, it is determined to be noise and the following is prevented, the phenomenon shown in FIG. By calculating the phase delay and changing the standby phase as shown in (2) of FIG. 2, the input signal phase and the standby phase are matched.

Example 2. In the device of the system in which the mobile station 3 controls the output level according to the input level from the base station 2 to improve the communication quality, a phase difference occurs when the output level of the mobile station 3 arbitrarily changes, and a standby phase is generated. Since they do not match, the input level detector 36 detects the input level,
The power amplifier 3 is configured so that the output level changes every integer multiple of the phase difference 2π (a loss amount during propagation of 37.5 km when a modulation clock of 4 kHz is used).
Control 5 Further, as shown in FIG. 3, when the phase adjuster 37 is provided in the mobile station 3 and the output level is changed, the base station 2 moves by adjusting the output phase by the change in the output level. The standby phase can be controlled regardless of the switching of the power of the station 3.

Example 3. In the second embodiment, the mobile station 3 controls the phase of the output power by the phase adjuster 37, and the base station 2 also controls the phase of the received signal by the input signal / clock control unit 28. The same operation can be performed by only the control. That is, as shown in FIG. 3, the input level detection circuit 36 of the mobile station 3 detects the input signal level from the base station 2 and approximates the distance to the base station 2 by the strength of this input signal level. The round trip phase delay amount between the base station 2 and the mobile station 3 is calculated from the distance and the clock whose phase is advanced by the phase adjuster 37 by this delay amount is supplied to the transmission modem 33. The station 2 can always receive the input signal of the same phase from the mobile station 3, and thus the base station 2 can match the standby phase and the input phase without any control including the case of switching the output power.

Example 4. In Examples 1 to 3 above,
If a phase difference is assumed to occur between the input signal phase and the standby phase, control is performed even with a slight difference, but only when the phase difference is around ± π, the standby phase (even the input signal phase is It is also possible to perform a simple control for shifting (good) by π. That is, as shown in FIG.
A control range (indicated by diagonal lines) is defined, and control is performed when the input signal phase is within this hatched range. For example, when the standby phase of the base station 2 is at the position shown in (1) of FIG. 4 (B) and the phase of the input signal is as shown in (2) of FIG. 4 (B), the phase difference Is around π. Therefore, only in such a case, control is performed to shift the standby phase by π as shown in (3) of FIG. 4B, and the phase difference that takes the longest time to pull in when there is no noise is around ± π. Is controlled to shorten the pull-in time.

Example 5. In addition, in the first embodiment, noise (interference wave) detection is performed by the input level detection circuit 27.
Although it is configured to judge whether or not the input level exceeds a predetermined threshold value, effective processing cannot be performed when an interfering wave exceeds this threshold value. In the fifth embodiment, as shown in FIG. 5, a circuit for detecting a unique word or frame other than the input level, for example, after the output of the modem 23 and detecting an interfering wave, or a P in the modem 23.
An interfering wave detection circuit 50 composed of a circuit for detecting an interfering wave according to the lag lock time is provided separately so that effective processing can be performed even for an interfering wave of a level exceeding a threshold value.

Example 6. Although the above embodiment describes the data communication between the fixed base station 2 and the mobile station 3, the present invention is not limited to this. For example, the mobile base station 2a and the mobile station 3 may be connected to each other. (FIG. 6 (A)), between the mobile base station 2a and the control station 1 (FIG. 6 (B)), between the mobile base station 2a and the fixed base station 2 (FIG. 6 (C)), Between the base stations 2a (FIG. 6D), between the mobile stations 3 (FIG. 6D).
It goes without saying that (E)) can be similarly implemented.

[0025]

As described above, according to the present invention, since the standby phase is controlled by the input level, the following effects can be obtained.

The distance from the mobile station is approximated by the input level, the phase difference between the input signal phase and the standby phase is calculated, and the standby phase and the input signal phase are matched to shorten the lead-in time. .

Further, when the input level is less than the threshold value, it is judged as noise, and it is possible to prevent the frequency of the PLL from being pulled to the upper limit or the lower limit by the noise, and the pull-in time can be shortened.

Further, since the pull-in time can be shortened, the bit line for synchronous pull-in can be shortened, the communication error can be reduced, the chance of retransmission due to erroneous reception can be reduced, and the expansion of the incommunicable area can be prevented. There are effects such as an efficient digital mobile communication system being obtained.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining a first embodiment and a second embodiment of the present invention.

FIG. 2 is a time chart diagram for explaining the difference between the operation of the embodiment shown in FIG. 1 and the operation of the conventional method.

FIG. 3 is a block diagram for explaining another configuration example of the second embodiment of the present invention and the third embodiment of the present invention.

FIG. 4 is a diagram for explaining a fourth embodiment of the present invention.

FIG. 5 is a block diagram for explaining a fifth embodiment of the present invention.

FIG. 6 is a diagram for explaining a sixth embodiment of the present invention.

FIG. 7 is a block diagram for explaining a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 control station 2, 2a base station 3 mobile station 4 communication line 21 clock synchronization circuit 22 transmission modulation modem 23 reception demodulation modem 24, 25 modulation / demodulation clock 26 phase adjuster 27 input level detector 28 input signal / clock control unit 29 demodulation reference clock 31 clock recovery circuit 32 reception demodulation modem 33 transmission modulation modem 34 control unit 35 power amplifier 36 input level detector 37 phase adjuster 41 reference clock 42 transmission data from control station 1 to base station 2 43 Received data from base station 2 to control station 50 Interfering wave detection circuit

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[Procedure amendment]

[Submission date] September 24, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

TDMA (Time Division Multiple Acces)
In the digital mobile communication system adopting the s) method, the burst signals transmitted from each mobile station 3 to the base station 2 do not collide with each other in order to prevent the base station 2 from colliding with each other.
It is necessary to synchronize the transmission time of. Further, it is necessary to control the transmission time so that the signal from the base station 2 does not collide with the signal from the mobile station 3. Therefore, the transmission / reception time is controlled with a common time reference for the entire system. This time reference is set by the transmission of the synchronization reference burst signal from the base station 2, but in mobile communication, the distance (propagation path length) between the base station 2 and the mobile station 3 changes every moment. When the average distance between the base station 2 and the mobile station 3 changes between the center of the zone and the periphery of the zone, synchronization control becomes difficult. Digital mobile communication not adopting TDMA method
Even in the system, bit synchronization control has the same difficulty.
U

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

Example 6. Although the above embodiment describes communication between the fixed base station 2 and the mobile station 3,
The present invention is not limited to this. For example, between the mobile base station 2a and the mobile station 3 (FIG. 6A), between the mobile base station 2a and the control station 1 (FIG. 6B). , Mobile base station 2
a and the fixed base station 2 (FIG. 6C), the mobile base station 2
between a (FIG. 6D), between mobile stations 3 (FIG. 6D).
It goes without saying that (E)) can be similarly implemented.

Claims (6)

[Claims] 1. A mobile station such as a mobile station or a mobile base station (hereinafter collectively referred to as a mobile station) and a fixed base station or a control station or a mobile station other than the mobile station (hereinafter collectively referred to as a mobile station). In a digital mobile communication system in which synchronization control is performed between base stations), the input signal level is monitored at the base station, and the distance to the mobile station is approximated by the strength of the input signal level. The phase delay amount of the input signal is calculated, and the phase of the standby clock of the PLL circuit for bit synchronization for this delay is controlled,
A digital mobile communication system comprising means for automatically matching the phase of an input signal and the phase of a standby clock. 2. A digital mobile communication system for performing synchronous control between a mobile station and a base station, wherein the input signal level is monitored in the mobile station, and the strength of the input signal level causes a difference between the base station and the mobile station. Approximate the distance,
The phase delay amount of the input signal input to the base station is calculated from the approximate distance, and the phase of the output modulation signal output by the mobile station is controlled by this delay, and the bit synchronization PLL in the base station is calculated.
A digital mobile communication system comprising means for automatically matching the phase of the standby clock of the circuit and the phase of the input signal from the mobile station. 3. When a mobile station adopts a digital mobile communication system in which the output level is controlled by the input level from the base station, the change in the output level of the mobile station is an integer multiple of the phase difference 2π. 3. The digital mobile communication system according to claim 1 or 2, further comprising: a means for controlling the output of the mobile station so that each of them is controlled by the following. 4. A digital mobile communication system in which synchronization control is performed between a mobile station and a base station, and a digital mobile communication system in which the mobile station controls the output level to be changed according to the input level from the base station is adopted. When changing the output level at the mobile station, monitor the input signal level at the mobile station, approximate the distance between the base station and the mobile station by the strength of the input signal level, and The phase delay amount of the input signal input to the base station is calculated, and the phase of the output modulation signal output by the mobile station is calculated so that the delay amount and the change in the output level of the mobile station are every integer multiple of the phase difference 2π. To automatically match the phase of the standby clock of the bit synchronization PLL circuit in the base station with the phase of the input signal from the mobile station. When it is not changed, the input signal level is monitored at the base station, the distance to the mobile station is approximated by the strength of the input signal level, the phase delay amount of the input signal is calculated from the approximated distance, and this delay component is calculated. A digital mobile communication system comprising means for controlling the phase of the standby clock of the bit synchronization PLL circuit and automatically matching the phase of the input signal with the phase of the standby clock. 5. A means for calculating the phase difference between the phase of the standby clock of the bit synchronization PLL circuit and the phase of the input signal from the mobile station according to the strength of the input signal level to match the two phases, 5. The digital signal according to claim 1, wherein the phase difference is judged to exist only when the phase difference is close to an integer multiple of π, and one of the phases is shifted by π. Mobile communication system. 6. An interference wave detecting means for detecting noise (interference wave) is provided, and when noise is input, the input to the demodulation modem is cut off, and the phenomenon that the frequency of the PLL in this modem is pulled by the noise The digital mobile communication system according to claim 1, 2, 4, or 5, wherein the digital mobile communication system is configured to prevent it.