JPH0833037A - Inter-base station frame phase synchronizing method - Google Patents

Abstract

PURPOSE:To decide stable transmission timing without being affected by the fluctuation of a reception input level caused by fading or the like by deciding the transmission timing of a control signal to be newly transmitted from its own base station every time while considering the transmission timing of a control signal transmitted from an adjacent base station. CONSTITUTION:The control signal transmitted from a base station 1 is received at a base station 2 and the output of that received signal after the detection of an envelope is passed through a comparator 12 for a phase detection level V. The difference between the transmission timing of transmitted signals from the base stations 1 and 2, namely, phase difference gamma of transmitted frames is calculated from the output of the comparator 12 and the transmission timing of the base station 2. A value alpha correcting that phase difference gamma corresponding to a correcting value provided from a reception input level A and the phase detection level V is defined as the phase difference of transmitted frames between two base stations. Based on this phase difference alpha, the transmission timing of the base station 2 is decided so as not to be overlapped with the transmission timing of the base station 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time division multiple access / time division bidirectional communication system (TDM) that uses the same frequency in both directions.
A / TDD) and time division multiple access / frequency division bidirectional communication method (TDMA / FD) that uses different frequencies bidirectionally
The present invention relates to a frame synchronization method between base stations in a mobile communication system using D).

[0002]

2. Description of the Related Art FIG. 1 shows a time division multiple access / time division bidirectional communication system (TDMA / TD) that uses the same frequency in both directions.
D) or a time division multiple access / frequency division bidirectional communication method (TDMA / F) that uses different frequencies in both directions
1 shows an outline of a mobile communication system using DD). In this system, it is necessary to synchronize the TDMA frames transmitted from the base station 1 and the base station 2, respectively.

Since a plurality of wireless stations transmit and receive signals at the same frequency at a predetermined time (slot) for each station within a predetermined cycle (frame) to communicate, the start of each frame It is necessary to match the time for all stations, and this is done by a common master clock. This is T
This is called phase synchronization of the DMA frame, and each station needs to transmit a signal in a designated slot in this frame. That is, in FIG. 1, it is necessary to synchronize the phases of the TDMA frames transmitted from the base station A and the base station B, respectively, and transmit the signal within each frame within a predetermined time (referred to as a burst signal). .

FIG. 6 shows a conventional TDMA / TDD system or a frame synchronization system between base stations in the TDMA / FDD system. Control signal transmitted from base station 1 (burst-shaped 1-slot signal transmitted at a certain fixed interval)
Is detected by the base station 2 and the phase detection level 19 for detecting the transmission timing of the base station 1 is set to a constant level in advance, and the phase is detected from the output signal of the demodulator 10 after envelope detection of the intercepted signal. The comparator 12 performs phase detection at the detection level. Here, the time difference β between the transmission timing of the interception signal from the base station 1 detected by the comparator 12 and the actual transmission timing of the base station 2 is corrected by the computer 16, and the base station 1 and the base station 2 obtained as a result are corrected. The inter-base station frame synchronization is achieved by determining the optimum transmission timing from the time difference of the transmission timings of the transmission signals, that is, the phase difference of the transmission frames. α is the difference between the transmission timings of the base stations 1 and 2.

FIG. 7 shows a method for measuring the time difference β between the transmission timing detected from the interception signal and the actual transmission timing. From the figure, the demodulator 10 receives the control signal transmitted from the modulator in the own base station, and the output after envelope detection is input to the comparator 12 in which the phase detection level 19 is set in advance to a constant value. As a result, the time difference between the transmission timing detected by the comparator 12 and the actual transmission timing output from the modulator 18 is measured by the counter 14. Let the measurement result be the time difference β.

[0006]

In a system in which a predetermined phase detection level is set by the conventional inter-base station frame synchronization method, when the level of the interception signal is constant as shown in FIG. 8 (1). 7 has a constant time difference β between the timing of the comparator output signal and the actual timing of the interception signal, the time difference of the transmission frame with the partner base station, that is, the phase difference can be accurately calculated, and a stable base station can be obtained. Inter-station frame synchronization can be established.

However, as shown in FIG. 8 (2), when the state of the transmission path changes with time as in mobile communication, the level of the interception signal also changes at the same time, and the deviation of the transmission timing time difference β increases. . As the deviation increases, the burst control slot signals deviate from a predetermined position (timing) within the frame, which causes a problem of interference between the respective transmission signals.

As described above, the object of the present invention is to shift each burst-shaped control slot signal from a predetermined position (timing) in a frame due to a change in the level of the interception signal,
An object of the present invention is to provide a frame synchronization method between base stations that solves the problem of interference, and to reduce control errors due to fluctuations in the received input level.

[0009]

The features of the present invention for achieving the above-mentioned object are to provide at least two base stations and a TDM.
In mobile radio communication in which bidirectional communication is performed with a mobile station using the A / TDD system or the TDMA / FDD system, the frequency of at least one control channel is used by a plurality of base stations in a time division manner to periodically transmit a control signal. In the inter-base-station frame phase synchronization method, one base station intercepts a control signal transmitted from another base station, detects the frame phase of the control signal, and determines the transmission timing of the control signal of the own base station. , The base station intercepts a control signal transmitted from another base station, and judges that the control signal is received when the output of the intercepted signal after envelope detection exceeds a phase detection level predetermined by the comparator. The time difference between the transmission timing of the interception signal detected by the comparator and the transmission timing of the control signal of its own base station, that is, the transmission frame is detected. The phase difference measured by counter,
The base station has means for detecting the reception input level of the control signal of another base station, and the time difference between the transmission timing detected by the comparator of the interception signal at that reception input level and the actual transmission timing is measured by the counter. The value obtained by subtracting from the phase difference of the transmission frame is used as the frame phase difference between the base stations, and the transmission timing of the own base station and the timing of the reception signal do not overlap and the timing difference is TDMA / TD.
In the inter-base-station frame synchronization method, the transmission timing of the control signal of the own base station is determined so as to be n (n = 1, 2 ...) Time of one transmission slot length of D or TDMA / FDD.

[0010]

According to the present invention, the phase detection level is fixed and the time difference of the transmission timings of the transmission signals of the base stations calculated based on the interception signal, that is, the phase difference of the transmission frame, is determined by the reception input level. The most important feature is to correct the phase difference. The difference from the conventional technique is that the phase difference of the transmission frame calculated based on the interception signal is corrected by the reception input level.

Since it is possible to correct the time difference of the transmission timing of the transmission signal of each base station calculated based on the interception signal, that is, the phase difference of the transmission frame, according to the reception input level, it is possible to make a sharp correction. Stable frame synchronization between base stations can be established by sufficiently following changes in the received input level.

[0012]

FIG. 2 illustrates the inter-base station frame synchronization system according to the first embodiment of the present invention (1). The same reference numbers as in FIG. 6 indicate the same. Further, FIG. 4 is a diagram illustrating a method of measuring the reception input level A. As shown in FIG. 2, the control signal transmitted from the base station 1 is intercepted by the base station 2, and the output of the intercepted signal after envelope detection is passed through a comparator 12 having a phase detection level V (constant). Next, the output of the comparator 12 and the base station 2
From the transmission timing of, the time difference between the transmission timings of the transmission signals of the base station 1 and the base station 2, that is, the phase difference γ of the transmission frame is obtained. On the other hand, as shown in FIG. 4, the output after envelope detection has an averaged level after being passed through an integrator and has a duty ratio (1 / 2k when the number of transmission slots is k in the TDMA / TDD system, TDMA / FDD). In the system, the reception input level is obtained as a value obtained by multiplying the reciprocal of 1 / k when the number of transmission slots is k. Then, as shown in FIG. 3, the time difference between the transmission timing detected from the interception signal and the actual transmission timing, that is, the correction amount t is calculated from the following equation:
A value α obtained by subtracting the correction value t from the phase difference γ of the transmission frame is set as the phase difference of the transmission frame between the two base stations.

A relational expression among the correction value t, the reception input level A and the phase detection level V is shown below.

Here, C is the equivalent capacitor value of the envelope detector, and R is the resistance value.

[0015]

[Equation 1]

Based on the phase difference α of the transmission frame between the two base stations obtained as described above, the transmission timing of the base station 2 and the transmission timing of the base station 1 do not overlap with each other, and the difference between the timings is TDMA / TDD. , Or TDMA / FD
D burst-like 1 slot length n (n = 1, 2 ...
-) The transmission timing of the transmission signal of the base station 2 is determined so as to be doubled. N of one slot length (n = 1, 2 ...)
By doubling, the timings of the control signals transmitted from the base station 1 and the base station 2 do not overlap, and interference can be prevented.

By doing so, stable inter-base station frame synchronization can be established without being affected by fluctuations in the reception input level.

FIG. 5 is a diagram for explaining another method for measuring the received input level A. From FIG. 2, the control signal transmitted from the base station 1 is intercepted by the base station 2, and the output of the intercepted signal after envelope detection is passed through a comparator having a phase detection level V (constant). Next, the time difference between the transmission timings of the transmission signals of the base station 1 and the base station 2, that is, the phase difference γ of the transmission frame is obtained from the output of the comparator 12 and the transmission timing of the base station 2.
On the other hand, as shown in FIG. 5, the output after envelope detection is used to obtain the reception input level A at the time when the pulse level becomes stable after a sufficient time t has elapsed from the start point of the pulse of the control signal. Then, as shown in FIG. 3, the correction amount t of the phase difference between the transmission frames of the base stations 1 and 2 is obtained from the following equation, and the value α obtained by subtracting the correction value t from the phase difference γ of the transmission frames is calculated by the two base stations. It is the phase difference between the transmission frames.

A relational expression among the correction value t, the reception input level A and the phase detection level V is shown below.

Here, C is the equivalent capacitor value of the envelope detector, and R is the resistance value.

[0021]

[Equation 2]

Based on the phase difference α of the transmission frame between the two base stations obtained as described above, the transmission timing of the base station 2 and the transmission timing of the base station 1 do not overlap and the timing difference is TDMA / TDD. , Or TDMA / FD
D burst-like 1 slot length n (n = 1, 2 ...
-) The transmission timing of the transmission signal of the base station 2 is determined so as to be doubled. N of one slot length (n = 1, 2 ...)
By doubling, the timings of the control signals transmitted from the base station 1 and the base station 2 do not overlap, and interference can be prevented.

By doing so, stable inter-base station frame synchronization can be established without being affected by fluctuations in the reception input level.

[0024]

As described above, according to the present invention, the transmission timing of the control signal to be newly transmitted from the own base station is determined each time in consideration of the transmission timing of the control signal transmitted from the adjacent base station. Since stable transmission timing can be maintained without being affected by fluctuations in the reception input level due to changes in the status of the transmission path due to fading, etc.,
We can provide high-quality services.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a system to which the present invention is applied.

FIG. 2 is a schematic diagram of an inter-base station frame synchronization method when the present invention is implemented.

FIG. 3 is a diagram showing an envelope detector and illustrating a method of calculating a phase difference correction value from a received input level when the present invention is implemented.

FIG. 4 is a diagram illustrating a method for measuring a reception input level according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating another method for measuring the reception input level according to the embodiment of this invention.

FIG. 6 is a schematic diagram of a conventional inter-base station frame synchronization method.

FIG. 7 is a configuration diagram for obtaining a reference value of a time difference between a timing of a comparator output and an actual transmission timing.

FIG. 8 is a diagram illustrating a problem that occurs in a conventional inter-base station frame synchronization method.

[Explanation of symbols]

 10 Base Station 2 Demodulator 10a Envelope Detector 12 Comparator 14 Counter 16 Computer 18 Base Station 2 Modulator 20 Received Input Level Measuring Circuit

Claims (3)

[Claims] 1. At least two base stations and TDMA /
In mobile radio communication in which two-way communication is performed with a mobile station using the TDD method or TDMA / FDD method, at least one control channel frequency is used in a time division manner in a plurality of base stations to periodically transmit a control signal. Then, a base station intercepts a control signal transmitted from another base station, detects the frame phase of the control signal, and determines the transmission timing of the control signal of its own base station. The station intercepts the control signal transmitted from another base station, and judges that the control signal is received when the output of the intercepted signal after envelope detection exceeds a predetermined phase detection level in the comparator, The determined time is detected as the transmission timing of the interception signal, and the time difference between the transmission timing of the interception signal detected by the comparator and the transmission timing of the control signal of the own base station, that is, the transmission frame The transmission timing detected by the comparator of the interception signal at the reception input level and the actual transmission are measured by measuring the phase difference with the counter, and the base station has means for detecting the reception input level of the control signal of the other base station. The value obtained by subtracting the timing time difference from the transmission frame phase difference measured by the counter is used as the frame phase difference between the base stations, and the transmission timing of the own base station and the reception signal timing do not overlap and the timing difference is TDMA. / TDD or TDMA / FDD, one transmission slot length n (n
= 1, 2 ...) times so that the transmission timing of the control signal of the own base station is determined. 2. The duty ratio of the interception signal (TDMA / TD) is set so that the reception input level of the control signal from another base station is set to a value obtained by passing the envelope detection output of the received control signal through an integrator.
1/2 when the number of transmission slots is k in D system
k, the number of transmission slots is k in the TDMA / FDD system
In the case of, it is detected as a value multiplied by the reciprocal of 1 / k),
The frame phase synchronization method between base stations according to claim 1. 3. The received signal input level of the control signal from another base station is stabilized after sufficient time has elapsed from the start point of the pulse of the control signal after envelope detection of the received control signal. 2. The inter-base station frame phase synchronization method according to claim 1, wherein the level is detected as a pulse level at a time point.