JPH07203543A - Tdma frame synchronization method - Google Patents

Abstract

PURPOSE:To establish TDMA synchronization in spite of interference by setting a time when a signal is actually received and a reception time when the signal is inputted to a mutual synchronization means to different values capable of avoiding the collision of a transmission TDMA frame and calculating the time of actual transmission from the output of the mutual synchronization means. CONSTITUTION:A reception time offset setting means 102 detects the base station identification number from a reception signal and adds an offset quantity equivalent to the position of a slot transmitting a signal within the TDMA frame specified in advance to the reception time of the reception signal so as to obtain the comparing reference time of the TDMA frame phase of the reception signal. A transmission time offset setting means 103 adds an offset quantity equivalent to the position of a slot transmitting the signal within the TDMA frame of the transmission signal of its own station to the output of the nutual synchronization means 101 so as to obtain the signal transmission time of its own station. Then, a signal from another base satation is mutually synchronized based on the difference between the reception and transmission times and the offset time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to synchronizing TDMA frame phases of all base stations and mobile stations that can communicate with each other in a system in which a plurality of base stations perform wireless TDMA communication with a plurality of mobile stations. It is about the method.

[0002]

2. Description of the Related Art FIG. 6 is a diagram for comparing a state in which a TDMA frame is asynchronous and a state in which a TDMA frame is synchronized. FIG. 11A shows a state in which the TDMA frame is asynchronous, and at this time, four stations can communicate. However, it can be seen that the frequency utilization rate deteriorates because there are many times when no signal exists on the time axis. The figure (b) is TD
The state is shown in which the MA frames are synchronized, and six stations can communicate. As described above, in the state where the TDMA frame is synchronized, the frequency utilization rate is improved as compared with the state where the TDMA frame is asynchronous.

FIG. 7 is a schematic diagram showing a state in which a mobile station moves across a plurality of zones. In the figure, it is assumed that at time T1, the mobile station is performing wireless TDMA communication in zone 1 indicated by numeral 701 with base station 1 indicated by 711 in TDMA frame synchronization.

Next, at time T2, mobile station 703 moves and enters zone 2 indicated by numeral 702, and tries to communicate with base station 2 indicated by 712. At this time, at time T3, if the TDMA frame of the base station 1 and the TDMA frame of the base station 2 are not synchronized, the mobile station is
A frame synchronization must be reestablished. Base station 1
By synchronizing the TDMA frame of the base station 2 with that of the base station 2, the TDMA frame synchronization re-establishment with the base station 2 is instantaneously performed, and a quick zone switching is possible. Therefore, it is necessary to synchronize the TDMA frames of the base stations with each other.

FIG. 8 is a diagram showing the structure of the mutual synchronizing means. The variable frequency oscillating means 803 is a signal oscillating means capable of changing the oscillation frequency according to the input signal Y, and the frequency changes according to the output of the weighted average means 802.

It is assumed that there are n inputs of reception times of reception signals from other base stations. The output of the frequency variable oscillation means 803 becomes the signal transmission time of its own station as it is, and is also fed back to the phase comparison means 801-1 to 801-n and compared with the input of the reception time of the reception signal from another base station. To be done.

In the phase comparison means 801-1 to 801-n, the time difference between the reception time of the received signal from another base station and the signal transmission time of the own station is calculated, and this is calculated as T between the own station and the received signal.
It is a DMA frame phase difference. FIG. 9 is a supplementary explanatory diagram of the TDMA frame phase difference, and explains that the TDMA frame phase difference is the time difference between the transmission signal of the own station and the reception signal from each neighboring zone.

This TDMA frame phase difference signal is shown in FIG.
Is input to the means 802 for weighted averaging. FIG. 10 is a block diagram of the weighted average means 802. The TDMA frame phase difference signal for the reception time of the reception signal from the i-th other base station is φi.

Weight coefficient registers 805-1 to 805-n
Is a means for storing the weight for each TDMA frame phase difference signal, and for even averaging, the coefficient of each register is set to (1 / n). φi is a multiplier 804-1
The weighting coefficient is multiplied by 804-n and becomes the input Xi of the adder 806. The output Y of the adder 806 becomes an input to the frequency variable oscillation means 803 in FIG.

Although the mutual synchronization means of FIG. 8 is required to receive the reception time of the reception signal from another base station, these reception signals do not necessarily have to be signals dedicated to TDMA frame synchronization. FIG. 11 is a schematic diagram showing that there are many inputs from neighboring zones. In the figure, reference numerals 111 to 120 represent base stations and their zones 1 to 10, and reference numeral 121 represents mobile stations.

The signal transmitted from the zone 2 base station to the mobile station 121 in zone 2 can be used as an input of the mutual synchronization means at the zone 1 base station if it can be received. is there. Similarly, if it is possible to receive signals from zones 3 to 10, the number of inputs of the mutual synchronization means at the base station of zone 1 is nine.

FIG. 12 is an explanatory diagram of the absolute phase. A reference time is set for each TDMA frame transmission cycle unit, and the time difference between the reference time and the signal transmitted by station A is A
We will call it the absolute phase of the station. The absolute phase is used on the vertical axis in FIGS. 13 and 5.

FIG. 13 is a schematic diagram showing a state in which the mutual synchronizing means are synchronized. For ease of explanation, the weighted average is a uniform average and the number of stations is three. The vertical axis represents the absolute phase described in FIG. 12, and the horizontal axis represents the elapsed time. Since each base station does not have a TDMA frame phase which is a time reference common to each base station, each station cannot observe the absolute phase, and can detect only the relative phase difference between the stations.

At time 0, the ABC stations are in an asynchronous state, and there is a phase difference between the stations. At the beginning, station A reaches the phase correction time, the phase difference between stations B and C is evenly averaged, and the phase of its own station is corrected, the TDMA frame phase of station A becomes the phase of station B and that of station C. It is fixed in the middle.

Next, station B reaches the phase correction time, and in the same way, A
It is corrected between the station phase and the C station phase. After that, the phases are corrected in order, and after a lapse of a sufficient time, the phases of the stations are synchronized to perform transmission / reception with the same TDMA frame phase.

[0016]

DISCLOSURE OF THE INVENTION The conventional TDM described above
In the A-synchronization method, the same frequency is used for the transmission signal from each base station, and the wireless T is shared by a plurality of base stations in a time division manner.
When the above mutual synchronization means is used in the DMA communication system, there is an unfavorable problem that the phase difference cannot be detected when there is interference.

FIG. 14 is a diagram showing interference caused in the synchronization process of the mutual synchronization means. In the initially asynchronous state, there is no temporal overlap (interference) and it is possible to receive the TDMA signal, but when the mutual synchronization circuit is operated, the TDMA signal with a frequency of one wave and the temporal overlap is transmitted. As a result, interference occurs and the TDMA frame cannot be received. Therefore, the TDMA frame phase of the base station in which these interferences occur cannot be detected, and TDMA frame synchronization cannot be achieved.

It is an object of the present invention to solve the conventional problem that a TDMA frame cannot be received due to interference as described above, and to realize a means capable of establishing TDMA frame synchronization.

[0019]

According to the invention, the aforesaid problems are solved by the means defined in the claims.

That is, according to the present invention, in a radio communication system in which a plurality of base stations communicate with a plurality of mobile stations by the TDMA method, each base station transmits and receives a phase of a TDMA signal frame and a signal transmitted from another base station. The difference between the phase of the TDMA signal frame and the phase difference of the TDMA frame between the own station and at least one other base station,

Each base station repeats the operation of determining the frame phase of the TDMA signal to be transmitted by the own station, so that the TDMA frame having mutual synchronization means for synchronizing the frames of the TDMA signals transmitted and received by all the base stations. In the synchronization method, a base station identification number corresponding to each base station and a slot in which a signal in a TDMA frame is to be received are predetermined for each base station,

Each base station transmits by including the base station identification number in the transmission signal, detects the base station identification number from the reception signal from another base station, and responds to the base station identification number. By adding or subtracting an offset amount corresponding to the position of the slot in which the signal in the TDMA frame is to be transmitted, to the reception time of the reception signal from another base station, the TDMA frame phase of the reception signal A reception time offset setting means as a comparison reference time,

An offset amount corresponding to the position of the slot in which the signal in the TDMA frame of the transmission signal of the own station, which is predetermined in the own station, is added to or subtracted from the output of the mutual synchronization means to transmit the signal of the own station. And a transmission time offset setting means for setting a time, and a signal from the other base station is set based on the difference between the time when the reception time is offset and the time when the transmission time of the own station transmission signal is offset. A TDMA frame synchronization method configured to perform synchronization.

[0024]

According to the present invention, by the above means, the time when the signal is actually received and the time when the signal is input to the mutual synchronization means can be avoided from temporal collision between the TDMA frame transmitted by the own station and the TDMA frame transmitted by another station. Since it is set to another value like this and each base station can calculate the time of actual transmission from the output of the mutual synchronization means, regardless of interference,
TDMA frame synchronization can be established. Less than,
The operation and the like of the present invention will be described in detail based on examples.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the construction of an embodiment of the present invention, showing the basic construction of the present invention. That is,
The present embodiment provides a method of establishing TDMA frame phase synchronization with the configuration shown in FIG. 1, which is characterized in that the reception time of a reception signal from another base station is synchronized with the mutual synchronization means 101.
The reception time offset setting means 102-1 to 102- for adding or subtracting an offset determined corresponding to the base station identification number detected from the received signal to the input stage before
having n,

The transmission time offset setting means 103 for adding or subtracting an offset determined in advance corresponding to the base station identification number of the self station is provided before the time when the self station outputs the time to be transmitted. This is different from the conventional technique in that the reception time offset setting means 102-1 to 102-n and the transmission time offset setting means 103 are added.

FIG. 2 is a diagram showing the configuration of the reception time offset setting means and the transmission time offset setting means. The structure of the reception time offset setting means 102 is shown in FIG. The base station identification number is compared with the offset table 104 to output an offset value corresponding to the base station number, and the adder 105 adds the offset value to the received TDMA frame phase.

By setting the offset value stored in advance in the offset table 104 as TDMA frame time length × integer, interference of TDMA frames can be avoided. FIG. 3 is a diagram showing that the transmission time of each base station can be controlled on the time axis by setting an integer. By using the value of the base station identification number as it is as the integer value, all the TDMA signals can be arranged in the order of the base station identification number on the time axis.

By setting an integer value to the remainder of the base station identification number divided by n, the base station identification numbers 0 to n are set.
The transmission signals up to -1 are arranged in numerical order on the time axis, and the transmission signal of the base station identification number n and the transmission signal of the base station identification number 0 are at the same time and the transmission signal of the base station identification number n + 1 and the base station identification number. It is also possible to set one transmission signal at the same time.

Interference will occur if the signals are transmitted at the same timing, but if the base station identification number 0 and the base station identification number n are sufficiently separated, the signal power will be small and the interference will be sufficiently small to cause no problem. Thus, the value of the integer is of a nature that depends on the design of the system.

The structure of the transmission time offset setting means 103 is shown in FIG. 2 (b). Using the offset table used in the reception time offset setting means, the offset amount for the base station identification number of the own station is fixedly output from the transmission time offset 106, and added by the adder 105 to the output of the mutual synchronization means, It is the time when the station should transmit.

FIG. 4 is a flow chart showing the processing of the base station, showing the operation of the TDMA frame synchronization method according to this embodiment. As shown in the figure, each base station always monitors whether or not it is the transmission time of its own station, and when it is not the transmission time of its own station, monitors the received signal from another station.

When there is a received signal, the received time is stored, the offset amount for the received time is calculated from the base station identification number detected from the received signal, and added to the received time. The reception time to which the offset amount is added is stored, and the state returns to the state in which the own station transmission time is monitored again. Generally, signals from a plurality of base stations are received between the transmission time of the own station and the transmission time of the next own station.

When the transmission time of the own station is reached, the offset amount of the own station is added to the transmission time of the own station before transmission, and subsequently, the respective reception times stored are sequentially read out, and the reception in which the offset amount is added is received. The time difference between the time and the transmission time of the own station to which the offset amount is added is calculated and used as the phase difference with each received signal. After that, each phase difference is averaged, the TDMA frame period of the local station is temporarily increased or decreased, each reception memory is reset, and the state returns to the state of monitoring the local station transmission time again.

As the offset amount, any value that is an integral multiple of the slot time length can be used if it is uniquely determined as a function of each base station identification number. Hereinafter, the wireless TDMA communication in which the transmission signal includes the base station identification number will be described as an example.
Consider a case where the phase offset is set to, for example, slot length × base station identification number. When the slot length is L, the phase offset of each station is as shown in "Table 1". Each station has such an offset table and adds the offset amount to the phase of the received signal.

[0036]

[Table 1]

Based on the TDMA frame phase of its own station,
The phase difference is detected by observing the received signals from other stations. now,
If a received signal is detected from station C at time tc, this tc is directly input to the mutual synchronization circuit in the conventional method. However, in the present embodiment, referring to "Table 1", the received signal is received. The offset amount 2L corresponding to the base station identification number 2 included in is calculated, and this offset amount is added (tc
+ 2L) is input to the mutual synchronization circuit. Similarly, signals from other stations are sequentially received and input to the mutual synchronization circuit.

By calculating the offset amount each time from the base station identification number included in the received signal, it is possible to reduce the amount of memory installed in the station. FIG. 5 shows an example of the phase synchronization process in the present invention. For ease of explanation, this figure shows the case where the weighted average is a uniform weight and the number of stations is three. The system on the vertical axis is the absolute phase seen from the outside. Since each base station does not have a TDMA frame phase which is a time reference common to each base station, each station cannot observe the absolute phase, and can detect only the relative phase difference between the stations.

First, station A reaches the phase correction time, and station B
The phase difference with the C station is detected. The offset amount L determined from the base station identification number included in the received signal is added to the phase difference from the B station, and the offset amount 0 of the own station is subtracted. Then C
The offset amount 2L determined from the base station identification number included in the received signal is added to the phase difference with the station, and the offset amount 0 of the own station is subtracted. In FIG. 5, the virtual phase considering the offset is shown by a broken line. By taking the average value of these two virtual phases, the phase of station A changes to the middle of the two broken lines.

Next, station B reaches the phase correction time, and stations A and C
Detect the phase difference with the station. Offset amount 0 determined from the base station identification number including the received signal in the phase difference with the A station
Is added and the offset amount L of its own station is subtracted. Next, the offset amount 2L determined from the base station identification number included in the received signal is added to the phase difference with the C station, and the offset amount L of the own station is subtracted. The phase of station B changes to the middle of the two dashed lines.

Similarly, the phase correction is continued, and after a sufficient time elapses, each station settles in a phase separated by a time width L.
In this state, it is not necessary to receive the TDMA frame from another station at the same time when the TDMA frame of the own station is transmitted, and it is possible to establish the TDMA frame phase synchronization using the mutual synchronization means.

[0042]

As described above, according to the present invention,
Radio T that uses only one frequency for transmission signals from each base station
Even when the mutual synchronization means is used in the DMA communication system, the phase difference can be detected without causing interference and TDMA frame synchronization can be achieved.

Further, normally, the wireless TDMA communication is performed by the TDM.
After the A frame synchronization is established, the transmission slot of each base station is reallocated (so-called transmission slot segregation) with the intention of avoiding the transmission TDMA slot from interfering with other transmission TDMA slots. According to TDM
Segregation can be performed in the A frame synchronization pull-in process.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a reception time offset setting means and a transmission time offset setting means.

FIG. 3 is a diagram illustrating a difference in signal transmission state due to a difference in offset setting.

FIG. 4 is a flowchart showing processing of a base station.

FIG. 5 is a diagram showing a phase synchronization process of the present invention.

FIG. 6 is a diagram comparing the synchronous and asynchronous states of TDMA frames.

FIG. 7 is a schematic diagram showing a state in which a mobile station moves across a plurality of zones.

FIG. 8 is a diagram showing a configuration of mutual synchronization means.

FIG. 9 is a diagram illustrating a TDMA frame phase difference.

FIG. 10 is a diagram showing a configuration of a means for performing weighted averaging.

FIG. 11 is a schematic diagram showing that there are many inputs from neighboring zones.

FIG. 12 is an explanatory diagram of an absolute phase.

FIG. 13 is a schematic diagram showing a state in which mutual synchronization means are synchronized.

FIG. 14 is a diagram showing interference occurring in the synchronization process of the mutual synchronization means.

[Explanation of symbols]

101 Mutual synchronization means 102-1 to 102-n Reception time offset setting means 103 Transmission time offset setting means 104 Offset table 105 Adder 106 Transmission time offset 801-1 to 801-n Phase comparison means 802 Weighted average means 803 Frequency variable Transmission means 804-1 to 804-n Multiplier 805-1 to 805-n Weighting coefficient register 806 Adder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshinori Tanaka 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A plurality of base stations comprises a plurality of mobile stations and a TDMA.
Each base station of a wireless communication system that performs communication according to the method detects the difference between the phase of a TDMA signal frame transmitted and received and the phase of a TDMA signal frame transmitted from another base station, and detects at least one other base station. TD between station and own station
TDMA to be transmitted by the own station based on the phase difference of the MA frame
In a TDMA frame synchronization method having mutual synchronization means for performing frame synchronization of TDMA signals transmitted and received by all base stations by repeating the operation of determining the frame phase of a signal, each base station A base station identification number corresponding to the base station,
A slot for receiving a signal in a TDMA frame is predetermined, and each base station transmits the transmission signal by including the base station identification number, and at the same time, the base station identifies from the reception signal from another base station. Number is detected and an offset amount corresponding to the position of a slot in which a signal in a TDMA frame that is predetermined corresponding to the base station identification number is transmitted is added to the reception time of a reception signal from another base station or Subtract the T of the received signal
Reception time offset setting means for setting a comparison reference time of the DMA frame phase, and TDMA of a transmission signal of the own station, which is predetermined in the own station.
A transmission time offset setting unit that adds or subtracts an offset amount corresponding to the position of a slot in which a signal in a frame is to be transmitted to the mutual synchronization unit output to obtain the signal transmission time of the local station; and TDM characterized by mutual synchronization based on the difference between the time when the reception time of the signal from the base station is offset and the time when the transmission time of the local station transmission signal is offset
A frame synchronization method.