JPH0473898B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] In the TDMA communication system that communicates between a master station and a plurality of slave stations using a time division method, the clock signal phase at the time of initial synchronization establishment, periodic maintenance, etc. During adjustment, the master station calculates each error based on the clock information and carrier wave information from the slave station, reports the error information to the slave station, and the slave station adjusts the clock signal phase according to the error information. By adjusting the transmission carrier frequency, the clock signal phase at the slave station can be maintained accurately even when the clock signal frequency is close to the transmission carrier frequency.

[Industrial application field]

The present invention relates to a TDMA communication system that performs communication between a master station and a plurality of slave stations in a time-division manner.

In the TDMA communication system that performs time-division multidirectional communication between a master station and multiple slave stations, the master station is equipped with a high-precision oscillator to stabilize the frequency of the clock signal and transmission carrier wave, and The slave station is provided with a relatively inexpensive oscillator to generate a clock signal that is phase synchronized with the clock signal from the master station. There is a demand for stabilization of the clock signal in such slave stations.

[Prior Art] As shown in FIG. As shown in figure a,
Signals a, b, c, ... addressed to each slave station A, B, C, ...N
n is transmitted using the same carrier frequency with a guard time.

Each slave station A, B, C, ...N receives signals a, b, c, ...n in its own slave station allocated time slot,
For example, as shown in b, the slave station A receives the signal a in the own slave station allocated time period after the propagation delay time τa,
As shown in c, the slave station B receives the signal b in its own assigned time slot after a propagation delay time τb. Similarly, as shown in d, the slave station N receives the signal n in its own assigned time slot after a propagation delay time τn.

Each slave station A, B, C, . Also, each slave station A, B, C,...N
are based on the frame synchronization signal (reference burst signal at the beginning of the frame), and the propagation delay times τa, τb,
...It is transmitted at the transmission timing corrected by τn, so that the signals from each slave station A, B, C, ...N are received in an orderly line on the time axis of the master station, as in a. It is intended to be controlled.

As a result, the signals from each slave station A, B, C, ...N can be received by the master station without overlapping.
Communication can be performed between the master station and each slave station A, B, C, . . . N using a time division method.

[Problem that the invention seeks to solve]

At the time of establishing initial synchronization, it is practically difficult to calculate the delay time setting of the delay equalizer based on the propagation delay time with the master station. Therefore, a burst signal is transmitted at a predetermined timing based on a reference burst from the master station, the master station determines whether or not this burst signal has been received at the predetermined timing, and the determination information is transmitted to the slave station. The burst signal is then adjusted so that the burst signal can be transmitted at a predetermined timing. In order to establish such initial synchronization, one channel is commonly allocated to each slave station, and initial synchronization is established for each slave station in sequence.

Also, compared to the frequency of the clock signal, the frequency of the transmission carrier wave is generally selected to be very high. In that case, even if the frequency of the transmitted carrier wave varies somewhat, the effect on the clock signal phase can be ignored. However, if the frequency of the clock signal is selected to be close to the frequency of the transmitted carrier wave, the clock signal phase will vary when the frequency of the transmitted carrier wave changes. In order to prevent this, it would be sufficient to provide a high-precision oscillator in the slave station, but since a high-precision oscillator is expensive, this poses an economical problem.

The present invention enables stable communication by adjusting the clock signal phase and the transmission carrier frequency at the time of initial synchronization establishment, periodic maintenance, etc., even if an oscillator with the same accuracy as the conventional one is used. The purpose is to

[Means for solving problems]

The TDMA communication system of the present invention performs communication between a master station and a plurality of slave stations in a time-division manner, and adjusts the clock signal phase and transmission carrier frequency of the slave stations. I will explain.

The master station 1 transmits to each of the plurality of slave stations 2 in a time-division manner, and the slave stations 2 transmit to the master station 1 in synchronization with the clock signal from the master station 1 during their own assigned time slots.

When initial synchronization is established or during periodic maintenance, the slave station 2 transmits a first synchronization pull-in signal with a short time length and a second synchronization pull-in signal with a long time length within the auxiliary signal allocation time slot, and the master station 1, so that the first synchronization pull-in signal can be received at approximately the center of the auxiliary signal allocation time zone, and the second synchronization pull-in signal is within the auxiliary signal allocation time zone. , transmits the error information to the slave station 2, and extracts clock signal phase information and transmission carrier frequency information from the synchronization pull-in signal, and the slave station clock signal phase and slave station transmission carrier frequency determining section 3 Error information with respect to the reference value is obtained and this error information is transmitted to the slave station 2.

The slave station 2 controls the transmission timing according to the error information from the master station 1, controls the phase of the clock signal by the clock signal phase control section 4, and controls the transmission carrier wave by the transmission carrier frequency control section 5. Control frequency.

[Effect]

When establishing initial synchronization or during periodic maintenance, when slave station 2 transmits a short first synchronization pull-in signal within the auxiliary signal allocation time slot, master station 1 receives this first synchronization pull-in signal. Then, error information indicating the deviation from the center within the auxiliary signal allocation time slot is transmitted to the slave station 2. The slave station 2 adjusts the transmission timing according to this error information. Next, the slave station 2 transmits a second synchronization pull-in signal with a longer time length within the auxiliary time allocation time slot. The master station 1 receives this second synchronization pull-in signal and transmits to the slave station 2 error information indicating a deviation when the auxiliary signal does not fall within the allocated time period. The slave station 2 adjusts the transmission timing according to this error information.

In addition, the master station 1 extracts clock signal phase information and transmission carrier frequency information from the first and second synchronization pull-in signals from the slave station 2, and performs a slave station clock signal phase and slave station transmission carrier frequency determination section. In step 3, error information with respect to the reference value is obtained and this error information is transmitted to the slave station 2. In accordance with this error information, the slave station controls the phase of the clock signal using the clock signal phase control section 4, and controls the frequency of the transmission carrier using the transmission carrier frequency control section 5. In other words, the slave station 2 is provided with an oscillator with lower frequency stability than the oscillator of the master station 1, and even if the oscillation frequency of the slave station 2's oscillator deviates due to changes over time, it can be controlled to return to the correct frequency. , it is possible to stabilize TDMA communication.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram of the main parts of the master station according to the embodiment of the present invention, in which 11 is a demodulator, 12 is a separation section, 13 is a phase comparator, 14 is a phase error detection section, and 15 is a sample hold section (S /H), 16 is an A/D converter,
17 is a band pass filter, 18 is a frequency detection section, 19 is a sample hold section (S/H), 20
21 is an A/D converter, 21 is a control circuit, 22 is a switching circuit, and 23 is a multiplexing section. The configuration excluding the multiplexing section 23 corresponds to the slave station clock signal phase and slave station transmission carrier frequency determination section 3 in FIG.

A modulated signal from a slave station is applied to a demodulator 11 and a bandpass filter 17, demodulated by the demodulator 11, and applied to a separation section 12. At the time of initial synchronization establishment or periodic maintenance, the clock signal separated by the separation section 12 is applied to the phase comparator 13, where a phase comparison with the basic clock signal is performed.
The comparison output is applied to the phase error detection section 14, and a phase error signal is output. This phase error signal is sampled and held in a sample and hold section 15, converted into a digital signal by an A/D converter 16, and applied to a switching circuit 22.

In addition, the frequency component of the slave station transmission carrier wave is extracted from the modulated signal by a bandpass filter 17 having a pass band centered on the slave station transmission carrier frequency _f0 , and is added to the frequency detection section 18 to determine the slave station transmission carrier frequency. is detected, and a frequency error signal is output by comparison with a reference value. This frequency error signal is sampled and held by a sample and hold section 19, converted into a digital signal by an A/D converter 20, and applied to a switching circuit 22.

The control circuit 21 controls the separation section 12 to separate data and clock signals from the demodulated output signal, adds a sample-and-hold timing signal to the sample-and-hold sections 15 and 19, and also controls the switching circuit 22.
It has the function of adding a switching signal to the The switching circuit 22 alternately switches between the clock signal phase error signal and the carrier frequency error signal output from the A/D converters 16 and 20 for each frame, and applies the signals to the multiplexing section 23, for example.

The multiplexing unit 23 multiplexes data and the like to be sent to the slave station, and an error signal is sent to the slave station where initial synchronization is being established.

FIG. 3 is a block diagram of the main parts of the slave station according to the embodiment of the present invention, in which numeral 31 is a multiplexing section, 32 is a synchronization control section,
33 is a switching circuit, 34 is a modulator, 35 is a carrier wave generating section, 36 is a demodulator, 37 is a synchronizing circuit, 38 is a separating section, and 39 is a clock signal generating section. This clock signal generation section 39 has a function of generating a clock signal that is phase-synchronized with a clock signal extracted from a signal from the master station, and also has a function of performing phase control based on a phase error signal from the master station. The clock signal phase control section 4 in FIG.
corresponds to Further, the carrier generation section 35 has a function of controlling the transmission carrier frequency based on the frequency error signal from the master station, and corresponds to the transmission carrier wave control section 5 in FIG. 1.

The modulated signal from the master station is demodulated by a demodulator 36, frame synchronization and bit synchronization are achieved by a synchronization circuit 37, and data in a predetermined time period is separated by a separation section 38. At the time of initial synchronization establishment or periodic maintenance, the phase error signal of the clock signal from the master station and the frequency error signal of the transmitted carrier wave are separated, and the phase error signal is added to the clock signal generator 39 to control the phase of the clock signal. The frequency error signal is applied to the carrier wave generator 35 to control the carrier wave frequency.

The clock signal output from the clock signal generator 39 is sent to the multiplexer 31 via the synchronization controller 32.
and is added to the switching circuit 33. Synchronization pull-in control signals ACQ1 and ACQ2 for transmitting burst data of different time lengths are applied to the synchronization control unit 32 at the time of initial synchronization establishment or periodic maintenance. This first synchronization pull-in control signal ACQ1 sends out a synchronization pull-in signal with a very short time period compared to the time period allocated for establishing initial synchronization, and the second synchronization pull-in control signal ACQ2 sends out a synchronization pull-in signal with a very short time period compared to the time period allocated for establishing initial synchronization. Control is performed to send out a synchronization pull-in signal with a time length slightly shorter than the time slot allocated for synchronization establishment.

FIG. 4 is an explanatory diagram of the operation of the embodiment of the present invention,
If a signal with the frame structure shown in a is to be transmitted and received, the time period allocated to the synchronization signal at the beginning of the frame and other auxiliary signals is the time period commonly used at the time of initial synchronization establishment or periodic maintenance in each slave station. Assuming that the auxiliary signal allocation time period for that purpose is shown in b, initially, by applying the first synchronization pull-in control signal ACQ1 to the synchronization control unit 32, the auxiliary signal is allocated as shown in c. Synchronization pull-in signal ACQ with a very short time compared to the signal allocation time zone
Send out. Note that GT is a guard time added before and after the synchronization pull-in signal ACQ.

The master station receives this synchronization pull-in signal ACQ,
The shift from the center is notified so that the master station can receive the reception auxiliary signal almost at the center of the allocated time period. The slave station sends a synchronization pull-in signal according to the information.
Adjust the ACQ sending timing. When the adjustment is made so that the receiving auxiliary signal can be received at approximately the center of the allocated time period at the master station, the second synchronization pull-in control signal ACQ2 is applied to the synchronization control unit 32, and as shown in d, the auxiliary signal Sends a synchronization pull-in signal ACQ with a time length slightly shorter than the signal allocation time period. In this case, the guard time GT is approximately several bits.
Then, at the master station, this synchronization pull-in signal ACQ is
The slave station is notified of the shift so that it falls within the reception auxiliary signal allocation time slot. The slave station thereby adjusts the sending timing of the synchronization pull-in signal ACQ.
Therefore, the slave station can set the transmission timing based on the synchronization signal from the master station.

This synchronization pull-in signal ACQ is data of "1" and "0" alternately, as shown in e, based on the clock signal from the clock signal generator 39. Pull-in signal ACQ
The separating section 12 separates the clock signal component and applies it to the phase comparator 13, and as described above, the phase error signal of the clock signal is applied to the multiplexing section 23 via the switching circuit 22, and the clock signal component is sent to the slave station. The phase error signal of the signal is inserted into the auxiliary signal time period or the order wire time period and transmitted.

In the slave station, as described above, the separation section 38 separates this phase error signal and applies it to the clock signal generation section 39 to control the phase of the clock signal.

In addition, in the master station, as mentioned above, the frequency error signal of the slave station transmission carrier is added to the multiplexing section 23 via the switching circuit 22, and the frequency error signal is transmitted to the slave station in the time period of the auxiliary signal or in the order wire. Insert it into the time zone and send it out.

In the slave station, as described above, the separation section 38 separates this frequency error signal and applies it to the carrier wave generation section 35 to adjust the frequency of the transmission carrier wave.

In the above embodiment, the phase error signal of the clock signal and the frequency error signal of the transmitted carrier wave are:
Although this shows a case where these error signals are transmitted in different frames, it is of course possible to transmit these error signals within the same frame. Furthermore, since the frequency of the transmitted carrier wave of the slave station generally varies only slightly, it only needs to be adjusted during regular maintenance once a day or every few days, and the processing load on the master station does not become particularly large.

〔Effect of the invention〕

As explained above, the present invention can be used at the time of initial synchronization establishment or during periodic maintenance approximately once a day or every few days.
The slave station 2 transmits the first synchronization pull-in signal with a short time length to the master station 1 within the auxiliary signal allocation time period, and then transmits the second synchronization pull-in signal with a long time length.
The master station 1 transmits error information to the slave so that the first synchronization pull-in signal can be received in the center of the auxiliary signal allocation time period, and the second synchronization pull-in signal can be received within the auxiliary signal allocation time zone. The master station 1 transmits the information to the station 2 to adjust the transmission timing at the slave station 2, and the master station 1
extracting clock signal phase information and transmission carrier frequency information from the first and second synchronization pull-in signals;
Error information with respect to the reference value is determined and transmitted to the slave station 2, and the slave station 2 adjusts the phase of the clock signal in the clock signal phase control section 4 according to the error information, and adjusts the phase of the clock signal according to the frequency error information of the transmitted carrier wave. The transmission carrier frequency control section 5 adjusts the frequency of the transmission carrier wave, and even if the frequency stability of the transmission carrier wave of the slave station 2 is lower than that of the master station 1, the frequency of the transmission carrier wave of the slave station 2 is adjusted. Since the clock signal phase can be adjusted to the reference value, the clock signal phase is also stabilized, and therefore, TDMA communication between the master station 1 and the plurality of slave stations 2 can be stabilized.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a block diagram of the main parts of a master station according to an embodiment of the invention, Fig. 3 is a block diagram of main parts of a slave station according to an embodiment of the invention, and Fig. 4 5 is an explanatory diagram of the operation of the embodiment of the present invention, FIG. 5 is an explanatory diagram of the multidirectional communication network, and FIG. 6 is an explanatory diagram of the operation of the multidirectional communication network. Reference numeral 1 designates a master station, 2 a slave station, 3 a slave station clock signal phase and slave station transmission carrier frequency determination section, 4 a clock signal phase control section, and 5 a transmission carrier frequency control section.

Claims (1)

[Scope of Claims] 1 Transmission is performed from a master station 1 to each of a plurality of slave stations 2 in a time-division manner, and each slave station 2 receives its own slave station assignment in synchronization with a clock signal from the master station 1. In the TDMA communication method, which is transmitted to the master station 1 during the time period, when initial synchronization is established or during periodic maintenance, a first synchronization pull-in signal with a short time length and a second synchronization signal with a long time length are sent from the slave station 2. The master station 1 transmits the first synchronization pull-in signal within the auxiliary signal allocation time slot, and transmits the first synchronization pull-in signal in a substantially central part of the auxiliary signal allocation time slot. The slave station 2
At the same time, the clock signal phase information and transmission carrier frequency information are extracted from the synchronization pull-in signal, and the slave station clock signal phase and slave station transmission carrier frequency determination section 3 determines the error with respect to the reference value. information, and transmits the error information to the slave station 2.
The slave station 2 controls the transmission timing according to the error information from the master station 1, and controls the clock signal phase and transmission timing by the clock signal phase control section 4 and the transmission carrier frequency control section 5. A TDMA communication method that is characterized by controlling each carrier frequency.