JPS592454A - Time division omnidirectional mutiplex communication system - Google Patents

Abstract

PURPOSE:To make the initial adjustment easy at the stage of installation while keeping the effective use of frequency, by adding a preamble signal to only a specific burst before an information burst, in a time division omnidirectional multiplex communication system. CONSTITUTION:First, a distance between a master station and a slave station is obtained, the distance between an antenna and a radio equipment is obtained, the transmission timing of the slave station is adjusted coarsely, only a communication telephone burst is transmitted for communication. The master station compares the phase of a clock 17 extracted for the burst while communication with a sample pulse 13 sampling the main data burst, transfers the result to the slave station, the difference information of the transmission timing is transferred to the slave station, where the transmitted timing is tuned minutely. Further, when the main signal burst is transmitted, the main signal burst is made coincident with the timing of the master station.

Description

[Detailed Description of the Invention] The present invention relates to a time division multiplex communication device, and in particular, in order to effectively utilize frequencies, insertion of useless bits is minimized, and communication telephone calls can be made even during the initial construction stage. The present invention aims to provide a time-division multi-directional multiplex blood transmission system for terrestrial fixed radio, which facilitates burst timing adjustment from a slave station to a master station.

FIG. 1 shows the configuration of this type of communication system.

A master station 1 communicates with a plurality of slave stations 4 scattered in an area within a certain angular range by covering them with a wideband beam antenna 2. From the master station 1, a frame synchronization signal and a signal for each slave station are time-division multiplexed and sent to the slave stations in broadcast mode, as in general digital fixed radio. Each slave station extracts only the signal destined for itself from the received signal train.

Conversely, in the case of a slave station, the frame synchronization signal from the master station is used as a time reference, and transmission is performed intermittently only in the time domain allocated to the own station, as shown in FIG. In this way, as shown in FIG. 6, the signals are arranged in a line on the time axis at the master station receiver as if they were received from one station. Communication is performed by the master station separating and extracting signals from each slave station.

As described above, two types of methods are considered for time division multiple access for accessing one master station from a plurality of slave stations: the first-order method.

■ What is the method for transmitting bursts from the slave station at the master station? For example, by observing them with an oscilloscope and adjusting the transmission timing at the slave station on a per-bit basis and in bit units to match the timing required by the master station's receiver.

■ When configuring a burst to be transmitted from a slave station, a training pattern called a preamble is added before the signal section that is originally intended to be sent, and the training pattern until the synchronization circuit of the carrier and clock of the master station receiver starts up, and the start of the signal section is added. The slave station transmits the data with a rough transmission timing adjustment that does not overlap with the bursts of other stations, and the master station performs carrier synchronization and clock synchronization if necessary on a burst-by-burst basis. By establishing frame synchronization, the signals of each slave station are separated and extracted.

Comparing these methods, method Ⅰ is useless, has few problems, and does not require much increase in the clock rate of the wireless transmission path compared to the information bit rate, so it suppresses the spread of the spectrum to a certain amount. It has the advantage of being able to

This shows that the frequency between adjacent channels can be narrowed compared to method (2), which is desirable from the point of view of effective use of nine frequencies. But on the other hand.

During the construction stage of this system, there are inconveniences such as the signal from the slave station cannot be demodulated and the telephone for communication cannot be used until the transmission timing adjustment to the master station is completed.

On the contrary, method (2) synchronizes on the receiving side in burst units, so it has the advantage that communication can be performed automatically with only rough positioning calculated from the distance on the map. However, since extra signals such as a preamble and a unique word are added in addition to the information bits, the clock rate of the wireless transmission path becomes considerably higher than the information bit rate.

It can be said that it is inferior in terms of effective frequency utilization.

The present invention is characterized by combining the advantages of both. FIG. 4 shows an embodiment of a frame configuration diagram from the slave station to the master station.

Assuming that there are eight slave stations, A to H, the main signal bursts A to H are sent out from the slave stations without a preamble signal.

On the other hand, regarding the contact telephone burst, the slave station assigned according to the occasional call situation adds a preamble signal PAS and a unique word signal UWS serving as a frame mark before the information bit and sends it out.

FIG. 5 shows a block diagram of the main station receiver after the demodulator.

When the output signal 16 of the demodulator 5 is an A-H main signal burst, the sample circuit 6 uses the same clock as the transmitting side.
1"", °"O°゛ was determined.

The decompression buffer memory 11 separates the signal into signals for each slave station. At the time of a contact telephone burst, the demodulator output signal is the clock extracted by the clock extraction circuit 7, and the sampling circuit 8 outputs the signal at 1111.degree. IIQ+'' is determined.The preamble signal PAS is.

The clock is added for the necessary time until the clock extraction circuit 7 is synchronized. The sampled data 22 is sent to the decompression buffer memory 1 after a unique word detection circuit 9 finds a unique word indicating the start position of the information portion.
Written to 0. The unique word gate pulse 24 is used to determine whether the timing desired by the master station is roughly within the range, and has a tolerance range of about ±2 to 3 bits. When the expansion buffer memory 10 is read out using the read pulse 48 of the master station, the contact telephone signal is separated.

Next, in order to specifically explain the effectiveness of the present invention, a working procedure for synchronizing the timing of burst transmission from a slave station to a master station during the construction stage of a time division multiplex communication system according to the present invention will be described.

First, find the distance between the master station and slave station from Map 2.

By calculating the distance from each station's radio to the antenna, you can roughly predict the correct timing. Therefore, the transmission timing of the slave station is roughly adjusted and first only the contact telephone burst is transmitted. Since contact telephone bursts are synchronized with bursts, it is possible to receive them while allowing arrival timing errors in the overlay bits, so if the initial rough adjustment calculations are approximately correct, the communication between the master station and the slave stations can be made from the beginning. You will be able to make calls.

Therefore, while making a call, the result of a phase comparison between the extracted clock 17 of this burst and the same sample pulse 13 used on the master station transmitting side used to sample the main data burst is transferred to the slave station, and the unique word arrival time position and There is an original timing for sending out the main signal burst.

The information on the difference between the desired position and the desired position is transferred to the slave station, and the slave station finely adjusts the transmission timing either manually or automatically.

If you send out the main signal burst after this, the contact telephone burst and the main signal burst will originally have the same clock.

Because they are made from the same frame counter.

The main signal burst coincides with the timing that should be used as the master station.

In this method, although there are wasted bits due to the addition of preamble signal imma to the contact telephone burst, it is quite small considering the overall increase rate including the main signal, and while maintaining the effective use of nine frequencies, the construction This has the advantage that the initial stage adjustment is easier than in the conventional example.

[Brief explanation of drawings]

Figure 1 is a block diagram of a multiplex transmission system (time division multiplexing for fixed wireless), Figure 2 is a transmission burst diagram of each slave station, Figure 5 is a reception burst diagram of the master station, and Figure 4 is a diagram of the transmission burst diagram of the present invention. FIG. 3 is a diagram showing the configuration of a frame from a slave station to a master station according to an embodiment. FIG. 5 is a block diagram of the demodulator and subsequent parts in the master station receiver. 5: Demodulator, 6: Sample circuit, 7: Clock extraction circuit, 8: Sample circuit, 9: Unique word detection circuit, 1
0: Extendable horn memory. 11: Extension buffer memory, 13: Sample pulse, 14: Write timing pulse, 15: Read timing pulse, 17: Extracted clock pulse, 1
8: Read pulse. 19: Post-sample data, 20: Main signal data for A-H stations, 21: Contact phone information, 22: Post-sample data,
23: Write timing pulse, 24: Unique word 1"7'-)/"Lune. Figure 2 Figure 3

Claims (1)

[Claims] 1. The master station transmits time-division multiplexed continuous wave mode to each slave station, and each slave station transmits intermittently in a time-division multiplexed continuous wave mode so that when it reaches the master station, it becomes a line of time-division signals. In a multidirectional multiplex communication system that transmits information to The main signal burst is sent without a preamble signal, and at the master station, after demodulation, the burst with a preamble is used to write into the expansion memory using the clock extracted by the clock extraction circuit, and the main signal burst without a preamble signal is sent out. A time-division multidirectional multiplex communication system configured to sample at the same clock as the transmission from the master station and write data to the expansion memory.