JPS5850063B2 - Unique word detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting unique word signals necessary for establishing character synchronization and frame synchronization in a time division multiple access communication system.

In conventional time division multiple access communication systems, each station's transmission burst includes a prefix part and an information part.

One of these stations is designated as a mask station, and the other stations are designated as slave stations.

FIG. 1 is a format diagram showing an example of the format of a burst transmitted by each station.

The burst from the mask station can locate the burst anywhere in the time frame, but in the figure A is designated as the mask station and B and C are each designated as the two slave stations.

Burst is guard time Gt1 carrier regeneration bit b
Bit timing reproduction bit bb, key C) Consists of a unique word bu (hereinafter referred to as data unique word) and information bit bm for establishing Yarakuta synchronization.

In order to synchronize the communication system so that the bursts of different stations do not overlap, that is, to establish and maintain frame synchronization, the mask station sends a unique word (hereinafter referred to as the reference unique word) consisting of a special pattern for that purpose. is sent.

FIG. 2 is a format diagram showing another example of the format of the burst transmitted by each station.

In Figure 1, the format of the transmitted burst is the same as that of other slave stations, except that the mask station's unique word is the reference unique word, whereas in Figure 2, the mask station does not send any information part. The case is shown in which the station is a synchronous control only station that sends only the prefix part containing the reference unique word (indicated by the shaded area in the figure).

FIG. 3 is a block wiring diagram showing an example of a slave station device in a conventional time division multiple access communication system. In the figure, 1 is a demodulated input bit string, 2 is a data unique word detector, and 3 is this data unique word detector. O due to the output of the word detector
A flip-flop is set through the R-gate 4, 5 is an AND gate driven by the output of this flip-flop 3 and the local clock power 6 of that station operating at the transmitted bit rate, 7 is an AND gate of this AND gate 5. 8 is a station identifier; 9 is an AND gate between the signal from this station identifier and the output of the delay counter T; 10 is the A flip-flop 11 is set by the output of an AND gate 9; an AND gate 11 is driven by the output of this flip-flop 10 and a local clock 12;
3 is an address counter driven to 1 by the output of this AND gate 11, 14 is a reception buffer memory, 15 is a central processing unit, 16 is a reception interrupt signal given to this central processing unit by the address counter 13, and 17 is the input mentioned above. A reference unique word detector detects a reference unique word from signal 1; 18 is a flip-flop set by the output of this reference unique word detector; 19 is an AND driven by the output of this flip-flop 18 and a local clock signal 20; 21 is a delay counter that delays the output of this AND gate 19 until the transmission timing of the own station's burst; 22 is a flip-flop that is set by the output of this delay counter 21; 23 is the output of this flip-flop 22; AND gate, 25 driven by local clock signal 24
is an address counter driven by the output of the gate 23 of this M, 26 is a transmission buffer memory for transmitting the accumulated data of the address specified by this address counter 25, and 27 is a buffer memory from the address counter 25 to the flip-flop. 28 is a preamble word generator that is driven at the timing of the delay counter 21, and 29 is a transmitter that transmits the output of this preamble word generator. An OR gate 30 added to the output of the buffer memory 26 is an example of an output bit output from this OR gate 29.

In the slave station device configured as described above, flip-flop 3 is reset by the output of delay counter 7, and flip-flop 10 is reset by the output of address counter 1.
3, the flip-flop 18 is reset by the output of the delay counter 21, and the flip-flop 22 is reset by the output of the address counter 25.

Although not shown in the figure, the delay counter 7, delay counter 21, address counter 13, and address counter 25 clear themselves at the same time as they are output.

The connection shown by the broken line to the OR gate 4 in FIG. 3 is for the case where the mask station transmits the information part following the reference unique word as shown in FIG. If the station transmits only the reference unique word as shown, the connection shown by the broken line is unnecessary.

In FIG. 3, demodulated input bit example 1 is input to a data unique word detector 2, and when a data unique word is detected, a flip-flop 3 is set and a clock input 6 is input to a delay counter 1.

When the station discriminator 8 determines that the input bit string 1 is addressed to the station, the station discriminator 8 outputs a logic "1" signal to the gate 9, but in synchronization with this point, the delay counter 7 also outputs a logic "1" signal. A logic "1" signal is output to gate 9, and flip-flop 10 is set by the output of gate 9.

When the flip-flop 10 is set, the address counter 13 starts counting addresses, and the input bit string 1 is input to the reception buffer memory 14 via the data unique word detector 2 and the station identifier 8. 13 controls which address in the reception buffer memory 14 this manual bit string 1 is stored.

The time when the final stage of the address counter 13 outputs an output and the address counter 13 self-clears corresponds to the reception completion time, and this output resets the flip-flop 10 and at the same time sends the reception interrupt signal 1 to the central processing unit 15.
Give 6.

In response to this interrupt signal 16, the central processing unit 15 transfers and processes the signal stored in the reception buffer memory 14.

Input bit string 1 is reference unique word detector 1
7, when a reference unique word is detected, the flip-flop 22 is set after a delay time determined by the clock 20 and the delay counter 21 from that point, and the address counter 25 starts counting addresses. do.

Before the start of this counting, the output of the preamble word generator 28 is outputted as the first bit string of the output bit string 30 via the OR gate 29 by the output of the predetermined count value of the delay counter 21, and then the output of the preamble word generator 28 is outputted as the first bit string of the output bit string 30. The stored contents of the transmission buffer memory 26 are sequentially outputted in response to the count output.

The time at which the address counter 25 self-clears when an output is output from the final stage of the address counter 25 corresponds to the time when the transmission is completed, and at the same time, the flip-flop 22 is reset by this output, and at the same time, the transmission interrupt signal 2 is sent to the central processing unit 15.
Give 7.

In response to this interrupt signal 27, the central processing unit 15 transfers the transmission data to be transmitted next time to the transmission buffer memory 26.

In the above explanation, it is assumed that the station identification code is placed at the beginning of the information part, and an example has been described in which the reception buffer memory 14 receives information after the station identification code 8 determines that the information is addressed to the own station. By slightly changing the circuit configuration, it is easy to receive data from the beginning of the information part.

There are various ways of transferring data between the central processing unit 15 and the reception buffer memory 14 and transmission buffer memory 26, such as flag-controlled transfer in addition to interrupt transfer, but these are techniques in different fields. Since this is not directly related to this invention, its description is omitted, and FIG. 3 shows the case of an interrupt.

In the data unique word detector 2 and the reference unique word detector 17 shown in FIG. 3, unique words are detected from the received bit string by autocorrelation detection.

Since an error in detecting a unique word has a serious effect on synchronization, it is common practice to set a code error threshold value to be allowed in advance for a received unique word, and to accept only errors less than this value as a unique word.

The number of circuits required for this purpose is determined by the bit length of the unique word, the modulation method, etc., but is usually quite large.

For example, a unique word detector in a 4-phase PSK communication system with a 32-bit unique word and a 4-bit bit error threshold will require at least four 8-bit shift registers and a 4-bit full adder, even if well devised. 20 pieces, 8 4-bit comparators, and approximately 50 pieces including the gate circuit.
More than one IC is required.

As is clear from the above, the conventional slave station unique word detector requires two unique word detectors, a data unique word detector and a reference unique word detector, so it depends on the bit length of the unique word and the modulation method. The number of circuits may be considerably large, and since the preamble word generators of the mask station and slave stations are different, it has the disadvantage that it is difficult to unify the circuit boards of the mask station and slave stations. .

This invention was made to eliminate the above-mentioned drawbacks, and the mask station is equipped with means for successively sending a plurality of slave station data unique words as reference unique words, and each slave station has a unique word detector. The object of the present invention is to establish character synchronization and frame synchronization using the same unique word detector by providing means for recognizing a plurality of data unique words as a reference unique word when a plurality of data unique words are successively detected.

FIG. 4 is a block diagram of a slave station device in a time division multiple access communication system showing an embodiment of the present invention.
5 to 16 and 18 to 30 are exactly the same as the conventional device shown in FIG.

41 is an AND gate for clearing the address counter 13 by ANDing the output of the delay counter 7 and the data unique word detector 2; 42 is an AND gate for clearing the address counter 13 by the output of the delay counter 7;
An OR gate 43 is an OR gate for resetting the flip-flop 10 using the output of the address counter 13.

Comparing the slave station device of the time division multiple access communication system configured as described above with the conventional device shown in FIG.
The major difference is the addition of D gate 41.

5 and 6 are operation time charts showing typical time relationships between the outputs of various gates and flip-flops of the slave station device in FIG. 4, and FIG. FIG. 6 shows a case where the input bit string is from a mask station and is addressed to the own station.

Figures 5 and 6 were created based on the following assumptions.

That is, it is assumed that the data unique word consists of 16 bits, the reference unique word consists of two data unique words, or 32 bits, and the information part consists of 256 bits, and the station identification code is 8 bits and is placed at the beginning of the information part.

That is, in FIG. 5, the human input signal 1 is a unique word for character synchronization of 16 bits (in this specification, the first unique word is The station identification code is divided into 256-bit information portions consisting of bits DO-D255 (middle bits are omitted), and the station identification code consists of 8 bits DO-D7.

In Fig. 6, the 256-bit information part of Do-D255 and the 8-bit station identification code of DO-D7 therein are the same as in Fig. 5, but the 16-bit information part is exactly the same as UWO-UW15 in Fig. 5. is repeated twice in succession to form a unique word for 32-bit frame synchronization (referred to as a second unique word in this specification).

In the case of FIG. 5, when the unique word detector 2 detects a unique word from the input bit string 1, the flip-flop 3 is set, and the delay counter T waits until the reception of the 256-bit information portion (DO-D 255) is completed. After a time delay of , reset the flip-flop 3.

On the other hand, the delay counter 7 applies a pulse to the AND gate 9 after a time delay is given from the start of its operation to the completion of receiving the 8-bit station identification code, and at that time, the station identifier 8 detects the signal addressed to the own station. When it is determined, the output pulse of the station identifier 8 is applied to the other input terminal of the AND gate 9, and the flip-flop 10 is set.

Address counter 13 is 248, i.e. (256-8)
When the information part of the bit is received, flip-flop 1
Reset to 0:/ At the same time, a reception interrupt signal 16 is given to the central processing unit 15.

In the case of FIG. 6, input signal 1 is detected by unique word detector 2.
When the first unique word is detected, the flip-flop 3 is set and the delay counter 7 is driven in the same way as in FIG.

The delay counter 7 applies a pulse to the M-mount gate 41 after a 16-bit time delay from the start of operation.At this time, the detection pulse from the unique word detector 2 is applied to the AND gate 41.
AND gate 41 outputs a pulse.

This pulse means that a reference unique word has been detected, and as explained in FIG. 3, the next operation is performed at the same time as the reference timing for the transmission operation.

That is, when the mask station transmits the information part following the reference unique word as shown in FIG. 1, it makes the connection shown by the broken line in FIG. 4, clears the delay counter 7 and address counter 13, and performs the station identification judgment operation. Go back to the fifth
The receiving operation explained in the figure is performed.

If the mask station transmits only the reference unique word as shown in FIG. 2, connect the OR gate 42 and the OR gate
3, flip-flop 3 and flip-flop 10 are reset respectively to complete reception and prepare for the next burst reception.

The output indicated by the broken line in FIG. 6 is generated because the first 8 bits of the first unique word match the station code addressed to the local station, but even in this case, the output of the AND gate 41 when the reference unique word is detected is The output clears the delay counter 7 and address counter 13 and returns to the initial state, so that there is no problem with the receiving operation.

In this example, if the 16-bit data pattern of the unique word reception method matches the unique word pattern with less than the code error threshold, there is a possibility that it will be mistakenly detected as a reference unique word.

If the code error critical value is 1 bit, this probability is (16
CO+16C1)/216=2.6X10-4.

However, this detection error is caused by the probability (,6Co+,6C1
)X256/216: considerably smaller than 0.066.

This is because when the burst length is constant, the reset input to the flip-flop 3 can be applied at the completion of data reception, which is a constant time, as in one embodiment of the present invention, so the influence of error detection can be suppressed. .

If the reset input is the same as in the conventional method, the detection error will be the same as in the conventional method.

The probability of error detection decreases exponentially as the number of consecutive transmissions of reference unique words increases.

For example, when a unique word is received three times in a row, the detection error probability is (16CO+16CI)"=6.7X
It becomes 10-8.

Figure 7 shows the reference unique word c! :L, Chi 1
- FIG. 2 is a block diagram of a slave station device showing an embodiment of the present invention in a case where a new word is sent three times or more.

This figure focuses on the differences from the example in Figure 4.
19. 41 to 43 are exactly the same as the apparatus shown in FIG. 4 above.

51 is a flip-flop; 52 is an AND gate driven by this flip-flop 51 and a local clock 53;
54 is a delay counter that delays the output of this AND gate 52 by the time until the reception of the 16-bit unique word is completed; 55 is driven by the output of this delay counter 54 and the output of the data unique word detector 2; ANI
) gate 56 is a counter that counts the output of this AND gate 55 by a preset number.

In the slave station device configured as described above, in order to identify the unique word detected at the beginning of a burst, the output of the data unique word detector 2 and the inverted output of the flip-flop 3 are connected to an AND gate 41. Then, the flip-flop 51 is set.

The reset input of the flip-flop 51 is supplied with an output from the delay counter 7 after a delay time when the reference unique worder reception is completed.

During this time, the output of the flip-flop 51 is the local clock 53.
It is also applied to the AND gate 52 to drive the delay counter 54.

Delay counter 54 is provided with a time delay until it completes receiving the 16-bit unique word.

When the detection pulse from the unique word detector 2 is applied at the time of output of the delay counter 54, the output of the AND gate 55 drives the counting counter 56.

When the value of the counting counter 56 reaches a predetermined number, it means that a reference unique word has been detected.

In the embodiments shown in FIGS. 4 and 7, an example of the configuration of a slave station device is shown, but in the case of a mask station device, the flip-flop 18 is not necessary, and the unique words in the preamble generator 28 are continuous. By adding a circuit that generates multiple times, it is possible to unify the configuration of the station equipment with the slave station equipment.

In addition, in the above embodiment, a frame synchronization method is shown in which the transmission timing of the own station is determined from only the reference unique word. However, in communication systems such as satellite communication where guard time is an equal problem, this card may be used. In order to shorten the time and increase transmission efficiency, the station identification code of the own station is added to the prefix of the slave station burst, and the relative reception position of the reference unique word from the mask station and the own data unique word of the own station is calculated. Although a method is often used in which the transmission position of the local station's burst is determined based on the relationship, it goes without saying that the present invention can be used in this case as well.

Further, even when applied to a baseband transmission system using a dependent synchronization method that does not have a guard time carrier recovery bit and a bit timing recovery bit in the front part, the same effects as in the above embodiment can be obtained.

As explained above, this invention allows frame synchronization and character synchronization to be established with one unique word detector by a simple method of successively sending a plurality of data unique words as reference unique words, thereby making the device inexpensive. Furthermore, the slave station and the master station can be easily unified, and a highly accurate unique word detector can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a format diagram showing one example of the format of a transmission burst in a conventional time division multiple access communication system, Fig. 2 is a format diagram showing another example of the format of a transmission burst, and Fig. 3 is a format diagram in the conventional time division multiple access communication system. A block wiring diagram showing an example of a slave station device of a division multiple access communication system, FIG. 4 is a block wiring diagram of a slave station device showing an embodiment of the present invention, and FIG. 5 shows various gates and flip-flops of the slave station. FIG. 6 is an operation time chart showing another example of the output of various gates and flip-flops of the slave station, and FIG. 7 is a slave station showing another embodiment of the present invention. FIG. 2 is a block diagram of the device. In the figure, 2 is a data unique word detector, T is a delay counter, 8 is a station identifier, 13 is an address counter, 1
4 is a reception buffer memory, 15 is a central processing unit, 21 is a delay counter, 25 is an address counter, 26 is a transmission buffer memory, 28 is a preamble generator, 54 is a delay counter, and 56 is a counting counter. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a unique word detection method for a time division multiple access communication system between one mask station and multiple slave stations communicating via one line, each station detects a first unique word for character synchronization within a time division multiplex transmission burst. the mask station transmits the same signal as the first unique word signal a predetermined number of times in succession as a second unique word signal for frame synchronization; the first unique word signal;
Detecting the second unique word signal using the same unique word detector, and determining whether the signal is for character synchronization or frame synchronization based on the number of times the signal is continuously detected. A unique word detection method.