JPH04156744A - Transmission system - Google Patents

Abstract

PURPOSE:To receive the data of high quality, and to apply the title system to the polyphase PSK in which N is 3 or more as well by providing a receiving side with a means to reproduce correct receive data by executing code conversion to remove the code uncertainty of a received symbol string in accordance with symbol difference. CONSTITUTION:The frame signals 1a to 1c of M-symbol length in which the symbol is made into the symbol arrangement of two-phase PSK are prepaired at a transmitting side, and they are inserted unto transmit data 2a to 2c, and are 2N-phase PSK- modulated, and at the receiving side, the frame signal inserted by the symbol arrangement of the two-phase PSK is detected from among the demodulated outputs of a PSK demodulator 6. Then, the symbol difference corresponding to phase difference between transmission and reception is estimated from the amplitude information of the demodulated frame signals 6i, 6g at the time of detection, and the receive data is reproduced by executing the code conversion for making the phase uncertainty of the demodulated signal certain in accordance with the estimated symbol difference between the transmission and the reception. Thus, the data of the high quality can be received without using differential code modulation in which an error may be extended, and in addition, this system can be applied to the 2N-polyphase PSK of N>=3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission system, and particularly to a transmission system aimed at removing phase uncertainty in a digital wireless transmission system using 2N-phase PSK modulation.

[Conventional technology]

In data transmission using polyphase PSK indicated by 2N phases, 2N transmission symbols having a phase difference of 2π/2N with respect to a reference phase on the transmitting side are prepared.

Since each can add N bits of information, the transmitted data is converted into N code strings, and the phase of these transmitted data is
It is PSK modulated into N phases and transmitted to the receiving side. On the receiving side, a reference phase is prepared and the received symbols are demodulated based on the phase state of the received signal with respect to the reference phase. however,
Since the modulated signal does not contain information about the reference phase of the transmitter, the reference phase must be transmitted to the receiver by some means, or the receiver must be able to demodulate it without knowing the reference phase of the transmitter. It is necessary to

Conventional polyphase PSK transmission uses differential code modulation, and performs a storage type operation to reproduce received data from information one time slot before, as described below.・Differential code modulation handles 2N transmission symbols by expressing them as N-bit codes, performs a summation operation modulo 2N on the N-bit transmission code of the transmission symbol one time slot before, and calculates the next The data is transmitted as a transmission symbol, and the receiving side reproduces the received data by performing a difference operation modulo 2N between the received symbol and the received symbol one time slot before.

Now, as two examples, the case of 4-phase PSK will be explained. 4
The phase PSK is N=2, and the 4
It holds transmission symbols and performs an operation modulo 22=4 as follows.

For convenience of explanation, Q? .

! lj, (2j, !31), the transmission symbol one time slot before was "3", and I want to continue sending data as "M '1"3"1"2"1"3'12' Then, “3”O” 1'tOf Jlj 1
1 "0"3"1", and the transmission symbol is transmitted.

On the receiving side, the received data is reproduced by calculating the difference modulo 4 with the received symbol one time slot before.

For example, if the receiving side receives the previously transmitted symbol 63 as 2', then "2'"3"0"3"O"2" 1311
21 “0” is continuously received and when the difference is calculated, 'II Ell 13"1'2'11"3"2
' and matches the transmitted symbol, 2ch,
The received data is reproduced as 00101011, lch, and 11011101, but if an error shown by the symbol - occurs in the transmission path.

2'3"0"i"O"2"3' 121 When "0' is received, '1" l l l
l i+“-〇-9“2” Ell g31 1
29 and 2 time slots 2ch, OO-Ω-01011, lch, 110i11
01 expands the error to 2 bits.

Now, when inserting a channel identification code, the transmitting side inserts the radio frame signal and the channel identification code into the transmission data and transmits it, and the receiving side checks whether the demodulated signal is inverted or not by checking the radio frame signal. The received data is reproduced by making a judgment based on the detection and further recognizing the change of channels based on the channel identification code. 4 phase P
The case of SK is shown below.

Assume that 4-phase PSK has N=2, has two channels of modulated signals, and adds 01101 as a radio frame signal and 00 and 01 as channel identification codes.

2ch, 0110101. lch, becomes 0110100, and transmits the transmit symbol as loI&21 “2“O”2”O”“3”.

On the receiving side, it is determined whether the demodulated signals of the two channels are inverted or not based on whether or not the radio frame signals are inverted, and further, channel switching is determined based on the channel identification code.

For example, if the previously transmitted symbol "0" is received as "2" on the receiving side.

2ch, 1001010. lch, 1001011 &2t l□t gQl $21 4QI
121111 is received, the radio frame signal of 2ch is inverted, and the channel identification code indicates lch.

lch indicates that the radio frame signal is inverted and the channel identification code is 2Ch, and the received data can be reproduced from the number by inverting both channels and further switching the channels.

Four frame synchronization circuits are used because they must support one inverted signal and two channels.

In addition, in the case of 8-phase PSK with N=3, the same radio frame signal 01101. The channel identification code is 00. Of and 11 shall be added.

3ch, 0110111, 2ch, 011010L
lch, 0110100 (Ql15""5"
O'"5"3"4' and transmit symbols are transmitted.

Similarly, if the previously transmitted symbol "0" is received as "2" on the receiving side.

3ch, 1001010, 2ch, 0110111, l
ch, 1001011 becomes 121 471&7j
'25 171 451! 81 and symbols are received, the radio frame signal of 3ch is inverted and the channel identification code indicates 2ch, and the radio frame signal of 2ch is not inverted and the channel identification code indicates 3ch.

In lch, the radio frame signal is inverted, the channel identification code indicates lch, and the received data is the first and third c.
By inverting h and exchanging 2ch and 3ch, the received data can be reproduced. In this case, six frame synchronization circuits are used as in the case of 4-phase PSK.

However, if the previous transmitted symbol '0' is received as 3' on the receiving side.

3ch, 1001000, 2ch, 0000011, l
ch, 0000010 (311QI“023
' Receives the symbol "0" Ei "7", the radio frame signal of 3ch is inverted, and the channel identification code indicates 3ch, but 2ch and lch cannot detect the radio frame signal, and the data is different from that on the transmitting side. , the channel identification code becomes meaningless.

[Problem to be solved by the invention]

The conventional transmission method described above has the following drawbacks.

In other words, differential code modulation performs a storage type operation that reproduces received data from information one time slot before, so if an error occurs in the transmission path, the error will expand by one time slot and the required C/H Further, when combined with an error correction code, the error correction effect cannot be fully extracted.

In addition, the method of inserting a channel identification code requires 2XN frame synchronization circuits, which increases the hardware scale, and when N becomes a polyphase PSK of 3 or more, the channel identification code becomes meaningless, and the received data playback becomes difficult.

[Means to solve the problem]

The transmission method of the present invention is a transmission method in a digital wireless transmission system using 2N-phase PSK modulation, and generates a frame signal of M symbol length expressed by an N-bit code and having a 2-phase PSK symbol arrangement to transmit data. and a means for modulating the transmission data with 2NPSK modulation using the transmission symbol string into which the frame signal has been inserted and transmitting it as a modulated output. means for demodulating the received symbol expressed by , means for extracting the frame signal from the demodulated received symbol sequence, and means for estimating a symbol difference between transmission and reception based on amplitude information of the extracted frame signal. , and means for reproducing correct received data by performing code conversion to remove phase uncertainty of the received symbol string in accordance with the symbol difference, on the receiving side.

Further, in the transmission method of the present invention, the symbol difference corresponds to the phase difference between the amplitude information of the demodulated signal phase-detected at the time of frame synchronization and the synchronization carrier, and is estimated based on the amplitude information of the demodulated frame signal at the time of detection, It has a configuration that provides code conversion information necessary for converting demodulated data into correct received data.

〔Example〕

Next, one embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the transmitting side of the transmission system of the present invention, FIG. 2 is a block diagram showing an embodiment of the receiving side of the transmission system of the present invention, and FIG. FIG. 2 is a configuration diagram showing the PSK demodulator 6 in detail.

In this embodiment, the case is assumed to operate in 8-phase PSK with N=3, and the transmitting side has a frame signal generator 1 as shown in FIG.
and PSK as multiplexer 3 and 8-phase PSK modulator
It comprises a modulator 4.

First, the operation on the transmitting side of this embodiment will be explained with reference to FIG.

The frame signal generator 1 outputs a frame signal of M symbol length, which is represented by an N=3 bit code of +1a+ib, lc. These frame signals are multiplexed by the multiplexer 3 into transmission data represented by N=3 bits of 2 av 2 b + 2 c, and modulated data 3 a, 3 b
2N=
Modulated into an 8-phase PSK signal.

Output as modulated output 5. Although the frame signal length and multiplexing method in this case are not limited by the present invention,
For convenience of explanation, the frame signal is in the following data format having a two-phase PSK symbol arrangement.

la, 1110010 1b, 0001101 1c, 1111111 Transmission symbol, 2226626 7 symbols long, and multiplexed as shown in FIG.

FIG. 4(a) is a frame structure in this embodiment, FIG. 4(b) is a diagram showing an example of transmission symbols and code arrangement,
FIG. 4(C) is a diagram showing an example of transmission symbols and corresponding code arrangement.

Next, the configuration of the receiving side shown in FIG. 2 will be explained.

The receiving side includes a PSK demodulator 6 that demodulates the received input subjected to PSK modulation to obtain demodulated data, a frame detector 11 that extracts a frame synchronization signal from the demodulated data, and an arithmetic unit that calculates and outputs the symbol difference between transmission and reception. 12, and a code converter 13 that performs necessary code conversion using symbol differences and outputs desired received data.

Next, the operation on the receiving side will be explained.

The receiving power 5a is phase-detected by a PSK demodulator 6, and demodulated data 8a, 6b+8c and demodulated signal 6 is 6
Output q. Next, the inside of the PSK demodulator 6 will be explained with reference to FIG. Receiver power 5a is 9 oscillator 7
The phases of the synchronized carrier waves 7at7b outputted from the carriers are detected by the phase comparators 8at8b, respectively. The synchronous carrier wave 7b changes the phase of the synchronous carrier wave 7a by 9 by an integrator 9.
The phase is shifted by 0 degrees.

The demodulated signal 6is eq is a signal whose phase is detected by the two-phase comparator 8at sb, and is converted into demodulated data 6a+6b+6c by the code regenerator 10.

Since the synchronous carrier wave has 2N=8 synchronous states with respect to the received signal, it outputs different demodulated signals for each state. Therefore, when transmitting a frame signal on the transmitting side, PSK
The output of the demodulator 6 can take eight states. The demodulated signal example when reception starts with received symbols 2 and 5 is shown in the fifth example.
As shown in the figure. FIG. 5(a) shows a demodulated signal when reception starts from received symbol 2; in this case, the modulated signal and the demodulated signal are the same. FIG. 5(b) shows a demodulated signal when reception starts from received symbol 5; in this case, the modulated signal and the demodulated signal are not the same.

Returning again to FIG. 2, the description of the embodiment will be continued.

Among the demodulated data output by the PSK demodulator 6,
Since the frame pattern inserted in the two-phase PSK symbol arrangement is always included in one of the demodulated data 6a*6b, the frame detector 11 detects the demodulated signal 8.
A frame signal is detected from a s 8 b, and a frame synchronization signal 11a is output. When the computing unit 12 receives the frame synchronization signal 11a.

The demodulated signals 6t and 6Q of the frame signal at that time are taken in and their amplitude information is compared. In this embodiment, since there are eight types of demodulated signals depending on the synchronization state at the time of reception, there are also eight types of amplitude information of the demodulated signal at the time of frame synchronization. In this embodiment, which is 8-phase PSK with N=3, the demodulated signal 6+, Bq
4 different amplitudes are obtained, respectively +6++6Q and I respectively.

When the amplitude is large, it is expressed as an uppercase letter, when the amplitude is small, it is expressed as a lowercase letter, and when the polarity is negative, it is expressed with an inverted sign "-". It is the phase difference between the amplitude information of the demodulated signal and the synchronized carrier wave during frame synchronization, that is, the symbol. The relationship with the difference is as shown in FIG.

That is, in the computing unit 12, the frame synchronization signal 11a
When receiving the demodulated signals 6i and 6Q of the frame signal at that time, the symbol difference is estimated by comparing the demodulated amplitude of the frame signal stored inside the arithmetic unit 12, and symbol difference signals 12a, 12 are generated. b,
12 Output c. The code converter 13 demodulates data 6a based on the sent symbol difference signals 12at 12bt 12c.

6b and 6C are converted into received data 13a, 13b,
Play 13c. FIG. 7 shows a conversion table.

In other words, by preparing and transmitting a frame signal with M=7 symbols so that the symbols are in a two-phase PSK symbol arrangement on the transmitting side, the demodulated signal on the receiving side is 2N=8 depending on the synchronization position of the carrier wave. However, the demodulated signal 6
Since the frame pattern appears in either a + 6 b, it is possible to stably determine the synchronization by providing a frame synchronization circuit with a length of 5M = 7 symbols, and further, by comparing the amplitude information of the demodulated frame signals, it is possible to determine the synchronization between the transmitter and the receiver. It is possible to detect the symbol difference, that is, the phase difference between the demodulated signal and the synchronized carrier wave at the time of frame synchronization, and perform code conversion to determine the five phase uncertainties.

〔Effect of the invention〕

As explained above, in the present invention, two symbols are transmitted on the transmitting side.
Prepare a frame signal with a length of M symbols that has a phase PSK symbol arrangement, and insert this into the transmission data to generate 2N
Phase PSK modulation is performed, and on the receiving side, the frame signal inserted with the two-phase PSK symbol arrangement is detected from the demodulated output of the PSK demodulator, and the position between transmitting and receiving is determined from the amplitude information of the demodulated frame signal at the time of detection. By estimating the symbol difference corresponding to the phase difference and regenerating the received data by performing code conversion to determine the phase uncertainty of the demodulated signal according to the estimated symbol difference between transmitting and receiving, it is possible to prevent error expansion. High-quality reception is possible without using differential code modulation, and N≧3.
It can also be applied to N-polyphase PSK, and its effect is particularly large in noisy transmission paths. When error correction is added, the coding gain of error correction can be achieved by using a differential encoder and an error correction encoder in combination. There is an effect that there is no need to take account of the decrease, and a coding gain close to the ideal state can be expected.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the transmitting side of the transmission system of the present invention, Fig. 2 is a block diagram of an embodiment of the receiving side of the transmission scheme of the present invention, and Fig. 3 is the PSK demodulation of Fig. 2. 4(a) is a block diagram of the device 6, and FIG. 4(b) is a block diagram of the frame in this embodiment.
) is a diagram illustrating transmission symbols and code arrangement examples in this embodiment. FIG. 4(C) is a diagram showing an example of transmission symbols and corresponding code arrangement of this embodiment, FIG. 5(a) is a diagram showing a demodulated signal when reception starts from reception symbol 2, and FIG. )
is a diagram showing the demodulated signal when reception starts from received symbol 5, FIG. 6 is a diagram showing the relationship between the symbol difference and frame signal demodulation amplitude at the time of frame synchronization, and FIG. 7 is a diagram showing the code conversion content based on the symbol difference. FIG. 1...Frame signal generator s lay Ib, l
c...Frame signal, 2a, 2by 2c...Transmission data. 3... Multiplexer, 3a, 3b, 3c... Modulated data. 4...PSK modulator, 5...Modulation output t5a...
Receive input, 6-PSK demodulator t eat 6bt 6c
...Demodulated data* 6tt 6q...Demodulated signal, 7
...Oscillator, 7as7b...Synchronized carrier wave, 8a, 8
b... Phase comparator, 9... Integrator, 10... Code regenerator, 11... Frame detector, 11a... Frame synchronization signal, 12... Arithmetic unit, 12a, 12b, 1
2c... Symbol difference signal, 13... Code converter, 1
3a, 13b, 13C... Received data.

Claims (1)

[Claims] A transmission method in a digital wireless transmission system using 1, 2^N-phase PSK modulation, which generates a frame signal of M symbol length expressed by an N-bit code and having a 2-phase PSK symbol arrangement. and means for 2^NPSK-modulating the transmission data with the inserted transmission symbol sequence and transmitting it as a modulated output. means for receiving the modulated output and demodulating received symbols expressed in N-bit codes; means for extracting the frame signal from the demodulated received symbol sequence; and means for reproducing correct received data by performing code conversion to remove phase uncertainty of the received symbol string in accordance with the symbol difference. Characteristic transmission method. 2. The symbol difference corresponds to the phase difference between the amplitude information of the demodulated signal phase-detected at the time of frame synchronization and the synchronized carrier wave, and is estimated based on the amplitude information of the demodulated frame signal at the time of detection, and is used to distinguish the demodulated data from correct received data. 2. The transmission system according to claim 1, wherein the transmission system provides code conversion information necessary for the transmission.