JPH07143023A - Spread spectrum polyphase modulation/demodulation method - Google Patents

Abstract

PURPOSE:To solve a problem of making information hard to discriminate due to an exponential increase of code points to decrease distance between each other of code points by increasing the number of information bits in polyphase modulation. CONSTITUTION:Serial transmission data SD (...101...) is converted to parallel data by a serial-parallel converter 1, and three ((n) in general) parallel bits 1, 0 and 1 are inputted to information spreader 2, 3 and 4, respectively, and the information (spectrum) is spread by using spread codes A, B and C. Spread data (a), (b) and (c) are added by an adder 5 at each bit, ad each bit is changed to multi-valued data (s) with four values. The information diffusers 2, 3 and 4 output the spread codes as they are when input data is 1, while outputs then by inverting 0, 1 of each bit when it is 0. The multi-valued data (s) is inputted to a modulator 6, each bit converted into parallel data, and the phase shift quantity of a carrier are set at 0, pi/2, pi, -theta/2 corresponding to the values 0, 1, 2 and 3 of each bit of the data (s). On the demodulation side, multi-valued data s' is obtained through plane detection, the correlation of the data s' with each spread code is detected, and transmission data 1, 0 and 1 are restored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication method, and more particularly to a method for improving an information transmission speed without widening a required frequency band, and a method for improving the speed is particularly high.

[0002]

2. Description of the Related Art A conventional spread spectrum communication method using polyphase modulation uses 2 ⁿ code points for ⁿ information bits as shown in FIG. For example, in (A), in order to transmit 1-bit binary data of “0” and “1”, π
(Rad) When two code points separated are used, BPS
K (BinaryPhase Shift Keyin
called g). When transmitting 2-bit information,
As shown in (B), (0,0), (0,1), (1,
0), (1, 1) for the possible information values, π / 2
QPSK (Quadrattu) that associates distant code points
re Phase Shift Keying) is used. In case of 3 bits, 8 as shown in (C)
This is a method of dividing the phase and assigning information such as 8PSK in which one code point is associated.

[0003]

As described above, in the conventional spread spectrum polyphase phase modulation / demodulation method, the code points must be exponentially increased in order to increase the information bits, and the distance between the code points must be increased. Has a drawback that it becomes difficult to distinguish information due to shrinkage. The object of the present invention is to improve the above-mentioned conventional drawbacks.

[0004]

According to the present invention, n bits of transmission data are multiplied by n PN sequences (spreading codes) such that the values of correlation peaks do not interfere with each other, and n values are obtained. Of the spread data a, b, c ... Is multi-valued by adding it to each bit, and the carrier wave is modulated so as to perform phase shift according to the value of each bit of the multi-valued data. , More information can be transmitted with fewer code points.

On the receiving side, the above-mentioned modulated wave is phase-detected to obtain multi-valued data, the correlation between the multi-valued data and the preceding n spreading codes is detected, and n bits of the transmission data are restored. . In the present invention configured as described above, even if the information increases by 1 bit, the code point only needs to be increased by 1, so that the increase in the code point with respect to the increase in the amount of information can be minimized.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a block diagram of a transmitter / receiver using a spread spectrum polyphase phase modulation / demodulation method according to the present invention.
In this example, three spreading codes are used and four-phase phase modulation is performed. Spreading codes are shown in FIG.
For simplicity, one code length of 12 is used, and three time-slide codes are used.

Now, input data strings are "1", "0",
If it is "1", this data is parallelized by the serial-parallel converter 1 and input to the information spreaders 2, 3 and 4, and the code A,
Spreading code A supplied from B, C generators 7, 8, 9
Information is spread by being multiplied by B and C, respectively. The spread data a, b, c are added bit by bit by the adder 5 to become 4-valued data s. FIG. 1C shows data before and after the adder 5. The information spreaders 2 to 4 output the spread code as it is when the data is "1", and inverts 1 and 0 of each bit of the spread code and outputs it when the data is "0".
The quaternary adder output data s is the modulator 6 as 2-bit (generally a plurality of bits) parallel data such as a binary code.
Entered in. In the modulator 6, as shown in FIG. 2 (A), if the multi-valued data s is “0” with respect to the carrier wave, phase shift is not performed, and if it is “1”, only π / 2 is applied in the CCW direction to “2”.
If so, assign π only in CCW direction, and if it is “3”, assign only π / 2 in CW direction, and so on. This is Figure 3
It looks like a phase arrangement similar to the conventional phase modulation "QPSK" of (B).

Similarly, when the number of code multiplexes is increased to 4, the 5-phase phase modulation as shown in FIG. In this way, if the number of multiplexing is increased by 1, the number of code points will be increased by 1. Next, in the demodulation operation, the modulated wave modulated by the modulator 6 by the s output of FIG. 1 passes through the transmission medium, and then is demodulated by the demodulator 10 from the phase displacement of FIG. Is demodulated to original information s'of "3". (Fig. 1
(Equivalent to s output of (C)). This information s'is represented by 2-bit parallel data, is input to the code A correlator 11, the code B correlator 12, and the code C correlator 13, and is respectively correlated.

In the code A correlator 11, the demodulated information s'is correlated with the code A. When the code is “0”, the information is subtracted, and when the code is “1”, the information is added. Information s ′ 220222220022 Code A 000111010011 Code A Correlator output −2-2-0 + 2 + 2 + 2-2 + 2-0-0 + 2 + 2 = + 6 Similarly Code B, Code C Correlators 12, 13 Then, information s' 220222222022 code B 001100011101 code B correlator output -2-2 + 0 + 2-2-2-2 + 2 + 0 + 0-2 + 2 = -6 information s'2202222220022 code C 110100110001 code C Correlator output + 2 + 2-0 + 2-2-2 + 2 + 2-0-0-2 + 2 = + 6 In the information discrimination and parallel / serial converter 14, this correlation value (+
6, -6, + 6) is positive, the data is determined to be "1",
If it is negative, it is determined to be "0". In this example, "1",
It can be read as "0" or "1". Make such a determination,
The parallel data is replaced with the serial data and is output as data.

The spreading codes A, B and C are selected such that they do not interfere with each other in the above-mentioned correlation operation. For example, since the correlation between the codes A and B is zero as follows, it does not affect the discrimination of the codes. Correlations between the codes A and C and the codes B and C are also zero.

[0011]

As described above, according to the present invention, spread data is obtained by multiplying each bit of transmission data by a PN sequence such that correlation peak values do not interfere with each other, and the spread data is obtained for each bit. In addition, the multi-value conversion is performed and the modulation that causes the phase shift according to the multi-value is performed, and the increase of the code points with respect to the increase of the information amount is small, and the efficient information transmission is possible. .

Conventionally, two-phase (1 bit), four-phase (2
bit), 8 phase (3 bit), 16 phase (4 bit), ...
Thus, only the power-of-two phase modulation was used, but according to the present invention, three-phase (2 bit), four-phase (3 bi)
t), 5 phase (4 bit), ..., 3 phase, 5 phase, etc., which has not been practically used in the past, are also possible.

[Brief description of drawings]

FIG. 1A is a block diagram showing an embodiment of the present invention,
(B) is a figure which shows an example of the spreading codes A, B, and C used by (A), (C) is a figure which shows an example of the input data of the adder 5 of (A).

FIG. 2 (A) is a 3 implemented in modulator 6 of FIG. 1 (A).
The figure showing the state transition of code multiplex 4-phase modulation, (B) is 4
The figure which shows the state transition of code multiplex 5-phase phase modulation.

3 (A), (B) and (C) are conventional 2
The code arrangement diagram in phase four, phase four and phase eight modulation.

Claims (2)

[Claims] 1. Multiplying certain information by a pseudo-random code sequence (referred to as a PN sequence) that has a large autocorrelation at the time of synchronization and a certain low correlation when the timing is shifted by one code (chip) or more. , A spread spectrum communication method for transmitting information by spreading a spectrum, wherein n (integer of 2 or more) bits d _{1 of} binary transmission data,
For d ₂ , d _3, ... N spreading codes A, B, which are PN sequences whose correlation peak values do not interfere with each other.
C ... Multiplies each by n to convert it into n spread spectrum data a, b, c ... And adds these n spread spectrum data for each bit so that each bit is 0, 1, 2 ,. It is characterized in that it is converted into multivalued data (s) having any value, and a carrier wave is subjected to a phase shift of a magnitude according to the value of each bit of the multivalued data (s). Spread spectrum polyphase modulation method. 2. The multi-valued data (s) is obtained by phase-detecting the modulated wave obtained by the phase modulation method according to claim 1, and the multi-valued data (s) and the spread codes A, B and C are obtained. , ... to recover the n bits d ₁ , d ₂ , d ₃ , ... of the transmission data by detecting the correlation with each of them, and a spread spectrum multiphase phase demodulation method.