JPH05160807A - Spread code generating method - Google Patents

Abstract

PURPOSE:To establish the synchronism of all spread codes by establishing the synchronism of a reference spread code in the spread spectrum communication sending simultaneously plural spread codes with a different period. CONSTITUTION:A longest PN code PN1 is outputted from a 1st PN code generator 302, the PN code PNm of an intermediate length is outputted from a 2nd PN code generator 303 and a shortest PN code PNn is outputted from a 3rd PN code generator 304. The 2nd and 3rd PN code generators 303, 304 are initialized by a synchronous signal P from the 1st PN code generator 302.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread code generation method for a spread spectrum communication apparatus using a plurality of spread codes having different code lengths, and more particularly to improvement of a synchronization method for each spread code.

[0002]

2. Description of the Related Art Conventionally, different spreading codes having the same code length are used, or if the spreading codes have different code lengths, the code length is 2
^Since it is an odd prime number of ⁿ −1 (n is a positive integer and the number of stages of the shift register of the code generator), the phase of each code will deviate with time. Therefore, as shown in FIGS. 5 and 6, synchronization has been established for each spreading code.

FIG. 5 shows a transmitter and FIG. 6 shows a receiver. Figure 5
, 101 to 10n are spread modulators, and 111 to 11
n is a spread code generator (PNG), 121 to 12n are carrier wave oscillators, 131 to 13n are modulators, and 141 is a combiner. 6, 201 to 20n are bandpass filters, 211 to 21n are correlators, 221 to 22n are despreading code generators, 231 to 23n are clock generators, and 24.
Reference numerals 1 to 24n are synchronization circuits, and 250 is a data demodulation circuit. Baseband data 1101 to 11 in the transmitter
0n and spreading codes PN101 to PN10n having different code lengths generated by the spreading code generators 111 to 11n are spread-modulated by the spreading modulators 101 to 10n.

Output SS10 of spread modulators 101-10n
1 to SS10n are carrier waves R from oscillators 121 to 12n
PSK modulation is performed by F101 to RF10n and modulators 131 to 13n, respectively, and RFSS101 to RFSS10n
To get RFSS101 to RFSS10n are synthesizers 14
1 spread spectrum signal TXSS101
Sent as.

In the receiving section, the TXSS 101 is the RXS
It is received as S201. RXSS201 received
Are distributed and input to band pass filters 201 to 20n having RF101 to RF10n as center frequencies, respectively. Output R of each bandpass filter 201 to 20n
FSS 201 to RFSS 20n are correlators 211 to 21n
One of the inputs is input.

On the other hand, the despreading codes SS201 to SS20n generated by the despreading code generators 221 to 22n.
Are input to the other inputs of the correlators 211 to 21n, respectively. Correlation outputs of the correlators 211 to 21n are input to the respective synchronizing circuits 241 to 24n, and code synchronization is established for each code. When the synchronization is established, the correlation output is input to the data demodulation circuit 250 and the data is demodulated.

[0007]

However, according to the above-mentioned conventional method, there is a drawback in that there is a difference in the synchronization performance depending on the code length of each spread code, and the circuit is complicated and the cost is increased. ..

In order to solve the drawbacks of the conventional method, an object of the present invention is to spread all spread codes by establishing synchronization of a spread code which is a reference in spread spectrum communication in which a plurality of spread codes having different periods are simultaneously transmitted. It is an object of the present invention to provide a code generation method in which the phase of each spreading code is synchronized so that code synchronization is established.

[0009]

In order to achieve the above object, the present invention provides a spread spectrum code generation method for a spread spectrum communication apparatus using a plurality of spread spectrum codes having different code lengths, which is a first spread spectrum as a reference. A first spreading code generator for generating a code and a second spreading code generator having a code length different from at least the spreading code output by the first spreading code generator are used, and all the spreading code generators are used. Are driven by the same clock so that all other spreading codes are synchronized with the reference first spreading code, and the second spreading code generator is based on the output of the first spreading code generator. The basic idea is to initialize the other spreading code generator at the cycle of the reference spreading code.

[0010]

In the method of the present invention, all spreading codes are generated so that other spreading codes are synchronized with the reference spreading code, and it is not necessary to synchronize with each spreading code.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. Figure 1
2 is a conceptual diagram showing one embodiment of the method of the present invention when the reference spread code is the longest, and FIG. 2 shows another example of the method of the present invention when the reference spread code is the shortest. It is a conceptual diagram showing an example. Generally, a spread code used for spread spectrum communication has a length of L, such as an m-sequence code.

[0012]

[Equation 1]

It is an odd prime number such that Therefore, if the code lengths of the spread codes PNn and PMm are Ln and Lm, respectively,

[0014]

[Equation 2]

It is represented by The relationship between Ln and Lm at this time is

[0016]

[Equation 3]

It is represented by 3 different code lengths now
It is assumed that _one spreading code PN ₁ , PMm, PMn is used.
The lengths L ₁ , Lm, Ln of the respective codes are

[0018]

[Equation 4]

[0019] In FIG. 1, when the spread code PN ₁ having the longest code length is used as a reference, the relationship between the lengths of the respective codes is

[0020]

[Equation 5]

[0021] Therefore, by initializing the code generators of the spreading codes PNm and PNn at the timing A (the beginning of the spreading code PN ₁ ) in the figure, all the spreading codes can be synchronized in the cycle of 2 ¹ −1. In FIG. 2, with reference to the spread code PNn having the shortest code length,
The relation of the length of each code is from the equations (4) and (5)

[0022]

[Equation 6]

Therefore, for PNn

[0024]

[Equation 7]

All the spreading codes can be synchronized by initializing the code generators of the spreading codes PN ₁ and PNm in the cycle of. At this time, the relation of the length of each code is

[0026]

[Equation 8]

[0027] In the method described above, the length of the spread code serving as the reference has been described with respect to the longest spread code and the shortest spread code, but it is clear that the spread code can be generated similarly even when the spread code of any other length is used as the reference. Is. Further, when the relationship between the lengths of the spreading codes is 1 = pm, m = qn (p, q: 1, 2, 3, ...) (10), the deterioration of the spreading code performance can be minimized.

FIG. 3 is a block diagram of a spreading code generation circuit according to the present invention based on the longest spreading code, and FIG. 4 is a block diagram of a spreading code generation circuit according to the present invention based on the shortest spreading code. is there. The spreading code generation circuit of FIG. 3 includes a clock generator 301, a first PN code generator 302, and a second PN code generator 302.
PN code generator 303 and third PN code generator 304
And all PN code generators operate on PNCLOCK.

In FIG. 3, the first PN code generator 30
2 outputs the longest spreading (PN) code PN ₁ ,
The second PN code generator 303 outputs a PN code PNm having an intermediate length, and the third PN code generator 304 outputs the shortest PN code PNn.

The second PN code generator 303 and the third PN
The code generator 304 is initialized by the synchronization signal p from the first PN code generator 302.

The spreading code generating circuit of FIG. 4 comprises a clock generator 401, a first PN code generator 402, a second PN code generator 403, a third PN code generator 404 and a period counter 405. All PN code generators are PNC
It operates by LOCK.

In FIG. 4, the first PN code generator 40
The longest PN code PN ₁ is output from ₁ and the second P
Intermediate length PN code PNm from N code generator 402
Is output, and the shortest PN code PNn is output from the third PN code generator 403.

The synchronization signal q from the third PN code generator 403 is input to the cycle counter 405, which outputs the initialization signal r for each set cycle, and the first PN code generator 40.
2 and the second PN code generator 403 are initialized.

[0034]

As described above, according to the present invention, (i) even if a plurality of spreading codes having different code lengths are used,
By establishing the synchronization of the reference spreading code, it is possible to establish the synchronization of all the spreading codes used. (Ii) Even if a plurality of spreading codes having different code lengths are used,
Only one synchronization circuit is needed, which simplifies the circuit. (Iii) The cost can be reduced.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of the method of the present invention.

FIG. 2 is a conceptual diagram showing another embodiment of the method of the present invention.

FIG. 3 is a block diagram showing a spread code generating circuit according to the method of FIG.

FIG. 4 is a block diagram showing a spread code generating circuit according to the method of FIG.

FIG. 5 is a block diagram showing a transmitter of a conventional spread spectrum communication device.

FIG. 6 is a block diagram showing a receiving unit of the apparatus.

[Explanation of symbols]

PN _{1 to} PNm to PNn spreading code 301 clock generator 302 to 304 PN code generator

Claims (1)

[Claims] 1. A spread code generation method for a spread spectrum communication apparatus using a plurality of spread codes having different code lengths, wherein a first spread code generator for generating a reference first spread code, and at least the above. A second spreading code generator having a code length different from that of the spreading code output from the first spreading code generator is used, all of the above spreading code generators are driven by the same clock, and the first spreading code serving as a reference is used. All other spreading codes are synchronized with each other, and the second spreading code generator is initialized based on the output of the first spreading code generator, and the other spreading code is used at the cycle of the reference spreading code. A spreading code generating method characterized by initializing a spreading code generator.