JPH09116462A - Spread spectrum communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spread spectrum communication equipment which can easily synchronize reception signals by transmitting a pilot channel whose polarity is always '1' and which is spread by a spreading code system except for a spreading code for data transmission from a transmission-side and executing synchronization on a reception-side. SOLUTION: In the transmission-side, a spreading code mapping circuit 2 and a spreading code generation circuit 3 convert transmission data 1 into the spreading code, the code is added with the pilot channel generated in a pilot channel generation circuit 4 by an adder 5, and the code is converted into a transmission signal by a modulator 6 so as to be transmitted by a transmission antenna 7. In the reception-side, the transmission signal is received by a reception antenna 8, is converted into a base band signal by a demodulator 9 and it is inputted to a synchronization circuit 10 and a correlation unit 11. The synchronization circuit 10 synchronizes the spreading code by detecting correlation with the spreading code used for the pilot channel. Thus, the spread spectrum communication equipment which can easily synchronize the reception signal can be obtained.

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 device used for digital radio communication such as a car telephone and a mobile telephone.

[0002]

2. Description of the Related Art A spread spectrum communication system is a system that spreads information in a band sufficiently wider than a minimum required bandwidth when transmitting information, and has a high degree of confidentiality, confidentiality, and interference resistance. It is known to be an excellent communication method. The direct sequence (DS) method is a spread spectrum communication method in which an information signal is directly multiplied by a spreading code in spreading.

In a cellular radio communication system such as a car phone and a mobile phone, FDM is used as a multiple access technique when a plurality of stations simultaneously communicate in the same frequency band.
A (Frequency Division Multiple Access) method, TDMA (Time Division Multiple Access)
Access: Time division multiple access) method is known,
CDMA (Code Division M) using spread spectrum method
The ultimate access (code division multiple access) method is a method that can achieve higher frequency utilization efficiency and can accommodate a larger number of users compared to these technologies.

Paper "Proposal of parallel combination SS communication system"
(Zhu, Sasaki, Marubayashi, IEICE Transactions B-II Vo
In l.J74-B-II No.5), a spread spectrum communication method by a parallel combination method is proposed as a method for further increasing the frequency utilization efficiency. In the parallel combination spread spectrum communication method, K bits of information bits are taken as one data symbol, and r combinations are selected from n kinds of spread code sequences corresponding to the 2 ^K state of this data symbol, and +1
Alternatively, it is a method of performing communication by a signal obtained by multiplying by -1 and adding.

FIG. 8 shows the configuration of a parallel combination spread spectrum communication apparatus in a conventional example. Looking at the transmitter of the spread spectrum communication apparatus shown in this figure, reference numeral 30 denotes data to be transmitted,
Reference numeral 31 is a spreading code mapping circuit that determines a combination that selects a corresponding number (r) of spreading codes from a predetermined type of spreading code sequence, and 32 generates r spreading codes determined by the spreading code mapping circuit. Spreading code generation circuit, 33
Is an adder for adding the r spreading codes, and 34 is a modulator for converting transmission data into a signal for wireless transmission. Further, regarding the receiver of the conventional spread spectrum communication apparatus, reference numeral 36 is a receiving antenna for receiving radio waves, 37 is a demodulator for converting a signal for wireless transmission into processable data, and 38 is all spread spectrum. A correlator for detecting the correlation of the code, 39 is an information bit demapping circuit for obtaining received data from the determination result by the correlator.

In the parallel combination spread spectrum communication apparatus having such a configuration, the transmission data 30 is divided into K bits and input to the spread code mapping circuit 31. In the spreading code mapping circuit 31, r kinds of spreading code sequences are selected from n kinds of spreading code sequences in accordance with the 2 ^K kinds of input K bits.
The combination for selecting the individual and the polarity of the spread code are determined, and the result is input to the spread code generation circuit 32. The spreading code generating circuit 32 generates r spreading codes determined by the spreading code generating pping circuit 31. Spread code generation circuit 3
The r spreading codes generated in 2 are added in the adder 33, converted into a signal for wireless transmission in the modulator 34, and transmitted from the transmitting antenna 35. The transmission signal is received by the reception antenna 36 in the receiver, and is transmitted to the demodulator 3
It is converted into a baseband signal by 7 and input to the correlator 38. The correlator 38 performs correlation detection on all n types of spreading codes, and determines the r spreading codes used for transmission in the transmitter and their polarities. The information bit demapping circuit 39 obtains K-bit received data 40 from the r spreading codes determined by the correlator 38 and their polarities.

[0007]

However, in the above conventional parallel combination spread spectrum communication apparatus,
There is a problem that it is difficult for the receiver to synchronize the spread code with the received signal because the spread code to be transmitted constantly changes.

Further, in the conventional parallel combination spread spectrum communication apparatus, there has been a problem in recent years that no countermeasure is taken against fading which is a cause of deterioration of line quality in land mobile communication.

The present invention has been made in view of the above problems, and an object thereof is to easily perform synchronization by a receiver and to perform high quality data transmission even in a bad environment such as fading. A spread spectrum communication device is provided.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention has a polarity of 1 always on the transmission side of a spread spectrum communication apparatus, and other than n spread codes used for data transmission. The gist is that the configuration is such that the received signal is synchronized by receiving the pilot channel on the receiving side while transmitting the pilot channel spread by the spreading code sequence.

Further, while a convolutional encoder and an interleave circuit are provided on the transmission side of the spread spectrum communication apparatus,
The gist is that an interleave circuit and a Viterbi decoder are used on the receiving side to perform error correction.

[0012]

Therefore, according to the present invention, the polarity is always 1 in the transmitter, and the pilot channel spread by the spreading code sequence other than the n spreading codes used for data transmission can be easily transmitted. In addition, it has an effect that the received signal can be synchronized.

Further, since a convolutional encoder, an interleave circuit is used on the transmitting side and an interleave circuit and a Viterbi decoder are used on the receiving side to perform error correction, high-quality data can be obtained even in a bad environment such as fading. This has the effect of enabling transmission.

[0014]

【Example】

(Embodiment 1) FIG. 1 shows the configuration of a parallel combination spread spectrum communication apparatus in Embodiment 1 of the present invention. Looking at the transmitter of the spread spectrum communication apparatus shown in this figure, code 1 is data to be transmitted, and 2 is a combination that selects a corresponding number (r) of spread codes from a predetermined kind of spread code sequence. A spreading code mapping circuit for generating r spreading codes determined by the spreading code mapping circuit, 4 for a pilot channel generating circuit for generating pilot channels, and 5 for the r spreading codes. An adder for adding the code and the pilot channel, 6 is a modulator for converting the transmission data into a signal for wireless transmission, and 7 is a transmitting antenna for transmitting the modulated signal by radio waves. As for the receiver of the spread spectrum communication apparatus of this embodiment, reference numeral 8 is a receiving antenna for receiving radio waves, 9 is a demodulator for converting a signal for wireless transmission into processable data, and 10 is a spreader. A synchronizing circuit for synchronizing codes, a correlator 11 for detecting correlations for all spread codes, and an information bit demapping circuit 12 for obtaining received data 13 from the determination result by the correlator 11.

In the parallel combination spread spectrum communication apparatus having such a configuration, the transmission data 1 is divided into K bits and input to the spread code mapping circuit 2.
The spread code mapping circuit 2 determines the combination of selecting r from the n kinds of spread code sequences and the polarity of the spread code according to the 2 ^K kinds of the input K bits, and inputs the result to the spread code generation circuit 3. To do. The spread code generation circuit 3 generates r spread codes determined by the spread code mapping circuit 2. On the other hand, the pilot channel generation circuit 4 always has a polarity of 1 and generates a pilot channel spread with a spreading code other than the n spreading codes used for data transmission. R generated in the spread code generation circuit 3
The spreading code and the pilot channel are added in the adder 5, converted into a signal for wireless transmission in the modulator 6, and transmitted from the transmission antenna 7.

The transmitted signal is received by the receiving antenna 8 at the receiver.
Is received, is converted into a baseband signal by the demodulator 9, and is input to the synchronizing circuit 10 and the correlator 11. The synchronization circuit 10 synchronizes the spread code by performing correlation detection with the spread code used for the pilot channel that is constantly transmitted by the transmitter. The correlator 11 uses the timing of the spread code of the received signal reproduced by the synchronization circuit to perform correlation detection for all n types of spread codes, and the r spread codes used for transmission in the transmitter and their polarities. Information bit demapping circuit 1
Output to 2. In the information bit demapping circuit 12,
K-bit received data 13 is obtained from the r spread codes determined by the correlator 11 and their polarities.

As described above, according to this embodiment, the polarity is always 1 on the transmitting side, and the pilot channel spread by the spreading code sequence other than the n spreading codes used for data transmission is transmitted. Since the receiving side is configured to synchronize the received signal by receiving the pilot channel, the received signal can be easily synchronized.

(Embodiment 2) FIG. 2 shows the configuration of a parallel combination spread spectrum communication apparatus according to Embodiment 2 of the present invention. Referring to the transmitter of the spread spectrum communication apparatus shown in this figure, reference numeral 14 is data to be transmitted, and 15 is a convolutional encoder for encoding the input data 14 into a code word at a coding rate of 1 / K. , 16 is an interleave circuit that rearranges the code words input from the convolutional encoder 15 in time order and outputs them, and 17 selects a corresponding number (r) of spreading codes from a predetermined type of spreading code sequence. Spreading code mapping circuit for determining combination, 1
8 is a spreading code generating circuit that generates r spreading codes determined by the spreading code mapping circuit, 19 is a pilot channel generating circuit that generates a pilot channel, and 20 is an addition that adds the r spreading codes and pilot channels. Reference numeral 21 is a modulator for converting transmission data into a signal for wireless transmission, and 22 is a transmission antenna for transmitting the modulated signal by radio waves. As for the receiver of the spread spectrum communication apparatus of this embodiment, reference numeral 23 is a receiving antenna for receiving radio waves, 24 is a demodulator for converting a signal for wireless transmission into processable data, and 25 is a spreader. A synchronizing circuit for synchronizing the codes, a correlator 26 for detecting correlations for all spread codes, and a deinterleave circuit 27 for returning the temporal order exchanged by the interleaving circuit 16 of the transmitter to the original temporal order. , 28 performs Viterbi decoding on the output of the correlator 26 and receives the received data 29.
Is a Viterbi decoder that obtains

In the parallel combinatory spread spectrum communication apparatus having such a configuration, one bit of the transmission data 14 is encoded into a K-bit codeword by the convolutional encoder 15 having an encoding rate of 1 / K, and then the interleave circuit 16 is provided. Is entered. The interleave circuit 16 converts the K-bit codeword
(L × M) pieces are input, the temporal order is rearranged as shown in FIG. 3, and output to the spread code mapping circuit 17. That is, as shown in FIG. 3A, the interleave circuit 16 is
(L × M) code words are sequentially input from the first line on the memory to the second line, the third line, and so on, while (L × M) code words are input. When all the codewords of the memory have been input, as shown in FIG. 3B, (L × M) codewords are sequentially output from the left first column to the second column and the third column of the memory. The output is ... And
The spread code mapping circuit 17 determines the combination of selecting r from the n kinds of spread code sequences and the polarity of the spread code according to the 2 ^K kinds of the input codeword, and inputs the result to the spread code generation circuit 18. To do. Spread code generation circuit 18
Then r determined by the spread code mapping circuit 17
Generate spreading codes. On the other hand, the pilot channel generation circuit 19 always has a polarity of 1 and generates a pilot channel spread with a spreading code other than the n spreading codes used for data transmission. The r spreading codes and pilot channels generated in the spreading code generation circuit are added in the adder 20, converted into a signal for wireless transmission in the modulator 21, and transmitted from the transmission antenna 22.

The transmitted signal is received by the receiving antenna 2 at the receiver.
3 is received by the demodulator 3, converted into a baseband signal by the demodulator 24, and input to the synchronizing circuit 25 and the correlator 26. The synchronizing circuit 25 synchronizes the spread codes by performing correlation detection with the spread code used for the pilot channel that is constantly transmitted by the transmitter. The correlator 26 uses the timing of the spreading code of the received signal reproduced by the synchronizing circuit 25 to perform correlation detection for all n types of spreading codes, and outputs n correlation values to the deinterleave circuit 27. The deinterleave circuit 27 restores the time-ordered correlator outputs exchanged by the interleave circuit 16 of the transmitter to the original time order as shown in FIG. 4, and outputs them to the Viterbi decoder 28. That is, as shown in FIG. 4A, the deinterleave circuit 27 outputs (L × M) correlator outputs from the left first column to the second column of the memory sequentially.
While inputting in the third column, ………, while ((
When all L × M) correlator outputs have been input, FIG.
As shown in (b), this time, while returning the (L × M) correlator outputs, from the first row of the memory to the second row, the third row, ... Viterbi decoder 28
Output to. Then, the Viterbi decoder 28 performs the Viterbi decoding using the combination of the input n correlation values as the soft-decision branch metric to obtain the reception data 29.

As described above, according to the present embodiment, the convolutional encoder and the interleave circuit are provided on the transmitting side of the spread spectrum communication apparatus, while the interleave circuit and the Viterbi decoder are used on the receiving side to perform error correction. As a result, high quality data can be transmitted even in a bad environment such as fading.

(Embodiment 3) FIG. 5 is a block diagram showing the configuration of a parallel combination spread spectrum communication apparatus according to a third embodiment of the present invention. In this embodiment, the second
In the spread spectrum communication apparatus of the embodiment, the arithmetic circuit 45 is provided between the correlator 26 and the deinterleave circuit 27.
Is connected. This arithmetic circuit 45
Is a branch metric for soft-decision Viterbi decoding of each bit of K bits mapped to r spread codes by calculation from n correlation value data obtained by the correlation detection operation in the correlator 53. is there.

The operation of the spread spectrum communication apparatus having such a configuration will be described. First, send data 14
Are encoded by the convolutional encoder 15 and input to the interleave circuit 16. The interleave circuit 16 is similar to that described in the second embodiment above with reference to FIG.
While (L × M) -bit encoded data (code word) is input as shown in FIG. 3, the spreading code mapping circuit 1 is arranged by rearranging the temporal order bit by bit as shown in FIG.
Output to 7. The spread code mapping circuit 17 determines the combination of selecting r from the n kinds of spread code sequences and the polarity of the spread code according to the 2 ^K kinds of the input K-bit codeword, and the result is spread code generation circuit 18 To enter. The spread code generation circuit 18 generates r spread codes determined by the spread code mapping circuit 17. On the other hand, the polarity of the pilot channel generation circuit 19 is always 1
Then, a pilot channel spread with a spreading code other than the n spreading codes used for data transmission is generated.
The r spreading codes and pilot channels generated in the spreading code generating circuit 18 are added in the adder 20, converted into a signal for wireless transmission in the modulator 21, and transmitted from the transmitting antenna 22.

The transmitted signal is received by the receiving antenna 2 at the receiver.
3 is received by the demodulator 3, converted into a baseband signal by the demodulator 24, and input to the synchronizing circuit 25 and the correlator 26. The synchronization circuit 25 synchronizes the spread codes by performing correlation detection with the spread code used for the pilot channel that is constantly transmitted by the transmitter. The correlator 26 uses the timing of the spread code of the received signal reproduced by the synchronization circuit 25 to perform correlation detection for all n types of spread codes, and outputs n correlation value data to the arithmetic circuit 45. In the arithmetic circuit 45, r is calculated from the n correlation value data.
The branch metric for soft-decision Viterbi decoding of each bit of K bits mapped to the respective spreading codes is output to the deinterleave circuit 27.

In the deinterleave circuit 27, the data interleaved in 1-bit units by the interleave circuit 16 of the transmitter is put in the original time order as shown in FIG. 4 as in the second embodiment. It is returned and output to the Viterbi decoder 28. That is, as shown in FIG. 4A, the deinterleave circuit 27 outputs (L × M) correlator outputs,
From the first column on the left of the memory to the second column, the third column,
………, while all the (L × M) correlator outputs have been input, this time, as shown in FIG. 4B, this time, (L × M) correlator is input. The output is sequentially output from the first line of the memory to the second line, the third line, ...
The data is output to the Viterbi decoder 28 while returning to the above. Then, in the Viterbi decoder 28, soft decision Viterbi decoding is performed using the branch metric added to the input bit unit, and the received data 29 is obtained.

FIGS. 6 and 7 are views for explaining a concrete example of the operation of the arithmetic circuit 45 shown in FIG. An example of mapping K = 4 bits as shown in FIG. 6 and selecting and transmitting r = 1 from n = 8 types of spreading code sequences will be described. FIG.
It is assumed that eight pieces of correlation value data C1 to C8 are input as described above. Probability that each bit of 4 bits mapped to one spreading code is 1 is obtained from eight pieces of correlation value data C1 to C8. The mapping corresponding to the spreading code of C3 having the maximum absolute value among the eight pieces of correlation value data C1 to C8 is (0, 0, 1, 0) from FIG. Correlation value data of C3 is taken as the probability of each bit of 4 bits, and C1 to C are added to include information of other correlation values.
The variation degree k of 8 is multiplied. k takes the difference between the absolute value of C3 and the average of the absolute values of all correlation values. In the case of this example, the correlation value data of C3 is +100 and k = 72.75, so the branch metrics for Viterbi decoding of each bit are (-7275, -7275, +7275, -727).
5).

As described above, according to this embodiment, the convolutional encoder 15 and the interleave circuit 16 are provided on the transmission side, and the branch metric for soft decision Viterbi decoding in bit units is output from the correlation value data to the reception side. Arithmetic circuit 45,
By providing the deinterleave circuit 27 and the Viterbi decoder 28, it is possible to interleave on a bit-by-bit basis in the parallel combinatorial spreading communication apparatus, and the effect of error correction of Viterbi decoding on concentrated errors is enhanced.

[0028]

As is apparent from the above embodiment, according to the present invention, the polarity is always 1 in the transmitter, and the spreading code sequence other than the n spreading codes used for data transmission is spread. By transmitting the pilot channel, it is possible to easily synchronize the received signal.

Further, the convolutional encoder and the interleave circuit are used on the transmission side, and the interleave circuit and the Viterbi decoder are used on the reception side to perform error correction.
It has an effect that high quality data can be transmitted even in a bad environment such as fading.

Further, a convolutional encoder, an interleave circuit, an arithmetic circuit for outputting a branch metric for bit-wise soft-decision Viterbi decoding from the correlation value data, a deinterleave circuit, and a Viterbi decoder are provided on the transmitting side, so that parallel combination can be achieved. In the spreading communication device, it is possible to interleave in 1-bit units, and the effect of error correction of Viterbi decoding on concentrated errors is enhanced. Therefore, there is an effect that high quality data can be transmitted even in a bad environment such as fading.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a parallel combination spread spectrum communication apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a parallel combination spread spectrum communication apparatus according to a second embodiment of the present invention.

FIG. 3 is a diagram for explaining the concept of an operation of rearranging the temporal order of input data by an interleave circuit and outputting the input data in the second embodiment.

FIG. 4 is a diagram illustrating a concept of an operation in which the deinterleave circuit in the second embodiment restores and outputs the data whose temporal order has been rearranged by the interleave circuit.

FIG. 5 is a block diagram showing a configuration of a parallel combination spread spectrum communication apparatus according to a third embodiment of the present invention.

FIG. 6 shows an example in the case where, in the third embodiment, r = 1 is selected and transmitted from the spreading code series of the drawings showing an example of mapping of data input to the arithmetic circuit. FIG.
It is assumed that eight pieces of correlation value data C1 to C8 are input as described above. Conceptual diagram of the operation of the interleave circuit and the deinterleave circuit in the third embodiment

FIG. 7 is a diagram showing an operation example in which the data mapped as shown in FIG. 6 is input in the arithmetic circuit of the third embodiment.

FIG. 8 is a block diagram showing a configuration of a conventional spread spectrum communication device.

[Explanation of symbols]

 1, 14 Transmission data 2, 17 Spread code mapping circuit 3, 18 Spread code generation circuit 4, 19 Pilot channel generation circuit 5, 20 Adder 6, 21 Modulator 7, 22 Transmission antenna 8, 23 Reception antenna 9, 24 Demodulator 10, 25 Synchronous circuit 11, 26 Information bit demapping circuit 12, 29 Received data 15 Convolutional encoder 16 Interleave circuit 27 Deinterleave circuit 28 Viterbi decoder 45 Operation circuit

Claims (7)

[Claims] 1. Information bits K bits are taken as one data symbol, and r combinations are selected from n kinds of spreading code sequences corresponding to the 2 ^K states of the data symbols, and +1.
Alternatively, a transmitter and a receiver using a parallel combinatory spread spectrum method for performing communication by a signal obtained by multiplying by -1 and n kinds of spreading code sequences used in the transmission of the data symbol whose polarity is always +1 in the transmitter A spread spectrum communication apparatus having a function of transmitting a pilot channel spread by a spreading code other than the above, and a synchronization circuit for receiving the pilot channel in the receiver and reproducing the transmission timing. 2. Convolutional coding is performed on information bits,
2 ^{K of} these K bits for the encoded K bits
, A transmitter using a parallel combinatory spread spectrum method for transmitting signals obtained by selecting r combinations from n kinds of spreading code sequences and multiplying them by +1 or -1 and all n kinds of spreading codes. And a receiver for performing Viterbi decoding using a combination of n correlation values as branch metrics for soft decision. 3. A function of transmitting a pilot channel, which has a polarity of always +1 in a transmitter and is spread by a spreading code other than n kinds of spreading code sequences used for transmission of the data symbols, and a receiver receives the pilot channel. 3. The spread spectrum communication device according to claim 2, further comprising a synchronization circuit that regenerates the transmission timing. 4. An interleave circuit for changing the time order of a convolutionally coded sequence in the transmitter in K bits as a unit, and a deinterleave circuit for returning the time order of the sequence reordered by the interleave in the receiver. The spread spectrum communication device according to claim 2, further comprising: 5. An interleave circuit for changing the time order of a convolutionally coded sequence in a transmitter in K bits as a unit, and a deinterleave circuit for returning the time order of the sequence reordered by the interleave in a receiver. The spread spectrum communication device according to claim 3, further comprising: 6. Convolutional coding is performed on the information bits, and for the coded sequence K bits, r combinations are selected from n kinds of spreading code sequences corresponding to the 2 ^K states of the K bits. A transmitter using a parallel combinatory spread spectrum method for transmitting a signal obtained by adding +1 or -1 times to the selection, and performing correlation detection for all n types of spread codes, and transmitting r signals transmitted from n correlation values. Spread spectrum communication apparatus provided with a receiver for performing Viterbi decoding by adding a branch metric for soft decision to each bit of K bits corresponding to a spread code 7. An interleave circuit for changing the time order of a convolutionally coded sequence in the transmitter in units of 1 bit, and a deinterleave circuit for returning the time order of the sequence reordered by the interleave in the receiver. The spread spectrum communication device according to claim 6, further comprising: