KR20040014614A - Apparatus and Design Method of Binary CA-MC-CDMA (Constant Amplitude Multi-code CDMA) Communication System without Bandwidth Increment by the Code Selection and Pre-coding Method of Code Rate 1.0 - Google Patents

Abstract

PURPOSE: A device configuration of a binary CA-MC-CDMA(Constant Amplitude-Multi Code-CDMA) communication system without bandwidth increase by using a code selecting method and a new pre-coding system whose code rate is 1 is provided to apply a new pre-coding system and a code selecting method to an existing 4/4 MC-CDMA system, and to output a signal always having constant size, thereby preventing a transmission rate from deteriorating. CONSTITUTION: A received signal(16) passes through a serial/parallel converter(2). A parity signal extractor(13) searches a parity signal(14) used in a transmitter from parallel-converted signals. The parity signal(14) is multiplied by a final bit of the received signal(16). The received signal(16) is parallel/serial-converted(10). The converted signal is multiplied by each Walsh codes. Each parallel branch signal is outputted by signal restoration blocks(8). When the parity signal(14) is multiplied by the final bit and passes through the parallel/serial converter(10), a finally restored signal(17) is obtained.

Description

Apparatus and Design Method of Binary CA-MC-CDMA (Constant Amplitude Multi) Using Code Selection Technique and New Precoding with Code Rate of 1 -code CDMA) Communication System without Bandwidth Increment by the Code Selection and Pre-coding Method of Code Rate 1.0}

In a multi-code code division multiple access (hereinafter referred to as " MC-CDMA ") communication system, a plurality of parallel input data spread by different codes are high when the present invention is combined. Peak-to-Average Power Ratio (hereinafter referred to as "PAPR") occurs. This high PAPR causes nonlinear distortion in the high power amplifier (HPA), causing interference in the band as well as adjacent channels, as well as significantly lowering the power efficiency of the high output amplifier. Therefore, it is very important to reduce the high PAPR to low PAPR, which occurs when multiple, parallel input data are combined.

Examples of Peak to Average Power Ratio (PAPR) reduction techniques invented or reported in MC-CDMA communication systems so far,

1) In September 2002, K. Sathananthan and C. Tellambura published the Vehicular Technology Conference, vol. 1, a method of reducing PAPR generated by multi-user signals in MC-CDMA is called a partial transmit sequence (hereinafter referred to as "PTS") and selective mapping (hereinafter referred to as "SLM"). ) Techniques,

2) In September 2002, O. Vaananen, J. Vankka and K. Halonen published IEEE Seventh International Symposium on Spread Spectrum Techniques and Applications, vol. 2, PAPR reduction technique in MC-CDMA system using clipping method,

3) December 1997 by T. Wada, T. Yamazato, M. Katayama and A. Ogawa. Fundamentals, vol. Multi-code CDMA system with constant amplitude using pre-coding, presented in E80-A,

4) In November 2000, S. I. Kim, G. Y. Jung, S. Y. Yoon and H. S. Lee presented IEICE Trans. Commun. vol. A multicode wideband CDMA system with constant amplitude using the more advanced pre-coding presented in E83-B has been presented.

However, the PTS and SLM techniques have the advantage of reducing PAPR without distortion of the signal, but show limitations in the reduction, and have disadvantages such as transmission of side information using a large amount of computation and additional channels. In addition, the clipping technique distorts the signal itself, which has the effect of reducing the PAPR as much as desired. However, since the clipping signal is not completely recovered by the receiver, the bit error rate of the system is less than " BER ") is very bad.

On the other hand, the precoding technique is the base technology of the present study, and the PAPR reduction performance is excellent because it always outputs a constant signal without distorting the signal. However, the precoding technique presented in the previous studies has two major disadvantages. One is that as the number of parallel input branches of the system increases, additional channel signals are used instead of the input information for precoding, resulting in a loss of signal rate. The other is that the number of parallel branches increases. It is difficult to expand the system.

The present invention invents a new precoding and code selecting technique with a code rate of 1, and uses them in an MC-CDMA communication system to achieve a constant amplitude without loss of transmission speed due to a lower code rate. By outputting a signal having a fixed output, the PAPR of the output signal is always fixed to 0 dB. 2) Binary constant amplitude code division multiple access (MC-CDMA) which is easy to expand the system as the number of parallel branches increases. CA-MC-CDMA ") design method and apparatus configuration. This method can be applied without extending the bandwidth of the system.

In order to achieve the above object, the present invention uses a 2 × 2 Walsh code table to provide a signal having a length of 2 and a constant size of two binary for two parallel branch inputs. 4/4 CA-MC-CDMA with a code rate of 1 and always outputting a constant signal using a binary 2/2 CA-MC-CDMA output and a parity signal obtained from the parallel parallel signal By mixing or repeating them, the number of parallel branches input by only 4 times can be doubled, more easily and more precisely using only existing 4/4 CA-MC-CDMA. .

1 is a block diagram of a transmitter of the inventive binary 2/2 CA-MC-CDMA system.

2 is a block diagram of a receiver of the inventive binary 2/2 CA-MC-CDMA system.

3 is a block diagram of a transmitter of the inventive binary 4/4 CA-MC-CDMA system.

4 is a block diagram of a receiver of the inventive binary 4/4 CA-MC-CDMA system.

5 is a comparison table of output signals for parallel inputs of a 2/2 system.

6 is a comparison table of output signals for parallel inputs of a 4/4 system.

7 is a transmitter block diagram of an extended binary 8/8 CA-MC-CDMA system.

8 is a receiver block diagram of an extended binary 8/8 CA-MC-CDMA system.

9 is a transmitter block diagram of an extended binary 16/16 CA-MC-CDMA system.

10 is a receiver block diagram of an extended binary 16/16 CA-MC-CDMA system.

11 shows output signal level of general 8/8 MC-CDMA

12 is an output signal level of the invention 8/8 CA-MC-CDMA

13 shows the output signal level of general 16/16 MC-CDMA

14 shows the output signal level of the invention 16/16 CA-MC-CDMA

※ Explanation of the code about the main part of FIG.

(1) input data

(2) serial / parallel conversion block

(3) Code discrimination block of input signal

(4) 2 × 2 Walsh code selector

(5) Absolute value discrimination block of signal magnitude

(6) output signal

※ Explanation of codes for main parts of Figure 2

(7) received data

(8) each parallel data recovery block

(9) data determination block

(10) bottle / serial conversion block

(11) output signal

※ Explanation of the code about the main part of FIG.

(12) input data

(2) serial / parallel conversion block

(13) parity signal extraction block

(10) bottle / serial conversion block

(14) Extracted Parity Signal

(15) output signal

※ Explanation of codes for main parts of Figure 4

(16) received data

(13) parity signal extraction block

(2) serial / parallel conversion block

(10) bottle / serial conversion block

(14) Extracted Parity Signal

(8) each parallel data recovery block

(17) restored signal

※ Explanation of codes for main parts of FIG.

(18) input data

(2) serial / parallel conversion block

(19) Binary 4/4 CA-MC-CDMA Transmitter

(20) Binary 2/2 CA-MC-CDMA Transmitter

21 output signal

※ Explanation of the code about the main part of Figure 8

(22) received data

(23) Binary 2/2 CA-MC-CDMA Receiver

(24) Binary 4/4 CA-MC-CDMA Receiver

(10) bottle / serial conversion block

25 output signals

※ Explanation of codes for main parts of FIG.

(26) input data

(2) serial / parallel conversion block

(19) Binary 4/4 CA-MC-CDMA Transmitter

(27) output signal

※ Explanation of the code about the main part of Figure 10

(28) received data

(24) Binary 4/4 CA-MC-CDMA Receiver

(10) bottle / serial conversion block

(29) restored signal

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following description focuses on the parts necessary to understand the operation according to the present invention, it should be noted that the description of other parts will be omitted so as not to distract from the gist of the present invention.

In the present invention, the purpose of the binary full-width multiple code code division multiple access system using a new pre-coding technique and 2 × 2 Walsh code selection method, in the existing MC-CDMA system The high PAPR problem, which occurs when multiple parallel input data spread by different codes is merged, is solved at binary size level to enable high performance and high efficiency data transmission. In addition, it solves the problem of lowering the code rate, that is, reducing data rate or increasing bandwidth, which occurs in constant amplitude MC-CDMA using other precodings.

The use of this invention additionally solves the limitations of system extensions that have been a problem in previous studies, which are 2 lengths for two parallel branch inputs using a 2 × 2 Walsh code table. The code rate is 1 and always constant signals are obtained by using binary 2/2 CA-MC-CDMA, which outputs a constant signal in binary size, and a parity signal obtained from the input signals. By implementing 4/4 CA-MC-CDMA output and mixing or repeating it, it can be extended to systems that transmit data with increased parallel branching. As a result, the present invention solves the limitation of system expansion while maintaining the data transmission rate as it is, and solves the high PAPR problem completely by fixing the PAPR of the output signal to 0 dB at all times, and enables more stable and efficient communication.

1 shows a block diagram of a binary 2/2 CA-MC-CDMA system transmitter, which is one of the basics of the binary CA-MC-CDMA system according to the present invention. In order to achieve the above object, the input information data (1) b = { b ₀ , b ₁ } is serialized / parallel converted (2), and the values b ₀ and b respectively determined by the sign discrimination block (3). Appears as ₁ , this is a signal of ± 1. The operation of the code discrimination block 3 is as follows.

here

b ₀ is input to the 2x2 Walsh code selector and output as one selected code w _s At this time, the operation of the 2 × 2 Walsh code selector is performed as follows.

here

The signal w _s thus output is the signal determined from the absolute value determination block 5 of the signal magnitude | It is multiplied by b ₀ | and multiplied by the sign value b ₁ of b ₁ output from the sign discriminating block to become the final output signal 6 of this system.

2 shows a block diagram of a binary 2/2 CA-MC-CDMA receiver. The received data 7 R = { r ₀ , r ₁ } is multiplied by the respective Walsh codes and output by d ₀ and d ₁ by the data recovery block 8, respectively. Where the restoring equation is defined as:

Where i is the parallel data number, N is the length of the Walsh code, and k is the chip number within each code. The signal d _i restored in this way is a signal of each parallel data by the data determination block 9. Is output. At this time, the operation of the data determination block 9 is as follows.

This is again output 11 to the signal sequence originally transmitted by the parallel / serial transformation 10.

3 shows a block diagram of a binary 4/4 CA-MC-CDMA system transmitter which is another basis of the binary CA-MC-CDMA according to the present invention. In order to achieve the above object, the input information data 12 b = { b ₀ , b ₁ , b ₂ , b ₃ } is serial / parallel conversion (2), and the parity signal extractor 13 is serial / parallel. The parity signal 14 is extracted from the converted information data b ₀ , b ₁ , b ₂ , and b ₃ . The parity signal 14 at this time can be obtained by the following equation.

The parity signal 14 thus obtained is multiplied by the signal b ₃ of the fourth parallel branch. The signal input from each parallel branch always has an odd number of + 1's and -1's. The signal S, which is an odd number of + 1's and -1's multiplied by the Walsh Hardmard code w _n ( n = 1, 2, 3, 4), is always ± 2. The signal S thus obtained always has an odd number of +2 and -2 so that the first input signal can be distinguished by multiplying the parity signal 14 by the last bit, and the output signal always satisfying constant amplitude (15). ).

As an example, consider the case where the input signal b = [-1 -1 -1 -1]. The parity signal obtained by each data is -1, and the input signal converted by the parity signal is [-1 -1 -1. 1]. If the signal obtained by this process passes through WHT, the WHT output signal S is [-2 -2 -2 2], which is the same result as the first input is [-1 -1 -1 1]. To be done. The distinction between these two input signals can be made by multiplying the last bit of the signal S by the parity signal once again, so that the output signal 15 is S _out = [-2 -2 -2 -2]. In the case of other input signals, an output signal consisting of only ± 2 can be obtained by the same process.

4 shows a receiver block diagram of a binary 4/4 CA-MC-CDMA system. The received signal 16 undergoes a serial / parallel conversion (2), and from the parallel converted signals r _n ( n = 1, 2, 3, 4), the parity signal extractor 13 receives the parity signal ( 14) can be found. The parity signal 14 thus found is multiplied by the last bit r ₃ of the received signal 16 as at the transmitter, and the received signal is parallel / serial converted 10. The converted signal R 'is multiplied by each Walsh Hardmard code w _n ( n = 1, 2, 3, 4) and then by the signal recovery block 8 the signal of each parallel branch b' _n = { b ' ₀ , b Outputs ' ₁ , b' ₂ , b ' ₃ }, the parity signal 14 is multiplied by the last bit and finally reconstructed by going through the parallel / serial transformation 10. 17 B = { b' ₀ , b ' ₁ , b' ₂ , } Gets At this time, the signal recovery block 8 is the same as the above [ Equation 3 ] .

5 shows the output of each system according to the information input from the existing 2/2 MC-CDMA transmitter and the binary 2/2 CA-MC-CDMA transmitter.

6 shows the output of each system according to the information input from the existing 4/4 MC-CDMA transmitter and binary 4/4 CA-MC-CDMA transmitter.

7 shows the configuration of a binary 8/8 CA-MC-CDMA transmitter. First input signal 18 b = { b ₀ , b ₁ ,. . . , b ₆ and b ₇ } are inputted into two binary 4/4 CA-MC-CDMA transmitters 19 by 4 bits after serial / parallel conversion (2), and each binary 4/4 CA is inputted. The signal S _n ( n = 0, 1) output from the MC-CDMA transmitter 19 is input to one binary 2/2 CA-MC-CDMA transmitter 20 again and has an output signal 21 having a constant amplitude. Is sent. Since the signals S _n ( n = 0, 1) output from the two binary 4/4 CA-MC-CDMA transmitters 19 are signals each of length 4 and consist of ± 2, one binary 2/2 The output signal 21 passed through the CA-MC-CDMA transmitter 20 has a length of 8 and is ± 2.

8 shows a binary 8/8 CA-MC-CDMA receiver. Received data 22 R = { R ₀ ,. . . , R ₇ ) is converted into two bit strings R ₀ and R ₁ of length 4 and ± 2 by one 2/2 CA-MC-CDMA receiver 23, which in turn is two binary 4 / 4 CA-MC-CDMA receivers 24 are respectively inputted and output through 8 parallel branches. This parallel data is represented by the final reconstructed signal 25 after the parallel / serial transformation 10.

9 shows the configuration of a binary 16/16 CA-MC-CDMA transmitter. First input signal 26 b = { b ₀ , b ₁ ,. . . , b ₁₄ , b ₁₅ } are inputted into four binary 4/4 CA-MC-CDMA transmitters 19 by 4 bits after serial / parallel conversion (2), and each binary 4/4 CA is inputted. The signal S _n = { S _{n, 0} , S _{n, 1} , S _{n, 2} , S _{n, 3} } ( n = 1, 2, 3, 4) output from the MC-CDMA transmitter 19 is again one. The output signal 27 having a constant amplitude is input to the binary 4/4 CA-MC-CDMA transmitter 19 of S _tx = { S _{tx, 0} , S _{tx, 2 ,.} . . , S _{tx, 14} , S _{tx, 15} }. Since the signals S _n ( n = 1, 2, 3, 4) output from the four binary 4/4 CA-MC-CDMA transmitters 19 are signals each of length 4 and consist of 12, one binary signal is again used. The output signal 27 S _tx through the 4/4 CA-MC-CDMA transmitter 19 is 16 in length and is made of ± 4.

10 shows a binary 16/16 CA-MC-CDMA receiver. Received signal 28 R = { R ₀ ,. . . , R ₁₅ } is a four-bit string of length 4 and composed of ± 2 by one binary 4/4 CA-MC-CDMA receiver 24, R ' _n = { R' _{n, 0} , R ' _{n, 1} , R ' _{n, 2} , R' _{n, 3} }, which is input to four binary 4/4 CA-MC-CDMA receivers 24, respectively, and output as 16 parallel branches. This parallel data is passed through a parallel / serial transformation (10) and then finally recovered signal (29) B = { b ' ₀ ,. . . , b _'15 }.

FIG. 11 shows the level of a transmission signal output from a conventional MC-CDMA transmitter, and the number of parallel branches used is eight. As shown in the figure, it can be seen that the signal fluctuates greatly from -8 to +8, and because of this large change in signal level, it has a large PAPR.

12 shows the output signal level of the binary 8/8 CA-MC-CDMA invented in this study. Again, the number of parallel branches used is 8, and the signal appears at binary levels of +2 and -2 as shown. It has a PAPR of 0 dB and no nonlinear distortion occurs through the HPA.

FIG. 13 shows the level of the transmission signal output from the conventional MC-CDMA transmitter, and the number of parallel branches used is 16. FIG. As shown in the figure, it can be seen that the signal fluctuates greatly from -16 to +16. Since the large signal level changes, the signal has a large PAPR.

14 shows the output signal level of the binary 16/16 CA-MC-CDMA invented in this study. Again, the number of parallel branches used is 16, and the signal appears at binary levels of +4 and -4 as shown. It has a PAPR of 0 dB and no nonlinear distortion occurs through the HPA.

As described above, the present invention applies a new precoding technique and a code selecting technique to an existing 4/4 MC-CDMA system to always output a signal of a constant size. There is no transmission rate drop or bandwidth expansion problem, and the system parallel branch number is binary 4 / by using mixed or repeated use of binary 2/2 CA-MC-CDMA and binary 4/4 CA-MC-CDMA. 4 Can be extended more precisely when using only CA-MC-CDMA. The present invention solves the problem of data rate degradation or bandwidth expansion of the system and system scalability for more parallel branches, and by outputting a signal with a PAPR of 0 dB, nonlinear distortion in the high power amplifier (HPA) is eliminated. It does not occur, resulting in more efficient and stable BER performance. In addition, the high-power amplifier can be used at maximum power efficiency.

Claims (2)

In the structure and method of a binary constant amplitude multiple code code division multiplexing (CA-MC-CDMA) communication system proposed by the present invention, 1) a method and apparatus for implementing a binary 2/2 CA-MC-CDMA transmitter using a 2 × 2 code selector; 2) a method and apparatus for implementing binary 4/4 CA-MC-CDMA using a precoding scheme having a code rate of 1; 2) A method and apparatus for expanding the number of parallel branches, or transmission capacity, based on binary 2/2 CA-MC-CDMA and binary 4/4 CA-MC-CDMA, by mixing or repeating them. Binary 2/2 CA-MC-CDMA 2 × 2 code selecting scheme and binary 4 / In the configuration of a transmitting and receiving device by a new precoding scheme having a code rate of 4 CA-MC-CDMA and a method and apparatus for extending the number of parallel branches, A) method and apparatus for determining code selection and phase by maintaining the magnitude and sign of signals input to the transmitter of 2/2 CA-MC-CDMA, B) an apparatus for obtaining a parity signal from signals input to a transmitter of 4/4 CA-MC-CDMA, and a method and apparatus for multiplying the same with a signal of a fourth parallel branch; C) In a 4/4 CA-MC-CDMA transmitter, when the input signal converted by the parity signal is output through a WHT (Walsh Hardmard transform), the parity signal is again added to the last bit of the output signal. Process and apparatus for distinguishing parity signals used by multiplying by D) A method and apparatus for finding a parity signal used in a transmitter from each parallel data by serially / parallel converting a signal input to a receiver of 4/4 CA-MC-CDMA. E) a method and apparatus which is doubled in size by inputting output signals of two identical CA-MC-CDMA transmitters into one 2/2 CA-MC-CDMA. F) A method and apparatus for expanding to four times the size by inputting the output signals of four identical CA-MC-CDMA transmitters into another CA-MC-CDMA.