JP2004357104A - Cdm transmitter and receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CDM (Code Division Multiplexing) transmitter and receiver capable of improving interruption due to rainfall without accompanying drastic increase of hardware. <P>SOLUTION: The CDM transmitter which transmits information data by performing code diffusion is provided with an interleave means for interleaving the code-diffused information data, and transmits the interleaved information data. The CDM receiver is provided with a de-interleave means for receiving the interleaved information data after the code diffusion is performed and de-interleaving the received information data, and performs code diffusion of the de-interleaved information data. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a digital transmission technique, and more particularly, to a CDM (Code Division Multiplexing) transmitting apparatus and a receiving apparatus for transmitting information data by spreading the code.
[0002]
[Prior art]
FIG. 1 is a block diagram illustrating an example of a configuration of a conventional CDM transmission system. Data is transmitted from the CDM transmitting device 1 to the CDM receiving device 3 via the transmission path 2. The CDM transmission device 1 includes an error correction coding unit 4, a code spreading unit 5, and a quadrature modulation unit 6. The CDM receiving device 3 includes an orthogonal demodulation unit 7, a code despreading unit 8, and an error correction decoding unit 9.
[0003]
In the CDM transmitting apparatus 1, the transmission data is error-correction-coded by the error-correction coding unit 4, and then supplied to the code spreading unit 5. The code spreading section 5 performs code spreading on the transmission data. FIG. 2 is a diagram illustrating code spreading in the code spreading unit 5. In this example, four orthogonal spreading codes W1 (1, 1, 1, 1), W2 (1, -1, 1, -1), and W3 (1, 1, -1, -1) of four lengths are used. And transmission data D of 4-bit data (1, -1, 1, 1) subjected to error correction coding using W4 (1, -1, -1, 1). First, the 4-bit data is separated into four systems, one bit at a time, and each is multiplied by a spreading code W1, W2, W3, and W4 to obtain 4-bit data. Furthermore, these 4-bit data of four systems (1, 1, 1, 1), (-1, 1, -1, 1), (1, 1, -1, -1) and (1, -1, -1) , -1, 1) are added for each same bit position to obtain one system of transmission data (2, 2, -2, 2). The transmission data obtained in the code spreading section 5 is orthogonally modulated by the orthogonal modulation section 6, and transmitted to the transmission line 2 as a digital modulation wave.
[0004]
The CDM receiving device 3 receives the digitally modulated wave transmitted through the transmission path 2. First, a case where no error occurs on the transmission path 2 and the same data as the transmission data transmitted by the transmission device 1 is received will be described. The orthogonal demodulation unit 7 orthogonally demodulates the received data and supplies the data to the code despreading unit 8. The code despreading unit 8 performs code despreading on the received data. FIG. 3 is a diagram illustrating code despreading performed in the code despreading unit 8. The 4-bit data (2, 2, -2, 2) is separated into four systems, each of which is multiplied by the same spreading code W1, W2, W3, and W4 as in the CDM transmitting apparatus 1, and is composed of four data each. (2,2, -2,2), (2, -2, -2, -2), (2,2,2, -2) and (2, -2,2,2) are obtained. Further, with respect to the data of the four systems composed of these four data, an average value of the four data is obtained for each system, and when the polarity is positive, the threshold value is determined as 1, and when the polarity is negative, -1 is determined. , The same data as the transmitted data, ie, 1, -1, 1, 1 can be obtained. The data for which the threshold value has been determined is subjected to error correction processing by the error correction code decoder 9 and then output. It should be noted that the threshold value determination process indicated by the dotted line in FIG. 3 is unnecessary when the error correction code decoding in the error correction decoding unit 9 is performed by soft decision.
[0005]
Next, a case where an error is mixed in a signal in the transmission path 2 will be described. FIG. 4 is a diagram illustrating the code despreading process performed in the code despreading unit 8 in such a case. In this example, it is assumed that an error is mixed in the second data of the transmission data (2, 2, -2, 2) and the reception data becomes (2, 0, -2, 2). As in the example of FIG. 3, the received data is divided into four systems, each of which is multiplied by a spreading code W1, W2, W3, and W4, and is composed of four data (2, 0, -2, 2), respectively. (2,0, -2, -2), (2,0,2, -2) and (2,0,2,2) are obtained. With respect to the data of four systems composed of these four data, when the average value of the four data is obtained for each system, the average value is 0.5, -0.5, 0.5, 1.5. , (1, -1, 1, 1), indicating that the same error-free data as the transmitted data can be obtained.
[0006]
As described above, the CDM transmission has a function of recovering data even if data is erroneously mixed due to some disturbance or interruption on the transmission path, and is used in mobile communication or the like which is easily affected by fading or the like. I have. On the other hand, in satellite communication and satellite broadcasting, especially when a high frequency band is used, interruption due to rain attenuation is likely to occur. At present, there are few examples in which CDM transmission is applied to such satellite communication and satellite broadcasting. However, it is considered that transmission characteristics can be improved by using CDM technology, and 2.6 GHz band satellite audio broadcasting is considered. Will use CDM (service started in spring 2004). However, the interruption due to rain attenuation occurs for a very long time of several minutes to several hours. If the CDM technology is applied, a very long spreading code is used, and the number of multiplexed codes is reduced in order to suppress a decrease in efficiency. We have to increase it accordingly. As an example, in a CDM transmission apparatus that transmits data at a bit rate T = 111 [bits / second], when spreading at a frame period F = 10 [time] = 36000 [seconds], the spreading code length N is N = F. -T = 36000 [seconds]-111 [bits / second] = 4000000, and the number of multiplexed codes must be 4,000,000 in order not to lower the efficiency. Have difficulty.
[0007]
[Problems to be solved by the invention]
As described above, when the conventional CDM technology is used to obtain an improvement effect against a long-term interruption such as rain attenuation, a very long spreading code is used, and the number of multiplexed codes is reduced in order to suppress a decrease in efficiency. However, there is a problem that the hardware to be used becomes extremely large because the number of hardware must be increased accordingly.
[0008]
An object of the present invention is to provide a CDM transmitting device and a receiving device that can improve rainfall cutoff without a significant increase in hardware.
[0009]
[Means for Solving the Problems]
The CDM transmitting apparatus according to the present invention includes an interleaving means for interleaving the code-spread information data, and transmits the interleaved information data. In this way, continuous signal interruption is converted into a short-time signal interruption group, and the effect of suppressing interruption can be enhanced.
[0010]
Another embodiment of the CDM transmitting apparatus according to the present invention is characterized in that the interleaving means includes a memory element having a size which is an integral multiple of the length of a code used for code spreading of the information data. By doing so, the effect of the CDM can be enhanced.
[0011]
Still another embodiment of the CDM transmitting apparatus according to the present invention is characterized in that a unit of writing to a memory element of the interleaving means is a code length used for spreading the information data.
[0012]
The CDM receiving apparatus according to the present invention includes deinterleaving means for receiving interleaved information data after being code-spread, deinterleaving the received information data, and code-despreading the deinterleaved information data. It is characterized by the following. In this way, continuous signal interruption is converted into a short-time signal interruption group, and the effect of suppressing interruption can be enhanced.
[0013]
Another embodiment of the CDM receiving apparatus according to the present invention is characterized in that the deinterleaving means includes a memory element having a size of an integral multiple of a code length used for code despreading of the information data. By doing so, the effect of the CDM can be enhanced.
[0014]
Still another embodiment of the CDM receiving apparatus according to the present invention is characterized in that a unit of reading from the memory element of the deinterleaving means is a code length used for code despreading of the information data.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 5 is a block diagram showing an example of a configuration of a CDM transmitting device and a receiving device according to the present invention. Data is transmitted from the CDM transmitting device 11 to the CDM receiving device 13 via the transmission path 12. The CDM transmission device 11 includes an error correction coding unit 14, a code spreading unit 15, an interleave unit 16, and a quadrature modulation unit 17. The CDM receiving device 13 includes an orthogonal demodulation unit 18, a code despreading unit 19, a deinterleave unit 20, and an error correction decoding unit 21. The error correction encoding unit 14, the code spreading unit 15, the orthogonal modulation unit 17, the orthogonal demodulation unit 18, the code despreading unit 19, and the error correction decoding unit 21 in the CDM receiving device 13 in the CDM transmitting device 11. Is an error correction coding unit 4, a code spreading unit 5, a quadrature modulation unit 7, a quadrature demodulation unit 7 in the CDM receiving device 3, and a code despreading unit 8 in the conventional CDM transmitting device 1 shown in FIG. And the error correction decoding unit 9 may be the same. Here, it is assumed that they are the same for ease of explanation.
[0016]
In the CDM transmitting apparatus 11, the transmission data is error-correction-coded by the error-correction coding unit 14, and then supplied to the code spreading unit 15. The code spreading section 15 performs code spreading on the transmission data. The operation up to this point is the same as that of the conventional CDM transmitting apparatus described with reference to FIG. Next, the code-spread transmission data is subjected to an interleaving process in an interleaving section 16. In this example, the interleave unit 16 includes a memory of 4 columns × 1,000,000 rows so that data generated by one code spreading occupies one row of the memory. FIG. 6 is a diagram illustrating such an interleaving process. The transmission data is written from the top row of the memory of 4 columns × 1,000,000 rows, written to the bottom row, and then read from the leftmost column of 4 columns × 1,000,000 rows as shown in FIG. 6B. The interleaved transmission data is quadrature-modulated by the quadrature modulation unit 16 and transmitted to the transmission line 2 as a digital modulation wave.
[0017]
The CDM receiving device 13 receives data in the form of a digitally modulated wave that has passed through the transmission path 2. The orthogonal demodulation unit 18 orthogonally demodulates the received data and supplies the data to a deinterleave unit 19. The deinterleave unit 19 performs a deinterleave process. In this example, the deinterleave unit 19 includes a memory of 1,000,000 columns × 4 rows so that data processed by one code despreading occupies one column of the memory. FIG. 7 is a diagram illustrating such a deinterleaving process. The received data is written from the top row of the memory of 1,000,000 columns × 4 rows, written to the bottom row, and then read from the leftmost column of the memory of 1,000,000 columns × 4 rows. The deinterleaved received data is subjected to code despreading in a code despreading unit 20 and further error correction decoded in an error correction decoding unit 21.
[0018]
By performing such interleave processing and deinterleave processing, for example, when continuous interruption of 10,000,000 bits occurs on the transmission path, bit errors in the deinterleave section are dispersed in the row direction as shown in FIG. become. At this time, only one bit error occurs per column which is a unit of the code despreading process, and the bit error after the code despreading is improved as compared with the above-described conventional example. In the above configuration (spread code length N = 4, interleave depth x = 1,000,000), if the bit rate T = 111 bits / second, the frame period F after spreading is F = N / T × x = 36000. [Second], which has the same diffusion effect as the example described in [0006].
[0019]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the CDM transmission apparatus and the receiving apparatus which can improve a rainfall cut-off without accompanying a large increase in hardware are provided.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an example of a configuration of a conventional CDM transmission system.
FIG. 2 is a diagram illustrating code spreading.
FIG. 3 is a diagram illustrating code despreading.
FIG. 4 is a diagram illustrating code despreading when an error is mixed in a signal.
FIG. 5 is a block diagram showing an example of a configuration of a CDM transmitting device and a receiving device according to the present invention.
FIG. 6 is a diagram illustrating an interleaving process.
FIG. 7 is a diagram illustrating a deinterleaving process.
FIG. 8 is a diagram illustrating a distribution of bit errors in a deinterleave unit.
[Explanation of symbols]
1, 11 CDM transmitting device 2, 12 Transmission path 3, 13 CDM receiving device 4, 14 Error correction coding unit 5, 15 Code spreading unit 6, 17 Quadrature modulation unit 7, 18 Quadrature demodulation unit 8, 20 Code despreading unit 9, 21 error correction decoding section 16 interleave section 19 deinterleave section

Claims (6)

A CDM transmitting apparatus for code-spreading and transmitting information data, comprising: interleaving means for interleaving the code-spread information data, wherein the CDM transmitting apparatus transmits the interleaved information data. 2. The CDM transmitting apparatus according to claim 1, wherein said interleaving means includes a memory element having a size of an integral multiple of the length of a code used for code spreading of said information data. 3. The CDM transmitting apparatus according to claim 2, wherein a unit of writing to the memory element of the interleaving means is a code length used for spreading the information data. CDM receiving apparatus comprising: deinterleaving means for receiving interleaved information data after being code spread and deinterleaving the received information data, and code despreading the deinterleaved information data. . 5. The CDM receiving apparatus according to claim 4, wherein said deinterleaving means comprises a memory element having a size of an integral multiple of a code length used for code despreading of said information data. . 6. The CDM receiving apparatus according to claim 5, wherein a unit of reading from the memory element of the deinterleaving means is a code length used for code despreading of the information data.

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