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Space-time spreading method of CDMA system

A space-time, spread-spectrum technology, applied in transmission systems, code division multiplexing systems, electrical components, etc., can solve problems such as difficult implementation, engineering implementation difficulties, and mobile station difficulties, so as to improve the quality of information transmission and eliminate Multiple access interference, the effect of improving system bit error rate performance

Inactive Publication Date: 2009-07-08
BEIJING JIAOTONG UNIV
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Problems solved by technology

[0010] In the existing space-time spread spectrum technology (STS), the distance between the transmitting antennas of the base station must be greater than 10-15 times the wavelength of the radio frequency signal to ensure that the signals reaching each unit of the antenna array are not correlated with each other, which causes difficulties in engineering implementation
Because due to objective conditions, the distance between base station transmitting antennas may not meet the aforementioned requirements
The existing space-time spread spectrum technology with multiple transmitting antennas requires the mobile station to have multiple antennas, which brings great difficulties to the technical realization of the mobile station, increases the cost of the mobile station, and increases the size of the mobile station
The receiving despreading algorithm in the aforementioned literature requires a large number of matrix operations, so it is difficult to implement

Method used

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Embodiment Construction

[0046] refer to figure 1 , the invention is a space-time spread spectrum method for downlink of CDMA system. The system of the present invention includes a base station and a plurality of mobile stations. The base station has two antennas, and each mobile station has only one antenna. The base station performs transmit diversity on the multi-user data flow b at the baseband, and its transmit diversity circuit includes down-sampling modules 111 and 112, a delay module 122, spreaders (multipliers) 131, 132, 133, 134, and adders 141 and 142 .

[0047] combine figure 2 , the steps of base station baseband processing are:

[0048] 1) Step 21: Divide each user's data stream into odd data stream and even data stream

[0049]The data stream b of each user is divided into two paths, and the odd data stream b1 and the even data stream b2 are obtained through the down-sampling modules 111 and 112 . Data stream b is BPSK modulated.

[0050] 2) Step 22: Adjust the time difference b...

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Abstract

The invention relates to a space-time spread spectrum method for a CDMA system. The transmitted signal is down-sampled into an odd data stream and an even data stream, and the time difference between the even data stream and the odd data stream is adjusted through a delay module, and then the same spread The two orthogonal spread spectrum codes obtained by the spectral code are spread, and then transmitted by two antennas. The receiving end despreads the received signal in two ways, weights the obtained first despread signal and the second despread signal respectively with channel parameters, obtains a combined signal of the first and second channel parameter weighted signals, and divides the first despread signal into The first and second combined signals of the first and second channel parameter weighted signals are respectively judged to obtain restored data. The invention also provides a receiving circuit of a mobile station using the method, which utilizes one antenna and two-way matched filtering to restore parity data streams. The invention enables the mobile station to obtain diversity gain when receiving data, improves the information transmission quality of the system, and simplifies the design of the receiving circuit.

Description

technical field [0001] The invention relates to a space-time spread spectrum method of a CDMA system, which belongs to the field of mobile communication. Background technique [0002] The direct spread spectrum technology of multiple transmit antennas is used in the forward and reverse links of CDMA system, which can effectively improve the system performance. CDMA1X uses direct spread spectrum transmit diversity technology, which has two methods: [0003] (1) One is Orthogonal Transmit Diversity OTD (Orthogonal TransmitDiversity) [0004] The method is that the CDMA base station first separates the data streams and then spreads the two data streams with different orthogonal Walsh codes, and transmits them through two transmitting antennas of the base station. [0005] (2) The other is the space-time spread spectrum diversity method STS (Space Time Spreading) [0006] The CDMA base station uses two spatially separated antennas to transmit the interleaved data, uses the sa...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04J13/02H04B1/16H04B1/04
Inventor 肖扬
Owner BEIJING JIAOTONG UNIV
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