A Cooperative Diversity Transmission Method Based on Random Unitary Matrix Modulation

Abstract

The invention discloses a cooperative diversity transmission method based on random unitary matrix modulation. Received signals on antennas of relay nodes are transmitted by a random unitary matrix, and the signals of a plurality of time slots are linearly combined by an orthogonal spreading code sequence. The signals transmitted by a relay occupy limited time slots for transmission by conjugate processing. Real parts and imaginary parts of the received signals are independently decoded by the aid of complex signal properties. By properly processing the received signals in two time slots at destination nodes, real parts and imaginary parts of the transmitted signals can be independently decoded, and decoding complexity of an original scheme is effectively reduced. Improvement of system performances is further verified by analyzing the upper bound of a pairwise error ratio. Simulation results indicate that the bit error ratio of the cooperative diversity transmission method is reduced by about 3dB or 5dB as compared with an MRC-DSTC (maximum-ratio combining distributed space-time coding) algorithm when a system is provided with a single relay node and two relay nodes.

Description

technical field [0001] The invention belongs to the technical field of multi-antenna wireless communication, and relates to a cooperative diversity transmission method based on random unitary matrix modulation. Background technique [0002] Cooperative diversity technology, which uses multiple nodes to cooperate with each other in wireless networks, has gained widespread attention in recent years because it can obtain space diversity and effectively improve system performance. [0003] The Distributed Space-Time Coding (DSTC) proposed in [1] adopts the cooperative design method of relay nodes without channel information in the network, and independently processes the received signal at each relay antenna. On the basis of DSTC, many DSTC coding design methods have emerged. Literature [2] is a differential transmission scheme based on DSTC, which is a differential transmission scheme when the relay node and the destination node have no channel information. Document [3] is bas...

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Problems solved by technology

However, in the above DSTC coding scheme, since each relay antenna processes the received information independently, the system performance cannot be optimal when the relay node has multiple antennas. In order to solve this problem, literature [4 ] The DSTC maximum ratio combining (MRC-DSTC) scheme proposed by the relay node uses the channel information to perform maximum ratio combining on the received signals, thereby improving the performance of the wireless relay network

However, this scheme constructs the processing matrix of the relay node based on the orthogonal design theory, and there is a zero matrix in it, which makes the relay node fail to effectively forward the received signal; in addition, in order to meet the conditions of the orthogonal design, this scheme also It is required that the number of transmission slots is not less than the number of relay antennas, which makes the number of transmission slots limited by the number of relay antennas

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