Design method for two-level precodes of cognitive MIMO communication system

Abstract

The invention discloses a design method for two-level precodes of a cognitive MIMO communication system and relates to the technical field of the cognitive MIMO communication systems. In the MIMO communication system, a cognitive user adopts an opportunistic access mode to use space sub-channels of a main user, and interference, generated on the main user, of the cognitive user is reduced through an interference alignment method; interference alignment is achieved through precode designing of all transmitting ends of the cognitive user. According to the transmission performance of the main user, a precode matrix can be designed on the basis of transmission channel matrix singular value decomposition, and power distribution of the transmitting ends is achieved by the utilization of a water-filling method; the design for the two-level precodes is performed on the transmitting ends of the cognitive user, the first level precode is used for aligning the interference generated, on the main user, of the cognitive user to the space sub-channels available for the main user, and the second level precode is used for promoting the transmission performance of the cognitive user. By the adoption of the design method for the two-level precodes, under the condition that the interference, on the main user, of the cognitive user is reduced, the transmission performance of the cognitive user is guaranteed.

Description

technical field [0001] The invention relates to the technical field of cognitive MIMO communication, in particular to a design method of a two-stage precoding that can take into account cognitive user transmission performance and interference alignment in a cognitive MIMO communication system. Background technique [0002] With the rapid development of wireless communication technology, the demand for wireless spectrum resources has increased accordingly, resulting in increasingly tight spectrum resources suitable for wireless communication. Cognitive radio realizes dynamic spectrum through spectrum sensing and adjusting system parameters according to the radio frequency environment. Access and intelligent spectrum allocation to improve spectrum utilization; MIMO (Multiple-Input / Multiple-Output) system is considered to be another technology to improve spectrum utilization. [0003] The MIMO system optimizes the multi-path wireless channel, transmission and reception as a who...

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Problems solved by technology

[0006] Also, "Secondary Precoding Transmission Method Based on Zero Subspace Technology in Cognitive Wireless MIMO System" (Application No.: 200810042032.2, Shanghai Wireless Communication Research Center), requires the cognitive user transmitter to perceive the primary user's transmission signal and estimate Corresponding covariance matrix, the subspace technique is applied to the covariance matrix, and the corresponding noise subspace is estimated to obtain the null space, and the dimension of the null space and the use status of the spatial subchannel are determined by using the information theory criterion, which can be obtained by The null space of the cognitive user is used to design the precoding matrix of the sending end of the cognitive user. This transmission method eliminates the interference of the cognitive user to the primary user, but does not consider the transmission channel of the cognitive user itself and its own transmission performance.

[0007] According to the literature Amir, M., EI-Keyi, A., Nafie, M.P: 'Constrained Interference Alignment and the Spatial Degrees of Freedom of MIMO Cognitive Networks' (IEEE Trans.Inf.Theory, 2011, 57, (5), pp.2994-3004), in the case of cognitive users and primary users coexisting in the channel, the cognitive user sender is limited by external constraints to reduce the interference to the primary user sender by designing precoding, and studied The spatial degree of freedom of the cognitive MIMO system, this document only discusses the reduction of interference received by the primary user and the degree of freedom achieved by the cognitive user, but does not discuss the transmission performance of the primary user and the cognitive user

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