Research On Coding And Decoding With Cognitive Side Information In Transmitter

With the rapid development of wireless communication technology, the number of wireless services increases rapidly, which makes the crisis of the spectrum resource more and more serious. Cognitive radio network technology can improve the spectrum efficiency and increase the channel capacity. Thus, it has become a hot research topic in the field of wireless communications in recent years.This paper mainly studies the overlay cognitive radio network, where the cognitive user and the primary user transmit concurrently in the same spectrum. The cognitive transmitter has the non-causal knowledge of the primary user’s codebook and message, which enables the cognitive user allocate part of its transmit power to relay the primary user’s transmitted signal in order to avoid the performance loss of the primary user. Meanwhile, the cognitive user employs advanced coding technology to transmit its own message with the remaining power in order to improve the performance of the cognitive system.Dirty paper coding is a kind of nonlinear precoding technology and is often used to study the overlay cognitive radio channel. When the channel interference is known at the transmitter, it can be completely eliminated by using dirty paper coding technology. This paper studies the theory of the dirty paper coding algorithm, analyses its channel capacity and describes three existing schemes applicable to the cognitive radio channel. However, due to the use of the iterative decoding algorithm, these schemes have a high complexity.Thus, this paper proposes a dirty paper coding scheme with low complexity. This scheme is applied to the basic cognitive radio channel with one cognitive user. Through the shaping code selection, it is able to change the size of the constellation self-adaptively according to the interference power. The decrease in the search space of the optimal codes reduces the complexity of the cognitive system. Simulation results show that the proposed scheme achieves an excellent performance with a low complexity.Furthermore, this paper proposes a dirty paper coding scheme applied the MIMO cognitive radio channel with multiple cognitive users. Based on the zero-forcing dirty paper coding and multi-user trellis shaping technology, it can eliminate the interference caused not only by the primary user but also by other cognitive users. The performance of this scheme is compared using simulations with that employing conventional trellis shaping and it achieves excellent tradeoff between performance and complexity.