Cooperative Communication Relay Technology Research

With the rapid development of wireless mobile communication technology in recent years, MIMO becomes one of the key technologies for the next generation mobile communications, since it provides a capability to approach Shannon bound. However, it is difficult to configure MIMO for the mobile terminals at present because of its rigorous demand for the distance between the antenna units. Therefore, the researchers bring forward the new concept, Cooperative Communication, in which inter-help among single-antenna terminals with longer spatial distance is employed to implement communication. Cooperative communication can not only increase the spectrum efficiency, but also be capable of employing distributed spatial diversity to combat the deep fading.Relay selection is a crucial challenge in cooperative communication. There are some disadvantages in present relay selection algorithms such as long time delay in the algorithm based random geographic forwarding (RaGeF) and unsustainable for mobility in the algorithm based on average receive SNR. While the third algorithm based instantaneous channel state information is very complicated because of the requirement for real time channel fading factors. The following contents are the main work in this thesis:1,A new relay selection algorithm based on receive-power of nodes is proposed with the advantage of low complexity and accommodation for mobile communication networks. We compare the performance of the proposed algorithm in Rayleigh channel with the algorithm based instantaneous CSI using simulations. The simulation results indicate that the new algorithm without the requirement for channel estimation performs the similar performance, such as spectrum efficiency and bit error rate, as the scheme based CSI in cooperative communication.2,The performance of cooperative Turbo codes with the different digital modulation schemes is studied. Code cooperation, which is the combination of channel coding and cooperative communication, becomes one of the protocols with best link quality, because it avoids the disadvantages from amplify-and-forwarding and decode-and-forwarding modes. With excellent error checking and correcting capabilities, Turbo code becomes the channel coding standardization for next generation wireless communication systems. The performance for Turbo code with BPSK modulation schemes is analyzed by using 3GPP LTE 36.212 coding structure. Then a cooperative-Turbo scheme is introduced by jointly designing the cooperative communication and Turbo code when the proposed relay selection algorithm is taken into account. Simulation results show that there is at least 0.5dB gain for this new scheme with comparison to present ones under the BPSK modulation scheme when the SNR exceeds 2dB. Finally the performance of cooperative Turbo codes is analyzed and simulated under the QPSK and 16QAM modulations.