A Study Of Cooperative Relay Scheme Between Notes In CRAHN And Physical Layer Implementation

In recent years, with the radio spectrum resources become increasingly scarce, CRAHN network has been a research hotspot. Each node in this network has the capability of spectrum sensing, they are equal, and can form the network in self-organizing and multi-hop. CRAHN is suitable for complex electromagnetic environment, it can realize the Multi-hop wireless broadband systems in an adaptive way, which has broad application prospects in emergency communications.This paper researches on Cooperative relay strategy based on a multi-level clustering CRAHN network. Firstly it introduces the related theory of cooperative communication, describes the key protocol of traditional 802.11 MAC, summarizes the classification of the relay technology, introduces two kinds of traditional cooperative relay strategy, and analyzes their respective advantages and disadvantages.Secondly, in view of the existing cooperation strategy based on relay list, this paper proposes a cooperative relay scheme for multi-level clustering network, and carries on the discussion divided into intra cluster and inter cluster relay scheme. The new scheme according to the neighbor table information uses different strategies in different channel conditions for relay cooperation opportunities and the optimal relay node selection. In addition, compared with the intra cluster relay, the relay node of inter cluster relay requires the ability to send and receive frequency switching. Finally, the simulation results show that the proposed scheme has certain practical application value.Thirdly this paper focuses on the cooperative relay strategy of real-time services within the period of CP in intra cluster communication. In view of the traditional CoopMAC protocol, this paper has proposed cooperative relay scheme based on the instant channel information and the node residual energy.In this scheme, there is no need to maintain a relay list, which can select relay node dynamically and avoid over using of the node which has good channel condition. Simulation results show that under the circumstance of the slightly decline in the network saturation throughput performance, it can greatly increase the survival time of network.Finally, this paper focus on the physical layer key technology associated with the cooperative communication. It has designed a cooperative control module, which completes part of the operation with receiving date in the physical layer, and only the processing result is sent in the form of reports to the MAC layer, in order to save the signal processing time. The physical layer adopts OFDM modulation technology, it is a kind of multi carrier transmission scheme which can effectively counter the narrowband noise and multipath effect. This paper introduces the methods of channel decoding module and their hardware implementation detailly, which is closely related with Cooperative Communications. And has simulated in FPGA environment. The simulation results show that the design of the module meets the requirement of experiment.