Research On Coding And MAC Protocol For Multi-Source Node Relay Network

With the rapid development of wireless communication industry, in both civil and military field, relay network has been widely applied, for instance, the satellite relay network and wireless sensor relay network .Currently, with the improvement of data storage capacity,compute capability and wireless communications capabilities of source node, security issues in data processing and power consumption issues for wireless communications have become a focus concern of both domestic and foreign researchers.Generally, data from source nodes require interaction.These sources between nodes cannot communicate with each other directly. They need the help of source node forwarding.The emergence of the network coding theory changed the basic idea that the data packets in traditional communication network should be stored and forwarded by router, and it also improved the system performance and network throughput. But because of the characteristic of the broadcasting, the security abuse of applications based on network coding should not be ignored. The openness of the way of eavesdropping and encoding rules makes it much easier to decipher the message of other nodes when there is eavesdropper in the net. It is a major threat to the transmission of privacy data. Therefore we should use Coding algorithm with high security in relay network. In terms of energy consumption, the source node energy is usually limited, the majority of it is occupied in wireless communication between nodes, the computing performance of source node and the limitations of storage size. So we can't achieve complex calculation and large data storage. In order to improve network throughput,latency and other performance we need well-designed MAC layer transport protocols to save energy consumption.This paper studied the performance of two-way relay network in terms of the above two aspects. First, according to the source node for multi-way relay network system model, it analyzed the energy consumption under the condition whether use the network coding or not.Through theoretical analysis and simulation results shows that under the same network parameters, the application of network coding can achieve better energy efficiency and minimize the energy consumption of network which use the network coding under the condition that the total packet arrival rate for the given value and the data packet arrival rate in each of source network node are equal.Secondly, this paper proposed a security network coding algorithm based on singular value decomposition to accomplish exchanging the data of source nodes. The simulation showed that, at the same monitor error rates, traditional XOR bit network coding algorithm has the same bit error rate of decoding and monitor error rate, and the algorithm this paper proposed has a rate error rate over 40% basically, which is of good security performance compared to traditional algorithm.Finally, in the aspect of MAC layer data transmission, according to the particularity of security network coding algorithm based on singular value presented in this paper, we propose that each node transmits a data frame to a relay node at a time period, the relay node carries out the data frame of all the source nodes in the network coding, and then broadcasts the encoded data frame to all the source nodes. Based on the structure of the multi-source node bidirectional relay network system model and security network coding algorithm based on singular value mentioned in this paper, we propose a MAC protocol based on energy optimization. The MAC protocol based on energy optimization is introduced from the aspects of frame structure, CSMA/CA channel competition mechanism, data transmission and channel access method. This MAC protocol using CSMA / CA mechanism channel competition in super active part of the frames. When after successful data transmission, enter a state of dormancy, until it receives a relay node broadcasts data, reopen channel competition.This protocol can be applied to relay networks such as satellite networks, wireless sensor networks and so on, and it also greatly saves the source node energy. By compared the MAC protocol based on energy optimization with IEEE 802.15.4 MAC protocol on simulation platform of OMNET++, we found that the throughput and delay of MAC protocol based on energy optimization and 802.15.4 MAC IEEE protocol are equal. But with the protocol based on energy optimization the slot could save 48.13%-76.56% with same network parameter and has better energy saving. Considering the system performance, the design of the frame period and the active part length of the frame should be considered in the design of the network size,the length of the data frame and the total time delay.