Research On Transmission And Physical Layer Security For Wireless Two-way Relay Communication

The concept of Network Coding (NC) was proposed in2000. An intermediate node processes data streams by linear or nonlinear transformation, and then forwards the data to the next node. The destination node can recover the data through the appropriate operation by means of the known information. Theory and simulation have proved that NC can improve resource efficiency and make network throughput achieve the theoretical upper bound of transmission capacity. Two-Way Relay Channel (TWRC) is a typical application of sence for NC. Due to broadcast characteristic of wireless channel, NC can significantly improve spectrum efficiency of TWRC.Compressive Sensing (CS) is a new theory evolved from signal sparse decomposition and approximation theory. It processes the signal by global observations under the rate far below the Nyquist rate rather than local sampling. And then it recovers the original signal from observation values by appropriate reconstruction algorithm. Channel estimation based on CS can greatly improve the reliability of channel estimation and reduce naumber of he pilots.This paper makes the analysis and research for information transmission, channel estimation and physical layer security in TWRC. The main contents are listed as follows:First, an asymmetric modulation scheme based on physical layer network coding was proposed to realize the entire asymmetric rate transmission in TWRC. Then a scheme named subset coding was proposed, which combines channel coding and network coding with modulation to improve transmission validity and guarantees reliability.Second, channel estimation based on CS in TWRC was completed. Channel sparsity was analyzed and through appropriate design of the pilot, synthetic concatenated convolutional channels can be decomposed into two independent channel. The improved orthogonal matching pursuit algorithm adopted improves the spectrum utilization and the performance of channel estimation.Third, secret key was we extracted by exploiting channel reciprocity and commutative law of convolution operation. The scheme ensures the security of the physical layer communication. Then a scheme for security communication by exploiting the randomness of pilots was proposed to present eavesdropping of the third party.