Asymmetric Physical Layer Network Coding For Wireless Two-Way Relay Communication

Physical layer network coding has been considered as a key technique to enhance the spectral efficiency of two-way relay channels. While traditional network coding does not work well in the asymmetric scenes which naturally exist, we need to design asymmetric physical network coding for these scenes. Moreover, since MIMO technology and channel coding are important technologies for wireless communication, asymmetric physical network coding for MIMO system and channel coded system should be considered.In 3-node wireless two-way relay communications, two terminals exchange information with the help of one relay. The relay needs to receive data from the two terminals, combine the two data streams by network coding and broadcast the network coded signals to the two terminals. Form the received signals from the relay, the two terminals get the information they need, separately. Theoretically, the relay can transmit data to the two receivers simultaneously at rates equal to the individual link capacities. Therefore, our goal of designing asymmetric physical layer network coding is to make the performance of transmission from relay to the two terminals to be the same as traditional point to point transmission.We prove the traditional zero padding XOR scheme is not optimal and propose a more flexible and better scheme. Next, we specially design STBC and its bit-to-code mapping for asymmetric two-way relay transmission. At last, we discuss asymmetric physical layer network coding in channel coded system. For PSK modulation, we propose a scheme which can combine two data streams using different channel coding. The proposed schemes improve the system performance, and they are easy to be implemented.