Study On Hierarchical Modulation Based On Network Coding

In the two-way relay wireless network, because the distance of the two sources tothe relay is not consistent, it leds to the asymmetry between the channel. If the poorsource node uses low order modulation, then the good channel of the other one will bewasted. However if the good one uses high order modulation, the bad channel of thepoor source node will degrade, eventually it led to a decline in performance of thesystem.Network coding technology subverts the traditional concept-intermediate nodeonly stores and forwards from the received information. The basic idea of Networkcoding technology is that the intermediate node multiples the data streams fornonlinear or linear transformation, then forwarding to the destination node, thedestination node restores the initial information through the operation on the basis ofthe known information, in order to improve the network throughput. Hierarchicalmodulation technology distributions different protection to different information, soas to make the important information has better performance on the receivingterminal.This article is based on wireless two-way relay channel（TWRC）transmissionscenario, the network coding and hierarchical modulation technology conductedin-depth research, the research content of this article is as follows:1、 Because in actual two-way relay channel transmission, the quality of thedifferent channels are generally asymmetric, The traditional adding zero scheme canbe used to make the information symmetry, generally we can base on the traditionaladding zero scheme. So we put forward the hierarchical adding zero scheme,effectively reduce the redundancy of the system. Through the theoretical analysis andthe simulation results we can see that the BER performance of the system has beenimproved.2、 Aimed to the wireless two-way relay system, we proposed joint networkcoding and hierarchical modulation scheme based on adaptive threshold control, inthe process of transmission, the relay employs adaptive joint network coding andhierarchical modulation based on the channel conditions, making the systemimproved. In different channel conditions, we can choose the adaptive network codingscheme.