Rotated Constellations To Improve BICM Performance For Next Generation Broadcast-wireless

The Next Generation Broadcast-Wireless(NGB-W) network aims to carry various services of tri-network convergence,and provides users with finer services such as broadcasting,data pushing, bidirectional interaction and accessing which sublimates on the basis of broadcast and cellular communication network.This system not only ensures efficiency in power and spectrum,but also improves communication robustness which introduces new key technologies such as LDPC and BCH joint coding,constellation rotation,interleaving and MIMO.With NGB-W in the background,this paper mainly has the following parts:Firstly, there are some passages to introduce the background knowledge including the network architecture and various key technologies such as MIMO technology, OFDM modulation and synchronization, coding and modulation techniques.Secondly,the two kinds of NGB-W channel model are described.The introduction of wireless channel characteristics is followed by channel simulation modeling which is desired by this paper, including traditional Rayleigh fading channel and deep fading channel.Thirdly, the paper studies BICM technology in the NGB-W system. Aiming at the constellation rotation technology of improving BICM, this chapter describes in detail the principles and implementation process.Then it simulates under different scenarios,and concludes:the gain of constellation rotation is directly proportional to LDPC code rate and channel fading,and inversely proportional to modulation order.Finally, the effect about de-mapping by the constellation rotation technique is studied. Under normal circumstances, the de-mapping method is one-dimensional LLR de-mapping, but the introduction of the constellation rotation technique changes orthogonality in two components of signal, thus the two-dimensional LLR de-mapping must be introduced.Then this chapter simulates under different scenarios,and concludes: the gain of the two-dimensional LLR iterative de-mapping is directly proportional to the number of iterations and the channel fading, inversely proportional to the LDPC code rate, and it may have no significant relationship with the modulation order.