Multiple Ldpc Coding And Modulation Are Jointly Optimized Design Studies

With the mobile communications towards to the development of high-speed broadband, Frequency resources become increasingly valuable at the request of transmission speed.Future communication system must make full use of limited spectrum resources,so the effectiveness of power and bandwidth is becoming increasingly prominent.The combination of code and modulation can overcome this contradiction.In recent years,With the new error correction coding, MIMO space-time modulation, as well as the emergence of iterative decoding methods, the joint coding and modulation design is becoming a hot spot of common concern.LDPC code is a channel coding scheme which approaches the Shannon limit, and it has been used in DVB-T, WiMax, UWB and LTE wireless communication system, etc. The performance of q -ary LDPC code is better than that of the binary LDPC code, so the study of q -ary LDPC code encoding and decoding and the research of joint design of q -ary LDPC code and high-level modulation are very meaningful work.In addition to coding and modulation technologies,diversity is also a technology for achieving gain.Different from time diversity,frequency diversity and spatial diversity which have been extensively studied,Signal space diversity (signal space diversity, SSD) is a power and bandwidth efficient diversity technique that does't need additional resources.SSD improve the system performance by increasing the computational complexity of the receiver.This is the main factor that hindering its wider use.Although, SSD has been widely used in a number of coded modulation schemes, such as BICM and BICM-ID, SSD will be used in the q -ary coded modulation system based of the inherent requirement of mapping high-dimensional space of SSD.The main work and conclusions of this paper are as follows:We make a detailed analysis and summary for decoding algorithm of q -ary LDPC code, taking into account the requirements of the hardware implementation, we improve thedecoding algorithm which of low-complexity, and the improvement brought about a certain amount of compensation for the performance. Starting with the simplest combination of q -ary LDPC code and high-level modulation, we proposed a new q -ary LDPC code based on belief propagation joint code modulation (QBPCM-ID) scheme.Through the simulation, we analyse the impact on system performance from the number of iterations and the interleaver.Next, we introduce the SSD to the QBPCM-ID scheme. Through the result of the simulation, the system performance turns better.Application of the idea of concatenated coding, we proposed a coded SSD.That is, to maintain the same code rate and transfer part of the code rate of the q -ary LDPC code to the SSD side. We can observe that the new scheme is better than the old one according to the result of simulation under different total code rate.