Research On Unequal Error Protection Mechanism For Near Shannon Limit Codes

In the modern society, with the rapid development of communications technologies, various data can be transmitted to all over the world through digital communication systems conveniently and fast. In order to improve the quality of transmitted multimedia which is mainly image and video, people begin to pay more attention to unequal error protection(UEP) technology. Unequal error protection gives more protection to the more important part according to the influence of different parts of the bit stream on the quality of reconstruction. Although it degrades the performance of less important part, it improves the overall performance of the receiver and the robustness of data transmission in the severe channel environment.This paper mainly focuses on unequal error protection mechanism of near Shannon limit codes. These codes include LDPC codes, Raptor codes, Polar codes, etc. Low Density Parity Check(LDPC) codes have unique advantages in realizing UEP by designing the parity check matrix, which makes them become one of the hotspots in the UEP research. Raptor codes can realize UEP by optimizing the degree distribution of LT codes and increasing the probability of involving more important data in encoding. It can also realize UEP through the source-channel joint coding with other codes. Polar codes are another near Shannon limit codes proposed in recent years. Right now, the research on UEP based on Polar codes is ongoing. Based on the existing research, this paper designs two new unequal error protection schemes. The main contributions of this paper are as follows:1) The unequal error protection scheme based on Polar codes is proposed by making use of the channel polarization phenomenon. In order to improve the decoding performance, we concatenate Polar codes with LDPC codes. Simulation results show that the proposed scheme gives the expected performance for unequal error protection.2) Based on the BP decoding algorithm of LDPC codes, a new UPF decoding algorithm with UEP characteristics is proposed. Simulation results show that the new algorithm has better decoding performance compared with the existing unequal error protection decoding scheme for LDPC codes.