On iterative decoding of two-level superposition codes for cooperative broadcasting based on QPSK and 4-PAM constellations

Abstract

Abstract-This paper considers iterative decoding of twolevel superposition codes used in cooperative broadcasting over wireless networks. The coding scheme consists of two low-density parity-check (LDPC) codes combined using Plotkin's |u|u + v|-construction and provides two levels of error protection. Coding for cooperative broadcasting differs from conventional singlesource broadcast coding. Instead of binary addition of subcode codewords performed by a single-source encoder, in superposition coding two modulated subcode sequences, produced by two coordinated and independent sources, are combined at the antenna of the receiver. Expressions are derived for the bit metrics, or log-likelihood ratio values, used by an iterative decoder for twolevel superposition coding schemes based on BPSK, QPSK and 4-PAM modulated sequences. It is shown that conventional equalenergy 4-PAM constellations do not work well with two-level superposition coding. A solution is proposed in which 4-PAM constellations of different levels of average energy are used.

Two-level channel coding for cooperative wireless networks based on WiMAX LDPC codes

“…The error performance of superposition coding using Plotkin's construction with short length LDPC codes based on BPSK and QPSK constellations was presented in a previous paper [25]. Figs.…”

“…A previous paper [25] proposed the use of two Gray-mapped 4-PAM constellations of differing energies, in order remove error floors resulting from the use of equal-energy 4-PAM constellations. We propose to use one 4-PAM constellation with four times larger energy.…”

Jointly optimized multiple Reed-Muller codes for wireless half-duplex coded-cooperative network with joint decoding

“…Based on this fact, we also propose an efficient algorithm to design a good code at the relay. In [28,29], Plotkin's construction is used in conjunction with the superposition coding for cooperative broadcasting in wireless networks. In superposition coding [30], two modulated subcode sequences, produced by the two coordinated and independent sources, are combined at the antenna of the receiver (also referred as over the air mixing [31]).…”

“…That scheme also showed promising BER performance gains; however, the scheme proposed in this paper is entirely different from the former in many ways. Firstly, we use Plotkin's construction to construct a new code at the destination, and binary addition of unmodulated codewords takes place at the relay instead of real number addition as suggested in [28,29]. Secondly, there is only one source in our scheme, and there is no over the air mixing, whereas in [28,29], two independent source nodes broadcast their information to the destination node and over the air mixing is performed.…”

Polar code‐based overlapping transmission scheme for Internet of Vehicles

“…In this case, the received signals are overlapped (nonorthogonal). In order to recover the information from overlapped signals, many related works based on different encoding and decoding algorithms were proposed [2][3][4]. Zhu et al [4] proposed an overlapping scheme for sensor networks in which the overlapped signals are from different sensor nodes.…”