In this paper, the performance of OFDM systems that utilize coding and spreading is presented. The proposed systems operate in outdoor environments and achieve coding gains through the use of Low-Density Parity-Check (LDPC) encoding. It is shown here that by introducing HadamardWalsh spreading in coded OFDM, additional gain in performance can be attained relative to uncoded as well as LDPC code...

WLAN plays an important role as a complement to the existing or planned cellular networks which can offer high speed voice, video and data service up to the customer end. The aim of this paper is to analysis the performance of coded WLAN system for BPSK under AWGN channel. The low-density parity-check (LDPC) coding is considered as the high-performance channel coding scheme due to its good trad...

In this paper, we consider joint network and LDPC coding for practically implementing the denosie-and-forward protocol over bi-directional relaying. the closed-form expressions for computing the log-likelihood ratios of the network-coded codewords have been derived for both real and complex multipleaccess channels. It is revealed that the equivalent channel observed at the relay is an asymmetri...

We report weaknesses in two algebraic constructions of low-density parity-check codes based on expander graphs. The Margulis construction gives a code with nearcodewords, which cause problems for the sum-product decoder; The RamanujanMargulis construction gives a code with low-weight codewords, which produce an error-floor.

Let h l (x)h2 (x) be the parity check polynomial of a binary cyclic code. This article presents a formula for decomposing words in the code as sums of multiples of words in the codes whose parity check polynomials are hl(x) and h 2 (x). This decomposition provides information about the weight distribution of the code. This work was supported by National Science Foundation Grants GK-37449 and GK...

We extend the framework for studying the stopping redundancy of a linear block code by introducing and analyzing the stopping redundancy hierarchy. The stopping redundancy hierarchy of a code represents a measure of the trade-off between performance and complexity of iteratively decoding a code used over the binary erasure channel. It is defined as an ordered list of positive integers in which ...

We analyze the effect of redundant parity-check equations on the error-floor performance of low-density paritycheck (LDPC) codes used over the additive white Gaussian noise (AWGN) channel. Our findings show that a large number of iterative decoding errors in the [2640, 1320] Margulis code, confined to point trapping sets in the standard Tanner graph, can be corrected if only one redundant parit...

An algorithm for generating parity-check matrices of high-rate lowdensity parity-check codes based on permutation matrices and Steiner system S(v, 4, 2) is proposed. The estimations of rate, minimum distance and girth for derived code constructions are presented. The results of simulation of obtained code constructions for an iterative ”belief propagation” (Sum-Product) decoding algorithm, appl...

In this paper the broadband wireless access system, provided by the IEEE 802.16 wireless MAN air interface with its amendment to mobile users (IEEE 802.16e), is being analyzed. We provide performance results for the most important forward error correcting (FEC) schemes intended for IEEE 802.16e – convolutional turbo codes (CTC) and Low Density Parity Check (LDPC) codes.

Using a new parity-check matrix, a class of convolutional codes with a designed free distance is introduced. This new class of codes has many characteristics of BCH block codes, therefore, we call these codes BCH convolutional codes.