A Communication System Based on Walsh-Hadamard Codes and Constellations for Fading Environments

• Published in: IEEE transactions on vehicular technology Vol. 57; no. 3; pp. 1596 - 1605
• Main Authors: Magana, M.E., Moranvil, W., Huaping Liu
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.05.2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; AWGN; Bit error rate; Circuit properties; Coding, codes; Digital communication; Diversity reception; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Equipments and installations; Exact sciences and technology; Fading; Information, signal and communications theory; Lattices; Mobile radiocommunication systems; Modulation coding; Nonuniform pulse-amplitude modulation (PAM); nonuniform quadrature-amplitude modulation (QAM); peer-topeer; Pulse modulation; Quadrature amplitude modulation; Radiocommunications; Rayleigh channels; Rayleigh fading; Signal and communications theory; Signal convertors; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Walsh codes; Peer-to-peer; Walsh codes; Nonuniform PAM; Rayleigh fading; Nonuniform QAM; Performance evaluation; Quadrature amplitude modulation; Bit error rate; Wireless telecommunication; peer-to- peer; Gaussian distribution; nonuniform quadrature-amplitude modulation (QAM); Selective fading; M ary modulation; Gaussian noise; Computer network; White noise; Digital communication; Pulse amplitude modulation; Robustness; Hadamard codes; Fading channels; Mobile radiocommunication; Modulator; Binary signal; Rayleigh channels; Distributed source signal; Resource sharing; Signalling; Nonuniform pulse-amplitude modulation (PAM); Telecommunication system
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2007.907078

In this paper, we investigate a new digital communication system based on Walsh-Hadamard codes. The modulator maps a uniformly distributed binary source to a set of symbols with a Gaussian-like distribution. These symbols are then mapped to a 2-D constellation in such a way that performance is improved when transmission occurs over Rayleigh fading channels. We assess the performance of these modulation schemes when the channel is of the nonfrequency-selective Rayleigh fading plus white Gaussian noise type and compare the results to conventional quadrature-amplitude modulation (QAM) schemes with comparable spectral efficiencies. The proposed system provides excellent robustness to fading without the use of common diversity schemes employed in M-ary signaling systems to improve bit-error-rate (BER) performance in such environments.