Maximum-likelihood decoding and code combining for DS/SSMA slotted ALOHA

Author

Bigloo, Amir M Y ; Gulliver, T. Aaron ; Bhargava, Vijay K.

Author_Institution

Dept. of Syst. & Comput. Eng., Carleton Univ., Ottawa, Ont., Canada

Volume

45

Issue

12

fYear

1997

fDate

12/1/1997 12:00:00 AM

Firstpage

1602

Lastpage

1612

Abstract

This paper considers the combination of multiple copies of a packet to improve the performance of a slotted direct-sequence spread-spectrum multiple-access (DS/SSMA) ALOHA packet radio system with coherent binary phase-shift keying (BPSK) modulation. Both slotted DS/SSMA ALOHA with and without forward error correction (FEC) are considered. For the case with FEC, maximum-likelihood decoding with code combining is used. Code combining allows for the combination of multiple copies of the same packet (which are typically discarded), to obtain a lower code rate for that specific packet, and therefore an improved probability of successful decoding. In both cases, combining multiple copies of the same packet results in a throughput which is an increasing function over a broad range of offered load, so that the system is more reliable from the point of view of stability. In addition, combining provides a higher throughput and a smaller time delay for packet transmission. This is illustrated by means of analytical and simulation results

Keywords

access protocols; delays; forward error correction; maximum likelihood decoding; multi-access systems; packet radio networks; phase shift keying; probability; pseudonoise codes; spread spectrum communication; stability; telecommunication channels; BPSK modulation; DS/SSMA channels; DS/SSMA slotted ALOHA; FEC; analytical results; code combining; code rate; coherent binary phase-shift keying; direct-sequence spread-spectrum multiple-access; forward error correction; maximum-likelihood decoding; multiaccess interference; multiple packet copies; packet radio system; packet transmission; performance; simulation results; stability; successful decoding probability; throughput; time delay; Binary phase shift keying; Delay effects; Forward error correction; Maximum likelihood decoding; Packet radio networks; Phase modulation; Phase shift keying; Spread spectrum communication; Stability; Throughput;

fLanguage

English

Journal_Title

Communications, IEEE Transactions on

Publisher

ieee

ISSN

0090-6778

Type

jour

DOI

10.1109/26.650239

Filename

650239