DocumentCode :
1251563
Title :
The coding-spreading tradeoff in CDMA systems
Author :
Veeravalli, Venugopal V. ; Mantravadi, Ashok
Author_Institution :
Dept. of Electr. & Comput. Eng., Illinois Univ., Urbana, IL, USA
Volume :
20
Issue :
2
fYear :
2002
fDate :
2/1/2002 12:00:00 AM
Firstpage :
396
Lastpage :
408
Abstract :
General definitions of spreading and coding are given based on the notion of Shannon bandwidth introduced by Massey (1994), with the goal of distinguishing these operations for signaling with bandwidth redundancy. These definitions are shown to lead to a separation result: every bandwidth redundancy scheme can be expressed as a concatenation of coding followed by spreading. The coding-spreading tradeoff problem is then studied for a code division multiple access (CDMA) system in which the receiver processes the received signal by using a user-separating front-end, which feeds into autonomous single-user decoders. Under the single-user decoding setting, it is established that the linear minimum mean square error (LMMSE) front-end multiuser detector is optimum among all front-ends that are constrained to use only spreading information. Also, conditions are given for the single-user decoders to ignore spreading information without losing optimality. An example illustrating the coding-spreading tradeoff optimization for a direct sequence CDMA system with random spreading is given. Single-cell and multicell scenarios are considered in the optimization, and a comparison is made of the spectral efficiencies that can be achieved with the conventional matched filter and LMMSE front-ends
Keywords :
cellular radio; code division multiple access; decoding; encoding; least mean squares methods; multiuser channels; signal detection; spread spectrum communication; LMMSE front-end multiuser detector; Shannon bandwidth; bandwidth redundancy; cellular radio; coding-spreading tradeoff; direct sequence CDMA system; division multiple access; linear minimum mean square error; matched filter; random spreading; receiver; single-user decoders; spectral efficiency; user-separating front-end; Bandwidth; Baseband; Decoding; Feeds; Matched filters; Mean square error methods; Multiaccess communication; Redundancy; Signal processing; Spread spectrum communication;
fLanguage :
English
Journal_Title :
Selected Areas in Communications, IEEE Journal on
Publisher :
ieee
ISSN :
0733-8716
Type :
jour
DOI :
10.1109/49.983362
Filename :
983362
Link To Document :
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