DocumentCode :
345673
Title :
Soft-decoder feedback aided space-time processing in multiuser interference suppression
Author :
Thomas, Joseph ; Geraniotis, Evaggelos
Author_Institution :
Dept. of Electr. & Comput. Eng., Maryland Univ., College Park, MD, USA
fYear :
1999
fDate :
1999
Firstpage :
693
Abstract :
This work presents a soft iterative minimum mean square error (MMSE) multiuser interference suppressor for coded direct sequence code division multiple access (CDMA) uplink channels that employ space-time processing at both the mobile transmitters and the base station receiver. With a new equivalent discrete-time synchronous model for randomly spread asynchronous multiuser CDMA channels, we develop an iterative scheme that exchanges soft information between an MMSE multiuser demodulator (that also concurrently performs subtractive interference cancellation) and a bank of single-user decoders. It performs well both at low and high received signal powers, and displays the successive cancellation property across iterations, exhibiting good near-far resistance. Introducing multisensor arrays at the receiver relaxes the limitations imposed by the inherent suboptimality of MMSE multiuser demodulation, in so far as it enhances interuser separation, now in the spatial sense, and thereby allows significant overload capability. Further, this work explores new territory by studying multisensor transmission in multiuser channels. A new multisensor block modulation scheme called space-time spreading, for mobile transmitters is proposed; it is observed to provide significant benefits especially when the spatial separation afforded by the use of multisensor receiver arrays, is otherwise limited
Keywords :
Viterbi decoding; array signal processing; cellular radio; code division multiple access; demodulation; interference suppression; iterative methods; least mean squares methods; mobile radio; multiuser channels; signal detection; spread spectrum communication; DS-CDMA uplink channels; MMSE multiuser demodulator; base station receiver; direct sequence code division multiple access; equivalent discrete-time synchronous model; iterative scheme; mobile transmitters; multisensor arrays; multisensor block modulation scheme; multisensor receiver arrays; multiuser channels; multiuser interference suppression; near-far resistance; randomly spread asynchronous multiuser CDMA channels; single-user decoders; soft iterative minimum mean square error; soft-decoder feedback; space-time processing; space-time spreading; spatial separation; subtractive interference cancellation; successive cancellation property; Base stations; Demodulation; Direct-sequence code-division multiple access; Feedback; Interference cancellation; Interference suppression; Iterative decoding; Mean square error methods; Multiaccess communication; Transmitters;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Wireless Communications and Networking Conference, 1999. WCNC. 1999 IEEE
Conference_Location :
New Orleans, LA
ISSN :
1525-3511
Print_ISBN :
0-7803-5668-3
Type :
conf
DOI :
10.1109/WCNC.1999.796733
Filename :
796733
Link To Document :
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