Novel Low-Density Signature for Synchronous CDMA Systems Over AWGN Channel

Novel low-density signature (LDS) structure is proposed for transmission and detection of symbol-synchronous communication over memoryless Gaussian channel. Given N as the processing gain, under this new arrangement, users' symbols are spread over N chips but virtually only d v < N chips tha...

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Veröffentlicht in:IEEE transactions on signal processing Jg. 56; H. 4; S. 1616 - 1626
Hauptverfasser: Hoshyar, R., Wathan, F.P., Tafazolli, R.
Format: Journal Article
Sprache:Englisch
Veröffentlicht: New York, NY IEEE 01.04.2008
Institute of Electrical and Electronics Engineers
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Schlagworte:
Applied sciences
AWGN channels
Beta
Channels
Chip-level iterative SISO MUD
Chips
Code Division Multiple Access
Code division multiplexing
Coding, codes
Detection, estimation, filtering, equalization, prediction
Exact sciences and technology
Forward error correction
Gaussian channel
Gaussian channels
Information, signal and communications theory
Intersymbol interference
Iterative algorithms
low-density signature
Message passing
message passing algorithm
Multiaccess communication
Multiple access interference
Multiuser detection
Optimization
overloaded condition
Signal and communications theory
Signal, noise
Signatures
Spread spectrum
Spreads
Symbols
Telecommunications and information theory
Multiuser detection
Performance evaluation
Multiple access
overloaded condition
Gaussian channel
Wireless telecommunication
Iterative method
message passing algorithm
Decoding
Optimal detection
Algorithm
AWGN channels
Memoryless channel
Message passing
Simulation
Overload
Synchronous transmission
Code division multiple access
Chip-level iterative SISO MUD
Robustness
low-density signature
Signal detection
ISSN:1053-587X, 1941-0476
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Zusammenfassung:Novel low-density signature (LDS) structure is proposed for transmission and detection of symbol-synchronous communication over memoryless Gaussian channel. Given N as the processing gain, under this new arrangement, users' symbols are spread over N chips but virtually only d v < N chips that contain nonzero-values. The spread symbol is then so uniquely interleaved as the sampled, at chip rate, received signal contains the contribution from only d c < K number of users, where K denotes the total number of users in the system. Furthermore, a near-optimum chip-level iterative soft-in-soft-out (SISO) multiuser decoding (MUD), which is based on message passing algorithm (MPA) technique, is proposed to approximate optimum detection by efficiently exploiting the LDS structure. Given beta = K/N as the system loading, our simulation suggested that the proposed system alongside the proposed detection technique, in AWGN channel, can achieve an overall performance that is close to single-user performance, even when the system has 200% loading, i.e., when beta = 2. Its robustness against near-far effect and its performance behavior that is very similar to optimum detection are demonstrated in this paper. In addition, the complexity required for detection is now exponential to dc instead of K as in conventional code division multiple access (CDMA) structure employing optimum multiuser detector.
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ISSN:1053-587X
1941-0476
DOI:10.1109/TSP.2007.909320