Layered Steered Space-Time-Spreading-Aided Generalized MC DS-CDMA

• Published in: IEEE transactions on vehicular technology 2010-02, Vol.59 (2), p.999-1005
• Main Authors: El-Hajjar, M., Alamri, O., Maunder, R.G., Hanzo, L.
• Format: Article
• Language: English
• Subjects: Amalgamation; Applied sciences; Array signal processing; Beam-forming; beam-steering; Beamforming; Code division multiplexing; Coding, codes; Decoding; Detection, estimation, filtering, equalization, prediction; Direct-sequence code-division multiple access; Diversity methods; Exact sciences and technology; extrinsic information transfer (EXIT) charts; Gain; generalized multicarrier code-division multiple access (MC-CDMA); Information, signal and communications theory; INT; Interference; Iterative decoding; iterative detection; MIMO; Multiaccess communication; Multiplexing; near-capacity coding; Signal and communications theory; Signal, noise; Sociotechnical systems; space-time spreading; spatial multiplexing; Spreading; Subcarriers; System performance; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments)
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2009.2027734

We present a novel trifunctional multiple-input-multiple-output (MIMO) scheme that intrinsically amalgamates space-time spreading (STS) to achieve a diversity gain and a Vertical Bell Labs layered space-time (V-BLAST) scheme to attain a multiplexing gain in the context of generalized multicarrier direct-sequence code-division multiple access (MC DS-CDMA), as well as beamforming. Furthermore, the proposed system employs both time- and frequency-domain spreading to increase the number of users, which is also combined with a user-grouping technique to reduce the effects of multiuser interference. Further system performance improvements can be attained by serially concatenating our proposed scheme with an outer code that is amalgamated with a unity-rate code for the sake of improving the achievable decoding convergence behavior of the proposed system, which is evaluated with the aid of extrinsic information transfer charts. We also propose a novel logarithmic likelihood ratio (LLR) postprocessing technique to improve the iteratively detected system's performance. Explicitly, the proposed system can attain a second-order spatial diversity gain and a frequency diversity gain of order V, where V is the number of subcarriers. Additionally, the proposed system attains a beamforming gain and a multiplexing gain that is twice that of a single-input-single-output system. Furthermore, after I = 10 decoding iterations and employing an interleaver depth of D int = 160 000 bits, a time-domain spreading factor of N e = 4, and V = 4 subcarriers, the overloaded system supporting K = 8 users requires an E b /N 0 that is only about 0.45 dB higher than the single-user system.