Space-Time Trellis and Space-Time Block Coding Versus Adaptive Modulation and Coding Aided OFDM for Wideband Channels

Abstract

Abstract-The achievable performance of channel coded spacetime trellis (STT) codes and space-time block (STB) codes transmitted over wideband channels is studied in the context of schemes having an effective throughput of 2 bits/symbol (BPS) and 3 BPS. At high implementational complexities, the best performance was typically provided by Alamouti's unity-rate G 2 code in both the 2-BPS and 3-BPS scenarios. However, if a low complexity implementation is sought, the 3-BPS 8PSK space-time trellis code outperfoms the G 2 code. The G 2 space-time block code is also combined with symbol-by-symbol adaptive orthogonal frequency division multiplex (AOFDM) modems and turbo convolutional channel codecs for enhancing the system's performance. It was concluded that upon exploiting the diversity effect of the G 2 space-time block code, the channel-induced fading effects are mitigated, and therefore, the benefits of adaptive modulation erode. In other words, once the time-and frequency-domain fades of the wideband channel have been counteracted by the diversity-aided G 2 code, the benefits of adaptive modulation erode, and hence, it is sufficient to employ fixed-mode modems. Therefore, the low-complexity approach of mitigating the effects of fading can be viewed as employing a single-transmitter, single-receiver-based AOFDM modem. By contrast, it is sufficient to employ fixed-mode OFDM modems when the added complexity of a two-transmitter G 2 scheme is affordable.

Near-Instantaneously Adaptive HSDPA-Style OFDM Versus MC-CDMA Transceivers for WIFI, WIMAX, and Next-Generation Cellular Systems

“…The performance versus complexity tradeoffs of MC-CDMA systems benefiting from both STBCs and cyclic delay diversity (CDD) was investigated by Lodhi et al [120]. Different-throughput STBC and ST trellis coded AOFDM schemes combined with a variety of channel codes were studied by Liew and Hanzo [121] in terms of their performance versus complexity. For low-dispersion channels the STBC-aided AOFDM schemes performed better, while for high-dispersion channels the opposite was true.…”

“…For example, for a 6 Â 6-element adaptive MIMO OFDM system a total of 64 FDCHTFs has to be determined. Blind joint soft-detection aided slow frequencyhopped multicarrier DS-CDMA was the subject of [130], while space-time coded MIMO aided OFDM was the subject of [131] and [132].…”

Performance Analysis of MIMOOFDM System using Spacetime Turbo Codes and Adaptive Beamforming

“…[1] Among the existing air-interface techniques, orthogonal frequency division multiplexing (OFDM) [2]- [4] has shown a number of advantages and has attracted substantial interest. New wireless techniques, such as ultra wideband (UWB) [5],advanced source and channel encoding as well as various smart antenna techniques, for example space-time codes (STCs) [6], space division multiple access (SDMA) [1] and beamforming, as well as other multiple-input multiple output (MIMO) [7], [8] wireless architectures are capable of offering substantial gains attaining the maximum possible diversity gain is the objective of the family of space-time block coding (STBC) [11] as well as spacetime trellis coding (STTC) [12] schemes found in the literature [6]. The beneficial effects of second-order transmit and up to sixth-order receiver diversity was demonstrated in the context of STBC-aided MIMO-OFDM [13], [14], but space-time coding MIMO will not be considered further in this treatise.…”

Multiuser MIMO-OFDM for Next-Generation Wireless Systems

“…In Fig. 1 the beneficial effects of second-order transmit and up to sixth-order receiver diversity was demonstrated in the context of STBC-aided MIMO-OFDM [13], [14], but space-time coding MIMOs will not be considered further in this treatise. Finally, beamforming mitigates the effects of interfering users roaming in the vicinity of the desired user [15], provided that their received signals are angularly separable, as demonstrated in Fig.…”