Abstract
Super-orthogonal block codes in space-time domain (i.e., Super-orthogonal space-time trellis codes (SOSTTCs)) were initially designed for frequency nonselective (FNS) channels but in frequency selective (FS) channels these super-orthogonal block codes suffer performance degradation due to signal interference. To combat the effects of signal interference caused by the frequency selectivity of the fading channel, the authors employ two methods in this paper, namely, multichannel equalization (ME) and orthogonal frequency division multiplexing (OFDM). In spite of the increase complexity of the SOSTTC-ME optimum receiver design scheme, the SOSTTC-ME scheme maintains the same diversity advantage as compared to the SOSTTC scheme in FNS channel. In OFDM environments, the authors consider two forms of the super-orthogonal block codes, namely, super-orthogonal space-time trellis-coded OFDM and super-orthogonal space-frequency trellis-coded OFDM. The simulation results reveal that super-orthogonal space-frequency trellis-coded OFDM outperforms super-orthogonal space-time trellis-coded OFDM under various channel delay spreads.
Highlights
The use of channel codes in combination with multiple transmit antennas achieves diversity, but the drawback is loss in bandwidth efficiency
The super-orthogonal block coding schemes with orthogonal frequency division multiplexing (OFDM) (i.e., super-orthogonal space-time trellis codes (SOSTTCs)-OFDM and SOSFTC-OFDM) are assumed to have a bandwidth of 1 MHz and 128 OFDM subcarriers, and with multichannel equalisation, the system is assumed to have 512 bits per frame (QPSK modulation assumed for all simulations)
The receiver structure of an SOSTTC in an frequency selective (FS) channel is given so that multichannel equalisation is used to mitigate the effects of multipath interference
Summary
The use of channel codes in combination with multiple transmit antennas achieves diversity, but the drawback is loss in bandwidth efficiency. The performance of super-orthogonal block code in space-time domain is based on two fundamental assumptions with regard to the fading channel, which are given as follows:. OFDM can be used to mitigate the effects of intersymbol interference for space-time codes in multipath fading channels [11, 12]. (iii) The performance comparison of using both ME and OFDM to mitigate the effects of signal interference for super-orthogonal block code in a multipath environment was presented.
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