A new channel interleaving method, called chip interleaving, for direct sequence code division multiple access (DS-CDMA) mobile radio is proposed. Chip interleaver scrambles the chips and transforms the transmission channel into a highly time-selective or highly memoryless channel. It was found that the turbo decoding performance which degrades in a fading channel is significantly improved with...

Powerand bandwidth-efficient differentially encoded transmission over slowly time-varying fading channels with noncoherent reception and without channel state information is considered. For high bandwidth efficiencies, combined phase and amplitude modulation is used. For increased power efficiency, channel coding and multiple-symbol differential detection are applied, i.e., interleaving and det...

Coherent frequency-domain equalisation (FDE) of DS-CDMA signals suffers from channel estimation error. Frequency-domain differential detection and equalisation (FDDDE) for the reception of differentially encoded DS-CDMA signals transmitted over a frequency-selective fading channel is proposed. At a transmitter, the differentially encoded data symbol is spread and transmitted. At a receiver, dif...

This paper presents a new fractionally-spaced maximum a posteriori (MAP) equalizer for data transmission over frequency-selective fading channels. The technique is applicable to any standard modulation technique. The MAP equalizer uses an expanded hypothesis trellis for the purpose of joint channel estimation and equalization. The fading channel is estimated by coupling minimum mean square erro...

This thesis deals with multiuser multicarrier communications over unknown time and frequency selective fading channels. Since there is a growing demand for capacity, especially in mobile communications, wireless multiuser communications experiences increasing interest in recent year. The wireless channel in general is a time and frequency selective fading channel. In that case, orthogonal frequ...

The ergodic capacity, capacity distribution and outage capacity are investigated for MIMO wireless systems under time-varying and frequency-selective Rayleigh fading channels. Our theoretical results and Monte-Carlo simulations show that: (1) if the frequency-selective Rayleigh fading channel impulse response has no inter-tap correlations, then its ergodic capacity is the same as that of the fr...

Abstract— Low-density parity-check (LDPC) codes are analyzed using density evolution techniques for a frequency-nonselective, time-selective fading channel where the fading affects both the amplitude and the phase of the transmitted signal. To aid the channel estimation process, pilot symbols are transmitted periodically. The performance of several message-passing estimation/decoding algorithms...

In this paper, the transmission of an orthogonal frequency division multiplexed (OFDM) signal over channel with time varying frequency has been considered, selective fading and additive white Gaussian noise (AWGN). Due to channel dispersion, intersymbol and intercarrier Interference will occur at the receiver. To reduce this interference, a guard time is added as a cyclic prefix (CP), or traili...

The problem of training symbol placement for the estimation of block-fading channel is first considered. The channel is frequency selective with correlated random taps. The Cramér-Rao Bound (CRB) on the mean square error (MSE) of channel estimators is derived and minimized with respect to the pilot symbols and their placement. It is shown that, among all orthogonal pilot sequence placements, th...

In this paper, we propose a joint channel estimation and decoding scheme using soft bit output information in OFDM-based systems. In order to estimate the complex OFDM channel amplitudes, the estimation algorithms usually rely on the Pilot Signal Assisted Modulation (PSAM). We enhanced this method by using the soft code bits after each turbo decoding iteration in a feedback loop. This way, the ...