No abstract

With single-carrier frequency-domain equalization, the carrier-frequency and sampling-frequency offsets are embedded in the phases of complex frequency-domain signal components. This paper proposes a sub-block processing to extract the phases and applies the least-squares regression to jointly estimate the offsets. The effectiveness of the proposed SC-FDE receiver is demonstrated on multipath fading channels.

For the single-carrier M-ary differential phase-shift keying (MDPSK), the multiple-symbol differential detector, or the noncoherent maximum-likelihood sequence detector (NSD), and its three special cases, namely, the noncoherent one-shot detector, the linearly predictive decision-feedback (DF) detector, and the linearly predictive Viterbi receiver are reviewed based on a hierarchical interpretation. For the multicarrier transmission, the differential orthogonal frequency division multiplexing (OFDM) systems with diversity reception are discussed. It is well known that there are two types of differential OFDM systems, namely, the time domain differential OFDM (TD-OFDM) and the frequency domain differential OFDM (FD-OFDM). In this paper, the NSD and its special cases are incorporated to the differential OFDM systems. Furthermore, we provide a simple closed-form bit-error-rate (BER) expression for the differential OFDM systems utilizing the noncoherent one-shot detector with diversity reception in the time-varying multipath Rayleigh fading channels. Numerical results have revealed that, with multi-antenna diversity reception, the performance of the noncoherent one-shot detector is improved significantly. However, when only one or two receive antennas are available, the implementation of the linearly predictive DF detector or the linearly predictive Viterbi receiver is necessary for achieving better and satisfactory performance.

For the two-branch space-time (ST) block-coded directsequence code-division multiple-access (DS-CDMA) systems, the impacts of a time-varying multipath channel on the downlink transmission are analyzed. By considering the systems using the random binary spreading code (RBSC) and deterministic binary spreading code (DBSC), the effects of the multipath interference and multiuser interference are included in the analyses of the bit-error rate and bit-error outage. Also, for the performance analysis of the system employing the decision-feedback (DF) detector, the effect of error propagation is taken into account. It is known that enlarging the spreading factor can enhance the interference-rejection ability of a DS-CDMA system and, hence, can improve the performance. However, it also lengthens the symbol duration and, thus, stiffens the diversity penalty resulting from the channel variation within an ST-code-word duration. Thus, a moderate spreading factor should be chosen. In this paper, for the RBSC system using the simple-maximum-likelihood (SML) detector, we derive an optimum spreading factor that is optimum in the minimum-error-probability sense. Numerical results have revealed that the derived optimum spreading factor is a good estimate of the ones for the DBSC systems using the SML, zero-forcing, and DF detectors. Therefore, it is very useful for system designers in determining the system parameters.

With single-carrier frequency-domain equalization (SC-FDE), the carrier-frequency offset (CFO) and samplingfrequency offset (SFO) are embedded in the phase rotations of the complex frequency-domain signal components at the output of the fast Fourier transform (FFT). To extract the phase rotations and estimate the CFO and SFO, the frequency-domain signal components need to be known. However, they are, in general, not known to the receiver, since they are a mixture of the data and pilot symbols. To solve this difficulty sub-block processing is proposed, such that joint estimation of the CFO and SFO can be applied. For the joint estimation, both the linear least-squares (LLS) and simple weighted least-squares (SWLS) regressions are considered, where the latter is shown to be robust to the channel frequency-selectivity. Finally, the SC-FDE receiver with proposed closed-loop tracking algorithm is tested on both quasi-static and time-varying multipath fading channels and its effectiveness is demonstrated.