Ping-Hung Chiang

Performance analysis of two-branch transmit diversity block-coded OFDM systems in time-varying multipath Rayleigh-fading channels

Based on Alamouti code, Lee and Williams proposed two-branch transmit diversity block-coded orthogonal frequency-division multiplexing (TDBC-OFDM) systems, namely, space-time block-coded OFDM (STBC-OFDM) and space-frequency block-coded OFDM (SFBC-OFDM). However, they employed the simple maximum-likelihood (SML) detector, which was designed under the assumption that the channel is static over the duration of a space-time/frequency codeword. Therefore, STBC-OFDM/SFBC-OFDM suffers from the high time/frequency selectivity of the wireless mobile fading channel. In this paper, besides the original SML detector, three detectors proposed by Vielmon et al. are applied to improve the two-branch TDBC-OFDM systems. Additionally, assuming sufficient cyclic prefix, the performances of all systems in spatially uncorrelated time-varying multipath Rayleigh-fading channels are evaluated by theoretical derivation and computer simulation, as well. According to the derived bit-error rate (BER), we further derive the bit-error outage (BEO) to provide a more object judgment on the transmission quality within a fading environment. Numerical results have revealed that significant performance improvement can be achieved even when the systems are operated in highly selective channels.

Performance of 2IMO differentially transmitdiversity block coded OFDM systems in doubly selective channels

By applying the differential space-time block coding in wireless multicarrier transmission, Diggavi et al. proposed the two-input-multiple-output (2IMO) differentially space-time-time block coded OFDM (TT-OFDM) system. In this paper, we recommend three novel differentially transmit-diversity block coded OFDM (DTDBC-OFDM) systems, namely, the FT-, FF-, and TF-OFDM systems. For instance, the TF-OFDM stands for the differentially space-time-frequency block coded OFDM. Moreover, the noncoherent maximum-likelihood sequence detector (NSD), and its three special cases, namely, the noncoherent one-shot detector, linearly predictive decision-feedback (DF) detector, and linearly predictive Viterbi receiver are incorporated to the 2IMO DTDBC-OFDM systems

Joint Estimation of Carrier-Frequency and Sampling-Frequency Offsets for SC-FDE Systems on Multipath Fading Channels

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.

Performance Analysis of Two-Branch Space-Time Block-Coded DS-CDMA Systems in Time-Varying Multipath Rayleigh Fading Channels

Based on Alamouti code, two-branch transmit diversity DS-CDMA systems, namely, space-time block coded DS-CDMA (STBC-DS-CDMA) systems are discussed. Besides the simple maximum-likelihood (SML) detector, three novel detectors are applied to improve the STBC-DS-CDMA systems. Additionally, for random binary spreading code (RBSC), the performance of all systems in spatially uncorrelated time-varying multipath Rayleigh fading channels are derived theoretically. In consequence of the simple expression for the variances of the multipath interference (MPI) and the multiuser interference (MUI), our analytical results are easy to calculate. Numerical outcomes have revealed that significant performance improvement can be achieved even when the systems are operated in highly selective channels.

Performance of noncoherent maximum-likelihood sequence detection for differential OFDM systems with diversity reception

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.

Pilot-Aided Fine Synchronization for SC-FDE Systems on Multipath Fading Channels

With single-carrier frequency-domain equalization (SC-FDE), the carrier-frequency offset (CFO) and sampling-frequency 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.

Performance Analysis of Alamouti 2IMO Diversity System in Time-Varying Rayleigh Fading Channels

It is well-known that space-time block coded transmit diversity system suffers from a diversity penalty in the time-varying channel. Lately, based on the Alamouti two-input single-output (2ISO) antenna diversity system, Vielmon et al. investigated the impact of a time-varying channel on the bit-error-rate (BER) performance and also recommended three detectors to increase the system robustness for rapid channel variation. In this paper, we generalize these detectors and their BER expressions to the two-input multiple-output (2IMO) antenna configuration. Moreover, the bit-error-outages (BEOs) are also derived to provide a more objective judgment on the transmission quality within a fading environment. These generalized results can be easily extended to the orthogonal frequency-division multiplexing (OFDM) and code-division multiple-access (CDMA) systems with the 2IMO antenna configuration.

SINR for DS-CDMA with random spreading

For wireless multipath fading channels, the performance of a direct-sequence code-division multiple-access (DS-CDMA) system is degraded by interference, including multipath interference (MPI) and multiuser interference (MUI). For the downlink DS-CDMA with random spreading, we derive the variances of MPI and MUI and obtain the signal-to-interference-plus-noise ratio (SINR). The simple and elegant expressions for the variances of the interference provide useful insights, while the corresponding SINR representation is helpful in evaluating the bit-error-rate (BER) performance that takes the impact of the interference into consideration. In order to demonstrate our approach, an example regarding the performance analysis of the two-input-single-output (2ISO) space-time block coded DS-CDMA with RAKE reception is also provided.

Performance analysis of two-branch space-time block coded DS-CDMA systems in time-varying multipath Rayleigh fading channels

Based on Alamouti code, two-branch transmit diversity DS-CDMA systems, namely, space-time block coded DS-CDMA (STBC-DS-CDMA) systems are discussed. Besides the simple maximum-likelihood (SML) detector, three novel detectors are applied to improve the STBC-DS-CDMA systems. Additionally, for random binary spreading code (RBSC), the performance of all systems in spatially uncorrelated time-varying multipath Rayleigh fading channels are derived theoretically. In consequence of the simple expression for the variances of the multipath interference (MPI) and the multiuser interference (MUI), our analytical results are easy to calculate. Numerical outcomes have revealed that significant performance improvement can be achieved even when the systems are operated in highly selective channels.

Performance analysis of two-branch transmit diversity block coded OFDM systems in timevarying multipath rayleigh fading channels

Based on Alamouti code, Lee et al. proposed two-branch transmit diversity OFDM systems, namely, space-time block coded OFDM (STBC-OFDM) and space-frequency block coded OFDM (SFBC-OFDM). However, they employed the simple maximum-likelihood (SML) detector, which was designed under the assumption that the channel is static over the duration of a space-time/frequency codeword. Therefore, STB-COFDM/SFBC-OFDM suffers from the high time/frequency-selectivity of the wireless mobile fading channel. In our work, in addition to the original SML detector, three novel detectors, proposed by Vielmon et al., are applied to improve the two-branch TDBC-OFDM systems. Additionally, assuming sufficient cyclic prefix (CP), the performances of all systems in spatially uncorrelated time-varying multipath Rayleigh fading channels are evaluated by theoretical derivation and computer simulation, as well. Numerical results have revealed that significant performance improvement can be achieved even when the systems are operated in highly selective channels.