Duration Of Channel Impulse Response Research Articles

A Fine-Grained Analysis of Time Reversal MU-MISO Systems Over Correlated Multipath Channels With Imperfect CSI

Time reversal (TR) is regarded as a potential future transmission scheme for multi-user (MU) multiple-input single-output (MISO) ultra-wideband (UWB) communication systems. In spite of TR’s good performance in MU-MISO UWB systems, it suffers from performance degradation due to spatial correlation and imperfect channel-state information. In this paper, a comprehensive performance analysis of MU-MISO UWB systems with a TR pre-filter is provided. Both spatial correlation and channel estimation errors (CEE) are taken into account in the propagation channel model, and the system performance is mainly studied in terms of its effective signal-to-interference-plus-noise ratio (SINR), channel capacity, and bit error rate. The novel closed-form expressions for the average effective SINR are derived in order to characterize the influence of propagation conditions such as channel impulse response duration, spatial correlation, and CEE on TR performance metrics. The expressions reveal more precisely to us that spatial correlation and CEE have different effects on the average power of the desired signal, inter-symbol interference, and inter-user interference. Moreover, the impacts of spatial correlation and CEE on the performance of MU-MISO TR system are thoroughly investigated. In particular, the capacity loss of MU-MISO TR system due to spatial correlation and CEE is quantified and fully discussed at the end of this paper. It is shown that high spatial correlation and CEE cause a remarkable reduction in bandwidth efficiency. Finally, all theoretical results are confirmed by numerical simulations.

Blind Beamforming Schemes in SC-FDMA Systems With Insufficient Cyclic Prefix and Carrier Frequency Offset

In cyclic prefix (CP)-based transmission systems, if the time duration of the cyclic extension is shorter than the channel impulse response duration, system performance is degraded due to the introduction of intersymbol interference (ISI) and intercarrier interference (ICI). In this paper, we propose a blind beamforming algorithm for single-carrier frequency-division multiple-access (SC-FDMA) systems under insufficient CP sceIn cyclic prefix (CP)-based transmission systems, if the time duration of the cyclic extension is shorter than the channel impulse response duration, system performance is degraded due to the introduction of intersymbol interference (ISI) and intercarrier interference (ICI). In this paper, we propose a blind beamforming algorithm for single-carrier frequency-division multiple-access (SC-FDMA) systems under insufficient CP scenarios. In addition, we also consider the effects of carrier frequency offsets (CFOs) in the processing schemes. The simulation results are presented by employing an SC-FDMA uplink signal model to illustrate the efficacy of the proposed algorithms.narios. In addition, we also consider the effects of carrier frequency offsets (CFOs) in the processing schemes. The simulation results are presented by employing an SC-FDMA uplink signal model to illustrate the efficacy of the proposed algorithms.

Multicarrier modulation with blind detection capability using cosine modulated filter banks

The cosine modulated filter bank (CMFB) is introduced as a multicarrier modulation (MCM) technique for wideband data transmission over wireless channels. Under the name discrete wavelet multitone modulation, CMFB has been considered for data transmission over digital subscriber lines. We propose a new receiver structure that is different from those proposed previously. The new structure simplifies the task of channel equalization, by reducing the number of equalizer parameters significantly. We also propose a novel blind equalization algorithm that fits very nicely in the proposed structure. Moreover, we discuss the bandwidth efficiency of the proposed CMFB-MCM system and show that it is superior to the conventional (single carrier) quadrature amplitude modulation (QAM) and orthogonal frequency-division multiplexing (OFDM). The CMFB is found to be a signal processing block that stacks a number of vestigial sideband modulated signals in a number of overlapping subchannels in the most efficient way. The proposed CMFB-MCM is also compared to OFDM with respect to bit-error rate performance. Under the conditions that the channel impulse response duration remains less than the length of cyclic prefix, OFDM is found marginally superior to CMFB-MCM. However, OFDM degrades very fast when the channel impulse response duration exceeds the length of the cyclic prefix. CMFB-MCM, on the other hand, is found less sensitive to variations in channel impulse response duration.