Hongzhi Zhao

Performance Analysis of

It is known that the keyhole or pinhole effect can severely degrade the performance of multiple-input-multiple-output (MIMO) communication systems. In this paper, the outage probability and error probability of orthogonal space-time block codes with m transmit and n receive antennas over keyhole fading channels are analyzed. Closed-form outage probability and symbol/bit error rate expressions are derived with M-ray phase-shift keying (M-PSK) and M-ray quadrature amplitude modulation (M-QAM) signaling. It is found that the exact error probability expressions have two different forms for m = n and m ne n, respectively. Furthermore, when m ne n, approximate error rate expressions are derived at high signal-to-noise ratios (SNRs), whereas there are no asymptotic expressions for m = n. Simulation results are provided to verify our analytical results.

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In this letter, we propose an eigen domain interference rejection combining (E-IRC) algorithm to suppress the narrowband interference (NBI). The proposed E-IRC algorithm explores the difference between the time domain autocorrelation matrices of the NBI and the desired signal and implements the IRC in the eigen domain. Compared with the traditional IRC, which rejects the interference in the spatial domain, the proposed E-IRC algorithm exploits the characteristics of the received signal in both the time and spatial domain to suppress the NBI and thus yields better performance. Simulation results are presented to demonstrate the advantage of the proposed algorithm.

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Space-time block codes are known to be a powerful tool to achieve full spatial diversity gain while maintaining a very simple receiver structure. In this paper, the authors analyze the asymptotic error performance of orthogonal space-time block codes over flat Nakagami-m fading channels. Both identical and non-identical m-distributions are considered. Based on the moment generation function (MGF) approach, the closed-form asymptotic symbol error probabilities over Nakagami-m fading channels are derived. Compared to the previous works in literature, our results are more accurate and more general. Simulation results are provided to verify our analytical results.

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Correct time and frequency synchronization is important for the performance of orthogonal frequency-division multiplexing (OFDM) system. While using the partial power training sequences to synchronize in orthogonal frequency-division multiplexing (OFDM) system, the received data signals will be interfered by the training sequences. In this paper, we give a method for suppressing the interference caused by the training sequence, and introduce an optimized formula for the partial interference canceling factor of partial power training sequence. The above technique is evaluated by means of pilot assistant coherent OFDM system under time-varying multipath Rayleigh fading channels, and the linear interpolation channel estimator is employed to exploit the frequency domain correlation. Especially we focus on only one OFDM symbol in a packet transmission, that is, both the OFDM data and the training sequences are included in one OFDM symbol, and there are no other symbols before or after it. Both theoretical and simulated results of the above technique are presented. It has been shown that the better BER performance can be achieved as compared with no separation, and only the one OFDM symbol can accomplish user data communication assignment.

-QAM Modulated Orthogonal Space–Time Block Codes in Keyhole Channels

Considering a broadband co-frequency and co-time full duplex (CCFD) transceiver, which transmits and receives at the same time and frequency resources, the previous studies propose many self-interference cancellation algorithms in the radio frequency (RF) domain, but lack their performance analysis. Therefore, we make an attempt to analyze the optimal self-interference cancellation performance in the RF domain of a CCFD transceiver, by adopting the general multi-tap self-interference cancellation structure. In detail, the optimal RF self-interference cancellation performance of a CCFD transceiver is derived by using the optimal parameters of the RF multi-tap self-interference canceller. By analysis and simulation, the optimal RF self-interference cancellation performance of a CCFD transceiver is related with the signal bandwidth, carrier frequency, and differences between the multi-tap delays of the self-interference cancellation structure and multi-path delays of the self-interference channel.

An Eigen Domain Interference Rejection Combining Algorithm for Narrowband Interference Suppression

Considering the radio frequency (RF) self-interference cancellation of the full duplex transceiver, which can transmit and receive simultaneously at the same frequency band. The current studies mainly focus on the feasibility verification, most of which are realized by manual adjustment of the self-interference parameters, and lack of the theoretical analysis of the interference cancellation capability. To solve this problem, an adaptive least mean square (ALMS) algorithm for the self-interference cancellation at the RF stage is presented in this paper. Besides, the convergence and steady state performances of the ALMS algorithm are proved and analyzed, respectively. Analysis and simulation results show that the ALMS algorithm can achieve significant cancellation of the self-interference at the RF stage. Moreover, it is revealed that the interference cancellation performance and convergence speed of the ALMS algorithm are related with the following parameters: the duration per iteration, normalized step size, as well as the ratio of the interference power and total power of the desired signal plus noise.

Space-Time Block Codes in Nakagami Fading Channels with Non-Identical m-Distributions

In certain multiple-input multiple-output (MIMO) fading environments, the offered channel capacity can be very low even when the MIMO channels are uncorrelated; this effect has been termed as keyhole or pinhole effect. In this paper, we present rigorous error rate analysis of orthogonal space time block codes in Nakagami-m keyhole channels with arbitrary fading parameters. Using a moment-generation-function based approach, we provide the exact expressions of symbol error rate. Furthermore, the closed-form asymptotic expressions are derived, based on which one can easily quantify the diversity gain of the considered system with arbitrary m-fading parameters while existing methods in literature fail to do so. Simulation results are also provided to verify our analytical results.

Optimum partial interference canceling factor in pilot assistant coherent OFDM system with power training sequence synchronization

Existing active multi-tone interference (MTI) suppression methods used in direct sequence spread spectrum (DSSS) consider the interference to be time-invariant. However, in most practical scenarios, the interference is time-varying. These conventional analytic models cannot be directly applied to current realistic systems with time-varying interference. Hence, in this paper, we propose a novel approach based on frequency domain interference detection to suppress MTI experiencing a time-varying fading channel. Our approach operates in two steps. Firstly, we calculate the interference decision threshold by the probability of false alarm based on the Neyman-Pearson (NP) criterion. Secondly, we consider that the frequency bin is corrupted by interference, and the corresponding point is set to zero if the magnitude of the received signal exceeds the threshold. The simulation results demonstrate that our proposed method can mitigate time-varying MTI effectively, and can approach the interference-free performance limit over practical ranges of interference power levels and mobility levels.

Performance analysis of RF self-interference cancellation in broadband full duplex systems

In this paper, a novel practical linear minimum square error (LMMSE) channel estimation is proposed to improve the performance of uplink multiple input multiple output (MIMO) single carrier frequency division multiple access (SC-FDMA) systems. We first show the performance deterioration of traditional DFT-based techniques in the uplink, then propose a novel practical LMMSE estimator to solve this problem. Numerical simulation results show that a considerable performance gain is obtained by the proposed approach compared to the DFT-based techniques.

A RF adaptive least mean square algorithm for self-interference cancellation in co-frequency co-time full duplex systems

In this paper we analyze the diversity performance of a general cooperative transmission system equipped with nonregenerative fixed gain relays in flat fading channels. Through outage probability and diversity analysis, we derive the diversity order of a two-hop cooperative transmission system when the relay has an arbitrary fixed gain. It is found that the end-to-end diversity order in such two-hop system is different from that of a nonregenerative system with channel state information (CSI)-assisted relays. Simulation results are provided to verify our analytical results