A Dual-Function Massive MIMO Uplink OFDM Communication and Radar Architecture

This paper proposes a joint uplink massive multiple-input-multiple-output (MIMO) communication and orthogonal frequency-division multiplexing (OFDM) radar sensing architecture. Specifically, uplink communication and short-range radar sensing are considered, where the user equipments (UEs) transmit data to the base-station (BS), which simultaneously receives radar returns from the targets over the same subcarriers. Hence, the signals received at each BS antenna include radar returns and communication signals to be processed for extracting the sensing and communication data. The separation and detection of such signals are achieved by utilizing the channel diversity between the UEs and the targets. To this end, the UEs' signals are first detected and demodulated, and then subtracted from the received signal to acquire the radar returns. Symbol-based radar processing is then employed, as it provides substantial processing gains, and its detection performance is independent of the transmitted radar waveform. Furthermore, self-interference - due to the simultaneous operation of transmit and receive antennas - is taken into account. The communication rate and normalized error of the radar-target channel estimation are mathematically analyzed, and the trade-off between the achievable rate and radar detection performance is demonstrated in terms of the output power of the communication and radar sub-systems and the signal-to-noise ratio

Optimized Precoders for Vehicular Massive MIMO RadCom Systems

This paper proposes optimized precoders for dual-functional radar and communication (RadCom) systems to maximize the sum-rate (SR) while satisfying radar target detection and user data rate constraints towards 6G networks. For this purpose, a RadCom precoder scheme that exploits radar interference is utilized with massive multiple-input-multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. Firstly, the communication capacity and radar detection performance metrics are analytically derived. Then, optimum precoders that utilize these analytical expressions are designed via convex optimization to maximize the SR with modest computational complexity. The analytical results are also verified by simulations. The results show that the optimized precoder can substantially enhance the SR compared to the benchmark methods

Performance analysis of adaptive hybrid nonlinear preprocessors for impulsive noise mitigation over power-line channels

© 2015 IEEE. Impulsive noise (IN) over power-lines can significantly corrupt communication signals. To diminish its effect, a nonlinear preprocessor is usually applied at the receiver's frond-end to blank or clip the incoming signal when it exceeds a certain threshold. Applying a combination of blanking and clipping in a hybrid fashion is characterized by two thresholds T1 and T2 (T2 = αT1), where α is a scaling factor. Previous studies assumed a fixed value for the scaling factor and found that optimizing the threshold T1 is the key to improve performance. In contrast to the existing work, in this paper we show that the performance of the hybrid technique is sensitive not only to the threshold but also to the scaling factor, and in light of this we propose to enhance the capability of this technique by optimizing the two parameters. System Performance is evaluated mathematically in terms of the probability of missed blanking/clipping (Pm), probability of IN identification (Pi) and the symbol error rate (SER) performance. In all our investigations, simulation results are provided to validate the analysis. Results reveal that the proposed scheme is superior in terms of minimizing Pm and maximizing Pi which consequently results in improving SER performance

Improved DPTE technique for impulsive noise mitigation over power-line communication channels

© 2015 Elsevier GmbH. All rights reserved. Signal blanking is a simple and efficient method commonly used to reduce the impact of impulsive noise (IN) over power-lines. There are two main ways to implement this method, namely, (a) the unmodified scheme and (b) the dynamic peak-based threshold estimation (DPTE) technique. Concerning the first, in order to optimally blank IN the noise characteristics must be made available at the receiver otherwise the system performance will degrade dramatically. Whereas in the DPTE case, only estimates of the signal peaks are required to achieve best performance. In this paper, however, we propose to enhance the capability of the conventional DPTE technique by preprocessing the signal at the transmitter side. To evaluate system performance, we consider the probability of blanking error (Pb), probability of missed blanking (Pm) and probability of successful detection (Ps). In light of this, closed-form analytical expressions for the three probabilities are derived which are then validated with simulations. The results reveal that the proposed DPTE technique can significantly minimize both Pb and Pm and maximize Ps. It is also shown that the proposed system is able to attain up to 3.5 dB and 1 dB SNR enhancement relative to the unmodified and the conventional DPTE techniques, respectively, as well as improving the symbol error rate performance

Improving blanking/clipping based impulsive noise mitigation over powerline channels

Powerline communication technology is a promising communication platform for smart grid and has nowadays become an attractive alternative for data transmission in the home. Iimpulsive noise (IN) over such channels, however, remains the main factor responsible for degrading communication signals. Many techniques for mitigating IN have been reported in the literature the most common of which is preceding the OFDM receiver with blanking, clipping or hybrid (combined blanking-clipping) nonlinear preprocessors. In this paper, we propose to enhance the capability of these techniques by preprocessing the signal at the transmitter. A closed-form analytical expression for the probability of IN detection error is derived and the problem of blanking/clipping threshold selection is also considered. The results reveal that the proposed is able to minimize the probability of IN detection error significantly and can provide up to 3dB SNR improvement relative to the conventional techniques. © 2013 IEEE

Efficient SLM based impulsive noise reduction in powerline OFDM communication systems

A very efficient method to mitigate impulsive noise (IN) over powerline channels is to precede the OFDM demodulator with a blanker to zero the incoming signal when it exceeds a certain threshold. Blanking the signal samples unaffected by IN exceeding this threshold, i.e. blanking errors, can cause severe performance degradation. For best performance, the optimal blanking threshold must be determined and this requires some prior and accurate knowledge about the characteristics of IN; this method is referred to as the unmodified method. In this paper, we propose an algorithm to enhance the capability of such methods by processing the OFDM signal at the transmitter to make the IN more easily identifiable at the receiver. This is done by simply deploying a peak to average power ratio (PAPR) reduction technique such as the selective mapping (SLM) scheme. A closed-form analytical expression for the probability of blanking error is derived and the problem of blanking threshold optimization is addressed under various IN environments. The results reveal that the proposed technique is able to minimize the probability of blanking error dramatically and can provide significant SNR improvement relative to the unmodified scheme. It will also be shown that when SLM is implemented with a large number of phase sequences, not only a considerable SNR enhancement is achieved but also, unlike the unmodified method, it becomes feasible to completely alleviate the need for any previous knowledge about the IN characteristics for optimal blanking. © 2013 IEEE

Single-carrier FDMA with blanking/clipping for mitigating impulsive noise over PLC channels

Communication signals over power-line channels can be affected greatly by impulsive noise (IN). The effect of this noise is commonly reduced with the application of a nonlinear preprocessor at the receiver such as blanking, clipping or hybrid (combined blanking and clipping) that blanks and/or clips the received signal when it exceeds a certain threshold. Erroneous blanking/clipping of the unaffected signals can lead to significant performance degradations. It is found that determining the optimal blanking/clipping threshold is the key for achieving best performance. In contract to these studies, we show in this paper that the performance of the nonlinear preprocessing-based method is not only impacted by the blanking/clipping threshold but also by the transmitted signal's peak-to-average power ratio (PAPR). In light of this and for more efficient IN cancellation we, therefore, propose to implement single-carrier FDMA (SC-FDMA), which inherently has low PAPR properties, combined with a nonlinear preprocessor at the receiver. The results reveal that the proposed system can provide significant enhancements in terms of minimizing the probability of IN detection error as well as achieving up to 4dB gain in the output signal-to-noise ratio relative to the conventional OFDM case. © 2014 IEEE

Threshold and scaling factor optimization for enhancing impulsive noise cancellation in PLC systems

© 2014 IEEE. Power-line communication (PLC) is considered as the backbone of smart grid. Impulsive noise (IN) over such channels, however, remains the main factor responsible for degrading communication signals. A simple method to mitigate IN over PLC channels is to precede the receiver with a nonlinear preprocessor to blank and/or clip the incoming signal when it exceeds a certain threshold. Applying a combination of blanking and clipping in a hybrid fashion was shown to provide the best performance. The hybrid scheme is characterized by two thresholds Τ1 and T2 (Τ1 = α.T2), where a is a scaling factor. Previous studies assume a fixed value for the scaling factor and found that optimizing the threshold T2 is the key to enhance performance. In this paper, we show that the performance of this scheme is sensitive not only to the threshold, but also to the scaling factor. With this in mind, a mathematical expression for the output signal-to-noise ratio as a function of the threshold and scaling factor is formulated and used to optimize the hybrid scheme performance. Simulation results are also provided to validate our analysis. The results reveal that using an adaptive hybrid scheme with an optimally selected threshold and scaling factor always outperforms other nonlinear schemes

On the performance of multi-user DS-CDMA systems over power-line channels

© 2014 IEEE. In this paper we propose to implement direct-spread code-division multiple access (DS-CDMA) over powerline channels combined with blanking at the receiver to reduce the effect of impulsive noise (IN). Two spreading sequences are investigated in this study, namely, Walsh-Hadamard and polyphase codes. The impact of different loading scenarios, ranging from light-to full-loading, on the probability of blanking error and output signal-to-noise ratio (SNR) performance is examined. In addition, the optimal blanking threshold that maximizes the system performance is considered for various system loadings and under different IN conditions. Results reveal that the proposed technique is able to provide remarkable output SNR improvement relative to the conventional DS-CDMA system. It is also shown that this enhancement becomes more significant when the number of active users is reduced

Preprocessing-based impulsive noise reduction for power-line communications

Signal blanking is a common technique for mitigating impulsive noise (IN) in power-line communications. When signal samples unaffected by IN are erroneously blanked, part of the useful signal will be lost and performance will degrade. In this paper, we show that the performance of this technique is sensitive not only to the blanking threshold but also to the signal's peak-to-average power ratio (PAPR). We thus propose enhancing the capability of the conventional blanking technique by preprocessing the signal at the transmitter. With this in mind, a closed-form analytical expression for the probability of blanking error is then derived and the problem of blanking threshold optimization is addressed. The results reveal that the proposed technique is able to minimize the probability of blanking error dramatically and can provide up to 3.5-dB signal-to-noise ratio (SNR) improvement relative to the conventional technique. Furthermore, it will be shown that if the transmitted signal's PAPR is maintained below a certain threshold, then not only can a considerable SNR enhancement be achieved but it is also possible to completely alleviate the need for any prior knowledge about the IN characteristics in order to optimally blank it. © 2014 IEEE