Suhail Al-Dharrab

Cooperative underwater acoustic communications [Accepted From Open Call]

This article presents a contemporary overview of underwater acoustic communication (UWAC) and investigates physical layer aspects on cooperative transmission techniques for future UWAC systems. Taking advantage of the broadcast nature of wireless transmission, cooperative communication realizes spatial diversity advantages in a distributed manner. The current literature on cooperative communication focuses on terrestrial wireless systems at radio frequencies with sporadic results on cooperative UWAC. In this article, we summarize initial results on cooperative UWAC and investigate the performance of a multicarrier cooperative UWAC considering the inherent unique characteristics of the underwater channel. Our simulation results demonstrate the superiority of cooperative UWAC systems over their point-to-point counterparts.

Cooperative diversity in the presence of impulsive noise

Although there already exists a rich literature on cooperative diversity, current results are mainly restricted to the conventional assumption of additive white Gaussian noise (AWGN). AWGN model realistically represents the thermal noise at the receiver, but ignores the impulsive nature of atmospheric noise, electromagnetic interference, or man-made noise which might be dominant in many practical applications. In this paper, we investigate the performance of cooperative communication over Rayleigh fading channels in the presence of impulsive noise modeled by Middleton Class A noise. Specifically, we consider a multi-relay network with amplify-and-forward relaying. Through the derivations of pairwise error probability, we quantify the diversity advantages. Based on the minimization of a union bound on the error rate performance, we formulate optimal power allocation schemes and demonstrate significant performance gains over their counterparts with equal power allocation. An extensive Monte Carlo simulation is also presented to illustrate the performance of cooperative schemes in various impulsive environments.

Error Probability of DF Relaying with Pilot-Assisted Channel Estimation over Time-Varying Fading Channels

In this paper, we investigate the error rate performance of a cooperative network with adaptive decode-and-forward (DF) relaying over time-selective frequency-flat Rayleigh-fading channels. We assume pilot-symbol-assisted modulation (PSAM) for the estimation of time-varying fading channel coefficients. For the system under consideration, we derive an exact closed-form expression for the average bit/symbol error rate, which is further validated through Monte Carlo simulations. Such closed-form solutions are highly desirable because they allow for rapid and efficient performance evaluation. Through the derived expression, we also demonstrate the effect of various system parameters such as the number of relays, Doppler values, and filter length on system performance.

Aspect dependent multipath ghost suppression in TWRI under compressive sensing framework

In through-the-wall radar imaging, multipath propagation can create ghost targets which can adversely affect the image reconstruction process. The fact that the ghost positions changes with the radar locations which is referred to as aspect dependence has been reported as among the features distinguishing ghost from true target. This paper proposes ghost suppression method which exploit the aspect dependence feature under compressive sensing framework. The existing signal model is modified so that the location of reflecting geometry is no longer a constraint. Also the sensing matrix is greatly reduced making the methods more attractive. Simulation results demonstrate the effectiveness of the proposed methods.

Information theoretic performance of cooperative underwater acoustic communications

Cooperative communication is considered as a major enabling technique to meet the demanding performance requirements of future underwater acoustic (UWA) communication systems. In this paper, we investigate the information theoretic performance of a cooperative UWA system to provide insight into the fundamental performance limits imposed by underwater acoustic channels. We first propose an approximate statistical model for the non-stationary ambient noise. The proposed model allows mathematical tractability and is a good fit for most operating frequencies in practical systems. Based on this ambient noise model, we investigate the outage performance of a precoded cooperative multicarrier UWA system with amplify-and-forward (AF) relaying. Our numerical results for cooperative UWA systems demonstrate significant performance gains over point-to-point systems. The impact of several system and environmental parameters on the performance is further demonstrated.

Outage capacity regions of multicarrier DF relaying in underwater acoustic channels

In this paper, we investigate the information theoretical limits on the performance of cooperative multicarrier underwater acoustic (UWA) communication systems. We assume decode-and-forward (DF) relaying and consider non-orthogonal half-duplex cooperation. Under the assumptions of sparse and frequency-selective Rician fading channel and correlated Gaussian ambient noise, we derive the maximum achievable sum-rate and common/individual outage capacity regions for the cooperation protocol under consideration. We further investigate the effect of several parameters such as underwater temperature, carrier frequency, etc. on the outage capacity regions.

Cooperative Diversity over Fading Channels with Impulsive Noise

Although there already exists a rich literature on cooperative diversity, current results are mainly restricted to the conventional assumption of additive white Gaussian noise (AWGN). AWGN model realistically represents the thermal noise at the receiver, but ignores the impulsive nature of atmospheric noise, electromagnetic interference, or man-made noise which might be dominant in many practical applications. In this paper, we investigate the performance of cooperative communication over Rayleigh fading channels in the presence of impulsive noise modeled by Middleton Class A noise. Specifically, we consider a multi-relay network with amplify-and-forward relaying. Through the derivations of the pairwise error probability, we quantify the diversity advantages. Based on the minimization of a union bound on the error rate performance, we formulate optimal power allocation schemes and demonstrate significant performance gains over their counterparts with equal power allocation. An extensive Monte Carlo simulation is also presented to illustrate the performance of cooperative schemes in various impulsive environments.

Performance of multicarrier cooperative communication systems over underwater acoustic channels

Multicarrier transmission in the form of orthogonal frequency division multiplexing (OFDM) is an efficient method to handle inter-symbol interference resulting from the frequency selectivity of the underwater acoustic (UWA) channels. OFDM can be further combined with cooperative transmission to benefit from the spatial diversity advantages and improve the performance over conventional point-to-point UWA communication systems. In this study, the authors consider a cooperative OFDM UWA communication system and investigate the outage performance for both amplify-and-forward relaying and decode-and-forward (DF) relaying. They derive expressions for bounds on outage probability and outage capacity. Monte Carlo simulations corroborate and quantify the enhanced performance of cooperative OFDM UWA communication compared with direct transmission systems. Through numerical simulations, they investigate the impact of geometry on outage probability and signal-to-noise ratio requirements in cooperative OFDM UWA communication with DF relaying. Furthermore, the authors analyse the effects of relay location and carrier frequency on the outage probability for both relaying schemes.