Browsing by Author "Bariah, L."
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ArticlePublication Open Access Capacity analysis of NOMA-enabled underwater VLC networks(IEEE, 2021) Elamassie, Mohammed; Bariah, L.; Uysal, Murat; Muhaidat, S.; Sofotasios, P. C.; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, MuratVisible light communication (VLC) has recently emerged as an enabling technology for high capacity underwater wireless sensor networks. Non-orthogonal multiple access (NOMA) has been also proven capable of handling a massive number of sensor nodes while increasing the sum capacity. In this paper, we consider a VLC-based underwater sensor network where a clusterhead communicates with several underwater sensor nodes based on NOMA. We derive a closed-form expression for the NOMA system capacity over underwater turbulence channels modeled by lognormal distribution. NOMA sum capacity in the absence of underwater optical turbulence is also considered as a benchmark. Our results reveal that the overall capacity of NOMA-enabled Underwater VLC networks is significantly affected by the propagation distance in underwater environments. As a result, effective wireless transmission at high and moderate spectral efficiency levels can be practically achieved in underwater environments only in the context of local area networks. Moreover, we compare the achievable capacity of NOMA system with its counterpart, i.e., orthogonal frequency division multiple access (OFDMA). Our results reveal that NOMA system is not only characterized by achieving higher sum capacity than the sum capacity of its counterpart, OFDMA system. It is also shown that the distances between sensor nodes and the clusterhead for achieving the highest sum capacity in these two multiple access systems are different.ArticlePublication Open Access Comparative characterization of indoor VLC and MMW communications via ray tracing simulations(IEEE, 2023) Hosseinabadi, Fahimeh Aghaei; Eldeeb, H. B.; Bariah, L.; Muhaidat, S.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Hosseinabadi, Fahimeh AghaeiThe demand for ultra-high-speed indoor wireless connectivity is ever-increasing, which poses unique challenges for the next generation wireless communication system design. This has prompted the exploration of higher frequency bands including millimeter wave (MMW) and visible light bands in addition to the conventional sub-6 GHz band. This paper provides a comprehensive comparison of the propagation channels of these frequency bands under the same indoor environment and scenarios. We adopt ray tracing techniques for site-specific channel modeling, which enables the consideration of the three-dimensional models of the indoor environment and objects inside. It allows us to take into account different frequencies, i.e., 2.4 GHz, 6 GHz, 28 GHz, 60 GHz, 100 GHz, and visible light band as well as different transmitter types, i.e., omnidirectional/directional antennas for radio frequency systems and indoor luminaries for visible light communications (VLC). For different frequencies under consideration, we obtain channel impulse responses (CIRs) and present the channel path losses for various user trajectories in indoor environments. Furthermore, we propose closed-form expressions for the cumulative distribution functions (CDFs) of received power levels for all frequency bands under consideration. Our results demonstrate that VLC channels exhibit lower path loss than that in MMW bands but higher than that of 2.4 GHz band. In addition, it is observed that VLC systems exhibit more sensitivity to shadowing and blockage effects. Our findings further indicate that the characteristics of the propagation channel are greatly influenced by the antenna type. For instance, using omnidirectional and rectangular patch antennas results in lower path loss compared to horn antennas, and this difference becomes more significant as the transmission distance decreases.ArticlePublication Open Access Coordinated beamforming design for multi-user multi-cell MIMO VLC networks(IEEE, 2022-06) Naser, S.; Bariah, L.; Jaafar, W.; Muhaidat, S.; Al-Qutayri, M.; Uysal, Murat; Sofotasios, P. C.; Electrical & Electronics Engineering; UYSAL, MuratInter-cell interference (ICI) and inter-user interference (IUI) constitute a major issue towards achieving the optimum spectral efficiency (SE) and energy efficiency (EE) performance in multi-cell visible light communication (VLC) networks. Hence, advanced multiple access techniques need to be leveraged in order to improve the provided service to the users of such interfering networks. To this end, the present contribution proposes the integration of coordinated beamforming (CB) with rate-splitting multiple access (RSMA) in multi-cell VLC systems. Specifically, we consider the design of beamformers for the common and private streams in a coordinated manner between different attocells, which is shown to provide efficient mitigation of the incurred interference. Additionally, the formulated optimization problem aims to minimize the sum of the mean squared error across all attocells in order to jointly determine the optimum receive filters and coordinated transmit beamformers for RSMA streams. In this context, we illustrate through extensive computer simulations, which are carried out in a realistic setup that assumes noisy channel state information acquisition, the distinct flexibility and robustness of CB-based RSMA in mitigating the incurred interference. Finally, the offered results demonstrate the superiority of CB-based RSMA in terms of achievable SE and EE performance in multi-cell VLC networks compared to the conventional CB-based space division multiple access counterpart.ArticlePublication Metadata only Interference management strategies for multiuser multicell MIMO VLC systems(IEEE, 2022-09) Naser, S.; Bariah, L.; Muhaidat, S.; Al-Qutayri, M.; Uysal, Murat; Sofotasios, P. C.; Electrical & Electronics Engineering; UYSAL, MuratThis paper investigates different precoding strategies for rate splitting multiple access (RSMA) in the downlink of multi-cell visible light communication (VLC) networks. Since classical Shannon capacity formula does not hold for VLC, we first provide a lower bound on the channel capacity for RSMA in such interfering networks. Then, we formulate a spectral efficiency maximization problem to jointly find the optimal rate-splitting and transmit precoding. Beside that, since cell-edge users suffer from additional inter-cell interference, we propose to design the precoders of different RSMA signals utilizing coordinated beamforming (CB). Subsequently, aiming to improve the performance of the CB design for RSMA, while maintain a reduced complexity, we introduce two enhanced precoding strategies for RSMA. To the best of the authors' knowledge such a contribution has not been considered before in the open literature. It is shown in the paper that the formulated optimization problem is non-convex and a sub-optimal, yet, a low complexity solution can be obtained efficiently using semi-definite relaxation combined with successive convex approximation. Through analytical results, we illustrate the flexibility and superiority of the proposed precoding strategies for RSMA over conventional coordinated space division multiple access and non-orthogonal multiple access for different scenarios and network loads.ArticlePublication Metadata only Non-orthogonal multiple access-based underwater VLC systems in the presence of turbulence(IEEE, 2022-02) Bariah, L.; Elamassie, Mohammed; Muhaidat, S.; Sofotasios, P. C.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; ELAMASSIE, MohammedThe promising potential of underwater applications in visible light communication (VLC) systems has recently gained considerable research attention, as an efficient technology for enabling high data rate, massive connectivity, and ultra-low latency. Different from indoor VLC, underwater wireless communications experience harsh environmental challenges, yielding a degraded performance. Non-orthogonal multiple access (NOMA) was introduced to enhance spectral efficiency and connectivity of underwater VLC communications. In this paper, we develop a mathematical framework to evaluate the performance of NOMA-enabled underwater VLC systems in the presence of turbulence. Specifically, we derive a closed-form expression for the outage probability of NOMA over lognormal channels, while considering the effect of path loss and turbulence. The derived analytical results with the corresponding numerical results demonstrate that the transmission distance between laser diode and sensor nodes (SNs) has a high impact on the outage performance of the SNs, due to the increased turbulence level with increased distance. Moreover, the presented results show the effect of the water type on the outage performance of the SNs and on the optimum values of the power coefficients.ArticlePublication Open Access Space-time block coded spatial modulation for indoor visible light communications(IEEE, 2022-02) Naser, S.; Bariah, L.; Muhaidat, S.; Al-Qutayri, M.; Uysal, Murat; Sofotasios, P.; Electrical & Electronics Engineering; UYSAL, MuratVisible light communication (VLC) has been recognized as a promising technology for handling the continuously increasing quality of service and connectivity requirements in modern wireless communications, particularly in indoor scenarios. In this context, the present work considers the integration of two distinct modulation schemes, namely spatial modulation (SM) with space time block codes (STBCs), aiming at improving the overall VLC system reliability. Based on this and in order to further enhance the achievable transmission data rate, we integrate quasi-orthogonal STBC (QOSTBC) with SM, since relaxing the orthogonality condition of OSTBC ultimately provides a higher coding rate. Then, we generalize the developed results to any number of active light-emitting diodes (LEDs) and any M-ary pulse amplitude modulation size. Furthermore, we derive a tight and tractable upper bound for the corresponding bit error rate (BER) by considering a simple two-step decoding procedure to detect the indices of the transmitting LEDs and then decode the signal domain symbols. Notably, the obtained results demonstrate that QOSTBC with SM enhances the achievable BER compared to SM with repetition coding (RC-SM). Finally, we compare STBC-SM with both multiple active SM (MASM) and RC-SM in terms of the achievable BER and overall data rate, which further justifies the usefulness of the proposed scheme.