Lee, It Ee; Guo, Yujian; Ng, Tien Khee; Park, Kihong; Alouini, Mohamed-Slim; Ooi, Boon S.(2017 Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR), Institute of Electrical and Electronics Engineers (IEEE), 2017-11-30)[Conference Paper]
Underwater wireless optical communication (UWOC) has been widely studied as a promising alternative to establish reliable short-range marine communication links. Microscopic particulates suspended in various ocean, harbor and natural waters will alter the propagation characteristics of the optical signals underwater. In this paper, we demonstrate a gigabit near-infrared (NIR)-based UWOC link using an 808-nm laser diode, to examine the feasibility of the proposed system in mitigating the particle scattering effect over turbid waters. We show that the NIR wavelengths presents greater resilience to the aqueous suspension of these micro-sized particles with a smaller scattering effect due to its longer wavelength, as evident by the smaller variations in the optical beam transmittance. It is also observed that the error performance is improved at higher concentrations albeit the significant reduction in received signal power. We further demonstrate that the overall frequency response of the system exhibits a bandwidth enhancement up to a few tens of MHz with increasing concentrations.
Lee, It Ee; Guo, Yong; Ng, Tien Khee; Park, Kihong; Alouini, Mohamed-Slim; Ooi, Boon S.(Conference on Lasers and Electro-Optics, The Optical Society, 2017-05-08)[Conference Paper]
We demonstrate a gigabit near-infrared-based underwater wireless optical communication link using an 808-nm laser diode to mitigate the particle scattering effect in turbid medium. An improvement in the error performance is observed with increasing concentrations.
Soury, Hamza; Elsawy, Hesham; Alouini, Mohamed-Slim(2017 IEEE International Conference on Communications (ICC), Institute of Electrical and Electronics Engineers (IEEE), 2017-07-31)[Conference Paper]
This paper develops a mathematical paradigm to study downlink error rates and throughput for half-duplex (HD) terminals served by a full-duplex (FD) base station (BS). Particularly, we study the dominant intra-cell interferer problem that appears between HD users scheduled on the same FD-channel. The distribution of the dominant interference is first characterized via its distribution function, which is derived in closed-form. Assuming Nakagami-m fading, the probability of error for different modulation schemes is studied and a unified closed-form expression for the average symbol error rate is derived. To this end, we show the effective downlink throughput gain, harvested by employing FD communication at a BS that serves HD users, as a function of the signal-to-interference-ratio when compared to an idealized HD interference and noise free BS operation.
Arshad, Rabe; Elsawy, Hesham; Sorour, Sameh; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim(2016 IEEE Global Communications Conference (GLOBECOM), Institute of Electrical and Electronics Engineers (IEEE), 2017-02-07)[Conference Paper]
Network densification has always been an important factor to cope with the ever increasing capacity demand. Deploying more base stations (BSs) improves the spatial frequency utilization, which increases the network capacity. However, such improvement comes at the expense of shrinking the BSs' footprints, which increases the handover (HO) rate and may diminish the foreseen capacity gains. In this paper, we propose a cooperative HO management scheme to mitigate the HO effect on throughput gains achieved via cellular network densification. The proposed HO scheme relies on skipping HO to the nearest BS at some instances along the user's trajectory while enabling cooperative BS service during HO execution at other instances. To this end, we develop a mathematical model, via stochastic geometry, to quantify the performance of the proposed HO scheme in terms of coverage probability and user throughput. The results show that the proposed cooperative HO scheme outperforms the always best connected based association at high mobility. Also, the value of BS cooperation along with handover skipping is quantified with respect to the HO skipping only that has recently appeared in the literature. Particularly, the proposed cooperative HO scheme shows throughput gains of 12% to 27% and 17% on average, when compared to the always best connected and HO skipping only schemes at user velocity ranging from 80 km/h to 160 Km/h, respectively.
Sifaou, Houssem; Park, Kihong; Kammoun, Abla; Alouini, Mohamed-Slim(2017 IEEE International Conference on Communications (ICC), Institute of Electrical and Electronics Engineers (IEEE), 2017-07-31)[Conference Paper]
Visible light communication (VLC) is an emerging technique that uses light-emitting diodes (LED) to combine communication and illumination. It is considered as a promising scheme for indoor wireless communication that can be deployed at reduced costs while offering high data rate performance. In this paper, we focus on the design of the downlink of a multi-user VLC system. Inherent to multi-user systems is the interference caused by the broadcast nature of the medium. Linear precoding based schemes are among the most popular solutions that have recently been proposed to mitigate inter-user interference. This paper focuses on the design of the optimal linear precoding scheme that solves the max-min signal-to-interference-plus-noise ratio (SINR) problem. The performance of the proposed precoding scheme is studied under different working conditions and compared with the classical zero-forcing precoding. Simulations have been provided to illustrate the high gain of the proposed scheme.
Shen, Chao; Guo, Yujian; Sun, Xiaobin; Liu, Guangyu; Ho, Kang-Ting; Ng, Tien Khee; Alouini, Mohamed-Slim; Ooi, Boon S.(2017 Opto-Electronics and Communications Conference (OECC) and Photonics Global Conference (PGC), Institute of Electrical and Electronics Engineers (IEEE), 2017-12-13)[Conference Paper]
Laser diode based visible light communication link with data rate of 2.2 Gbps over a 12-meter underwater channel is reported using non-return-to-zero on-off keying modulation scheme. The underwater optical wireless communication link beyond 10-meter can be achieved using visible lasers.
Oubei, Hassan M.; Elafandy, Rami T.; Park, Kihong; Ng, Tien Khee; Alouini, Mohamed-Slim; Ooi, Boon S.(Institute of Electrical and Electronics Engineers (IEEE), 2017-10)[Conference Paper]
We experimentally evaluate the performance of underwater wireless optical communication (UWOC) links in the presence of different air bubbles. Air bubbles of different sizes and densities are generated by using an air pipe in conjunction with a submersible water pump of variable flow rate that help break up large bubbles into smaller bubbles. Received signal intensity measurements show that bubbles significantly degrade the performance of UWOC links. Large bubbles completely obstruct the optical beam and cause a deep fade. However, as the bubble size decreases, the level of deep fade also decreases because the optical beam is less susceptible to complete obstruction and more light reaches the detector. We also show that beam expansion could help mitigate the performance degradation due to the deep fade caused by air bubbles scatters in the channel.
Alouini, Mohamed-Slim(Institute of Electrical and Electronics Engineers (IEEE), 2017-08)[Conference Paper]
5G wireless communication networks are expected to fulfill the demand for higher data rates, lower latency, and/or massive connectivity of a growing number of users/devices exploiting a variety of wireless applications. This envisioned rapid increase in the use of wireless services lead the wireless research community to start looking at new technologies to address problems related to the radio-frequency (RF) spectrum exhaustion. This includes the development of (i) new techniques and concepts such as massive multiple input multiple output (MIMO) systems and heterogeneous networks to improve the spectral efficiency at the link and network layers, respectively, and (ii) novel schemes to better utilize the unregulated bandwidth in particular in the upper millimeter wave, THz, and optical portion of the spectrum. This talk will first go briefly over the vision and goals of 5G wireless communication networks. Then it presents some of these emerging enabling technologies that need to be developed to pave the way towards the successful roll-out and operation of these future wireless networks. Finally, the talk offers at the end an overview of some of the recent results in the areas of massive MIMO systems, full-duplex communication systems, and optical (Li-Fi) wireless communication systems.
Sapenov, Yerzhan; Chaaban, Anas; Rezki, Zouheir; Alouini, Mohamed-Slim(Institute of Electrical and Electronics Engineers (IEEE), 2017-06)[Conference Paper]
In this paper, an optical wireless multiple-input single-output communication system employing intensity-modulation direct-detection is considered. Subject to a per transmit-aperture power constraint, the performance of direct current (DC) offset space-time block codes (STBC) is studied in terms of pairwise error probability (PEP). It is shown that among the class of DC-STBCs, the worst case PEP, i.e., the one corresponding to the minimum distance between two codewords, is minimized by repetition coding (RC) for any channel state. Therefore, it follows that among all DC-STBCs, RC is optimal in terms of worst case PEP under any turbulence statistics. This result agrees with previously published numerical results showing the superiority of RC in such systems. It also agrees with previously published analytical results on this topic under lognormal turbulence and further extends it to arbitrary turbulence statistics. Numerical results provided to verify this indicate that RC is not only optimal in terms of worst case PEP, but also in terms of average error probability.
Chaaban, Anas; Varshney, Lav R.; Alouini, Mohamed-Slim(Institute of Electrical and Electronics Engineers (IEEE), 2017-06)[Conference Paper]
The capacity region of the class of injective semi-deterministic two-way channels (TWCs) is investigated in this paper. To characterize this capacity, two conditions under which Shannon's bounds on the capacity region of TWCs are tight are first given. Using those conditions, it is shown that the capacity of this class of TWCs is characterized by the rectangle formed by the one-way capacities. This proves that adaptation is not needed for this class. This class encompasses, among others, all memoryless additive channels with input-independent noise, and hence, adaptation is useless for all such channels. This also shows that there exist continuous additive TWCs not of the exponential family type for which adaptation is not necessary. An example of a Cauchy TWC is given, and its capacity is characterized in closed form under a logarithmic constraint. Finally, the impact of the dependence of the noise on the inputs is discussed, and it is shown that adaptation may still be useless in such cases.
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