Browsing by Author "Haas, H."

Now showing 1 - 5 of 5

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Coordinated interference management for visible light communication systems
(IEEE, 2015-11) Kashef, M.; Abdallah, M.; Qaraqe, K.; Haas, H.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we consider the performance of a visible light communication (VLC) network with coordinated interference management. The VLC transmitters are allowed to coordinate their transmissions using one of two transmission schemes so as to maximize a network utility function. In the first technique, namely, orthogonal transmission, the utility function is maximized by optimally partitioning all resources. In the second technique, namely, power control, the transmitters are allowed to share the full spectrum while being allowed to control their power so as to maximize network performance. In particular, for each transmission technique, we optimize a general network utility function under the constraint of a desired illumination power for each VLC transmitter, taking into consideration the optical signal clipping effect due to the physical limitations of the VLC transmitters. For the power control transmission scheme, we develop a computationally efficient method for finding the optimal power values by deriving a computationally efficient way to obtain the achievable spectral efficiency region. Considering the summation and the proportional fairness utility functions, our simulation results show that the optimal transmission scheme depends on the location of the VLC users and the desired illumination power. Also, we show the superiority of the performance of the power control scheme over the orthogonal transmission scheme for low interference regions.
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A European view on the next generation optical wireless communication standard
(IEEE, 2015) Jungnickel, V.; Uysal, Murat; Serafimovski, N.; Baykas, T.; O’Brien, D.; Ciaramella, E.; Ghassemlooy, Z.; Green, R.; Haas, H.; Haigh, P. A.; Gil Jimenez, V. P.; Miramirkhani, Farshad; Wolf, M.; Zvánovec, S.; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
Optical wireless technology uses light for mobile communications. The idea is to simultaneously combine the illumination provided by modern high-power light-emitting diodes (LEDs) with high-speed wireless communications. There have been numerous practical demonstrations of this concept, and the technology is now well matured to be deployed in practice. Independent market analysts forecast a high-volume market for mobile communication devices connected to the ubiquitous lighting infrastructure. This paper aims to make optical and wireless industries aware of the requirement for standardization in this area. The authors present the view of the European COST 1101 research network OPTICWISE towards a next-generation optical wireless standard aiming at data rates from 1 Mbit/s to 10 Gbit/s. Besides key technical insights, relevant use cases and main features are described that were recently adopted by the IEEE 802.15.7r1 working group. Moreover, a channel model is introduced to enable assessment of technical proposals.
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On the benefits of cooperation via power control in OFDM-based visible light communication systems
(IEEE, 2014) Kashef, M.; Abdallah, M.; Qaraqe, K.; Haas, H.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, the performance of a visible light communication (VLC) network exploiting power control is considered. The achievable rate region of two VLC communication pairs is characterized. The system employs optical orthogonal frequency division multiplexing (O-OFDM) with power control performed at the transmitters. The optical signal clipping effect is taken into consideration which results from the physical limitations at the transmitters. Also, the system is constrained by the desired illumination power for each transmitter. We prove that the achievable rate region is defined as the union of two regions where the boundary of each of these regions can be obtained by a single variable optimization problem. Our numerical results show the effects of the system parameters including direct current (DC) bias, the desired illumination power, clipping noise and the relative positions of the receivers relative to the LED transmitters on the achievable rate region of the two users. We show the enhancement in the performance resulted from using power control compared to orthogonal resource allocation techniques.
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Outage performance of multi-hop hybrid FSO/RF communication systems
(IEEE, 2015) Kazemi, H.; Uysal, Murat; Touati, F.; Haas, H.; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, five scenarios are considered for the realization of a multi-hop hybrid free-space optical/radio frequency (FSO/RF) communication system with decode-and-forward (DF) relaying, and analytical outage probability expressions are derived. The scenarios have a different number of FSO and RF links. The aim is to identify an optimum scenario to effectively improve the end-to-end reliability of the multi-hop hybrid FSO/RF system. Outage performance is investigated for the scenarios under various weather conditions through numerical examples. It is identified that for a given link distance the end-to-end outage probability is minimized when using a hybrid FSO/RF link between every two successive nodes of the multi-hop system, and this requires the maximum number of FSO and RF links to be deployed.
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Single photon avalanche diode (SPAD) VLC system and application to downhole monitoring
(IEEE, 2014) Li, Y.; Videv, S.; Abdallah, M.; Qaraqe, K.; Uysal, Murat; Haas, H.; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, it is demonstrated for the first time that the problem of continuous downhole monitoring in the oil and gas industry is effectively addressed by the use of visible light communication (VLC). As a reliable, flexible and low-cost technique, VLC can fulfill a critical need of operators to maintain production efficiency and optimize gas well performance. The proposed VLC system makes use of a light emitting diode (LED) transmitter and a high sensitivity single photon detecting receiver referred to as single-photon avalanche diode (SPAD). The latter is instrumental in achieving long range communications, and the fact that ambient light is not present in a gas pipe is exploited. Specifically, the lack of ambient light enables high signal to noise ratio (SNR) at the receiver which operates in a photon counting mode. In this study, the bit error ratio (BER) performance of the system is simulated for a 4 kilometres long metal pipe. It is shown that the proposed system has superior power efficiency over conventional methods, which is important as it is assumed that the transmitter is battery operated. In addition, the theoretical BER performance is calculated and compared to the simulation results.