Haas, Harald

Laurenson, David

Chen, Cheng

2017-11-06T15:56:33Z

2017-11-06T15:56:33Z

2017-07-10

There is a trend to move the frequency band for wireless transmission to ever higher frequencies in the radio frequency (RF) spectrum to fulfil the exponentially increasing demand in wireless communication capacity. Research work has gone into improving the spectral efficiency of wireless communication system to use the scarce and expensive resources in the most efficient way. However, to make wireless communication future-proof, it is essential to explore ways to transmit wirelessly outside the traditional RF spectrum. The visible light (VL) spectrum bandwidth is 1000 times wider than the entire 300 GHz RF spectrum and is, therefore, a viable alternative. Visible light communication (VLC) enables existing lighting infrastructures to provide not only illumination but also wireless communication. In conjunction with the concept of cell densification, a networked VLC system, light fidelity attocell (LAC) network, has been proposed to offer wide coverage and high speed wireless data transmission. In this study, many issues related to the downlink system in LAC networks have been investigated. When analysing the downlink performance of LAC networks, a large number of random channel samples are required for the empirical calculation of some system metrics, such as the signal-to-interference-plus-noise ratio (SINR). However, using state-of-the-art approaches to calculate the non-line-of-sight (NLoS) channel component leads to significant computational complexity and prolonged computation time. An analytical method has been presented in this thesis to efficiently calculate the NLoS channel impulse response (CIR) in VLC systems. The results show that the proposed method offers significant reduction in computation time compared to the state-of-the-art approaches. A comprehensive performance evaluation of the downlink system of LAC networks is carried out in this thesis. Based on the research results in the literature in the field of optical wireless communication (OWC), a system level framework for the downlink system in LAC networks is developed. By using this framework, the downlink performance subject to a large number of parameters is evaluated. Additionally, the effect of varying network size, cell deployment and key system parameters are investigated. The calculation of downlink SINR statistics, cell data rate and outage probability are considered and analysed. The results show that the downlink performance of LAC networks is promising in terms of achievable data rate per unit area compared to other state-of-the-art RF small-cell networks. It is found that co-channel interference (CCI) is a major source of signal impairment in the downlink of LAC network. In order to mitigate the influence of CCI on signal distortion in LAC networks, widely used interference mitigation techniques for RF cellular systems are borrowed and extensively investigated. In this study, fractional frequency reuse (FFR) is adapted to the downlink of LAC networks. The SINR statistics and the spectral efficiency in LAC downlink system with FFR schemes are evaluated. Results show that the FFR technique can greatly improve the performance of cell edge users and as well the overall spectral efficiency. Further performance improvements can be achieved by incorporating angular diversity transmitters (ADTs) with FFR and coordinated multi-point joint transmission (JT) techniques.

http://hdl.handle.net/1842/25420

en

The University of Edinburgh

C. Chen, D. A. Basnayaka, and H. Haas, “Downlink Performance of Optical Attocell Networks,” J. Lightw. Technol., vol. 34, pp. 137–156, Jan., 2016.

C. Chen, S. Videv, D. Tsonev, and H. Haas, “Fractional Frequency Reuse in DCO-OFDMBased Optical Attocell Networks,” J. Lightw. Technol., vol. 33, pp. 3986–4000, Oct., 2015.

C. Chen, D. Basnayaka and H. Haas, “Non-line-of-sight channel impulse response characterisation in visible light communications,” IEEE Int. Conf. on Commun., (Kuala Lumpur, Malaysia) pp. 1-6, May., 22–27 2016.

C. Chen, I.Muhammad, D. Tsonev, and H. Haas, “Analysis of Downlink Transmission in DCOOFDM- Based Optical Attocell Networks,” in Proc. of IEEE Global Commun. Conf., (Austin, TX), Dec., 8–12 2014.

C. Chen, D. Basnayaka, and H. Haas, “Downlink SINR Statistics in OFDM-Based Optical Attocell Networks with a Poisson Point Process Network Model,” in Proc. of IEEE Global Commun. Conf., (San Diego, CA), pp. 1–6, Dec., 6–10 2015.

C. Chen, N. Serafimovski, and H. Haas, “Fractional Frequency Reuse in Optical Wireless Cellular Networks,” in Proc. of the Int. Symp. on Personal, Indoor and Mobile Radio Commun., (London, United Kingdom), pp. 35943598, Sept., 8–11 2013.

C. Chen, D. Tsonev, and H. Haas, “Joint Transmission in Indoor Visible Light Communication Downlink Cellular Networks,” in IEEE Globecom Workshops, (Atlanta, GA), pp. 11271132, Dec., 9–13 2013.

light fidelity

visible light

visible light communication

cellular network

Downlink system characterisation in LiFi Attocell networks

Thesis or Dissertation

Doctoral

PhD Doctor of Philosophy