Haas, Harald

Safari, Majid

Kazemi, Hossein

Engineering and Physical Sciences Research Council (EPSRC)

2019-08-12T12:52:44Z

2019-08-12T12:52:44Z

2019-07-03

The backhaul of tens and hundreds of light fidelity (LiFi)-enabled luminaires constitutes a major challenge. The problem of backhauling for optical attocell networks has been approached by a number of wired solutions such as in-building power line communication (PLC), Ethernet and optical fiber. In this work, an alternative solution is proposed based on wireless optical communication in visible light (VL) and infrared (IR) bands. The proposed solution is thoroughly elaborated using a system level methodology. For a multi-user optical attocell network based on direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM) and decode-and-forward (DF) relaying, detailed modeling and analysis of signal-to-interference-plus- noise (SINR) and end-to-end sum rate are presented, taking into account the effects of inter-backhaul and backhaul-to-access interferences. Inspired by concepts developed for radio frequency (RF) cellular networks, full-reuse visible light (FR-VL) and in-band visible light (IB-VL) bandwidth allocation policies are proposed to realize backhauling in the VL band. The transmission power is opportunistically minimized to enhance the backhaul power efficiency. For a two-tier FR-VL network, there is a technological challenge due to the limited capacity of the bottleneck backhaul link. The IR band is employed to add an extra degree of freedom for the backhaul capacity. For the IR backhaul system, a power-bandwidth tradeoff formulation is presented and closed form analytical expressions are derived for the corresponding power control coefficients. The sum rate performance of the network is studied using extensive Monte Carlo simulations. In addition, the effect of imperfect alignment in backhaul links is studied by using Monte Carlo simulation techniques. The emission semi-angle of backhaul LEDs is identified as a determining factor for the network performance. With the assumption that the access and backhaul systems share the same propagation medium, a large semi-angle of backhaul LEDs results in a substantial degradation in performance especially under FR-VL backhauling. However, it is shown both theoretically and by simulations that by choosing a sufficiently small semi-angle value, the adverse effect of the backhaul interference is entirely eliminated. By employing a narrow light beam in the back-haul system, the application of wireless optical backhauling is extended to multi-tier optical attocell networks. As a result of multi-hop backhauling with a tree topology, new challenges arise concerning optimal scheduling of finite bandwidth and power resources of the bottleneck backhaul link, i.e., optimal bandwidth sharing and opportunistic power minimization. To tackle the former challenge, optimal user-based and cell-based scheduling algorithms are developed. The latter challenge is addressed by introducing novel adaptive power control (APC) and fixed power control (FPC) schemes. The proposed bandwidth scheduling policies and power control schemes are supported by an analysis of their corresponding power control coefficients. Furthermore, another possible application of wireless optical backhauling for indoor networks is in downlink base station (BS) cooperation. More specifically, novel cooperative transmission schemes of non-orthogonal DF (NDF) and joint transmission with DF (JDF) in conjunction with fractional frequency reuse (FFR) partitioning are proposed for an optical attocell downlink. Their performance gains over baseline scenarios are assessed using Monte Carlo simulations.

http://hdl.handle.net/1842/36029

en

The University of Edinburgh

H. Kazemi and H. Haas, “Downlink Cooperation with Fractional Frequency Reuse in DCOOFDMA Optical Attocell Networks,” in Proc. IEEE Int. Conf. Commun., (Kuala Lumpur, Malaysia), pp. 16, May 2016.

H. Kazemi, M. Safari, and H. Haas, “Spectral Efficient Cooperative Downlink Transmission Schemes for DCO-OFDM-Based Optical Attocell Networks,” in Proc. IEEE 84th Veh. Technol. Conf., (Montreal, Canada), pp. 16, Sep. 2016.

H. Kazemi, M. Safari, and H. Haas, “A Wireless Backhaul Solution Using Visible Light Communication for Indoor Li-Fi Attocell Networks,” in Proc. IEEE Int. Conf. Commun., (Paris, France), pp. 17, May 2017.

H. Kazemi, M. Safari, and H. Haas, “Bandwidth Scheduling and Power Control for Wireless Backhauling in Optical Attocell Networks,” in Proc. IEEE Global Commun. Conf., (Abu Dhabi, UAE), pp. 16, Dec. 2018.

H. Kazemi, M. Safari, and H. Haas, “AWireless Optical Backhaul Solution for Optical Attocell Networks,” IEEE Trans. Wireless Commun., vol. 18, no. 2, Feb. 2019.

light-fidelity

LiFi systems

backhaul

LiFi networks

optimal use of finite bandwidth

bandwidth sharing algorithms

Wireless optical backhauling for optical attocell networks

Thesis or Dissertation

Doctoral

PhD Doctor of Philosophy