Analysis of downlink transmission in DCO-OFDM-based optical attocell networks

In this paper, an indoor visible light communication (VLC) cellular network, referred to as an optical attocell network, is analysed at system level. A line-of-sight (LOS) ray-tracing model is used to characterise the light propagation and its effect on the performance of an intensity modulation (IM) and direct detection (DD) communication system. Orthogonal frequency division multiple access (OFDMA) based on direct-current optical orthogonal frequency division multiplexing (DCO-OFDM) is used as a multi-user access scheme. The signal-to-interference-plus-noise ratio (SINR) for a user with a random location in an optical attocell is studied. An analytical approach to calculate the statistics of the SINR is presented and verified by Monte Carlo simulations. Moreover, average spectral efficiency is also studied in order to estimate the downlink wireless capacity of the optical attocell network. The spectral efficiency of the system has been found to be strongly dependent on the radius of an optical attocell and on the half-power semi-angle of the light transmission profile. Guidelines for the configuration of the relevant attocell parameters are provided. An optical attocell with an average spectral efficiency of 5.9 bits/s/Hz is demonstrated for an appropriate set of attocell parameters.