Analysis of Optimal Placement of LED Arrays for Visible Light Communication

In this paper the optimum placement of light emitting diode (LED) arrays is investigated for indoor visible light communication (VLC) subject to maximization of average area spectral efficiency (ASE). Design parameters of LED array such as the distance between two neighboring LEDs and the precise location on the ceiling of the LED arrays can be obtained by solving an optimization problem. The formulated optimization problem is applied to a room of 2.5m×5m×3m dimension where two square LED arrays provide the required illumination. Due to the complexity of the optimization problem, a numerical optimization procedure is employed and the maximization is carried out by using algorithms from Matlab optimization toolbox. The results show that when the users employ a wide field of view (FOV) detector (e.g. 85°) the optimum solution involves placing the two LED arrays close to the opposite walls in the direction of the highest dimension of the room. It is also shown that when employing receivers with a smaller FOV (45°) the optimum solution allows the two LED arrays to be placed farther away from the opposite walls in the room. The average ASE achieved in this case is twice as high as the average ASE obtained when employing receivers with 85° FOV. Moreover, when the illumination constraint is also fulfilled, the ASE performance degradation can be quite significant (e.g. 33% for detectors with 85° FOV) as compared with the case where the VLC system is used only for communication purposes.