Performance of optical receivers using photodetectors with different fields of view in an indoor cellular communication system

This paper describes the use of an optical receiver which has photodiodes (PDs) with two different fields of view (2-FOV) in an indoor visible light communications (VLC) system. Data is transmitted using asymmetrically clipped optical OFDM (ACO-OFDM) from white light emitting diodes (LEDs) which are also used for illumination. A cellular configuration is considered where each transmitter transmits data to receivers within its cell. A minimum mean square error (MMSE) combiner is used in the receiver to separate the wanted signal from the interference. Results are calculated for the signal to interference plus noise ratio (SINR) as a function of the transmitter and receiver characteristics and the relative positions of the transmitters and receiver. It is shown that for most receiver positions the 2-FOV receiver outperforms a conventional receiver in which all of the PDs have the same FOV. It is also shown that increasing the number of PDs in the 2-FOV receiver from two to eight gives negligible improvement in performance. Bit error rate (BER) results are presented for a number of receiver positions showing that at some positions the 2-FOV receiver gives a significant improvement in performance but that at others no improvement is observed.