Effects of shadowing on non-directed LOS indoor infrared wireless systems with site diversity

We propose the multi base station (BS) system with site diversity to overcome the effects of shadowing. In the proposed system each BS transmits the same data at the same time. Thus, the symbol rate of the proposed system is almost the same as the bit rate when on-off keying (OOK) is employed, while that of the conventional repetitive transmission system is the number of BSs times as high as the bit rate. The receiver comprises an array of narrow field-of-view (FOV) detectors, like an angle diversity, and can collect signals from some BSs. Thus, the proposed system is robust against shadowing. We consider the down link transmission based on time-division multiple access (TDMA) and evaluate the effects of shadowing caused by pedestrians via theoretical analysis and computer simulation. We show that the proposed system can achieve higher signal-to-noise ratio (SNR) than the conventional system, and thus can decrease an outage probability that the receiver cannot achieve the required bit error rate (BER). We also show that the proposed system is robust against shadowing and can accommodate more calls.