Wireless infrared in-house communications: how to achieve very high bit rates

While use of a power efficient signaling scheme appears to be effective in compensating for inherent high path-loss associated with pure diffuse infrared links, it begins to lose its effectiveness as data rate is increased. At very high data rates, intersymbol interference (ISI) can result in a very high and sometimes irreducible power penalty, preventing the system from operating at a low bit-error probability. In this paper, we investigate a link design employing a multi-beam transmitter in conjunction with a narrow field-of-view (FOV) direction diversity receiver. The design goal is to eliminate the effect of ISI, so that power efficient signaling schemes such as pulse-position modulation (PPM) can be employed at very high data rates. It is shown that an average bit-error rate (BER) not exceeding 10^-9 can be achieved within the link coverage area with more than 99% probability at bit rates up to a few hundreds of megabits per second, using transmitted power levels well below one Watt