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 pathloss 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 to operate 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.