Capacity analysis in indoor wireless infrared communication using adaptive multiple subcarrier transmission

In the research field of indoor wireless IR communications state-of-the-art systems achieve high data rates through angular or spatial diversity. An innovative concept for performance improvement in IR system, based on signal processing and adaptive modulation, is proposed. This technique, known from DSL, and currently under discussion for RF wireless, seems also attractive for IR indoor systems, but needs to be examined under the specific conditions of the wireless optical channel (new problem statement). As first evaluation step, we perform capacity analysis to assess potential data rates in the multi-path IR channel present in most rooms. We derive the optimal power control for IR channels subject to an optical power constraint. Results show that, depending on the channel state, system capacity dramatically varies which can be efficiently exploited only by an adaptive system.