Capacity of multi-antenna array systems for HVAC ducts

Multi-element antenna arrays at both transmitter and receiver systems have emerged as a new technique for wireless communication systems in rich multipath environments. HVAC ducts, viewed as over-moded waveguide network systems at RF frequencies, have the multipath richness through various propagating modes and reflections within the system. This paper studies multiple-input multiple-output (MIMO) systems for HVAC ducts. Computations based on measured channel responses of a 6×6 MIMO system in 0.3 m diameter HVAC ducts in the 2.4 GHz ISM band demonstrate a five-fold increase in mean capacity over single antenna systems for an SNR of 30 dB.