Multiple antenna channel characterisation for wearable devices in an indoor stairwell environment

Any building with more than one floor will have stairwells of some form, yet this area is often neglected in channel characterisation studies. The authors present fading channel models and examine attainable spatial diversity gains at 90% signal reliability for an off-body multiple-antenna system at frequencies of 3, 4, and 5 GHz in an indoor stairwell. Additionally, they investigate received power, mutual coupling and channel cross-correlation, signal combining modelling, and antenna spatial diversity; the authors believe this is a valuable advancement beyond current knowledge to understand wearable multipleinput multiple-output technology in stairwell environments. Results reveal that two-branch spatial diversity techniques offer signal gains over individual single channels in the range of 1.7-3.3 dB for line of sight (LOS) and 1.8-3.4 dB for non-LOS (NLOS) for each of the three investigated frequencies, while three-channel diversity combining appears to offer no significant additional gain over the two-branch combinations. Furthermore, for NLOS cases the best-fit statistical distribution channel models were found to change when spatial diversity was utilised; this highlights mitigated channel fading and increased signal reliability.