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 characterization studies. We 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 we 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 MIMO technology in stairwell environments. Results reveal that 2-branch spatial diversity techniques offer signal gains over individual single channels in the range of 1.7 to 3.3 dB for LOS and 1.8 to 3.4 dB for NLOS for each of the three investigated frequencies, while 3-channel diversity combining appears to offer no significant additional gain over the 2-branch combinations. Furthermore, for NLOS cases the best fit statistical distribution channel models were found to change when spatial diversity was utilized; this highlights mitigated channel fading and increased signal reliability.