Indoor On-body to Off-body Fading Mitigation Using Pattern Diversity

• Published in: Wireless personal communications Vol. 90; no. 1; pp. 109 - 120
• Main Authors: Chamaani, Somayyeh, Mokhtarani, Ali
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.09.2016; Springer Nature B.V
• Subjects: Antenna arrays; Beam switching; Channels; Communications Engineering; Computer Communication Networks; Engineering; Fading; Microstrip antennas; Networks; Patch antennas; Probability distribution functions; Remote monitoring; Shadows; Signal,Image and Speech Processing; Walking; Fading; Pattern diversity; Switched multi-beam antenna; Body shadowing; Body area communications
• ISSN: 0929-6212; 1572-834X
• DOI: 10.1007/s11277-016-3334-5

Establishing a reliable communication link between on-body and off-body is a challenge in remote patient monitoring. Fading is very common in body area communications due to multi-path, body shadowing and inherent channel dynamicity. This paper investigates effectiveness of pattern diversity in the fading mitigation. An on-body switched multi-beam array implemented by a 4 by 4 butler matrix is used to fulfill the pattern diversity at 2.4 GHz industrial, scientific and medical band. The multi-beam array performance is compared with a single microstrip patch antenna. The tests are done with two different subjects carrying the antennas in various random scenarios including walking, sitting and lying. It is observed that the generalized Gamma distribution which has been proposed for channels including both of shadowing and multi-path effects, properly describes most of the off-body scenarios. The fitting results show that the fading severity parameter of the generalized Gamma is reduced in the beam switching method. In addition, second order statistics including level crossing rate and average fade duration (AFD) are extracted from measurements. It is shown that the beam switching reduces the AFD. Furthermore, outage probability is reduced for all scenarios where 2–5.1 dB diversity gain is achieved for different scenarios. The results show that the pattern diversity is a simple method to alleviate the fading of the dynamic off-body channel.