Godkända
Robust On-Body MIMO Communications
Ali Muhammad Khan (Ja) och Salman Changazi (Ja)
Start
2008-11-04
Presentation
2009-05-15 13:15
Plats:
E:2311
Avslutat:
2009-05-29
Examensrapport:
(Kontakta handledare)
Sammanfattning
A human body has quite complex geometry and this results in on-body propagation characteristics being quite different as compared to off body environments. The fading of propagation channel around the human body has been studied relevant to specific antenna types, but in all those cases the effects of antennas are inherently included. If we can eliminate the effects of antennas, then we can focus on the propagation only channel characteristics. The purpose with this master thesis is to review all literature relating to on-body propagation in the initial step. After this, preliminary simulations were performed in the CST electromagnetic simulation software, in which we evaluated several 3-D body shapes, i.e., spherical, rectangular and cylindrical bodies. Different antennas, including monopoles, dipoles and wearable integrated antennas (WIAs), were simulated, and we verified some of interesting previous work done based on S21 parameter results. The body material was equivalent to that of muscle with conductivity of 1.81 S/m and relative permittivity of 53.58. After gaining the necessary insights, we designed and carried out a parametric simulation study (also in CST), in which a setup of four transmit antenna positions and three antenna orientations was used. The propagation behavior was visualized and analyzed around the body in three different regions using Matlab scripts written to process all data extracted from CST. Each transmit antenna position was at spacing of half a wavelength (lambda/2) from the adjacent position to ensure sufficient decorrelation at the transmit end. The transmit antenna positions were selected to be on front side of body while fictitious receivers (e.g., perfect electromagnetic field sensors) were assumed to be placed on different regions of the body. The correlation characteristics for various positions and orientations were extracted and analyzed. The visualization of the electric field around the body shows that when both the transmit and receive antennas are in line-of-sight (LOS) or semi-LOS, the field decays at an exponential rate with separation distance. In non-LOS (NLOS) situations, standing wave patterns were observed in the received fields. The fading of the NLOS conditions was determined to be lognormally distributed, which agrees with existing studies. Analysis of the diversity performance of the on-body propagation channel reveals that on-body antennas can be placed at a spacing of greater than lambda/4 at both the transmit and receive ends, in order to achieve good spatial diversity performance. This indicates that the fading characteristics in NLOS are favorable for robust on-body communications, even with the absence of scatterers in the surrounding environment.
Handledare: Buon Kiong Lau (EIT)
Examinator: Anders Karlsson (EIT)