Multiple element antenna systems in an indoor environment

Multiple antenna systems have been proposed as an effective way to implement high data rate applications in wireless communications. They can potentially achieve very high capacities by decomposing the communications link into several sub-channels. Their efficiency depends on the propagation scenario between the transmitter and the receiver.; The original theoretical studies assume certain statistical properties for the propagation environment. We compare the theory with actual measurements of the physical channel. We study indoor propagation experimentally, and investigate the power and capacity behavior of the multiple antenna system in terms of antenna polarization, intra-element distance and array separation.; We first present measurements for a system with 12 transmitters and 15 receivers. The transmitter array was fixed in a hallway and the receiver was moved along the hallway and into the adjacent labs. When there was a strong line of sight component (hallway), the signal power was higher but there were fewer equivalent sub-channels. In the labs, the signal power suffered a significant loss. This affected the channel capacity and could not be compensated for by the increased number of sub-channels. We also investigate the propagation characteristics of the two electric field polarizations, and show that there is an advantage in using both.; The information theory based analysis treats the channel as a random process. However, we have deterministically analyzed the channel behavior in the hallway. Signal propagation in such an environment can be predicted with a simplified image model: the irregularities are ignored and the boundaries are considered infinite dielectric materials. A point source in the hallway corresponds to an infinite grid of images on a plane perpendicular to the hall. This model produces the same kind of behavior as that observed experimentally.; As a second deterministic theoretical approach, the hallway is modeled as a waveguide, where only specific propagation modes are allowed. In that case, the number of propagating modes limits the number of equivalent sub-channels. Since higher order modes decay much faster, the number of sub-channels also diminishes with distance.; These simplified models are qualitatively consistent with the channel behavior in the lab environment.