Channel modeling for millimeter wave MIMO

The large amounts of bandwidth available in the millimeter (mm) wave band enable multiGigabit wireless networks with applications ranging from indoor multimedia networking to outdoor backhaul for picocellular networks. Carrier wavelengths in this band are an order of magnitude smaller than those for existing cellular and WiFi systems, resulting in a drastically different propagation geometry. Omnidirectional transmission is essentially infeasible because of the increased propagation loss at smaller wavelengths; on the other hand, highly directive transmission and reception with electronically steerable beams can be achieved using compact antenna arrays. Thus, in contrast to the rich scattering environment at lower carrier frequencies, a small number of paths are dominant for directional mm wave links. The small wavelength also implies that spatial multiplexing gains can be obtained even in Line of Sight (LoS), or more generally, sparse scattering, environments with antennas with moderate separation. In this paper, we examine the consequences of these observations for two scenarios. The first is a lamppost-based outdoor deployment, where we model fading due to ground and wall reflections, and examine MIMO techniques for combating fading. The second is for spatial multiplexing for an indoor link, where we model the number of eigenmodes as a function of form factor, and examine the effect of blockage.