Antenna-Generic Multi-Mode Channels

This paper explains what is antenna-generic multi-mode channel, why we need it and how to obtain it. This paper is summarized from our measurement-based studies where we establish an analytical model and analyze the statistical behaviors of multi-mode channels in spherical vector wave (SVW) domain. The multi-mode channels represent radio wave propagation in the form of SVW mode coupling between link ends. The multi-mode channels do not rely on particular realizations of antennas at link ends, since any transmitting, receiving, and scattering fields associated with an antenna can be modeled as a weighted sum of SVW modes where different antennas have different complex-valued mode weights. The multi-mode channel can be converted from plane wave channel model parameters that we always extract from measurable channel transfer functions, and can also be measured directly with dedicated array design at link ends. The multi-mode channels can be used directly to compute the spatial degree-of-freedom which poses an upper-limit of the antenna channels when specific antennas are deployed, as well as the intrinsic channel capacity that depends on the propagation condition and antenna's electric size (only). The multi-mode channel behaviors in an urban microcellular scenario have been investigated as to power imbalance, small-scale fading, auto- and cross-correlations. These behaviors provide invaluable insights into the design of antenna systems tailored to a specific propagation environment. Antenna systems at link ends should be devised such that the multi-mode channels with higher power, larger coherent distance and smaller cross-correlation be excited to fully exploit the degree of freedom of propagation channel.