Covariance Matrix Basics

C is Hermitian: C = CH

Thermal Noise (regardless of architecture)

uncorrelated among spatial channels:

The covariance matrix characterizes how the interference is correlated

from channel to channel.

Narrowband directional jamming

correlated among spatial channels:

phase delays relative

to reference channel

signal amplitudes

in channels i and j

Noise + Multiple Uncorrelated Jammers:

rank = N

The Cjs have rank = 1; can’t invert!

if #J < N, need noise to get full rank

(if #J > N, don’t have enough nulls!)