Plots of cumulative probability distribution versus channel capacity in a 2 × 2 MIMO system with different normalized distances. 0.1λ is the distance between two dipoles Tx coupling indicates that the transmitting dipoles are 0.1λ apart but the receiving dipoles are independent; Tx–Rx coupling signifies that both the transmitting dipole distance and receiving dipole distance are 0.1λ. The others have the same meanings as shown elsewhere. In addition, i.i.d. with TR means independent 2 × 2 MIMO channel with TR, and i.i.d. without TR refers to independent 2 × 2 MIMO channel without TR.