TABLE OF CONTENTS In this chapter, we consider a MIMO system with n t transmit and n r receive antennas communicating through a frequency flat-fading channel. A codeword C = [ c 0 c T -1] of size n t T contained in the codebook 
(i.e. the set of all possible transmitted codewords) is transmitted over T symbol durations via n t transmit antennas. At the k th time instant, the transmitted and received signals are related by
| (5.1) |  |
where y k is the n r 1 received signal vector, H k is the n r n t channel matrix and n k is a n r 1 zero mean complex additive white Gaussian noise (AWGN) vector with 
. The parameter E s is the energy normalization factor, so that the ratio 
represents the SNR denoted as ?.
In order to match the normalization of the input covariance matrix Q introduced in Chapter 4 (Tr{ Q} = 1), we normalize the codeword average transmit power such that ? {Tr{ CC H}} = T. The quantity E s can thus be thought of as the total average energy available at the transmitter over a symbol duration. We should stress that alternative normalizations may be found in the literature.
As an example, the dependence in n t
