| We consider the single-relay Ricean fading channels. We assume
that the receivers have perfect knowledge of the channel but
transmitters have no knowledge of the channels. We investigate the
statistics of the information rate by making use of a Hermitian
quadratic form in complex Gaussian random variables. The
cumulative distribution function (CDF) of the information rate is
obtained explicitly in a single integral. Some upper bounds and
lower bounds on the CDF of the information rate are also been
developed in closed forms. Based on the distribution of the
information rate, we obtain the optimal correlation coefficient of
the signals from source and relay in a quasi-static Ricean fading
environment, which minimizes the outage probability of the
information rates. When the product of the Ricean factors of the
channels from source and relay to destination is small, the
signals from source and relay should be independent for relatively
small transmission rates; when the product of the Ricean factors
of the channels from source and relay to destination is large, the
signals from source and relay should be correlated, and the
optimal correlation coefficient depends on the signal-to-noise
ratios (SNRs) of the three links in the single-relay channels, as
well as the rate threshold. |