Fading Broadcast Channel Capacities: III Scalar Fading Channels
In wireless broadcast multicast services (BMS), a standard assumption is that each receiver knows something about the channel h, usually referred as channel side information (CSI) or channel quality information (CQI). This is a pretty reasonable assumption when the channel is fading slowly inside the design boundary since there are pilot symbols available for the receiver to estimate CQI. Since the channel and transmitted signals are independent to each other, the ergodic capacity of the fading channel with receiver side information is given by C fading ( SNR, h ) = E log( 1 + |h| 2 SNR ) ≤ C AWGN ( E(|h| 2 ) SNR ). This means fading hurts or reduces the capacity in general if the transmitter knows nothing of the fading. This is different to the case that assumes the transmitter can estimate channel through CQI feedback and therefore can do some precoding on broadcast signals. Since a statistic analysis on a log(*) probability function is non-trivial, one approach is to apply the...
