Wireless Multicasting with Channel Uncertainty

We consider wireless multicasting where a source of common information is transmitted to a group of receivers over block fading channels. Communication between the transmitter and each of the receivers is implemented by specifying a minimum signal to noise plus interference ratio (SINR) threshold; if the threshold is met, the communication is successful at a corresponding rate, otherwise the communication fails. Such error controlled reception converts wireless channels into erasure channels, upon which forward error correction or retransmission is concatenated to achieve reliable communication. Assuming only channel distribution information at the transmitter, we derive the optimal SINR threshold given the transmit power constraint. We show, in the low transmit power regime, the optimal ratio between the SINR threshold and the transmit power is determined only by the channel distributions.