Cooperative communication is a promising technique that achieves spatial diversity without requiring multi-antenna receivers. In this paper, the authors consider the cooperative Amplify-and-Forward protocol and assume the channel realizations to be unknown. They study several pilot-based channel estimation strategies at the relay and the destination. The obtained maximum-likelihood estimators are evaluated for transmission over Rice-fading channels, in terms of channel estimation accuracy and error performance. An obvious way to achieve spatial diversity is by using communication terminals with multiple antennas.