Capacities of unknown channels

Shannon's channel coding theoem treats the problem of communicating reliably over a channel when both the transmitter and the receiver are assumed to have full knowledge of the channel law so that selection of the codebook and the decoder structure can be optimized accordingly. However, there are a variety of situations in which either the codebook or the decoder must be selected without a complete knowledge of the law governing the channel over which transmission occurs. In subsequent work, Shannon and others have proposed several different channel models for such situations (e.g., the compound channel, the arbitrarily varying channel, etc.). Such channels can broadly be referred to as unknown channels.