Protocols for adapting the rate of an error-control code in direct-sequence or frequency-hop spread-spectrum packet radio networks are evaluated for static channels and channels with time-varying parameters that are modeled as finite-state Markov chains. The performance of our protocols is compared with the performance of an ideal protocol that has perfect channelstate information and employs a set of capacity-achieving codes of the same rates as the codes available to our protocols. The

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... ics used by our protocols for adaptation are derived from the demodulator and decoder in the receiving radio, and they are provided to the transmitting radio by a few bits that are included in each acknowledgment packet.