Adaptive coding and modulation (ACM) transceiver system

A method for transmitting signals in an adaptive coding and modulation (ACM) transmission system, the method comprising:

• Transmitting, by an ACM transceiver, a first transmit signal in a first modulation and coding scheme (MODCOD) of a plurality of MODCODS;
• Receiving, by the ACM transceiver, a first return signal corresponding to the first transmit signal;
• Receiving, by the ACM transceiver, a reported signal-to-noise ratio (SNR) corresponding to the first transmit signal via the first return signal;
• comparing the reported SNR with a plurality of adaptive SNR thresholds in an adaptive ACM table, each of the plurality of adaptive SNR thresholds being associated with a respective one of the plurality of MODCODS, to determine one of the plurality of MODCODS for transmission of a second transmit signal;
• transmitting, by the ACM transceiver, the second transmit signal via the determined one of the plurality of MODCODS;
• receiving, by the ACM transceiver, a second return signal corresponding to the second transmit signal;
• and
• updating the adaptive ACM table based on the reported SNR delivered by the second return signal comprising updating a maximum SNR difference value for each of the plurality of MODCODS in an ACM tracking table, the maximum SNR difference value corresponding to a difference between the reported SNR associated with a first transmit signal and the reported SNR associated with a second transmit signal for the respective one of the plurality of MODCODS.

A troposcatter communication system comprising an adaptive coding and modulation (ACM) transmission system, an ACM transceiver system comprising an ACM controller configured to receive a reported signal-to-noise ratio (SNR) delivered by each of a plurality of return signals corresponding to a respective plurality of transmit signals that were each sequentially previously transmitted from the ACM transceiver system in a respective one of a plurality of modulation and coding schemes (MODCODS), the reported SNR delivered by a given one of the plurality of return signals corresponding to the respective one of the plurality of transmit signals, the ACM controller comprising:

• an ACM reference table comprising a nominal SNR threshold associated with each of the plurality of MODCODS;
• an ACM tracking table comprising a maximum SNR difference value corresponding to a difference between the reported SNR associated with one of the plurality of transmit signals and the reported SNR of another one of the plurality of transmit signals for each of the plurality of MODCODS;
• and
• an adaptive ACM table comprising an adaptive SNR threshold associated with each of the plurality of MODCODS, the adaptive SNR threshold comprising a sum of the nominal SNR threshold and the maximum SNR difference value for each of the plurality of MODCODS;
• wherein the ACM controller is configured to compare the reported SNR with the adaptive SNR threshold of each of the plurality of MODCODS to select one of the plurality of MODCODS for transmission of a next transmit signal.