Patent ID: 7443312

Claim:
A downhole communications system that comprises: a downhole transceiver to transmit uplink signals having a fixed modulation method via a first transmission mode, wherein the fixed modulation method is discrete multi-tone (DMT) modulation; and a surface transceiver coupled to the downhole transceiver, wherein the surface transceiver is configured to transmit a downlink signal to the downhole transceiver via a second transmission mode orthogonal to the first transmission mode, wherein the surface transceiver is further configured to transmit a proposed data rate to the downhole transceiver after an initial training phase, and wherein the surface transceiver is further configured to receive a downlink modulation method selection from the downhole transceiver in response to the transmission of a proposed data rate, the downlink modulation method being a selectable one of at least two alternative modulation methods including: quadrature amplitude modulation (QAM) without multiple carrier frequencies, and DMT modulation, and wherein the surface transceiver transmits using the selected downlink modulation method.