Patent ID: 7672265

Claim:
A method for adjusting data modulation at a base station comprising: receiving data in data blocks from a higher layer ARQ mechanism at a physical layer transmitter for transmission; formatting the received data blocks into packets for transmission, the packets being smaller in size than the data blocks, and each packet having a forward error correction (FEC) encoding/data modulation; appending an error check sequence for each packet; providing a physical layer ARQ mechanism performing steps including: transmitting the packets using an orthogonal frequency division multiple access (OFDMA) air interface; storing the packets for retransmission in a buffer memory incorporated into the physical layer transmitter; monitoring a return channel for receipt of an acknowledgment for each packet that the packet has been received; limiting the number of retransmissions to an operator-defined integer value; clearing the buffer memory after the integer value is reached; retransmitting an original or selectively modified packet at the physical layer transmitter in response to a failure to receive a corresponding acknowledgement for a given packet; wherein the physical layer ARQ mechanism and physical layer transmitter operate transparently with respect to the higher layer ARQ mechanism; receiving and demodulating received packets at a physical layer receiver; receiving a corresponding acknowledgement for a given packet at the physical layer receiver, wherein a mechanism configured to receive the corresponding acknowledgement for the given packet operates transparently with respect to the higher layer ARQ mechanism; collecting retransmission statistics and adjusting the FEC encoding/data modulation using the collected statistics at an adaptive modulation and coding controller; wherein on a condition that the collected retransmission statistics indicate a low number of retransmissions, a higher capacity FEC encoding/data modulation scheme is selected and on a condition that the collected retransmission statistics indicate a high number of retransmissions, a lower capacity FEC encoding/data modulation scheme is selected; buffering, decoding, and detecting packet errors at a combiner/decoder; generating an acknowledgement for each received packet in an acknowledgement generator in response to that packet having an acceptable error rate; and selectively nulling subchannels from an OFDM frequency set for the retransmitting, wherein the use of a poor quality subchannel is precluded for a predetermined period and adding a previously nulled subchannel back into the OFDM frequency set where a retransmission rate or link quality indicates a high quality for the previously nulled subchannel.