Method for physical layer automatic repeat request for a base station
First Claim
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1. 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.
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Abstract
A physical automatic repeat request method implemented by a base station having a transmitter and a receiver. A physical layer, at the transmitter receives data and formats the received data into packets having a particular encoding/data modulation. The physical layer transmit the packets and retransmits packets upon failure to receive a corresponding acknowledgment for a given packet. An adaptive modulation and coding controller in the transmitter collects retransmission statistics and adjusts the particular encoding/data modulations using the collected statistics.
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Citations
5 Claims
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1. A method for adjusting data modulation at a base station comprising:
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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. - View Dependent Claims (2, 3, 4, 5)
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Specification