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By virtue of one embodiment of the present invention, dynamic signal to noise ratio measurements made on received signals are used to identify degraded segments of a channel. The degraded segments are then no longer used for transmitting payload data. In the context of an orthogonal frequency divisi

By virtue of one embodiment of the present invention, dynamic signal to noise ratio measurements made on received signals are used to identify degraded segments of a channel. The degraded segments are then no longer used for transmitting payload data. In the context of an orthogonal frequency division multiplexing (OFDM) communication system, degraded OFDM subchannels, as determined on a real-time basis, are not used to transmit payload data. In an OFDM network where access is shared in the time domain among multiple transmitters and a single allocable time slot includes an integer number of OFDM bursts, the medium access control layer adjusts packet length, and therefore the amount of data to be included in a given slot, in response to the fluctuating number of available subchannels.

대표청구항 ▼

The invention claimed is: 1. In a point to multipoint communication network, a method comprising: at an access point device in the network, receiving a series of orthogonal frequency division multiplexed (OFDM) bursts transmitted from a subscriber unit; at the access point device, monitoring recept

The invention claimed is: 1. In a point to multipoint communication network, a method comprising: at an access point device in the network, receiving a series of orthogonal frequency division multiplexed (OFDM) bursts transmitted from a subscriber unit; at the access point device, monitoring reception quality in a plurality of OFDM subchannels, wherein monitoring comprises measuring an average signal-to-noise ratio for each of a plurality of groups of subchannels for the OFDM bursts, applying a weight to the average based on time of reception such that average signal-to-noise measurements for more recently received OFDM bursts are given relatively higher weight than average signal-to-noise measurements for older OFDM bursts; at the access point device, designating a selected subchannel as below a quality threshold based on the signal-to-noise ratio measured in the plurality of subchannels; and generating a message at the access point device to be sent to the subscriber unit, the message configured to instruct the subscriber unit to not transmit payload data in said selected subchannel. 2. The method of claim 1 further comprising: receiving an acknowledgment from said subscriber unit that was generated in response to said instructing. 3. The method of claim 2, and further comprising, at the access point device, updating parameters associated with processing of transmissions received from the subscriber unit upon receiving the acknowledgment, wherein updating comprises updating one or more of: a deinterleaving function to reflect one or more selected subchannels that the subscriber unit does not transmit in, a media access control (MAC) layer processing function according to a new upstream packet size based on the one or more selected subchannels, and a decoding function according to a change in codeword size based on the one or more selected subchannels. 4. The method of claim 1, wherein receiving comprises receiving OFDM bursts of a wireless transmission from the subscriber unit. 5. In a point to multipoint communication network, a method for operating a subscriber unit, said method comprising: at a subscriber unit in the network, receiving an instruction message from an access point device in the network, said instruction message including information identifying one or more selected orthogonal frequency division multiplexed (OFDM) subchannels to be left unused in future transmissions to the access point device; and at the subscriber unit, updating parameters associated with transmissions of OFDM bursts to be sent based on the instruction message, wherein updating comprises updating one or more of: an interleaving function based on one or more selected subchannels that are not used, a media access control (MAC) layer processing function according to a new upstream packet size based on the one or more selected subchannels that are not used, and an encoding function according to a change in codeword size based on the one or more selected subchannels that are not used; at the subscriber unit, transmitting an OFDM burst with subchannels left unused for data in accordance with said instruction message and based on said updating. 6. The method of claim 5 further comprising: sending to said access point device a message acknowledging said instruction message. 7. The method of claim 5, wherein updating comprises updating parameter associated with wireless transmissions of OFDM burst to be sent by the subscriber unit. 8. In a point to multipoint communication network, an apparatus for operating a central access point, said apparatus comprising: a receiver that is configured to monitor reception quality in a plurality of orthogonal frequency division multiplexed (OFDM) subchannels, wherein the receiver comprises a converter that is configured to convert a series of time domain bursts received from a subscriber unit to frequency domain OFDM bursts and a signal-to-noise ratio measurement block that is configured to measure an average signal-to-noise ratio for each of a plurality of groups of subchannels for the OFDM bursts, apply a weight to the average based on time of reception such that average signal-to-noise measurements for more recently received OFDM bursts are given a relatively higher weight than average signal-to-noise measurements for older OFDM bursts; and a control processor that is configured to analyze the signal-to-noise ratio in the plurality of subchannels, to designate a selected subchannel as below a quality threshold based on the signal-to-noise measurements made by the signal-to noise measurement block and to generate a message to be sent to the subscriber unit, the message being configured to instruct the subscriber unit to not transmit payload data in said selected subchannel. 9. The apparatus of claim 8, wherein said control processor is configured to generate the message that identifies the selected subchannel and to receive an acknowledgement to message. 10. The apparatus of claim 9, wherein the control processor is configured to update parameters associated with processing of transmissions received from the subscriber unit upon receiving the acknowledgment, including updating one or more of: a deinterleaving function to reflect one or more selected subchannels that the subscriber unit does not transmit in, a media access control (MAC) layer processing function according to a new upstream packet size based on the one or more selected subchannels, and a decoding function according to a change in codeword size based on the one or more selected subchannels. 11. The apparatus of claim 8, wherein the control processor is configured to monitor OFDM bursts transmitted by subscriber units in a particular geographical grouping of subscriber units within a network so as to make decisions concerning subchannels to be designated for no transmissions with respect to all subscriber units within the particular geographical grouping. 12. The apparatus of claim 8, wherein the receiver is configured to monitor reception quality in a plurality of OFDM subchannels associated with a received wireless transmission. 13. In a point to multipoint communication network, an apparatus for operating a subscriber unit, said apparatus comprising: a control processor that is configured to process an instruction message received from an access point, said instruction message including information identifying one or more selected orthogonal frequency division multiplexed (OFDM) subchannels to be left unused in future transmissions, wherein the control processor is configured to update parameters associated with transmissions of OFDM bursts by updating one or more of: an interleaving function based on one or more selected subchannels that are not used, a media access control (MAC) layer processing function according to a new upstream packet size based on the one or more selected subchannels that are not used, and an encoding function according to a change in codeword size based on the one or more selected subchannels that are not used; and an OFDM transmitter that transmits an OFDM burst with one or more subchannels unused for transmitting payload data in accordance with said instruction message. 14. The apparatus of claim 13, wherein said control processor is configured to generate an acknowledgment message to be sent to the access point, wherein the acknowledgement message is configured to acknowledge said instruction message. 15. The apparatus of claim 13, wherein the OFDM transmitter is configured to wirelessly transmit the OFDM burst. 16. A non-transitory computer-readable storage medium storing instructions that, when executed by a processor, cause the processor to: measure an average signal-to-noise ratio for each of a plurality of groups of subchannels for a plurality of orthogonal frequency division multiplexed (OFDM) subchannels of transmission bursts received at an access point device from a subscriber unit, apply a weight to the average based on time of reception such that average signal-to-noise measurements for more recently received OFDM bursts are given a relatively higher weight than average signal-to-noise measurements for older OFDM bursts; monitor noise and/or interference conditions within the plurality of subchannels based on the signal-to-noise ratio measured in the plurality of subchannels; identify subchannels impacted by noise and/or interference conditions by designating one or more selected subchannels that fall below a quality threshold based on the signal-to-noise ratio measured in the plurality of subchannels; and generate a message to be sent to the subscriber unit, the message configured to instruct the subscriber unit to not include payload data in said one or more selected subchannels. 17. A non-transitory computer-readable storage medium of claim 16, and further comprising instructions that cause the processor to monitor, identify and generate a message with respect to received OFDM transmissions made by subscriber units in a particular geographical grouping of subscriber units within a network so as to make decisions concerning subchannels to be designated not to include payload data with respect to all subscriber units within the particular geographical grouping. 18. A non-transitory computer-readable storage medium of claim 16, wherein the instructions that cause the processor to measure comprise instructions that cause the processor to measure signal-to-noise ratio for a plurality of OFDM subchannels of received wireless transmission bursts. 19. A non-transitory computer-readable storage medium storing instructions that, when executed by a processor, cause the processor to: recover from a message received at a subscriber unit from an access point device; identify one or more subchannels impacted by noise and/or interference conditions, said one or more subchannels being determined based on real-time signal measurements; update parameters associated with orthogonal frequency division multiplexed (OFDM) transmissions, by updating one or more of: an interleaving function based on one or more selected subchannels that are not used, a media access control (MAC) layer processing function according to a new upstream packet size based on the one or more selected subchannels that are not used, and an encoding function according to a change in codeword size based on the one or more selected subchannels that are not used; and generate an OFDM burst to be transmitted to the access point device, which burst does not employ one or more selected subchannels that are not used for carrying payload data. 20. A non-transitory computer-readable storage medium of claim 19, wherein the instructions that cause the processor to generate the OFDM bursts comprises instructions to generate the OFDM bursts for wireless transmission to the access point device.