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A method and system applicable within a mobile transmission system for adaptively allocating a downlink data rate to an access terminal to compensate for channel fading. In accordance with the method of the present invention a downlink data rate is selected in accordance with a determined signal-to-

A method and system applicable within a mobile transmission system for adaptively allocating a downlink data rate to an access terminal to compensate for channel fading. In accordance with the method of the present invention a downlink data rate is selected in accordance with a determined signal-to-noise level and an effective throughput, wherein the downlink data rate is associated with a specified signal-to-noise threshold to achieve a specified packet error rate. Next, a packet is transmitted to an access terminal at the selected downlink data rate. In response to successfully decoding the packet at the access terminal, the signal-to-noise threshold specified for the selected downlink data rate is decreased such that subsequent data rate selections are adaptively maximized. Responsive to a packet decoding error, the signal-to-noise threshold is abruptly increased to maintain the specified packet error rate.

대표청구항 ▼

What is claimed is: 1. A method applicable within a mobile communication system for adaptively allocating a downlink data rate to an access terminal to compensate for channel fading, said method comprising: selecting a downlink data rate in accordance with a determined signal-to-noise level and a d

What is claimed is: 1. A method applicable within a mobile communication system for adaptively allocating a downlink data rate to an access terminal to compensate for channel fading, said method comprising: selecting a downlink data rate in accordance with a determined signal-to-noise level and a determined effective throughput, wherein said downlink data rate is associated with a specified signal-to-noise threshold to achieve a specified packet error rate; receiving a packet by the access terminal at said selected downlink data rate; and responsive to successfully decoding said packet, decreasing the signal-to-noise threshold specified for said selected downlink data rate, wherein said determined effective throughput is computed in accordance with the relation: description="In-line Formulae" end="lead"r j=kj/ljdescription="In-line Formulae" end="tail" wherein rj represents the effective throughput, k j corresponds to an average successfully transmitted number of bits, and lj denotes the average number of slots used. 2. The method of claim 1, wherein said determined signal-to-noise level at said access terminal is a ratio of the signal strength of an allocated access terminal channel to the combined external signal strength plus thermal noise. 3. The method of claim 1, wherein said selecting a downlink data rate is preceded by determining a signal-to-noise level at said access terminal. 4. The method of claim 1, wherein said selecting a downlink data rate comprises: comparing said determined effective throughput with a plurality of effective throughput values, wherein each of said plurality of effective throughput values is associated with a corresponding downlink data rate and a signal-to-noise level; and selecting a highest downlink data rate corresponding to one of said plurality of effective throughput values that has a highest effective throughput where said associated signal-to-noise level does not exceed said determined signal-to-noise level. 5. The method of claim 1, further comprising: responsive to unsuccessfully decoding said packet, increasing the signal-to-noise threshold specified for said selected downlink data rate. 6. The method of claim 5, wherein said increasing the signal-to-noise threshold specified for said selected downlink data rate comprises: computing an increased signal-to-noise threshold specified for said selected downlink data rate in accordance with the relation: description="In-line Formulae" end="lead"T=T j+Δlocaldescription="In-line Formulae" end="tail" wherein T represents the increased signal-to-noise threshold associated with the selected downlink data rate, Tj represents the current signal-to-noise threshold value associated with the selected downlink data rate, and Δlocal represents a local data rate control delta value. 7. The method of claim 6, wherein said mobile communication system includes selectable data rate control sets in which each of said plurality of signal-to-noise threshold values is associated with a corresponding downlink data rate for said specified packet error rate, said method further comprising: responsive to unsuccessfully decoding said packet, increasing each of said plurality of signal-to-noise threshold values in accordance with the relation: description="In-line Formulae" end="lead"T=T i+Δglobaldescription="In-line Formulae" end="tail" wherein T represents the increased value for the ith signal-to-noise threshold value among said plurality of signal-to-noise threshold values, Ti represents current value for the ith signal-to-noise threshold value among said plurality of signal-to-noise threshold values, and Δglobal represents a global data rate control delta value. 8. The method of claim 1, wherein said decreasing the signal-to-noise threshold specified for said selected downlink data rate comprises: computing a decreased signal-to-noise threshold specified for said selected downlink data rate in accordance with the relation: T=T j-(PER*Δlocal) wherein T represents the decreased signal-to-noise threshold value associated with the selected downlink data rate, Tj represents the current signal-to-noise threshold value associated with the selected downlink data rate, PER represents said specified packet error rate, and Δlocal represents a local data rate control delta value. 9. The method of claim 8, wherein said mobile communication system includes selectable data rate control sets in which each of said plurality of signal-to-noise threshold values is associated with a corresponding downlink data rate for said specified packet error rate, said method further comprising: responsive to successfully decoding said packet, decreasing each of said plurality of signal-to-noise threshold values in accordance with the relation: description="In-line Formulae" end="lead"T=T i-(PER*Δglobal)description="In-line Formulae" end="tail" wherein T represents the decreased signal-to-noise threshold, Ti represents the ith signal-to-noise threshold value among said plurality of signal-to-noise threshold values, PER represents said specified packet error rate, and Δglobal represents a global data rate control delta value. 10. A mobile communication system for adaptively allocating a downlink data rate to an access terminal to compensate for channel fading, said mobile communication system comprising: a processor to select a downlink data rate in accordance with a determined signal-to-noise level and a determined effective throughput, wherein said downlink data rate is associated with a specified signal-to-noise threshold to achieve a specified packet error rate; an air-interface transceiver to transmit a packet to an access terminal at said selected downlink data rate; and the processor responsive to successfully decoding of said packet for decreasing the signal-to-noise threshold specified for said selected downlink data rate, wherein said determined effective throughput is computed in accordance with the relation: description="In-line Formulae" end="lead"r j=Kj/ljdescription="In-line Formulae" end="tail" wherein ri represents the effective throughput, k j corresponds to an average successfully transmitted number of bits, and lj denotes the average number of slots used. 11. The mobile communication system of claim 10, wherein said determined signal-to-noise level at said access terminal is a ratio of the signal strength of a pilot channel to the combined external signal strength plus thermal noise. 12. The mobile communication system of claim 10, further comprising signal detection means for determining a signal-to-noise level at said access terminal. 13. The mobile communication system of claim 10, wherein said processor selects the downlink data rate by comparing said determined effective throughput with a plurality of effective throughput values, wherein each of said plurality of effective throughput values is associated with a downlink data rate and a signal-to-noise level; and selecting a highest downlink data rate corresponding to one of said plurality of effective throughput values that has a highest effective throughput where said associated signal-to-noise level does not exceed said determined signal-to-noise level. 14. The mobile communication system of claim 10, wherein the processor is responsive to unsuccessfully decoding of said packet for increasing the signal-to-noise threshold specified for said selected downlink data rate. 15. The mobile communication system of claim 14, wherein said processor increases the signal-to-noise threshold specified for said selected downlink data rate by computing an increased signal-to-noise threshold specified for said selected downlink data rate in accordance with the relation: description="In-line Formulae" end="lead"T=T j+Δlocaldescription="In-line Formulae" end="tail" wherein T represents the increased signal-to-noise threshold associated with the selected downlink data rate, Tj represents the current signal-to-noise threshold value associated with the selected downlink data rate, and Δlocal represents a local data rate control delta value. 16. The mobile communication system of claim 15, further comprising memory containing selectable data rate control sets in which each of said plurality of signal-to-noise threshold values is associated with a corresponding downlink data rate for said specified packet error rate, wherein the processor is responsive to unsuccessfully decoding of said packet by increasing each of said plurality of signal-to-noise threshold values in accordance with the relation: description="In-line Formulae" end="lead"T=T i+Δglobaldescription="In-line Formulae" end="tail" wherein T represents the increased value for the ith signal-to-noise threshold value among said plurality of signal-to-noise threshold values, Ti represents current value for the ith signal-to-noise threshold value among said plurality of signal-to-noise threshold values, and Δglobal represents a global data rate control delta value. 17. The mobile communication system of claim 10, wherein said processor decreases the signal-to-noise threshold specified for said selected downlink data rate by computing a decreased signal-to-noise threshold specified for said selected downlink data rate in accordance with the relation: description="In-line Formulae" end="lead"T=T j-(PER*Δlocal)description="In-line Formulae" end="tail" wherein T represents the decreased signal-to-noise threshold value associated with the selected downlink data rate, Tj represents the current signal-to-noise threshold value associated with the selected downlink data rate, PER represents said specified packet error rate, and Δlocal represents a local data rate control delta value. 18. The mobile communication system of claim 17, further comprising memory for storing selectable data rate control sets in which each of said plurality of signal-to-noise threshold values is associated with a corresponding downlink data rate for said specified packet error rate wherein the processor is responsive to successfully decoding of said packet by decreasing each of said plurality of signal-to-noise threshold values in accordance with the relation: description="In-line Formulae" end="lead"T=T j-(PER*Δglobal)description="In-line Formulae" end="tail" wherein T represents the decreased signal-to-noise threshold, Ti represents the ith signal-to-noise threshold value among said plurality of signal-to-noise threshold values, PER represents said specified packet error rate, and Δglobal represents a global data rate control delta value.