Adaptive data rate control for mobile data transfer for high throughput and guaranteed error rate

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:

r j =k j /l j

wherein r j represents the effective throughput, k j corresponds to an average successfully transmitted number of bits, and l j 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:

T=T j +Δ local

wherein T represents the increased signal-to-noise threshold associated with the selected downlink data rate, T j represents the current signal-to-noise threshold value associated with the selected downlink data rate, and Δ local 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:

T=T i +Δ global

wherein T represents the increased value for the i th signal-to-noise threshold value among said plurality of signal-to-noise threshold values, T i represents current value for the i th signal-to-noise threshold value among said plurality of signal-to-noise threshold values, and Δ global 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*Δ local )

wherein T represents the decreased signal-to-noise threshold value associated with the selected downlink data rate, T j represents the current signal-to-noise threshold value associated with the selected downlink data rate, PER represents said specified packet error rate, and Δ local 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:

T=T i −( PER*Δ global )

wherein T represents the decreased signal-to-noise threshold, T i represents the i th signal-to-noise threshold value among said plurality of signal-to-noise threshold values, PER represents said specified packet error rate, and Δ global 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:

r j =K j /l j

wherein r i represents the effective throughput, k j corresponds to an average successfully transmitted number of bits, and l j 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:

T=T j +Δ local

wherein T represents the increased signal-to-noise threshold associated with the selected downlink data rate, T j represents the current signal-to-noise threshold value associated with the selected downlink data rate, and Δ local 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:

T=T i +Δ global

wherein T represents the increased value for the i th signal-to-noise threshold value among said plurality of signal-to-noise threshold values, T i represents current value for the i th signal-to-noise threshold value among said plurality of signal-to-noise threshold values, and Δ global 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:

T=T j −( PER*Δ local )

wherein T represents the decreased signal-to-noise threshold value associated with the selected downlink data rate, T j represents the current signal-to-noise threshold value associated with the selected downlink data rate, PER represents said specified packet error rate, and Δ local 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:

T=T j −( PER*Δ global )

wherein T represents the decreased signal-to-noise threshold, T i represents the i th signal-to-noise threshold value among said plurality of signal-to-noise threshold values, PER represents said specified packet error rate, and Δ global represents a global data rate control delta value.