Adaptive data rate control for mobile data transfer

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, wherein said downlink data rate is associated with a specified signal-to-noise threshold value to achieve a specified packet error rate, wherein selecting the downlink data rate compnses:

comparing said determined signal-to-noise level with a plurality of signal-to-noise threshold values, wherein each of said plurality of signal-to-noise threshold values is associated with a downlink data rate; and

selecting a highest downlink data rate corresponding to two or more of said plurality of signal-to-noise threshold values that do not exceed said determined signal-to-noise level, 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, and wherein selecting the highest downlink rate comprises:

comparing the relative values of said two or more signal-to-noise threshold values; and

selecting a data rate control set corresponding to the lowest among said two or more signal-to-noise threshold values;

receiving a packet by the access terminal at said selected downlink data rate;

responsive to successfully decoding said packet, decreasing the signal-to-noise threshold value specified for said selected downlink data rate; and

responsive to unsuccessfully decoding said packet, increasing the signal-to-noise threshold value specified for said selected downlink data rate, said increasing the signal-to noise threshold value specified for said selected downlink data rate comprising:

computing an increased signal-to-noise threshold value 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 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, and Δ local represents a local data rate control delta value.

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.

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 , 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.

5. A method applicable within a mobile communication system for adaptively allocating a downlink data rate to a mobile access terminal to compensate for channel fading, said method comprising:

selecting, by the mobile access terminal, a downlink data rate in accordance with a determined signal-to-noise level, wherein said downlink data rate is associated with a specified signal-to-noise threshold value to achieve a specified packet error rate;

receiving a packet by the mobile access terminal at said selected downlink data rate; and

responsive to successfully decoding said packet, the mobile access terminal decreasing the signal-to-noise threshold value specified for said selected downlink data rate, said decreasing the signal-to-noise threshold value specified for said selected downlink data rate comprising:

computing a decreased signal-to-noise threshold value 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.

6. The method of claim 5 , 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 local )

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.

7. The method of claim 5 , further comprising responsive to unsuccessfully decoding the packet, increasing the signal-to-noise threshold value specified for the selected downlink data rate.

8. 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:

processing means for selecting a downlink data rate in accordance with a determined signal-to-noise level, wherein said downlink data rate is associated with a specified signal-to-noise threshold value to achieve a specified packet error rate, wherein said processing means for selecting a downlink data rate comprises:

processing means for comparing said determined signal-to-noise level with a plurality of signal-to-noise threshold values, wherein each of said plurality of signal-to-noise threshold values is associated with a downlink data rate; and

processing means for selecting a highest downlink data rate corresponding to two or more of said plurality of signal-to-noise threshold values that do not exceed said determined signal-to-noise level;

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 said processing means for selecting the highest downlink data rate comprises:

processing means for comparing the relative values of said two or more signal-to-noise threshold values; and

processing means for selecting a data rate control set corresponding to the lowest among said two or more signal-to-noise threshold values;

air-interface transmission means for transmitting a packet to an access terminal at said selected downlink data rate;

processing means responsive to successfully decoding said packet for decreasing the signal-to-noise threshold specified for said selected downlink data rate; and

processing means responsive to unsuccessfully decoding said packet for increasing the signal-to-noise threshold specified for said selected downlink data rate, said processing means for increasing the signal-to-noise threshold specified for said selected downlink data rate comprising:

processing means for 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.

9. The mobile communication system of claim 8 , 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.

10. The mobile communication system of claim 8 , further comprising signal detection and processing means for determining a signal-to-noise level at each access terminal.

11. The mobile communication system of claim 8 , further comprising:

processing means responsive to unsuccessfully decoding said packet for 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.

12. A mobile access terminal comprising:

processor to select a downlink data rate in accordance with a determined signal-to-noise level, wherein said downlink data rate is associated with a specified signal-to-noise threshold value to achieve a specified packet error rate;

the processor to send a data rate request containing the selected downlink data rate to an access node over an uplink channel;

air-interface transceiver to receive a packet from the access node at said selected downlink data rate; and

the processor responsive to successfully decoding said packet to decrease the signal-to-noise threshold value specified for said selected downlink data rate, wherein the signal-to-noise threshold value specified for said selected downlink data rate is decreased by:

computing a decreased signal-to-noise threshold value 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.

13. The mobile access terminal of claim 12 , 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,

the processor responsive to successfully decoding said packet to decrease each of said plurality of signal-to-noise threshold values in accordance with the relation:

T=T j −(PER*Δ local)

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.

14. The mobile access terminal of claim 12 , the processor responsive to unsuccessfully decoding the packet to increase the signal-to-noise threshold value specified for the selected downlink data rate.