Power control in a wireless communication system
A method of power control in a wireless communication system, wherein blocks are transmitted from a transmitter to a receiver via a wireless transport channel. The method comprises comparing a target signal quality value with a received signal quality value and providing the results of the comparing step to the transmitter to adjust transmit power based on the comparing step. The target signal quality value is set by the following steps: determining an initial target value; detecting if a data block has been received; detecting if received blocks have been successfully decoded; and decreasing the target value when pass blocks are received and increasing the target value when failed blocks are received subject to monitoring a period of inactivity on the transport channel in which no blocks are received.
1. A method of power control in a wireless communication system wherein blocks of a transport channel are transmitted from a transmitter to a receiver via a wireless transmission channel, there being a period of time where no data blocks are transmitted for that transport channel, the method comprising comparing a target signal quality value with a received signal quality value and providing the results of the comparing step to the transmitter to adjust transmit power based on the comparing step, wherein the target signal quality value is set by the following steps:
determining an initial target value;
detecting if a data block has been received, said detecting generating detection error events in said period of time which appear as fail blocks;
detecting if received blocks have been successfully decoded, and identifying the received blocks as pass or fail blocks; and
decreasing the target value when pass blocks are received and increasing the target value when fail blocks are received subject to monitoring a period of inactivity on the transport channel in which no blocks and fail blocks are identified and where the period of inactivity exceeds a threshold reducing a current target value to a value determined by the target value at commencement of the period of inactivity.
2. A method according to claim 1 , wherein blocks are transmitted via multiple transport channels and wherein an initial target value is set for each transport channel and a signal quality target is maintained for each transport channel, the target signal quality value used in the comparing step being derived from the multiple signal quality target values.
3. A method according to claim 2 , comprising the step of estimating the received signal quality value for each transport channel.
4. A method according to claim 2 , wherein multiple transport channels are transmitted on the same physical channel comprising the steps of estimating one received signal quality value for multiple transport channels.
5. A method according to claim 1 , wherein the target signal quality value is a signal to disturbance ratio for the channel, where the disturbance can be interference, noise, or interference plus noise.
6. A method according to claim 1 , wherein the period of inactivity is monitored by a timer.
7. A method according to claim 6 , comprising the step of resetting the timer when a good block is received.
8. A method according to claim 7 , comprising the step of, when a good block is received, comparing the current target value with a comparison target value and resetting and restarting the timer if the current target value is greater than the comparison target value, and resetting and freezing the timer if the current target value is less than the comparison target value, in which case the timer will be restarted when the target value becomes greater than the comparison target value.
9. A method according to claim 8 , wherein the comparison value is the initial target value.
10. A method according to claim 1 , wherein the period of inactivity is monitored by counting the number of transmission time intervals during which no good block is detected.
11. A method according to claim 1 , wherein the period of inactivity is monitored by counting the number of radio frames during which no good block is detected.
12. A method according to claim 1 , wherein the value which is determined by the target value at commencement of the period of inactivity is the target value at the commencement of the period of inactivity.
13. A method according to claim 1 , wherein the value which is determined by the target value at the commencement of the period of inactivity is obtained by subtracting an amount from the target value at the commencement of the period of inactivity.
14. A method according to claim 13 , comprising the step of checking if the step of subtracting the amount from the target value at commencement of the period of inactivity results in a value which is less than a comparison value, and if so increasing the value to the comparison value.
15. A method according to claim 14 , wherein the comparison value is the initial target value.
16. A method according to claim 1 comprising the step of determining if a block of data has been received, prior to the detecting step, using blind transport format detection.
17. A receiver for a wireless communications system, the receiver comprising:
means for detecting blocks of a transport channel transmitted from a transmitter to the receiver via a wireless transmission channel, there being a period of time where no data blocks are transmitted for that transport channel, said detecting generating detection error events in said period of time which appear as fail blocks;
means for detecting if blocks have been successfully decoded and identifying blocks as pass or fail;
means for generating a target signal quality value by decreasing the target value when pass blocks are received and increasing the value when fail blocks are received;
means for comparing the target signal quality value with a received signal quality value and providing the result of the comparing step to the transmitter to adjust transmit power based on the comparing step; and
means for monitoring a period of inactivity on the transport channel in which no blocks and fail blocks are identified and means operable to adjust the target value so that where the period of inactivity exceeds a threshold, the current target value is reduced to a value determined by the target value at commencement of the period of inactivity.
18. A receiver according to claim 17 , wherein said means for monitoring the period of inactivity is a clock.
19. A receiver according to claim 17 , wherein the means for monitoring the period of inactivity is operable to count the number of transmission time intervals in which no good block is detected.
20. A receiver according to claim 17 , wherein the means for monitoring the period of inactivity is operable to count the number of radio frames in which no good block is detected.
21. A receiver according to claim 17 , comprising means for storing initial target values for multiple transport channels and maintaining separate target signal quality values for multiple transport channels, wherein the target signal quality value which is compared with the received signal quality value is derived from said multiple targets.
22. A receiver according to claim 17 , comprising means for storing an amount by which the target value at commencement of the period of inactivity is reduced to obtain the value determined by the target value at commencement of the period of inactivity.
23. A wireless communication system comprising a receiver according to claim 17 and a transmitter, wherein the transmitter is operable to adjust transmit power based on the result of comparing the target signal quality value with the received signal quality value.
24. A communications system according to claim 23 , wherein the result of comparing the target signal quality value with the received signal quality value is supplied to the transmitter via a wireless transport channel.
25. A receiver for a wireless communications system, the receiver comprising:
a component arranged to detect blocks of a transport channel transmitted from a transmitter to the receiver via a wireless transmission channel, there being a period of time where no data blocks are transmitted for that transport channel, said detecting generating detection error events in said period of time which appear as fail blocks;
a component arranged to detect if blocks have been successfully decoded and identifying blocks as pass or fail;
a component arranged to generate a target signal quality value by decreasing the target value when pass blocks are received and increasing the value when fail blocks are received;
a component arranged to compare the target signal quality value with a received signal quality value and providing the result of the comparing step to the transmitter to adjust transmit power based on the comparing step; and
a component arranged to monitor a period of inactivity on the transport channel in which no blocks and fail blocks are identified and a component operable to adjust the target value so that where the period of inactivity exceeds a threshold, the current target value is reduced to a value determined by the target value at commencement of the period of inactivity.