Fine time tracking with improved resolution
The present invention relates to compensation method and circuit for compensating time drifts in a receiver suited for multi-path environment. The time drifts are separated into a first component common to groups of paths belonging to the same radio link, for example a radio link of a connection between a user equipment and a base station, and second components valid for each individual path belonging to a group. The first component is processed by employing first feedback means with a first bandwidth, and the second components are processed by employing a second feedback means with a second bandwidth, wherein the first bandwidth is set to a value higher than the second bandwidth. Thereby, the bandwidth of the loop devoted to the individual tracking of each path can be slower and adjusted to environmental conditions, so as to allow application of a principle of interference mitigation for improving time resolution.
1. A compensation circuit for compensating time drifts in a multi-path receiver environment, said compensation circuit comprising:
first feedback means arranged for processing a first component of said time drifts in the multi-path receiver environment at a higher bandwidth, said first component being a common time drift component and able to affect all paths belonging to a radio link; and
second feedback means arranged for processing second components of said time drifts in the multi-path receiver environment at a lower bandwidth that is different and lower than the higher bandwidth, said second components being differential time drift components and respectively valid for each individual one of said paths belonging to said radio link, wherein at least two received paths of said paths belonging to the radio link comprise respective fingers of a Rake receiver.
2. A compensation circuit according to claim 1 , wherein said time drifts are obtained from at least one incoherent early-late gate.
3. A compensation circuit according to claim 1 , wherein said first and second feedback means are provided in a dual-loop delay locked loop.
4. A compensation circuit according to claim 1 , further comprising control means for applying a common control signal to groups of received paths, each group belonging to a Radio link, and an individual control signal to individual paths in response to processing outputs of said first and second feedback means.
5. A compensation circuit according to claim 4 , wherein said common and individual control signals comprise up and down commands for delay control.
6. A method of compensating time drifts in a receiver suited for a multi-path environment, said method comprising the steps of:
separating said time drifts in the receiver suited for the multi-path environment into a first component, said first component being a common time drift component which is common to at least one group of paths including at least two received paths and second components, said second components being differential time drift components and respectively valid for each individual path of said at least one group of paths, wherein the at least two received paths comprise respective fingers of a Rake receiver;
processing said first component by employing first feedback means with a first bandwidth;
processing said second components by employing a second feedback means with a second bandwidth; and
setting said first bandwidth to a value different and higher than said second bandwidth.
7. A method according to claim 6 , further comprising the step of deriving said time drifts from an early-late error determination step.
8. A method according to claim 6 , further comprising the step of applying interference mitigation to the processing results.
9. A method according to claim 6 , further comprising the step of estimating coefficients which connect path strengths and path errors.
10. A method according to claim 9 , wherein said estimation is based on a determination of cross variances between said path strengths and path errors.
11. A method according to claim 9 , wherein said estimation is based on an estimation of relative delays between different ones of said at least two received paths.
12. A method according to claim 6 , further comprising the step of adapting a ratio between values of said first and second bandwidths to environmental conditions.
13. A non-transitory computer readable storage medium having computer-executable instructions stored thereon that, when executed by a computer processor, cause the computer processor to perform a method of compensating time drifts in a receiver suited for multi-path environment, the method comprising:
separating said time drifts in the receiver suited for the multi-path environment into a first component, said first component being a common time drift component which is common to at least one group of paths including at least two received paths and second components, said second components being differential time drift components and respectively valid for each individual path of said at least one group of paths, wherein the at least two received paths comprise respective fingers of a Rake receiver;
processing said first component by employing first feedback means with a first bandwidth;
processing said second components by employing a second feedback means with a second bandwidth; and
setting said first bandwidth to a value higher and different than said second bandwidth.
14. The non-transitory computer readable storage medium according to claim 13 , wherein said instructions, when executed by the computer processor, further cause the computer processor to adapt a ratio of values between said first and second bandwidths to environmental conditions.