Processing digital samples in a wireless receiver
A method of processing digital samples of a signal received at a receiver of a wireless communication system includes monitoring channel conditions and generating a channel indicator including at least one channel parameter by performing at least one of: estimating a channel mobility parameter and comparing it with a threshold; estimating a channel parameter of the energy of the channel outside a predefined temporal window and comparing it with a threshold; estimating a channel temporal duration parameter and establishing if it meets predetermined criteria; estimating a channel-zero location parameter and establishing if it meets predetermined criteria; estimating a received-signal signal-to-disturbance power ratio and comparing it to a threshold; estimating an estimated-channel-response signal-to-disturbance power ratio; estimating the degree of non-stationarity of the disturbance at the receiver input; and selecting one of a plurality of processing routines for processing the digital samples based on said channel indicator. Related receivers are also described.
1. A method of processing radio signals in a wireless radio receiver to identify an n-ray channel condition comprising:
receiving signal samples and estimating a plurality of channel taps from the samples based on a tapped delay line model of the channel impulse response;
estimating for each of the channel taps a signal power and a disturbance power;
filtering the estimated signal power to provide a filtered signal power quantity;
filtering the estimated disturbance power to provide a filtered disturbance power quantity;
using the filtered power quantities to determine n strongest channel taps;
generating first and second comparison parameters using the strongest channel taps and at least one other channel tap;
providing a comparison result based on the first and second comparison parameters and a threshold value, and;
identifying an n-ray channel condition from the comparison result.
2. The method according to claim 1 , wherein n=1 and the step of identifying an n-ray channel condition comprises identifying a single ray channel condition.
3. The method according to claim 1 , wherein the step of identifying an n-ray channel condition is used to select one of a rake processing and equalisation processing.
4. The method according to claim 1 , wherein the step of generating the first comparison parameter comprises determining the ratio of the filtered signal power quantity and the filtered disturbance power quantity for the n strongest channel taps, and the second comparison parameter, the ratio of the filtered signal power quantity and the filter disturbance power quantity for the at least one other channel tap.
5. The method according to claim 4 , wherein the ratios are filtered to generate the respective first and second comparison parameters.
6. The method according to claim 1 , wherein the step of generating the first and second comparison parameters comprises filtering a multiplicand of the filtered signal power quantity for the strongest channel tap and the filtered disturbance power quantity for the at least one other channel tap as the first comparison parameter, and filtering a multiplicand of the filtered signal power quantity for the at least one other channel tap and the filter disturbance power quantity for the strongest channel tap.
7. The method according to claim 1 , wherein the at least one other channel tap is the second strongest channel tap.
8. The method according to claim 1 , wherein the at least one other channel tap comprises all channel taps apart from the n strongest taps.
9. A radio receiver for a wireless communication system comprising:
means for receiving signal samples and estimating a plurality of channel taps from the samples based on a tapped delay line model of the channel impulse response;
means for estimating for each of the channel taps a signal power and a disturbance power;
means for filtering the estimated signal power to provide a filtered signal power quantity;
means for filtering the estimated disturbance power to provide a filter disturbance power quantity;
means for using the filtered power quantities to determine n strongest channel taps;
means for generating first and second comparison parameters using the n strongest channel taps and at least one other channel tap;
means for providing a comparison result based on the first and second comparison parameters and a threshold value; and
means for identifying an n-ray channel condition from the comparison result.
10. The receiver according to claim 9 , which comprises a rake processing function and an equalisation processing function and additionally comprises means for selecting one of the rake processing function and equalisation processing function based on the output from the identifying means.
11. A computer program product comprising program code stored on a non-transitory computer readable medium which when executed by a processor implements a method according to claim 1 .
12. A radio receiver for a wireless communication system comprising:
a wireless interface for receiving digital samples;
a processor arranged to execute a program which implements the steps of claim 1 ;
a memory holding a rake processing code sequence and an equalisation processing code sequence; the processor adapted to execute one of the rake processing and equalisation processing sequence in dependence on the identified n-ray channel condition.