Method and system for characterizing a radio channel of a wireless network using variability of synchronization
View Patent ↗A speed parameter or channel quality parameter are determined in a mobile device based on variation in frequency offset measurement. A higher variation in the frequency offset measurement reflects a poorer channel quality and a higher speed; a lower variation in the frequency offset measurement reflects a better channel quality and a lower speed. The parameter(s) may be fed back to the system and used, for example, to make adaptive modulation and coding decisions.
1. A method comprising:
receiving a signal over a wireless communications channel;
making a plurality of frequency offset measurements in respect of the signal;
estimating a PDF of the frequency offset measurements;
determining at least one of a channel quality parameter and a speed parameter as a function of the PDF;
determining the measure of variation from the PDF.
2. The method of claim 1 wherein determining at least one of a channel quality parameter and a speed parameter as a function of the PDF comprises determining a width of the PDF.
3. A method comprising:
receiving a signal over a wireless communications channel;
making a plurality of frequency offset measurements in respect of the signal;
determining differences between consecutive frequency offset measurements;
determining at least one of a channel quality parameter and a speed parameter as a function of the differences between consecutive frequency offset measurements.
4. The method of claim 3 wherein determining at least one of a channel quality parameter and a speed parameter as a function of the differences between consecutive frequency offset measurements comprises determining a maximum difference over an observation period.
5. The method of claim 3 wherein determining a speed parameter comprises:
speed= K ×(measure of variation of frequency offset measurements based on differences between consecutive offset measurements)
where K is a constant.
6. The method of claim 3 further comprising:
transmitting an indication of at least one of the channel quality parameter and the speed parameter.
7. A mobile device comprising:
at least one antenna for receiving a signal;
a local frequency source;
a frequency offset determiner configured to determine frequency offset measurements between a frequency of the local frequency source and a frequency of the signal;
a parameter determiner configured to determine a PDF of the frequency offset measurements and to determine at least one of a channel quality parameter and a speed parameter as a function of the PDF.
8. The mobile device of claim 7 wherein the frequency offset determiner comprises an automatic frequency controller configured to make adjustments to the frequency of the local frequency source to synchronize with a remote frequency source, wherein the adjustments to the frequency are used as said frequency offset measurements.
9. The mobile device of claim 8 wherein the parameter determiner is configured to determine at least one of a channel quality parameter and a speed parameter by determining a width of the PDF.
10. A mobile device comprising:
at least one antenna for receiving a signal;
a local frequency source;
a frequency offset determiner configured to determine frequency offset measurements between a frequency of the local frequency source and a frequency of the signal;
a parameter determiner configured to determine differences between consecutive frequency offset measurements and at least one of a channel quality parameter and a speed parameter as a function of the differences between frequency offset measurements.
11. The mobile device of claim 10 wherein the parameter determiner is configured to determine at least one of a channel quality parameter and a speed parameter as a function of the differences between frequency offset measurements by determining a maximum difference over an observation period.
12. The mobile device of claim 10 wherein the parameter determiner is configured to determine the speed parameter by:
speed= K ×(measure of variation of frequency offset measurements based on differences between frequency offset measurements)
where K is a constant.
13. A computer readable medium having instructions stored thereon for execution by a mobile device, that when executed, cause the mobile device to execute a method comprising, in respect of a signal received over a wireless communications channel:
making a plurality of frequency offset measurements in respect of the signal;
estimating a PDF of the frequency offset measurements;
determining at least one of a channel quality parameter and a speed parameter as a function of the PDF.