Method and access network for estimating the movement of a terminal of interest with respect to said access network
A method for estimating the movement of a terminal of interest with respect to an access network. An incoming frequency of a message of interest transmitted by the terminal of interest and received by a pair of base stations of the access network are measured. The incoming frequencies of calibration messages transmitted by calibration terminals and received by the pair of base stations are measured. A differential measurement error according to the incoming frequencies of the calibration messages is estimated. A difference in incoming frequency of the message of interest according to the incoming frequencies of the message of interest and according to the differential measurement error is estimated. The movement of the terminal of interest according to the difference in incoming frequency of the message of interest is estimated.
1. A method for estimating a movement of a terminal of interest with respect to an access network of a wireless communication system, the terminal of interest located in a geographical area served by a pair of base stations of the access network, the method comprising steps of:
measuring, for each base station, a frequency of arrival of a message of interest transmitted by the terminal of interest;
measuring, for said each base station, frequencies of arrival of calibration messages transmitted by calibration terminals, the calibration terminals being distinct from the terminal of interest;
estimating a differential measurement error for the pair of base stations based on the frequencies of arrival of the calibration messages;
estimating a frequency difference of arrival of the message of interest based on the frequencies of arrival of the message of interest and on the differential measurement error;
estimating the movement of the terminal of interest based on the frequency difference of arrival of the message of interest for the pair of base stations;
wherein movements of all or a subset of the calibration terminals are not known; and
wherein the estimation of the differential measurement error comprises calculating, for each calibration message, a frequency difference of arrival of said each calibration message for the pair of base stations based on the measured frequencies of arrival of said each calibration message, the differential measurement error being estimated by calculating an average value of the frequency differences of arrival of the calibration messages.
2. The method according to claim 1 , further comprising a step of selecting messages received during a time window of a predetermined length comprising a reception of the message of interest as the calibration messages.
3. The method according to claim 1 , wherein the subset of the calibration terminals are reference terminals, each reference terminal having a predetermined movement.
4. The method according to claim 1 , wherein the terminal of interest are located in a geographical area served by at least three base stations forming three pairs of base stations, the method further comprising steps of: estimating the frequency difference of arrival of the message of interest for each of the three pairs of base stations; and estimating the movement of the terminal of interest based on the frequency differences of arrival of the message of interest estimated for the three pairs of base stations.
5. An access network to estimate a movement of a terminal of interest, comprising:
a pair of base stations, the terminal of interest being located in a geographical area served by the pair of base stations, each base station comprising a processor configured to measure a frequency of arrival of a message of interest transmitted by the terminal of interest and frequencies of arrival of calibration messages transmitted by calibration terminals, the calibration terminals being distinct from the terminal of interest;
a processing server, comprising a processor, configured to:
calculate a frequency difference of arrival of each calibration message for the pair of base stations based on the measured frequencies of arrival of said each calibration message;
estimate a differential measurement error for the pair of base stations by calculating an average value of the frequency differences of arrival of the calibration messages;
estimate a frequency difference of arrival of the message of interest based on the measured frequencies of arrival of the message of interest and on the differential measurement error; and
estimate the movement of the terminal of interest based on the frequency difference of arrival of the message of interest for the pair of base stations; and
wherein movements of all or a subset of the calibration terminals are not known.
6. The access network according to claim 5 , wherein messages received during a time window of a predetermined length comprising a reception of the message of interest are selected as the calibration messages.
7. A wireless communication system comprising the terminal of interest, the calibration terminals and the access network according to claim 5 .
8. A system according to claim 7 , wherein the subset of the calibration terminals are reference terminals, each reference terminal having a predetermined movement.