System and method for speed indication through transmit power control commands
Speed indication device ( 100 ) for determining a speed indication signal ( 410 ) indicating a speed of a wireless mobile telecommunication device ( 14 ) relative to the speed indication device ( 100 ), wherein the speed indication device ( 100 ) determines the speed indication signal ( 410 ) from a sequence of transmit power control commands sent by the wireless mobile telecommunication device ( 14 ) to an access point ( 12 ) in a wireless telecommunication device ( 14 ) to an access point ( 12 ) in a wireless telecommunication network for controlling, in use, a transmit power of a radio signal transmitted by the access point ( 12 ) to the wireless mobile telecommunication device ( 14 ). If the relative speed is found to be above a threshold, the speed may be calculated using a measurement of the Doppler frequency.
1. An apparatus for determining a speed indication signal indicating a speed of a wireless mobile telecommunication device relative to said apparatus, wherein said apparatus determines said speed indication signal from a sequence of transmit power control commands sent by said wireless mobile telecommunication device to an access point in a wireless telecommunication network for controlling, in use, a transmit power of a radio signal transmitted by said access point to said wireless mobile telecommunication device, wherein said apparatus comprises:
a memory for storing said sequence of transmit power control commands;
a logical filter circuit for determining a radio signal strength minimum in said radio signal at a location of said mobile telecommunication device by detecting if a predetermined number of consecutive transmit power control commands from said sequence of transmit power control commands each comprise either an ‘up’ or ‘down’ transmit power control command;
a speed information control device for providing a speed estimation signal for said wireless mobile telecommunication device; and
a Doppler frequency measurement device for determining a Doppler speed signal for said wireless mobile telecommunication device, said apparatus being adapted to provide said speed estimation signal in dependence on said speed indication signal for speeds of said wireless mobile telecommunication device below a predetermined threshold and on said Doppler speed signal for speeds above said predetermined threshhold;
wherein said speed information control device comprises a speed tuning device, said speed tuning device operative to perform the steps of:
determining a tuning value, said tuning value being a division of said Doppler speed signal over said speed-indication signal, said tuning value being filtered with a long-time constant; and
providing, in dependence of a predetermined threshold (V th ), for determining of said speed estimation signal:
speed-related information, in dependence of said tuning value, at speeds below said predetermined threshold (V th ); and
a tuned Doppler measurement signal at speeds above said predetermined threshold (V th ), said tuned Doppler measurement signal being said Doppler measurement signal multiplied by said tuning value.
2. A method for determining a speed indication signal indicating a speed of a wireless mobile telecommunication device relative to a stationary wireless access point, said method comprising the steps of:
determining said speed indication signal from a sequence of transmit power control commands sent by said wireless mobile telecommunication device to said access point for controlling, in use, a transmit power of a radio signal transmitted by said access point to said wireless mobile telecommunication device, wherein said step of determining said speed indication comprises the steps of:
storing information related to at least a portion of said sequence of transmit power control commands; and,
determining a radio signal strength minimum in said radio signal at a location of said mobile telecommunication device by detecting if a predetermined number of consecutive transmit power control commands from said sequence of transmit power control commands each comprise either an ‘up’ or ‘down’ transmit power control command;
determining a Doppler speed signal for said wireless mobile telecommunication device;
providing said speed estimation signal in dependence on said speed indication signal for speeds of said wireless mobile telecommunication device below a predetermined threshold and on said Doppler speed signal for speeds above said predetermined threshold;
determining a tuning value for a speed information control device, said tuning value being a division of said Doppler speed signal over said speed-indication signal, said tuning value being filtered with a long-time constant; and,
providing, in dependence of a predetermined threshold (V th ), for determining of said speed estimation signal:
speed-related information, in dependence of said tuning value, at speeds below said predetermined threshold (V th ); and,
a tuned Doppler measurement signal at speeds above said predetermined threshold (V th ), said tuned Doppler measurement signal being said Doppler measurement signal multiplied by said tuning value.