Transmission timing adjustment in radio systems
View Patent ↗A method of adjusting the transmission time of a signal in a radio link, the method being performed by a transmitter configured to transmit the signal over the radio link to a receiver and comprising the steps of ascertaining an accuracy that the receiver assumes for the transmitter's clock, calculating an assumed drift of the transmitter's clock based on the assumed accuracy of that clock and the time since a previous correlation between the transmitter's clock and the receiver's clock; and transmitting the signal at a time dependent on the assumed drift.
1. A method of adjusting a transmission time of a signal in a radio link, the method being performed by a transmitter to transmit the signal over the radio link to a receiver and the method comprising the steps of: ascertaining, at the transmitter, an accuracy that the receiver assumes for the transmitter's clock, calculating, at the transmitter, an assumed drift of the transmitter's clock based at least on the assumed accuracy that the receiver will have made of the transmitter's clock and a time since a previous correlation between the transmitter's clock and the receiver's clock; and transmitting, by the transmitter, the signal at a time dependent on the assumed drift such that the transmission time is closer to the receiver's activation time than a predetermined transmission time for the signal, wherein the transmitter and the receiver operate according to a Bluetooth Low Energy (LE) system.
2. A method according to claim 1 , wherein the signal is transmitted earlier than the predetermined transmission time for the signal.
3. A method according to claim 2 , wherein the signal is transmitted earlier than the predetermined transmission time by a time approximately equal to the assumed drift of the transmitter's clock.
4. A method according to claim 1 , wherein the assumed accuracy for the transmitter's clock is a maximum permissible accuracy for a transmitter clock in the protocol being utilised.
5. A method according to claim 1 , further comprising the step of transmitting an indication of the transmitter's clock accuracy from the transmitter to the receiver, wherein that indication comprises a range of accuracy values.
6. A method according to claim 5 , wherein the assumed accuracy for the transmitter's clock is the maximum value in a transmitted range.
7. A method according to claim 1 wherein the signal is a periodic polling signal.
8. A system comprising: a transmitter configured to transmit a signal over a radio link to a receiver, wherein the transmitter is configured to: ascertain an accuracy that the receiver assumes for the transmitter's clock, calculate an assumed drift of the transmitter's clock based at least on the assumed accuracy that the receiver will have made of the transmitter's clock and a time since a previous correlation between the transmitter's clock and the receiver's clock, and transmit the signal at a time dependent on the assumed drift such that the transmission time is closer to the receiver's activation time than a predetermined transmission time for the signal, wherein the system further configured to operate according to a Bluetooth Low Energy (LE).