Doppler shift compensation apparatus and method
The present disclosure relates to a Doppler shift compensation scheme applicable in a high mobility communication system. In some examples, a Doppler shift compensation apparatus may include an angle measuring unit configured to measure Angle Of Arrival (AOA) information of a User Equipment (UE); a velocity calculating unit configured to calculate a velocity information of the UE based on the measured AOA information; a frequency shift estimating unit configured to estimate Doppler shift of the UE based on the measured AOA information and the calculated velocity of the UE; a frequency shift compensation triggering unit configured to trigger Doppler frequency shift compensation based on the estimated Doppler shift of the UE; and a frequency shift compensating unit configured to perform the Doppler frequency shift compensation based on a trigger instruction from the frequency shift compensation triggering unit. Doppler shift compensation methods are also described in some other examples of the present disclosure.
1. A Doppler shift compensation apparatus, comprising:
an angle measuring unit configured to measure Angle Of Arrival (AOA) information of a User Equipment (UE);
a velocity calculating unit configured to calculate a velocity information of the UE based on the measured AOA information;
a frequency shift estimating unit configured to estimate Doppler shift of the UE based on the measured AOA information and the calculated velocity of the UE;
a frequency shift compensation triggering unit configured to trigger Doppler frequency shift compensation based on the estimated Doppler shift of the UE; and
a frequency shift compensating unit configured to perform the Doppler frequency shift compensation based on a trigger instruction received from the frequency shift compensation triggering unit.
2. The Doppler shift compensation apparatus according to claim 1 , wherein
the frequency shift compensation triggering unit is configured to divide a full span of Doppler shift of a UE into a plurality of extents, and
if Doppler shifts of the UE estimated in a first predetermined number of estimation periods fall in one and the same extent, the frequency shift compensation triggering unit is configured to determine the one and the same extent as a stable extent.
3. The Doppler shift compensation apparatus according to claim 2 , wherein
the frequency shift compensation triggering unit is configured to trigger, in a second predetermined number of estimation periods, the Doppler frequency shift compensation in a hybrid compensation mode with a median of the stable extent or with an average of the Doppler shifts of the UE estimated in the first predetermined number of estimation periods.
4. The Doppler shift compensation apparatus according to claim 2 , wherein
the frequency shift compensation triggering unit is configured to trigger, in each estimation period, the Doppler frequency shift compensation in an accurate compensation mode with the estimated Doppler shift of the UE, if the frequency shift compensation triggering unit determines no stable extent.
5. The Doppler shift compensation apparatus according to claim 2 , wherein
if the UE is moving from a Base Station (BS) to which the Doppler shift compensation apparatus belongs to another BS,
the Doppler shift compensation apparatus is configured to transfer the estimated Doppler shifts in some periods of the first predetermined number of estimation periods to the other BS via an inter-BS interface; and/or
if the UE is moving from another BS to a Base Station (BS) to which the Doppler shift compensation apparatus belongs,
the Doppler shift compensation apparatus is configured to receive the estimated Doppler shifts in some periods of the first predetermined number of estimation periods from the other BS via an inter-BS interface, and
the frequency shift estimating unit is configured to estimate Doppler shifts of the UE in the rest periods of the first predetermined number of estimation periods.
6. The Doppler shift compensation apparatus according to claim 5 , wherein the inter-BS interface is X2 interface or S1 interface.
7. The Doppler shift compensation apparatus according to claim 1 , wherein the angle measuring unit is configured to measure the AOA information of the UE by using the UE's Channel Quality Index (CQI) reports reported respectively at a start point and an end point of an estimation period.
8. The Doppler shift compensation apparatus according to claim 1 , wherein the Doppler shift compensation apparatus is used in a Long Term Evolution (LTE) system, an LTE-Advanced system, or a Time Division Synchronous Code Division Multiple Access (TD-SCDMA) system.
9. A Doppler shift compensation method, comprising:
measuring Angle Of Arrival (AOA) information of a User Equipment (UE);
calculating a velocity information of the UE based on the measured AOA information;
estimating Doppler shift of the UE based on the measured AOA information and the calculated velocity of the UE; and
triggering and performing Doppler frequency shift compensation based on the estimated Doppler shift of the UE.
10. The Doppler shift compensation method according to claim 9 , wherein the Doppler frequency shift compensation triggering and performing step includes:
if Doppler shifts of the UE estimated in a first predetermined number of estimation periods fall in one and the same extent, determining the one and the same extent as a stable extent, wherein a full span of Doppler shift of a UE is divided into a plurality of extents;
triggering, in a second predetermined number of estimation periods, the Doppler frequency shift compensation in a hybrid compensation mode with a median of the stable extent or with an average of the Doppler shifts of the UE estimated in the first predetermined number of estimation periods.
11. The Doppler shift compensation method according to claim 10 , wherein the Doppler frequency shift compensation triggering and performing step further includes: triggering, in each estimation period, the Doppler frequency shift compensation in an accurate compensation mode with the estimated Doppler shift of the UE, if no stable extent is determined.
12. The Doppler shift compensation method according to claim 10 , further comprising: if the UE is moving from a Base Station (BS) to another BS, transferring the estimated Doppler shifts in some periods of the first predetermined number of estimation periods from the BS to the other BS via an inter-BS interface.
13. The Doppler shift compensation method according to claim 10 , further comprising:
if the UE is moving from an originating Base Station (BS) to a destination BS,
receiving, at the destination BS, the estimated Doppler shifts in some periods of the first predetermined number of estimation periods from the originating BS via an inter-BS interface, and
estimating, at the destination BS, Doppler shifts of the UE in the rest periods of the first predetermined number of estimation periods.
14. The Doppler shift compensation method according to claim 12 , the inter-BS interface is X2 interface or S1 interface.
15. The Doppler shift compensation method according to claim 9 , wherein the AOA information of the UE I measured by using the UE's Channel Quality Index (CQI) reports reported respectively at a start point and an end point of an estimation period.
16. The Doppler shift compensation method according to claim 9 , wherein the Doppler shift compensation method is used in a Long Term Evolution (LTE) system, an LTE-Advanced system, or a Time Division Synchronous Code Division Multiple Access (TD-SCDMA) system.