Method and communication device for handling time offsets between communication device and transmission points
A method of handling a plurality of time offsets between a communication device of a wireless communication system and a plurality of transmission points of the wireless communication system is disclosed. The method is utilized in the communication device, and comprises obtaining the plurality of time offsets by using a first reference signal; and transmitting the plurality of time offsets to the plurality of transmission points, respectively; wherein the plurality of transmission points compensate the plurality of time offsets, respectively, when communicating with the communication device.
1. A method of handling a plurality of time offsets between a communication device of a wireless communication system and a plurality of transmission points of the wireless communication system, the method being utilized in the communication device and comprising:
obtaining the plurality of time offsets by using a first reference signal;
determining a plurality of quantized time offsets by performing a quantization on the plurality of time offsets, respectively; and
transmitting the plurality of quantized time offsets to the plurality of transmission points, respectively;
wherein the plurality of transmission points compensate the plurality of time offsets, respectively, when communicating with the communication device;
wherein the quantization is a linear quantization represented by the following equation:
Q
n
=
L
ini
+
n
·
(
2
·
Δ
req
)
,
n
=
0
,
1
,
…
,
⌊
L
req
-
L
ini
2
Δ
req
⌋
,
where 2Δ req is a step size of the linear quantization, (0, L req ) is a range of the linear quantization, and L ini is an initial value of the linear quantization.
2. The method of claim 1 , wherein a range of the quantization is related to a requirement on the plurality of time offsets.
3. The method of claim 1 , wherein the linear quantization is a 3-bit linear quantization with 2Δ req =0.429 μs, L ini =0 and L req =3 μs, for determining the plurality of quantized time offsets of (0, 0.43, 0.86, 1.29, 1.71, 2.14, 2.57, 3.0), with 2Δ req =0.6 μs, L ini =0 and L req =3 μs, for determining the plurality of quantized time offsets of (0, 0.6, 1.2, 1.8, 2.4, 3.0), or with 2Δ req =0.375 μs, L ini =Δ req =0.1875 μs and L req =3 μs, for determining the plurality of quantized time offsets of (0.19, 0.56, 0.94, 1.31, 1.69, 2.05, 2.44, 2.81).
4. The method of claim 1 , further comprising:
obtaining channel information between the communication device and the plurality of transmission points by using a second reference signal;
determining a plurality of precoding matrix indicators corresponding to the plurality of transmission points, respectively, according to the channel information; and
transmitting the plurality of precoding matrix indicators to the plurality of transmission points, respectively.
5. The method of claim 4 , wherein the communication device transmits the plurality of time offsets periodically with a first period, and the first period is greater than a second period for transmitting the plurality of precoding matrix indicators periodically.
6. The method of claim 1 , wherein the plurality of transmission points are in a cooperating set, one of the plurality of transmission points is a reference point, and the plurality of time offsets are relative time offsets of the plurality of transmission points with respect to an actual time offset of the reference point, respectively.
7. The method of claim 6 , wherein the reference point is selected from the plurality of transmission points according to at least one of time delays, signal amplitudes, channel qualities, reference signal received powers (RSRPs) and reference signal received qualities (RSRQs) of the plurality of transmission points.
8. A communication device of a wireless communication system for handling a plurality of time offsets between the communication device and a plurality of transmission points of the wireless communication system, the communication device comprising:
means for obtaining the plurality of time offsets by using a first reference signal;
means for determining a plurality of quantized time offsets by performing a quantization on the plurality of time offsets, respectively; and
means for transmitting the plurality of quantized time offsets to the plurality of transmission points, respectively;
wherein the plurality of transmission points compensate the plurality of time offsets, respectively, when communicating with the communication device;
wherein the quantization is a linear quantization represented by the following equation:
Q
n
=
L
ini
+
n
·
(
2
·
Δ
req
)
,
n
=
0
,
1
,
…
,
⌊
L
req
-
L
ini
2
Δ
req
⌋
,
where 2Δ req is a step size of the linear quantization, (0, L req ) is a range of the linear quantization, and L ini is an initial value of the linear quantization.
9. The communication device of claim 8 , wherein a range of the quantization is related to a requirement on the plurality of time offsets.
10. The communication device of claim 8 , wherein the linear quantization is a 3-bit linear quantization with 2Δ req =0.429 μs, L ini =0 and L req =3 μs, for determining the plurality of quantized time offsets of (0, 0.43, 0.86, 1.29, 1.71, 2.14, 2.57, 3.0), with 2Δ req =0.6 μs, L ini =0 and L req =3 μs, for determining the plurality of quantized time offsets of (0, 0.6, 1.2, 1.8, 2.4, 3.0), or with 2Δ req =0.375 μs, L ini =Δ req =0.1875 μs and L req =3 μs, for determining the plurality of quantized time offsets of (0.19, 0.56, 0.94, 1.31, 1.69, 2.05, 2.44, 2.81).
11. The communication device of claim 8 , further comprising:
means for obtaining channel information between the communication device and the plurality of transmission points by using a second reference signal;
means for determining a plurality of precoding matrix indicators corresponding to the plurality of transmission points, respectively, according to the channel information; and
means for transmitting the plurality of precoding matrix indicators to the plurality of transmission points, respectively.
12. The communication device of claim 11 , wherein the communication device transmits the plurality of time offsets periodically with a first period, and the first period is greater than a second period for transmitting the plurality of precoding matrix indicators periodically.
13. The communication device of claim 8 , wherein the plurality of transmission points are in a cooperating set, one of the plurality of transmission points is a reference point, and the plurality of time offsets are relative time offsets of the plurality of transmission points with respect to an actual time offset of the reference point, respectively.
14. The communication device of claim 13 , wherein the reference point is selected from the plurality of transmission points according to at least one of time delays, signal amplitudes, channel qualities, reference signal received powers (RSRPs) and reference signal received qualities (RSRQs) of the plurality of transmission points.