Channel quality indicator method, associated base station, and associated user equipment
It would be to provide a method which will work with future versions of LTE-A, be backwards compatible and alleviate interference to signals for basic system operation. The method includes generating one or more Reference Signals associated with the one or more Channel Quality Indicators, and includes mapping the one or more Channel Quality Indicator-Reference Signals to the last symbol of the second slot of the one or more subframes.
1. A method implemented in a base station used in a wireless communications system, comprising:
transmitting to a user equipment (UE) two channel quality indicator (CQI) reference signals using two resource elements per transmission layer of a plurality of transmission layers within a subframe comprising a resource block, wherein each transmission layer of the plurality of transmission layers is multiplexed using frequency division multiplexing; and
receiving from the user equipment a report determined according to said two CQI reference signals;
wherein a value of a subframe offset corresponding to the subframe is within a range from 0 ms to (T CQI-RS —-1) ms, where T CQI-RS denotes a CQI reference signal transmission period, and the report comprises a rank indicator, a channel quality indicator, and a precoding matrix indicator, wherein:
the subframe comprises the resource block and a last orthogonal frequency division multiplexing symbol in the resource block conveys at least one of the two CQI reference signals;
the CQI reference signal transmission period is cell-specific and a CQI reporting period or a PMI reporting period is user equipment-specific;
the two channel quality indicator reference signals are repeated at a period of 5 subframes, 10 subframes, 20 subframes, 40 subframes, or 80 subframes; and
the CQI reference signal transmission period is 1 ms, 5 ms, 10 ms, 20 ms, 40 ms, or 80 ms.
2. The method according to claim 1 , wherein the CQI reporting period or the PMI reporting period is equal to or longer than the CQI reference signal transmission period.
3. The method according to claim 1 , wherein the value of the subframe offset is greater than 0 ms and up to (T CQI-RS -1) ms, where T CQI-RS denotes a CQI reference signal transmission period.
4. The method according to claim 1 , wherein the subframe offset is cell-specific.
5. The method according to claim 1 , wherein said two CQI reference signal resource elements are used for one or more antenna ports for spatial multiplexing, the number of said one or more antenna ports being equal to or less than 8, or for one or more transmission layers, the number of said one or more transmission layers being equal to or less than 8.
6. The method according to claim 1 , wherein a CQI reference signal position depends on a cyclic prefix (CP) length.
7. The method according to claim 1 , wherein the base station is configured to be used in a Coordinated Multi-Point (CoMP) transmission.
8. The method according to claim 1 , wherein the value of the subframe offset is greater than 0 ms and up to (T CQI-RS -1) ms, where T CQI-RS denotes the CQI reference signal transmission period, and the value of the subframe offset is taken to avoid channel quality indicator (CQI) reference signals being transmitted in the same subframe.
9. A base station used in a wireless communications system, comprising:
a transmitter to transmit to a user equipment (UE) two channel quality indicator (CQI) reference signals using two resource elements per transmission layer of a plurality of transmission layers within a subframe comprising a resource block, wherein each transmission layer of the plurality of transmission layers is multiplexed using frequency division multiplexing, and the CQI reference signal transmission is transmitted from the base station at a CQI reference signal transmission period; and
a receiver to receive from the user equipment a report determined according to the two CQI reference signals;
wherein a value of a subframe offset is within a range from 0 ms to (T CQI-RS -1) ms, where T CQI-RS denotes a CQI reference signal transmission period, and the report comprises a rank indicator, a channel quality indicator, and a precoding matrix indicator, wherein:
the subframe comprises the resource block and a last orthogonal frequency division multiplexing symbol in the resource block conveys at least one of the two CQI reference signals;
the CQI reference signal transmission period is cell-specific and a CQI reporting period or a PMI reporting period is user equipment-specific;
the two channel quality indicator reference signals are repeated at a period of 5 subframes, 10 subframes, 20 subframes, 40 subframes, or 80 subframes; and
the CQI reference signal transmission period is 1 ms, 5 ms, 10 ms, 20 ms, 40 ms, or 80 ms.
10. A method implemented in a user equipment (UE) used in a wireless communications system, comprising:
receiving from a base station two channel quality indicator (CQI) reference signals using two resource elements per transmission layer of a plurality of transmission layers within a subframe comprising a resource block, wherein each transmission layer of the plurality of transmission layers is multiplexed using frequency division multiplexing; and
transmitting to the base station a report determined according to said two CQI reference signals;
wherein the value of the subframe offset is within a range from 0 ms to (T CQI-RS -1) ms, where T CQI-RS denotes a CQI reference signal transmission period, and the report comprises a rank indicator, a channel quality indicator, and a precoding matrix indicator, wherein:
the subframe comprises the resource block and a last orthogonal frequency division multiplexing symbol in the resource block conveys at least one of the two CQI reference signals;
the CQI reference signal transmission period is cell-specific and a CQI reporting period or a PMI reporting period is user equipment-specific;
the two channel quality indicator reference signals are repeated at a period of 5 subframes, 10 subframes, 20 subframes, 40 subframes, or 80 subframes; and
the CQI reference signal transmission period is 1 ms, 5 ms, 10 ms, 20 ms, 40 ms, or 80 ms.
11. The method according to claim 10 , wherein the CQI reporting period or the PMI reporting period is equal to or longer than the CQI reference signal transmission period.
12. The method according to claim 10 , wherein the value of the subframe offset is greater than 0 ms and up to (T CQI-RS -1) ms, where T CQI-RS denotes the CQI reference signal transmission period.
13. The method according to claim 10 , wherein the subframe offset is cell-specific.
14. The method according to claim 10 , wherein said two CQI reference signal resource elements are used for one or more antenna ports for spatial multiplexing, the number of said one or more antenna ports being equal to or less than 8, or for one or more transmission layers, the number of said one or more transmission layers being equal to or less than 8.
15. The method according to claim 10 , wherein a CQI reference signal position depends on a cyclic prefix (CP) length.
16. The method according to claim 10 , wherein the base station is configured to be used in a Coordinated Multi-Point (CoMP) transmission.
17. A user equipment (UE) used in a wireless communications system, comprising:
a receiver to receive from a base station two channel quality indicator (CQI) reference signals using two resource elements per transmission layer of a plurality of transmission layers within a subframe comprising a resource block, wherein each transmission layer of the plurality of transmission layers is multiplexed using frequency division multiplexing, and the CQI reference signal transmission is transmitted from the base station at a CQI reference signal transmission period; and
a transmitter to transmit to the base station a report determined according to the two CQI reference signal resource elements;
wherein the value of the subframe offset is within a range from 0 ms to (T CQI-RS -1) ms, where T CQI-RS denotes a CQI reference signal transmission period, and the report comprises a rank indicator, a channel quality indicator, and a precoding matrix indicator, wherein:
the subframe comprises the resource block and a last orthogonal frequency division multiplexing symbol in the resource block conveys at least one of the two CQI reference signals;
the CQI reference signal transmission period is cell-specific and a CQI reporting period or a PMI reporting period is user equipment-specific;
the two channel quality indicator reference signals are repeated at a period of 5 subframes, 10 subframes, 20 subframes, 40 subframes, or 80 subframes; and
the CQI reference signal transmission period is 1 ms, 5 ms, 10 ms, 20 ms, 40 ms, or 80 ms.