Uplink HARQ feedback channel design for carrier aggregation in OFDMA systems
HARQ feedback channel design for carrier aggregation (CA) is proposed in a multi-carrier LTE/LTE-A system. In one novel aspect, a predefined rule for HARQ feedback channel format switching is adopted by the system. Different HARQ formats are supported: single component carrier (non-CA) mode, carrier aggregation with small payload size (CA-S) mode, carrier aggregation with large payload size (CA-L) mode, and fallback mode. From the various CA and non-CA formats, the format to be used for uplink HARQ feedback channel is determined based on: UE capability for the maximum number of CCs supported; CC configuration information by RRC layer; and detection results of downlink schedulers. The CC configuration information may include the number of CCs that are configured and a specific HARQ format to be used. Because more reliable upper layer configuration is used to make the HARQ format-switching decision, the risk of UE and eNB mismatch is greatly reduced.
1. A method comprising:
receiving an upper layer configuration message from an eNB by a user equipment (UE) in a multi-carrier wireless communication network with carrier aggregation (CA);
receiving one or more downlink (DL) grants from the eNB;
determining a HARQ feedback format based on UE capability of maximum number of CCs supported, detection result of the received DL grants, and the upper layer configuration; and
transmitting HARQ feedback information using the determined HARQ feedback format.
2. The method of claim 1 , wherein the UE uses single CC (non-CA) format, and wherein the UE supports a single CC.
3. The method of claim 1 , wherein the UE switches to single CC (non-CA) format, wherein the UE supports more than one CC, and wherein only one CC is configured by upper layer.
4. The method of claim 1 , wherein the UE switches to CA with small payload size (CA-S) format, wherein the UE supports up to two CCs, wherein two CCs are configured by upper layer, and wherein the UE detects at least one DL grant for the data transmission over a secondary CC (SCC).
5. The method of claim 1 , wherein the UE switches to CA with large payload size (CA-L) format, wherein the UE supports up to five CCs, wherein more than one CC are configured by upper layer, and wherein in UE detects at least one DL grant for the data transmission over a secondary CC (SCC).
6. The method of claim 1 , wherein the UE switches to single CC (non-CA) format in fallback mode, wherein the UE supports more than one CC, wherein more than one CCs are configured by upper layer, and wherein the UE detects only one DL grant for the data transmission over a primary CC (PCC).
7. A User Equipment (UE), comprising:
a Radio Resource Control (RRC) layer module that receives a configuration message from an eNB;
a Physical (PHY) or Media Access Control (MAC) layer module that receives one or more downlink (DL) grants from the eNB, wherein the PHY or MAC layer module determines a HARQ feedback format based on UE capability of maximum number of CCs supported, detection result of the received DL grants, and the configuration message; and
an antenna that transmits HARQ feedback information, wherein the HARQ feedback information was encoded using the determined HARQ feedback format.
8. The UE of claim 7 , wherein the UE uses single CC (non-CA) format, and wherein the UE supports a single CC.
9. The UE of claim 7 , wherein the UE switches to single CC (non-CA) format, wherein the UE supports more than one CC, and wherein only one CC is configured by upper layer.
10. The UE of claim 7 , wherein the UE switches to CA with small payload size (CA-S) format, wherein the UE supports up to two CCs, wherein two CCs are configured by upper layer, and wherein in UE detects at least one DL grant for the data transmission over a secondary CC (SCC).
11. The UE of claim 7 , wherein the UE switches to CA with large payload size (CA-L) format, wherein the UE supports up to five CCs, wherein more than one CC are configured by upper layer, and wherein in UE detects at least one DL grant for the data transmission over a secondary CC (SCC).
12. The UE of claim 7 , wherein the UE switches to single CC (non-CA) format in fallback mode, wherein the UE supports more than one CC, wherein in more than one CCs are configured by upper layer, and wherein the UE only detects one DL grant for the data transmission over PCC.
13. A method comprising:
transmitting an upper layer configuration message from an eNB to a user equipment (UE) in a multi-carrier wireless communication network with carrier aggregation (CA);
transmitting one or more downlink (DL) grants;
determining a HARQ feedback format based on UE capability of maximum number of CCs supported, the transmitted DL grants, and the upper layer configuration; and
receiving and decoding HARQ feedback information using the determined HARQ feedback format.
14. The method of claim 13 , wherein the eNB uses single CC (non-CA) format to decode the HARQ feedback information for non-CA-capable UE.
15. The method of claim 13 , wherein the eNB uses single CC (non-CA) format to decode the HARQ feedback information for CA-capable UE, where the eNB configures only one CC by upper layer.
16. The method of claim 13 , wherein the eNB uses CA with small payload size (CA-S) format to decode the HARQ feedback information, wherein the UE supports up to two CCs, and wherein two CCs are configured by upper layer.
17. The method of claim 13 , wherein the eNB uses CA with large payload size (CA-L) format to decode the HARQ feedback information, wherein the UE supports up to five CCs, and wherein more than one CC are configured by upper layer.
18. The method of claim 13 , wherein the eNB uses single CC (non-CA) format to decode HARQ feedback information in fallback mode for CA-capable UE, wherein in more than one CCs are configured by upper layer.
19. A base station, comprising:
a Radio Resource Control (RRC) layer module that transmits an upper layer configuration message to a user equipment (UE) in a multi-carrier wireless communication network with carrier aggregation (CA);
a Physical (PHY) or Media Access Control (MAC) layer module that transmits one or more downlink (DL) grants, wherein the PHY or MAC layer module determines a HARQ feedback format based on UE capability of maximum number of CCs supported, the transmitted DL grants, and the upper layer configuration; and
an antenna that receives HARQ feedback information, wherein the HARQ feedback information is decoded using the determined HARQ feedback format.
20. The base station of claim 19 , wherein the eNB uses single CC (non-CA) format to decode the HARQ feedback information for non-CA-capable UE.
21. The base station of claim 19 , wherein the eNB uses single CC (non-CA) format to decode the HARQ feedback information for CA-capable UE, where the eNB configures only one CC by upper layer.
22. The base station of claim 19 , wherein the eNB uses CA with small payload size (CA-S) format to decode the HARQ feedback information, wherein the UE supports up to two CCs, and wherein two CCs are configured by upper layer.
23. The base station of claim 19 , wherein the eNB uses CA with large payload size (CA-L) format to decode the HARQ feedback information, wherein the UE supports up to five CCs, and wherein more than one CC are configured by upper layer.
24. The method of claim 19 , wherein the eNB uses single CC (non-CA) format to decode HARQ feedback information in fallback mode for CA-capable UE, wherein in more than one CCs are configured by upper layer.