Deterministic UE behavior for CSI/SRS reporting during DRX
The invention relates to a method for transmitting a periodic channel quality report (CSI) and/or a sounding reference symbol (SRS) from a UE to an eNodeB. To avoid double decoding at the eNodeB in transient phases, a deterministic behavior of the UE is defined by the invention, according to which the eNodeB can unambiguously determine whether the UE will transmit the CSI/SRS or not. According to one embodiment, the UL grants and/or DL assignments received until and including subframe N−4 only are considered; UL grants and/or DL assignments received by the UE after subframe N−4 are discarded for the determination. Additionally, DRX-related timers at subframe N−4 are considered for the determination. In a second embodiment, DRX MAC control elements from the eNodeB, instructing the UE to enter DRX, i.e., become Non-Active, are only considered for the determination if they are received before subframe N−4, i.e., until and including subframe N−(4+k).
1. A mobile station comprising:
a receiver which, in operation, receives, from a base station, configuration information for transmitting, in subframe N to the base station, at least one of a channel quality information report and a sounding reference symbol, and receives from the base station a media access control (MAC) control element regarding a discontinuous reception (DRX) operation,
circuitry which, in operation, determines whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N, based at least on the MAC control element received until and including subframe N−(4+k), where k is an integer value equal to or greater than 1, and
a transmitter which, in operation, does not transmit the channel quality information report or the sounding reference symbol to the base station in subframe N, in case the mobile station is determined to be not in DRX Active Time in subframe N.
2. The mobile station according to claim 1 , which is configured to transmit the channel quality information report and/or the sounding reference symbol periodically.
3. The mobile station according to claim 1 , wherein the circuitry, in operation, determines whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N, based on uplink resource grants for an uplink shared channel and/or downlink resource assignments for a downlink shared channel, which are received by the mobile station until and including subframe N−(4+k).
4. The mobile station according to claim 1 , wherein the transmitter, in operation, transmits the channel quality information report and/or the sounding reference symbol to the base station in subframe N, in case the mobile station is determined to be in DRX Active Time in subframe N.
5. The mobile station according to claim 1 , wherein the circuitry, in operation, determines whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N, based on DRX-related timers running for the mobile station including at least one of a DRX Inactivity Timer, a DRX OnDuration Timer, and a DRX Retransmission Timer.
6. The mobile station according to claim 1 , wherein the transmitter is configured, by radio resource control (RRC) signaling, to restrict periodic transmission of channel quality information reports to only during DRX Active Time.
7. The mobile station according to claim 1 , wherein the circuitry, in operation, determines to disregard any MAC control element regarding a DRX operation in subframes N−(3+k) to N.
8. The mobile station according to claim 1 , wherein the integer value of k is equal to 1.
9. A method performed by a mobile station comprising:
receiving, from a base station, configuration information for transmitting, in subframe N to the base station, at least one of a channel quality information report and a sounding reference symbol,
receiving, from the base station, a media access control (MAC) control element regarding a discontinuous reception (DRX) operation,
determining whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N, based at least on the MAC control element received until and including subframe N−(4+k), where k is an integer value equal to or greater than 1, and
determining not to transmit the channel quality information report or the sounding reference symbol to the base station in subframe N, in case the mobile station is determined to be not in DRX Active Time in subframe N.
10. The method according to claim 9 , comprising:
transmitting the channel quality information report and/or the sounding reference symbol periodically.
11. The method according to claim 9 , wherein the step of determining whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N is based on uplink resource grants for an uplink shared channel and/or downlink resource assignments for a downlink shared channel, which are received by the mobile station until and including subframe N−(4+k).
12. The method according to claim 9 , comprising:
transmitting the channel quality information report and/or the sounding reference symbol to the base station in subframe N, in case the mobile station is determined to be in DRX Active Time in subframe N.
13. The method according to claim 9 , wherein the step of determining whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N is based on DRX-related timers running for the mobile station including at least one of a DRX Inactivity Timer, a DRX OnDuration Timer, and a DRX Retransmission Timer.
14. The method according to claim 9 , comprising:
in response to radio resource control (RRC) signaling, restricting periodic transmission of channel quality information reports to only during DRX Active Time.
15. The method according to claim 9 , comprising:
determining to disregard any MAC control element regarding a DRX operation in subframes N−(3+k) to N.
16. The method according to claim 9 , wherein the integer value of k is equal to 1.