FIG. 7B also illustrates that the SRS transmission 726 has the potential to collide with uplink transmissions on a third CC, CC3 730. When this occurs, the UE may need to determine which CC, CC1 or CC3, to interrupt in order to transmit SRS.
Interruption Time
UEs with the capability of supporting more downlink carriers than uplink carriers may be configured to use an inactive, or unconfigured, uplink portion of a TDD CC that is configured in carrier aggregation for downlink-only operation to facilitate transmission of an SRS. The UE may need to switch from one CC in order to transmit the SRS transmission in the unconfigured uplink portion of the downlink-only TDD CC. For example, in FIG. 7A, the UE may switch or tune its transmitter away from CC1 in order to transmit SRS 708, 712 on an unconfigured uplink portion of CC2. This may cause an interruption to CC1, affecting both downlink and uplink traffic due to interruption of PUCCH, PUSCH, etc. on CC1. Such interruptions may potentially impact data rates and control transmissions in CC1 as well as downlink data rates of other CCs. The interruption time may vary, e.g., depending on whether the UE may need to perform inter-band switching or intra-band switching.
