Collision handling mechanisms for dynamic TDD systems
Methods, systems, and devices for wireless communication are described. Generally, the described techniques provide for communicating an uplink grant and a channel state information reference signal (CSI-RS) trigger. A wireless device may identify a pending collision for a slot of a carrier between a CSI-RS and uplink data. The wireless device may determine a communication configuration for the CSI-RS and the uplink data such that no collision occurs. The determined communication configuration for the CSI-RS may include delaying one of the colliding signals, transmitting only one of the colliding signals and suppressing the other, or reconfiguring the slot such that both signals can be transmitted successfully. Additionally, the UE and the base station may determine a CSI reporting configuration based on the determined communication configuration.
1. A method for wireless communication at a user equipment (UE), comprising:
receiving a set of backoff periods via a first downlink control signal;
receiving a channel state information reference signal (CSI-RS) trigger and an uplink grant;
identifying, for a slot of a carrier, a pending collision between a CSI-RS corresponding to the CSI-RS trigger and uplink data corresponding to the uplink grant;
receiving a second downlink control signal that corresponds to the CSI-RS, the uplink data, or neither the uplink grant nor the CSI-RS;
selecting a first backoff period from the set of backoff periods based at least in part on the second downlink control signal, wherein a communication configuration for the CSI-RS and the uplink data corresponds to a delay of the CSI-RS by the first backoff period;
performing measurements on the CSI-RS received in a second slot corresponding to the first backoff period from the slot;
identifying a CSI report trigger; and
determining a CSI reporting configuration based at least in part on the communication configuration associated with the pending collision, the measurements on the CSI-RS, and the CSI report trigger.
2. The method of claim 1 , wherein determining the communication configuration for the CSI-RS and the uplink data further comprises:
transmitting the uplink data in the slot.
3. The method of claim 2 , further comprising:
delaying performing measurements corresponding to the delay of the CSI-RS for the slot on the carrier.
4. The method of claim 2 , further comprising:
delaying transmission of a CSI report associated with the delay of the CSI-RS.
5. The method of claim 1 , further comprising:
determining that a reporting delay from the CSI-RS trigger does not exceed the second slot by at least a threshold number of slots;
determining a second backoff period comprising the first backoff period or the reporting delay; and
transmitting a CSI report in a third slot corresponding to the second backoff period from the slot in which the CSI report was triggered.
6. The method of claim 5 , wherein determining the second backoff period further comprises:
receiving a set of second backoff periods in a first downlink control signal;
the method further comprising:
receiving a second downlink control signal, wherein the second downlink control signal corresponds to one of the uplink grant, the CSI-RS trigger, or a downlink control signal that is separate from the uplink grant and the CSI-RS trigger; and
selecting one of the set of second backoff periods based at least in part on the received second downlink control signal.
7. The method of claim 6 , wherein at least one of the first downlink control signal and the second downlink control signal comprise downlink control information (DCI), a media access control (MAC) control element (CE), or a radio resource control (RRC) message.
8. The method of claim 1 , further comprising:
determining that a reporting delay from the CSI-RS trigger exceeds the second slot by at least a threshold number of slots; and
transmitting a CSI report in a third slot corresponding to a timing delay indicated in the CSI report trigger.
9. The method of claim 1 , further comprising:
determining that the carrier is one of a plurality of configured component carriers;
performing measurements on a CSI-RS received in the slot on at least a second component carrier of the plurality of configured component carriers; and
transmitting a CSI report comprising the measurements for the CSI-RS received in the slot on at least the second component carrier.
10. An apparatus for wireless communication at a user equipment (UE), comprising:
means for receiving a set of backoff periods via a first downlink control signal;
means for receiving a channel state information reference signal (CSI-RS) trigger and an uplink grant;
means for identifying, for a slot of a carrier, a pending collision between the CSI-RS corresponding to a CSI-RS trigger and uplink data corresponding to the uplink grant;
means for receiving a second downlink control signal that corresponds to the CSI-RS, the uplink data, or neither the uplink grant nor the CSI-RS;
means for selecting a first backoff period from the set of backoff periods based at least in part on the second downlink control signal, wherein a communication configuration for the CSI-RS and the uplink data corresponds to a delay of the CSI-RS by the first backoff period;
means for performing measurements on the CSI-RS received in a second slot corresponding to the first backoff period from the slot;
means for identifying a CSI report trigger; and
means for determining a CSI reporting configuration based at least in part on the communication configuration associated with the pending collision, the measurements on the CSI-RS, and the CSI report trigger.