CFRA Message 2 DCI Repetition for Uplink Reliability
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Solution Overview
Problem
Current wireless communication systems face challenges in ensuring reliable contention-free random access procedures due to potential failures in receiving critical messages, leading to increased latency and system inefficiency.
Innovation Solution
Implementing message two control channel repetition in contention-free random access procedures, where user equipment (UE) requests the base station to repeat downlink control information (DCI) transmissions, enhancing message reliability through multiple repetitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If message repetition is implemented to improve reliability, then the reliability of random access procedure is improved, but the device complexity and signaling overhead increase
Solution Approach 1:
The UE determines in advance whether message repetition is needed by evaluating criteria such as coverage enhancement requirements, message priority, and channel conditions before transmitting the random access message. The base station similarly determines repetition configuration beforehand based on UE capabilities and network conditions, avoiding complex real-time decisions during the random access procedure.
Solution Approach 2:
Message repetition is applied selectively only to specific messages (Msg1, Msg2, Msg3, or Msg4) based on their priority and reliability requirements, rather than uniformly to all messages. High-priority messages or messages in poor coverage conditions receive repetition, while others use standard transmission, optimizing the balance between reliability and complexity.
2Reliability
If message repetition is used to enhance reliability, then the reliability of critical random access messages is improved, but the transmission time and latency increase
Solution Approach 1:
The system pre-configures repetition parameters and determines the need for repetition before the random access procedure begins, based on historical channel conditions, UE capabilities, and message priority. This avoids time-consuming decisions during the actual access procedure.
Solution Approach 2:
The random access message is divided into multiple repetitions transmitted in sequence, with the UE able to stop receiving after successfully decoding any one repetition. This segmented approach reduces expected latency compared to transmitting all repetitions regardless of successful reception.
3Reliability
If multiple repetitions of DCI are transmitted to improve reliability, then the reliability of scheduling information delivery is improved, but the use of energy and network resources increases
Solution Approach 1:
DCI repetition is applied selectively based on the priority of the scheduled message and the channel conditions. Only high-priority DCI or DCI in poor coverage conditions receive multiple repetitions, while standard priority DCI uses single transmission, optimizing energy usage.
Solution Approach 2:
The base station determines the appropriate repetition level for DCI before transmission based on pre-configured parameters, UE capabilities, and current network conditions. This preliminary determination avoids unnecessary repetitions and optimizes energy consumption.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) and a base station may perform a contention-free random access (CFRA) procedure to establish a connection. The base station may transmit control signaling indicating a configuration for a first message of the CFRA including a preamble. The UE may transmit the first message in accordance with the configuration. The preamble of the first message may indicate a request for the base station to use repetition to transmit downlink control information (DCI) that schedules a second message of the CFRA procedure. In some examples, the UE may transmit the first message based on determining that one or more measurement values satisfy one or more thresholds. In response to the request, the base station may transmit one or more repetitions of the DCI and may transmit the second message of the CFRA procedure in accordance with the DCI.