Supplementary Uplink Random Access Across Multiple Carriers
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently switching between uplink carriers for random access procedures, leading to unsuccessful transmissions and suboptimal resource utilization.
Innovation Solution
A method for a WTRU to transmit random access preambles on multiple uplink carriers, including determining an RA-RNTI based on a carrier offset, and monitoring for a random access response to switch between carriers when initial transmissions are unsuccessful.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the WTRU transmits random access preambles on a single uplink carrier, then the device complexity is reduced, but the transmission reliability deteriorates due to unsuccessful transmissions
Solution Approach 1:
The WTRU dynamically switches between uplink carriers based on transmission success. The system transitions from a static single-carrier approach to a dynamic multi-carrier approach where the WTRU attempts random access on the first UL carrier and switches to the second UL carrier if the maximum number of RA retransmissions is met, thereby improving transmission reliability while managing complexity through conditional carrier switching
2Reliability
If the WTRU switches to a second uplink carrier after maximum retransmissions, then the transmission reliability improves, but the access delay increases
Solution Approach 1:
The WTRU is pre-configured with multiple uplink carriers and the maximum number of RA retransmissions threshold before attempting random access. This preliminary configuration allows the WTRU to quickly switch to the second UL carrier without delay when the retransmission threshold is reached, as all necessary parameters (carrier offsets, RA-RNTI determination methods) are already established, thus minimizing access delay while maintaining reliability
3Productivity
If the WTRU monitors for RAR based on RA-RNTI determined by carrier offset, then the resource utilization improves, but the measurement precision requirements increase
Solution Approach 1:
The WTRU autonomously determines the RA-RNTI using the carrier offset of the second UL carrier without requiring additional network signaling or configuration messages. The WTRU calculates the RA-RNTI based on the formula involving the carrier offset, thereby self-serving the resource allocation function and improving resource utilization efficiency while the precision requirements are managed through standardized offset values
Data Source
AI summary
A method performed by a WTRU may comprise transmitting, to a gNB, a first random access preamble on a first physical random access channel (PRACH) resource of a first uplink (UL) carrier and determining that the transmission on the first PRACH resource is unsuccessful. The method may further comprise determining that a maximum number of random access retransmissions on the first UL carrier is met and in response, the WTRU may transmit, to the gNB on a second UL carrier, a third random access preamble on a third PRACH resource. The WTRU may determine an RA-RNTI for a second UL carrier at least in part by a carrier offset. The WTRU may monitor for a random access response (RAR) based on the RA-RNTI.