Supplementary Uplink Access via Carrier Switching After PRACH Failure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently establishing uplink access when initial random access attempts fail, leading to suboptimal resource utilization and increased latency.
Innovation Solution
A WTRU transmits a random access preamble on multiple uplink carriers, switching between carriers if initial attempts fail, and determines an RA-RNTI based on carrier offsets to enhance access success.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a WTRU transmits random access preambles on multiple uplink carriers with switching mechanisms, then uplink access reliability is improved, but device complexity increases
Solution Approach 1:
The patent divides the uplink access process into multiple segments by implementing separate random access procedures on different uplink carriers (first UL carrier and second UL carrier). When access fails on the first carrier, the WTRU segments the retry attempts across carriers, with each carrier having its own counter (first counter and second counter) to track failures independently. This segmentation allows the system to maintain reliability through multiple independent access paths while managing complexity through structured organization.
Solution Approach 2:
The patent implements dynamic carrier switching based on real-time access success feedback. The WTRU dynamically selects which uplink carrier to use for random access transmissions based on whether previous attempts succeeded or failed. This dynamic adaptation allows the system to respond to changing channel conditions and network responses, improving reliability by automatically switching to alternative carriers when needed, while the dynamic nature prevents the system from becoming statically complex.
2Device complexity
If a WTRU attempts random access on a single uplink carrier with maximum retry limits, then device complexity is reduced, but access latency increases
Solution Approach 1:
The patent adds a new dimension to the random access retry process by introducing a second uplink carrier as an additional spatial/frequency dimension for access attempts. Instead of simply increasing the number of retries on a single carrier (one-dimensional approach), the system transitions to a two-dimensional approach where retries can occur on either the first UL carrier or the second UL carrier. This dimensional expansion reduces latency by providing parallel access paths while maintaining manageable device complexity through structured carrier selection rules.
Solution Approach 2:
The patent implements preliminary configuration of multiple uplink carriers and their associated random access parameters before actual access is needed. The WTRU is pre-configured with information about both the first and second UL carriers, including their respective PRACH resources and counter settings. This preliminary preparation ensures that when access failure occurs, the WTRU can immediately switch to an alternative carrier without additional configuration delays, thereby reducing access latency while keeping the switching mechanism relatively simple.
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.