Two-Step Random Access With Preamble-Mapped Uplink Data
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing four-step random access procedure in wireless communication systems introduces unacceptable levels of latency and signaling overhead, particularly in unlicensed spectrum, and may fail due to channel unavailability, necessitating improvements for reduced latency and signaling overhead.
Innovation Solution
A two-step random access procedure is introduced, where the first step transmission includes a random access preamble that also serves as a grant-free data transmission, with the preamble mapped to uplink data channel resources, allowing for direct data transmission without dynamic scheduling, and enabling a seamless switch to four-step procedures when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a four-step random access procedure is used, then the access procedure is reliable and compatible with legacy UEs, but the latency and signaling overhead become unacceptable
Solution Approach 1:
The patent segments the traditional four-step random access procedure into a simplified two-step procedure by combining message 3 and message 4 transmissions into a single uplink message (MsgA), and combining message 2 and message 3 receptions into a single downlink message (MsgB). This segmentation reduces the number of signaling exchanges from four to two, directly reducing access latency while maintaining reliability through the same fundamental random access mechanism.
Solution Approach 2:
The patent merges multiple message functions into fewer transmissions. Specifically, the uplink message combines the random access preamble, uplink data, and uplink control information into a single MsgA transmission. The downlink message combines the random access response, contention resolution, and scheduling information into a single MsgB transmission. This merging eliminates intermediate signaling steps and reduces overall access latency.
2Reliability
If a four-step random access procedure is used, then the procedure is thorough and reliable, but the signaling overhead becomes excessive
Solution Approach 1:
The patent combines multiple signaling functions into consolidated messages. MsgA merges the random access preamble, uplink data payload, and uplink control information into a single transmission, eliminating the need for separate message 3 and message 4 transmissions. MsgB consolidates the random access response, contention resolution identifier, and scheduling assignments into one downlink message, reducing the total number of signaling exchanges and overhead.
Solution Approach 2:
The patent creates multi-functional messages that perform multiple roles simultaneously. MsgA serves as both the random access preamble and the uplink data transmission, eliminating the need for separate data channel transmissions in the traditional four-step procedure. MsgB functions as both the random access response and the contention resolution message, reducing signaling overhead by consolidating multiple functions into fewer messages.
3Productivity
If grant-free data transmission is implemented, then latency is reduced and efficiency is improved, but compatibility with legacy UEs and systems becomes challenging
Solution Approach 1:
The patent implements dynamic adaptability by allowing the network to configure different random access procedures based on UE capabilities and service requirements. The system can dynamically select between the two-step grant-free procedure for capable UEs requiring low latency and the traditional four-step procedure for legacy UEs or scenarios where grant-based transmission is preferred. This dynamic configuration enables the system to adapt to different UE types and service conditions.
Solution Approach 2:
The patent changes the procedural parameters of the random access mechanism by introducing configurable message structures and transmission formats. The network can parameterize the random access procedure to support both two-step and four-step formats, adjusting parameters such as message timing, resource allocation, and transmission formats based on UE capability indicators. This parameter flexibility enables seamless support for both grant-free and grant-based transmissions across different UE types.
Data Source
AI summary
Systems and methods for two-step random access procedure are described. According to embodiments, a user equipment (UE) transmits a random access preamble on a random access channel. The UE also transmits data on an uplink data channel using a particular uplink data channel resource. The particular uplink data channel resource is selected by the UE based on the random access preamble.