Two-Step Random Access Signaling With Transport Block Size Scaling
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Solution Overview
Problem
The traditional four-step random access channel (RACH) procedure in wireless communication systems, such as 5G NR, leads to high latency, which is a bottleneck for efficient and fast communication setups.
Innovation Solution
Implementing a two-step RACH process that merges the contents of msg1 and msg3 into msgA and msg2 and msg4 into msgB, with msgB incorporating downlink control information (DCI) to include a field indicating transport block size scaling, using a new RNTI (msgB-RNTI) for efficient contention resolution and reduced latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a traditional four-step random access procedure is used, then the access process is reliable and complete, but the initial access latency is high
Solution Approach 1:
The patent merges the traditional four-step random access procedure into a two-step procedure by combining step 1 (preamble transmission) and step 3 (data transmission) into a single uplink message (msgA), and combining step 2 (random access response) and step 4 (contention resolution) into a single downlink message (msgB). This merging reduces the number of interaction steps from four to two, directly reducing initial access latency while maintaining the essential functions of the random access procedure.
2Loss of time
If the transport block size is scaled down, then the payload capacity is reduced, but the message length is shortened reducing latency
Solution Approach 1:
The patent introduces a transport block size scaling mechanism that dynamically adjusts the payload capacity based on the message type and content requirements. For msgB (downlink response message), the transport block size can be scaled down compared to traditional messages, reducing the message length and transmission time. The scaling factor is determined by the network device based on the actual data needs, allowing flexible adaptation between payload capacity and transmission speed.
3Loss of time
If a two-step random access procedure is implemented, then the initial access latency is reduced, but the message structure complexity increases
Solution Approach 1:
The patent segments the random access procedure into two distinct message exchanges (msgA and msgB) with clearly defined structures and functions. msgA contains the preamble and uplink data, while msgB contains the random access response and contention resolution information. This segmentation approach simplifies the overall structure compared to four separate steps, making each message self-contained with specific purposes, thereby reducing processing complexity despite reducing the number of steps.
Solution Approach 2:
The two-step random access messages are designed to perform multiple functions within each exchange. msgA simultaneously serves as both the preamble transmission and the uplink data transmission, while msgB simultaneously provides the random access response and contention resolution. This multi-functionality reduces the number of separate messages needed, simplifying the overall procedure structure while achieving the same goals as the four-step procedure.
Data Source
AI summary
A wireless communication method is provided to include: sending, by a user device, a first message to a network device in a wireless network to initiate a 2-step random access to the wireless network; and receiving, in response to the first message, a second message to perform the 2-step random access, the second message including a field indicating whether a transport block size of a payload of the second message is scaled.