Two-Step Random Access Procedure for 5G IoT Delay Reduction
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Solution Overview
Problem
The existing contention-based random access (CBRA) procedure in wireless communication systems, such as LTE, suffers from high delay in transitioning from an idle to a connected state, which is not sufficient to meet the next generation radio access technology's requirement of a 10ms delay.
Innovation Solution
A two-step contention-based random access (RA) procedure is introduced, where the user equipment (UE) transmits a random access channel (RACH) preamble and a UE ID in a single physical layer protocol data unit, followed by a response from the base station (BS) that includes timing advance and UE ID confirmation. Additionally, a fall-back mechanism from two-step to four-step RA procedure is implemented when additional information is not successfully decoded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a traditional four-step contention-based random access procedure is used, then the procedure is reliable and well-established, but the idle to connected state transition delay is 29.5 TTIs which exceeds the 10ms requirement
Solution Approach 1:
The patent segments the traditional four-step random access procedure into a compressed two-step procedure by combining MSG1 and MSG3 into a single uplink transmission, and combining MSG2 and MSG4 into a single downlink transmission. This segmentation reduces the number of interaction steps from four to two, directly reducing the transition delay from 29.5 TTIs to meet the 10ms requirement while maintaining reliability through fallback mechanisms.
Solution Approach 2:
The patent merges multiple message exchanges into fewer transmissions. Specifically, the UE combines the random access preamble (MSG1) and additional information (MSG3) into a single uplink transmission to the base station. The base station combines the random access response (MSG2) and contention resolution message (MSG4) into a single downlink transmission. This merging reduces the number of round-trip delays and achieves the required 10ms transition time.
2Productivity
If a two-step random access procedure is implemented to reduce delay, then the transition delay meets the 10ms requirement, but the procedure complexity increases and fallback mechanisms are needed
Solution Approach 1:
The patent implements a dynamic random access procedure that can adapt between two-step and four-step modes based on decoding success. When the base station successfully decodes the combined MSG1/MSG3 transmission, the procedure completes in two steps for high efficiency. When decoding fails, the system dynamically falls back to the traditional four-step procedure, ensuring reliability while maintaining the option for high productivity when conditions permit.
Solution Approach 2:
The patent introduces an intermediary fallback mechanism that mediates between the simplified two-step procedure and the robust four-step procedure. The base station acts as an intermediary by determining whether to accept the compressed two-step transmission or trigger a fallback to four steps based on decoding results. This intermediary mechanism manages the complexity trade-off by providing a clear escalation path when the simplified procedure fails.
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AI summary
A communication method and system for converging a fifth generation (5G) communication system for supporting higher data rates beyond a fourth generation (4G) system with a technology for Internet of things (IoT) are provided. The communication method and system may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method of a user equipment (UE) for performing a random access (RA) procedure is provided. The method includes transmitting a first message including a RA preamble and a UE identifier (ID) to a base station (BS), and receiving a second message including a sequence index of the RA preamble from the BS.