Two-Step Random Access Method for 5G Wireless Latency Reduction
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G networks, face challenges in efficiently performing random access procedures due to increased complexity and latency, especially in scenarios requiring low latency and high reliability like IoT applications.
Innovation Solution
A two-step random access method is introduced, where user equipment (UE) transmits a first message including a MAC PDU with a common control channel SDU or C-RNTI, and the base station (BS) responds with a second message within a configured time window, allowing for successful determination of the random access procedure's success based on specific criteria, such as contention resolution identity matches or uplink grants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional four-step random access procedure is used, then the random access process is more robust and reliable, but the latency and complexity of the access procedure increases
Solution Approach 1:
The patent combines multiple random access messages into fewer transmission steps. Specifically, it merges the traditional four-step random access procedure (Msg1, Msg2, Msg3, Msg4) into a two-step procedure by combining Msg3 and Msg4 into a single uplink message, and combining Msg1 and Msg2 into a single downlink message. This merging reduces the number of round-trip transmissions, thereby reducing latency while maintaining access reliability through integrated acknowledgment and data transmission in the combined messages.
Solution Approach 2:
The patent segments the random access procedure into distinct phases with clear success criteria. It divides the procedure into an initial access phase (Msg1/Msg2 exchange) and a data transmission phase (combined Msg3/Msg4). The segmentation allows the system to determine access success earlier in the process based on whether the combined downlink message contains an acknowledgment, thereby reducing overall latency while maintaining reliability through structured message phases.
2Loss of time
If a two-step random access procedure is implemented, then the latency and complexity are reduced, but the reliability and robustness of the access procedure may be compromised
Solution Approach 1:
The patent combines multiple functions into single messages to maintain reliability despite reduced steps. The combined downlink message (replacing Msg2, Msg3, Msg4) integrates acknowledgment of the random access preamble, uplink resource allocation, and data transmission confirmation. The combined uplink message (replacing Msg3 and Msg4) includes both data transmission and acknowledgment components. This merging ensures that all critical reliability functions are preserved in fewer steps.
Solution Approach 2:
The patent creates multi-functional messages that perform multiple roles simultaneously. The combined downlink message serves as both an acknowledgment of received data and a grant for uplink transmission, while also confirming random access success. The combined uplink message functions as both data transmission and access confirmation. This multi-functionality maintains system reliability by ensuring all necessary control functions are embedded within the reduced message set.
3Reliability
If more messages are exchanged in the random access procedure, then the reliability and completeness of information transfer is improved, but the procedure complexity and processing overhead increases
Solution Approach 1:
The patent merges multiple sequential messages into two combined messages, reducing procedure complexity while preserving information completeness. The combined downlink message integrates acknowledgment, resource allocation, and data confirmation that were previously distributed across three separate messages (Msg2, Msg3, Msg4). The combined uplink message merges data transmission and access confirmation from two messages (Msg3, Msg4). This merging reduces the number of protocol states and processing steps required.
Solution Approach 2:
The patent employs universal messages that handle multiple protocol functions simultaneously, reducing overall procedure complexity. The combined downlink message universally handles acknowledgment, resource grant, and data confirmation functions that previously required separate message handling. The combined uplink message universally handles data transmission and access success indication. This multi-functionality reduces the complexity of message routing, state management, and protocol processing.
Data Source
AI summary
A random access method in a wireless communication system and an apparatus therefor are provided. A method for performing two-step random access in user equipment (UE) includes transmitting a first message to a base station (BS), the first message including a medium access control (MAC) packet data unit (PDU) that includes a common control channel (CCCH) service data unit (SDU) or a cell radio network temporary identifier (C-RNTI), and a random access preamble, monitoring a physical downlink control channel (PDCCH) for a second message from the BS within a configured time window, the second message corresponding to the first message, and determining whether the two-step random access is successful based on a result of the monitoring.