2-Step RACH Incremental Redundancy for Reliable Random Access
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Solution Overview
Problem
The existing 2-step RACH process in wireless communication systems faces challenges in retransmission reliability and latency due to complex failure scenarios, such as message 1 and message 3 not being received correctly, requiring improved retransmission policies.
Innovation Solution
Implementing an incremental redundancy manner for retransmitting data using different redundancy versions and power ramping strategies to enhance reliability and reduce latency in the random access procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If incremental redundancy with different redundancy versions is used for retransmission, then data transmission reliability is improved, but system complexity increases
Solution Approach 1:
The data transmission process is segmented into multiple transmissions, each carrying different redundancy versions (RV0, RV1, RV2, RV3). The original data is divided into code blocks, and each retransmission sends a different segment of redundancy information, allowing the receiver to progressively reconstruct the original data with increased reliability.
Solution Approach 2:
Redundancy versions are pre-configured and prepared in advance according to the cyclic redundancy check (CRC) result. The system预先 determines which redundancy version to send based on the initial transmission outcome, enabling efficient retransmission without real-time computation delays.
2Reliability
If power ramping strategy is implemented for retransmission, then transmission reliability is improved, but energy consumption increases
Solution Approach 1:
The transmission power is dynamically adjusted based on the retransmission scenario. The power ramping strategy implements dynamic power control where the transmit power is increased progressively with each retransmission attempt, adapting to the channel conditions and ensuring reliable delivery while minimizing unnecessary energy consumption.
Solution Approach 2:
The transmit power parameter is changed according to the retransmission count and channel quality. The system modifies the power level from the initial transmission through subsequent retransmissions, optimizing the balance between reliability and energy efficiency by adjusting this critical parameter based on actual transmission needs.
3Loss of time
If 2-step RACH is used instead of 4-step RACH, then access latency is reduced, but retransmission complexity increases
Solution Approach 1:
The 2-step RACH merges the random access preamble transmission and the uplink data transmission into a single message (MsgA), combining functions that were previously separated in the 4-step procedure. This consolidation reduces the number of interaction steps between terminal and network, thereby reducing access latency while managing retransmission complexity through unified handling.
Solution Approach 2:
Message A serves multiple functions simultaneously: it acts as both the random access preamble and the uplink data carrier. This multi-functional design eliminates the need for separate message exchanges, reducing the overall access time while the system manages the inherent complexity through standardized retransmission protocols for MsgA.
Data Source
AI summary
This application discloses a communications method and apparatus. The method includes: sending, by a terminal device, a first message to a network device, where the first message includes a first random access preamble and first data, and a first redundancy version is used for the first data; and determining, by the terminal device, that the first data fails to be sent, and retransmitting the first data, where a second redundancy version is used for the first data. The corresponding communications apparatus is further disclosed. An incremental redundancy manner is used in a retransmission procedure of random access data.