5G NR RACH Msg3 Repetition and Frequency Hopping
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Solution Overview
Problem
In 5G NR wireless communications, the random access channel (RACH) procedure lacks support for message 3 (Msg3) repetitions and frequency hopping, which affects the reliability of initial transmissions between user equipment (UE) and the next generation Node-B (gNB).
Innovation Solution
The UE and gNB determine the number of repetitions and frequency hopping (FH) type and pattern for Msg3 transmissions based on system information block (SIB) and downlink control information (DCI) transmissions, repurposing reserved bits in the UL grant to indicate these parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Msg3 transmissions are transmitted without repetitions and frequency hopping, then the device complexity and protocol overhead are kept simple, but the reliability of initial transmissions between UE and gNB deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the RACH procedure parameters to include Msg3 repetitions and frequency hopping. The base station configures repetition factors and frequency hopping patterns through system information blocks and downlink control information, transforming the original single-transmission parameter set into a multi-parameter configuration that enables reliable repeated transmissions with frequency diversity.
Solution Approach 2:
The patent implements dynamics by making the Msg3 transmission configuration adaptive rather than static. The number of repetitions and frequency hopping parameters are dynamically determined based on channel conditions, UE capability, and network configuration, allowing the system to optimize reliability while managing complexity through conditional parameter selection.
2Reliability
If Msg3 transmissions use repetitions and frequency hopping, then the reliability of initial transmissions is improved, but the protocol complexity and signaling overhead increase
Solution Approach 1:
The patent applies preliminary action by pre-configuring Msg3 repetition and frequency hopping parameters through system information blocks before the actual RACH procedure. The base station prepares and transmits configuration information including repetition factors and frequency hopping patterns in advance, so that when Msg3 transmissions occur, the UE can immediately apply the predetermined parameters without real-time negotiation, reducing signaling overhead during the critical access phase.
3Reliability
If the number of Msg3 repetitions is increased, then the reliability of transmission is improved, but the transmission time and access delay increase
Solution Approach 1:
The patent applies partial action by implementing a configurable number of Msg3 repetitions rather than requiring a fixed large number of transmissions. The system transmits Msg3 with a repetition factor that is sufficient to achieve the required reliability threshold but not excessive, allowing the UE to complete the access procedure with an optimized number of transmissions that balances reliability improvement against access delay.
Data Source
AI summary
A user equipment (UE) is configured to receive message 3 (Msg3) transmissions. The UE receives a system information block (SIB) transmission from a base station of a wireless network, receives a downlink control information (DCI) transmission scheduling a message 2 (Msg2) transmission from the base station, receives the Msg2 transmission including an uplink (UL) grant for a message 3 (Msg3) initial transmission from the base station, determines the number of repetitions for the Msg3 initial transmission based on at least one of the SIB transmission, the DCI transmission, and the Msg2 transmission and determines a frequency hopping (FH) type and FH pattern based on at least one of the SIB transmission, the DCI transmission, and the Msg2 transmission.