Early Data PDU Rebuilding for NB-IoT CE Level Changes
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Solution Overview
Problem
In NB-IoT technology, when a user equipment fails to transmit Msg3 during a random access procedure due to changing coverage enhancement levels, the stored data no longer fits the new uplink grant, leading to inefficiencies and potential retransmission failures.
Innovation Solution
The user equipment adjusts the Transport Block Size (TBS) by removing padding or adding headers to ensure the PDU fits the new CE level's uplink grant, allowing successful retransmission of early data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the user equipment changes the coverage enhancement level to improve signal coverage, then the transmission reliability is improved, but the stored Msg3 protocol data unit no longer fits the new uplink grant, causing retransmission failure
Solution Approach 1:
The patent makes the PDU structure dynamic by allowing it to be rebuilt when CE level changes occur. Instead of using a static PDU format, the system dynamically reconstructs the PDU with appropriate padding and subheaders based on the new CE level's uplink grant requirements, enabling successful retransmission across different coverage conditions
Solution Approach 2:
The patent changes the parameters of the PDU (specifically the MAC subheader structure and padding) to match the new CE level. When the CE level changes, the system modifies the PDU parameters including adding necessary subheaders and adjusting padding to ensure compatibility with the new uplink grant size and structure
2Reliability
If the user equipment adds padding and subheaders to fit the PDU to the new uplink grant, then the retransmission success rate is improved, but the data transmission efficiency decreases due to increased overhead
Solution Approach 1:
The patent applies partial action by adding only the minimum necessary padding and subheaders required to fit the PDU to the new uplink grant. Rather than over-padding or using excessive overhead structures, the system calculates and adds precisely the amount of padding needed to match the grant size, minimizing efficiency loss while ensuring successful transmission
3Reliability
If the user equipment retransmits the Msg3 PDU after changing CE level, then the early data transmission capability is maintained, but the power consumption increases due to additional processing and retransmission
Solution Approach 1:
The patent performs preliminary actions by detecting CE level changes before retransmission and proactively rebuilding the PDU with appropriate padding and subheaders. This preliminary preparation prevents transmission failures and avoids the need for multiple retransmission attempts, thereby reducing overall power consumption despite the initial processing overhead
Data Source
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AI summary
Various communication systems may benefit from improved random access procedures. For example, it may be helpful to improve random access procedure when changing a coverage enhancement level. A method, according to certain embodiments, may include changing a coverage enhancement level in response to a failure of a random access procedure. The method may also include determining whether early data transmission may be initiated in the changed coverage enhancement level. In addition, the method may include building at a user equipment a protocol data unit corresponding to the changed coverage enhancement level when the early data transmission is initiated in the changed coverage enhancement level. Further, the method may include transmitting the early data from the user equipment to a network entity in the built packet data unit on the changed coverage enhanced level.