Random Access Procedure State Alignment in NB-IoT
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Solution Overview
Problem
In NB-IoT, mismatches in the states of user apparatus and base station apparatus regarding contention-based and non-contention-based random access procedures lead to incomplete random access procedures, as the base station assumes a contention-based procedure while the user apparatus performs a non-contention-based procedure, resulting in failed communications.
Innovation Solution
Introducing a 'CF' field in the MAC payload of the random access response to indicate whether the response corresponds to a non-contention or contention-based random access procedure, and modifying the preamble sub-carrier selection process to ensure alignment between the base station and user apparatus states, allowing proper completion of the random access procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the base station apparatus transmits an indication for non-contention based random access procedure, then the user apparatus can perform non-contention based random access, but the base station apparatus may assume contention based procedure resulting in state mismatch and procedure failure
Solution Approach 1:
The patent applies feedback by having the user apparatus transmit a random access response that includes a CF field indicating whether the response corresponds to non-contention based or contention based procedure. This feedback mechanism ensures that the base station apparatus can accurately determine the procedure type and adjust its behavior accordingly, preventing state mismatches and ensuring reliable procedure completion.
Solution Approach 2:
The patent segments the random access response into distinct components, including the CF field that specifically indicates the procedure type. This segmentation allows the base station apparatus to process and interpret the procedure type information separately from other response parameters, enabling accurate state alignment between transmitter and receiver.
2Speed
If the user apparatus performs non-contention based random access procedure, then the access speed is improved, but the base station apparatus may not properly recognize the procedure type leading to resource mismatch
Solution Approach 1:
The CF field in the random access response serves as feedback that explicitly conveys the procedure type information to the base station apparatus. This ensures that even though the user apparatus performs non-contention based access at high speed, the base station receives and processes the necessary procedure type information to maintain proper resource allocation and recognition.
3Device complexity
If the base station apparatus uses contention based random access procedure, then the procedure is simpler to implement, but the user apparatus may perform non-contention based procedure resulting in state mismatch
Solution Approach 1:
The patent uses the CF field as feedback to inform the base station apparatus about the actual procedure type used by the user apparatus. This feedback mechanism allows the base station to maintain simple implementation while achieving reliable state alignment, as the CF field explicitly indicates whether non-contention or contention based procedure was performed.
Solution Approach 2:
The patent changes the parameter state by introducing the CF field as a new indicator in the random access response. This parameter change enables the base station apparatus to distinguish between different procedure types and adjust its behavior accordingly, resolving the state mismatch issue while maintaining implementation simplicity.
Data Source
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AI summary
A user apparatus that communicates with a base station apparatus is provided. The user apparatus includes a reception unit configured to receive, from the base station apparatus, an indication for an individual random access preamble, information indicating correspondence to non-contention based random access procedure, and a random access response; a transmission unit configured to transmit the individual random access preamble to the base station apparatus; and a control unit configured to, in response to receiving the random access response to the individual random access preamble, the random access response being transmitted from the base station apparatus, determine whether the random access procedure has been successfully completed based on the information indicating correspondence to the non-contention based random access procedure.