Uplink Grant Handling via HARQ Process Verification
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Solution Overview
Problem
In the LTE wireless communication system, contention between user equipment (UE) during random access procedures leads to misuse of uplink grants, causing collisions and inefficient use of radio resources, as contention losers continue to use the same Temporary C-RNTI to monitor PDCCH, potentially receiving and misusing uplink grants intended for contention winners.
Innovation Solution
A method and apparatus for handling uplink grants in a UE, where a Temporary C-RNTI is set to a value assigned in a Random Access Response message, and the UE monitors a Contention Resolution message to determine if the uplink grant corresponds to a different HARQ Process or has a different Transport Block size than initially provided, preventing data transmission when mismatches are detected to avoid misusing uplink grants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE continues to use the Temporary C-RNTI to monitor PDCCH after receiving an uplink grant, then the UE can receive downlink control information, but the UE may misuse the uplink grant for transmission causing collisions
Solution Approach 1:
The patent implements a feedback mechanism where the UE monitors the Contention Resolution message and compares the HARQ process number and Transport Block size from the received uplink grant with the expected values. If mismatches are detected, the UE generates a feedback indication to discard the uplink grant, preventing misuse while maintaining reliable communication for legitimate grants.
Solution Approach 2:
The patent performs preliminary verification of the uplink grant parameters (HARQ process number and Transport Block size) against the expected values before the UE actually transmits data. This preliminary action prevents the harmful effect of using incorrect uplink grants for transmission, thereby avoiding collisions with other UEs.
2Adaptability or versatility
If the UE monitors PDCCH for uplink grants during random access procedure, then the UE can receive downlink control information, but contention losers may receive and misuse uplink grants intended for contention winners
Solution Approach 1:
The patent uses the Contention Resolution message as a feedback mechanism that provides verification information about the uplink grant parameters. The UE compares the received HARQ process number and Transport Block size with the expected values, and only uses the uplink grant if the parameters match, thereby preventing resource waste while maintaining the ability to receive downlink control information.
Solution Approach 2:
The patent changes the verification parameters from simply checking C-RNTI match to also verifying HARQ process number and Transport Block size. This parameter expansion ensures that even if a contention loser receives the same C-RNTI, it cannot misuse the uplink grant because the additional parameter verification will fail.
3Device complexity
If multiple UEs use the same Random Access Preamble, then the random access procedure can be simplified, but contention occurs causing inefficient use of radio resources
Solution Approach 1:
The patent implements a feedback mechanism through the Contention Resolution message that provides verification information about the uplink grant parameters. The UE compares the received HARQ process number and Transport Block size with the expected values, and only uses the uplink grant if the parameters match, thereby preventing resource waste while maintaining the ability to receive downlink control information.
Solution Approach 2:
The patent extracts the verification function from the basic random access procedure by introducing separate verification steps that check HARQ process number and Transport Block size against expected values. This extraction allows the system to maintain simple random access procedures while adding a verification layer that prevents contention losers from misusing uplink grants, thereby improving radio resource utilization efficiency.
Data Source
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AI summary
A method for handling an uplink grant received on a physical downlink control channel (PDCCH) in a user equipment (UE) of a wireless communication system is disclosed. The method includes steps of setting a Temporary Cell Radio Network Temporary Identifier (Temporary C-RNTI) of the UE to a value assigned in a Random Access Response message, monitoring a contention resolution message, receiving an uplink grant on PDCCH addressed to the Temporary C-RNTI, and not using the uplink grant to transmit data if the uplink grant corresponds to a Hybrid Automatic Repeat Request (HARQ) Process different from an HARQ Process used for transmission of a Medium Access Control (MAC) Protocol Data Unit (PDU) in a Message 3 buffer.