Uplink Synchronization via Contention Resolution Timer
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Solution Overview
Problem
In wireless communication systems, particularly in contention-based random access procedures, uplink synchronization is challenging due to the possibility of random access failures caused by contention between user equipment (UE) using the same random access preamble, leading to incorrect time alignment and potential interference.
Innovation Solution
A method for performing uplink synchronization involves transmitting a randomly selected random access preamble, receiving a random access response with a time alignment value, starting a time alignment timer, and initiating a contention resolution timer. If contention is unsuccessful, the time alignment timer is stopped to prevent incorrect synchronization and potential interference, allowing for retrying the random access procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a random access preamble is randomly selected for contention-based random access procedure, then the ease of operation is improved, but the reliability deteriorates due to possible contention and random access failure
Solution Approach 1:
The patent implements feedback mechanisms where the base station sends random access responses and contention resolution messages to inform UEs about the success or failure of their random access attempts. The UE monitors for specific messages and adjusts its behavior based on whether contention resolution is successful, creating a closed-loop feedback system that improves reliability while maintaining the random selection approach.
Solution Approach 2:
The patent establishes preliminary conditions and procedures before attempting random access, including selecting random access preambles from specific groups (A or B) based on path loss thresholds, and configuring time alignment timers in advance. These preliminary actions prepare the system to handle contention scenarios more effectively while maintaining operational simplicity.
2Duration of action of moving object
If the time alignment timer is continuously running after receiving random access response, then the duration of action is improved, but the object-generated harmful factors worsen due to potential interference from incorrect synchronization
Solution Approach 1:
The patent makes the time alignment timer dynamic by configuring different timer values based on the random access group (A or B) and adjusting the timer behavior based on contention resolution outcomes. The timer is started or restarted only when appropriate, and its duration is adapted to the specific random access scenario, preventing both premature expiration and excessive duration that could cause interference.
Solution Approach 2:
The patent treats the time alignment timer as a temporary, disposable resource that is started only when needed for a specific random access attempt and is discarded (stopped or expired) when contention resolution fails or succeeds. This approach avoids the harm of continuously running timers with incorrect synchronization while maintaining synchronization when valid.
3Productivity
If uplink transmission is allowed when time alignment timer is running, then the productivity is improved, but the reliability deteriorates when the timer is running with incorrect synchronization
Solution Approach 1:
The patent uses feedback from the base station's random access response and contention resolution messages to determine whether uplink transmission should be allowed. The UE monitors for successful contention resolution before enabling uplink transmission with the received time alignment value, ensuring that productivity is maintained only when synchronization reliability is confirmed.
Solution Approach 2:
The patent requires preliminary successful contention resolution before allowing uplink transmission with the time alignment timer running. This preliminary verification step ensures that the UE has valid synchronization information before engaging in uplink transmission, preventing reliability issues while maintaining productivity when conditions are met.
Data Source
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AI summary
Method and user equipment UE for performing uplink synchronization in a wireless communication system, the method comprising: transmitting a random access preamble from a user equipment UE to a network; receiving at the UE a random access response from the network, the random access response comprising a temporary UE identifier and a time alignment value for uplink synchronization with the network; starting a time alignment timer in the UE responsive to receiving of the time alignment value; determining whether contention resolution is successful between the UE and the network; and stopping the time alignment timer in the UE if the contention resolution is not successful.