Uplink Timing Adjustment in UTRAN Wireless Systems
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Solution Overview
Problem
Current uplink timing adjustment methods in UMTS UTRAN, such as the TPC solution, are inefficient due to unnecessary periodic adjustments, high signaling overhead, and incompatibility with legacy UEs, and fail to effectively align uplink signals, leading to interference issues as peak data rates increase.
Innovation Solution
The NodeB determines which UEs need uplink timing adjustments by calculating the difference between estimated and ideal reception times, initiating adjustments only when necessary to avoid transmission time interval overlap, using existing signaling protocols to request and implement timing adjustments directly or indirectly through the RNC or High Speed Downlink Packet Access channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If periodic timing adjustment commands are sent to all UEs, then timing alignment is maintained, but signaling overhead increases unnecessarily
Solution Approach 1:
The patent applies local quality by sending timing adjustment commands selectively only to specific UEs that require adjustment, rather than periodically to all UEs. The NodeB determines which UEs need adjustment based on their individual timing status, thereby maintaining timing alignment reliability while significantly reducing unnecessary signaling overhead.
Solution Approach 2:
The patent implements partial action by sending timing adjustment commands only when and where needed, rather than applying a blanket periodic adjustment to all UEs. This partial approach sends exactly the right amount of signaling - no more, no less - thereby optimizing the balance between maintaining timing alignment and minimizing overhead.
2Object-generated harmful factors
If larger time adjustments are made to avoid TTI overlapping, then interference is reduced, but adjustment time increases
Solution Approach 1:
The patent applies preliminary action by having the NodeB continuously monitor and estimate the reception time of UE signals in advance. This allows the NodeB to detect timing deviations before they cause TTI overlapping or significant interference, enabling proactive timing adjustments that prevent problems rather than correcting them after they occur.
Solution Approach 2:
The patent implements feedback by having the NodeB estimate the reception time of UE signals and use this information to determine when timing adjustment is needed. This continuous feedback loop allows the system to make timely, targeted adjustments that prevent interference while minimizing adjustment time by acting only when necessary.
3Reliability
If TPC solution is used for timing adjustment, then orthogonality is improved, but compatibility with legacy UEs is lost
Solution Approach 1:
The patent applies universality by using a timing adjustment mechanism that is compatible with both legacy UEs and modern UEs. The NodeB sends timing adjustment commands using existing signaling protocols that legacy UEs can interpret, while still achieving the orthogonality improvements needed for modern high-rate data transmissions. This universal approach maintains backward compatibility while enabling advanced timing control.
4Reliability
If timing adjustment is sent to all UEs periodically, then worst-case scenarios are covered, but resources are wasted in normal scenarios
Solution Approach 1:
The patent applies local quality by sending timing adjustment commands selectively only to specific UEs that require adjustment, rather than periodically to all UEs. The NodeB determines which UEs need adjustment based on their individual timing status, thereby maintaining timing alignment reliability while significantly reducing unnecessary signaling overhead.
Solution Approach 2:
The patent implements partial action by sending timing adjustment commands only when and where needed, rather than applying a blanket periodic adjustment to all UEs. This partial approach sends exactly the right amount of signaling - no more, no less - thereby optimizing the balance between maintaining timing alignment and minimizing overhead.
Data Source
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AI summary
The present invention relates to methods and arrangements that enable uplink timing adjustment in a UTRAN while minimizing the signalling overhead. This is achieved by a solution where the information about the estimated reception time is used by the NB to determine whether the UEs need to be time adjusted on the UL in order to avoid TTI overlapping and thus interference. The estimated reception time of a UE UL signal is compared with an ideal reception time (the reference time) which can be defined based on the overall knowledge of the estimated reception times. If the difference between the estimated and the ideal reception time is larger than a pre-defined threshold value, meaning that the overlapping with some other UEs TTI will be big, a timing adjustment is initiated.