Uplink Carrier Grouping for Time Alignment in Wireless Networks
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Solution Overview
Problem
In wireless communication systems, maintaining time alignment with multiple uplink carriers is challenging due to the need for efficient synchronization and resource management across multiple carriers, particularly in LTE networks where determining synchronization and alignment status between a wireless transmit/receive unit (WTRU) and the network is resource-intensive.
Innovation Solution
The solution involves determining groups of uplink carriers that operate with a single Timing Advance (TA) and applying a TA value to specific uplink component carrier sets (UL CC sets), using a TA Command in a Random Access Response message, and managing Time Alignment Timers (TAT) to maintain alignment, with the WTRU capable of operating with multiple TAs and identifying UL CC sets based on predetermined identification or properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple uplink carriers are configured for time alignment, then communication performance and synchronization are improved, but resource consumption and system complexity increase
Solution Approach 1:
The patent segments uplink carriers into multiple sets (first set and second set) that can be managed with different timing advance values. This allows the system to handle multiple carriers efficiently by processing them in organized groups rather than individually, reducing the complexity of synchronization management while maintaining reliable time alignment across all carriers.
Solution Approach 2:
The patent introduces dynamic mechanisms including a time alignment timer that expires after a predetermined period, automatically triggering release of PUCCH resources and reconfiguration. The system dynamically adjusts timing advance values based on received commands and carrier conditions, enabling flexible adaptation to changing network requirements without manual intervention.
2Measurement precision
If multiple Timing Advance values are applied to different UL CC sets, then time alignment precision is improved, but resource management complexity increases
Solution Approach 1:
The patent divides uplink component carriers into distinct sets (first UL CC set and second UL CC set) that can be associated with different timing advance values. This segmentation enables precise time alignment for each set while managing complexity through structured organization, as each set can be independently configured and managed.
Solution Approach 2:
The patent introduces a timing advance command as an intermediary mechanism that conveys timing information from the network to the WTRU. This command structure simplifies resource management by providing a standardized way to transmit and apply timing adjustments, reducing the complexity of direct resource coordination while maintaining precise time alignment.
3Quantity of substance
If PUCCH resources are released upon time alignment timer expiry, then resource efficiency is improved, but synchronization reliability may be affected
Solution Approach 1:
The patent implements a periodic time alignment timer that continuously monitors synchronization status and triggers resource release only after a predetermined expiration period. This periodic mechanism ensures that resources are released efficiently after a reasonable duration while maintaining synchronization reliability during the active period, balancing resource consumption with communication reliability.
Solution Approach 2:
The patent establishes a feedback mechanism where the time alignment timer continuously monitors synchronization status and triggers appropriate actions (resource release or reconfiguration) based on timer expiration. This feedback loop ensures that resource management decisions are based on actual synchronization state, maintaining reliability while improving efficiency.
Data Source
AI summary
Maintaining time alignment with multiple carriers is contemplated. A group of uplink carriers (UL CC sets) that operate with a single Timing Advance (TA) may be determined, and a TA value may be applied to a specific UL CC set. A wireless transmit/receive unit's (WTRU) capability of using multiple TAs may define a group index of a few bits for each UL CC set. A TA Command received in a Random Access Response message may be used to apply the TA value to each UL carrier of the UL CC set. The WTRU may determine which UL CC set the TA value applies to based on which DL carrier the command was transmitted from. The WTRU may determine which UL CC set the TA value applies to based on the Group Index being explicitly provided in the command. The WTRU may release multi-CC configurations upon Time Alignment Timer (TAT) expiry.