Uplink Resource Selection for PHR in Multi-TTI LTE Systems
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Solution Overview
Problem
In LTE communications systems, user equipment (UE) faces challenges in sending power headroom reports (PHR) when located in cells with different TTI lengths, as existing methods do not provide a clear solution for allocating uplink resources effectively across cells with varying TTI durations.
Innovation Solution
A method where the user terminal determines a target uplink resource with the earliest start time within the maximum TTI duration and calculates power headroom reports for each cell, ensuring accurate PHR transmission by considering the sending bandwidth and maximum power limits, even when cells have different TTI lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the base station allocates uplink resources for PHR transmission in cells with different TTI lengths, then the UE can send PHR in all activated cells, but there is no clear solution for determining the target uplink resource when TTI lengths differ by at least twice
Solution Approach 1:
The patent changes the selection criterion from considering multiple factors (cell type, TTI length, resource availability) to a single parameter: earliest start time. This simplifies the resource selection process by establishing a clear time-based rule for determining the target uplink resource across cells with different TTI lengths.
Solution Approach 2:
Instead of selecting resources based on cell characteristics or scheduling priorities, the patent inverts the approach by selecting the resource with the earliest start time regardless of cell type. This reverse selection method resolves the complexity of multi-parameter decision-making.
2Measurement precision
If the UE calculates PHR for each cell separately, then accurate power headroom information is obtained for each cell, but the resource allocation becomes more complex when cells have different TTI durations
Solution Approach 1:
The patent segments the PHR calculation process by cell, calculating power headroom separately for each activated cell while maintaining a unified resource selection rule. This allows accurate per-cell PHR measurement while simplifying resource allocation through the earliest-start-time criterion.
Solution Approach 2:
The patent applies a universal resource selection rule (earliest start time) that works across all cells regardless of their TTI length or type. This multi-functional approach simplifies the allocation process while maintaining accuracy in PHR calculation for each cell.
3Productivity
If the UE sends PHR on the earliest uplink resource, then resource utilization is optimized, but the calculation of PHR for cells with shorter TTI becomes more challenging
Solution Approach 1:
The patent performs preliminary PHR calculation for all cells before selecting the target uplink resource. By calculating PHR values in advance for each cell and then applying the earliest-start-time rule, the system optimizes resource utilization while managing calculation complexity through structured preprocessing.
Data Source
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AI summary
Embodiments of the present invention provide a PHR sending method and a user terminal. The method in the embodiments of the present invention includes: receiving, by a user terminal, information about an uplink resource set, where the uplink resource set includes uplink resources in at least two cells, TTI lengths of the two cells are different, each uplink resource in the uplink resource set is an uplink resource that is located within duration of a first TTI, and the first TTI is a TTI in a cell that has a maximum TTI length and in which the user terminal is located; determining, by the user terminal, a target uplink resource, where the target uplink resource is an uplink resource that has an earliest start time and that is located within the duration of the first TTI; obtaining, by the user terminal, a power headroom report; and sending, by the user terminal, the power headroom report on the target uplink resource.