Power Headroom Reporting for Multi-Cell TDD Scheduling
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Solution Overview
Problem
The existing Power Headroom Reporting (PHR) mechanism in LTE-A systems discourages subsequent scheduling due to incomplete PH information when different TDD UL/DL configurations are used across aggregated cells, leading to inefficient scheduling and stability issues.
Innovation Solution
A method and system for power headroom reporting and subframe scheduling that determines and reports PH information for each configured and active cell, including those with different TDD UL/DL configurations, allowing for accurate PH information to be used for scheduling subsequent uplink subframes by virtualizing downlink subframes as uplink subframes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If PH information is reported only for uplink subframes in cells with different TDD configurations, then the reporting mechanism is simple, but the PH information becomes incomplete and scheduling efficiency deteriorates
Solution Approach 1:
The patent segments the PH information reporting by cell and subframe type. For cells with different TDD configurations, it separately handles uplink subframes (reporting actual PH) and downlink subframes (reporting virtual PH or padding). This segmentation allows complete PH coverage across all cells while maintaining manageable reporting structure, resolving the contradiction between simplicity and completeness for scheduling efficiency.
Solution Approach 2:
The patent introduces virtual PH calculation for downlink subframes as a preliminary action. By pre-calculating what the PH would be if the downlink subframe were treated as an uplink subframe (using virtual PUCCH/PUSCH formats), the system prepares complete PH information in advance for all cells, enabling the eNB to perform accurate uplink scheduling even when actual uplink transmissions haven't occurred yet.
2Loss of information
If PH information is reported for all configured and active cells including downlink subframes, then complete PH information is obtained, but the reporting mechanism complexity increases
Solution Approach 1:
The patent uses copying by creating virtual PH information for downlink subframes. Instead of requiring actual uplink transmissions in downlink subframes, it copies the PH calculation methodology from uplink subframes and applies it virtually to downlink subframes using virtual PUCCH/PUSCH formats. This provides complete PH information for all cells without requiring physical uplink resources in downlink subframes, balancing completeness with mechanism simplicity.
Solution Approach 2:
The patent changes the subframe type parameter from downlink to virtual uplink for PH calculation purposes. By treating downlink subframes as if they were uplink subframes (parameter change), the system can calculate and report PH information for all cells uniformly. This parameter change enables complete PH reporting while avoiding the need for complex separate handling of downlink subframes.
3Device complexity
If the same TDD configuration is used for all aggregated cells, then PH reporting is simple and complete, but the system adaptability to different frequency bands deteriorates
Solution Approach 1:
The patent introduces dynamic handling of TDD configurations in PH reporting. Instead of requiring static same-configurations across all cells, it dynamically adapts the PH reporting mechanism to each cell's actual TDD configuration. For cells with different configurations, the system dynamically determines whether to report actual PH (uplink subframes) or virtual PH (downlink subframes), enabling inter-band CA with different TDD configurations while maintaining reporting simplicity through standardized processing logic.
Data Source
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AI summary
Embodiments of the invention relate to the field of wireless communications and particularly to a method of and apparatus for power headroom reporting so as to address such a problem in the prior art that PH information is reported for only an uplink subframe and the existing PHR mechanism discourages subsequent scheduling in the case that there are different TDD UL/DL configurations for a plurality of configured and active cells aggregated for a user equipment. A method of power headroom reporting according to an embodiment of the invention includes: determining PH information of each of configured and active cells at a current instant if PH information is required to be reported, wherein the configured and active cells include a cell which is configured with a downlink subframe at the current instant; and reporting the determined PH information. Since a power headroom is reported by obtaining PH information of a configured and active cell which is currently a downlink subframe according to a virtual transmission format, the PH information facilitates subsequent scheduling by an eNB.