Dynamic Downlink Power Allocation for Higher Order Modulation
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Solution Overview
Problem
In wireless communication systems, particularly in LTE, high-order modulation (HOM) support for wireless devices is hindered by the need for cleaner radio channel conditions and sufficient power headroom, which can lead to increased costs and reduced cell coverage due to the requirement for advanced radios with low Error Vector Magnitude (EVM) tolerance, and may result in higher Block Error Rates (BLER) if not adequately managed.
Innovation Solution
A method and network entity that dynamically adjust power allocation by determining legacy and HOM mode power offset values to enable HOM mode support for HOM-capable wireless devices, switching between HOM and legacy modulation modes based on channel quality and distance from the network entity, and scheduling power resources to maintain low EVM and BLER, thereby allowing 256 QAM usage without impacting other devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If advanced modulation (256 QAM) is used to increase throughput, then data throughput is improved, but Error Vector Magnitude (EVM) tolerance requirements worsen (need cleaner radio channel conditions)
Solution Approach 1:
The patent changes the power allocation parameters dynamically by introducing mode-specific power offset values (legacy mode power offset and HOM mode power offset). The network entity determines which power offset to apply based on the wireless device's operating mode, thereby adjusting the transmission parameters to match the modulation scheme being used and resolving the EVM tolerance issue while maintaining high throughput.
2Reliability
If power headroom is increased to achieve low EVM, then EVM performance is improved, but cell coverage is reduced
Solution Approach 1:
The patent applies different power offset values locally depending on the operating mode. When HOM mode is active, a HOM mode power offset (which is lower) is applied, allowing better EVM performance. When legacy mode is active, a legacy mode power offset (which is higher) is applied, ensuring adequate coverage. This local differentiation resolves the contradiction between EVM performance and cell coverage.
3Productivity
If HOM mode is enabled for all wireless devices, then throughput is improved, but devices with legacy radios experience higher BLER
Solution Approach 1:
The patent implements dynamic mode switching capability where the network entity can switch wireless devices between HOM mode and legacy mode based on their capabilities and channel conditions. This dynamic adaptation ensures that legacy radios operate in legacy mode with appropriate power offsets to maintain low BLER, while capable devices can utilize HOM mode for high throughput.
4Adaptability or versatility
If mode switching between HOM and legacy is implemented, then adaptability to channel conditions is improved, but system complexity increases
Solution Approach 1:
The patent utilizes feedback mechanisms where the network entity receives information about wireless device capabilities and channel conditions, then determines the appropriate mode and power offset. The network entity sends RRC reconfiguration messages to switch modes and provides downlink control information to indicate power offset adjustments. This feedback-driven approach enables adaptability while managing system complexity through standardized procedures.
Data Source
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AI summary
A method and network entity for enabling higher order modulation (HOM) mode support for HOM capable wireless devices. The method includes determining a legacy mode power offset value for HOM mode capable wireless devices in legacy modulation mode and calculating a power headroom value for sending downlink data to the HOM mode capable wireless devices. When the power headroom value exceeds a threshold value, the HOM mode support for the HOM mode capable wireless devices is enabled using the identified legacy mode power offset value. When the power headroom value does not exceed the threshold value, and a HOM mode power offset value is available, the HOM mode power offset value being less than the legacy modulation mode power offset value, the HOM mode support for the HOM mode capable wireless devices is enabled using the HOM mode power offset value.