Radio Base Station Power Control for RF EMF Compliance
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Solution Overview
Problem
Radio base stations equipped with advanced antenna systems (AAS) face challenges in maintaining RF EMF exposure compliance due to increased beamforming gain, leading to higher momentary power density, which can exceed regulatory limits, making it difficult to deploy 4G or 5G base stations in close proximity without expanding RF EMF exclusion zones.
Innovation Solution
A control device and method that dynamically control the total average transmission power of radio base stations over a fixed time period by adjusting CDMA resources, using a resource factor value to restrict the use of CDMA resources, limiting code tree branches, transmission time intervals, user data rates, and coding rates to ensure compliance with RF EMF exposure regulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If advanced antenna systems with large number of transmitters are deployed to achieve high directivity and beamforming gain, then capacity and coverage are improved, but momentary power density increases and may exceed RF EMF exposure limits
Solution Approach 1:
The patent applies periodic action by controlling the transmission power in a time-averaged manner over a fixed time period. The system allows momentary power density to exceed limits temporarily, but ensures that the average power density over the specified time period T remains below the regulatory limit. This is achieved through dynamic power adjustment where the base station transmits at high power during some time intervals and reduces power during others, creating a periodic control pattern that satisfies both capacity requirements and RF EMF exposure regulations.
Solution Approach 2:
The patent implements dynamics by making the transmission power adjustable and controllable in real-time. The base station dynamically adjusts its transmission power level based on current conditions while maintaining a time-averaged power constraint. This dynamic power control allows the system to optimize capacity and coverage through beamforming while simultaneously complying with RF EMF exposure limits by adapting the power level over the fixed time period.
2Length of stationary object
If maximum EIRP of AAS is used to improve coverage, then beamforming gain is increased, but the size of RF EMF compliance boundary increases making deployment difficult
Solution Approach 1:
The patent resolves this contradiction by implementing periodic power control over a fixed time period. Instead of maintaining constant maximum EIRP, the system periodically adjusts transmission power levels such that the time-averaged power density remains within compliance limits. This allows the base station to achieve effective coverage through beamforming while the compliance boundary size is reduced to feasible dimensions by controlling the average power output over time.
3Object-affected harmful factors
If time-averaged power is maintained below threshold to reduce compliance boundary size, then RF EMF exposure compliance is improved, but momentary transmission power is restricted
Solution Approach 1:
The patent applies periodic action by allowing transmission power to vary over time while maintaining the time-averaged power below the threshold. The system can transmit at higher momentary power levels during certain intervals and reduce power during other intervals, ensuring that the average over the fixed time period T satisfies RF EMF exposure requirements. This periodic power adjustment resolves the contradiction by enabling both momentary power flexibility and compliance with average power density limits.
4Productivity
If co-sited radio base stations are deployed to improve capacity, then network capacity is increased, but the total RF EMF compliance boundary size increases
Solution Approach 1:
The patent resolves this contradiction by implementing coordinated periodic power control across multiple co-sited base stations. Each base station adjusts its transmission power over time such that the combined time-averaged power density from all co-sited stations remains within compliance limits. This allows the deployment of multiple base stations at the same geographical position to increase network capacity while the total compliance boundary size is reduced to feasible dimensions through synchronized average power control.
Data Source
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AI summary
There is provided mechanisms for controlling total average transmission power of a radio base station over a fixed time period. A method is performed by a control device. The method comprises obtaining values of average total transmission power of at least one previous transmission from the radio base station. The method comprises determining a resource factor value from the value of average total transmission power and a set point value of the average total transmission power. The method comprises determining, based on the resource factor value, an action that restricts the amount of code-division multiple access (CDMA) resources to be used at least for a current transmission. The method comprises controlling the total average transmission power over the fixed time period by initiating the determined action at least for the current transmission.