MIMO Transmitter Output Power Control for RF EMF Compliance
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Solution Overview
Problem
The introduction of advanced antenna systems (AAS) in wireless communication networks increases beamforming gain, leading to higher power density and potential non-compliance with RF EMF exposure regulations, making it challenging to maintain compliance distances and exclusion zones, especially when reusing existing sites.
Innovation Solution
A method for controlling the output of MIMO transmission points by determining average output power, comparing it to a reference value, allocating resources based on beam gains, and scheduling data to ensure compliance with RF EMF exposure regulations by limiting the use of available resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If advanced antenna systems (AAS) are introduced to increase beamforming gain, then network capacity and coverage are improved, but power density increases leading to non-compliance with RF EMF exposure regulations
Solution Approach 1:
The patent applies periodic action by implementing time-averaged power control where the transmission point alternates between high-power and low-power transmission intervals. The system calculates average output power over a defined time period T and adjusts resource allocation periodically to ensure the time-averaged power density complies with RF EMF regulations while maintaining high instantaneous data rates during high-power intervals.
Solution Approach 2:
The patent implements dynamics by making the resource allocation fraction dynamic rather than static. The system continuously monitors average output power and adjusts the fraction of available resources allocated to different wireless devices in real-time, allowing the network to adaptively balance between maintaining high capacity and complying with RF EMF exposure limits under varying channel conditions and traffic demands.
2Length of moving object
If beamforming gain is increased to enhance coverage, then effective signal strength is improved, but compliance distances and exclusion zones increase
Solution Approach 1:
The patent uses periodic action to allow high instantaneous power transmissions that extend coverage range, followed by lower power intervals that reduce average power density. This periodic high-low power pattern enables the system to achieve effective long-range coverage during high-power phases while maintaining regulatory compliance through averaging over time T, thereby reducing required compliance distances compared to continuous high-power transmission.
3Object-affected harmful factors
If time-averaged power is reduced to maintain RF EMF compliance, then power density limits are met, but network performance is compromised
Solution Approach 1:
The patent applies dynamics by implementing dynamic resource allocation that adjusts the fraction of available resources allocated to each wireless device based on real-time average power conditions. When average power is high, the system reduces resource fractions to comply with RF EMF limits; when average power is low, it increases resource fractions to maximize network performance. This dynamic adaptation prevents permanent performance degradation while maintaining compliance.
Solution Approach 2:
The patent implements parameter changes by varying the resource allocation fraction as a function of the comparison between average output power and reference values. The system changes key parameters including the fraction of available resources, the time-averaging window, and beam weight configurations to optimize the trade-off between maintaining power density compliance and preserving network throughput and service quality.
Data Source
AI summary
A MIMO transmission point utilizes respective pluralities of beam weights to transmit corresponding pluralities of beams to each group of wireless devices, with respective numbers of resources being allocated for transmissions to each group of wireless devices. One method comprises: determining an average output power of the transmission point over a period of time in a first direction; comparing the average output power to an output power reference value; determining a fraction of a pool of available resources for the allocation of data to be transmitted by the transmission point as a function of the comparison; for each group of wireless devices, and determining beam gains in the first direction for each of the plurality of beams and weighting the number of resources allocated to the group of wireless devices according to the determined beam gains to obtain an effective number of resource blocks in the resources in the first direction.