Beam Selection Using RSRP and Back-Off Power Difference
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Solution Overview
Problem
In millimeter-wave communication, the conventional method of determining the uplink transmit beam based on the downlink reference signal measurement reduces uplink communication performance due to power back-off requirements for radio frequency energy exposure compliance, which affects the terminal's ability to maintain effective communication while adhering to regulatory standards.
Innovation Solution
A beam selection method where a terminal performs RSRP and MPE measurements on multiple beams to determine the optimal uplink working beam based on the difference between RSRP and back-off power, allowing for improved communication performance by selecting the beam with the greater difference, thereby enhancing both uplink and downlink communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the terminal determines the uplink transmit beam based on downlink reference signal measurement, then the beam selection process is simple, but the uplink communication performance deteriorates due to power back-off requirements
Solution Approach 1:
The patent changes the selection criterion from RSRP alone to a composite metric that incorporates both RSRP and back-off power. The terminal calculates a first metric equal to RSRP minus back-off power for each beam, and selects the beam with the maximum first metric. This parameter transformation resolves the contradiction by maintaining simple beam selection logic while accounting for power back-off effects, thereby improving uplink communication performance without significantly increasing complexity
Solution Approach 2:
The patent performs preliminary measurement of back-off power for each beam before final beam selection. The terminal measures the back-off power associated with each candidate beam based on its direction and the terminal's orientation, then uses this pre-measured information in the beam selection decision. This preliminary action allows the system to anticipate power constraints and select beams that will maintain better performance after power back-off is applied
2Reliability
If the terminal performs power back-off to satisfy radio frequency energy exposure regulations, then compliance with standards is achieved, but uplink transmit power is reduced
Solution Approach 1:
The patent applies different power back-off levels to different beams based on their specific characteristics. Instead of applying a uniform power back-off to all beams, the terminal calculates the back-off power individually for each beam based on its direction relative to the terminal's orientation and the applicable exposure limits. This local differentiation allows the system to maintain maximum permissible exposure compliance while minimizing the impact on uplink transmit power for each specific beam
Solution Approach 2:
The patent converts the harmful effect of power back-off into a beneficial selection criterion. By incorporating back-off power into the beam selection metric (RSRP minus back-off power), the system uses the power reduction information to identify beams that will perform better after back-off is applied. This transforms the previously harmful power reduction into a useful indicator for optimizing beam selection, thereby maintaining compliance while improving overall uplink performance
Data Source
AI summary
A beam selection method and a communication apparatus are provided, which relate to the field of communication technologies. The method includes: A terminal receives a downlink reference signal from a third beam of a network device on a first beam and a second beam; then, the terminal performs RSRP measurement and MPE measurement on the first beam and the second beam separately to obtain first RSRP, second RSRP, first back-off power, and second back-off power; and when a difference between the first RSRP and the first back-off power is greater than a difference between the second RSRP and the first back-off power, the terminal sends uplink data by using the first beam. In this technical solution, the terminal may select an uplink working beam with reference to the measured back-off power of the first beam and the measured back-off power of the second beam.