Coordinated AP Calibration via Channel Response Difference
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Solution Overview
Problem
In CoMP systems, especially under TDD mode, uplink-downlink channel reciprocity errors between coordinated APs cause phase and amplitude differences in data transmission, affecting coherent transmission and system performance, as existing methods fail to effectively calculate and address these differences.
Innovation Solution
A method and base station configuration that calculate the uplink-downlink channel response difference between coordinated APs by obtaining and dividing frequency-domain responses, allowing for data calibration to mitigate these errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If independent antenna calibration is performed by each AP, then calibration complexity is reduced, but uplink-downlink channel reciprocity errors cause phase and amplitude differences in coordinated transmission
Solution Approach 1:
The base station acts as an intermediary that collects channel response information from multiple APs, calculates the uplink-downlink channel response differences, and provides calibration parameters to coordinate the transmission phases and amplitudes across APs, thereby achieving coherent transmission without requiring complex inter-AP coordination
Solution Approach 2:
The system implements feedback by having APs report their channel frequency-domain responses to the base station, which then calculates calibration parameters based on the difference between uplink and downlink channel responses and feeds back adjusted transmission parameters to the APs for coherent coordinated transmission
2Measurement precision
If channel calibration is performed at different times for uplink and downlink, then channel estimation accuracy is improved, but channel variations between time points introduce additional errors
Solution Approach 1:
The base station obtains both uplink and downlink channel frequency-domain responses in advance before coordinated transmission begins, calculates the uplink-downlink channel response difference as a calibration parameter, and uses this pre-calculated parameter to adjust transmission parameters, thereby avoiding real-time channel variations during actual coordinated transmission
3Device complexity
If coordinated transmission is performed without calibration, then system complexity is reduced, but phase and amplitude differences significantly degrade transmission performance
Solution Approach 1:
The system changes the transmission parameters (phase and amplitude) of coordinated APs based on the calculated uplink-downlink channel response difference, applying calibration factors to adjust the transmission parameters so that signals from multiple APs arrive at the receiver with coherent phase and appropriate amplitude, thereby improving transmission performance without requiring complex hardware modifications
Data Source
AI summary
A method and a base station for calibrating data transmitted by coordinated APs are disclosed. The method includes: a base station obtaining an uplink channel frequency-domain response and a downlink channel frequency-domain response between a first AP and a second AP which participate in coordination; the base station dividing the uplink channel frequency-domain response by the downlink channel frequency-domain response to obtain an uplink and downlink channel response difference between the first AP and the second AP; and the base station calibrating the data transmitted by the first AP and the second AP in coordination according to the uplink and downlink channel response difference. The method and base station in the embodiments of the present document are applied to calibrate the data transmitted by coordinated APs.