Carrier Selection for High-Speed UEs Using Low GDV
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Solution Overview
Problem
In LTE cellular wireless networks, high group delay variation (GDV) and Doppler Effect-induced signal distortions lead to reduced signal quality and reliability, particularly for fast-moving user equipment (UEs), causing communication interruptions.
Innovation Solution
A base station determines the speed of movement of UEs and selects a carrier with low GDV to minimize distortion, thereby reducing overall signal distortion and maintaining communication quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a base station serves fast-moving UEs on carriers with high GDV, then carrier bandwidth and data rate are improved, but signal quality and reliability deteriorate due to increased distortion
Solution Approach 1:
The base station dynamically selects carriers based on real-time UE movement speed measurements. When a UE is detected to be moving above a threshold speed, the base station identifies and assigns a carrier with low GDV characteristics from available carriers, thereby adapting the carrier assignment to the current motion state of the UE to minimize distortion while maintaining data rate
Solution Approach 2:
The system changes the carrier parameter (specifically GDV characteristic) based on UE movement conditions. By measuring UE speed and selecting carriers with appropriate GDV values (low GDV for fast-moving UEs, high GDV for stationary or slow-moving UEs), the system optimizes the match between carrier characteristics and UE motion state to resolve the contradiction between data rate and signal quality
2Reliability
If carrier selection is based on low GDV for fast-moving UEs, then signal distortion is reduced, but system complexity increases due to additional measurement and selection processes
Solution Approach 1:
The base station pre-measures and characterizes the GDV of each available carrier before UE arrival. When a UE connects, the base station already has GDV information for all carriers, enabling rapid selection based on UE speed without requiring complex real-time analysis during the connection establishment phase
Solution Approach 2:
The UE itself provides movement speed information to the base station through uplink transmissions. The base station utilizes this readily available speed information (derived from uplink signal processing) to trigger the carrier selection process, eliminating the need for separate measurement mechanisms and reducing overall system complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The approach effectively reduces signal distortions caused by GDV and Doppler Effect, ensuring stable communication for UEs by dynamically selecting carriers based on UE movement speed and GDV, thereby enhancing signal quality and reliability.
Implementation Method 1
high group delay variation (GDV) and Doppler Effect-induced signal distortions lead to reduced signal quality and reliability, particularly for fast-moving user equipment (UEs)
Implementation Method 2
each base station may be configured with filters that pass an entire LTE band (e.g., LTE Band 41) and block frequencies outside of the band. In other LTE deployments, a base station may be configured with filters that pass a portion of an LTE band (e.g., a 50 MHz range of frequencies within LTE Band 41) and block frequencies outside of the desired portion the LTE band (e.g., outside of the desired 50 MHz frequency range). Signals that traverse the amplifiers and filters of base stations will experience various signal impairments, including group delay, which is a measure of the time delay of the amplitude envelopes of the various sinusoidal components (e.g., subcarriers) of the signal as the signal propagates through a filter and/or amplifier. Group delay is inversely proportional to filter bandwidth and nearly proportional to the order of the filter.
Implementation Method 3
In order to determine a GDV of a carrier on which to serve a UE, a base station may make use of a frequency response of a filter configured to pass frequencies of the carrier
Data Source
AI summary
Disclosed are methods and systems for selecting a carrier on which to serve a user equipment device (UE). In particular, a base station may determine that a speed of movement of the UE is threshold high. In response to determining that the speed of movement of the UE is threshold high, the base station may select a carrier based on a group delay variation (GDV) of the selected carrier. For example, the base station may respond to the determining by selecting a carrier having a threshold low GDV. In another example, the base station may respond to the determining by selecting the carrier having the lowest GDV among two or more candidate carriers being considered as part of the selection process. As such, once a carrier is selected, the base station may then serve the UE on the selected carrier.