gNB-DU Handover Control Using L1 and L3 Mobility Measurements
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wireless communication systems face challenges with lower layer triggered mobility (LTM) due to unreliable L1 measurements, leading to potential handover issues such as ping-pongs and selection of non-preferred cells, especially in high-frequency bands, and lack of efficient coexistence with L3-based mobility.
Innovation Solution
The gNB-DU makes handover decisions by combining L1 measurements with L3 measurements, using L3 HO information from the gNB-CU to enhance decision robustness, and implementing new F1AP messages for signaling between the gNB-CU and gNB-DU to manage LTM handovers effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If L1 measurements are used for handover decisions in lower layer triggered mobility, then handover latency is reduced, but measurement reliability deteriorates leading to wrong cell selections
Solution Approach 1:
The patent combines L1 measurements (fast, low latency) with L3 measurements (reliable, averaged) to make handover decisions. The gNB-DU receives both measurement types and integrates them to select target cells, ensuring both speed and accuracy in mobility decisions.
Solution Approach 2:
The gNB-DU acts as an intermediary between L1/L2 fast processing and L3 reliable processing. It receives L1 measurements from the UE, obtains L3 HO information from the gNB-CU, and uses both to make the final handover decision, mediating between the two measurement types.
2Speed
If L1 measurements are used for handover decisions, then response speed is improved, but measurement accuracy deteriorates due to lack of time averaging
Solution Approach 1:
The patent merges L1 measurements (high speed, no averaging) with L3 measurements (high accuracy, time-averaged) to achieve both fast response and accurate measurement for handover decisions.
Solution Approach 2:
The system changes the measurement parameters by using different averaging periods for L1 and L3 measurements. L1 measurements use short or no averaging for speed, while L3 measurements use longer averaging for accuracy, and both are combined for the final decision.
3Duration of action of moving object
If lower layer triggered mobility is implemented, then handover interruption time is reduced, but handover stability deteriorates due to ping-pong effects
Solution Approach 1:
The patent combines L1 fast switching capability with L3 stable decision-making to reduce handover interruption time while preventing ping-pong effects through more reliable target cell selection.
Solution Approach 2:
The system uses feedback from both L1 and L3 measurements to make informed handover decisions. The gNB-DU continuously monitors both measurement types and uses this feedback to avoid selecting unstable target cells, reducing ping-pong effects.
4Loss of information
If L1 measurements are used for cell switching, then overhead is reduced, but decision robustness deteriorates
Solution Approach 1:
The patent merges L1 measurements (low overhead) with L3 measurements (higher reliability) to maintain low overhead while improving decision robustness through the additional L3 HO information from the gNB-CU.
Data Source
Figure 1
Figure 2
Figure 2
AI summary
A communication network comprising distributed units for supporting radio coverage via a cell and for providing access to the cell to a user equipment and central units each controlling several distributed units. The distributed units comprise: mobility control circuitry configured: in response to receipt of layer 3 handover information for a user equipment from a central unit and where the mobility control circuitry has access to layer 1 measurements for the user equipment, to select a cell for a handover in dependence upon the layer 3 handover information and the layer 1 measurements.