Beam Switching in Cellular Networks
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Solution Overview
Problem
In cellular communication systems employing beam-forming, sudden drops in signal power and signal-to-interference ratio can occur quickly due to shadowing, leading to connection loss before there is enough time to initiate and complete a beam switch, resulting in radio link failures.
Innovation Solution
Decreasing the transmit power level of interfering signals during the mobility procedure to reduce the risk of connection loss, allowing for the completion of a beam switch or mobility procedure, which involves identifying interfering signals, reducing their power, and executing part of the mobility procedure with the decreased power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference signals are transmitted continuously in all beams, then beam switch decisions can be made accurately, but power consumption increases and interference is added
Solution Approach 1:
The system performs preliminary measurements of beam qualities before initiating a mobility procedure. The wireless communication device measures reference signals from candidate beams and reports beam quality information to the network node in advance, so that when a beam switch is needed, the decision can be made quickly based on pre-collected measurement data rather than requiring continuous reference signal transmission in all beams
Solution Approach 2:
Instead of continuous reference signal transmission in all beams, the system uses periodic measurement opportunities where the wireless communication device measures available reference signals from candidate beams and reports back to the network node. This periodic measurement approach reduces power consumption and interference while still providing sufficient information for beam switch decisions
2Reliability
If beam switch procedure is initiated quickly, then connection loss is prevented, but measurement accuracy may be insufficient
Solution Approach 1:
The wireless communication device continuously monitors and measures reference signals from candidate beams in the background, maintaining up-to-date beam quality information without requiring active triggering. When signal quality deteriorates, the pre-measured data is immediately available for rapid beam switch decision-making, ensuring both connection reliability and measurement accuracy
3Reliability
If transmit power of interfering signals is decreased during mobility procedure, then beam switch success probability increases, but communication efficiency decreases
Solution Approach 1:
The network node proactively decreases the transmit power of interfering signals before the beam switch procedure is initiated, creating a more favorable interference environment in advance. This preliminary anti-action against interference ensures that the mobility procedure can complete successfully without being disrupted by strong interfering signals, while the power reduction is temporary and localized only to the duration of the beam switch procedure
Data Source
AI summary
A method for a network node of a cellular communication network is disclosed. The network node and at least some other network nodes of the cellular communication network are each adapted to support a plurality of beams of a signal beam-forming scheme and to communicate with a wireless communication device using at least one of the plurality of beams. The method comprises initiating a mobility procedure, identifying interfering signals transmitted by one or more interfering beams, decreasing a transmit power level of the identified interfering signals, and executing at least part of the mobility procedure while the identified interfering signals use the decreased transmit power level. The mobility procedure may, typically, comprise transmission of a reference signal on each of one or more candidate beams (wherein the reference signals are for measurement by the wireless communication device), reception of a report from the wireless communication device (wherein the report is indicative of a result of measurements of the reference signals and is for making a beam switch decision), and execution of the beam switch (if applicable). Corresponding computer program product, arrangement and network node are also disclosed.