Factor Graph Beam Sweeping for mmWave Synchronization
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Solution Overview
Problem
In millimeter-wave wireless networks, ensuring initial synchronization of user equipment (UEs) while minimizing power consumption and interference is challenging due to the use of narrow beams, which provide good signal quality to only a small area, leading to difficulties in covering all UEs and optimizing power settings across multiple access nodes.
Innovation Solution
Access nodes exchange messages to jointly determine optimized transmit power settings and beam sweep patterns using a message-passing algorithm based on historical statistics, modeling the power consumption as a factor graph with check and variable nodes to minimize total power consumption while meeting quality-of-service constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If narrow beams are used for synchronization signal transmission, then signal quality to targeted devices is improved, but coverage area is reduced
Solution Approach 1:
The coverage area is divided into multiple sectors, each served by a narrow beam. Multiple narrow beams are transmitted in different directions to collectively cover the entire service area, ensuring both high signal quality in each direction and comprehensive coverage across all sectors.
Solution Approach 2:
The access node performs periodic beam sweeping, sequentially transmitting narrow synchronization beams in different directions across multiple time slots. This periodic scanning ensures that all directional sectors are covered over time while maintaining narrow beamwidth for high signal quality in each direction.
2Power
If all antenna elements are used to transmit synchronization signals, then total transmitted power is increased, but power efficiency is reduced
Solution Approach 1:
Different antenna elements or element subsets are selectively activated based on the required beam direction. Only the necessary antenna elements for each specific beam are powered on, while others remain inactive. This localized activation ensures sufficient transmitted power for each beam while improving overall power efficiency by avoiding unnecessary power consumption from all elements.
Data Source
AI summary
Techniques for determining beam-sweeping patterns for synchronization signals transmitted in a region by several access nodes in a network, where each access node is connected to a corresponding array of antenna elements. An example method includes modeling a total power function for the power transmitted in the synchronization signals, as a factor graph having a plurality of check nodes and variable nodes, each check node corresponding to a virtual wireless device in the region and each variable node corresponding to an available beam for an access node. The virtual wireless devices are emulated so as to implement quality-of-service constraints on synchronization signals received by the virtual wireless devices. An iterative message-passing algorithm, such as a min-sum algorithm, is applied to the modeled total power function, to determine a sequence of power levels, for each access node, for sweeping synchronization signal beams, so as to minimize the total power function.