Cell Selection Using RAN Node Response Times
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Solution Overview
Problem
In 5G cellular communications systems, User Equipment (UE) lacks awareness of cell load within the gNB during cell reselection, leading to potential failure in meeting stringent latency requirements due to unknown processing loads, which can result in delayed UP payloads and compromised Quality of Service (QoS).
Innovation Solution
RAN nodes broadcast response times reflecting their current processing loads, allowing UE to consider these times during cell or beam selection/reselection, thereby accounting for delays and loads across network interfaces, ensuring better latency compliance and load balancing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cell reselection is based only on radio link quality measurements (RSRP, RSRQ), then the cell selection process is simple and fast, but the UE cannot account for gNB processing load, leading to potential latency violations
Solution Approach 1:
The gNB provides feedback to the UE about its processing load state through system information blocks (SIBs) or other signaling mechanisms. This feedback enables the UE to make informed cell reselection decisions by considering both radio link quality and gNB processing capabilities, thereby resolving the information asymmetry and improving latency fulfillment reliability.
Solution Approach 2:
The gNB proactively announces its processing load characteristics before the UE needs to make a cell reselection decision. By providing this information in advance through system information, the UE can evaluate candidate cells based on both radio conditions and expected processing delays, enabling better preliminary assessment of which cell to select for meeting latency requirements.
2Productivity
If the UE selects cells based on best radio conditions without considering gNB load, then cell selection is straightforward, but UP payloads may experience delays due to high processing load at selected cells
Solution Approach 1:
The cell selection criterion becomes dynamic by incorporating the gNB processing load state. Instead of a static radio-quality-only metric, the selection now adapts to current gNB conditions. The UE can dynamically adjust its cell preference based on real-time or near-real-time gNB load announcements, balancing selection efficiency with payload delay avoidance.
Solution Approach 2:
The cell evaluation parameters are extended beyond radio link quality (RSRP, RSRQ) to include gNB processing load metrics. By changing the parameter set used for cell comparison, the system enables the UE to identify cells that not only have good radio conditions but also sufficient processing capacity to handle UP payloads within required latency bounds.
3Reliability
If all UEs reselect to the same high-quality cell regardless of gNB load, then radio link quality is optimized, but load balancing across the network is compromised
Solution Approach 1:
Each gNB announces its local processing load characteristics, allowing UEs to differentiate between cells based on their specific load conditions. This enables a distributed load balancing mechanism where UEs can select cells with adequate local capacity, preventing overload at any single cell while maintaining good radio link quality where possible.
Solution Approach 2:
The network achieves load balancing through self-service mechanisms without centralized control. Each gNB independently announces its load state, and UEs autonomously make reselection decisions based on this information. This decentralized approach allows the network to naturally balance load across multiple cells while maintaining radio quality optimization where capacity exists.
Data Source
AI summary
Systems and methods for using response times of one or more Radio Access Network (RAN) nodes for cell or beam selection or reselection are disclosed herein. In one embodiment, a method performed by a User Equipment (UE) for cell or beam selection or reselection in a cellular communications system comprises receiving response times from one or more RAN nodes. The method further comprises performing a cell or beam selection or reselection procedure that takes into consideration the response times received from the one or more RAN nodes. Corresponding embodiments of a UE are also disclosed. Embodiments of a method performed by a RAN node and corresponding embodiments of a RAN node are also disclosed.