Carrier Selection for Random Access Load Distribution
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Solution Overview
Problem
In Narrowband Internet of Things (NB-IoT) systems, the random access procedure is limited to the anchor carrier, leading to potential bottlenecks due to the large number of devices competing for resources, and existing solutions for load balancing across multiple carriers are not optimal, especially when there is an imbalance between Rel-13 and Rel-14 UEs.
Innovation Solution
Configuration information is transmitted to wireless devices to govern which carrier within a set of carriers, including an anchor and non-anchor carriers, to perform random access, using probability values or identity-based selection methods to dynamically distribute the load across carriers, allowing Rel-14 UEs to perform random access on non-anchor carriers and alleviate load on the anchor carrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If random access is limited to anchor carrier only, then Rel-13 UEs can maintain simple operation, but load bottleneck occurs due to large number of devices competing for resources
Solution Approach 1:
The random access function is segmented between anchor carrier and non-anchor carriers. Rel-13 UEs continue to use only the anchor carrier maintaining their simple operation, while Rel-14 UEs can utilize both anchor and non-anchor carriers for random access, thereby distributing the load and increasing overall system capacity without compromising backward compatibility.
2Productivity
If Rel-14 UEs are allowed to perform random access on non-anchor carriers, then load distribution across carriers is improved, but device complexity increases due to multi-carrier support requirements
Solution Approach 1:
Different operational capabilities are assigned to different UE types based on their release versions. Rel-13 UEs maintain simple single-carrier operation on the anchor carrier, while Rel-14 UEs are equipped with enhanced multi-carrier capabilities. This local differentiation allows load distribution benefits without forcing complexity on all devices.
Solution Approach 2:
The system dynamically adapts to the capabilities of connected UEs by providing appropriate random access configurations. Rel-14 UEs can be configured to use non-anchor carriers for random access when needed, while Rel-13 UEs automatically use only the anchor carrier. This dynamic adaptation allows the network to optimize load distribution based on the actual mix of UE capabilities.
3Productivity
If probability-based carrier selection is used for random access, then load balancing across carriers is achieved, but control complexity increases due to configuration management
Solution Approach 1:
The network automatically configures probability-based carrier selection parameters for Rel-14 UEs based on current load conditions, while Rel-13 UEs continue to use default anchor carrier-only access. The UE automatically applies the configured probabilities without requiring manual intervention or complex user-side management, thereby achieving load balancing while minimizing control complexity.
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A wireless device (14A) is configured for use in a wireless communication system (10) for performing random access. The wireless device (14A) supports random access on a non-anchor carrier. The wireless device (14A) is configured to obtain configuration information (20) that governs on which carrier within a set (16) of carriers the wireless device (14A) is to perform random access, where the set (16) of carriers includes an anchor carrier (14A) and a non-anchor carrier. The configuration information (20) may for instance indicate a probability value (20A) that is assigned to each of one or more of the carriers in the set (16). Regardless, the wireless device (14A) is configured to select, from among the carriers in the set (16), a carrier on which to perform random access, in accordance with the configuration information (20). The wireless device (14A) is also configured to perform random access on the selected carrier.