Predictable Carrier Selection for CE Level Ramping in NB-IoT Random Access
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Solution Overview
Problem
In wireless communications networks, especially in NB-IoT, the RACH becomes a bottleneck during simultaneous random access attempts in larger coverage areas, as existing technologies restrict RACH configuration only to the anchor carrier, leading to inefficient CE level ramping and unpredictable carrier changes, which complicates network node resource management and positioning.
Innovation Solution
A method where wireless devices predictably change carriers and preamble indices at different CE levels during random access procedures, allowing coordinated NPRACH resource changes, ensuring network nodes can anticipate and manage random access attempts, even when the initial carrier lacks configured resources for the new CE level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If RACH configuration is restricted only to the anchor carrier, then network node resource management is simplified, but random access efficiency deteriorates in larger coverage areas
Solution Approach 1:
The patent segments the RACH configuration by separating anchor carrier and non-anchor carrier configurations. Non-anchor carriers can be independently configured with NPRACH resources for specific CE levels, allowing distributed random access opportunities across multiple carriers while maintaining manageable complexity through structured configuration parameters.
Solution Approach 2:
The patent adds a carrier dimension to RACH configuration by enabling NPRACH on non-anchor carriers. This transitions from a single-carrier (anchor only) approach to a multi-carrier approach, providing additional random access dimensions that improve efficiency in large coverage areas without overwhelming network node management.
2Adaptability or versatility
If carriers are changed unpredictably at different CE levels, then adaptability to coverage conditions is improved, but network node positioning and resource management become complicated
Solution Approach 1:
The patent implements preliminary action by configuring predictable carrier and preamble index changes before CE level transitions occur. The wireless device and network node both know in advance which carrier and preamble will be used at each CE level based on pre-configured rules, eliminating unpredictability while maintaining adaptability to coverage conditions.
Solution Approach 2:
The patent establishes feedback mechanisms where the network node can observe and verify the predictable carrier changes. The configured rules create a closed-loop system where the network node expects specific behavior and can confirm it occurs, maintaining both adaptability and predictability through coordinated interaction.
3Measurement precision
If explicit signaling is used for CE level ramping, then transmission accuracy is improved, but signaling overhead increases
Solution Approach 1:
The patent implements self-service by configuring the wireless device with rules that enable autonomous determination of carrier and preamble index at each CE level. The device independently calculates the correct resources based on pre-configured parameters without requiring explicit signaling from the network node, eliminating overhead while maintaining precision through deterministic calculations.
Solution Approach 2:
The patent uses parameter changes by configuring key parameters (carrier index, preamble index) that automatically change according to CE level transitions. These pre-configured parameter transformation rules enable accurate resource determination without additional signaling, as the parameters self-update based on the CE level state.
4Device complexity
If NPRACH resources are configured only on anchor carrier, then device complexity is reduced, but random access capacity is insufficient for simultaneous attempts
Solution Approach 1:
The patent applies universality by enabling multiple carriers (anchor and non-anchor) to serve the random access function. Each carrier can be configured with NPRACH resources for specific CE levels, creating a universal multi-carrier RACH system that increases total random access capacity while maintaining manageable device complexity through standardized configuration procedures.
Data Source
AI summary
A wireless device and a method therein for performing a transmission at a changed Coverage Enhancement (CE) level in a random access procedure. The wireless device receives a random access order indicating a first preamble and a first carrier. Further, the wireless device transmits, to a network node, the first preamble on the first carrier using a first CE level. In the absence of a valid response after a number of transmissions, the wireless device determines a second CE level that is different from the first CE level. Thereafter, the wireless device selects, in a predictable way for the network node, a carrier that is supporting the second CE level, and transmits, to the network node, a preamble on the carrier using the second CE level.