NB-IoT Random Access Carrier Selection Reducing Collisions
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Solution Overview
Problem
In NB-IoT systems, the collision probability increases when terminal devices randomly select new carriers for access without ensuring that the selected carrier and its resources are reserved by the base station, leading to interference with other devices.
Innovation Solution
The terminal device determines a new access carrier based on a pre-obtained access carrier information list and the first access carrier indicated by the base station, using a preset algorithm to calculate the index of the second access carrier, ensuring that the base station can configure reserved resources and avoid collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the terminal device randomly selects a new carrier for access, then the terminal device can attempt random access on multiple carriers, but the collision probability greatly increases and interference occurs with other terminal devices
Solution Approach 1:
The patent changes the carrier selection parameter from random selection to deterministic selection based on a formula: carrier index = (first carrier index + offset) mod N, where N is the number of carriers supporting the new coverage level. This parameter change ensures that terminal devices with the same first carrier index will select the same second carrier index, allowing base stations to predict and reserve resources, thereby reducing collision probability while maintaining carrier selection flexibility
Solution Approach 2:
The patent introduces a feedback mechanism where the base station receives the first carrier index from the terminal device, calculates the corresponding second carrier index using the same formula, and reserves random access resources on that carrier. This feedback loop ensures that the base station has advance knowledge of which carrier the terminal will select, enabling resource reservation and avoiding collisions
2Reliability
If the terminal device increases coverage level after access failures, then the terminal device can maintain connection, but the randomly selected carrier may not have reserved resources causing collision
Solution Approach 1:
The patent applies preliminary action by having the terminal device calculate the second carrier index before actually performing random access. The terminal uses the formula carrier index = (first carrier index + offset) mod N to determine the target carrier in advance, and the base station similarly calculates and reserves resources on that carrier before the terminal attempts access. This preliminary calculation and resource reservation prevent collisions when the terminal increases coverage level and selects a new carrier
Data Source
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AI summary
Embodiments of this application provide a random access method and apparatus, a device, and a storage medium. The method includes: determining, by a terminal device, a second access carrier based on a pre-obtained access carrier information list and information about a first access carrier that is indicated by a base station and that can be used for access, where the access carrier information list includes information about all carriers that support random access; and then performing, by the terminal device, random access on the second access carrier. When performing random access, the terminal device determines the new second access carrier in the access carrier information list based on the first access carrier already known by the base station, instead of randomly selecting an access carrier. The base station may also determine, based on the indicated first access carrier, the second access carrier used by the terminal device, so as to configure an access carrier for another terminal device. This reduces a probability of a collision between the terminal device and the another terminal device, and avoids interference on use of the another terminal device.