Wireless Device Random Access Preamble Subset Selection
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Solution Overview
Problem
In mobile communication systems, the increasing number of wireless devices leads to a high probability of preamble collisions during random access procedures, which prolongs the access time and can result in failed data transmissions and idleness of radio resources, especially affecting devices that require real-time data transmission.
Innovation Solution
A random access mechanism where wireless devices receive a system message carrying a random access success rate from a base station and divide preambles into subsets based on this rate, allowing them to select preambles from larger subsets gradually in case of collisions, employing a code-domain backoff mechanism to reduce collision probability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If all wireless devices select preambles randomly from the same set, then the random access procedure is simple to implement, but the probability of preamble collision increases significantly
Solution Approach 1:
The patent divides the single preamble set into multiple preamble subsets (first preamble subset and second preamble subset) based on different random access success rates. Devices with higher success rates select from a smaller first subset, while devices with lower success rates select from a larger second subset. This segmentation reduces collision probability by distributing devices across different subsets while maintaining implementation simplicity.
2Reliability
If wireless devices re-select preambles randomly after collision, then the random access procedure can be retried, but the access time is prolonged and resources are wasted
Solution Approach 1:
The patent applies preliminary action by having devices select preambles from appropriately sized subsets based on pre-acquired random access success rate information. This prevents collisions before they occur rather than requiring reselection after collision, thereby reducing access time and avoiding resource waste while maintaining high success rates.
3Device complexity
If a large number of wireless devices use the same preamble set, then the system is easy to manage, but the radio resources become idle due to repeated collisions and retransmissions
Solution Approach 1:
The patent changes the parameter of preamble subset size based on the random access success rate. By dynamically adjusting which subset devices select from based on their success rate metrics, the system efficiently utilizes radio resources without requiring complex management mechanisms, thereby reducing resource idleness while maintaining simple system operation.
Data Source
AI summary
A wireless device and a random access method thereof for a mobile communication system are provided. The mobile communication system defines a plurality of preambles. The wireless device receives a system message carrying a random access success rate from a base station, and divides the preambles into N preamble subsets according to the random access success rate. The N preamble subsets have a strict partial order relationship therebetween. The union of the N preamble subsets consists of the preambles. When requesting random access from the base station, the wireless device randomly selects a preamble from the smallest preamble subset. When a preamble collision occurs, the wireless device reselects a preamble from the larger preamble subset gradually for the random access.