Dedicated Random Access Preamble Validity Pattern for LTE Uplink Synchronization
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Solution Overview
Problem
In wireless telecommunications, particularly in LTE systems, the random access procedure faces delays and collisions due to the shortage of dedicated random access preambles, leading to inefficiencies in uplink synchronization and resource allocation.
Innovation Solution
The introduction of a validity pattern for dedicated random access preambles allows UEs to perform random access in specific PRACH occurrences, effectively extending the availability of dedicated preambles and reducing collisions and delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of dedicated random access preambles is increased, then collision probability decreases, but system complexity and resource overhead increase
Solution Approach 1:
The patent segments the random access procedure into two distinct phases: contention-based random access using non-dedicated preambles from a shared pool, and contention-free random access using dedicated preambles assigned to specific UEs. This segmentation allows the system to handle different access scenarios with appropriate preamble types, reducing overall collision probability while managing complexity through structured resource allocation.
Solution Approach 2:
The patent implements dynamic preamble allocation where the eNB can transition a UE from contention-based to contention-free access by assigning a dedicated preamble. This dynamic adjustment optimizes resource utilization by providing dedicated preambles only when needed, balancing reliability improvement with system complexity management.
2Loss of time
If dedicated preambles are assigned to all UEs, then random access delays are reduced, but available preambles for other UEs decrease
Solution Approach 1:
The patent implements dynamic preamble assignment where UEs transition from contention-based to contention-free access based on network conditions and UE behavior. The eNB assigns dedicated preambles selectively to UEs that require them, such as during handover or when uplink synchronization is needed, while other UEs continue using the shared non-dedicated preamble pool. This dynamic approach reduces random access delays for specific UEs without depleting the overall preamble resources.
Solution Approach 2:
The patent enables preamble reuse where dedicated preambles assigned to UEs can be recovered and reassigned to other UEs after the original UE completes its random access procedure or when the dedicated preamble is no longer needed. This recovery mechanism ensures that dedicated preambles are not permanently consumed, maintaining resource availability while providing low-delay access when required.
3Reliability
If contention-free random access is used, then collision probability decreases, but system resource overhead increases
Solution Approach 1:
The patent segments the preamble pool into non-dedicated preambles for contention-based access and dedicated preambles for contention-free access. This segmentation allows the system to use collision-free dedicated preambles only when necessary (e.g., for handover or synchronization), while relying on the shared non-dedicated pool for general access, thereby reducing overall resource overhead while maintaining low collision probability for critical operations.
Solution Approach 2:
The patent changes the state of preamble allocation from static to dynamic, where preambles can be temporarily dedicated to specific UEs for contention-free access and then returned to the shared pool. This parameter change allows the system to adjust the ratio of dedicated to non-dedicated preambles based on current network conditions, optimizing the balance between collision reduction and resource overhead.
Data Source
AI summary
The present invention relates to methods and apparatuses (radio base station) and UE for enabling a UE to perform a random access. According to embodiments of the present invention, an identification number of a dedicated random access preamble is, in a message, transmitted together with information indicating in which channel or channels the preamble is valid for the UE. The UE can then use the received information and based on that information perform a random access.