Two-Step Random Access Configuration for Cellular Handover
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Solution Overview
Problem
Existing handover procedures in cellular networks do not adequately support two-step random access procedures, leading to issues such as increased PRACH load, resource wastage, and collisions, especially in scenarios like small cells and stationary UEs.
Innovation Solution
A method for configuring a random access procedure that involves triggering a message from a serving cell to a UE indicating a preferred two-step random access procedure during handovers, along with configuring the UE with channel or bandwidth part information for Listen Before Talk (LBT) and random access operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If two-step random access procedure is used, then random access latency is reduced, but PRACH load and collision increase
Solution Approach 1:
The patent changes the parameter of random access procedure type from four-step to two-step, which reduces latency by eliminating intermediate steps. The base station configures the UE to use two-step random access by setting ra-Type to 'twoStep', thereby reducing the number of message exchanges and access latency while managing PRACH load through selective configuration.
Solution Approach 2:
The patent introduces dynamic selection between four-step and two-step random access procedures based on current network conditions. The base station evaluates suitability criteria (load, channel conditions, UE capabilities) and dynamically configures the appropriate procedure type, allowing the system to adapt to changing conditions and optimize between latency reduction and load management.
2Loss of time
If two-step random access procedure is used, then random access latency is reduced, but resource wastage increases
Solution Approach 1:
The patent changes the random access procedure parameter to two-step, reducing latency. Resource wastage is mitigated by configuring preambles specifically for two-step procedures (separate from four-step preambles) and by selectively enabling two-step RA only when suitable, avoiding unnecessary resource consumption in scenarios where it is not beneficial.
Solution Approach 2:
The patent applies different qualities/resources to different random access types. Separate preamble sets are allocated for two-step and four-step procedures, allowing optimized resource allocation. Two-step specific resources are provided only where needed, reducing overall resource wastage while maintaining latency benefits in appropriate scenarios.
3Loss of time
If two-step random access procedure is used, then random access latency is reduced, but collision increases
Solution Approach 1:
The patent changes to two-step procedure to reduce latency while managing collision risk through parameter configuration. The base station configures appropriate parameters including preamble sets, power control settings, and resource allocations optimized for two-step RA, balancing latency reduction with collision mitigation based on current network conditions.
Solution Approach 2:
The patent implements dynamic selection between four-step and two-step procedures based on real-time suitability assessment. When collision risk is high or conditions are unfavorable, the system dynamically reverts to or selects four-step procedure, which has better collision handling characteristics, thereby maintaining reliability while still utilizing two-step RA benefits when appropriate.
4Reliability
If four-step random access procedure is used, then reliability is improved, but random access latency increases
Solution Approach 1:
The patent implements dynamic procedure selection where the system can switch between four-step and two-step random access based on current conditions. When reliability is prioritized (high collision risk, poor channel conditions), four-step is selected for its robust collision handling. When latency is prioritized (good conditions, low load), two-step is selected, achieving optimal balance between reliability and latency.
Solution Approach 2:
The patent uses parameter configuration to enable flexible selection between procedures. By configuring ra-Type parameter and associated parameters (preamble sets, resources), the system can switch between four-step and two-step procedures to match current requirements, achieving both reliability when needed and low latency when possible.
Data Source
AI summary
A technique for configuring a random access procedure to be performed by a user equipment, UE, (310) when handing over from a serving cell to a target cell in a cellular network is provided. A method implementation of the technique is performed by a base station (300) associated with the serving cell and comprises triggering sending, to the UE (310), a message related to the handover from the serving cell to the target cell, the message including an indication of a preferred type of random access procedure to be performed by the UE (310) with the target cell, wherein the preferred type of random access procedure corresponds to a two-step random access procedure.