Random Access Resource Allocation for Beam Handover
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Solution Overview
Problem
In New Radio (NR) systems operating in mmWave frequency bands, beam mobility within a cell is handled at physical and MAC sublayers, making handover procedures complex, especially when user devices switch between beams, as current methods do not efficiently manage random access resource allocation for unsuccessful attempts, leading to suboptimal resource usage.
Innovation Solution
A method involving a user device transmitting first and second random access requests using different preambles to handover target cells or beams, storing information on not-responded requests, and transmitting this information for resource allocation optimization, while an access node analyzes this information to avoid allocating resources used for unsuccessful attempts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If random access requests are transmitted using multiple preambles to different beams during handover, then the reliability of connection establishment is improved, but the complexity of random access resource allocation increases
Solution Approach 1:
The network pre-configures multiple random access preambles and their associated beam information before handover occurs. The user equipment stores this preamble information in advance, allowing it to quickly transmit random access requests to multiple beams simultaneously when handover is triggered, improving connection reliability without increasing real-time processing complexity
Solution Approach 2:
The system implements feedback mechanisms where the network monitors which preambles are successfully received and which beams respond. This feedback information is used to optimize future random access resource allocation, allowing the system to learn from unsuccessful attempts and improve resource distribution over time
2Reliability
If random access resources are allocated to multiple beams for handover attempts, then the probability of successful handover is improved, but the resource utilization efficiency deteriorates
Solution Approach 1:
Instead of allocating random access resources to all possible beams, the system allocates preambles to a selected subset of beams based on current network conditions, user equipment capability, and historical performance. This partial action approach ensures sufficient handover success probability while avoiding waste of resources on beams with poor performance or low likelihood of success
Solution Approach 2:
The system dynamically adjusts random access resource allocation parameters such as preamble count, time slot allocation, and frequency resources based on changing network conditions. When handover success rate is high, resources are consolidated; when failure rate increases, resources are expanded to additional beams, optimizing the balance between success probability and resource efficiency
3Productivity
If information on unsuccessful random access attempts is stored and transmitted, then the optimization of resource allocation is improved, but the signaling overhead increases
Solution Approach 1:
The system extracts only the most critical information from unsuccessful random access attempts, such as preamble indices and associated beam identifiers, while omitting redundant details. This selective extraction provides sufficient data for resource allocation optimization while minimizing the amount of signaling data that needs to be transmitted back to the network
Solution Approach 2:
The same random access preamble information serves multiple purposes: it is used for the actual random access transmission, for identifying failed attempts, and for optimizing future resource allocation. This multi-functionality reduces the need for separate signaling messages, as the existing preamble structures are leveraged for multiple functions simultaneously
Data Source
AI summary
An apparatus is configured to transmit at least one first random access request by using a first preamble to a first handover target cell or to a first beam provided by a serving cell. If the first random access request is responded, the apparatus carries out a synchronization to the first handover target cell or to the first beam provided by the serving cell. If the first random access request is not responded, the apparatus transmits at least one second random access request by using at least one second preamble to at least one second handover target cell or to at least one second beam provided by the serving cell. The apparatus stores information on not-responded first or second random access requests or resources not used for random access requests, wherein the information comprises preambles used. The apparatus transmits, after being synchronized, the stored information to either the first handover target cell, the at least one second handover target cell or the serving cell for being used in random access resource allocation.