5G Random Access Contention Resolution via UL Resource Pooling
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Solution Overview
Problem
In 5G wireless communication systems, there is a challenge in reducing inter-UE and inter-cell interference during the random access procedure, particularly in large cells with many user equipment (UEs), leading to contention where multiple UEs transmit the same PRACH sequence at the same time, causing the base station to fail in distinguishing between them and resulting in resource wastage.
Innovation Solution
The method involves receiving random access preambles with the same sequence from multiple UEs, transmitting a response message indicating a pool of uplink resources, and having UEs randomly select from this pool, thereby reducing contention by ensuring different UEs select different resources, and optionally using TRP-specific reference signals to differentiate between UEs in multi-TRP scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple UEs transmit the same PRACH sequence simultaneously, then the random access procedure can be initiated, but the base station cannot distinguish between the UEs leading to contention and resource wastage
Solution Approach 1:
The patent segments the random access procedure into multiple stages: initial PRACH sequence transmission followed by a second transmission stage. UEs that experience contention in the first stage are assigned different resources (time, frequency, or spatial) for the second stage, enabling the base station to distinguish between contending UEs through resource differentiation.
Solution Approach 2:
The patent introduces additional dimensions for resource differentiation beyond the initial PRACH sequence. By allocating different time slots, frequency resources, or spatial beams for subsequent transmissions, the system creates new dimensions for distinguishing UEs that initially used the same sequence, thereby resolving contention.
2Object-affected harmful factors
If PRACH resources are assigned to neighboring base stations to avoid interference, then inter-cell interference is reduced, but the number of available PRACH sequences per cell is limited
Solution Approach 1:
The patent merges multiple resource dimensions (time, frequency, spatial) to create a expanded resource pool for random access. By combining these dimensions, the system effectively increases the number of distinguishable random access resources available to UEs without requiring additional PRACH sequences per cell, thereby maintaining low inter-cell interference while providing sufficient resources.
Solution Approach 2:
The patent implements dynamic resource allocation for random access transmissions. Resources are assigned dynamically based on contention detection and UE behavior, allowing the system to adaptively utilize available resources across different time and frequency slots, effectively increasing the functional capacity beyond the static number of PRACH sequences.
3Area of stationary object
If a large number of UEs are served in large cells, then network coverage is improved, but contention probability increases leading to resource wastage
Solution Approach 1:
The patent implements preliminary contention detection and resolution mechanisms. The base station monitors for contention conditions and proactively assigns differentiated resources to contending UEs before they waste resources through repeated failed transmissions. This preliminary intervention prevents resource wastage by resolving contention early in the access procedure.
Solution Approach 2:
The patent incorporates feedback mechanisms where the base station provides information to UEs about resource allocation and contention status. This feedback enables UEs to adjust their transmission behavior and select differentiated resources, reducing contention-related resource wastage while maintaining support for large numbers of UEs in extended coverage areas.
Data Source
AI summary
Disclosed is a method for wireless communication. The method comprises receiving, from one or more user equipments (UEs), a plurality of random access preambles on a physical random access channel (PRACH). Each random access preamble comprises the same random access preamble sequence. A response message indicating a pool of uplink (UL) resources is transmitted to the one or more UEs. One or more transmissions on a subset of the pool of uplink resources are received from the one or more UEs.