Contention-Free Random Access Preamble Allocation for Connected Mode Devices
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Solution Overview
Problem
Current network access signaling procedures in LTE systems, particularly for machine-type communications, result in high energy consumption and access delay due to frequent random access collisions and inefficient preamble allocation, which is detrimental for both energy-deprived devices and latency-sensitive applications.
Innovation Solution
Allocating dedicated, contention-free random access preambles to wireless devices in connected mode, allowing them to perform collision-free random access procedures when data is available for uplink transmission, thereby reducing energy consumption and access delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional random access procedures are used for machine-type communications, then network access can be established, but energy consumption increases and access delay occurs due to frequent collisions
Solution Approach 1:
The random access preambles are segmented into two distinct groups: contention-based preambles for general access and contention-free preambles for connected mode devices. This segmentation allows devices in connected mode to use dedicated preambles that do not collide with other devices, thereby reducing energy consumption from repeated access attempts while maintaining reliable network access.
Solution Approach 2:
The network node preliminarily allocates contention-free preambles to devices in connected mode before they need to perform random access. This preliminary allocation ensures that when these devices need to access the network (e.g., for uplink transmission), they can immediately use their pre-assigned preambles without collision, eliminating energy-wasting retransmissions and reducing access delay.
2Reliability
If conventional random access procedures are used, then network access is possible, but access delay increases due to collision resolution time
Solution Approach 1:
By segmenting preambles into contention-based and contention-free groups, the invention creates a dedicated access path for connected mode devices. This segmentation eliminates the collision resolution time that would otherwise be required, significantly reducing access delay while maintaining reliable network access for all device types.
Solution Approach 2:
The preliminary allocation of contention-free preambles to connected mode devices ensures that these devices have immediate access to collision-free resources when needed. This eliminates the time loss associated with collision detection, backoff, and retransmission, thereby reducing overall access delay while preserving access reliability.
3Loss of time
If dedicated preambles are allocated to all devices, then collision-free access is achieved, but signaling overhead and resource allocation complexity increase
Solution Approach 1:
Instead of allocating dedicated preambles to all devices uniformly, the invention applies local quality by providing contention-free preambles specifically to devices in connected mode that benefit most from collision-free access. This selective allocation reduces signaling overhead and allocation complexity compared to a universal dedicated preamble scheme, while still achieving collision-free access for the target devices.
Solution Approach 2:
The invention implements partial action by allocating contention-free preambles only to the subset of devices that need them (connected mode devices with uplink transmission needs), rather than to all devices. This partial allocation reduces the complexity of preamble management and signaling overhead while still achieving the collision-free access benefit where most needed.
Data Source
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AI summary
The present invention relates to a method for enabling Random Access(RA)of a wireless device being in connected mode in a cell served by a radio network node of a wireless communication system. The method in the radio network node comprises allocating (610) a contention-free RA preamble to the wireless device. The method further comprises transmitting (620) an indicator of the contention- free RA preamble to the wireless device. The indicator is thus received by the wireless device, and the indicated preamble may be used by the wireless device for performing RA in the cell at a coming RA occasion, when the RA is initiated by the wireless device when data is available at the wireless device for uplink transmission.A cooperating method in a core network node is also provided, as well as the nodes themselves.