Dynamic Uplink Resource Reuse in LTE eNB via TTI Segmentation
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Solution Overview
Problem
In communications networks, particularly in LTE and 5G, persistent uplink resource allocation can lead to wasted system capacity due to reserved resources being unused by users with sporadic data transmissions, which hinders efficient use of resources and increases latency.
Innovation Solution
The proposed solution involves subdividing long TTIs into shorter sub-TTIs and dynamically reallocating unused fractions of TTIs to other users, with high-priority users allocated to long TTIs and low-priority users to short TTIs, allowing for conditional grants based on usage detection by the eNB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If persistent uplink resource allocation with 1 TTI periodicity is provided to guarantee deterministic latency, then latency is reduced and reliability is improved, but system capacity is reduced and resources are wasted when unused
Solution Approach 1:
The long TTI (1 ms) is divided into multiple short TTIs (e.g., 2, 4, or 7 OFDM symbols each). This segmentation allows the system to allocate resources at a finer granularity, enabling other UEs to use unused portions of the long TTI resources while the first UE maintains its persistent allocation for deterministic latency.
Solution Approach 2:
The system dynamically determines whether to allocate short TTI resources to additional UEs based on whether the first UE actually uses its long TTI resources. The eNB monitors resource usage and adjusts allocations in real-time, transitioning from static persistent allocation to dynamic shared allocation to optimize system capacity.
2Loss of time
If long TTI resources are reserved for a UE with sporadic data transmissions, then deterministic latency is guaranteed, but system capacity is reduced due to blocked resources
Solution Approach 1:
By segmenting the long TTI into short TTIs, the system creates allocatable units that can be dynamically assigned. When the first UE has sporadic data, only the necessary short TTIs are used by the first UE, while remaining short TTIs can be allocated to other UEs, thus improving system capacity without increasing latency for the first UE.
Solution Approach 2:
The same physical resources (time-frequency blocks within the long TTI) serve multiple functions: they guarantee deterministic latency for the first UE when needed, and simultaneously provide additional capacity for other UEs when the first UE's resources are unused. This multi-functionality resolves the contradiction between latency guarantee and capacity utilization.
3Productivity
If short TTI resources are allocated to additional UEs, then system capacity is improved, but deterministic latency guarantee may be compromised
Solution Approach 1:
The segmentation of long TTI into short TTIs enables precise control over resource allocation. The eNB can allocate specific short TTI segments to additional UEs while ensuring that the critical early segments (which determine latency for the first UE) remain dedicated. This granular control maintains deterministic latency while improving capacity.
Solution Approach 2:
The eNB monitors the actual usage of long TTI resources by the first UE and uses this feedback to make intelligent allocation decisions for short TTIs. When the first UE uses its resources, the eNB prevents allocation to other UEs, thus preserving deterministic latency. When resources are unused, the eNB allows allocation to improve system capacity.
Data Source
AI summary
The invention refers to a method in an access node or evolved Node B, eNB, (110) for granting uplink, UL, transmission resources to one or a plurality of user equipments, UEs, (120-1, 120-2), comprising allocating an uplink transmission resource over one or a plurality of transmission time intervals, TTIs to a first UE (120-1); and granting an uplink transmission resource of a fraction of a certain TTI to a second UE (120-2), if it is detected that the uplink resource is not used for uplink transmission in the certain TTI by the first UE (120-1); the invention further refers to an corresponding eNB (110), corresponding first UE (120-1) a second UE (120-2), and corresponding methods performed in the UEs.