Adaptive TTI Coexistence Mechanism for LTE and 5G Systems
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Solution Overview
Problem
The coexistence of existing LTE systems and new 5G systems poses a challenge due to differences in transmission time interval (TTI) capabilities, where legacy LTE UEs can only use designated TTI lengths, while 5G UEs require adaptive TTI lengths to balance latency and control signaling overhead, necessitating a mechanism for seamless coexistence.
Innovation Solution
The implementation of adaptive TTI coexistence mechanisms within the same carrier or new carrier type, using intra-carrier and inter-carrier configurations, allows legacy LTE and 5G systems to share resources, with 5G UEs configured to support adaptive TTI lengths, while legacy UEs remain unaware of the adaptive TTI structure, ensuring transparent operation and gradual migration to adaptive TTI frame structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If adaptive TTI lengths are implemented for 5G UEs, then network efficiency and latency performance are improved, but device complexity and system compatibility deteriorate due to legacy LTE UEs requiring designated TTI lengths only
Solution Approach 1:
The system segments the UE population into two distinct groups: legacy LTE UEs that operate with fixed TTI lengths and 5G UEs that operate with adaptive TTI lengths. This segmentation allows each group to operate with its optimal TTI configuration without interfering with the other, resolving the contradiction between improved network efficiency for 5G UEs and maintained compatibility for legacy LTE UEs.
Solution Approach 2:
The system applies different TTI length characteristics to different UE types: legacy LTE UEs are assigned fixed TTI lengths appropriate for their capabilities, while 5G UEs are assigned adaptive TTI lengths that can vary based on traffic conditions. This local differentiation allows each UE type to operate with the quality of TTI configuration it requires, achieving both improved efficiency for 5G and preserved compatibility for LTE.
2Loss of time
If adaptive TTI structure is introduced for 5G systems, then latency requirements are better satisfied, but control signaling overhead increases
Solution Approach 1:
The system implements dynamic TTI length adjustment for 5G UEs based on real-time traffic conditions and channel state. By making the TTI length a dynamic parameter rather than a fixed value, the system can adapt to varying latency requirements and optimize performance for different traffic types, satisfying latency requirements while managing control signaling overhead through intelligent adaptation.
Solution Approach 2:
The system changes the TTI length parameter dynamically for 5G UEs based on traffic conditions, channel quality, and latency requirements. This parameter change allows the system to optimize latency performance for time-sensitive traffic while using longer TTIs for less time-critical traffic, thereby balancing latency satisfaction with control signaling overhead reduction.
3Productivity
If legacy LTE UEs and 5G UEs share the same carrier, then resource utilization is improved, but interference management and coexistence complexity increase
Solution Approach 1:
The system merges legacy LTE UEs and 5G UEs onto the same carrier frequency, allowing both types of UEs to share the available radio resources. This merging improves overall resource utilization by enabling simultaneous operation of both UE types on a single carrier, while the network manages the coexistence through appropriate scheduling and resource allocation mechanisms.
Solution Approach 2:
The network acts as an intermediary between legacy LTE UEs and 5G UEs sharing the same carrier. It manages the coexistence by allocating resources appropriately, scheduling transmissions to minimize interference, and coordinating the operation of both UE types. This intermediary management resolves the coexistence complexity while enabling improved resource utilization through shared carrier operation.
Data Source
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AI summary
System and method embodiments are disclosed to provide mechanisms that allow adaptive transmission time interval (TTI) coexistence in Long Term Evolution (LTE) and fifth generation (5G) cellular systems. In accordance with an embodiment, a method for an adaptive TTI coexistence mechanism includes allocating, by a network controller, a LTE TTI at a first bandwidth. The first bandwidth is smaller than an available system bandwidth and is centered around a carrier frequency at a center of the available system bandwidth. The method further includes broadcasting the first bandwidth in LTE system information messages, allocating adaptive TTIs in the available system bandwidth outside the first bandwidth, and broadcasting adaptive TTI bandwidth partitioning information to adaptive TTI-capable terminals.