Carrier Aggregation Frame Offset for TDD Latency Reduction
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Solution Overview
Problem
In LTE Advanced systems using TD-LTE, the round trip time for end-to-end traffic is high due to TDD UL/DL configurations, particularly affecting delay-sensitive services like VoIP and real-time gaming, as there is not always simultaneous downlink and uplink transmission in each TTI, leading to latency issues.
Innovation Solution
The method involves carrier aggregation with an intelligent permutation of component carriers, where a specified offset is introduced between the start of frames of different carriers to ensure a better ratio of uplink and downlink timeslots, mimicking the FDD system's performance by ensuring coexistence of UL and DL in most TTIs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If TDD UL/DL configuration is used to extend bandwidth via carrier aggregation, then available bandwidth is improved, but round trip time increases causing latency issues
Solution Approach 1:
The patent segments the frame structure into different types (first frame type with downlink timeslot followed by uplink timeslot, second frame type with uplink timeslot followed by downlink timeslot) and alternates between them. This segmentation allows the system to maintain carrier aggregation for bandwidth extension while creating more frequent uplink opportunities, thereby reducing round trip time without sacrificing bandwidth capacity.
2Productivity
If TDD alternating transmission is used, then bandwidth efficiency is improved, but uplink transmission opportunities are reduced causing delay
Solution Approach 1:
The patent implements periodic alternation between two frame types, where each frame type provides different uplink-downlink ordering. This periodic action ensures that uplink transmission opportunities occur more frequently than in conventional TDD, improving ease of operation for uplink transmissions while maintaining overall bandwidth efficiency through structured time-division multiplexing.
Data Source
AI summary
Provided is a method for scheduling a communication link, wherein the communication link is adapted for connecting two network elements, wherein a first carrier and a second carrier are assigned to the communication link, wherein each carrier includes frames divided into timeslots, and a predefined number of timeslots is allocated for downlink communication and a predefined number of timeslots is allocated for uplink communication. The method includes scheduling the communication link for offsetting the start of the frames of the first carrier in respect to the start of the frames of the second carrier. Also provided are a network element adapted for carrying out the method and a system including the network element.