Inter-RAT Carrier Aggregation Feedback Scheduling
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Solution Overview
Problem
Current wireless communication systems face inefficiencies in feedback communication, as they often use resources that could be used for application data, and inter-radio access technology (RAT) carrier aggregation is challenging due to differing transmission time intervals (TTIs) between advanced and less-advanced cellular network protocols.
Innovation Solution
The system enables inter-RAT carrier aggregation by allowing user devices to transmit feedback communications via a first component carrier of one RAT, based on user plane data received via a second component carrier of a different RAT, using a next available uplink subframe or time slot, thereby optimizing resource usage across carriers with different TTIs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback communication is transmitted using dedicated resources, then reliable data packet acknowledgment is achieved, but resource availability for application data decreases
Solution Approach 1:
The patent combines feedback communication with uplink data transmission by multiplexing control information (ACK/NACK) and uplink data onto the same Physical Uplink Shared Channel (PUSCH). This merging eliminates the need for separate dedicated feedback resources, thereby maintaining reliable acknowledgment while preserving resources for application data transmission.
Solution Approach 2:
The PUSCH is designed to serve multiple functions simultaneously: it carries both uplink application data and feedback control information (ACK/NACK for downlink data, Scheduling Requests, Buffer Status Reports). This multi-functionality allows the same resource to fulfill both data transmission and feedback communication needs, resolving the resource allocation contradiction.
2Adaptability or versatility
If inter-RAT carrier aggregation is implemented with different TTI lengths, then network compatibility and bandwidth utilization are improved, but scheduling complexity and timing alignment difficulties increase
Solution Approach 1:
The patent segments the carrier aggregation into two functional parts: a primary cell (PCell) with longer TTI that handles control plane signaling and feedback communications, and secondary cells (SCells) with shorter TTI that handle user plane data transmission. This segmentation allows each component carrier to operate independently with its own timing structure, simplifying the overall scheduling complexity while maintaining support for multiple RATs with different TTI lengths.
Solution Approach 2:
The PCell acts as an intermediary between the network control plane and the SCells data plane. It receives downlink data from the network, processes feedback timing according to its longer TTI, and coordinates with SCells that operate on shorter TTIs. This intermediary role mediates the timing differences between RATs, enabling seamless inter-RAT carrier aggregation without requiring complex cross-RAT timing synchronization.
Data Source
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AI summary
The present disclosure describes methods and apparatuses for inter-radio access technology carrier (RAT) aggregation. In aspects, a user device (102) establishes a wireless link (106) for communicating with one or more base stations (104, 202) via a first component carrier (214) and a second component carrier (208, 220). The first component carrier uses a (RAT) having a first transmission time interval (TTI) and the second component carrier uses a second RAT having a second, different TTI. The user device receives user plane data via the second component carrier and analyzes the user plane data to determine whether data packets of the user plane data were successfully or unsuccessfully received by the user device (804, 806). The user device then transmits, via a next available uplink subframe or time slot of the first component carrier of the first RAT, a feedback communication based on which data packets were successfully received (808).