ACK/NACK Feedback Transmission in Multi-Carrier Systems
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Solution Overview
Problem
Current wireless communication systems face inefficiencies in sending feedback information, particularly in multicarrier operations, where acknowledging data transmissions across multiple downlink carriers requires effective uplink resources allocation and orthogonal spreading techniques to maintain reliable communication.
Innovation Solution
The proposed solution involves determining uplink resources based on downlink resources used for data transmissions, allowing for reduced or no orthogonal spreading, and utilizing channel selection methods to efficiently convey acknowledgement information, thereby optimizing feedback transmission in multicarrier systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If orthogonal spreading is used to send feedback information on multiple downlink carriers, then reliability of feedback transmission is improved, but uplink resource overhead and complexity increase
Solution Approach 1:
The feedback information for multiple downlink carriers is segmented into separate ACK/NACK channels. Each channel corresponds to a specific downlink carrier or group of carriers, allowing the system to distribute feedback transmission across multiple resources rather than using complex spreading across all carriers simultaneously. This segmentation reduces the overhead of orthogonal spreading while maintaining reliable feedback transmission for each carrier.
Solution Approach 2:
The patent introduces channel selection as an additional dimension for feedback transmission. Instead of relying solely on orthogonal spreading in the code domain, the system uses channel selection to assign different physical channels or resource blocks for feedback on different downlink carriers. This dimensional approach allows efficient multiplexing of feedback information without requiring full orthogonal spreading for all feedback signals.
2Productivity
If channel selection is used to transmit ACK/NACK feedback, then uplink resource efficiency is improved, but the complexity of resource mapping and signal processing increases
Solution Approach 1:
The system performs preliminary configuration of ACK/NACK channel mappings during system setup or connection establishment. The mapping between downlink carriers and uplink feedback channels is pre-determined and stored in both the base station and UE, eliminating the need for complex real-time resource mapping decisions during feedback transmission. This preliminary action simplifies the runtime processing while maintaining efficient resource utilization.
Solution Approach 2:
The patent uses downlink control information (DCI) and resource allocation messages as intermediaries to convey channel mapping information. Instead of implementing complex direct mapping logic in the UE, the base station provides mapping instructions through standardized control channels, allowing the UE to follow simple procedures based on received guidance. This intermediary approach reduces UE complexity while enabling flexible resource allocation.
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AI summary
Techniques for sending feedback information for multi-carrier operation are described. In an aspect, feedback information for data transmissions on multiple downlink carriers may be sent on at least one uplink resource determined based on at least one downlink resource used to send at least one downlink grant for the data transmissions. In another aspect, feedback information for data transmissions on multiple downlink carriers may be sent with reduced or no orthogonal spreading to enable more feedback information to be sent. In yet another aspect, feedback information for data transmissions on multiple downlink carriers may be sent with channel selection. A UE may send a transmission of at least one signal value on at least one resource to convey acknowledgement (ACK) information for data transmissions on multiple downlink carriers. The signal value(s) and resource(s) may be determined based on the content of the ACK information.