HARQ ACK/NACK Vector Encoding for Multi-Carrier LTE Feedback
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Solution Overview
Problem
In 3GPP LTE compliant communications systems, the overhead associated with ACK/NACK control signaling can significantly impact performance, especially with higher bandwidth deployments, necessitating a method to reduce this negative impact.
Innovation Solution
A method that determines HARQ responses for each component carrier, generates an information vector, encodes it, and assigns a fixed vector value to undetected transmissions, utilizing a priori information to improve decoding performance and reduce overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional ACK/NACK feedback mechanisms are used in multi-carrier systems, then transmission reliability is maintained, but signaling overhead increases significantly
Solution Approach 1:
The patent combines ACK/NACK feedback for multiple component carriers into a single uplink subframe. Instead of sending separate feedback signals for each carrier, the system merges all HARQ acknowledgments into one consolidated feedback message transmitted on the PUCCH, thereby reducing signaling overhead while maintaining reliable feedback for all carriers
Solution Approach 2:
The PUCCH resource is designed to handle multiple functions simultaneously - it carries HARQ acknowledgments for multiple component carriers, supports both ACK and NACK states, and can adapt to different feedback scenarios (new transmission vs. retransmission) using a single unified channel structure
2Measurement precision
If separate feedback is sent for each component carrier, then decoding accuracy is improved, but resource consumption increases
Solution Approach 1:
The patent merges feedback for multiple component carriers into a single PUCCH transmission. The UE generates one consolidated HARQ-ACK codebook that includes acknowledgments for all configured component carriers, and transmits this single codebook on one PUCCH resource, reducing resource consumption while preserving decoding accuracy through proper bit mapping and channel coding
3Ease of operation
If DTX state is indicated by silence, then feedback simplicity is achieved, but ambiguity arises between no transmission and failed detection
Solution Approach 1:
The patent introduces an explicit DTX indicator bit as an intermediary signal element. This bit acts as a mediator that clearly distinguishes between the case where the UE detected no PDCCH (DTX state) and cases where PDCCH was detected but transmission failed. The eNB can interpret this bit to correctly understand the UE's state and make appropriate scheduling decisions
Data Source
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AI summary
A method for communications device operations, the method comprising: determining a hybrid automatic repeat request (HARQ) response for each component carrier (CC) in a set of CCs thereby producing a set of HARQ responses; generating an information vector from the set of HARQ responses, wherein the information vector comprises one or more bits respectively corresponding to a CC in the set of CCs, and a bit of the one or more bits is assigned a fixed value if HARQ response of a corresponding CC is set to DTX in response to no transmission detected over the CC; encoding the information vector; and transmitting the encoded information vector.