HARQ Acknowledgement Encoding for LTE Carrier DTX Overhead
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Solution Overview
Problem
In 3GPP LTE compliant communications systems, the overhead associated with ACK/NACK control signaling significantly impacts performance, especially in higher bandwidth deployments, due to the inability to distinguish between the absence of a PDCCH and its undetected presence by the UE.
Innovation Solution
A method and system for transmitting and receiving acknowledgement information by determining HARQ responses for each component carrier, generating an information vector, encoding it, and assigning a fixed vector value to bits corresponding to DTX states, thereby reducing overhead and improving decoding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system transmits ACK/NACK feedback for all configured component carriers, then the receiver can accurately acknowledge received data, but the control signaling overhead increases significantly
Solution Approach 1:
The patent extracts and removes the redundant DTX state information from the ACK/NACK feedback mechanism. By having the receiver autonomously determine DTX states using a priori information about scheduled component carriers, the system eliminates the need to explicitly signal DTX, thereby reducing control overhead while maintaining feedback accuracy for actual data transmissions.
Solution Approach 2:
The receiver performs self-service by autonomously determining which component carriers are in DTX state based on a priori information it already possesses about scheduled carriers. This self-determination eliminates the need for explicit DTX signaling from the transmitter, reducing overhead while maintaining reliable feedback.
2Measurement precision
If the system uses explicit DTX signaling to indicate absence of PDCCH, then the receiver can accurately identify DTX states, but the control signaling complexity and overhead increase
Solution Approach 1:
The patent extracts the DTX detection function from the explicit signaling mechanism and relocates it to the receiver's autonomous determination process. The receiver uses its existing a priori information about scheduled component carriers to identify DTX states without requiring additional explicit signaling, thereby reducing complexity while maintaining detection accuracy.
Solution Approach 2:
Instead of having the transmitter explicitly signal DTX states to the receiver, the patent inverts the approach by having the receiver autonomously determine DTX states using its own a priori information. This inversion eliminates the need for complex explicit DTX signaling mechanisms while achieving the same detection accuracy.
3Loss of information
If the system transmits ACK/NACK information for every component carrier including DTX states, then complete feedback is provided, but the bandwidth efficiency decreases
Solution Approach 1:
The patent extracts redundant DTX state information from the ACK/NACK feedback stream. By having the receiver autonomously determine DTX states, the system removes unnecessary feedback bits for carriers in DTX state, thereby improving bandwidth efficiency while maintaining complete and accurate feedback information for all carriers.
Solution Approach 2:
The system discards redundant DTX signaling information that would be transmitted in the ACK/NACK feedback, as this information can be recovered by the receiver through autonomous determination using a priori information. This discarding of redundant information improves bandwidth efficiency without losing essential feedback completeness.
Data Source
AI summary
A system and method for transmitting and receiving acknowledgement information are provided. A method for communications device operations includes determining a hybrid automatic repeat request (HARQ) response for each CC in a set of configured CCs, thereby producing a set of HARQ responses, generating an information vector from the set of HARQ responses, encoding the information vector, and transmitting the encoded information vector. A sub-vector of one or more bits selected from the information vector is assigned a fixed vector value independent of HARQ responses for CCs not in a set of CCs when the set of CCs is not empty, where the set of CCs comprises at least one CC whose HARQ response is equal to DTX.