Reiterated Downlink Grant Design for LTE Signaling Overhead Reduction
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Solution Overview
Problem
In wireless communication systems, especially in LTE/LTE-Advanced networks, transmitting multiple data transmissions with unique hybrid automatic repeat request (HARQ) processes leads to significant signaling overhead and unnecessary re-transmissions due to decoding errors in control information, particularly in unlicensed or shared spectrum where consistent timing is unreliable.
Innovation Solution
The implementation of reiterated downlink grants in multiple transmission time intervals (TTIs) within a downlink burst, where each grant includes common control information and indicators for preceding and subsequent TTIs, allows the user equipment (UE) to decode data transmissions based on correctly received grants, reducing the number of HARQ processes and minimizing re-transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple data transmissions with unique HARQ processes are scheduled in different TTIs, then data transmission capability is improved, but signaling overhead increases significantly
Solution Approach 1:
The patent merges multiple control information elements into a single downlink grant message. The grant includes a New Data Indicator (NDI) field that can indicate multiple TTIs, resource allocation fields that can allocate resources across multiple TTIs, and modulation and coding scheme (MCS) fields that apply to multiple transmissions. This consolidation reduces the number of separate control messages needed while maintaining the ability to schedule multiple data transmissions with unique HARQ processes.
2Reliability
If each data transmission has a unique HARQ process, then error correction capability is improved, but the complexity of managing multiple HARQ processes increases
Solution Approach 1:
The patent segments the HARQ process management by associating each TTI within the burst with a unique HARQ process identifier. The downlink grant includes information that allows the UE to determine which HARQ process corresponds to each TTI, enabling independent error correction tracking for each transmission while maintaining overall system coordination through the single grant structure.
3Measurement precision
If control information is transmitted for each TTI separately, then decoding accuracy is improved, but transmission latency increases
Solution Approach 1:
The patent performs preliminary action by including all necessary control information for multiple TTIs in a single downlink grant transmitted at the beginning of the burst. The grant contains resource allocation, MCS, and NDI information that enables the UE to decode multiple subsequent data transmissions without needing additional control messages. This upfront provision of control information reduces latency while maintaining decoding accuracy through the inclusion of comprehensive grant details.
Data Source
AI summary
Enhanced robustness for downlink burst transmissions using reiterated grants. A user equipment (UE) may receive multiple transmissions during multiple (e.g., consecutive, etc.) transmission time intervals (TTIs) as part of a downlink burst from a base station, where at least some of the TTIs may include an iteration of a grant and a data transmission. The grants may contain some common control information for TTIs of the downlink burst, as well as an indicator of how may TTIs come before and after. The UE may identify preceding and subsequent TTIs in the downlink burst by decoding any of the grant iterations. If the UE identifies a previous transmission that has not been buffered, it may send a negative acknowledgement to the base station. If the previous transmission has been buffered, the UE may decode the previous transmission based at least in part on the current grant iteration.