Group HARQ Feedback for LTE Unlicensed Spectrum
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Solution Overview
Problem
Wireless communications networks face challenges in maximizing the use of unlicensed spectrum due to contention-based protocols, leading to inefficiencies in data frame utilization and increased overhead, particularly in congested cellular networks.
Innovation Solution
The implementation of group hybrid automatic repeat request (HARQ) feedback messages, which group acknowledgments for multiple data subframes into a single message, transmitted over unlicensed spectrum, to minimize overhead and optimize uplink transmission, using clear channel assessment and request-to-send/clear-to-send signals to manage spectrum access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If contention-based protocol is used to access unlicensed spectrum, then spectrum sharing with WiFi is enabled, but data frame utilization efficiency deteriorates due to inability to capture spectrum over consecutive frames
Solution Approach 1:
The patent applies preliminary action by performing clear channel assessment (CCA) and sending request-to-send (RTS) signals before data transmission to reserve the unlicensed spectrum for consecutive data frames. This advance preparation enables the eNB to capture the spectrum continuously, improving data frame utilization efficiency while maintaining spectrum sharing capability with WiFi devices.
2Measurement precision
If individual HARQ feedback messages are sent for each data subframe, then acknowledgment accuracy is improved, but overhead increases
Solution Approach 1:
The patent applies merging by combining multiple individual HARQ feedback messages into a single group HARQ feedback message that acknowledges multiple data subframes simultaneously. This grouping approach maintains acknowledgment accuracy for each subframe while significantly reducing feedback overhead, as the UE sends one consolidated message instead of multiple separate messages for each data subframe.
3Loss of information
If multiple individual HARQ feedback messages are transmitted, then feedback completeness is improved, but uplink transmission resources are consumed
Solution Approach 1:
The patent applies merging by consolidating feedback for multiple data subframes into a single group HARQ feedback message. This approach maintains feedback completeness by including acknowledgments for all relevant subframes while reducing uplink transmission resource consumption, as the UE transmits one message instead of multiple separate messages.
4Reliability
If clear channel assessment and RTS/CTS signals are used to manage spectrum access, then spectrum capture reliability is improved, but protocol complexity increases
Solution Approach 1:
The patent applies preliminary action by implementing clear channel assessment (CCA) and request-to-send (RTS) signals before data transmission to reliably capture and reserve the unlicensed spectrum. While this preliminary protocol sequence increases device complexity, it ensures high spectrum capture reliability by checking channel availability and obtaining permission from other devices before transmitting data frames.
Data Source
AI summary
Methods, systems, devices, and apparatuses are described for wireless communications. In one method, a set of one or more data subframes of a data frame may be transmitted over an unlicensed spectrum, to a user equipment (UE), during a transmission period. A group hybrid automatic repeat request (HARQ) feedback message for a plurality of data subframes including at least one of the data subframes in the set of one or more data subframes may then be received over the unlicensed spectrum, from the UE, during the transmission period. In another method, a set of one or more data subframes of a data frame may be received over an unlicensed spectrum during a transmission period. A group HARQ feedback message for a plurality of data subframes including at least one of the data subframes in the set of one or more data subframes may then be transmitted over the unlicensed spectrum during the transmission period.