Grantless Uplink Control Signaling for Unlicensed LTE Throughput
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Solution Overview
Problem
The inefficiency of scheduled uplink transmissions in LTE systems operating in unlicensed spectrum due to the need for multiple LBT procedures and subframe latency, leading to degraded uplink throughput performance.
Innovation Solution
Implementing a non-scheduled, grantless uplink transmission mode for user equipment (UE) using new downlink control information (DCI) formats that include modulation coding scheme (MCS) information, channel state information (CSI), and hybrid automatic repeat request (HARQ) acknowledgment feedback, allowing UE to transmit data without receiving a UL grant, thereby eliminating the need for eNB to perform LBT procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If scheduled uplink transmission mode is used in unlicensed spectrum, then system control and scheduling capability is maintained, but uplink throughput performance is degraded due to multiple LBT procedures and subframe latency
Solution Approach 1:
The patent extracts and removes the LBT procedure requirement from the scheduled transmission path by implementing grantless uplink transmission. The UE transmits uplink data without waiting for UL grant and LBT completion, directly eliminating the time-consuming LBT steps while maintaining system control through DCI-based scheduling information.
Solution Approach 2:
The patent applies preliminary action by pre-configuring UL grant information through DCI formats that contain scheduling information, MCS, and resource allocation. This allows the UE to prepare transmission parameters in advance and execute immediate transmission without waiting for traditional scheduled grant confirmation, reducing latency while maintaining control.
2Productivity
If scheduled uplink transmission mode is used in unlicensed spectrum, then system control and scheduling capability is maintained, but the number of LBT procedures increases causing performance degradation
Solution Approach 1:
The patent extracts and removes the LBT procedure requirement from the scheduled transmission path by implementing grantless uplink transmission. The UE transmits uplink data without waiting for UL grant and LBT completion, directly eliminating the time-consuming LBT steps while maintaining system control through DCI-based scheduling information.
3Productivity
If non-scheduled grantless transmission mode is implemented, then LBT procedures and latency are eliminated improving throughput, but system control and scheduling capability is reduced
Solution Approach 1:
The patent introduces DCI formats as an intermediary mechanism that carries scheduling information, MCS, and resource allocation details. This intermediary maintains system control and scheduling capability by providing the UE with necessary transmission parameters without requiring traditional scheduled grant confirmation, thus preserving control while enabling grantless transmission.
Solution Approach 2:
The patent implements feedback mechanisms where the eNB monitors uplink transmissions and provides scheduling information through DCI formats. This feedback loop maintains system control by allowing the eNB to manage resource allocation and adjust transmission parameters based on channel conditions, even in grantless mode.
Data Source
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AI summary
Methods and apparatus are described by which user equipment (UE) transmits data over unlicensed spectrum using systems, such as MulteFire and enhanced Licensed-Assisted Access (eLAA) systems. Embodiments transmit data over a physical uplink shared channel (PUSCH) channel to an evolved Node B (eNB) without first receiving an uplink (UL) grant from the eNB. Embodiments of downlink control information (DCI) and its transmission and channel sensing schemes are described that contain information that may be used by the UE to transmit data over unlicensed spectrum.