Conditional Carrier Selection for LAA Uplink Latency
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Solution Overview
Problem
In LTE LAA operations, the average latency of data transmission is increased due to the Listen-Before-Talk (LBT) procedure, which requires UE to suspend transmissions when the channel is occupied, leading to complications in uplink operations and reduced data throughput.
Innovation Solution
Implementing conditional carrier selection, where the UE dynamically chooses an available LAA carrier for PUSCH transmission based on predetermined rules or dynamic L1 signaling, allowing for continued transmission on a different carrier when the scheduled carrier is occupied, thereby reducing the impact of negative LBT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE suspends transmissions when the channel is occupied during LBT procedure, then the channel access compliance is improved, but the data throughput and transmission latency are worsened
Solution Approach 1:
The patent implements dynamic carrier selection where the UE can switch between licensed and unlicensed carriers based on real-time channel availability. The system transitions from a static carrier assignment to a dynamic selection mechanism that adapts to changing channel conditions, allowing the UE to maintain transmissions on alternative carriers when the primary unlicensed carrier is occupied during LBT procedure.
Solution Approach 2:
The patent changes the operational parameter of carrier selection by introducing conditional carrier selection based on LBT outcomes. The UE monitors the availability of unlicensed carriers and dynamically switches to licensed carriers when unlicensed carriers are unavailable, thereby changing the transmission parameter from fixed to variable based on channel conditions.
2Adaptability or versatility
If the UE performs LBT procedure before each transmission, then the fair spectrum access is improved, but the transmission latency is worsened
Solution Approach 1:
The patent applies preliminary action by performing LBT procedure in advance before scheduled transmissions on unlicensed carriers. The UE conducts clear channel assessment ahead of time and prepares alternative licensed carrier selections, so that when LBT fails, the switch to alternative carriers can occur rapidly without additional delay, thus reducing overall transmission latency while maintaining fair spectrum access.
Solution Approach 2:
The patent introduces licensed carriers as intermediary alternatives between the UE and unlicensed carriers. When unlicensed carriers are unavailable due to LBT constraints, the licensed carriers serve as intermediate transmission paths, allowing continuous data flow without direct conflict with other unlicensed system users, thereby reducing latency while preserving fair spectrum access principles.
3Reliability
If the UE switches to a different carrier when the scheduled carrier is occupied, then the transmission reliability is improved, but the device complexity is worsened
Solution Approach 1:
The patent segments the carrier selection process into distinct components: unlicensed carrier monitoring, LBT procedure execution, licensed carrier identification, and switching logic. By dividing the complex carrier selection task into manageable segments with clear decision boundaries, the UE can implement reliable transmission through systematic carrier selection without overwhelming device complexity.
Solution Approach 2:
The patent applies preliminary action by pre-configuring the UE with both licensed and unlicensed carrier information and establishing carrier selection criteria in advance. This preliminary setup includes configuring the relationships between carriers and defining the conditions for switching, which simplifies the real-time decision-making process and reduces the complexity of dynamic carrier selection while maintaining high transmission reliability.
Data Source
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AI summary
In accordance with an example embodiment of the present invention, a method, comprising: receiving an information regarding one or more uplink grants of an assigned component carrier to use to transmit data; determining a set of uplink component carriers of licensed-assisted uplink component carriers that are considered as conditional uplink component carriers to use to transmit data; determining whether the assigned component carrier is available to transmit the data; based on determining that the assigned component carrier is not available to transmit the data, identifying a component carrier of the at least one conditional uplink component carrier of the licensed- assisted uplink component carriers that is available to transmit the data; and transmitting the data on the identified available component carrier of the licensed-assisted uplink component carriers, is disclosed.