LTE Unlicensed Band Scheduling via Preamble Signaling
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Solution Overview
Problem
In Long Term Evolution (LTE) networks, scheduling data transmissions in unlicensed bands is challenging due to coexistence requirements with other technologies like Wi-Fi, as Listen Before Talk (LBT) mechanisms make it difficult for eNBs to determine available transmission times, especially in centrally controlled LTE systems.
Innovation Solution
The method involves transmitting downlink control channel information using a licensed LTE bandwidth, followed by a preamble on an unlicensed bandwidth to indicate the starting symbol for data transmission on a Physical Downlink Shared Channel (PDSCH), with Clear Channel Assessment (CCA) to reserve the channel and flexible scheduling to ensure availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If LBT mechanisms are used in unlicensed bands, then coexistence with other technologies like Wi-Fi is improved, but it becomes difficult for eNBs to determine available transmission times
Solution Approach 1:
The patent introduces a preamble as an intermediary signal transmitted before actual data transmission in the unlicensed band. This preamble serves as a mediator that reserves the channel and provides clear indication to the UE about the upcoming data transmission, solving the uncertainty caused by LBT mechanisms while maintaining coexistence requirements
2Extent of automation
If centralized control is used in LTE systems, then scheduling coordination is improved, but flexibility in adapting to unlicensed band availability is reduced
Solution Approach 1:
The patent implements preliminary action by transmitting the preamble before the actual data transmission. This allows the eNB to centrally coordinate the scheduling decision and prepare the UE in advance, while still adapting to the dynamic availability of the unlicensed band by choosing when to transmit the preamble based on LBT outcomes
3Reliability
If clear channel assessment is performed, then channel availability is determined, but transmission delay increases due to reservation procedures
Solution Approach 1:
The patent segments the transmission process into distinct phases: control information transmission on licensed band, preamble transmission on unlicensed band with CCA, and data transmission on unlicensed band. This segmentation allows CCA to be performed only when necessary (before unlicensed band transmission) while maintaining reliable scheduling through the control channel, reducing overall delay compared to performing CCA before every transmission
Data Source
AI summary
At least one example embodiment discloses a system including a network element configured to transmit downlink control channel information to a user equipment (UE) using a first bandwidth, the first bandwidth being at least a portion of a long term evolution (LTE) bandwidth, transmit a preamble to the UE using a second bandwidth, the second bandwidth being a bandwidth excluding the LTE bandwidth, and the preamble indicating a scheduled data transmission, and transmit data to the UE using the second bandwidth in accordance with the downlink control channel information and the preamble.