UE-Assisted Channel Reservation for Indoor LTE-WLAN Interference
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Solution Overview
Problem
Existing interference coordination methods in unlicensed spectrum face challenges in detecting indoor WLAN transmissions, leading to failed LTE transmissions due to strong interference, especially since 80% of UEs are indoor and eNBs struggle to sense nearby indoor WLAN STA signals, resulting in reduced communication reliability.
Innovation Solution
Allowing UEs to perform medium sensing and send Clear to Send (CTS) messages instead of eNBs, enabling localized channel reservations and reducing interference by confining data transmissions to successfully reserved channels, thereby minimizing the impact on nearby WLAN STAs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If eNB performs medium sensing to detect WLAN transmissions, then interference coordination can be implemented, but eNB fails to detect indoor WLAN transmissions due to signal attenuation, resulting in failed LTE transmissions
Solution Approach 1:
Instead of having the eNB perform medium sensing to detect WLAN transmissions, the patent inverts the approach by having UEs perform the sensing. Since UEs are indoors with the WLAN transmissions, they can detect the signals that eNB cannot detect due to building attenuation. The UE then sends a CTS message to reserve the medium, solving the detection problem by reversing who performs the sensing function.
2Reliability
If eNB sends CTS message for channel reservation, then centralized control is maintained, but the CTS message cannot effectively reserve indoor channels due to eNB's inability to sense indoor transmissions
Solution Approach 1:
The patent segments the medium sensing and channel reservation functions from the eNB and assigns them to individual UEs. Each UE that needs to transmit data performs its own medium sensing and sends its own CTS message. This segmentation allows each UE to effectively reserve its local indoor channel since it is physically present with the WLAN transmissions, while the eNB maintains overall scheduling control through downlink grants.
3Reliability
If UEs perform medium sensing and send CTS messages, then localized channel reservation is achieved, but device complexity increases for UE
Solution Approach 1:
The patent implements self-service by enabling UEs to autonomously perform medium sensing and send CTS messages for their own channel reservation. Each UE independently detects WLAN transmissions in its local environment and reserves the medium as needed for its data transmission. This self-service approach distributes the sensing and reservation burden across multiple UEs rather than requiring complex centralized eNB sensing, reducing overall system complexity while improving indoor reliability.
Data Source
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AI summary
A user equipment (UE) can reserve shared spectrum between two wireless protocols upon the request from a tower. For example, an enhanced node B (eNB or eNodeB) transmits a message to associated UEs including a set of candidate UEs, a length of time to reserve, and a frequency band to use. UEs perform medium sensing on the specified spectrum if a UE finds its identifier in the set of candidate UEs. Candidate UEs transmit a clear to send (CTS) message with channel reservation information if the medium is idle. A result of the success or failure of the CTS transmission attempt is sent back to the eNB. Upon receiving the feedback information from the UEs, the eNB starts sending data to those UEs that sent the positive feedback on the channel reservation.