Listen Before Talk Protocol for Discovery Reference Signal Transmission
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Solution Overview
Problem
The challenge in wireless communication systems is to ensure efficient coexistence with existing unlicensed band users, particularly in the 5 GHz band, where LTE-U operations require effective listen-before-talk (LBT) mechanisms for discovery reference signal (DRS) transmission to avoid interference and optimize channel usage.
Innovation Solution
Implementing a listen-before-talk (LBT) protocol with specific criteria for DRS transmission in unlicensed spectrum, including channel assessment through idle sensing and reservation signals, to determine channel availability and ensure accurate radio resource measurements, allowing for efficient DRS transmission within defined timing configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If LBT protocol is implemented for DRS transmission in unlicensed spectrum, then coexistence with other unlicensed users is improved, but transmission reliability deteriorates due to channel access uncertainty
Solution Approach 1:
The patent performs LBT channel assessment before DRS transmission to ensure the channel is idle, and transmits a reservation signal immediately after successful LBT to secure the channel for the upcoming DRS transmission. This preliminary channel securing action improves transmission reliability by reducing the risk of channel contention during the actual DRS transmission.
Solution Approach 2:
The patent implements a feedback mechanism where the base station monitors channel conditions through LBT, adjusts transmission timing based on channel availability, and uses reservation signals to maintain channel access. This closed-loop approach allows the system to adapt to dynamic unlicensed spectrum conditions while maintaining reliable DRS transmission.
2Reliability
If LBT protocol with reservation signals is used, then channel access reliability is improved, but transmission delay increases
Solution Approach 1:
The patent performs LBT assessment only for the specific time window when DRS transmission is scheduled, rather than continuous monitoring. The reservation signal is transmitted only when needed to bridge the gap between LBT success and DRS transmission start. This partial action approach reduces unnecessary delays while maintaining reliability when required.
Solution Approach 2:
The patent performs LBT channel assessment in advance of the scheduled DRS transmission time, and if the channel is idle, transmits a reservation signal to secure the channel. This preliminary channel securing allows the DRS transmission to proceed at the scheduled time without delay, even if other devices become active nearby.
3Productivity
If DRS transmission timing is flexible to accommodate LBT, then channel utilization is improved, but measurement accuracy deteriorates
Solution Approach 1:
The patent transmits the reservation signal for a duration that fully covers the period from LBT success to DRS transmission start, ensuring complete channel protection. This excessive reservation signaling duration guarantees that even if DRS timing is delayed to improve channel utilization, the measurement accuracy is preserved by preventing any interference during the critical measurement window.
Data Source
AI summary
Techniques for mobile communication in an unlicensed frequency band are discussed. A network device (e.g., an evolved NodeB, or other cell network device) can generate a listen before talk (LBT) protocol in order to determine whether an unlicensed carrier of a secondary cell device is idle or busy. The LBT protocol can be generated as a one shot LBT within a two symbol duration of a potential downlink (DL) transmission burst, or multiple times within the two symbol duration. In response to an idle state detection, a discovery reference signal (DRS) can be transmitted. In response to the LBT protocol and the DRS transmission being misaligned, a reservation signal can be generated to reserve the unlicensed carrier for the DL transmission.