Radio Base Station LBT Control for DRS Transmission
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Solution Overview
Problem
In next-generation mobile communication systems, particularly in LTE/LTE-A systems operating in unlicensed bands, there is a challenge in ensuring adequate downlink (DL) transmission while managing measurement signals and DL data at different timings, especially when interference control mechanisms like Listen Before Talk (LBT) are employed, which can limit the opportunities for discovery reference signals (DRS) transmission and impact DL data transmission.
Innovation Solution
Implementing a radio base station and user terminal with a processor that controls the transmission of DL data and measurement signals based on listening results, applying different conditions for listening operations before DL data and measurement signal transmissions, such as random backoff, predetermined defer periods, and configuring listening windows to prioritize DRS transmission opportunities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If Listen Before Talk (LBT) mechanism is employed for interference control in unlicensed bands, then interference between different systems is reduced, but transmission opportunities for discovery reference signals and DL data are limited
Solution Approach 1:
The patent segments the LBT procedure into different types: initial sensing for DL data transmission and sensing based on Contention Window (CW) adjustment. By dividing the sensing mechanism into distinct segments with different rules, the system can prioritize DRS transmission while maintaining interference control, thus resolving the contradiction between reducing interference and ensuring transmission opportunities.
Solution Approach 2:
The patent applies different sensing conditions to different signal types: DRS transmission uses sensing based on CW adjustment with predetermined defer periods, while DL data transmission uses initial sensing with random backoff. This local differentiation of quality/conditions allows DRS to secure transmission opportunities without compromising overall interference control.
2Object-affected harmful factors
If sensing based on Contention Window (CW) adjustment is applied to DL data transmission, then interference control is improved, but DRS transmission opportunities are reduced
Solution Approach 1:
The patent implements preliminary action by configuring a predetermined defer period for DRS transmission before the actual sensing based on CW adjustment. This advance preparation ensures that DRS transmission opportunities are secured in advance, preventing loss of time while still maintaining interference control through the subsequent sensing mechanism.
Solution Approach 2:
The patent introduces dynamics by making the sensing conditions adaptive: the CW size can be adjusted based on sensing results, and the defer period is configured dynamically. This allows the system to balance interference control with ensuring sufficient DRS transmission opportunities under varying channel conditions.
3Ease of operation
If random backoff is applied to listening before DL data transmission, then channel access fairness is improved, but transmission delay increases
Solution Approach 1:
The patent applies partial action by using random backoff only for DL data transmission, not for DRS transmission. This selective application maintains channel access fairness for data transmissions while avoiding the time penalty for critical DRS transmissions, thus resolving the contradiction between fairness and delay.
Data Source
AI summary
A radio base station is disclosed. The radio base station has a transmitter that transmits downlink (DL) data and a measurement signal to a user terminal and a processor that executes control of transmission of the DL data and the measurement signal based on a result of listening, which is performed before signals are transmitted. The processor applies different conditions to listening that is performed before the DL data is transmitted and listening that is performed before the measurement signal is transmitted.