Control Signaling via Discovery Signals in Unlicensed Spectrum
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Solution Overview
Problem
Current LTE communication methods incur significant delays in accessing the medium when networks are congested, particularly due to the need for complete random backoff procedures when transmitting control signals on unlicensed carriers.
Innovation Solution
The method involves sending control signals along with discovery signals without data, utilizing a shorter period for determining medium availability, thereby avoiding the need for a complete random backoff procedure, and allowing faster transmission of control information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complete random backoff procedure is used for transmitting control signals on unlicensed carriers, then medium access reliability is improved, but transmission delay increases significantly
Solution Approach 1:
The patent segments the medium access procedure into two distinct paths: a shortened backoff procedure for control signals and the complete random backoff procedure for data transmissions. This segmentation allows control signals to use a faster access path while data transmissions maintain the full collision avoidance mechanism, thus resolving the contradiction between reliability and delay.
Solution Approach 2:
The patent introduces dynamic behavior by allowing the backoff procedure duration to vary based on the signal type. Control signals utilize a dynamic shortened backoff period, while data transmissions use the standard complete backoff procedure. This dynamic adaptation enables the system to optimize for speed when transmitting control information while preserving collision avoidance for data.
2Speed
If shorter period for determining medium availability is used for control signals, then transmission speed is improved, but collision risk increases
Solution Approach 1:
The patent applies local quality by implementing different medium access characteristics for different signal types. Control signals receive a localized optimization with shortened backoff procedure, while data transmissions maintain the standard complete backoff procedure. This localized differentiation allows speed improvement for control signals without compromising the collision avoidance reliability of data transmissions.
3Device complexity
If control signals are sent with data transmissions, then protocol complexity is reduced, but control signaling delay increases
Solution Approach 1:
The patent extracts control signal transmission from the data transmission process by implementing a separate, independent medium access procedure. Instead of waiting for data transmission opportunities, control signals can be transmitted independently using the shortened backoff procedure. This extraction eliminates the dependency that caused delay while maintaining protocol manageability through clear separation of concerns.
Data Source
AI summary
A method performed by a first communication device for sending one or more control signals to a second communication device. The first communication device and the second communication device operate in a wireless communications network. The first communication device determines, during a first period, that a transmission medium is available for sending the one or more control signals to the second communication device. The first communication device then sends, to the second communication device, the one or more control signals along with a discovery signal, via the transmission medium. The discovery signal and the one or more control signals are sent without data after the first period. The first period is shorter than a second period for determining that the transmission medium is available for sending the data.