Adaptive Signal Transmission Method and System for Unlicensed Band Frequency Sharing in Heterogeneous Networks

LTE-U and Wi-Fi Coexistence Transmission via Collision Probability-Based Contention Window Optimization

This technology is an adaptive signal transmission method for heterogeneous networks that monitors channels to select the unlicensed band if it is vacant, or the licensed band otherwise. When using the unlicensed band, it calculates the collision probability for LTE-U users to determine the contention window (CW) and transmits using the DCF mechanism.

As the number of smart devices increases, the demand for frequency has grown, but spectrum resources remain limited, leading to situations where LTE must operate in the unlicensed bands used by Wi-Fi. Existing coexistence methods like LBT or CSAT have limitations in handling increased demand, as they fail to sufficiently reduce collisions when there are many Wi-Fi users.

This technology re-optimizes the CW size within a range of 15 to 1023 when the collision probability, calculated based on the number of LTE APs and slot transmission probability, reaches a threshold. This suppresses LTE-U channel collisions and maintains transmission efficiency even in environments with high Wi-Fi user density. It can be applied to unlicensed band integration for mobile base stations and small cells, allowing for increased data throughput without requiring additional licensed spectrum.

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Key Features:

• Monitoring channels to use the licensed band if no available band is found, or the unlicensed band used by Wi-Fi APs if available
• Calculating the collision probability of LTE-U users based on the number of LTE APs and general slot transmission probability when using the unlicensed band to determine the contention window
• Optimizing the contention window size using a CW value between a minimum of 15 and a maximum of 1023 when the collision evaluation value reaches the collision threshold
• Transmitting signals to the unlicensed band according to the DCF mechanism using the optimized contention window

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This invention was developed with support from the Ministry of Education's Next-Generation Integrated Wireless Network Optimal Frequency Sharing Technology Development project.

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