Unlicensed Band Data Reception with Inverted RTS/CTS
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Solution Overview
Problem
The hidden node problem occurs in environments where an unlicensed LTE cell and a WLAN AP coexist, and the conventional RTS/CTS procedure is ineffective in resolving this issue, leading to potential data collisions due to unsynchronized communication.
Innovation Solution
A method is proposed where a UE receives indicators from the BS to determine channel availability and transmit CTS only when necessary, using both LTE and WLAN modules to inform the BS of successful or failed channel sensing, thereby preventing collisions and ensuring data reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional RTS/CTS procedure is used in unlicensed band, then channel access coordination is provided, but hidden node problem cannot be resolved due to CTS coverage limitations
Solution Approach 1:
Instead of the conventional approach where BS sends RTS and UE sends CTS, this patent inverts the procedure by having UE send RTS and BS send CTS. This inversion allows the CTS signal from the BS to cover the hidden node area, effectively resolving the hidden node problem while maintaining channel access coordination
Solution Approach 2:
The patent introduces a dual-module architecture where the UE's WLAN module acts as an intermediary to perform channel sensing and detect hidden nodes, then communicates findings to the LTE module which sends the RTS/CTS signals. This intermediary approach enables effective hidden node detection and resolution
2Loss of information
If UE transmits CTS in response to RTS from BS, then channel availability is indicated, but hidden node collisions occur due to unsynchronized communication
Solution Approach 1:
By inverting the RTS/CTS direction (UE sends RTS, BS sends CTS), the patent ensures that the CTS signal originates from the BS which has network-wide awareness, enabling proper synchronization and preventing hidden node collisions while maintaining channel availability information transmission
3Productivity
If LTE and WLAN networks are integrated for data offloading, then data capacity is increased, but hidden node problems arise due to different network structures
Solution Approach 1:
The patent uses the UE's WLAN module as an intermediary that performs channel sensing and detects hidden nodes in the WLAN network, then communicates this information to the LTE module. This intermediary approach bridges the different network structures of LTE and WLAN, enabling reliable data offloading while preventing hidden node problems through coordinated channel access
Data Source
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AI summary
Provided are a method for receiving, by a terminal, data on an unlicensed band in a wireless communication system, and an apparatus for supporting the same. The terminal receives, from a base station, a first indicator which indicates existence of data to be transmitted to the terminal; receives a timer value from the base station; performs channel sensing in a section where a timer operates; and can transmit, to the base station on the basis of the result of performing channel sensing, either one of a second indicator, which indicates that reception of data is possible, and a third indicator, which indicates that reception of data is impossible.