LAA RTS CTS Dynamic Medium Reservation
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Solution Overview
Problem
In wireless communication systems using unlicensed spectrum, such as LTE-U or LAA, the coexistence of cellular and Wi-Fi signals can lead to data throughput degradation and performance issues due to hidden nodes, which existing technologies like LBT protocols struggle to fully address.
Innovation Solution
Implementing opportunistic use of request-to-send (RTS)/clear-to-send (CTS) handshakes, CTS-to-self messages, and Wi-Fi preambles/NAV messages to reduce collisions and improve timing synchronization in shared unlicensed spectrum, allowing for dynamic occupation of the wireless medium during gaps between LBT procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If listen-before-talk (LBT) procedure is used to avoid collisions in unlicensed spectrum, then collision avoidance is improved, but timing synchronization is degraded due to indeterminate gaps between LBT completion and next cellular communication start time
Solution Approach 1:
The patent applies preliminary action by performing RTS/CTS handshakes or transmitting CTS-to-self messages during the gap period between LBT completion and the next scheduled cellular communication start time. This提前 occupation of the wireless medium with reservation messages ensures that when cellular communication begins at the synchronized start time, the medium is already reserved, preventing other devices from transmitting and thus maintaining both collision avoidance and timing synchronization.
2Reliability
If RTS/CTS handshakes are performed to reduce collisions, then collision avoidance is improved, but device complexity increases due to additional message exchanges
Solution Approach 1:
The patent applies dynamics by making the RTS/CTS handshake usage dynamic and opportunistic rather than mandatory. The system dynamically selects whether to perform full RTS/CTS handshakes, CTS-to-self messages, Wi-Fi preambles/NAV messages, or simple reservation signals based on the available time gap, channel conditions, and traffic requirements. This dynamic approach reduces device complexity by avoiding unnecessary message exchanges while maintaining collision avoidance where needed.
3Productivity
If cellular communication occupies unlicensed spectrum, then data throughput is improved, but coexistence with Wi-Fi is degraded due to hidden node problems
Solution Approach 1:
The patent uses Wi-Fi preambles and NAV (Network Allocation Vector) messages as intermediary elements that bridge cellular and Wi-Fi communication systems. These messages are recognizable by both cellular devices and Wi-Fi devices, allowing cellular communication to reserve the medium in a way that Wi-Fi devices can understand and respect. This intermediary approach enables cellular communication to occupy unlicensed spectrum for improved throughput while maintaining coexistence with Wi-Fi by preventing hidden node collisions through universal recognition of the reservation signals.
Data Source
AI summary
This disclosure relates to performing cellular communication in unlicensed spectrum in a manner that accounts for the possible existence of hidden nodes by opportunistically introducing the use of RTS and CTS messages. A listen-before-talk procedure may be performed to determine whether a wireless medium is available. When the listen-before-talk procedure is complete, an amount of time until a next possible start time for communicating in the cellular communication system according to a timing synchronization scheme for the cellular communication system may be determined. The wireless medium may be occupied until the next possible start time for communicating in the cellular communication system in a manner selected based at least in part on the amount of time until the next possible start time for communicating in the cellular communication system. Cellular communication may be performed on the wireless medium at the next possible start time for communicating in the cellular communication system.