V2X Request Response Protocol Priority Handling
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Solution Overview
Problem
In vehicle-to-everything (V2X) wireless communication systems, existing request and response techniques such as listen-before-talk (LBT) and request-to-send/clear-to-send (RTS/CTS) are inadequate in mitigating signal interference when multiple transmitters simultaneously multicast transmissions, leading to hidden node problems and interference among receivers.
Innovation Solution
A request/response procedure where transmitters multicast a request message with priority indications, and receivers respond only to the message with the highest priority, allowing the corresponding transmitter to proceed with data transmission while others cede the channel, thereby reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple transmitters simultaneously multicast transmissions in V2X systems, then communication coverage and data delivery are improved, but signal interference and hidden node problems worsen
Solution Approach 1:
The patent implements a request-to-send (RTS) message transmission before actual data transmission. This preliminary action allows the transmitter to reserve the channel and notify receivers in advance, enabling receivers to perform clear-to-send (CTS) procedures and prepare for incoming transmissions. This prevents simultaneous transmissions by establishing a reservation mechanism that resolves the hidden node problem before interference occurs.
Solution Approach 2:
The patent employs a feedback mechanism where receivers send CTS messages back to transmitters in response to RTS messages. This feedback loop allows the system to confirm channel availability and coordinate transmissions. The CTS message contains information about the receiver's readiness and channel status, enabling the transmitter to adjust its transmission timing and power to avoid interference with other simultaneous communications.
2Object-affected harmful factors
If listen-before-talk (LBT) techniques are used to mitigate interference, then signal collision is reduced, but effectiveness deteriorates in multi-transmitter multicast scenarios due to hidden node problems
Solution Approach 1:
The patent introduces RTS and CTS messages as intermediary signaling elements that mediate between transmitters and receivers. These intermediary messages establish a handshake protocol that coordinates channel access. The RTS message acts as a reservation request, and the CTS message serves as an acknowledgment and permission to transmit. This intermediary communication layer solves the hidden node problem by ensuring all parties are aware of the transmission schedule before actual data exchange occurs.
Solution Approach 2:
The patent performs channel reservation through RTS message transmission before actual data transmission begins. This preliminary channel reservation allows the system to establish transmission rights and notify all receivers in advance. By performing this action beforehand, the system prevents simultaneous transmissions and resolves the limitations of LBT in multicast scenarios where hidden nodes cannot detect each other's transmissions.
3Reliability
If request-to-send/clear-to-send (RTS/CTS) techniques are applied, then hidden node problems are addressed, but system complexity increases in multi-transmitter multicast scenarios
Solution Approach 1:
The patent segments the communication process into distinct phases: RTS message transmission, CTS message reception and processing, and actual data transmission. This segmentation allows each phase to be handled independently with specific protocols and procedures. The RTS phase handles channel reservation, the CTS phase handles acknowledgment and coordination, and the data transmission phase handles actual payload exchange. This segmentation reduces complexity by breaking down the complex RTS/CTS handshake into manageable, standardized steps that can be implemented systematically in multi-transmitter scenarios.
Solution Approach 2:
The patent designs the RTS and CTS messages with universal structures that can handle multiple functions. The RTS message serves both as a channel reservation request and as a notification to receivers. The CTS message simultaneously acknowledges the RTS, grants transmission permission, and provides channel status information. This multi-functionality reduces the need for separate specialized messages and procedures, thereby reducing overall system complexity while maintaining reliable hidden node problem resolution.
Data Source
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AI summary
Methods, systems, and devices for wireless communications are described. A transmitting user equipment (UE) such as a vehicle may identify data for transmission and transmit a request message to one or more receiving UEs (e.g., other vehicles). The request message may be associated with a first priority. The transmitting UE may monitor resources for a response message. The response message may be associated with a second priority. If the transmitting UE receives a response message, the transmitting UE may determine whether to transmit the data based on a comparison of the priorities of the request message and the response message. In some cases, the transmitting UE may transmit the data if the transmitting UE does not receive any response message. A receiving UE may receive the request message and determine whether to transmit a response message based on the priority and/or the receive power of the request message.