Full-Duplex Transceiver Self-Interference Cancellation
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Solution Overview
Problem
Wireless communication networks face interference and collisions due to the 'hidden node problem' and 'exposed node problem', where nodes cannot detect other users of the medium because of limited propagation range, leading to reduced network performance and spatial reuse.
Innovation Solution
Implementing a full-duplex communication system with self-interference cancellation, allowing nodes to transmit and receive simultaneously on the same channel by using knowledge of the transmitted signal to estimate and remove interference, thereby enabling simultaneous transmission and reception without collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CSMA/CA with RTS/CTS is used to reduce collisions, then collision avoidance is improved, but message passing overhead and delay increase significantly
Solution Approach 1:
The patent extracts the essential function of collision avoidance from the RTS/CTS handshake mechanism and implements it through full-duplex self-interference cancellation. The transmitter cancels its own transmitted signal at the receiver, eliminating the need for separate RTS/CTS reservation messages and reducing protocol overhead while maintaining collision avoidance capability.
Solution Approach 2:
The transmitter performs self-interference cancellation using knowledge of its own transmitted signal, making the system self-managing regarding interference. This self-service approach eliminates the need for external coordination mechanisms like RTS/CTS, reducing message passing overhead while maintaining reliable communication.
2Productivity
If full-duplex transmission with self-interference cancellation is implemented, then spatial reuse is improved, but device complexity increases
Solution Approach 1:
The patent uses a copy of the transmitted signal (available at the transmitter) to generate the cancellation signal. This copying approach allows the transmitter to replicate its own signal characteristics for cancellation purposes, enabling full-duplex operation while managing the complexity through signal processing rather than additional hardware.
3Reliability
If RTS/CTS mechanism is used to alert nearby nodes, then frame collision frequency is reduced, but throughput decreases due to extra message passing
Solution Approach 1:
The patent extracts the collision avoidance function from the RTS/CTS protocol and implements it through physical-layer self-interference cancellation. This eliminates the need for additional control messages (RTS/CTS) that consume bandwidth and time, thereby improving throughput while maintaining frame collision reduction.
Solution Approach 2:
The full-duplex transmitter performs self-interference cancellation autonomously, eliminating the need for RTS/CTS reservation messages. This self-service mechanism reduces the number of protocol messages exchanged, decreases overhead, and improves overall throughput while maintaining reliable frame transmission.
Data Source
AI summary
Full-duplex wireless communication is described. In an embodiment, a transceiver device having a transmitter circuit and a receiver circuit receives a data packet sent over a shared communication medium. In the embodiment, the transceiver reads the header of the data packet and starts transmitting an output signal on the same shared communication medium. Embodiments are described in which, whilst the transmission of the output signal is ongoing, the transceiver receives an impaired data signal which is made up of the payload of the data packet and interference from the output signal. In the embodiment, a cancellation signal is derived from the output signal, and this is combined with the impaired data signal to remove the interference and recover the payload of the data packet.