RF Echo Cancellation for Full-Duplex Wireless Capacity
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Solution Overview
Problem
Current wireless communication systems face challenges in exploiting full time/frequency capacity due to interference from high power echo signals, which can swamp weak receive signals, especially in duplex communications where Tx and Rx share the same frequency and time resources, leading to poor signal decoding.
Innovation Solution
Implementing an RF echo cancellation system with a novel vector modulator and weight calculator to perform echo cancellation in the analog domain, using a two-tap filter to estimate and subtract echo signals, thereby minimizing echo power and enhancing signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If separate time and frequency resources are employed for downlinks and uplinks (TDD or FDM), then interference between transmission and reception is reduced, but the full time/frequency capacity for wireless communications cannot be exploited
Solution Approach 1:
The patent enables continuous simultaneous transmission and reception by eliminating the need to alternate between Tx and Rx modes. The analog echo cancellation system continuously suppresses echo interference during full-duplex operation, allowing the wireless medium to be fully utilized without time-division gaps, thereby achieving continuity of useful action and maximizing communication capacity.
Solution Approach 2:
The patent transitions from time-division or frequency-division separation to spatial-spectral coexistence by operating in the same time and frequency resources. The analog echo cancellation technique operates in the RF domain to manage interference, adding a new dimension of interference management that enables full exploitation of time/frequency capacity simultaneously for both directions.
2Productivity
If the same RF carrier is used for simultaneous transmission and reception, then full time/frequency capacity is exploited, but high power transmit signals leak into the receive chain as echoes that swamp weak receive signals
Solution Approach 1:
The patent converts the harmful high-power transmit signal into a useful reference for echo cancellation. By capturing a portion of the transmit signal and processing it through the analog echo cancellation system, the harmful echo leakage is transformed into a controlled cancellation signal that actively suppresses interference in the receive chain, allowing simultaneous Tx/Rx operation.
Solution Approach 2:
The patent introduces an intermediary analog echo cancellation system between the transmit and receive chains. This intermediary component processes the transmit signal to generate cancellation signals that are combined with the received signal, effectively mediating the interference problem and enabling clean simultaneous reception despite high-power transmission.
3Ease of operation
If impedance mismatching occurs at antenna and cable, then echoes appear at the receive chain, but these echoes can be cancelled through adaptive filtering techniques
Solution Approach 1:
The patent implements feedback through the analog echo cancellation system that continuously monitors the transmit signal and adaptively generates cancellation signals. The system uses feedback from the transmit chain to model and cancel the echo paths caused by impedance mismatches, dynamically adjusting to changing conditions and maintaining clean reception despite mismatches.
Solution Approach 2:
The patent employs parameter changes through adaptive filtering coefficients in the analog echo cancellation system. The filter parameters are dynamically adjusted based on the observed echo characteristics and transmit signal conditions, allowing the system to adapt to varying impedance mismatches and optimize echo suppression in real-time.
Data Source
AI summary
An apparatus may include an antenna and a transceiver coupled to the antenna, the transceiver including a receiver operative to receive a radio-frequency (RF) signal and a transmitter operative to transmit a RF signal. The apparatus may also include an RF echo cancellation module coupled to the receiver and the transmitter, the RF echo cancellation module operative to generate an analog echo cancellation signal for the received RF signal based on a delayed version of the transmit RF signal. Other embodiments are disclosed and claimed.