Self-Interference Canceler Using Equalizer Assisted Polynomial Linearity
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Solution Overview
Problem
Modern cellular communication systems face limitations in coverage range due to limited output power of mobile terminals, particularly in TDD systems, which restricts the power spectral density and requires more base stations to cover an area, and struggle with self-interference issues in FDD systems requiring separate bands and isolation.
Innovation Solution
A transceiver architecture that includes a processor to estimate non-linear components in the transmit path and applies an equalizer function to received signals, followed by self-interference cancellation circuitry to remove leakage, allowing concurrent uplink and downlink communication without the need for separate bands or isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If TDD systems split uplink and downlink in time domain, then device complexity is reduced, but productivity decreases due to duty cycle limitation
Solution Approach 1:
The patent merges TDD and FDD operations into a single transceiver that can concurrently transmit and receive on the same frequency band. The self-interference cancellation technique enables the system to combine the simplicity of TDD (single band) with the continuous operation of FDD (simultaneous UL/DL), resolving the contradiction between device complexity and productivity.
Solution Approach 2:
The patent converts the harmful self-interference (transmit signal leaking to receive antenna) into a beneficial feature by using it to train and optimize the self-interference cancellation algorithm. This measured self-interference signal is used to estimate channel characteristics and improve the cancellation performance, turning a disadvantage into an advantage for system productivity.
2Productivity
If FDD systems use separate bands for uplink and downlink, then productivity increases with continuous transmission, but device complexity increases due to isolation requirements
Solution Approach 1:
The patent extracts and separately processes the self-interference component from the received signal. By isolating the transmit signal leakage mathematically through signal processing rather than physically through duplexers and isolation structures, the system achieves continuous transmission without complex isolation hardware, resolving the contradiction between productivity and device complexity.
Solution Approach 2:
The patent replaces mechanical/isolation-based frequency separation (physical duplexers, filters, and isolation structures) with a digital signal processing approach. The self-interference cancellation algorithm substitutes for the physical isolation mechanisms, enabling continuous transmission while reducing device complexity by eliminating or simplifying the isolation hardware.
3Manufacturing precision
If equalizer function is applied to received signal, then manufacturing precision of signal processing is improved, but device complexity increases
Solution Approach 1:
The patent applies equalization before self-interference cancellation in the signal processing chain. By pre-processing the received signal to compensate for channel effects before the cancellation operation, the system improves overall signal processing accuracy. This preliminary action simplifies subsequent processing steps and reduces the computational burden, resolving the contradiction between manufacturing precision and device complexity.
Data Source
AI summary
A cross-division duplex (XDD) system includes an apparatus having a transceiver configured to communicate via an uplink channel and a downlink channel concurrently. The apparatus also includes a transmit antenna, a receive antenna, and a processor. The processor is configured to: estimate a non-linear component corresponding to a transmit path in the transceiver; apply an equalizer function to a received signal; and subtract, in a self-interference cancel (SIC) circuitry, the estimated non-linear component from the equalized signal.