Digital Self-Interference Canceler for MIMO Transmitters
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Solution Overview
Problem
Modern cellular communication systems face challenges in uplink coverage due to limited output power of user equipment (UEs), which constrains the coverage range and requires more base stations, especially in Frequency Division Duplexing (FDD) systems where self-interference is significant, and there is a need for a low-complexity solution to alleviate self-interference in multi-antenna systems.
Innovation Solution
An equalizer-assisted self-interference canceler is implemented in a transceiver system with multiple transmit and receive antennas, using feedback signals to calculate a self-interference estimate and subtract it from received signals, thereby obtaining a residual signal, which improves signal-to-interference ratio and channel capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If FDD systems use separate bands for uplink and downlink with simultaneous operation, then uplink coverage is extended and continuous operation is achieved, but self-interference between transmit and receive paths increases significantly
Solution Approach 1:
The patent extracts and removes the self-interference component from the received signal by calculating an estimate of the self-interference based on feedback signals from transmit antennas, then subtracting this estimate from the received signal at receive antennas, thereby isolating the desired uplink signal from the harmful self-interference
Solution Approach 2:
The patent introduces an intermediary self-interference cancellation system that includes feedback signal paths from transmit antennas through equalizers to estimate self-interference, and a subtraction mechanism that removes this estimated interference from received signals, acting as a mediator between the transmit and receive paths
2Object-generated harmful factors
If traditional isolation methods using duplexers and separate antennas are used, then self-interference is reduced, but device complexity and isolation requirements increase
Solution Approach 1:
The patent replaces physical isolation mechanisms (duplexers and spatial separation) with a digital signal processing approach that uses feedback signals, equalizers, and mathematical subtraction to cancel self-interference, substituting mechanical/electrical isolation with computational methods
Solution Approach 2:
The patent changes the approach from physical parameter isolation (frequency separation, spatial distance) to signal parameter manipulation (feedback signal processing, equalization coefficients, interference estimation) to achieve self-interference cancellation
3Area of stationary object
If more base stations are deployed to improve uplink coverage, then coverage range is extended, but system cost and complexity increase
Solution Approach 1:
The patent enables the base station to serve itself by using its own transmitted signal feedback to estimate and cancel the self-interference it generates, allowing the system to overcome its own limitations without requiring additional infrastructure
Data Source
AI summary
An apparatus is configured to perform a method for self-interference cancelation (SIC). In one embodiment, an apparatus is provided. The apparatus includes a transceiver, a first number of transmit antennas, a second number of receive antennas, an equalizer, and SIC circuitry. The equalizer is configured to, for at least one receive antenna of the second number of receive antennas: receive feedback signals, wherein a feedback signal is received from each of the first number of transmit antennas; and calculate, based on the feedback signals and an equalizer function, a self-interference (SI) estimate for the at least one receive antenna. The SIC circuitry is configured to, for the at least one receive antenna of the second number of receive antennas, subtract the SI estimate from a signal received at the at least one of the second number of receive antennas to obtain a residual signal.