Analog Cancellation for Full Duplex MIMO Radio Interference
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Solution Overview
Problem
Current wireless communication systems, particularly those using division free duplexing in MIMO radio systems, face challenges in isolating transmitter power from co-located receivers due to broadband noise and non-linearities, leading to interference and reduced capacity.
Innovation Solution
The system employs a circulator and multitap cancellation components to sample and modify the analog transmitted signal, generating a cancellation signal that reduces the amount of transmitted signal appearing at the receiver, thereby mitigating interference and increasing link capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency division duplex or time division duplex is used to avoid interference, then interference between transmitted and received signals is reduced, but transmission capacity and link utilization are limited
Solution Approach 1:
The system applies preliminary anti-action by generating a cancellation signal that is the inverse of the leaked transmit signal before it interferes with the received signal. The cancellation signal is created by sampling the transmit signal, processing it through complex conjugation and channel estimation, and then subtracting it from the received signal path, thereby preemptively neutralizing the interference
Solution Approach 2:
The patent introduces an intermediary cancellation signal path that mediates between the transmit and receive paths. This intermediary path samples the transmit signal, processes it through channel estimation and complex conjugation, and injects the processed cancellation signal into the receive path to counteract the direct leakage, thus enabling full duplex operation
2Reliability
If transmitter power is increased to improve signal strength, then received signal quality improves, but transmitter noise and signal leakage into the receiver increases
Solution Approach 1:
The system converts the harmful leaked transmit signal into a beneficial cancellation signal. By sampling the transmit signal and processing it through channel estimation and complex conjugation, the system transforms the harmful leakage into a useful cancellation component that, when subtracted from the received signal, actually improves receive sensitivity and signal quality
Solution Approach 2:
The patent implements feedback by continuously sampling the transmit signal and using it to generate real-time cancellation signals. The channel estimation process provides feedback about the leakage path characteristics, which is then used to adjust the cancellation signal parameters, creating a closed-loop system that adaptively compensates for transmitter noise and leakage
3Productivity
If multiple transmitters are used in MIMO to increase link capacity, then data throughput increases, but signal leakage into each receiver increases
Solution Approach 1:
The system applies segmentation by treating each transmitter-receiver pair in the MIMO system independently with dedicated cancellation paths. Each transmitter's leaked signal is sampled and cancelled separately in each receiver, allowing the system to scale to multiple antennas while maintaining effective interference cancellation for each spatial stream
Solution Approach 2:
The cancellation mechanism is designed with universality to handle multiple transmitters and receivers simultaneously. The same cancellation principle (sampling, channel estimation, complex conjugation, and subtraction) is applied universally across all MIMO antenna pairs, enabling the system to maintain full duplex capability across the entire MIMO array
Data Source
AI summary
System and method embodiments are provided for analog cancellation for division free duplexing for radios using MIMO. In an embodiment, a system for minimizing transmitted signals from a transmitter appearing at a co-located receiver in a division free duplexing radio includes a transmitter to transmit an analog transmitted signal; an antenna; a circulator coupled to the transmitter and the antenna; a tuning algorithm component configured to receive a copy of the analog transmitted signal from the transmitter and a sampled analog received signal from a received signal path from the circulator, wherein the sampled analog received signal is sampled at a point in the received signal path before the analog received signal is provided to a receiver; and a multitap cancellation component configured to provide a cancellation signal to couple to the analog received signal such that an amount of the analog transmitted signal appearing at the receiver is reduced.