WiFi Backscatter Range Extension via Query Signal Nulling
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Solution Overview
Problem
WiFi backscatter communication systems have limited range due to self-interference issues, particularly in non-line-of-sight scenarios, as existing WiFi devices lack full-duplex radios, leading to weak backscatter signals that are difficult to decode, and out-of-channel systems face interference and power consumption challenges.
Innovation Solution
The method involves nulling the query signal at the WiFi receiver using multiple signal components with adjusted phases and amplitudes to eliminate self-interference, allowing for effective decoding of backscatter signals at greater distances and in NLOS conditions without modifying existing hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If in-channel WiFi backscatter systems are used, then the query signal and backscatter signal are in the same channel, but the backscatter signal becomes orders of magnitude weaker than the query signal resulting in self-interference and very limited range
Solution Approach 1:
The patent segments the communication process into distinct phases: a query phase where the WiFi transmitter sends signals, and a backscatter phase where the tag modulates and reflects signals. This temporal segmentation allows the receiver to separately process query signals and backscatter signals, reducing self-interference and improving decoding reliability while maintaining compatibility with existing WiFi devices.
Solution Approach 2:
The system employs periodic transmission of query signals followed by periodic backscatter responses. This periodic structure enables the receiver to anticipate and filter out query signal interference during backscatter reception, improving signal decoding reliability while working within the constraints of existing WiFi device architecture.
2Reliability
If out-of-channel WiFi backscatter systems are used, then the backscatter signal is shifted to another channel to avoid self-interference, but this creates interference for other WiFi traffic on the second channel and significantly increases power consumption
Solution Approach 1:
The patent changes signal parameters (frequency, phase, amplitude) of the backscatter signal to distinguish it from the query signal within the same WiFi channel. By modulating the backscatter signal with different parameters, the system achieves reliable decoding without shifting to another channel, thus avoiding interference with other WiFi traffic and reducing power consumption compared to out-of-channel systems.
3Length of moving object
If the distance between the receiver and the backscatter tag increases, then the backscatter tag's signal becomes orders of magnitude weaker than the originally transmitted query signal, but it becomes challenging for the receiver to separate and decode the weaker backscatter tag signal
Solution Approach 1:
The system implements feedback mechanisms where the receiver measures the strength and characteristics of received backscatter signals and adjusts its processing accordingly. This feedback enables the receiver to compensate for signal attenuation over distance, maintaining decoding accuracy even as communication range increases, by adapting filtering and detection parameters based on received signal quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly extends the WiFi backscatter signal range, enabling successful decoding of backscatter signals even when the tag is far away or out of line of sight, with improved Signal to Noise and Interference Ratio (SNIR), and can be implemented on current WiFi devices without hardware modifications.
Implementation Method 1
In response to receiving the query signal, a backscatter tag sends its own data (such as in the form of a backscatter tag or backscatter tag signal) by modulating and reflecting the query signal back to a WiFi receiver
Data Source
AI summary
In this disclosure, a system and method for extending WiFi backscatter signal range is disclosed. By nulling a query signal at the receiver end, the receiver is able to more effectively receive a backscatter tag signal that has been generated in response to the query signal.