Vortex Radiometer for Wireless Communications
Vortex Radiometer for Wireless Communications (LEW-TOPS-147)
Mitigating Fades and Maximizing Throughput
Innovators at the NASA Glenn Research Center have developed the Vortex Radiometer (VR), an early-warning system for communication antennas that identifies atmospheric noise before it reaches the antenna and then optimizes mitigation strategies. Communication links are subject to atmospheric effects that reduce the signal power received at the antenna (i.e., a fade). If the atmospheric losses are too high, the signal level could drop below the minimum measurable power of the receiver, causing data loss across the communication link. Previous attempts to forewarn fading using predictive algorithms have yielded sub-optimal results largely because they rely on real-time performance data from the communications link itself, meaning they have very little time to respond. By contrast, NASA's VR constantly senses incoming noise, which allows real-time measurement and characterization of fading and enables maximization of data throughput.
The Vortex Radiometer (VR) creates concentric, annular antenna beam patterns that measure sky-noise temperature. Annular antenna patterns are created by imparting orbital angular momentum into the electric field received by the antenna using spiral phase plates placed in front of the antenna aperture, generating multiple radiometer channels. Data points are then collected by plotting the measured noise temperature of each radiometer channel as a function of time. Noise temperature increases as a noise source (e.g., weather-related noise, signal interference, etc.) traverses the antenna beam patterns. An algorithm is then used to correlate noise temperature peaks in adjacent beams and to determine when a fade will occur, how long the fade will last, and how intense the fade will be. With this information, effective and efficient strategies can be implemented using cognitive communication and antenna systems to autonomously select the optimum fade-mitigation technique and parameter (e.g., increasing the transmission power, adjusting the modulation and/or coding scheme, etc.). NASA's VR system has been prototyped, including the radiometer device and the algorithm for characterizing noise sources based on VR data. Simulations have shown that a VR system can instruct an existing cognitive antenna to switch between Ka- and X-Band communications in order to avert interference from small diameter noise sources. Any high-performance communication systems operating in RF or optical frequencies may benefit from NASA's VR capabilities.
- Data-based measurement of incoming fades: The VR uses measured data and a prediction algorithm to estimate when a fade will occur, how long it will last, and how intense it will be
- Accurate cognitive communication and antenna systems: The VR can provide accurate data to autonomous fade-mitigation antennas
- Adaptable platform: The VR system can be implemented into existing communication systems in current form or with minor modification
- Aerospace and Aviation: ground communications
- Antennas: incorporation of VR into antenna packages
- Financial communications: point-to-point millimeter-wave communication systems for financial services
- Military: high-performance defense communications
- Marine: ship-to-ship and ship-to-shore communications
- Satellites: telemetry, satellite television, and satellite internet
- Unmanned Vehicles: UAV and drone data transmission