A high bandwidth radar operation over the Internet: signal analysis, network protocols and experimental validation

Abstract

The Virtual-CHILL (VCHILL) project is an initiative to provide full operation of the CSU-CHILL radar over the Internet. As part of this project, VCHILL aims to transmit Digitized Radar Signal (DRS) in real-time over high-bandwidth data network, estimate radar parameters at remote sites, and distribute them for display and further applications. This concept is referred to as the high-bandwidth VCHILL. The distribution of real-time DRS enables the remote users to process the digitized signals according to their interests. First, a new digital-IF receiver, which operates in parallel with the existing digital receiver (DRX) of the CSU-CHILL radar, was developed. The parallel receiver operates in conjunction with the DRS network server so that the server arranges the DRS into a specified format in real-time and transmits it to clients at up to a few hundred Mbps. Subsequently, end-system architectures for the high-bandwidth VCHILL were developed. The architecture design includes various functions, such as DRS acquisition, DRS transmission, DRS receive/radar parameter computation, and parameter transmission, as well as generic packet and data structures for the data transmission and sharing. Third, transmission waveform design scheme for congestion control was developed to make the real-time operation tolerable and provide high quality end products under unpredictable network conditions. The developed scheme relies on the operating principle of the pulsed-Doppler radar and estimation theory of the radar parameters. A combination of this waveform design scheme and a source-based rate control algorithm with Additive Increase and Proportionate Decrease based on the feedback provides the highest quality of service possible. Performance evaluation of the system, while operating the CSU-CHILL radar in real-time, shows the linearity of the end-to-end TCP throughput proportional to the data, rate, coincidence with the output of the DRX system, quality improvement of display, as well as apparent congestion control functionality. Finally, to increase computing capacity at client sites, a concept of distributed DRS client was developed. The essential idea is that the computation loads are evenly distributed among the computing nodes that are connected to each other in networked environment. Another aspect of the VCHILL is networked radar operation. In this scenario, a networked radar system can be readily used for the simultaneous observation of a same target by multiple radars, and the replacement of a large centralized radar with multiple small radars. Operational models, end-system architectures, and network models to make possible the notion of the networked real-time weather radar system are proposed. Scalability of the networked radar system was studied in terms of power consumption for pulse transmission, computation load, and communication load varying the Quality of Service parameters of spatial resolution and data accuracy.