Phase-Net

Advanced Research provided test expertise to Venture Ad Astra on the Phase-Net program.

About Phase-Net

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Phase-Net, a product of Venture Ad Astra, provides precise position and time over long distances through a software-based architecture. It is capable of taking advantage of signals of opportunity, reduces its impact on the radio spectrum and allows wireless devices and communication units to have location awareness. This is accomplished by the use of accurate time stamping and sophisticated algorithms that build on GPS and Network theory. Phase-Net also employs the powerful benefits of network gain to obtain greater precision availability and reliability.

Phase-Net presents an immediate advantage to other radionavigation positioning methods. By using signals of opportunity, instead of implementing a separate constellation of dedicated positioning beacons, a system with position and timing accuracies better than GPS can be established more quickly and at much lower cost.

Technically, Phase-Net works by sharing simple time stamps at each signal source and signal receiver. These time stamps are processed from multiple sources over multiple times to compute precise relative time and position. When integrated with a precise absolute reference, the precise time and position information is available at any node in the network. The multiplicity of nodes and their interaction in the network provide an inherent gain in precision, resulting in relative timing accuracies on the order of 100 picoseconds or better, a near 100-fold improvement over absolute GPS. Phase-Net can be adapted to any wireless network that broadcasts data, — such as a digital communication channel or telemetry stream, — providing enhanced flexibility and scalability. Each node becomes both a reference provider and user. Thus a key to successful operation is to employ enough nodes to permit robust operation of Phase-Net in the event nodes drop in and out. While Phase-Net assumes that good quality crystal clocks are used at individual nodes, this alone is not enough to obtain the accuracies capable from Phase-Net. A further gain is obtained from Phase-Net processing that yields an order of magnitude increase in accuracy, taking it to the sub-nanosecond range of accuracy. This translates into position accuracy on the order of centimeters. The system is also accommodating to passive only nodes which can calculate positions from transmitting nodes without itself transmitting. It also has the capability to function with intermittent transmissions or signal drop outs.

Phase-Net has been in development by Venture Ad Astra (VAA) for several years, and has completed two years of development funded by the US Air Force for government and civil applications. The first year of development demonstrated Phase-Net’s feasibility in a simulated environment using AGI’s Satellite Tool Kit and MATLAB. The second year of development has been demonstrating its operation forensically using live radios with post-processing of the

timestamp data. Recently VAA established a commercial subsidiary for Phase-Net, known as ZuluTime LLC, which has begun a commercial application in cellular, Wi-Fi, and WiMAX technology.

The Test Program

Advanced Research developed a full scale test program to both verify and validate system and specification requirements, as well as system operation in a variety of conditions, in accordance with US Air Force requirements.  Our test plans identified the test objectives and qualification requirements, test environment, and the various test cases necessary.  We then developed detailed procedures describing the steps to be followed in conducting the tests.  We coordinated with the client in developing a precision test environment, in which the positions of each of the Phase-Net units was measured to sub-centimeter precision.

Changes in the project’s goals and specifications have demanded changes to the original test program. Large portions have been executed as planned while others have been modified or dropped according to the wishes of the client.

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