Randall Olsen

Directional ad hoc networking technology (DANTE) performance at sea

SPAWAR Systems Center Pacific has spent several years developing directional wireless networks. These networks harness the power of highly directive antennas (range extension, higher data rates, lower power consumption, etc.) and have software to deal with the additional beam-steering complexity. The directional networking technology, DANTE, is outlined first. Three Trident Warrior at-sea tests of DANTE are then described, with summaries of each of their successes and limitations. Finally, we briefly relate ongoing DANTE-2 research efforts on the antennas and networking software.

New approaches to directional antenna technologies for unmanned system communications

We discuss novel methods and techniques for the design and development of low cost light weight directional antennas at microwave frequencies for unmanned system communications application. These are based on Rotman lens, Risley prism and the multi-horn switched beam antenna principles.

Network solutions for employing COTS radios in multi-sector directional architectures

Central to this paper is the use of electronically-steered directional antennas with COTS radio technology to increase performance. In this paper, we describe a multi-sector wireless architecture using several such radios/antennas in a complete system. We discuss networking issues and solutions that arise due to this architecture including link discovery, signal tracking, handover, and the coordination of these between nodes. We also introduce the concept of using a ldquogateway aliasrdquo which provides transparent routing by allowing multiple radios to appear as a single node. The system has been implemented using high gain, switched-beam directional antennas and tested in an operational environment. Results and future direction are discussed.

Real-world rotman lens prototyping and analysis

In this paper, tools to semi-automate and speed up the Rotman lens design process are suggested, allowing researchers to rapidly iterate designs or produce studies that span multiple design parameters. As guidance for the analysis of these lenses, methods for measuring or simulating insertion loss and beam efficiency of the entire lens are described. These are real-world characteristics that must be assessed and optimized if Rotman lenses are to contend with other phase-shifting devices for military or commercial use.

A solution to network protocol issues for directional ad-hoc networks through topology control and a multiple-radio-per-node architecture

Line of Sight (LOS) communications and mobile networking are important capabilities for future military operations. Central to this idea is the desire for increased bandwidth and the ability to operate in the absence of satellite-based communications. A key concept in tactical edge wireless networks and airborne backhaul networks is the use of directional antennas to boost the performance of radio systems. As most current radio and wireless networking protocols were designed for omni-directional and/or fixed infrastructure environments, the use of directional antennas introduces disrupting side effects in many protocol layers of a networking system. Solving these issues is the topic of much current academic research. In this paper we describe a Multiple-Radio-per-node Architecture (MRA) that eliminates most of these problems. That is, our solution involves making changes to the architecture of a wireless node as an alternative to making changes to the design of network protocol layers. As a result, our architecture makes it possible to immediately build fully directional mobile ad-hoc networks (MANETs) using a wide range of radios without requiring major modification to the radio or existing protocols. Instead, the focus is on building a system of controllers that understand the capabilities of a given radio and implement appropriate discovery, tracking, and topology control algorithms.

Physical simulation of long distance and directional wireless channels

In order to accurately test directional or multiplexed systems in a lab environment, a testbed should simulate both directional wireless channels and propagation delay. Using one or more RF lenses, one can test a radio system that uses switched or adaptively steerable antennas: one side is switched by an ldquoenvironmentrdquo controller, the other by the the discovery and tracking loop of the radio system. True path delay testing can be done by using analog RF-to-optical converters and miles of low-cost, low-loss fiber optics. Apart from verifying latency, this test can also determine if there are issues with ACK or other timeouts: information unavailable by simply attenuating a link to simulate distance.

Semi-automated Rotman lens design focusing on anti-jam performance

We have made a case for semi-automation of RF lens design and described some of the important performance characteristics required of RF lenses to perform well in jamming environments. The semi-automation tools developed by the authors were outlined and shown to not only speed up development time, but also bring to light important realities of Rotman lens performance. Many design iterations with full wave MoM simulation are needed to ensure that the lenses yield acceptable anti-jam characteristics (i.e., low sidelobes). Much research and development work remains to fully understand and control the complex interactions of the many lens design parameters including horn and anechoic section size/shape/position.