STI: Flexible Wireless Systems for Rapid Network Evolution

University Of Kansas Center For Research Inc, Lawrence KS

Investigators

Abstract

Ultra-wideband (UWB) systems portend to offer multiple communications advantages. However, the conventional approach to UWB systems is to emit a short, possibly shaped, pulse at determined intervals. The effect is not unlike your car engine firing a spark plug at determined intervals. Advocates contend that by shaping the pulse and adjusting the interval between pulses, a robust, short-ranged communications system can be achieved. However, traditional UWB systems have only two degrees of freedom, pulse shape and pulse interval. This limits their ability to avoid interfering with critical (e.g. GPS) channels and comply with laws regarding spectrum management. The project investigates solutions to these issues by developing, implementing, and demonstrating an ultra-wideband communications system based on hundreds to thousands of individual carrier channels. Called Hyper-Orthogonal Frequency Division Multiplexing, or HOFDM, such systems will allow the rapid deployment of new wireless Internet services by providing a platform that is flexible with respect to the ambient spectrum regulations and conditions. H-OFDM permits the mining of the existing spectrum to obtain bandwidth to support new networking services. The H-OFDM system has the following attributes: 1. The radio frequency (RF) environment can be sensed and the system can adapt to the local environment. 2. The H-OFDM system can adjust to local (foreign) regulations regarding RF emissions. 3. The H-OFDM system can adjust to propagation conditions, using lower frequencies to penetrate foliage and/or reach longer distances or use higher frequencies to limit range and support covert operations. Generation of a H-OFDM signal is the combination of hundreds of individual carriers at frequencies compatible with the requirements of the propagation environment, the degree of stealth, and the limitations of the applicable government. OFDM is selected because one can move carriers with relative ease, one can move carriers very close to existing channels, and one can easily control the modulation and bandwidth. The system proposal is based on three components: 1. Ultra-wideband radio frequency transmitters and receivers. 2. Ultra-wideband antennas, power amplifiers, and low-noise receivers to support the H OFDM system. 3. High-performance digital signal processing (DSP) algorithms and components to generate and detect H-OFDM signals. When successful, this project will provide a technology for providing wireless Internet services with greater bandwidth.