Spectrum Engineering

This report details a method that was developed to identify all potential forms of interference that could occur with a proposed collocation of three Federal systems in the 1675–1695 MHz frequency band. The incumbents are the National Oceanographic and Atmospheric Administration’s (NOAA) Geostationary Operational Environmental Satellites (GOES) and receivers and radiosonde systems. The entrant is the Department of Homeland Security’s (DHS) Video Surveillance System (VSS). The primary objective is that the quality of the mission-critical communications for each service is maintained.

A detailed electromagnetic compatibility (EMC) analysis is used to identify both the highest potential interference scenarios and those scenarios that have little to no effect. Two primary interference mitigation techniques can be implemented to achieve electromagnetic compatibility: frequency offset (Δf) and separation distance. Based on the frequency dependent rejection (FDR) between the interference source and the victim receiver, the Δf and separation distance necessary for a desired level of interference rejection can be calculated. For all potential interference interactions, the Δf and the separation distance can be adjusted to arrive at a solution for operation on a non-interference basis. It is not the intent of this report to make pronouncements on how to achieve coexistence within a shared band. The intent is to examine and illuminate the engineering questions that need to be answered so that those who are responsible for Federal services in a band may negotiate and cooperate with their colleagues who are responsible for other Federal services in the same band.

Keywords: electromagnetic compatibility (EMC); spectrum sharing; interference mitigation; frequency dependent rejection; frequency offset; separation distance

• TR-15-516 

This report describes a comprehensive series of tests that were conducted by engineers and researchers from the U.S. Department of Commerce’s Public Safety Communications Research (PSCR) program and the University of Colorado during the period of July 2013–May 2014. The report presents results obtained at two buildings located on the campus of the University of Colorado at Boulder. Indoor coverage was measured using the PSCR Band 14 LTE outdoor macro network. We also explored methods for improving in-building coverage using a cell on wheels and small cell feeding either discrete antennas or a distributed antenna system. The results indicate that the PSCR macro network by itself does not provide complete coverage inside these buildings and that coverage needs to be supplemented with combinations of a small cell deployed indoors and a cell on wheels (COW). The results indicate that significant system in-building performance improvements can be realized using small cells and a COW.

Keywords: modem; antenna; building attenuation; indoor propagation; signal strength; spectrum analyzer; Long Term Evolution (LTE); small cells; test methodology; backpack measurement system; macro network; Band 14; cell on wheels; channel analyzer; in-building

• TR-15-518

Great emphasis is seen on the networking and data management aspects of spectrum monitoring, but far less attention is given to the radio frequency (RF) sensor systems used to collect the spectrum data. This report focuses on these sensor systems and, in particular, the commercial-off-the-shelf (COTS) RF sensors used in the sensor systems. A test plan for evaluating the RF performance of COTS sensors is outlined. Evaluation of COTS sensors is an ongoing task of the Center for Advanced Communications (CAC) Spectrum Monitoring Program. The intent is to build a comprehensive cost/capability/performance matrix to help guide the selection of the appropriate COTS sensor for a given monitoring scenario. The test plan strives to standardize the tests and metrics, so that results can be compared from sensor to sensor.

Keywords: software defined radio; spectrum monitoring; RF sensor

• TR-15-519