Every day the number of devices connected to wireless internet creeps closer to the 1 billion mark. The radio spectrum currently available for wireless internet is getting strained, access points and base stations are becoming overloaded and prices for consumers are rising. The new Microsoft Spectrum Observatory in Brussels shows that this does not have to be the case.
Microsoft has been exploring how to improve the utilization of available spectrum for a decade or so. We’ve looked at devices that opportunistically access unused spectrum, for example, TV White Spaces technology that work without disrupting TV broadcasts. We’ve also found ways to measure how the allocated spectrum is being used (or not). Our Spectrum Observatory represents an important breakthrough in this regard.
The Spectrum Observatory has been developed to give regulators and policy makers access to the latest information on the usage of wireless spectrum. Most policy makers agree that the way spectrum has been allocated lies at the heart of the current spectrum shortage but before making any significant changes to the underlying legislation they need information on how, when and which spectrum is being used. The Spectrum Observatory provides a one-stop solution for spectrum usage data. It helps collect and analyse the data, and helps inform decisions on which spectrum bands are the most appropriate immediate targets for expanded spectrum sharing. Microsoft’s first two installations, at our headquarters in Redmond and in Washington, D.C., have both been put to good use over the past few months.
The decision to launch the next Spectrum Observatory in Brussels was easy to make. Regulators around Europe have become increasingly interested in dynamic spectrum access. In the autumn of 2012 the European Commission put out a Communication on promoting the shared use of radio spectrum and there has been strong interest from regulators in Ireland, UK and Finland in trials and commercial pilots of the TV White Spaces technology.
Collecting and visualizing the data
The Spectrum Observatory draws on data collected via monitoring stations, which rely on a RFeye device manufactured by our UK-based partner CRFS. The device completes a scan of transmitted signals across a frequency range of 30 MHz to 6 GHz (a range typically used for television broadcasting, cordless phones, walkie-talkies, satellite communication, and numerous other applications) every three seconds, measuring the power of the signals. Once the raw readings for power spectral density are collected, they are stored and processed for visualization through the Microsoft Azure Cloud platform and made available for interactive viewing.
The system currently supports three different visualizations of the data: a spectrogram, occupancy chart, and power density chart. The spectrogram is a time-versus-frequency waterfall plot, which shows how the measured values change over time. The other two plots, occupancy and power density, provide views of the data aggregated over different time periods, including an estimate of the percentage of time that a particular frequency band is being used and the signal strength.
The chart above represents an example of the information the Spectrum Observatory can provide. It looks at last week’s usage of the ultra-high frequency (UHF) band between 400 MHz and 1 GHz in Brussels and demonstrates that not all parts of the spectrum are occupied at any one time. However, this is just a small example of the functionality available.