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retrieve environmental and location data from peripheral
components, process data, and package metadata/data.
In particular, although any kind of device able to capture
and analyze a frequency interval could, in principle, be compliant with the standard, we imagine three different possible
architectures: (1) an autonomous Software Defined Radio,
(2) a host-based Software Defined Radio (as considered in
this paper) or (3) a bench instrument such as a Spectrum
Analyzer.
In the first case, all conditioning, acquisition, processing
and decision operations are performed on board, and it is also
capable of packing the retrieved data and needed metadata to
send them back to manager.
In the second case, with respect to Fig. 2, it is possible to say
that only the conditioning (pre-selector) and acquisition are
made on-board, while processing as well as data packaging
and communication are performed by leveraging on the connected computer capabilities.
Finally, a bench instrument is a possible sensing solution,
where all " measurement " tasks are performed on-board, but
generally it needs to be remotely driven to send data or perform particular post-processing task, as data packaging: this
latter is usually left to a computer, still following the scheme
reported in Fig. 2.
The Sensor software provides a platform for operating
Sensors over a data network. The goal is to provide a robust,
flexible, and secure starting point for remote and distributed
spectrum monitoring. The Sensor software is required to: provide status, advertise capabilities, provide onboard scheduler,
be responsive to tasking, and package task results in a common metadata/data format. To support standard messaging
protocols such as HTTPS and MQTT, the standard defines the
Sensor control service and objects associated with the following endpoints: Status, Capabilities, Schedule and Task.
The standard is intended to support Sensor hardware- and
algorithm-agnostic developments. This is achieved via capture of Sensor hardware metadata and software metadata with
each sensing task. The metadata is associated with the dataset
created by the sensing task and together are transmitted back
to the Manager and/or the SCOS Client as a packaged data
object. Depending on the deployment model and use case,
Sensors can be calibrated at install time, or periodically via a
calibration signal source, with a digital calibration certificate
that is available for inspection via the Manager and included
in the metadata for any task.
The intent is to enable a variety of SCOS data clients to programmatically consume required information and promote
collaborative research, large-scale analytics, and sharing of sophisticated tools and methodologies.

The Manager
The Manager is a software system that allows Clients (whether
individual users or other systems) to interact with a distributed network of Sensors. The Manager does not engage
in sensing activity itself but exposes the capabilities of the
SCOS platform to users, manages task requests by users, and
December 2020	

ultimately controls the sensors registered with it. There are no
normative hardware requirements associated with the Manager-it is a software-only component in the architecture.
Manager software requirements include:
Operations: Display sensor locations, status, and other system
diagnostics in an operations view to allow for early detection
of problems.
Client Requests: With appropriate permissions, Clients can
download acquisitions already acquired or specify a transmission end-point for acquisition datasets. Based on SCOS
platform capabilities and authorization, Clients can also request new actions to be scheduled by the Manager to the
appropriate Sensor.
Distributed sensing actions: Schedule and manage actions
across groups of sensors.
SCOS Owner control: Clients can request new actions to be
scheduled, but only as far not scheduled without as they are
authorized by the SCOS Owner, provided through authorization or policy mechanisms implemented on the Manager.

Preliminary SCOS Testbed Implementations
The described idea has been implemented to provide a test-
bed where the SCOS functionalities have been effectively
tested and validated. The instruments used, reported as Sensors in the standard draft and working as Sensing Devices, are
a National Instrument (NI) product, NI 2901[9]. The Manager
is implemented on a notebook computer, and it, along with
the Sensors, is connected to a Local Area Network (LAN). The
adopted sensors can scan frequency bands ranging from 70
MHz to 6 GHz, with a maximum instantaneous bandwidth of
56 MHz. They are endowed with two RF chains, namely RF0
and RF1. The Manager is provided with this information at
Sensor association time. The Manager stores the information
locally and links RF capabilities to a unique Sensor identifier.
Due to the chosen devices' entry-level nature, the RX channels
are endowed with only one oscillator, and consequently, the
RX settings are jointly set. TX channels have the same working condition. In Fig. 3, the block diagram of the adopted
sensing device is displayed, as provided by the instrument
manufacturer.
The working principle of the system is completely derived
from the standard description and its deployment is not geographically distributed but is confined to the laboratory in
order to test functionalities. In the following discussion, we
provide some insight about the developed sensing technique
and its results in terms of the Receiver Operating Characteristic (ROC) curve.
The lab work has been focused on the detection of users within the VHF and UHF bands. Typical signals are DTT
(DVB-T in Europe) and Program Making and Special Events
(PMSE), such as wireless microphones. Details about sensing
techniques can be found in [10].

IEEE Instrumentation & Measurement Magazine	61



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