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13.12.2017 : 4:31

Highlights: Proof of Concept

During the first months of work, WP7 has been focused on the definition and description of the Platform Architecture, which first steps can be found in D7.1. 

At a later stage in the QoSMOS Project, the definitive set of Proof of Concepts was defined and approved, and thus the four definitive test beds were presented in  D7.2, delivered by the end of the second year of the project.

The final scenario includes a complete group of QoSMOS entities which represent a reliable sample of the system architecture and it is extensively depicted in undefinedD7.5.

QoSMOS Proof of Concepts

The QoSMOS Proof of Concepts are the way to demonstrate, assess and validate certain Cognitive Radio functionalities previously selected, as well as a set of diverse building blocks developed within the different previous work packages.

In order to properly execute these tests a complete set of hardware and software tools is required, where the following resources can be found:

  • Multiple baseband signal generator and RF Up-converters
  • VMware to implement virtual machines
  • Real-time sensing and PHY integration
  • Ettus USRP platforms
  • TeleVision White Spaces Database

PoC #1 Primary scene and sensing engine

Primary scene and sensing engine proof of concept demo aims at showcasing the radio environment modelled in WP3, with the primary radio scene engine feeding the sensors developed within that work package in order to test their accuracy in both time and frequency dimensions.

The radio environment emulated by the primary radio scene engine consists of Incumbent User waveforms modelled over wide frequency band. The channel fading effects are also added on the waveforms before the faded signals are finally delivered to the sensors. The channel emulation also involves the Doppler spread effect in order to evaluate the performance of the sensing engine in a mobile environment.

 

The PoC#1 test bed is composed of three main entities: Primary Scene Emulator (PSE), sensor and spectrum analysis.

Primary Scene Emulator

The scene emulator concept is an advanced test platform for the evaluation of wireless systems that enables the reproduction of radio environment in laboratory conditions. The advantage over testing in the field is the full controllability and reproducibility of real-world test scenarios.

This platform is especially well suited for the testing of cognitive radio sensing devices, since it offers the capability to generate standards compliant waveforms and features also channel emulation block.

Sensors

The sensing node is built on top of the GNU Radio and USRP (Universal Software Radio Peripheral) hardware. The USRP devices used in the current test bed are composed of Ettus USRP1 and B100 motherboards and SBX, WBX and TVRX2 daughterboards that are responsible, respectively, for baseband and radio frequency processing. Other USRP devices can be easily adopted using the Universal Hardware Driver recently present in GNU Radio releases. The sensing node is in charge of performing the RF sensing and applying a local decision algorithm, as well as sending the final decision to the fusion unit, and its architecture is shown in the figure.

 

PoC #2 Flexible Transceiver

This PoC implements an original PHY layer adapted to Cognitive Radio requirements, thus providing quite relevant information about complexity, and being the QoS monitoring its key feature.

 

PoC#2 proposes to demonstrate some of the Flexible Transceiver aspects developed in QoSMOS. One element of demonstration that has been considered proposes to demonstrate the usage of TVWS as an application of the algorithms and design developed in WP4, notably the implementation of a Filter Bank Multicarrier Transceiver (FBMC). This PoC focuses on measuring the out-of-band performance of FBMC in a complete radio system, where RF impairments are accounted for. This is performed without compromising the flexibility of the transceiver, notably its frequency agility. One element that has been considered is to measure performance of the newly developed FBMC and the interference it may generate to incumbent users and may be compared against results simulated in WP4. A comparison with OFDM (Orthogonal Frequency Division Multiplexing) performance is also performed. PoC#2 serves as a basis for PoC#4 to demonstrate the complete integrated scenario.

The PoC is based on the QoSMOS T-Flex board developed in WP7 and already presented in [D7.3]. The digital board is interfaced to the RF TX and RX daughterboards in order to generate UHF (Ultra High Frequency) signal from 470MHz up to 860MHz in a flexible way. The ARM processor controls the digital board and the RF Boards and interfaces to an external PC via either a USB, an Ethernet or a Wi-Fi connection.

 

The setup proposed to demonstrate the capability of FBMC in terms of both transmitter flexibility and performance includes a QoSMOS T-Flex transmitter generating FBMC signal, while the transceiver is controlled by a Personal Computer. At the same time a DVB-T modulator is used to transmit a television service. DVB-T and FBMC transmitted signals are combined then divided to a Digital TV (DTV) receiver and a spectrum analyzer.

PoC #3 Distributed/Collaborative sensing

This PoC aims at demonstrating the benefit of the distributed sensing algorithms proposed and developed within WP3 through a sensing scenario which includes hardware sensors (Opportunistic Users) and a data fusion unit (Opportunistic User Base Station or Access Point), along with an Incumbent User signal generator.

 

Building on the work developed in WP3, where novel collaborative/distributed sensing algorithms were investigated and evaluated via computer simulations, the aim of this demonstration is to prove the worthiness of the developed algorithms in scenarios as close to reality as possible.

The hardware sensor is in charge of performing an RF sensing and applying a local decision algorithm, as well as sending the final decision to the fusion unit. The data fusion unit is responsible for the generation of the decision on the presence of an Incumbent User. This unit gathers the sensing data from the sensing devices and generates the final decision. Finally, the Primary Scene Emulator generates the IU signal that each sensing device receives according to the IU service detected and the considered channel model.

PoC #4 Integrated Proof of Concept

This integrated platform is designed to perform the validation of certain Cognitive Radio (CR) concepts developed for link and upper layers such as the spectrum management, the decision making algorithms and the Adaptation Layer functionalities

The proposed use case, composed of different entities, coming from the developments carried out within the rest of work packages, implies a sequence of interactions taking place between the QoSMOS system and some of its actors, involving a TVWS environment, where a cellular legacy system and a TVWS opportunistic system are combined through a complete group of QoSMOS entities selected to represent a reliable sample of the system architecture.

 

Thus, a Primary Scene Emulator (PSE) is used to generate opportunistic user signals. A spectrum portfolio repository is emulated in the so called Master Entity (ME) to provide access to the databases. This ME is the centralising point in the scenario, presenting features of the Adaptation Layer and of some other QoSMOS architecture entities not fully developed for this test bed.

A cellular network is deployed in order to work within two different environments. Cell 1 uses the flexible transceiver, operating in a TVWS band, while cell 2, in form of a femtocell, operates in a licensed band (3G).

In addition, a User Equipment (UE) with cognitive features is present, composed of a Smartphone and an additional feature for white space operation, provided by the flexible transceiver.

Finally, a mesh of sensors is present in order to carry out distributed sensing duties and get a proper frequency to work with based upon the results offered by the data fusion unit (DFU).

 

Depiction of the scenario

The user equipment, represented by an Android cell phone, is going to play a video sent from a RTSP (Real Time Streaming Protocol) server (based on TCP for control duties and on UDP for data) through different TV channels and, after an eviction process is executed, a 3G connection.

The Opportunistic transmission that will be carried out begins using TV Channel 1. After a while, an Incumbent User is going to appear in that same TV channel, thus making it necessary to change to another one to continue the video streaming. The sensors inform that TV Channel 2 is not in use, so the transmission can be changed to that channel. Moments later, another Opportunistic User is going to make use of that same TV Channel 2, thus producing QoS decline which pushes the system to switch to a legacy channel in order to continue, and successfully end, the video streaming transmission.