Testbed

Office Testbed

NITOS facility

 The main experimental components of NITOS are:

• A wireless experimentation testbed, which consists of 100 powerful nodes (some of them mobile), that feature multiple wireless interfaces and allow for experimentation with heterogeneous (Wi-Fi, WiMAX, LTE, Bluetooth) wireless technologies.
• A Cloud infrastructure, which consists of 7 HP blade servers and 2 rack-mounted ones providing 272 CPU cores, 800 Gb of Ram and 22TB of storage capacity, in total. The network connectivity is established via the usage of an HP 5400 series modular Openflow switch, which provides 10Gb Ethernet connectivity amongst the cluster’s modules and 1Gb amongst the cluster and GEANT.
• A wireless sensor network testbed, consisting of a controllable testbed deployed in UTH’s offices, a city-scale sensor network deployed in Volos city and a city-scale mobile sensing infrastructure that relies on bicycles of volunteer users. All sensor platforms are custom, developed by UTH, supporting Arduino firmware and exploit several wireless technologies for communication (ZigBee, Wi-Fi, LTE, Bluetooth, IR).
• A Software Defined Radio (SDR) testbed that consists of Universal Software Radio Peripheral (USRP) devices attached to the NITOS wireless nodes. USRPs allow the researcher to program a number of physical layer features (e.g. modulation), thereby enabling dedicated PHY layer or cross-layer research.
• A Software Defined Networking (SDN) testbed that consists of multiple OpenFlow technology enabled switches, connected to the NITOS nodes, thus enabling experimentation with switching and routing networking protocols. Experimentation using the OpenFlow technology can be combined with the wireless networking one, hence enabling the construction of more heterogeneous experimental scenarios.

The testbed is based on open-source software that allows the design and implementation of new algorithms, enabling new functionalities on the existing hardware. The control and management of the testbed is done using the cOntrol and Management Framework (OMF) open-source software. NITOS supports evaluation of protocols and applications under real world settings and is also designed to achieve reproducibility of experimentation.

Use NITOS

LoRa city-scale Testbed

Testbed Topology

The LoRa testbed consists of one LoRa Gateway (GW ) that is deployed on the rooftop of our University’s premises and ten Sensing nodes that are scattered across the city of Volos, Greece. The end nodes feature various air quality probes, characterizing gas concentrations, dust particle con- centration, along with outdoor air temperature and humidity modules. We clearly observe that the testbed offers a wide range of wireless links that differentiate in terms of communication distance, elevation difference and LOS/NLOS conditions. For each node, we also note the amount of payload bytes transmitted when transferring the respective number of sensed parameters, which includes 5 Bytes per environ- mental parameter plus 9 Bytes of own protocol overhead, while it does not include the LoRa preamble, header and CRC, as specified in [5]. Below we present the custom developed GW and sensing devices, as well as the software toolkit for obtaining LoRa performance measurements.

LoRa Gateway: The GW is based on the BeagleBone Black Rev. C board [18] which is a low-cost, embedded plat- form characterized by su cient processing power capabili- ties (ARM Cortex-A8 Processor at 1 GHz with 512 MB RAM) and several I/O pins, while it also embeds an Ethernet port for communicating with the backbone network. On top of BeagleBone we attach a custom-designed PCB board (cape) that integrates our electronic components and features a slot for connecting a LoRa transceiver. More speci cally, the cape features the MK20DX128VLH5 micro-processor which is interfaced with the LoRa transceiver responsible to run all the requisite libraries for its operation. The micro- processor software is also responsible of implementing a polling mechanism to aquire measurements from the sensor nodes and also initiate the link quality experiments. For the LoRa transceiver we employ the SX1272 [19] chipset manufactured by Semtech, which is paired with a 4.5 dBi antenna.

LoRa Sensing Devices: The core module of our sensing devices is again the MK20DX128VLH5 [20]. The 32-bit ARM Cortex-M4 CPU, clocks up to 96 MHz and supports ultra-low power sleeping modes to allow for power e cient opera- tions. The node employs the same LoRa interface (SX1272) as the gateway device, attached to a 4.5 dBi omni-directional antenna. Each node is equipped with a varying set of sensors, as illustrated in Table 1, featuring 1, 3 or 7 sensors in total. The sensors utilized are gas concentrations probes (NO2, SO2, CO, NH3, O3), dust particle concentration PM2.5, PM10 and a temperature & humidity module. The micro-processor hosts a program that implements the sensor reading and collec- tion of measurements, and also the communication between itself and the SX1272 module. Fig.1(b) presents one sensor device attached with four gas concentration probes and a dust particle module.

Software Toolkit: Through the deployed list of devices, we continuously collect detailed air quality measurements, while also evaluate the performance of the employed LoRa communication links. The overall procedure is orchestrated at the GW level, which periodically polls the di erent sens- ing nodes that continuously remain in receive mode. Sensor polling is executed in a Round-robin fashion, instructing sensors to transmit collected air quality measurements (with an interval of 10 minutes) or to participate in a link quality evaluation experiment (executed twice per day). The two procedures are executed independently of each other, taking advantage of the employed polling approach, which enables us to avoid the impact of overlapping transmission inter- ference, when performing link quality experiments. Upon receiving a request for experiment, each sensing node trans- mits 10 consecutive packets at the data rate, payload length and transmission power that has been determined by the GW. The gateway sends the experiment settings embedded to the experiment request packet. The per-node link quality of the network is determined through the Packet Delivery Ratio (PDR) of the aforementioned experiments.

Sensor Device

Gateway Device

LoRa Agricultural Testbed

Testbed Topology

The LoRa Agricultural testbed consists of three LoRa Gateways (GW) that are deployed in three crop fields and 7 Sensing nodes that are scatted across the area of North Macedonia, Greece. The end nodes feature various sensors related with meteorological and agricultural measurements. We clearly observe that the testbed offers a wide range of wireless links that differentiate in terms of communication distance, elevation difference and LOS/NLOS conditions. For each node, we also note the amount of payload bytes transmitted when transferring the respective number of sensed parameters, which includes 5 Bytes per environmental parameter plus 9 Bytes of own protocol overhead, while it does not include the LoRa preamble, header and CRC. In Fig. 1 presents the topology of our testbed, while in Fig. 2 you can find the architecture of our system. Below we present the custom developed GW and sensing devices, as well as the software toolkit for obtaining LoRa performance measurements.

LoRa Gateway: The GW is based on the BeagleBone Black Rev. C board which is a low-cost, embedded platform characterized by sufficient processing power capabilities (ARM Cortex-A8 Processor at 1 GHz with 512 MB RAM) and several I/O pins. It also includes a USB port which is used for a 3G/4G interface for communicating with the backbone network. On top of BeagleBone we attach a custom-designed PCB board (cape) that integrates our electronic components and features a slot for connecting a LoRa transceiver. More specifically, the cape features the MK20DX128VLH5 micro-processor which is interfaced with the LoRa transceiver responsible to run all the requisite libraries for its operation. The micro-processor software is also responsible of implementing a polling mechanism to aquire measurements from the sensor nodes and also initiate the link quality experiments. For the LoRa transceiver we employ the SX1272 chipset manufactured by Semtech, which is paired with a 4.5 dBi antenna. Fig. 3(b) presents one LoRa Gateway device deployed in the field..

LoRa Sensing Devices: Our setup consists of two types of edge devices, the meteo and the agricultural. Both devices are power by Libelium’s Waspmote processing module an employs the same LoRa interface (SX1272) as the gateway device, attached to a 4.5 dBi omni-directional antenna. The meteo nodes features 9 sensors in total which provide measurements about temperature, humidity, atmospheric pressure, air speed, air direction, rainfall percentage and solar radiation. Also they utilize and the features from the agricultural nodes which are leaf wetness, soil moisture. The agricultural nodes features 5 sensors in total which provide measurements about temperature, humidity, atmospheric pressure, leaf wetness and soil moisture. The micro-processor hosts a program that implements the sensor reading and collection of measurements, and also the communication between itself and the SX1272 module. Finally, both sensing devices are battery powered and they are equipped also with a solar panel capable of recharging the batteries. The devices in every communication with the GW provide measurements about battery percentage and current provided by the solar panel in mA.Fig.3(a) presents one meteo device attached with a solar panel and the meteo sensors and Fig.3(c) presents an agricultural device attached with a solar panel and the agricultural sensors deployed in the field.

Software Toolkit: Through the deployed list of devices, we continuously collect detailed air quality measurements, while also evaluate the performance of the employed LoRa communication links. The overall procedure is orchestrated at the GW level, which periodically polls the different sensing nodes that continuously remain in receive mode. Sensor polling is executed in a Round-robin fashion, instructing sensors to transmit collected measurements (with an interval of 10 minutes) or to participate in a link quality evaluation experiment (executed once per day). The two procedures are executed independently of each other, taking advantage of the employed polling approach, which enables us to avoid the impact of overlapping transmission interference, when performing link quality experiments. Upon receiving a request for experiment, each sensing node transmits 10 consecutive packets at the data rate, payload length and transmission power that has been determined by the GW. The gateway sends the experiment settings embedded to the experiment request packet. The per-node link quality of the network is determined through the Packet Delivery Ratio (PDR) of the aforementioned experiments.