## 4 Technologies and Devices
### WiMAX  
Worldwide Interoperability for Microwave Access (WiMAX) is the radio communication technology used to connect the Local Control Unit with the World Wide Web. It is based on the IEEE 802.16 standard, with the intent of deliver Internet connectivity to areas where a normal DSL service is still difficult and expensive to install or in parts of cities not reached by 3G signals [5,30].  
The reason for choosing WiMAX is that in some parts of the city, e.g., very far from the downtown, sometimes, there is very scarce penetration of telecommunication lines or of the radio communication  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **RaspBerry** & **Arduino** & **Beaglebone** \\ \hline Base Price in US \$ & 25 & 35 & 50 \\ \hline Power Draw & \(\sim\)150 mA \# 5V & \(\sim\)50 mA \# 5V & \(\sim\)250 mA \# 5V \\ \hline Operating System & Linux & Custom & Linux \\ \hline Suited for & Software & Hardware & Software \\ \hline Number of I/O pins & 8 Digital & 14 Digital (6 PWM), 6 analog & 65 Digital \\ \hline \multirow{4}{*}{Peripherals} & 2 USB Hosts, 1 Micro-USB Power, 1 10/100 Mbps & None & 1 USB Host, 1 Mini-USB Client, 1 10/100 Mbps Ethernet \\ \cline{1-1}  & Ethernet & & \\ \hline Internet & Yes & _Via_ Shield & Yes \\ \hline \hline \end{tabular}
\end{table}
Table 2: Raspberry-Pi _vs._ Arduino and Beaglebone.  
coverage. In the best cases with clean line of sight (LOS) the radio link can cover up to 70 km [30]. Other technologies could be used to realize the remote communication such as 3G, satellite communication, WiFi or ADSL, but, as Table 3 shows, none offer the specific abilities of WiMAX. Excluding ADSL that needs a cable whose placement could be extremely expensive in these areas, and WiFi whose coverage is extremely short (less than 100 m), satellite communications offer worldwide coverage, but its subscription is usually much more expensive than a WiMAX or a 3G. The latter, always because is not profitable for the provider to create a 3G network, is not always active in these areas. For these reasons, WiMAX is a good candidate for this application. This would also allow diffusion of the SC paradigm in areas not properly considered as \"city\".  
In our system, we installed a base station (BS), spreading WiMAX single carrier TDD service at 3.4845 GHz center frequency and a bandwidth of 10 MHz. The BS transmitting antenna is an Argus tilt panel antenna model SPPX310M (65 deg Horizontal cut, 6.5 deg Vertical cut) [31].  
The total transmission power is 55 dBm EIRP given by the output signal of 37 dBm and an antenna gain of 18 dBi. The antenna was placed on the roof of a building at 30 m from ground level. To communicate between the main lamp post and the BS, we used a Huawei branded HES-319M outdoor WiMAX Customer Premise Equipment (CPE) [32], equipped with a 3.5 GHz 45\({}^{\circ}\) Cross-Polarization built-in directional antenna, with a maximum power at antenna port of 26 dBm and 14 dBi antenna gain. This allowed us to send reliably data at high speed. Furthermore, it avoids any type of interference with the ZigBee standard due to its different operating frequency.  
The WiMAX module uses 64 QAM5/6 modulation for the downlink when the CINR is higher than 30 dB and 16 QAM3/4 for the uplink [33,34]. Instead, when the CINR is lower than 10 dB, the link was still possible, but using a QPSK1/2 modulation because it is more robust at higher noise levels.  
The CPE is Power over Ethernet (PoE) 802.3 a/f compliant and it runs at 48 VDC, so a DC-DC step-up boost has been required to make the CPE working in our system. We used a \(\mathrm{LTC3863}\) mounted on its demonstration circuit 1286 A in order to boost up the 12 V from solar panel to the 48 VDC needed at the CPE PoE connector.