Hardware Selection

After progress had been made in transmitting a text message from one computer to another via the Simulink-USRP2 interface, the actual hardware on which this system would be implemented needed to be selected. Work on the Simulink program and improving its resiliency would continue, but the team had to now also work on selecting, purchasing, and testing the equipment. This was a vital part of the project because it is this hardware that would eventually be placed on the UAVs and run the overall communications system.

59 First, the team had to decide upon which hardware components would be needed for the system. Because the team was only responsible for the communications, this included all equipment that would be involved with this process. Overall, the system would be required to transmit data from the drones to the mothership, have the mothership compile and prioritize the information, and then transmit it to the base station. This process would thus need hardware capable of a drone-mothership link, signal processing, and a mothership-base station link. The separate hardware components were selected to meet these specific needs.

To enable the drones to communicate with the mothership, a basic Wi-Fi link was used. Because Wi-Fi has a limited range, an amplifier and antenna was needed to increase the transmission distance. The Bullet M Wi-Fi radio amplifier was selected for this application. An example of the Bullet M can be seen below.

Figure 42: The Ubiquiti Wi-Fi Bullet M [69]

The Bullet M weighs a light 0.18 kg, which is important when trying to cut weight on a UAV. It consumes up to 600 mW of power, has a data rate of 100+ Mbps, and a range of several kilometers [69]. These specifications made the Bullet M unique among Wi-Fi amplifiers, enabling it to have a relatively large range with low power and weight requirements. The Bullet M was the ideal choice for the drone-mothership communications. However, due to budget constraints, the team was only able to purchase one unit for $80. It is sufficient for testing, but further funding will need to be acquired in order to purchase more units and install them on all the UAVs.

60 The next important purchase item was the motherboard. This component was required for compiling all the incoming data from the other drones into one data stream that could be sent to the base station using software-defined radio. Specifically, the Simulink program the team wrote would carry out much of this task, which meant that the motherboard would need sufficient processing power to run MATLAB and Simulink and a gigabit Ethernet port to connect to the USRP2. After much searching, the team settled on the Axiomtek Pico820 motherboard, as seen below.

Figure 43: Pico ITX Motherboard [66]

The board was a small 100mm×72mm requiring a standard 5V power supply. It possessed a 1.6 GHz Intel Atom Z-series processor and 2 GB of RAM. These specifications meant that it would be capable of adequately running Simulink for the desired application. In addition, it had numerous input and output ports, including 4 USB 2.0 slots and a gigabit Ethernet port [66]. This Ethernet port was an important requirement in order for it to interface with the USRP2. The board was purchased for $550, making it the largest expense. However, only one was needed to place on the mothership; separate computers would perform any required computation on the drones and base station. Thus, this Pico ITX would meet all of the required processing needs for the communications system.

Two additional components were the solid state drive and the radio amplifier. The drive was needed as storage for the motherboard and to complete the fully-functioning computer that

61 would run Simulink. The team selected the ADATA 30 GB mSATA Internal Solid State Drive. It was chosen because of its large storage capacity, small 51mm×30mm×4mm footprint, high 280 MB/s data transfer rate, minimal 1.5 W power consumption, and reasonable $65 price [68]. A picture of it can be seen below.

Figure 44: ADATA 30 GB Solid State Drive [68]

The other additional component, the radio amplifier, was needed to provide additional power to the USRP2 and increase its transmission range. The ECE Wireless Laboratory already possessed such an amplifier, the MiniCircuits ZX60-33LN Low Noise Amplifier, so that is the one the team selected. It had a bandwidth of 50 to 3000 MHz, a gain of 16.5 dB, and a required DC voltage of 5.5 V [67]. These specifications, along with its small size, made it ideal for increasing the USRP2 range. In addition, using the one already supplied by the ECE department saved the team the $80 on the price. The amplifier can be seen below.

Figure 45: MiniCircuits ZX60-33LN Amplifier [67]

A table detailing all of these specifications for the different components can be seen in table 13.

62 Table 13: Hardware Specifications [66], [67], [68], [69]

Ubiquiti Bullet M  Weight: 0.18 kg

 Power: 600 mW

 Data rate: 100+ Mbps

 Range: several kilometers

Axiomtek Pico820  Size: 100mm×72mm

 Power supply: 5 V

 Processor: 1.6 GHz Intel Atom

 RAM: 2 GB

 Ports: gigabit Ethernet, 4 USB 2.0

ADATA mSATA Solid State Drive  Capacity: 30 GB

 Size: 51mm×30mm×4mm

 Transfer rate: 280 MB/s

 Power: 1.5 W

MiniCircuits zx60-33LN Amplifier  Bandwidth: 50 to 3000 MHz

 Gain: 16.5 dB

 Power supply: 5.5 V