## 11 Hardware and Testbeds
### Hardware Testbeds  
Hardware testbeds involve deploying of hardware devices, such as multiple types of cameras with different resolutions and image-processing abilities, and wireless communication hardware that may support multiple standards and different data rates. Besides that, hardware testbeds provide supporting software for data monitoring and user interface. Depending on the hierarchal organization supported by the network, Hardware testbeds can be further divided into single-tier or multi-tier testbeds:  
**A) Single-Tier Hardware Testbeds:** Meerkats [99] is a testbed of wireless network of battery-operated camera nodes used for monitoring and surveillance of wide areas. The Meerkats node, which is based on Stargate board and using 802.11b wireless card, is equipped with sufficient processing and storage capabilities (when compared to a Cyclops node) for running relatively complex image processing algorithms. The goal of the work is to measure the tradeoff between application-specific performance and power efficiency (or network life time) for a given resource management strategy. Meerkats currently composed of eight visual sensor nodes, each of which consists of -as we mentioned-a battery powered Crossbow Stargate board, which has an XScale PXA255 CPU (400 MHz) with 32 MB flash memory and 64 MB SDRAM, connected with a Logitech QuickCam Pro 4000 webcam via USB and IEEE 802.11b PCMCIA wireless card. The Stargate platform is selected for the Meerkats node because it is running an open source operating system (Linux kernel 2.4.19), it can be easily connected to a webcam, the image sensor in Meerkats node, and it provides sufficient processing and storage capabilities. A laptop acts as base station or information sink running a multithreaded server program. For energy conservation, the Meerkats node operates according to a specific duty cycle in which it switches periodically its components (processor, camera, radio) into different operation states (sleep, idle, active) and performs a specified tasks. Meerkats's energy performance evaluation can be seen at [113]. The Meerkats node performs all the image-related tasks such as image acquisition, processing, and compression when it is in the active state. For example, for event detection, the moving blobs in the image are detected using a fast motion analysis algorithm and the relevant information is compressed using JPEG standards. The communication, based on multi-hop routing, between Meerkats nodes are established using the Dynamic Source Routing (DSR) routing protocol through IEEE 802.11b links. The Mobile Emulab network testbed [114] provides a remotely accessible mobile wireless and sensor testbed. The mobile testbed can provide accurate positioning and monitoring using video camera equipments, and enable automated experiments by both on-site and off-site users by using open-source software and COTS equipments. The testbed consists of Acroname Gracia robots attached with Mica2 motes, Stargate boards with IEEE 802.11b cards, and low-cost Hitachi KP-D20A cameras. The testbed is used in an indoor field of sensor-equipped motes and webcams, and can provide simple path planning as well as vision-based tracking system accurate to 1 cm. Mobile Emulab testbed allows remote user to position the robots, control all the computers and network interfaces, run arbitrary programs, and log data in a database. Emulab testbed allow, through precise positioning and automation, quick evaluation of localization and mobility protocols in sensor-driven applications. Low-cost, vision-enabled, and flexible autonomous mobile robots were designed in the Explorebots testbed in [115] for indoor experimentation on multi-hop ad hoc and sensor networking. The wireless robots are equipped with MICA2 sensor motes for sensing and wireless communication, in addition to built-in electronic compass, velocity and distance sensors, motor movement control, and sonic-based ranging sensors that can be used for navigation.