## 1 Introduction
### Related Work and Limitations  
With network simulation [14], a software program is used to represent the behavior of a network by imitating the interaction between different network entities (e.g., gateways, nodes, mobility attributes) in accordance with the underlying models. The networking protocols, the applications, and services, as well as the various environmental conditions and nodal attributes that the simulator supports, can be adjusted in a controlled manner to assess how the network and the protocols would behave under different conditions [15; 16]. In that way, the network simulation provides a repeatable and controlled environment for rapid prototyping and experimental evaluation [17]. However, simulation models are inherently limited in their potential for accurately capturing finer details of network functions, nodal mobility behavior, and wireless medium characteristics [18].  
Network emulation [19; 20; 21] comes a step closer to the real system by combining actual elements of a deployed network implementation with other simulated components. A fundamental difference between simulation and emulation is that while the former runs in virtual simulated time (advanced either through triggers by discrete events or by fixed increments), the latter must run in real-time. This real-time nature of emulation, often in combination with a physically distributed computation infrastructure, hinders the repeatability of a sequence of events, contrary to simulation [22]. Moreover, while emulation comes closer to the real world than a plain simulation model, it still suffersfrom inaccuracies in the modeling of the abstracted elements. Generally, the potential and limitations of the emulation methods have been discussed in the literature (see, e.g., [23; 24]).  
By employing a full-blown set of real components, testbed-based methods provide the most realistic alternative for testing networking scenarios [25]. In particular, testbeds can represent, in realistic terms, the mobile nodes' motion, which critically affects the operation of real MANETs. This is in contrast to emulationor simulation-based methods, which represent motion through idealized models that cannot accurately capture the effect of real-world limitations and/or other interactions of the nodes with the environment. This is the key reason why most of the current MANET testbeds put an emphasis on mechanisms for controlling and tracking the motion of the employed mobile devices. For the localization (also called positioning) process, used for tracking and monitoring the positions and movements of the mobile devices over time, several centralized and distributed techniques exist, targeting indoor and/or outdoor experimentation terrains. These techniques employ visual-based methods [26], Global Positioning Systems (GPS) [27; 28], Inertial Measurements Units [27], or beacon-based methods (e.g., RSSI techniques and Bluetooth low energy beacons [29]). Additionally, the realization and control of the mobile nodes' motion involve facilities responsible for the navigation of the mobile devices [30; 31], including components and mechanisms for obstacles and collision avoidance [32]. For a comprehensive survey of selected MANET testbeds, see [33; 34].  
Currently existing MANET testbeds, however, although certainly useful for experimentation in the field, are monolithic \"black box\" designs, targeting a narrow set of predetermined technologies, operational scenarios, or environmental conditions. As such, they cannot be easily employed for the investigation of protocols or operational scenarios of a greater scope.