# Building Realistic Mobility Models for Mobile Ad Hoc Networks
## 2 Literature Review
### Approaches for MANET Performance Evaluation
#### Simulation  
By far the most common technique for the evaluation of MANET protocols is simulation. [PERSON] et al. (2000) [64] present a review of network simulations that specifically focused on ns-2. [PERSON] and colleagues (2002) [65] present a comparison of a simple flooding algorithm using three simulators (OPNET, ns-2, and GloMoSim) in which they highlighted the differences in the results from the different simulation software for apparently the same algorithm. They use a 1-km square with 50 nodes and random waypoint to evaluate the simulation software but not a particular protocol or world model. A survey of simulation techniques used by all research presented at the MobiHoc conferences from 2000 to 2005 has been conducted by [PERSON] et al. (2005) [66]. During that period, ns-2 is the most common simulation used. Other cited simulations are GloMoSim, QualNet, OPNET, and MATLAB, while a quarter of the surveyed research use self-built simulations. [PERSON] and colleagues highlight the issue deficiency in the details of the parameters used. Although they present a large table of simulation parameters (node count, world size, and wireless range), there is no evidence to suggest that these parameters relate to real-world MANET applications. [PERSON] and [PERSON] (2006) [67] have also critiqued the use of simulation for MANET research due to generalization and lack of rigor, which could contribute to inaccurate data yielding erroneous conclusions. Some of the issues raised are variation of results between different simulation packages (echoing [PERSON] et al. (2002) [65]), problems relating to layers within the protocol stacks of the simulators, lack of accurate reporting of the models (echoing [PERSON] et al. (2005), [66]), and lack of realistic world and mobility models. [PERSON] and colleagues (2006) have also provided an extensive overview of the simulators for MANET research and identified ns-2 as the de facto standard for network simulation. [PERSON] et al. (2009) [68] only discuss VANETs but identify a similar set of generic MANET simulation software, as well as some simulation software specifically designed for VANET and some mobility model generators. [PERSON] and [PERSON] (2012) [69] have developed a large-scale simulator that can handle 260,000 nodes, while [PERSON] and [PERSON] (2013) [70] report on a bespoke simulator to evaluate spanning, tree-based broadcast topologies in MANETs. The main issue with this custom-builtsimulators research is that it lacks benchmarking and independent verification of the simulation results. A more recent paper trend is to provide guidance on which simulator to use for MANET research. For example, [PERSON] and [PERSON] (2012) [71] survey ns-2, OMNET++, NCTUns, and GloMoSim, concluding that ns-2 and OMNET++ provide the best platforms, with ns-2 having a large number of available models and OMNET++ a powerful graphical user interface (GUI) and being better for development. [PERSON] et al. (2012) [72] cover the same simulation software, as well as Quelnet, Opnet, and J-Sim, and arrive at the same conclusions, while [PERSON] et al. (2014) [73] conduct a critical survey on simulations, such as ns-3, NetSim, TOSSIM, J-SIM, NCTUns, DRMSim, SSFNet, GrooveNet, TraNS, etc. A significant number of publications have raised problems with using simulations as a way of testing MANET protocols. Some of these compared different simulators using the same scenario and concluded that there are problems with using simulations. To reiterate, [PERSON] and colleagues (2002) [65] show that different simulation packages yield varied results and conclude that simulation is not an appropriate tool for evaluating MANET protocols. This is due to the fact that simulations are an abstraction, and therefore, no simulation can be genuinely accurate ([PERSON] et al. 2006, [74]). However, this does not necessarily negate their use for comparative purposes or for initial testing of concepts and algorithms.