# Building Realistic Mobility Models for Mobile Ad Hoc Networks
## 3 Realistic Scenarios and Modelling Issues
### World Size and Simulation Time  
The application scenarios commonly discussed in the MANET literature present variations in world size (i.e., the physical or geographical area covered by the MANET). These different world sizes are often not considered when simulations are used. This issue is highlighted by [PERSON] and colleagues (2005) [66], who conduct a critical survey of the parameters used in papers published in MobiHoc from 2000 to 2005. The findings reveal that a majority of MANET-deployed areas are squareswith arbitrary dimensions. Consideration of some of the common MANET application areas, such as battlefields and vehicular and search and rescue networks, show that the areas employed have little bearing on the real world. 3.1.1. Realistic World Size for Different Scenarios  
Battlefield scenarios cover a wide range of military operations and as such, have a wide range of possible world sizes. If an entire campaign is under consideration, hundreds of square kilometres may be covered. Individual battles can be anything from a single building to an entire battlefront. In both cases, MANET and its modelling will not cover the size of the whole field of operation but rather an appropriately apportioned size of the particular operation covered by MANET. Within a campaign or even an individual battle, there will be a number of different operations aimed at particular targets. These might include securing a particular enemy artillery placement, a strategic river crossing, or supply route. Thus, within a battlefield, most communications are required within smaller units and areas rather than the whole field. The communication structure within a battle is hierarchical rather than peer-to-peer for relaying orders and returning current position and status. Many military operations are stand-alone, and most campaigns consist of multiple operations. It is usual to have an infrastructure available behind the battle lines, where MANET applications would generally be restricted to individual operations and providing communications both within the operation and via edge connections to the military command. Simulations should therefore model the physical size of typical operations. In urban warfare, certain buildings are of major strategic significance and typically become particular targets. Common examples include radio and television centres (to secure communications to the population at large), supply and storage facilities (to control supplies to the population and also to acquire additional supplies for the army), and buildings that are either tall or on top of hills (to gain tactical advantage). Outside a full-scale war, the need to carry out military operations on buildings is also highlighted by a number of incidents where one or more individuals have seized a building and the local authorities need to retake control. For such targets, an entirely realistic world size and field of operation is automatically determined by selecting a real building, which can be modelled in the simulation to cover sizes, layouts, possible movement patterns, and radio range. Thus, the modelling of an operation to secure a building presents a realistic scenario for a MANET simulation, and the development of a technique for doing this would provide a useful tool for MANET application researchers. VANETs present a very different world from that on a battlefield. In general, there are two common layouts considered for VANETs: city and highway (motorway). City scenarios typically cover a rectangular area of a few km\({}^{2}\). However, the actual sizes of cities vary enormously, and in terms of vehicular traffic, much larger areas are commonly relevant, particularly during morning and evening rush hours. For example, Liverpool city covers an area of over 100 km\({}^{2}\) with a commuter belt that is much larger. If VANETs are to be useful in relaying traffic information for cities, they may need to cover a wider area. Motorways present a very different world size and shape.