## 3 Materials and Methods
### Development of ABM
#### 3.2.1 Model Designing  
Through the designing phase, all rules of behavior and properties of agents, topological environment, and the way agents interact with each other are documented by the natural language of modeler(s). This documentation actually serves as a textual model (this textual model is the conceptual model of an ABM, which is documented in natural language). ABMs designing can be viewed from two aspects of (1) _modeling purpose_ and (2) _model development approach_. In terms of modeling purpose, ABMs can be divided into two main categories of _phenomena-based modeling_ and _exploratory modeling_[52]. In case of phenomena-based modeling, researchers start with a known targeted phenomenon. Typically, that phenomenon has a specific pattern, known as a reference pattern. In exploratory modeling, a researcher can create a set of agents, define their behavioral rules, and explore the patterns that emerge. One might explore them merely as abstract forms similar to the case of cellular automata developed by [PERSON] [55]. In terms of model development approach, all ways used for developing ABMs range from _theory-based modeling_ to _evidence-based modeling_[56]. ABMs can be developed via a theory or a set of theories, actually a theory that determines the behavioral rules of agents or the statistical regularities that the model is designed to explain them. In contrast to theory-based ABMs that are constructed upon prior empirical studies and individual-level data [57; 58; 59; 60; 52]. ABMs can also be developed on the basis of evidence (i.e., personal perceptions and intuition). The evidence-based ABM is applied when researchers have a mental model concerning behavioral rules of agents of a system, and they are interested in understanding the collective behavior of that system when its agents interact with each other [61; 62; 63]. The relationship between modeling purpose and modeling development is Figure 5.  
In terms of modeling purpose, the model of this study is phenomena-based, because it is designed to simulate the diffusion of three MTTs over a specified time period, and in terms of model development approach, the model of this paper is both theory-based and evidence-based. It is mainly theory-based where real-world empirical data, theories, and extension of the works of [64; 65; 66; 67] have been taken into account (Every so often, previously built models are reused or extended by other researchers. This strategy, which is called TAPAS \"Take A Previous model and Add Something,\" is widely used in the ABM community. In this strategy, modelers take an existing model and successively modify it through adding new features or relating initial assumptions [68]), and it is (a little) evidence-based because some new variables (e.g., handset compatibility) are added by researchers. The model is discussed through nine following stages. Underlying Question of the Model  
The proposed model has been developed to help telecom strategists better answer the following questions:  
_The major question: What is the mechanism underlying the diffusion of three competing MTTs (i.e., 2G, 3G, and 4G) in Iran?_  
_The first sub-question: What are the elements of this mechanism?_  
_The second sub-question: How are these elements interrelated?_  
_The third sub-question: Which social complex network is more similar to that of Iran?_  
_The fourth sub-question: What are the critical drivers of MTTs diffusion in the country?_  
_The fifth sub-question: What are the appropriate scenarios for accelerating 4G technology diffusion?_  
Types and Classes of Agents  
Type of agents refers to agent breeds used in the ABM [52], and an agent class includes several agents sharing a similar behavioral rule(s) [58]. In this model, human-type agents have been used in five classes of (1) innovators, (2) early-adopters, (3) early-majority, (4) the late majority, and (5) laggards.