Wireless communication network consists of two parts (network infrastructures), the radio access network (RAN) and core network (CN). 4G-BWSim and 5G-BWSim focus on the RAN infrastructure which consists of three layers L1, L2 and L3. 4G simulator can simulate all the three layers whereas the 5G simulate the layer 1 end to end and elements of layers 2 and layer 3 but not complete layers. Both these simulators allows the designers/developers design the algorithms for radio access network but also optimize the methods/algorithms based on their customers need. Consider an example, an algorithm designed for mobile broadband may not be the best for IoT applications because the for mobile broadband applications the objective of algorithm design is to maximize the data-rate/throughput whereas for IoT applications data rate requirements are often low instead the power consumption is a major concern. Similarly, the protocols and algorithms designed for outdoor applications might not be the best for Indoor factory/gaming/V2X application. Hence, the terrain, scenario and use-cases plays a crucial role while designing the algorithms. The terrain and cell size are often captured by the channel model. In channel models, the small-scale parameters and large-scale parameters are calculated from data collected from a specific terrain. These parameters are characterized by the probability distribution function, mean value and the standard deviation. To make these channel model realistic these parameters maintain inter-parameter correlation, spatial consistency and correlation across space and time. On the other hand, the cell size has constraints on the base-station transmit power as the path-loss is lower and line of sight probability is higher in small cells (micro) compared to large (macro) cells. To design the whole network, the designers test their algorithms, protocol stacks and procedures implemented for different layers of the network using simulators.