# Evaluating 60 GHz FWA Deployments for Urban and Rural Environments in Belgium
## 4 Network Planning and Optimisation  
### Simulation Tool  
To execute the FWA mmWave study, we designed a simulation tool which performs network planning simulations based on realistic 3D scenarios, accounting for multiple optimisation functions to find the most appropriate network topology [4; 51; 6; 4].  
The main novelties of the tool used in this study include where multi-bouncing ray tracing up to second-order reflections is needed and meshing capabilities for the backhaul network in the 60 GHz band. The new algorithm is presented in Figure 5.  
* _STEP 1_ : In the initialisation, the configuration files are loaded, and the scenarios defined. Those inputs include the following files: 1. Shapefile of the environment with the area information, such as buildings, vegetation and streets needed to determine the location of nodes. 2. The bit rate information of users, as defined by the requirements of the simulations. 3. The technology files describing the information needed to perform the link budget calculation as shown in Section 3.5.  
Figure 5: General network planning algorithm.  
Other configuration files such as the type of node location and type of environmental restrictions (rain or vegetation).
* _STEP 2_: The possible EN location generation defines the possible location of the nodes in the environment. It first determines the type of location required on the facades, lamp posts or both. Then, it assigns many possible sites based on a maximum number of ENs and evaluates if those are viable. This evaluation is based on [PERSON]'s shortest path algorithm [PERSON] (1998), where all the nodes must have at least one path to the PoP. The connections of each path are calculated based on the path loss between the nodes and minimum supported bit rate (i.e., 2.5 Gbps). Those possible EN locations that do not have a connection to the PoP are removed from the list. This process is called tree pruning and is shown in Figure 2. Then, the CPEs are located on the facades of randomly selected houses, and the bit rate and specific location are assigned to the CPE node.
* _STEP 3_: Once the location of all the nodes is known, a graph network generation is constructed for both CPEs and ENs nodes. First, a list of possible links from each CPE to all close ENs is created. For each connection, a link budget is calculated based on the requested bit rate and the path loss between nodes. The path loss calculation includes ray tracing and environmental factors such as rain and vegetation. A link is added to a viable link list if it fulfils the network requirements. Similarly, the backhaul network between ENs is created, creating links between ENs and accounting for an aggregated minimum bit rate of 2.5 Gbps for each link.
* _STEP 4_: The constraints and requirements for the graph network are assigned in this step. First, it identifies the optimisation objectives described in Section 4.3. The rules of each node and link are described in a model that is read by the mixer-integer programming (MIP). In this case, the problem objective is to maximise the number of connected users, while minimising the cost of the network which includes the infrastructure size, the accumulated path loss and the averaged hop count.
* _STEP 5_: The MIP solver uses the Gurobi Optimiser to solve the multi-optimisation problem based on linear expression to map the objectives of the problem into a possible solution [PERSON] et al. (2018). Once one or several solutions are found, the best one is assigned to the wireless network. In particular, once all the radio resources are allocated, each CPE node is assigned to an EN, and the backhaul network is created, calculating the capacity of each link and aggregating all the traffic up to the PoP node.
* _STEP 6_: In the last step, the algorithm calculates the network performance metrics, saving them in files for further post-processing. In addition, MATLAB scripts were created to collect and aggregate the results and print them, as shown in the results section.