# Can the WiMAX IEEE 802.16 Standard Be Used to Resolve Last-Mile Connectivity Issues in Botswana?
## 4 Material and Methods
### Proposed Network Model  
The simulation network topology for this study is shown in Figure 2 and involves the following devices:  
\begin{table}
\begin{tabular}{c c c} \hline \hline Subscriber Stations & 10 km from the Base Station & 20 km from the Base Station & 30 km from the Base Station \\ \hline \multirow{6}{*}{\
\begin{tabular}{c} Applications Configuration \\ (Client-server) \\ \end{tabular} } & File Transfer (FTP) & High Load \\  & File Transfer (FTP) & ToS Best Effort (0) \\ \cline{2-3}  & Audio (VoIP) & PCM Quality Speech \\ \cline{2-3}  & Audio (VoIP) & ToS Interactive Voice (6) \\ \cline{2-3}  & & High-resolution video \\ \cline{2-3}  & & ToS (Type of service): Streaming Multimedia (4) \\ \cline{2-3}  & Video Conferencing & Note: \\ \cline{2-3}  & & start-time = Constant (100) for all the applications \\ \cline{2-3}  & & applications run over TCP/IP and UDP/IP \\ \hline \multirow{6}{*}{
\begin{tabular}{c} WiMAX Configuration \\ parameters \\ \end{tabular} } & Type: & Wireless OFDMA 20 MHz \\ \cline{2-3}  & Node Position: & Circular \\ \cline{2-3}  & Antenna gain (dBi): & \(-15\) \\ \cline{2-3}  & Transmission power: & \(0.5\) W \\ \cline{2-3}  & Duplexing: & TTD \\ \cline{2-3}  & Number of Subcarriers: & \(2048\) \\ \cline{2-3}  & routers with PPP ports: & \(4\) Mbps data rate \\ \cline{2-3}  & Default Routing Protocol: & OSPF \\ \hline \multicolumn{3}{c}{MPLS} & disabled \\ \hline \hline \end{tabular}
\end{table}
Table 2: Summary of simulation parameters.  
Figure 1: Applications attributes.  
A base station (Device Name: wimax_bs_ethernet4_slip4_router): A base station sends and receives signals between a transmitting and a receiving point. For example, in mobile/cellular communication, the base station facilitates connection within a given area if the service provider is directly connected.
2. Three servers (ppp. server model): A server node with server applications running over TCP/IP (transmission control protocol/internet protocol) and UDP/IP (user datagram protocol), and which supports one underlying SLIP connection. The data rate of the connecting link determines the operational speed to model the file transfer, audio, and video, respectively.
3. A node (ip32_cloud- node model): An IP cloud supports up to 32 serial line interfaces and models IP traffic at a selectable data rate and routes IP packets through a cloud interface to the proper output interface, based on their destination IP addresses. Routing protocols automatically and dynamically create cloud routing tables for directing the transmitted packets.
4. Fifteen WiMAX subscriber stations: Subscriber stations are often referred to as CPE (customer premises equipment), as they provide access at the customer side. Five subscriber stations were placed 10 km from the base station for the study, and another five subscriber stations were 20 km from the base station. The last five subscriber stations were 30 km away.
5. The link (ppp_adv point-to-point link): Connects two nodes with serial interfaces (routers with PPP ports) at a selectable data rate. The transmission link connects the base station and the IP cloud with the servers for this study.