Sample Answer
Design of a Wireless Local Area Network for Two Buildings
Introduction
This project focuses on the design of a wireless local area network to interconnect two office buildings, Block A and Block B, which are located one kilometre apart. The land between the buildings is owned by a third party and does not allow any form of cable installation. As a result, a wired interconnection is not feasible and a wireless solution must be designed.
Both buildings are multi-storey office environments with a high number of users, shared resources such as printers, and a central database server. The network must support intensive data transfer during peak periods while remaining reliable, secure, and cost-effective. This report proposes a suitable LAN architecture, calculates network load, identifies the placement of key network devices, estimates cabling requirements within buildings, and provides a cost analysis of the proposed solution.
Recommended Type of LAN and Justification
The most suitable solution for this scenario is a hybrid LAN design consisting of:
An internal wired Ethernet LAN within each building
A point-to-point wireless bridge linking Block A and Block B
Justification
Within each building, wired Ethernet is recommended rather than a fully wireless internal network. Wired LANs provide higher reliability, lower latency, and greater security, which is important given the volume of database traffic and file transfers. Ethernet is also more cost-effective for fixed office environments.
To interconnect the two buildings, a point-to-point wireless bridge operating at 5 GHz is the most appropriate choice. This technology can easily cover a one kilometre distance with line-of-sight, offers high throughput exceeding 1 Gbps with modern equipment, and avoids the legal restrictions associated with installing cables across third-party land.
This hybrid approach combines the strengths of both wired and wireless networking while minimising risk and cost.
Network Layout and User Distribution
Each building has the following characteristics:
5 floors per building
20 offices per floor
1 PC per office
Total PCs per building:
5 × 20 = 100 PCs
Total PCs across both buildings:
200 PCs
Printers are shared network devices and are assumed to be distributed evenly across floors.
The database server is located in Block A, meaning that all users in Block B access the database across the wireless link.
Average Network Load per User at Peak Time
To calculate the average load per user, all activities during peak time must be converted into bits per second.
Activity 1: Downloading a 300 MB file every 10 minutes
300 MB = 300 × 8 = 2400 Mbits
10 minutes = 600 seconds
Average rate:
2400 / 600 = 4 Mbps
Activity 2: Updating the database with 500 KB every 5 minutes
500 KB = 0.5 MB = 4 Mbits
5 minutes = 300 seconds
Average rate:
4 / 300 = 0.0133 Mbps
Activity 3: Sending 300 KB for printing every 30 minutes
300 KB = 2.4 Mbits
30 minutes = 1800 seconds
Average rate:
2.4 / 1800 = 0.0013 Mbps
Activity 4: Messages of 100 KB every 30 seconds
100 KB = 0.8 Mbits
30 seconds
Average rate:
0.8 / 30 = 0.0267 Mbps
Total Average Load per User
4 + 0.0133 + 0.0013 + 0.0267 = approximately 4.04 Mbps per user
