Planning the Wirelwss Lan


Planning the Wireless LAN
Implementing a WLAN that takes the best advantage of resources and delivers the best service can require careful planning. WLANs can range from relatively simple installations to very complex and intricate designs. There needs to be a well-documented plan before a wireless network can be implemented. In this topic, we introduce what considerations go into the design and planning of a wireless LAN.
The number of users a WLAN can support is not a straightforward calculation. The number or users depends on the geographical layout of your facility (how many bodies and devices fit in a space), the data rates users expect (because RF is a shared medium and the more users there are the greater the contention for RF), the use of non-overlapping channels by multiple access points in an ESS, and transmit power settings (which are limited by local regulation).You will have sufficient wireless support for your clients if you plan your network for proper RF coverage in an ESS.
When planning the location of access points, you may not be able to simply draw coverage area circles and drop them over a plan. The approximate circular coverage area is important, but there are some additional recommendations.
If access points are to use existing wiring or if there are locations where access points cannot be placed, note these locations on the map.
Position access points above obstructions.
Position access points vertically near the ceiling in the center of each coverage area, if possible.
Position access points in locations where users are expected to be. For example, conference rooms are typically a better location for access points than a hallway.
When these points have been addressed, estimate the expected coverage area of an access point. This value varies depending on the WLAN standard or mix of standards that you are deploying, the nature of the facility, the transmit power that the access point is configured for, and so on. Always consult the specifications for the access point when planning for coverage areas.
Based on your plan, place access points on the floor plan so that coverage circles are overlapping, as illustrated in the following example.
Example Calculation
The open auditorium (a Warehouse/Manufacturing Building Type) shown in the figure is approximately 20,000 square feet.
Network requirements specify that there must be a minimum of 6 Mb/s 802.11b throughput in each BSA, because there is a wireless voice over WLAN implementation overlaid on this network. With access points, 6 Mbps can be achieved in open areas like those on the map, with a coverage area of 5,000 square feet in many environments.
Note: The 5,000 square foot coverage area is for a square. The BSA takes its radius diagonally from the center of this square.
Let us determine where to place the access points.
The facility is 20,000 square feet, therefore dividing 20,000 square feet by a coverage area of 5,000 square feet per access point results in at least four access points required for the auditorium. Next, determine the dimension of the coverage areas and arrange them on the floor plan.
Because the coverage area is a square with side "Z", the circle that is tangent to its four corners has a radius of 50 feet, as shown in the calculations.
When the dimensions of the coverage area have been determined, you arrange them in a manner similar to those shown for Align Coverage Areas in the figure. Click the Align Coverage Areas button in the figure.
On your floor plan map, arrange four 50-foot radius coverage circles so that they overlap, as shown in the Plan. Click the Plan button in the figure.

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