August 11, 2008
Automated WLAN design
LANPlanner earns its keep by using per-site RF models to create WLAN designs that meet stated coverage and capacity requirements. Designs can be generated by adding APs manually or letting LANPlanner place APs where needed automatically. Most users should start with the latter, using manual adds, moves, and deletes to reflect necessary refinements (such as sliding proposed APs to more convenient mount points.)
Either way, design starts by selecting the kind(s) of AP to be deployed. Naturally, LANPlanner includes an extensive library of Motorola APs and requires no help to configure those AP’s capabilities or predict their default RF behaviors. It is also possible to define your own AP types to incorporate legacy devices in upgrade designs.
During automated design, a Quick Start AP Placement wizard asks for the maximum number of APs to be installed at this site, the type of air interface (802.11a or b/g) to be used, and whether redundant APs are required. Global settings determine max clients per AP, peak data rate, and any “fudge factor” to be subtracted for network overhead.
Next, the wizard lets you specify one or more “throughput regions.” These designated coverage areas are shapes, drawn on the 3D map, tied to peak data rate or minimum RSSI, number of clients, and average sustained data rate. The latter is easily specified by selecting one primary application from a pull-down list that includes Web surfing, videoconferencing, and VoIP (see figure 2-4). Regions can overlap to represent multi-use networks, but we did not see any ability to specify WMM priority.
“Exclusion regions” can also be defined–designated areas where APs should NOT be placed (or users do not need wireless access). We included a few exclusion regions in our design and found that LANPlanner does not try to avoid covering the area–rather it makes no attempt to ensure coverage there.
Quick Start uses these requirements to automatically place the optimal number of APs on the map, assigning channels and power settings to maximize signal-to-interference ratio (SIR). Quick Start also takes into account floor-to-floor interference, as well as co-channel interference generated by APs already on the map when invoked. A result summary indicates whether any clients lack sufficient coverage or capacity (for example, because doing so would require more APs than allowed by design parameters).