WiFoo..The.Secrets.of.Wireless.Hacking [Electronic resources] نسخه متنی

Summary

This chapter has discussed several survey methodsautomated, assisted, theoretical, and manualand now you might be asking which one is the best. There is no definitive answer. Each has advantages and disadvantages. Most require some sort of actual walkabout to verify performance. Areas such as warehouses and factories floors will likely still need a manual survey because they typically are looking for maximum range per AP and utilize directional-style antennas, making assisted and automated surveys less economical (because you need more APs). A theoretical survey requires you to input the attenuation factors of all the contents of the facility, something most non-RF engineers will not know or understand, and something difficult to do at many factories and warehouses.

For facilities that have public exposure, or where aesthetics are critical, placement possibilities of the APs might not fit into an automated or assisted survey model.

Totally automatic surveys, although they might work in some instances, most often result in at least one of two negative effects on a WLAN: A much higher number of APs is required to ensure no missed coverage; and at the other end of the risk spectrum, you risk not having enough (or incorrectly placed) APs and therefore dead spots. In such cases, a manual survey is needed to determine where these dead spots are and why they exist. This in turn requires additional APs (or, at least, new AP placement).

For carpeted offices and other areas where the typical range of an AP is greater than needed for the AP-to-user density specified in the design, an assisted site survey can be effective. However, the effectiveness is contingent on the environment being very consistent. If the arrangement of users or of the environment varies widely, assisted surveys might be only partially effective. In either case, a manual survey for user density is needed (hence the term assisted site survey).

A combination of theoretical, automatic, and manual survey techniques is ideal. (Assisted is already a combination of manual and automatic.) Each offers its own advantages, but the bottom line is that there is a need to have expertise in manual survey techniques, regardless of which survey method is chosen.