Predictive Site Survey for Location-Ready Wireless Networks

The question requires designing a predictive site survey for a wireless network that must be 'location-ready' in small office environments. The core concept here is client location tracking, which typically relies on trilateration or triangulation using signal strength (RSSI) from multiple access points (APs). For accurate location estimation, a client device generally needs to be heard by at least three distinct APs simultaneously to calculate a position in two-dimensional space. This is a standard requirement for Wi-Fi positioning systems (WPS) and location-based services.

Option A suggests only one AP per floor, which provides no redundancy or spatial reference for location calculation. Option B suggests two APs, which allows for basic coverage but is insufficient for precise 2D location triangulation, as two circles intersect at two points, creating ambiguity without a third reference. Option C specifies at least three APs per floor, which aligns with the fundamental geometric requirement for trilateration. This ensures that every point within the surveyed area has line-of-sight or sufficient signal overlap from at least three different sources, enabling the location engine to compute coordinates accurately. Option D suggests four APs, which may improve accuracy but is not the minimum requirement for 'location-ready' status; the question asks for the approach that must be considered, implying the baseline necessary condition.

The comment provided reinforces this by citing the Official Cert Guide, noting that trilateration requires several APs around each point, specifically mentioning 'at least three surrounding APs'. This confirms that the design must ensure a density of APs such that any location on the floor is covered by at least three APs.