During a site survey for a new wireless deployment in a multifloor office building, an...

Layer 1 interference analysis is foundational to the Cisco site survey methodology. When a spectrum analyzer reveals periodic noise floor spikes across multiple channels with no clear line-of-sight obstruction, the root cause is almost certainly a non-802.11 device — candidates include cordless phones, video cameras, microwave equipment, or radar systems triggering DFS events. The correct engineering response is systematic documentation: capture the time of occurrence, the specific frequency or frequency range, and the geographic location of the interference signature. This triangulation data enables correlation with physical devices present in the facility. Simply increasing transmit power (Option A) raises the noise floor for neighboring cells and worsens co-channel interference. Using WLC monitoring tools (Option B) is insufficient because the WLC cannot detect non-802.11 energy at Layer 1. Adjusting the channel plan (Option C) without fully characterizing the interferer is premature. Only Option D follows the correct Cisco survey methodology for Layer 1 analysis, leading to actionable AP placement adjustments. Reference: WLSD Study Guide — Wireless Site Survey Methodology, Layer 1 Spectrum Analysis, Interference Identification and Mitigation.