Advanced Site Survey Techniques Flashcards

What is the primary purpose of a predictive site survey in WLAN design?

Answer: To model RF coverage and capacity using floor plans before deploying equipment

Predictive site surveys use software tools to simulate RF propagation on imported floor plans, allowing designers to plan AP placement, channel assignments, and power levels before any equipment is physically installed.

What information should be gathered during a pre-survey site visit?

Answer: Building materials, ceiling heights, existing infrastructure, RF interference sources, and client requirements

A thorough pre-survey visit documents construction materials (wall composition, glass types), ceiling types and heights, existing cabling and mounting points, potential RF interference sources, aesthetic requirements, and client needs.

What is the difference between a passive and active site survey?

Answer: Passive surveys listen to existing RF without associating; active surveys connect to the network and measure performance

Passive surveys capture RF data (signal strength, noise, interference) without connecting to any network, while active surveys associate with the WLAN and measure actual throughput, latency, packet loss, and roaming behavior.

How does RF attenuation differ between 2.4 GHz and 5 GHz when penetrating building materials?

Answer: 5 GHz signals experience greater attenuation through most building materials than 2.4 GHz

Higher frequency signals (5 GHz) experience greater absorption and attenuation when passing through building materials compared to lower frequency signals (2.4 GHz), resulting in shorter effective range.

What is a spectrum analysis and when should it be performed during WLAN design?

Answer: An analysis of the RF environment to identify interference sources, performed during the site survey phase

Spectrum analysis identifies sources of RF interference (microwave ovens, Bluetooth, radar, cordless phones) by analyzing the radio frequency spectrum, and should be performed during the site survey to inform AP placement and channel planning.

What is the recommended minimum signal-to-noise ratio (SNR) for reliable VoWLAN (Voice over WLAN)?

Answer: 25 dB or higher

Voice over WLAN requires an SNR of at least 25 dB to maintain call quality, which is higher than the minimum for data applications due to voice's sensitivity to latency, jitter, and packet loss.