A wireless site survey is a phase in the process of wireless network design. Generally it can be realized more than once, in some cases even after initial technical expertise of customer requirements and understanding the scope of work. Wireless site survey is simple for small apartments and single room offices where one access point (AP) is sufficient to provide network connectivity. On the other hand, in some situations it can be very complex activity in residential and business buildings or hotels with concrete walls, specific warehouses, garages, transportation means, campuses, retail centers and malls or construction sites and parks.
In practice, site survey implies a site visit for the purpose of optimal localization of access points and testing the radio frequency (RF) indoor and outdoor coverage within requested range, identification of all RF interference sources – like existing wireless networks with their APs and other RF transmitters, identification of power supply locations and existing infrastructure, analysis of building floor plans, etc. Detail facility inspection with end users and their IT management is very important for determination of “in-scope” and specific “out-of-scope” coverage areas, like elevators, air shafts or some other facilities.
Three categories of wireless site surveys can be recognized – passive, active, and predictive. Their main characteristics are, as follows:
- Passive site survey implies listening – reception of existing WLAN traffic and its access points detection, RF signal strength and noise level measuring. This is basic pre-deployment survey.
- Active site survey is always connected with different measurements like round-trip time, packet loss, throughput rates etc. Active surveys are intended for wireless networks troubleshooting or post-deployment performance verification and improvements. Two essential methodologies used for active survey are:
- Basic Service Set Identifier (BSSID) – this methodology is analyzing single AP performances – coverage (range), throughput, etc. A subscriber is signed to the AP’s radio MAC address, without roaming capability.
- Service Set Identifier (SSID) – this methodology is more suitable for post-deployment scenarios. It surveys the mobile subscriber that is signed to a SSID. During this survey, roaming performances between APs are tested. This methodology is used for multiple Aps survey and measurements.
- Predictive site survey involves simulation tools usage. For example, passive site survey reports are important to provide correct information about environment at the site, as necessary inputs for RF modeling software (AP coordinates, RF parameters like power and antenna height, antenna cables length and types, antenna types, walls thickness, large object positions etc.). A predictive site survey can be generally realized in these situations:
- When there is no network at the site, as a first step for future network performance predictions analyses.
- To determine budget frameworks for materials, hardware and implementation of the network. For that cause, on-site implementation of temporary – pilot APs is some of the best practices for precise coverage, data rates and roaming estimations and improvements.
After the wireless site survey is finished, it is important to build-in its results in further network design and deployment. A final product of wireless site survey is a report that usually contains APs locations, maps showing the floor plan with RF coverage / signal strength – as presented in Figure 1, spectrum analysis notes with RF interference details (for example adjacent – neighboring channels interferences, locations of smart devices embedded with wireless technology or existing wireless networks and their frequency plans), roaming requests, etc.
Figure 1. The floor plan with wireless coverage – WiFi heat map
It is very important to be aware that precise and detail wireless site survey report significantly contributes to optimal wireless network solutions, with accurate quantities of APs, cables, external power supplies, some additional network equipment and other materials, estimations of necessary labor and overall project costs
The site survey is an indispensable part of wireless network design that will ensure the delivery of requested network coverage and service quality. It provides cost-effective wireless network deployment and project realization in timely manner.