Site Survey
Standards and topologies

A WLAN designer must be aware of the different 802.11 standards. A designer must also be aware of the limitations of 802.11 while designing a WLAN. Because the standard does not cover communication between APs across the wired backbone, it is recommended that the WLAN backbone consist of a single product from a manufacturer. Many applications require features not defined by the Institute of Electrical and Electronic Engineers (IEEE) such as roaming, load balancing, and wireless repeaters.

Just as with wired networks, the topology of WLANs may take many forms . But in reference to a WLAN, the term ‘topology’ does not refer to architectures such as bus or ring. Instead, it refers to the Basic Service Area (BSA), which is comprised of microcells. Each AP has an area of coverage referred to as a microcell or cell. In an installation consisting of a single AP this is a very simple concept. When multiple APs are installed, the cells must overlap so that the wireless connection is never interrupted while roaming from AP to AP. The main purpose of a site survey is to locate the proper placement for the APs and survey the cells to allow for proper overlap. Too much or too little overlap can cause disruption of the wireless connection to the client.

Sometimes the topology of the WLAN will be dictated by the layout of the wired LAN to which the WLAN will be connected . For example, if wired connectivity is only available along one side of a 9290 sq m (100,000 sq ft) warehouse, the distance limitations of a 100 m (328 ft) Category 5 cable run may not be sufficient to reach the recommended location of the AP. This is where the site survey engineer will have to be creative. There are many possible solutions, including the following:

  • Wireless hop using a repeater talking back to a wired AP
  • A repeater or a hub to extend the Category 5 cable run
  • A fiber link to provide connectivity on the other side of the warehouse

A site survey engineer is responsible for not only finding the best locations for the APs, but also for finding ways to connect the APs to the wired network. Therefore, it is crucial that the engineer have an understanding of wired networks. This understanding should cover wired LAN topologies, standards, and components.