March 2004 — Features
Print this article | Email this articleClick here to receive your FREE subscription to T.H.E. Journal
Finding Waves
Techniques for a Successful Wireless Site Survey
Wireless local area networks are the most widely adopted networking technology to hit the market in the last three years. They have the potential to make network applications and the Internet available anywhere on a campus so that students and faculty are no longer tethered to their offices or shared computer laboratories in order to connect to a computer network.
In early 2001, Saint Francis University in Loretto, Penn., undertook a study to create a wireless network in all of its academic buildings. The Center of Excellence for Remote and Medically Under Served Areas (online at www.cermusa.org), a telemedicine and distance learning research facility located on the university's campus, collaborated with Saint Francis on the effort. The university's goal was to create a wireless network to support an upcoming laptop initiative in which all incoming freshmen would receive notebook computers. CERMUSA's objective was to gain a better understanding of wireless technology, as well as to create a best-practices recommendation for schools and universities in the techniques of deploying a campus WLAN.
After a year of researching different methods of WLAN deployment, three different procedures that can be used to install a wireless network were identified. CERMUSA termed these three methods: E-Witching, Scientific Divining and Computer Modeling.
E-Witching
Electron witching, or e-witching, is akin to the approach used by early settlers in the Midwestern United States to find water sources for homes and farms. On these arid landscapes, visible sources of water such as streams and brooks were hard to find; however, potable water sources were often discovered flowing beneath the surface of the ground and a well had to be dug to capture the water. Skilled settlers, known as diviners, were often called in to locate these hidden water sources by using a forked stick (i.e., a divining rod) that would bend down when moved over a possible water source. The driller would then sink a well at this spot, most often with positive results.
E-witching works in a very similar manner. CERMUSA technicians used the software included with a wireless network card to measure the signal strength to various locations on campus. When it was determined that signal strength was too low to maintain a strong connection, a new access point was placed in the immediate area. Once a building had enough access points to provide sufficient coverage for the entire structure, the network administrator would use his software to individually configure each access point using a commonsense approach in regard to channel allocation.
Measuring signal propagation using the e-witching technique is a simple procedure. To begin, the site surveyor needs the following three pieces of equipment: a wireless access point; a wireless PC card installed on a laptop; and signal measurement software, which is typically included with a wireless card. After the wireless card and software have been installed on a laptop, the first task is to locate a starting point within the area where the WLAN is to be installed. This spot should be somewhere near the center of the proposed coverage area, and should be accessible for network and electrical wiring to be run to an access point.
