To the Editor:

I read with interest Dr. Matt Lewis’ article “A Primer on Wireless Networks” [February 2004, page 69], and I agree the future is wireless. One point Dr. Lewis covered briefly was the range of the wireless network. Although the 802.11g signal may travel 300 feet, the actual working distance will be much less. This is especially true in an office setting with interfering electronic equipment and multiple walls/obstructions (especially walls built with metal studs). I installed a wireless network at my office, and the effective range was less than 50 feet. To get 54 megabits per second (Mbps), the range was even less.

Since even the fastest broadband Internet connection is probably less than 3 Mbps, this may not be of concern. For Ethernet connections between computers, however, this can create a bottleneck in the network. To get around this issue, wireless access points must be installed throughout the building. In my case, I was able to adequately cover the entire building with a wireless router and one wireless access point (approximately 6,000 square feet of coverage). The wireless network relies on a wired backbone, as the access points need to be hardwired to the network. I used category 6 cables because category 5 was too susceptible to outside interference and there was a loss of signal over long cable spans. Using this arrangement, one can roam from access point to access point with no service interruption. If hardwiring an access point is not feasible, signal repeaters are available, but overall data through them will be cut by 50 percent because bandwidth has to be shared.

Author’s response:

Dr. Dom Dera raises some very practical points about the actual versus theoretical transmission speed and transmission distance of wireless networks in a real office setting. In the article, I mentioned that wireless “boosters” may be needed to provide wireless signal coverage throughout the clinic. I did not distinguish between hard-wired “access points” and wireless “signal repeaters,” but the point is important. Signal repeaters, which may be needed if hard-wiring a clinic is not feasible or not permitted, pick up the signal broadcast from a nearby router or other repeater and then retransmit the signal at greater strength. Access points simply plug into a hard-wired network and allow many points of wireless transmission. The size and shape of the clinic will determine the number of access points or repeaters needed. Category 6 cables allow higher transmission rates than category 5 or 5E (up to 155 Mbps) and thus are less susceptible to signal degradation over distance.