Upgrading and Repairing Networks (5th Edition)

Just as you need to test new network configurations or PC configurations in a laboratory before rolling them out for production usage, you need to evaluate the placement of access points should you decide to get into wireless networking. Wi-Fi provides for roaming capabilities, but it also enables you to restrict users to selected access points if you choose to do so. First, decide how you want to use wireless networking and which users it can be used by in a productive manner. Next, decide how many access points you need and where to place them.

You'll have to do some experimentation. Read the vendor's documentation to get the basics of the coverage area that the product is capable of, keeping in mind that this is only a general figure. For example, you'll find that most access points are capable of covering larger distances outside, rather than inside, because there are fewer structural components , such as bricks or steel beams, that can block the signal. You should take a vendor's specifications about its particular product with a grain of salt. Your mileage can vary.

If you use wireless networking inside and want to cover the entire building, you'll have to test to see exactly how far the coverage is for each access point. Also note that several factors can influence the performance you'll get no matter where you place the AP. For example, each AP is capable of supporting only a limited number of users before the available bandwidth begins to become saturated . Wireless networking at 11Mbps is faster than the standard 10BASE-T network connected to a basic hub. Yet it's nowhere near as fast as having a dedicated connection to a Fast Ethernet switch. There will come a point where too many users competing for too little bandwidth will provide too little performance to make wireless networking practical. IEEE 802.11a operates at a higher bandwidth and can accommodate a larger amount of users and network traffic.

Another thing to consider is source of interference, such as microwave ovens and other wireless devices. If you employ Bluetooth devices, you need to be careful because the technology is still new and despite some of the literature you may read, it's still inconclusive whether Bluetooth (or HomeRF for that matter) can interfere with Wi-Fi communications. All three use the same ISM radio frequency band, and although hopping around on different frequencies and using direct spread spectrum technologies might serve to reduce the chance of interference, don't count on there being no interference at all. Instead, if you use multiple technologies, go back to your lab and test the devices to see what kind of throughput you are able to achieve. Another popular device is the 2.4Ghz cordless telephone. These telephones operate in the same band as some wireless networks and can cause problems when used in the vicinity of wireless networking devices.

And keep that microwave oven in the break room well shielded ! You can purchase an inexpensive device at most consumer discount stores that can measure the amount of microwave radiation that's leaking from a microwave oven. You might find that simply replacing an old microwave oven with a newer model cures any interference problems. And because most work places don't need a top-of-the-line microwave that can zap a baked potato in just a few minutes, go with a low-end model that uses less power.