HOW TO IMPLEMENT WIRELESS TECHNOLOGY

There are a number of decisions that need to be made for any wireless net- work implementation. These decisions are reasonably straightforward and in- clude access point placement, site survey considerations, required network services, and other decisions about how open your wireless network will be.

Access Point/Antenna Placement

Generally speaking, it is good to place the access point, or an external an- tenna connected to an access point, as high as possible within the area being served. For reasons of aesthetics and security, it is also good to place access points where library patrons will not see them. Good alternatives for access point placement include nonpublic spaces such as communications wiring clos- ets, storage areas, technical service areas, staff offices, and above ceilings. Wiring closets are ideal, because using them places your wireless network infrastructure in the same space as your wired network infrastructure, and there is a good chance that clean AC power is already available. One disadvantage of above- ceiling installations is the need to run an Ethernet connection, and possibly AC power in small implementations, to these odd locations. Another disadvantage of above-ceiling placement is the need to use a ladder when doing installations or service.

Site Survey Considerations

A wireless site survey is an essential part of almost any wireless network im- plementation. Whether the survey is contracted out or done in-house, the survey involves temporarily placing one or more access points in planned locations and then verifying the resulting wireless connectivity coverage area by systematically walking through the desired coverage area with a radio signal measurement de- vice and a diagram of the facility, marking coverage boundaries. Generally speak- ing, wireless network adapters come with free software that allows any portable computer equipped with a wireless adapter to function as the survey instrument. The wireless signal degrades primarily due to two factors, reflection and ab- sorption. As a radio signal encounters various objects it is either reflected or ab- sorbed. The more a signal is reflected, the more difficult it is for the receiver to discern the original signal from its accompanying reflections. Water is especially adept at absorbing 2.4 GHz radio signals; this is what makes water boil in a mi- crowave oven. Both reflection and absorption can make wireless networking within the stacks problematic. Some libraries have seen no problems at all in the stacks, whereas others had a tough time getting a decent signal to all points in the stacks. That’s why a site survey is so important. If a given library experi- ences large seasonal swings in humidity, it is conceivable that the wireless radio signal will be more readily absorbed in the library environment during the high humidity season, particularly in the stacks. The survey should be performed dur- ing the high humidity season or allowances made in the coverage boundaries.

The survey might also include scanning for preexisting radio frequency (RF) interference in the 2.4 GHz range. This is most likely to be an issue in situations where the library shares a building with other organizations, though proximity to buildings with certain industrial, scientific, or medical devices may also yield interference. Because the use of the spectrum is unlicensed, no one has special rights to its use. Resolution of conflicting use generally involves working out an agreement to use different channels and unique network names.

A key decision is whether you are designing the wireless network for maxi- mum coverage area or for maximum performance. Most libraries will design for maximum coverage and minimum cost. Enterprise-class access points generally have settings for large-, medium-, small-, and even microcell coverage areas. The large-cell setting is appropriate for maximum coverage. Be sure to set this parameter in the access points prior to doing the site survey.

If your library includes multiple floors, be sure to test each access point’s cov- erage area on all floors. The standard access point coverage area is three- dimensional and generally globe-shaped. It is not uncommon for a radio signal to penetrate two stories in either direction.

Required Network Infrastructure Services

Except for the smallest implementations, a wireless network rides on top of a wired network infrastructure. If the wireless network is to be used for Internet

access, the minimum services required of the network infrastructure include TCP/IP protocol support, either a DHCP service to provide Internet provider (IP) addresses to wireless clients or an assigned range of IP addresses, and appropriate network bandwidth back to library servers and to the Internet. In very small im- plementations where these services do not already exist, a single broadband router/access point/firewall device may provide a low-cost and simple solution.

Client Decisions

A decision that will influence other choices is whether only library-owned devices or both library-owned and patron-owned devices will be allowed to use the wireless network. If only library-owned devices will be allowed, then it is ad- visable to use a specific network name, also called a service set identifier (SSID), rather than the default. Furthermore, if the access point supports the feature, make it a closed network. This means that the access point will not broadcast the network name. Also, use the WEP encryption option and assign an encryp- tion key. With these settings enabled on your wireless infrastructure, only some- one who knows your network name and encryption key will be able to connect a computer to the wireless network.

If you intend to allow patron-owned devices to use the wireless network, you should probably use the default network name, use the open network option, and leave encryption turned off. Most wireless access points come with these settings as the default. With these settings, anyone who has a wireless device will easily be able to configure their device to utilize your wireless network. In most cases, their devices will be able to autodetect these settings and begin to use your network immediately.

Many organizations place their wireless access points outside the firewall. This is probably an especially good choice if you are going to allow patron- owned devices on the wireless network. This will work well if your library system is Web accessible. On the other hand, if your library system is not Web accessi- ble and requires specialized client software, placing the wireless network outside the firewall may require you to open up the firewall so much that it no longer protects your key networked assets from the global Internet. Consult with some- one who understands your complete technical environment to assist you in making this decision.