Ethernet Considerations

Ethernet Considerations

When installing the APs, it is imperative to understand cable limitations for the data cable. If Category (Cat) 5 cable is going to be used, the AP must be located within 100 meters of the hub or switch to which it will be connected. The survey engineer should be aware of this, and part of the pre-site survey is to investigate where these infrastructure devices are located. If the survey report does not contain this information, the installer must verify the information and determine whether the AP is within that distance limitation.

For APs that will exceed the 100-meter limitation, consider using fiber-optic connections. You can use a number of converters to provide Ethernet-to-fiber translation. Although this cures the distance issue, it does introduce an issue with power. With fiber, you cannot send power over the optic cable. Because of this, many installers order an AC main outlet for AP location when using fiber. However, most of the APs that support PoE offer some type of power injectors (discussed in Chapter 9, "Discovering Wired Network Requirements"). You can resolve this issue by using a combination of fiber converters and a power injector.

Figure 12-16 shows a scheme that uses both PoE and fiber. In this particular example, the Ethernet switch is Cat 5 only and feeds an Ethernet-to-fiber converter placed in the same location as the switch. The other end of the fiber cable is located where there is AC power. This location must also be within 100 meters of the AP. At this location, the AC is fed to both the fiber converter and the power injector. From here, Cat 5 cable connects to the AP, carrying the necessary PoE as well as Ethernet. If the Ethernet switch supports fiber directly, you can eliminate one fiber converter.