Wireless Is Not Wireless: Designing a Wi-Fi office or building network

Around the year 2000, there was a battle royale between fiber and copper cabling forces to capture the desktop. For more than a decade, unshielded twisted-pair copper—what many of us still call Cat 5—had ruled the local area network (LAN), but Cat 5’s struggle to meet the bandwidth needs of gigabit Ethernet made fiber look more attractive for desktop LAN connections.

While the fiber and copper forces were battling, an alternative appeared that essentially replaced the desktop cabling connection—wireless. Wi-Fi (IEEE 802.11) had less bandwidth than copper and fiber, but it was enough for most users and offered mobility as the big advantage.

With the advent of Wi-Fi and the introduction of the small laptop, tablet and especially the smartphone, wireless coverage became a requirement for every office. It remains that way today, even more so. Desktop cabling is essentially obsolete except for power users and security concerns.

But that doesn’t mean cabling is no longer necessary. Wireless is not wireless. Wireless devices merely replace the patchcord needed to connect a device to the network with a radio connection to a wireless antenna and network device called an access point; the access points then connect to the cabling system.

Designing a cabling system from scratch or upgrading a cabling system today requires the same robust backbone cabling as before. However, the horizontal cabling to desktop outlets for every user changes to connecting just a few Wi-Fi access ports.

Designing a Wi-Fi office or building network is more complicated than just providing cables to every desktop. You need to determine how many access points are needed, where to place them, how to mount them with thoughts to future upgrades and how to power them.

Each access point has limited bandwidth so the designer must first consider the density of users in an office or building environment. Dividing an office or building environment into fixed cells with an access point in the center of every cell looks reasonable until you understand that radio waves don’t always follow logical paths.

Radio waves interact with the building, furniture, each other and even the people. Various wireless frequencies interact with building structures differently. There is software that helps design Wi-Fi systems indoors, but eventually a test with access points and test equipment may be necessary.

Once Wi-Fi access-point locations have been decided, you must bring cabling to them. This is the application power over ethernet (PoE) was designed for. A single UTP cable can bring ethernet signals to the access point and power the device from the switch it connects to or another PoE source. To further simplify cabling, you can now get UTP plugs that can be attached directly to the cable at the wireless access point, so all you have to do is terminate the cable and plug it into the device. No more outlets or patchcords.

The big caveat is that you cannot scrimp on the quality of the UTP cable. Wireless access points can use a lot of power and need several gigabits of bandwidth. Recommendations are usually for Cat 6A cable with 23 AWG conductors. Smaller conductors limit the power delivery and add heat to cabling, which degrades performance. This is not a place for inexpensive cable bought online. Much of that cheap cable is counterfeit and uses poor conductors and plastics that are not flame retardant. Buy brand names from reputable distributors only.

While we’re talking about Wi-Fi, you may be wondering about indoor cellular systems, such as distributed antenna systems (DAS). About 80% of all cellular calls originate from inside a building. Many building codes call for wireless service for emergency personnel. So, what about DAS?

DAS is generally not an office or enterprise network issue, since most mobile cellular devices today can make calls on Wi-Fi. Carriers use Wi-Fi calling to reduce their traffic loads, thereby putting it off on private networks. Buildings may need to cover cellular networks and emergency networks, which may be on different systems and different frequencies.

A building DAS is another technology with different solutions. Cabling is generally single-mode fiber to an entrance facility in the building. A modern building should have a fiber network available for tenants already, so tapping into that network for installing a DAS is just a matter of adding some drops to the antennas along with some power and providing space for the system and backup power in the entrance facility.

About the Author

Jim Hayes

Fiber Optics Columnist and Contributing Editor

Jim Hayes is a VDV writer and trainer and the president of The Fiber Optic Association. Find him at www.JimHayes.com.

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