The corporate network is undergoing a major shift in emphasis that impacts cabling tremendously. The “traditional” corporate network that uses fiber optic backbones and category-rated unshielded-twisted pair (UTP) copper to the desktop is becoming a dinosaur. Today’s users expect mobility, demonstrated by the sales of laptops exceeding desktop computers and the popularity of mobile platforms, such as the Blackberry and iPhone, which approach laptop capability. And mobility means wireless.
Many workers carry laptops to meetings, on coffee breaks, while waiting in the airport and on airplanes. Network users don’t want to be tethered with patchcords; they are annoyed enough to have to plug in to recharge their batteries.
Wireless has certainly had its growing pains. Wi-Fi, as the IEEE 802.11 standard for wireless networks is popularly known, has been widely adopted, but has always been challenged to provide adequate coverage and bandwidth. Cellular data networks provided much better coverage than Wi-Fi but have been very slow.
But with the advent of the latest version of Wi-Fi, 802.11n, updated cell-phone data systems and the likelihood of success for WiMax, users now have adequate wireless bandwidth practically everywhere, even for video conferencing. Many mobile devices are now being offered with several connection options, usually Wi-Fi and cellular to make them usable practically anywhere.
Not every employee needs or wants a laptop or needs to be mobile, of course. Accounting, customer service, production control and engineering, for example, are still users of desktop computers. Engineering, in particular, often requires large amounts of bandwidth for big computer-aided design (CAD) files, necessitating the highest bandwidth—gigabit Ethernet as a minimum—be delivered to the desktop, often on fiber instead of copper. Most everyone else is adequately served with fast Ethernet (100 Mbps) over cables rated Category 5 or higher.
The network of the future certainly does not include replacing cabling every couple of years with another UTP upgrade. Most users today already have networks with fiber backbones and desktop connections on Cat 5e or Cat 6 and a few Wi-Fi access points. If 10G needs to be delivered to the desk, it’s probably going to be on fiber, not just for the bandwidth, but also for the lower power consumption of fiber optic links.
The future appears to include more mobile applications. With fiber backbones already installed in most large corporate networks, adding adequate wireless access is easy, and of course, upgrades are simply a matter of replacing wireless access point hardware; no recabling is required.
Wireless is not wireless
Although we talk about wireless becoming the network connection of choice, we sometimes forget that wireless is not wireless. In reality, the wireless connection only replaces the patchcord, which would otherwise connect the user into the network, with a radio link. That radio link connects the mobile device to a wireless access point (AP) that is hardwired into the cabling network.
Every AP must have a connection into the network, either over UTP or fiber. APs are available with either type of connection, and fiber optic versions are not that much more expensive. The choice between copper and fiber depends on the location of the AP, possible electrical or wireless noise interference issues, and the necessity of powering the AP over the cabling, which requires copper.
Designing and installing the premises cabling network to accommodate wireless APs requires consideration be given to several options that may be new to cabling installers and may require the expertise of specialists. Beyond the usual concerns of installing proper pathways and supports for the cables and ensuring UTP cable runs from telecom rooms to workplace outlets are kept under 90 meters, the needs of wireless add new concerns for cabling. These include how much bandwidth must be supplied to the AP, where should wireless access points be located, how will the AP be powered and how will security be managed.
It is important to provide good wireless coverage in the work area. This involves more than just where wireless access points are located. Networks share bandwidth, so the service provided depends on how much bandwidth is available and how many users are sharing that bandwidth. For wireless, this involves several issues, including how many users are being served and the physical layout of the building and its occupants.
The 802.11n standard is rated to provide up to 600 Mbps of bandwidth under ideal conditions, and we all know how often you have ideal conditions. In reality, it provides about 90–100 Mbps reliably. For an 802.11 AP to work efficiently, it needs a reliable gigabit Ethernet connection. In the past, most users just plugged access points into any port in a telecom room, so it was sharing bandwidth with other users. To get best performance, a wireless AP may require cabling back to the main equipment room rather than to an overworked switch in a local telecom room. This needs to be decided by the customer’s networking expert before the cabling design is done.
Location, location, location
In an office, APs generally are installed above the ceiling or on a convenient wall. An AP is rated to cover a certain radius, but it may not work to just install APs with overlapping coverage. The coverage any AP provides depends on the environment—as objects such as walls, office partitions, desks and even people absorbing and reflecting wireless signals—affect the coverage. Complicating this is that 802.11n actually can use reflections as signal paths.
Manufacturers’ AP coverage diagrams often look like a nice circle (see figure), while actual coverage is generally much more irregular. Now specialists can bring instruments into the office and make tests that will determine where to locate APs for best coverage. These tests are important to ensure proper wireless functionality in any office or building space.
Power for wireless
Every AP needs power. Providing AC, conditioned and uninterruptible power as needed by all network components is one solution. The ability to power wireless APs over unshielded-twisted pair copper wire has been developed for components, such as APs and voice over Internet protocol (VoIP) phones, but may not be possible in all applications. The current version of power over Ethernet (PoE, IEEE standard 802.3af) only provides about 13W power, which while adequate for early versions of Wi-Fi, may not be enough for all manufacturers’ implementation of 802.11n APs, which basically includes six separate transceivers to deliver higher bandwidth.
A higher power version of PoE, IEEE 802.3at, delivers almost twice as much power, but still may be inadequate for 802.11n APs and may cause heating of the UTP cable, which degrades the performance. Some vendors have developed 802.11n APs that will operate on the original PoE, some have suggested installing a separate UTP cable for power, and others prefer local AC power, which allows an option of copper or fiber to the AP. Before the final design is finished, the issue needs to be settled as it affects the need for AC power and/or the cabling required.
Security in wireless networks
A big issue for wireless networks is security. Any wireless access point is a potential security breach because anyone with a Wi-Fi device, not just a laptop, can access the network. You can create password access, but any wireless access point allows hackers an opening to crack your network security, sometimes even from outside your premises. Security experts warn that many security breaches are inside jobs, so multiple levels of security are desirable.
Wireless access usually allows both employees and visitors to connect on your network. When a company’s wireless network must also accommodate visitors, they generally should only be allowed direct Internet access, not access to the company’s network.
Securing a wireless network properly requires completely isolating the wireless network from the company’s wired data network, including using separate cabling and special wireless routers. Cabling to the access points connects to special routers in the telecom rooms that connect to special servers over backbone cabling that is independent of the wired data/VoIP network. That means the IT manager now has two independent cabling networks to worry about, in addition to protecting his or her networks from encroachment by other applications, and the cabling installer may have two independent networks to install.
Before the installation
Wiring for wireless involves different concerns from simply building a wired network to every desktop. In order to build a cabling system to provide the required service, it is necessary to consider issues well beyond the traditional cabling standards, e.g., keep Cat 5e/6 runs under 90 m (280 feet), don’t kink cables and don’t untwist pairs more than 13 mm (½ inch).
To cable wireless correctly, the cabling contractor needs to confer with the company’s networking manager and security person, if they have one; the manufacturers of the wireless APs; and even the electrician. This will insure proper design of an optimum cabling system to support quality wireless service.
HAYES is a VDV writer and trainer and the president of The Fiber Optic Association. Find him at www.JimHayes.com.