Introduction

When installing or upgrading a structured cabling plant, IT departments can demonstrate significant time and money savings by determining their wireless LAN (WLAN) requirements and folding them into the project right from the start. The reason is that while WLANs provide over-the-air communication in the access network in areas where mobility and portability are needed, they also create new cabling requirements at the back end, often in hard-to-reach places. It’s far less expensive and labor intensive to do all cabling at once, without ceilings, walls and other obstructions in the way, than to install WLAN cabling later as a separate project.

The most common way of deploying WLAN access points (APs) is to mount them in ceilings and cable them directly to an Ethernet switch port. Generally, a 15- to 20-foot piece of cable called a service loop is left in the ceiling (Figure 1) in case an AP later needs to be moved slightly to tune coverage or avoid interference from other RF devices, such as wireless phones and microwave ovens. Planning for those cable runs upfront, in addition to your other network cabling needs, is financially and operationally prudent, allowing your organization to purchase all the necessary materials and labor in bulk with a corresponding volume discount.

If you consider only your wired network as you plan for your new infrastructure, you’ll likely have to pull additional cabling for your wireless equipment as a separate project. You might also have to change out some switches and power injectors. That situation can be painful on a number of fronts.

Smart Planning for New Network Infrastructures

When you have the luxury to cable a building from scratch, it pays to include wireless networks in your upfront plan and budget.

By Ahmet Tuncay,

Chief Technology Officer and

Vice President, Trapeze Networks

and Paul Kish, Director of

Systems and Standards, Belden

Table of Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

After-the fact Costs . . . . . . . . . . . . . . . . . . . . . 2

How to Plan for WiFi . . . . . . . . . . . . . . . . . . . . 2

Telecommunications Room Considerations . . . . . . . . . . . . . . . . . . . . . . . . . 4

Cable and Power Types . . . . . . . . . . . . . . . . . . 6

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

What access doyou deserve?

Access Control

Can your devicebe trusted?

Virus definitions, Firewall, Encryption

End Point Integrity

Figure 1 . Additional cabling from telecommunications room switches to Wi-Fi mounting locations in ceilings should be accounted for in the upfront cabling plan, leaving a 15- to 20-foot service loop at the end as wiggle room in case AP locations later require adjusting.

Where to Install Wireless Cable

Other Floors

First Floor

Equipment Room or Data Center

Telecommunications Room

PoE Ethernet Switch

Router/ Firewall

Main Cross-connect

Public Switched Telephone Network

Internet

Service Loop

Data Video VoiceApplication Servers

Riser Cable

Ethernet Switch

After-the-fact Costs

The after-the-fact approach involves the cost of opening up ceilings and walls, as well as the possible cost of business downtime while the environment remains ripped apart. These factors can increase the overall cabling project cost by 2 to 4 times, depending on the size and structural complexity of the property. The greater the importance of aesthetics in a building, the more difficult and expensive the after-the-fact cabling job is likely to be (Figure 2).

For example, there might be costs associated with patching or repairing walls and ceilings. Network integrator quotes that include structured cabling often do not account for these expenses, which can rear their heads as unexpected “change orders” not covered by your budget.

An additional consideration is the cost of the cable itself. The cable can cost more if bought in an add-on, incremental quantity, rather than as part of your initial volume order.

Note, too, that the telecommunications room contains most of the equipment required for the distribution network that supports the wireless APs:

Ethernet switches, Power over Ethernet (PoE) switches and power injectors, phone system elements and uninterruptible power supplies, for example. These active devices require heating, ventilation and air conditioning (HVAC) and AC or DC power and can thus be more costly if installed after the building has been constructed.

These are among the reasons that a universal IT best practice is to evaluate all network infrastructure requirements any time a property is built or opened up for remodeling. IT personnel are accustomed to taking these opportunities to visit the cabling requirements of traditional Ethernet switches, desktops, printers, servers and routers. But wireless is a comparatively new network type for mainstream use. It simply might not occur to planners to piggyback the network design and cabling aspects of a current or future wireless project onto the wired one.

Both have significant cabling components to them, though, so they should both be taken into consideration. Viewing the wired-wireless

network design and cabling infrastructure as one cohesive project makes installing wireless, when you are ready, a smooth process with minimal associated costs and headaches.

How to Plan for Wi-Fi

If your new building is under construction, how do you know where ceilings will be for mounting APs? How do you plan around sources of interference that might eventually be present? Don’t you have to wait until the building is actually constructed to figure this out–when it’s too late to reap the costs of pre-planning? Fortunately, the latest Wi-Fi surveying and planning tools eliminate this chicken-and-egg situation by allowing you to electronically pre-design the WLAN before the building is even constructed.

Historically, most companies installing Wi-Fi have conducted a physical site survey by walking around the building, mounting independent APs in places estimated to be appropriate for the desired coverage and hoping for the best. If there were coverage holes or irregular performance in certain areas, they have carried handheld or laptop-based spectrum analysis tools to the area to troubleshoot the problem. They could then remount APs or change AP channels to improve performance and coverage.

That process has historically worked well for small installations of one or two APs. But it quickly becomes unwieldy as wireless networks become mainstream throughout the building. A healthy dose of automation is now necessary to appropriately plan and scale building-wide Wi-Fi networks.

2

Figure 2 . The site survey after building is more accurate than an automated survey, but then you cannot afford to audit the site for accuracy. An automated site survey gives you good accuracy and low follow up (audit) costs, making it a better value overall.

Building

100,000 square feet Option 1

Site Survey After Building is In (without automated tools) Approx . $8,400 Option 2

Pre-build Automated Site Survey Approx. $1,500Site Audit After Equipment is Installed Approx. $3,500Total Approx . $5,000

Sample Wireless Installation Costs

3

Figure 3 . Using automated site planning tools, which rely on blueprint information, allows you to know ahead of time where your AP cable drops will need to be.

Use Automated Site Planning Tools

It has become possible to easily design the entire wireless network before the building is even constructed. All you need is a blueprint for the structure and an automated Wi-Fi site survey tool. You can import the blueprint into the electronic survey and planning program, and it will automatically tell you where to place APs and how many you will need, based on your wireless goals and what type of Wi-Fi equipment you intend to purchase.

One such tool is the RingMaster® management product from Trapeze Networks, a Belden brand. RingMaster works with Trapeze’s Wi-Fi WLAN infrastructure equipment both to automatically create the wireless network design and to manage the wireless network post-deployment (Figure 3).

Such site-planning tools account for the impact of building materials, glass windows, metal doors and other RF attenuators. They base their design decisions primarily by taking into account these variables on the blueprint. But they also require some basic information from you. So you need to make a few upfront decisions, described below.

Make Certain Decisions Upfront

First you need to decide where in the building you want network connectivity. Then decide for each location whether that connectivity should be wired, wireless or both.

Ideally, to create an accurate electronic Wi-Fi design, you should know what applications your WLAN will support, who will have access to the network and where they are likely to roam throughout the building. Obviously, the location component

is more difficult to predict in a mobile user environment than in a traditional wire-line environment, where PC-to-Ethernet switch port connections remain stationary. However, your organization should decide whether it intends to give users near-ubiquitous coverage throughout the building or whether coverage in common areas will suffice.

That decision might depend on the wireless applications you wish to support. For example, wireless networks that will be supporting Voice over IP (VoIP) as all or part of an internal mobile voice strategy usually require a more dense, overall AP deployment than those that provide wireless data access. Data networking is far more tolerant of packet loss, delivery delays and jitter than voice. Voice requires stable, ubiquitous coverage and minimum delays when connections are handed off from AP to AP as a user roams.

Automated Site Planning Tools

Installing an AP in each of a few public areas (such as meeting rooms, cafeteria and lobby) might be sufficient for data access; however, consistent and predictable voice and location service support will require coverage nearly everywhere. That means more APs and, consequently, more cabling runs to more places.

The same density consideration applies to data connections in areas where large groups of people are likely to congregate and use the network simultaneously, such as in a university lecture hall or in a conference room at a trade show.

Choose an 802.11 Technology

You’ll also need to decide what Wi-Fi technology you will use in your network: 802.11n, 802.11g, 802.11a or some combination. This decision will affect cabling because these WLAN types run at differing throughput speeds and coverage ranges. They also differ in capability and performance. You might elect to install a greater number of legacy APs for coverage or select an AP that supports the latest standards for greater coverage and capacity.

Ideally, it makes sense for an organization to install the newest technology (Draft 802.11n) available in WLAN equipment, which generally offers per-radio data-connect rates of up to 300 Mb/s. Reasons to do so might include the following:

• A reluctance to invest in so-called “legacy” technologies. (See Deployment Tip Sidebar)

• A true need for Ethernet-like bandwidth because of high-consumption applications such as multimedia or all-wireless user access.

• Stability of cabling for wireless. Because you’ll be deploying the latest technology, you likely won’t have to change your WLAN design–or the associated cabling–for the foreseeable future.

Note that while 802.11a operates in the 5 GHz frequency band, 802.11g operates in the 2.4 GHz band. 802.11n can operate in both. These frequencies are relevant because the higher the frequency, generally, the shorter distance a transmission will travel. Also, RF signals at higher frequencies attenuate more as they travel through channels with obstacles, further limiting signal reach. Because of these transmission traits in the 5 GHz band, it might be necessary to deploy a greater number of APs to achieve the desired coverage (range of transmission) than when operating in the lower frequencies.

Your automated site-planning tool will figure out the math that goes along with these issues to determine appropriate placement and coverage.

APs, Placement and Channel Planning

Once you decide on the 802.11 technology(ies) you will be using and where you need wireless connectivity, you can use your site-planning tools to automatically lay out the wireless network for you. You upload a floor plan for

your facilities using a CAD drawing or even a clean JPG file. You simply input information about the desired coverage area of the network. Then, you ask the program to calculate how many APs you’ll need, where the APs should be placed and on what channels they should operate so as not to interfere with one another. The program will automatically build the layout and specify at what power levels each AP should transmit for the best overall operation, keeping in mind FCC and other regulatory power limitations.

The tool will automatically assign a channel plan to the wireless network. Your channel plan maps each AP to a specific non-interfering channel in the frequency band in which it works. This is somewhat analogous to creating “virtual cabling” over the air such that communications don’t bump into one another.

Once your wireless network design has been created, you can calculate your physical AP cabling requirements to those spots and include them in your overall project plan and bid.

4

Note that Draft 802 .11n is backward compatible with 802 .11a/b/g networks, so continuing to install these earlier technologies won’t preclude moving to 11n in the future . However, when mixed 802 .11a/b/g/n nodes share the air space in backward-compatibility mode, 11n clients are likely to take a performance hit . This is because, despite a number of airtime fairness mechanisms in Wi-Fi systems, the slowest device on the network is the gating device .

To avoid compromised 11n performance in a mixed-mode network, use an AP with two radios: one tuned to the 5 GHz band and the other tuned to the 2 .4 GHz band . Use the 5 GHz band for 802 .11n APs and clients, creating a “pure 11n” network in that band . Allow legacy 802 .11g clients to communicate with a 2 .4 GHz “G” radio in the other slot .

This way, legacy clients continue to operate as before, without impacting the newer, faster 11n nodes . If you wish to maintain some 802 .11a (a 5 GHz technology) in the mix, be prepared for 802 .11n to slow down .

Deployment Tip

Telecommunications Room Considerations

Note that once you know how many APs you’ll need on each floor, you should make sure to account for them in the number of Ethernet switch ports you purchase for your new or upgraded environment. Traditionally, network planners total up the number of desktops and printers they plan to have on a given floor, the number of servers in the data center, and the occasional router, storage device and other wired network device that may need to be connected. From there, they usually purchase and install a switch of sufficient size in each telecommunications room–one with at least as many ports as needed for known devices on that floor or in the data center plus a few extra for wiggle room and growth. That port count, on Ethernet Switches or PoE Switches and power injectors, should also account for cabled AP ports, a factor that might easily escape network planners. In addition, where you place your WLAN controllers*–management appliances that enable AP provisioning and management–plays a role in how many switch ports you need on a given floor. If you deploy a cluster of virtualized controllers all in the data center, for example, you’ll need a corresponding number of data center switch ports available to support them. If you distribute some out to the floors, the controller ports will have to be covered in the telecommunications room switch purchase.

Today, it’s advisable to procure gigabit- speed Ethernet switches for connecting wireless APs and controllers, given that products supporting the most current WLAN technology, Draft 802.11n technology, contain gigabit-speed uplinks. The reason for the gigabit-speed uplinks is that multiple users with 100 Mb/s or faster connections will be accessing an AP simultaneously. The uplink capacity should be sufficient to support the aggregate of the user connection speeds. Otherwise, the telecommunications room will become a wireless communications bottleneck (Figures 4 and 5).

5

What access doyou deserve?

Access Control

Can your devicebe trusted?

Virus definitions, Firewall, Encryption

End Point Integrity

Wireless Access Network11-54 Mb/s

PoE Ethernet Switch

WLAN Controller

Telecom Room10/100 Mb/s

Data Center10/100 Mb/s

Backbone Ethernet Switch

Access PointsClient Devices

What access doyou deserve?

Access Control

Can your devicebe trusted?

Virus definitions, Firewall, Encryption

End Point Integrity

Wireless Access Network108-540 Mb/s

PoE Ethernet Switch

WLAN Controller

Telecom Room10/100/1000 Mb/s

Data Center10/100/1000 Mb/s

Backbone Ethernet Switch

Access PointsClient Devices

1 Gb/s x N

Typical Capacity of Legacy Infrastructure†

Typical Capacity of an 802.11n Infrastructure†

Figure 4 . Legacy environments easily accommodate Wi-Fi’s 54 Mb/s maximum data connect rates with Category 5e or Category 5 cabling and 10/100 Ethernet switches.

Figure 5 . If you are deploying a Draft 802.11n Wi-Fi, strongly consider Category 6 cabling for supporting the gigabit-speed uplinks of 802.11n equipment. Similarly, telecommunications room switches and data center switches connected to APs and controllers should support gigabit speeds, and pay attention to the power requirements of the 11n gear. † Controller-based architecture

It is also advisable to install PoE switches or PoE injectors that can supply higher power levels to comply with IEEE 802.3at requirements. This allows nearly every type of Access Point to operate at its maximum performance levels (as some advanced features, such as future MMO designs, may require more power than is available from legacy IEEE 802.3af compliant PoE sources).

Cable Types and Power Delivery

If you deploy 802.11n now or plan to in the future and procure gigabit-speed switch ports accordingly, it is advisable to install minimum Category 6 copper cabling from your telecommunications room out across your floors and throughout the walls and ceilings. The reason is that Category 6 twisted-pair cabling provides better noise immunity and more “Signal-to-Noise” headroom for supporting gigabit-per-second speeds across Ethernet’s 100-meter standard distance. Installing Category 6 or higher Category cabling at your earliest opportunity, then, should future-proof your cabling plant for some time to come.

That being said, another somewhat thorny consideration as you are building out your unified wired/wireless infrastructure is device requirements for power. The Power over Ethernet (PoE) standard today, IEEE 802.3af, is widely deployed. It powers most Wi-Fi and cabled devices requiring up to 12.95 Watts sustained over Ethernet’s 100-meter limit across Category 3-and-higher Category copper wiring.

Be sure to check the requirements of the Wi-Fi equipment vendor you use, particularly if you decide to deploy 802.11n. To take advantage of all the enhancements to the 802.11 standard for improved throughput, coverage, and interference avoidance, some 802.11n systems require more power than PoE can provide.

Trapeze Networks 802.11n gear requires one 802.3af PoE injector supplying power to one port of a dual-radio AP in order for the AP to operate in 2x3 MIMO mode (with two transmitting and three receiving antennas). With 802.3af PoE on both ports, both radios can support full 3x3 MIMO (with three transmitting and three receiving antennas).

An emerging follow-on IEEE power standard, commonly referred to as PoE+, is in development by the 802.3at task force. With ratification expected during the second half of 2009, 802.3at will run across Category 5e-and-higher Category cabling to provide up to 24 Watts of power, or nearly twice that of traditional PoE. Pre-standard 802.3at switches and injectors are available from a number of vendors. In the case of Trapeze gear, draft 802.3at-compliant power used on only one AP port will power both radios in an 802.11n AP in full 3x3 mode.

If you find yourself embarking on a new network infrastructure project later this year, keep in mind the benefits of Category 6 cabling to support gigabit speeds and the availability of 802.3at power sourcing equipment as you make your equipment and cabling decisions.

Using 802.3at-powered equipment allows nearly every type of wireless AP to operate at its maximum performance levels without having to make any tradeoffs in terms of performance or feature support.

Conclusion

Planning the wired and wireless network infrastructure cabling together can lower overall cabling project costs by 2 to 4 times. Companies realize these savings largely by avoiding “after the fact” cable pulls that might require breaking open ceilings and walls and having to purchase extra cable in smaller volume at a higher price.

Companies that design the wired and wireless network environments together also make sure that they account for wireless APs and WLAN controllers* in the number of Ethernet and PoE switch ports that they procure for their telecommunications room and data centers.

It’s now possible to plan and design the wired/wireless network environment together before buildings are even constructed, thanks to automated site survey tools that are now available. Such tools, including Trapeze Networks RingMaster, gather data about the environment from a building blueprint and combine it with information entered by the network administrator about desired wireless throughput at a given range and 802.11 technology requirements. From there, the tool determines how many APs and controllers are required and where to install the APs for optimum performance.

Network planners are advised to keep the latest standards for cabling and PoE in mind as they plan their new environments. Depending on timing, it may be desirable to install higher performing cabling and PoE + capable equipment to ensure having the gigabit-speed cabling and power support in place to keep your company covered for many years to come. * In controller-based Wi-Fi networks

6Belden Technical Support 1 .800 .BELDEN .1 ©Copyright 2009, Belden Inc.

www.belden.com Wired-Wireless WP 2009