Belden - Trapeze Wired/Wireless White Paper


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Smart Planning for New Network Infrastructures

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Belden - Trapeze Wired/Wireless White Paper

  1. 1. 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 Smart Planning for New provide over-the-air communication in the access network in areas where mobility and Network Infrastructures 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, When you have the luxury to cable a building from scratch, it pays to include without ceilings, walls and other obstructions in the way, than to install WLAN cabling wireless networks in your upfront plan later as a separate project. and budget. 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 By Ahmet Tuncay, Chief Technology Officer and service loop is left in the ceiling (Figure 1) in case an AP later needs to be moved slightly to tune Vice President, Trapeze Networks coverage or avoid interference from other RF devices, such as wireless phones and microwave and Paul Kish, Director of ovens. Planning for those cable runs upfront, in addition to your other network cabling needs, is Systems and Standards, Belden 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. Table of Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Where to Install Wireless Cable After-the fact Costs . . . . . . . . . . . . . . . . . . . . . 2 Other Floors How to Plan for WiFi . . . . . . . . . . . . . . . . . . . . 2 Telecommunications Room First Floor Considerations . . . . . . . . . . . . . . . . . . . . . . . . . 4 Cable and Power Types . . . . . . . . . . . . . . . . . . 6 PoE Service Ethernet Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Loop Switch Telecommunications Room Equipment Room or Application Servers Data Center Data Video Voice Riser Public Switched Cable Telephone Network Main Cross- connect Internet Ethernet Router/ Switch Firewall 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.
  2. 2. After-the-fact Costs The after-the-fact approach involves the Ethernet switches, Power over Ethernet (PoE) network design and cabling infrastructure as cost of opening up ceilings and walls, as well switches and power injectors, phone system one cohesive project makes installing wireless, as the possible cost of business downtime elements and uninterruptible power supplies, when you are ready, a smooth process with while the environment remains ripped apart. for example. These active devices require minimal associated costs and headaches. These factors can increase the overall cabling heating, ventilation and air conditioning How to Plan for Wi-Fi project cost by 2 to 4 times, depending on the (HVAC) and AC or DC power and can thus be size and structural complexity of the property. more costly if installed after the building has If your new building is under construction, The greater the importance of aesthetics in been constructed. how do you know where ceilings will be for a building, the more difficult and expensive mounting APs? How do you plan around These are among the reasons that a the after-the-fact cabling job is likely to be sources of interference that might eventually universal IT best practice is to evaluate all (Figure 2). be present? Don’t you have to wait until the network infrastructure requirements any building is actually constructed to figure this For example, there might be costs associated time a property is built or opened up for out–when it’s too late to reap the costs of with patching or repairing walls and ceilings. remodeling. IT personnel are accustomed pre-planning? Fortunately, the latest Wi-Fi Network integrator quotes that include to taking these opportunities to visit the surveying and planning tools eliminate this structured cabling often do not account for cabling requirements of traditional Ethernet chicken-and-egg situation by allowing you these expenses, which can rear their heads switches, desktops, printers, servers and to electronically pre-design the WLAN before as unexpected “change orders” not covered routers. But wireless is a comparatively new the building is even constructed. by your budget. network type for mainstream use. It simply might not occur to planners to piggyback Historically, most companies installing An additional consideration is the cost of the the network design and cabling aspects Wi-Fi have conducted a physical site survey cable itself. The cable can cost more if bought of a current or future wireless project by walking around the building, mounting in an add-on, incremental quantity, rather onto the wired one. independent APs in places estimated to be than as part of your initial volume order. appropriate for the desired coverage and Both have significant cabling components Note, too, that the telecommunications hoping for the best. If there were coverage to them, though, so they should both be taken room contains most of the equipment holes or irregular performance in certain into consideration. Viewing the wired-wireless required for the distribution network that areas, they have carried handheld or laptop- supports the wireless APs: based spectrum analysis tools to the area to troubleshoot the problem. They could then remount APs or change AP channels to Sample Wireless Installation Costs improve performance and coverage. Building That process has historically worked well 100,000 square feet for small installations of one or two APs. But it quickly becomes unwieldy as wireless Option 1 networks become mainstream throughout Site Survey After Building is In (without automated tools) Approx . $8,400 the building. A healthy dose of automation is now necessary to appropriately plan and Option 2 scale building-wide Wi-Fi networks. Pre-build Automated Site Survey Approx. $1,500 Site Audit After Equipment is Installed Approx. $3,500 Total Approx . $5,000 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. 2
  3. 3. Automated Site Planning Tools 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 Such site-planning tools account for the is more difficult to predict in a mobile user impact of building materials, glass windows, environment than in a traditional wire-line It has become possible to easily design the metal doors and other RF attenuators. They environment, where PC-to-Ethernet switch entire wireless network before the building is base their design decisions primarily by taking port connections remain stationary. However, even constructed. All you need is a blueprint into account these variables on the blueprint. your organization should decide whether it for the structure and an automated Wi-Fi site But they also require some basic information intends to give users near-ubiquitous coverage survey tool. You can import the blueprint into from you. So you need to make a few upfront throughout the building or whether coverage the electronic survey and planning program, decisions, described below. in common areas will suffice. and it will automatically tell you where to place APs and how many you will need, That decision might depend on the wireless based on your wireless goals and what type Make Certain Decisions Upfront applications you wish to support. For example, of Wi-Fi equipment you intend to purchase. wireless networks that will be supporting First you need to decide where in the building Voice over IP (VoIP) as all or part of an internal One such tool is the RingMaster® management you want network connectivity. Then decide mobile voice strategy usually require a more product from Trapeze Networks, a Belden for each location whether that connectivity dense, overall AP deployment than those that brand. RingMaster works with Trapeze’s Wi-Fi should be wired, wireless or both. provide wireless data access. Data networking WLAN infrastructure equipment both to Ideally, to create an accurate electronic is far more tolerant of packet loss, delivery automatically create the wireless network Wi-Fi design, you should know what delays and jitter than voice. Voice requires design and to manage the wireless network applications your WLAN will support, who stable, ubiquitous coverage and minimum post-deployment (Figure 3). will have access to the network and where delays when connections are handed off they are likely to roam throughout the from AP to AP as a user roams. building. Obviously, the location component 3
  4. 4. Installing an AP in each of a few public areas Note that while 802.11a operates in the your facilities using a CAD drawing or even a (such as meeting rooms, cafeteria and lobby) 5 GHz frequency band, 802.11g operates in clean JPG file. You simply input information might be sufficient for data access; however, the 2.4 GHz band. 802.11n can operate in about the desired coverage area of the consistent and predictable voice and location both. These frequencies are relevant network. Then, you ask the program to service support will require coverage nearly because the higher the frequency, generally, calculate how many APs you’ll need, where everywhere. That means more APs and, the shorter distance a transmission will travel. the APs should be placed and on what consequently, more cabling runs to Also, RF signals at higher frequencies channels they should operate so as not to more places. attenuate more as they travel through interfere with one another. The program will channels with obstacles, further limiting automatically build the layout and specify at The same density consideration applies to signal reach. Because of these transmission what power levels each AP should transmit for data connections in areas where large groups traits in the 5 GHz band, it might be necessary the best overall operation, keeping in mind of people are likely to congregate and use to deploy a greater number of APs to achieve FCC and other regulatory power limitations. the network simultaneously, such as in a the desired coverage (range of transmission) university lecture hall or in a conference The tool will automatically assign a than when operating in the lower frequencies. room at a trade show. channel plan to the wireless network. Your automated site-planning tool will Your channel plan maps each AP to a specific figure out the math that goes along with non-interfering channel in the frequency Choose an 802.11 Technology these issues to determine appropriate band in which it works. This is somewhat You’ll also need to decide what Wi-Fi placement and coverage. analogous to creating “virtual cabling” over technology you will use in your network: the air such that communications don’t 802.11n, 802.11g, 802.11a or some combination. bump into one another. APs, Placement and Channel Planning This decision will affect cabling because these Once your wireless network design WLAN types run at differing throughput Once you decide on the 802.11 has been created, you can calculate your speeds and coverage ranges. They also differ technology(ies) you will be using and physical AP cabling requirements to those in capability and performance. You might where you need wireless connectivity, spots and include them in your overall elect to install a greater number of legacy you can use your site-planning tools project plan and bid. APs for coverage or select an AP that supports to automatically lay out the wireless the latest standards for greater coverage network for you. You upload a floor plan for and capacity. Ideally, it makes sense for an organization to install the newest technology (Draft 802.11n) available in WLAN equipment, which generally Deployment Tip offers per-radio data-connect rates of up to Note that Draft 802 .11n is backward compatible with 802 .11a/b/g networks, so 300 Mb/s. Reasons to do so might include continuing to install these earlier technologies won’t preclude moving to 11n in the the following: future . However, when mixed 802 .11a/b/g/n nodes share the air space in backward- • A reluctance to invest in so-called “legacy” compatibility mode, 11n clients are likely to take a performance hit . This is because, technologies. (See Deployment Tip Sidebar) despite a number of airtime fairness mechanisms in Wi-Fi systems, the slowest device on the network is the gating device . • A true need for Ethernet-like bandwidth because of high-consumption applications To avoid compromised 11n performance in a mixed-mode network, use an AP with two such as multimedia or all-wireless radios: one tuned to the 5 GHz band and the other tuned to the 2 .4 GHz band . Use the user access. 5 GHz band for 802 .11n APs and clients, creating a “pure 11n” network in that band . • Stability of cabling for wireless. Because Allow legacy 802 .11g clients to communicate with a 2 .4 GHz “G” radio in the other slot . you’ll be deploying the latest technology, This way, legacy clients continue to operate as before, without impacting the newer, you likely won’t have to change your WLAN faster 11n nodes . If you wish to maintain some 802 .11a (a 5 GHz technology) in the mix, design–or the associated cabling–for the be prepared for 802 .11n to slow down . foreseeable future. 4
  5. 5. Telecommunications Room Typical Capacity of Legacy Infrastructure† Considerations Wireless Access Network Telecom Room Data Center Note that once you know how many APs 11-54 Mb/s 10/100 Mb/s 10/100 Mb/s you’ll need on each floor, you should make sure to account for them in the number of WLAN Controller 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, PoE Backbone they usually purchase and install a switch of Ethernet Switch Ethernet Switch 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 Client Devices Access Points Ethernet Switches or PoE Switches and power injectors, should also account for cabled AP Figure 4 . Legacy environments easily accommodate Wi-Fi’s 54 Mb/s maximum data connect rates with Category 5e or ports, a factor that might easily escape Category 5 cabling and 10/100 Ethernet switches. network planners. In addition, where you place your WLAN controllers*–management Typical Capacity of an 802.11n Infrastructure† appliances that enable AP provisioning and management–plays a role in how many Wireless Access Network Telecom Room Data Center switch ports you need on a given floor. If you 108-540 Mb/s 10/100/1000 Mb/s 10/100/1000 Mb/s deploy a cluster of virtualized controllers all in the data center, for example, you’ll need a WLAN Controller 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. 1 Gb/s x N Today, it’s advisable to procure gigabit- speed Ethernet switches for connecting PoE Backbone wireless APs and controllers, given that Ethernet Switch Ethernet Switch 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 Client Devices Access Points accessing an AP simultaneously. The uplink capacity should be sufficient to support the Figure 5 . If you are deploying a Draft 802.11n Wi-Fi, strongly consider Category 6 cabling for supporting the gigabit-speed aggregate of the user connection speeds. 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. Otherwise, the telecommunications room will become a wireless communications † Controller-based architecture bottleneck (Figures 4 and 5). 5
  6. 6. It is also advisable to install PoE switches or PoE Trapeze Networks 802.11n gear requires Companies that design the wired and injectors that can supply higher power levels to one 802.3af PoE injector supplying power wireless network environments together comply with IEEE 802.3at requirements. This to one port of a dual-radio AP in order for the also make sure that they account for wireless allows nearly every type of Access Point to AP to operate in 2x3 MIMO mode (with two APs and WLAN controllers* in the number operate at its maximum performance levels transmitting and three receiving antennas). of Ethernet and PoE switch ports that they (as some advanced features, such as future With 802.3af PoE on both ports, both radios procure for their telecommunications MMO designs, may require more power than can support full 3x3 MIMO (with three room and data centers. is available from legacy IEEE 802.3af transmitting and three receiving antennas). It’s now possible to plan and design the compliant PoE sources). An emerging follow-on IEEE power wired/wireless network environment together standard, commonly referred to as PoE+, before buildings are even constructed, thanks Cable Types and Power Delivery is in development by the 802.3at task force. to automated site survey tools that are now If you deploy 802.11n now or plan to in With ratification expected during the second available. Such tools, including Trapeze the future and procure gigabit-speed switch half of 2009, 802.3at will run across Category Networks RingMaster, gather data about ports accordingly, it is advisable to install 5e-and-higher Category cabling to provide up the environment from a building blueprint minimum Category 6 copper cabling from to 24 Watts of power, or nearly twice that of and combine it with information entered your telecommunications room out across traditional PoE. Pre-standard 802.3at switches by the network administrator about desired your floors and throughout the walls and and injectors are available from a number wireless throughput at a given range and ceilings. The reason is that Category 6 twisted- of vendors. In the case of Trapeze gear, 802.11 technology requirements. From there, pair cabling provides better noise immunity draft 802.3at-compliant power used on only the tool determines how many APs and and more “Signal-to-Noise” headroom for one AP port will power both radios in an controllers are required and where to install supporting gigabit-per-second speeds across 802.11n AP in full 3x3 mode. the APs for optimum performance. Ethernet’s 100-meter standard distance. If you find yourself embarking on a new Network planners are advised to keep the Installing Category 6 or higher Category network infrastructure project later this latest standards for cabling and PoE in mind cabling at your earliest opportunity, then, year, keep in mind the benefits of Category 6 as they plan their new environments. should future-proof your cabling plant for cabling to support gigabit speeds and the Depending on timing, it may be desirable to some time to come. availability of 802.3at power sourcing install higher performing cabling and PoE + That being said, another somewhat thorny equipment as you make your equipment capable equipment to ensure having the consideration as you are building out your and cabling decisions. gigabit-speed cabling and power support unified wired/wireless infrastructure is device in place to keep your company covered for Using 802.3at-powered equipment allows requirements for power. The Power over many years to come. nearly every type of wireless AP to operate at Ethernet (PoE) standard today, IEEE 802.3af, its maximum performance levels without * In controller-based Wi-Fi networks is widely deployed. It powers most Wi-Fi and having to make any tradeoffs in terms of cabled devices requiring up to 12.95 Watts performance or feature support. sustained over Ethernet’s 100-meter limit across Category 3-and-higher Category Conclusion copper wiring. Planning the wired and wireless network Be sure to check the requirements of the infrastructure cabling together can lower Wi-Fi equipment vendor you use, particularly overall cabling project costs by 2 to 4 times. if you decide to deploy 802.11n. To take Companies realize these savings largely by advantage of all the enhancements to the avoiding “after the fact” cable pulls that might 802.11 standard for improved throughput, require breaking open ceilings and walls and coverage, and interference avoidance, some having to purchase extra cable in smaller 802.11n systems require more power than volume at a higher price. PoE can provide. Belden Technical Support 1 .800 .BELDEN .1 Wired-Wireless WP 2009 6 © Copyright 2009, Belden Inc.