Typical WLAN Environments
WLANs have been around for more than a decade now, but their use in many different environments is just beginning to take off. As mentioned in Chapter 1, "Defining a Wireless Network's Protocols and Components," the initial widespread use of wireless was for bar coding and data acquisition. However, with the diverse universe where WLANs are now being deployed, many different factors need to be identified. The following lists some of the unique requirements of the most common environments: High bandwidth per user (office application, engineering departments) Maximum range (retail, warehousing) Extremely fast roaming times between access points (voice, video, time-sensitive applications) High level of security (health care, government, finance) Easily accessible by anyone (public WLANs)
Before you can determine the technology that will work for your system, review the requirements for your particular environment and application. Following that, a preliminary network design and site survey will help to determine whether that technology is right for your site. For every type of installation, you need to analyze several key items. The topic of bandwidth has been discussed many times already in this book, and this is not the last time it will be mentioned. Adequate bandwidth per user is critical to a successful WLAN. This means making some decisions about the density of users per access point (AP) and the 802.11 technology used. Determining what level of roaming is required for the applications can also be critical to a successful WLAN deployment. Now is the time to determine whether a fast roaming scheme (an extremely fast handoff when moving from one AP to another) is required to prevent problems in the applications. It is also critical to understand at what layer the roams will be occurring (Layer 2 or Layer 3 MAC and transport layers of the OSI model). This will be based upon the necessity of the users to access the network while they are in motion, and at what network layer the application is running. This requirement for voice over the wireless, which requires a very fast handoff, may impact the roaming requirement as well. The next sections outline WLAN considerations in many common WLAN markets, including retail, enterprise, health care, education, manufacturing, hospitality, public, and small office/home office (SOHO) locations. Retail/Bar Coding
Because the bar coding arena was the first widespread application for wireless, this discussion starts with traditional requirements for retail and warehousing, and includes what some users are doing with wireless today. Typically, in both retail and warehousing, there are a limited number of users, with limited requirements for bandwidth. In these environments, however, there tends to be a need to cover a large amount of area and to keep the cost per square foot of coverage to a minimum. These basic requirements are changing at some retail and warehouse facilities. Retail
There are several types of retail applications and environments. This section starts by discussing the applications used in the typical retail, large-scale store (that is, a superstore). In the superstore, applications will undoubtedly include inventory control, price shelf auditing, and printing. These applications generally use short packets and require minimum bandwidth. Running at even the lowest 802.11b setting of 1 Mbps provides more than enough speed for the typical number of users on the system. Figure 4-1 shows several popular bar code scanner styles used in a wide variety of applications. Hundreds of different models and types are available today, with many of them supporting WLAN systems. Figure 4-1. Typical Portable Bar Code Scanning DevicesAlong with portable bar code scanners, many large retail outfits provide a "price-verifier" scanning device for customers to check and verify the price of products. These devices are located around the facility, and can be found in standalone kiosks or mounted to the end of a shelf or even to building pillars and walls. Again, these devices require minimum bandwidth; however, their placement is sometimes not optimum. Although mounting the device to a shelf or a building support pillar is easy from the mounting aspect, because these mounting structures are typically steel construction, they tend to block the RF coverage to some degree. A third application where wireless is used in many retail locations is the point-of-sale (POS) device, or cash register. In some cases, the POS devices may be a self-checkout scanner, as shown in Figure 4-2, or even a customer kiosk where coupons are printed. By having the POS device wireless, it enables the placement of the devices at any location in the store where AC power is located, eliminating the need to pull new network cable. This makes rearrangements of a store easy, and proves especially helpful in times of heavy traffic such as the holidays and special store sales. Although the POS device is transacting bar code data, it also must be able to handle transactions for the final sale. Most POS devices will actually download a new product file at given times (usually when the location is closed for business), keeping the pricing and inventory data local. This particular download can be a very large file, and therefore requires a fair amount of bandwidth to complete in a reasonable time. 802.11b tends to provide more than enough bandwidth for such applications. Figure 4-2. Typical POS Terminalfast roaming capabilities, the use of voice will force this to become a requirement. But do not forget about future applications that will be used in retail locations. Some stores have already experimented with providing terminals mounted on shopping carts that enable shoppers to browse the Internet while cruising the store. This Internet access will require another piece of that same bandwidth as the store, but will also need to be segmented from the store traffic (another use for VLANs). In summary, remember the following considerations regarding WLAN usage in retail environments: Bar coding Typically, applications using bar code scanners have a very minimal set of requirements, with range and coverage being the most often sought-after feature of the wireless. Low bandwidth Low user density Maximum coverage for lowest implementation cost Voice Minimum number of users, but requires minimal dead spots in facility. Roaming Usually a single network segment of Layer 2 roaming is adequate. If voice is used, fast roaming is recommended. Security Depends on data being passed over WLAN devices. If POS devices are used on the WLAN, a high level of security is recommended, such as Wi-Fi Protected Access (WPA). Warehousing
Although bar coding is a primary application in warehousing as well, warehousing lends itself to other applications and a slightly different implementation of the bar code scanner. Most warehouses use lift trucks or tow motor vehicles, which move around the facility at a much higher pace than people on foot. This requires quick handoff between APs, but nowhere near the handoff requirement for voice roaming (150 ms). It also means the scanner device must be mounted to the vehicle. This can create some obstacles for the antennas. You must also consider the composition of the items being warehoused. For example, liquid items can be very radio opaque, and metal items can significantly affect the propagation of signals. These items may change in a warehouse as inventory levels change, or worse, not be present at the time of initial survey. Figure 4-3 shows one typical lift-truck terminal. This style of device is typically ruggedized, with large screens and large keys for easy accessibility while operating the vehicle. Figure 4-3. Typical Lift-Truck MountingFigure 4-3 also shows a typical mounting of a lift-truck terminal. The antenna is most often located up high for maximum coverage. In some cases, this is accomplished by mounting the entire device high (as shown in this figure) or by running coax cable to a remote antenna. Because of the nature of vehicle mobility, many users think fast roaming is required when using bar code scanners onboard a lift truck. However, as with simple bar code scanners and IP applications, this is not a necessity for most systems. It is, however, still a requirement for voice systems to have fast roaming implemented. In summary, remember the following considerations for typical WLAN usage in warehouse environments: Bar coding Similar to handheld bar code scanners, the lift-truck bar code scanners have similar requirements. Low bandwidth Low user density Maximum coverage for lowest implementation cost Voice Minimum number of users, but requires minimal dead spots in facility. Roaming Usually single network segment, of Layer 2 roaming is adequate. Tow roaming (even if vehicle is in motion. However, if voice is used, fast roaming is recommended. Security Depends on data being passed over WLAN devices and how critical its overall nature is. If the warehouse stores fresh foods, it may not be necessary at all. If the warehouse processes military materials, however, it may be a high-priority requirement. Enterprise Offices
The enterprise office is one the most recent places were wireless is starting to take a strong foothold. Although many people use wireless networks in offices, many others do not see the benefit of it and view wireless as just a workplace toy. This is especially true of users who are accustomed to a desktop PC and for whom mobility is not a possibility. As more users move to laptops, and portability is available, however, the use of wireless will take off. The ability to have information at your fingertips anywhere in the facility is extremely beneficial to both the user and the company. Typical applications for enterprise offices include general network use such as e-mail, Internet browsing, and file transfers. However, many applications such as intercompany instant messaging applications are starting to be used in the enterprise and require network connections throughout office. A well-disciplined and well-used instant messaging program can be an extremely useful tool. Consider this: You are attending a meeting and you need some bit of information that you do not have, but you know someone in your organization does have the information. You have three choices: Leave the meeting and go find that person. But this requires that you know precisely where that person is. Call the person, hoping he has his cellular phone turned on and he is not in a meeting that precludes him from answering the phone. Use an instant messaging application. You can ask the question and get the information without ever leaving the meeting room or disturbing anyone else in the meeting. Think about how much time that saved for everyone in the meeting!
A second application is 802.11 phones (see Figure 4-4). We all understand that the use of a cell phone, which is with you all the time, also dramatically increases your availability to coworkers. But the use of an 802.11 VoIP phone means you do not need to spend the extra expense of cellular airtime when inside your facility. Figure 4-4. Typical 802.11 Wireless PhonesBoth the instant messaging and 802.11 applications require connection at all times to the network; otherwise, they are not effective. Although instant messaging can withstand some interruptions (you normally will not be using your computer while walking from one location to another), a wireless VoIP phone requires not only constant connections, but also the ability to roam from one AP to another very fast (under 150 ms). That may mean maintaining the same subnet connection, which can have a huge effect on your network's design because it requires a large "flat" network, with many users on the same subnet. Although some Layer 3 roaming products are available, many are not fast enough to meet the necessary 150-ms roaming requirements needed for VoIP. They are, however, getting faster all the time. Be sure to specify fast roaming as a necessity if you require it for your design. Wireless VoIP also requires a bit more bandwidth, and has less tolerance to bandwidth congestion than regular data applications. For this reason, it may be necessary to limit the minimum data rate. Also most of the wireless VoIP products available at the time of writing are limited to 802.11b, with several companies' road maps including 802.11g and 802.1a products sometime in 2004 or 2005. In summary, remember the following considerations regarding WLAN usage in enterprise environments: Cell sizes Typically small for maximum per-user bandwidth. Voice Simultaneous calls can create a large bandwidth requirement. As mentioned previously, separate VLANs are recommended here, and care should be taken to keep dead spots in the facility to a minimum. Roaming Layer 2 roaming may be adequate, but Layer 3 roaming is often necessary. Fast roaming is required in most cases. Security A high level of security is recommended (WPA). Health Care
The health-care industry has experienced a surge of wireless usage over the past few years. Although several leading-edge health-care providers were actually using wireless many years ago, wireless has become mainstream only in the past few years. The scope of applications in health care is as wide as in any segment of the wireless industry. The initial usage of wireless was for medication distribution. The ability to have instant access to a patient's records enabled clinicians to view the last dosage and time, and to immediately update the patient's records when meds were administered, providing up-to-the-minute record keeping. This has been instrumental in reducing medication errors. This application requires minimal bandwidth because it is a simple database update, but it requires coverage in all areas where patients will be administered medication. Another early application was the use of wireless to connect patient monitors (devices that electronically monitor respiratory, heart, and vital statistics) to monitors at a centralized station such as ward or wing desk. This permits one health-care professional to monitor many patients simultaneously. This also enables health-care workers to monitor patient vitals not only while in the room but also as patients are moved to another location for testing, while in transit between departments, and so on. Once again, this requires only a minimum amount of bandwidth, but does require wireless connection access anywhere that a patient may be located. Chapter 3, "Regulating the Use of 802.11 WLANs," Health Insurance Portability and Accountability Act (HIPAA) regulations require all patient data to remain strictly confidential. So if there is any possibility that the data over the RF may be intercepted and decoded, the system cannot be used for patient data. Several other new wireless VoIP applications are entering the market today. One of the forerunners in these applications is Vocera (see Figure 4-5). The Vocera Communications Badge is reminiscent of the Star Trek communicator. It is a wearable device that weighs less than 2 ounces and can easily be clipped to a shirt pocket or worn on a lanyard. It enables instant two-way voice conversation without the need to remember a phone number or manipulate a handset. The communicator is controlled using natural spoken language. To initiate a conversation with Dr. John and LPN McMannon, for example, the user would simply say, "Get me Dr. John and Nurse McMannon." In addition, when a live conversation is not necessary, text messages and alerts can be sent to the LCD screen on the Communications Badge. Figure 4-5. Vocera CommunicatorExtensible Authentication Protocol [EAP]). Education
Education facilities vary in size and format. Today's colleges are reacting fast to the demand for wireless networks. Just like every other industry, secondary education is a competitive business. The ability to provide students with learning and teaching aids is an advantage. Wireless on the campus provides network connectivity in most locations to students and provides teaching professionals with yet another tool to disseminate information, including class updates and assignments. A fast-growing technology moving across colleges is the virtual class, or online class. Many universities are using online classes to provide lower-level classes or optional classes, and the ability to do it wirelessly means students can have access to these classes from locations outside the traditional classroom or computer lab, providing yet another competitive edge for the university and another advantage for the student. Many classes today can be quite large, with sometimes as many as 300 students in a basic English or history class. Trying to provide enough bandwidth in such a classroom can be a challenge. The requirements of the students in the classroom need to be analyzed. They can be much different from perhaps a class specializing in video editing, in which video files are being transferred up and down the network. Also the outdoor areas of the campus, or green spaces as they are called, are areas most students want to have wireless coverage (see Figure 4-6). Such coverage enables students to sit on campus lawns and in parks and access the network for work and research, or just to browse the Internet. However, covering these outdoor areas can be difficult, as well as expensive. The cost versus advantage should be analyzed here. Also when covering outdoor areas, you need to be certain coverage in the building structures isn't interfered with. Outdoor coverage should be thought of as part of the indoor system, not as just an "add-on" network. Figure 4-6. College Green SpacesAnother issue that affects education (as well as other public systems) is the content being downloaded from the Internet. When a large number of users are downloading MP3 or video files, or using the Internet to receive radio and TV broadcasts, the network can easily become saturated. Certain protocols may need to be filtered at the router, or at the very least, the AP. The final major hurdle from an education-use perspective is the hardware. The main staple for wireless today is 802.11b. And it comes in many flavors from many vendors. Whatever radio is in the computer the student got for Christmas, or whatever 802.11b card that is the cheapest at the book store, is what will be used. This means any requirements for proprietary systems (such as security) are simply not feasible. You might need to specify certain requirements for the students who want to access the wireless network. The first and most common requirement is the use of Wi-Fi certified devices only. You also want to specify what technology is to be used. Likely, you will require 802.11b or 802.11g devices, because either type can communicate in an 802.11b or 802.11g infrastructure. The infrastructure, however, will most likely need to support 802.11b devices (meaning it could be either b or g). The use of 802.11a systems could be an advantage; however, using 802.11a exclusively on a campus severely restricts students today from using most of what is on the market for WLAN devices. VLANs are another feature often implemented in educational environments. Many facilities use VLAN technology to separate students from faculty and staff. This helps to protect the facility's internal administrative systems from mischievous students and possibly from any viruses or worms students might introduce into the system. In summary, remember the following considerations regarding WLAN usage in education environments: Cell sizes Typically small for maximum per-user bandwidth. Voice Usually limited applications, possible for faculty use only. Roaming Layer 2 roaming may be adequate, but Layer 3 roaming is often necessary. Security Over-the-air security is optional. You might want network authentication to prevent nonstudents from accessing the network. VLANs Virtual LANs should be used to separate and protect the facility's internal networks from the student population and outsiders. Manufacturing
Manufacturing facilities have very unique requirements that vary quite widely. A critical look at the application is required to understand the bandwidth required and the user density. In most manufacturing environments, user density is not a big issue; however, bandwidth can vary. In some cases, wireless networks are used more for tracking products through manufacturing (using bar code applications) and require minimal bandwidth. In other cases, however, there may be a need to download inspection documents, specifications, and other large files; such downloading requires maximum bandwidth capability. Another common application in manufacturing and in industrial warehousing is machine automation. WLANs are used to feed control information to an automated crane, railcar, or any other remote-control device. With such, the device can move under remote control, without the need for wiring between the operator and vehicle or device (see Figure 4-7). Of course, the concern here is loss of communication. What happens when that crane is moving with 20 tons of steel and it loses its network connection? (And do not think it has not happened!) Figure 4-7. Remote Steel CraneFor industrial and manufacturing, it is very critical to review the requirements of connectivity, roaming (and roaming times), and bandwidth because applications vary widely. In summary, remember the following considerations regarding WLAN usage in manufacturing environments: User density Low user density, maximum coverage. Voice Usually limited applications. Roaming Layer 2 roaming generally suffices. Security Depends on data being passed over WLAN devices. Hotel, Conventions, and Hospitality
dual band to provide users who have 802.11a with access as well, freeing up some of the 2.4-GHz bandwidth. Normally, small cells and a higher number of APs are required for convention and meeting room areas. In summary, remember the following considerations regarding typical WLAN usage in hotels, convention centers, and hospitality areas: authentication server may be used to limit access to approved guests. (Guests are urged to use virtual private networks [VPNs] over wireless.) Public Hotspots
Sipping coffee, waiting for your flight, or having fries with a Quarter Pounder now means having access to the Internet. As more and more people depend on staying connected, and staying connected means keeping people longer in your establishment, wireless Internet access becomes a requirement. There are two main types of installation for such: The very local coverage area, such as a coffee shop or fast-food chain restaurant, where typically one or (at most) two APs are needed to provide coverage. A widespread coverage area such as an airport or park, where 10 or even hundreds of APs are necessary to provide full coverage.
Generally, these systems are used for one purpose: connecting to the Internet, with limited expectations for high bandwidth. The overall number of users who use these networks, while growing quickly, is still a small number of the total number of people at these locations. These public systems must follow the same rules as other locations where there is no control over the client device. A public system must allow almost any WLAN vendor's device to communicate, and installers should consider using an 802.11g or even a dual-band AP to provide the widest range of support for the users. Bandwidth Low to medium for most sites. User density Low for most sites, with expectations to grow. Roaming Small sites require no roaming. Larger sites may require minimal roaming support. Security Typically no WLAN security is set up. A network authentication server may be used to limit access to approved guests or to charge guests for access. VLANs Virtual LANs should be used to separate internal networks, conference networks, and guest networks. SOHO
Small office/home office (SOHO) environments do not usually require a site survey (unless, of course, your home is the size of a palace). SOHO sites usually require only a single AP and have a limited number of users accessing the network. Overall throughput is normally limited by the Internet connection. The choice of wireless vendors is usually controlled, and so technology choice is not a problem and any 802.11 scheme will work. Many SOHO users think security is not a problem. This, however, is probably the single biggest misconception regarding SOHO implementations. These environments should have at least minimal security, and it is recommended to at least use WPA with Pre-Shared Keys (PSK) and to require users to change passwords at periodic intervals (every month, every week, and so on). Another problem that occurs with SOHO installation is interference. Although most education and enterprise offices use 802.11 VoIP phones for wireless phones, or use proprietary 900-MHz wireless corporate phone systems, in the SOHO, it is common to use a standard home-style 2.4-GHz or 5-GHz wireless phone. These phones will cause interference if installed improperly. In addition to phones, many types of wireless devices can be sources of interference. For example, wireless baby monitors, cordless speakers, and wireless cameras are common users of the 2.4-GHz band. Almost any device that is "cordless" is a potential source of interference, and such devices should be reviewed to determine whether they operate in the same frequency band as the intended WLAN system. Even the standard microwave oven operates at the 2.4-GHz frequency and will cause interference to most 802.11b and 802.11g WLAN systems. In general, a minimum of 10 feet should separate the WLAN and the potentially interfering device. However, the best solution is to choose a phone, camera, and so on that uses a different frequency band than the WLAN and to keep any WLAN device at least 10 feet away from any microwave oven. In summary, remember the following considerations regarding typical WLAN usage in SOHO environments: Bandwidth Low (limited by incoming network pipe). Security At least minimal WLAN security is set up (WPA). Suggest a firewall if using public Internet access.
|