Things to keep in mind when considering wireless:
Wireless networks make up a tremendous portion of today’s networks. We can help you decide what works best for you. We install both wired and wireless networks featuring equipment from Linksys, a Cisco company.
The term “WiFi” originally referred to the IEEE 802.11b standard, but now typically refers to all three approved standards: 802.11a, 802.11b, and 802.11g.
The distance and speeds that the three standards address are typical for office environments. Actual performance will vary tremendously based on number, type, and density of access points (APs), building construction, office layout stability, interference and reflection conditions, and many other factors.
802.11b is the lowest-cost alternative and supports reasonable distances; however, its performance drops off markedly with distance from the AP, and its cost is now only slightly lower than 802.11g, making 802.11g a better value. Like 802.11g, it uses the unregulated 2.4-GHz Industrial Scientific Medical (ISM) band, meaning it is prone to unpredictable interference problems (more about that later).
802.11a is faster than b and has less interference as it uses a regulated frequency range; however, it suffers from higher cost and short distance support, and it has much more difficulty penetrating obstacles. As an example, a car manufacturing plant in California was totally wired for 802.11a before it was discovered the APs would not penetrate the facility’s ceiling tiles. The user decided it was cheaper to go with 802.11g rather than replace the tiles.
802.11g is low-cost, high-speed, and backward compatible with 802.11b, but still has interference issues due to the ISM band it uses. Overall, it is the best value. Some manufacturers offer very low-cost 108-Mbit/sec cards that are effectively two 802.11g’s. This setup works, but the implementation is not ratified by the Institute of Electrical and Electronics Engineers (IEEE; www.ieee.org). The IEEE is working on 802.11n, which promises speeds in excess of 100 Mbits/sec. It expects to finalize the standard by 2007.
With all three approved standards, network bandwidth is shared in half duplex. Plus, speed always diminishes rapidly as you get farther away from the AP. Even in an ideal circumstance, it is rare to achieve even 10% of the performance of a simple 100Base-TX full-duplex copper port connection.
Why we want wireless:
If the performance of wireless local area networks (WLANs) is so mediocre, why are they so popular? In many cases, users do not need high bandwidth or performance to handle routine communications like e-mail and Internet browsing. Conditions favoring a wireless network include:
Overlay network for mobile and guest users;
Application-specific requirements, such as portable inventory readers in warehouses, mobile meal ordering carts in hospitals, and portable data-entry pads in factories;
Temporary network connections where high performance is not needed, such as political campaign headquarters, temporary audit teams, trade shows, charity events, and emergency operations centers;
Inability to pull cables or access space easily because of such limitations as lease restrictions, a building’s historical status, civil boundaries, or apartment dwellers.
It is clear wireless networks are ubiquitous, yet do not match wired communications for performance, distance, or security. So, how do we analyze whether and to what extent wireless might replace horizontal copper cabling?
In the end, it comes down to distance, performance, security, and economics. Let’s look at wireless’s challenges to matching a copper connection in these areas and try to predict what’s likely to occur.
Distance. TIA/EIA-568-B-compliant structured cabling easily supports full-duplex Gigabit Ethernet traffic on links up to 100 meters in total length. Buildings are designed with wiring rooms to accommodate that distance. How does wireless fit in? As mentioned earlier, a typical 802.11g AP might have an effective reach of 40 meters in an office environment (your mileage may vary); however, there’s no law against installing more than one AP. With a judicious site survey and multiple APs, you can easily cover any conceivable office space-just don’t count on doing it with one AP, unless you have a very small office. While a single copper run can go farther in an office environment, even with dense AP deployment, you’ll have fewer copper runs; so, distance isn’t a real advantage either way.
Performance. Ubiquitous Category 5e cabling supports full-duplex Gigabit Ethernet. Here, there is no contest. The performance of a wireless network is highly variable, and can depend on whether you selected a, b, or g; the AP density; the number of users; and other factors mentioned earlier. Another key difference is that wireless data is shared half-duplex.
Let’s look at an example. Assume your office has an overlayed WiFi network running 802.11b. There may be up to 20 users sharing a particular AP, roaming up to 75 feet away from the AP. You’re at your desk, plugged into the wall outlet connected to a 100-Mbit/sec Fast Ethernet switch. You are enjoying 100 Mbits of personal, full-duplex bandwidth. You then unplug your laptop and carry it into a meeting room where you use wireless to access the company LAN. Given the conditions above, you might have a 5-Mbit/sec data rate (although 1 or 2 Mbits/sec would not be unusual), divided by 20 simultaneous users, in half-duplex mode.
So, in this example the wired LAN connection delivers 800 times higher performance than the wireless LAN. Even if you cut the number of users by a factor of 10 and upgraded to 802.11g, the difference is still staggering-and that is assuming your copper runners are not 10 times faster through connection to a Gigabit Ethernet switch, which is quickly becoming commonplace.
What else can we say about the relative performance? For one thing, the wired LAN is far more likely to maintain robust performance. You can be assured the copper cabling will deliver high bandwidth 24/7. The WiFi network is another proposition. WiFi is affected by multipath interference, neighboring wireless LANs, noise interference, other devices operating in the ISM band, and even the number and location of people in the building. The 2.4 GHZ used by 802.11b and g creates a wavelength that coincidentally happens to match almost exactly the common 4-inch construction nail, so sources of interference, reflection, and absorption are everywhere.
How much can performance vary? Here are a couple of actual examples. A WLAN in a warehouse was experiencing intermittent operation. Subsequent investigation revealed the amount and nature of inventory on the shelves (cans of pet food in this case) created variable signal attenuation between the AP and the mobile users. In another example, an office WLAN’s performance often dropped in the afternoon, but not every afternoon. After days of troubleshooting, the culprit was unmasked. It turned out that on sunny afternoons, the metallic blinds were twisted closed over the large windows, creating a strong multipath reflection that confused the APs and contributed to lower WLAN performance.
Upgrading from 802.11b to a, g, or n, or using dense AP deployment can improve performance. Both reduce the number of clients served per AP and decrease the users’ average distance from the AP, thereby increasing your typical connection rate. That said, the performance of WLANs is sufficient for e-mail and routine traffic for many users.
Security. There is no question that WLANs are a greater security risk than hard-wired LANs. By its very nature, a WLAN broadcasts traffic indiscriminately, and any suitable receiver can pick it up-even unintended ones. By now, everyone should know that the originally intended security scheme, Wired Equivalent Privacy (WEP), can be defeated easily by a determined intruder. WEP is still a reasonable method for home-based WiFi networks, but not suitable for the enterprise.
Much has been done with 802.11x, the IEEE standard for describing port-based access control, and WPA/WPA2 (WiFi Protected Access) to beef up encryption in the enterprise. Many companies offer methods of hardening access to uninvited users. With these additional measures, WLANs can become secure. But few things prevent a naοve user from attaching a $79 AP to a port at their desk and broadcasting in the clear. Wireless LAN network administrators need tools to quickly and effectively locate rogue APs and tightly manage security on their networks.
Economics. There is no such thing as a “wireless” LAN. Every AP is hard-wired to its associated switch. There are no wires from the AP to the laptops with which it communicates, but there are always wires. Just like in the frequent “copper-versus-fiber” comparisons you read, it’s easy to make one side or the other win depending on your objective. For that reason, we’re not going to go through the math here, but some of the financial considerations to take into account when contemplating WiFi versus copper include:
Number of users;
Users’ mobility needs;
Physical site design; permanence of facility;
Users’ performance needs;
Business applications/types of computing;
Security requirements;
Network reliability requirements;
Building restrictions, if any, on copper runs;
Cost of APs, site surveys, and wireless support;
Cost of running power to AP locations in ceilings or upper walls if you do not have Power over Ethernet (PoE)-enabled APs.
Hopefully, you will find this information helpful in your planning process for your home or office network. For more information on the wired and/or wireless networks, contact Kyawa today!
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