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Wireless LANs can avoid the cost of pulling cables and installing wall jacks for each client. They can improve workspace flexibility by providing connectivity wherever you need it instead of only where jacks have been installed. Most laptops now ship with both Ethernet and Wi-Fi onboard, so going all-wireless won't add client-side hardware cost.
On the other hand, WLAN APs can be more expensive than Ethernet edge switches for the same number of users. You will need to invest in a site survey to place APs where they can deliver adequate coverage and capacity. WLAN controllers that adjust channel assignment and power output will cost more initially, but will pay for themselves over time by automatically responding to RF changes so that you don't have to.
You'll need to decide whether to use Ethernet or wireless backhaul to connect APs to your core network. Going "all wireless" is a bit of an overstatement, because you will still use Ethernet to some degree. For example, you will use Ethernet to connect WLAN controllers to each other and to infrastructure devices like routers, firewalls, authentication servers, DHCP servers, and user directories. You may also decide to keep mission-critical application servers and high-demand resources like file shares and printers on wired segments to avoid creating performance bottlenecks and ensure availability.
This brings us to the biggest concerns that companies have about depending on wireless: capacity, quality of service, and availability.
- With only three non-overlapping 2.4 GHz channels, you might need to deploy a 5 GHz WLAN to deliver sufficient capacity. You can do that with 802.11a or draft 802.11n today, but should plan to migrate to standard 802.11n once it becomes available.
- Best effort applications like email and web raise fewer concerns, but you will need QoS controls (e.g., WMM) if you plan to run mission-critical applications over wireless -- particularly latency-sensitive or bandwidth-intensive applications like VoIP or video.
- All WLANs use unlicensed spectrum, which leaves them vulnerable to RF interference. Look for WLAN products that are inherently more resilient to interference, and create a fallback plan for what you will do during in the event that interference cannot be eliminated.
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