Wireless LAN Roadmap

Wireless LANs were installed in 2003 using consumer-level 802.11b access points in the Middle School to support a “mobile lab” of notebook computers due to a lack of traditional labs. Wireless implementation has been fraught with difficulties due to unique needs of schools:

1. high density of computers in a single area;
2. all computers being booted and logging in simultaneously;
3. roaming profiles and other login-related traffic saturating available wireless bandwidth.

In 2006, the consumer-level access points were replaced with an enterprise-level managed wireless network. This alleviated some issues, but not all. The main problem is the large bandwidth needed by a full classroom of notebook computers logging in simultaneously. The theoretical I/O of 802.11g is 54Mbps shared, but real-world bandwidth is closer to 30Mbps. Shared among 20 notebooks, each gets only 1.5Mbps. Compared to a wired 100Mbps connection, this is obviously about 60 times slower. Because the 802.11b/g network has only three non-overlapping channels (1, 6, 11), there is a maximum of three access points servicing a given area; more will cause signal interference. Regardless of changes made to the wireless LAN, this is a fundamental problem.

The next wireless standard, 802.11n, was ratified in November 2008. It offers not only increased speed and range for 802.11n clients (many of which are shipping with draft specification hardware now), but also an increase in performance for legacy 802.11g clients due to its MIMO capabilities.

The IT department has decided that deploying additional 802.11g infrastructure is not effective. All further wireless deployment is deferred until 802.11n access points are available.

Cisco (the manufacturer of our current switch infrastructure) has a prototype 802.11n access point based on the draft spec. Research indicates that improvements to the wired network will be needed to effectively deploy 802.11n access points. The IT department will prepare for 802.11n by completing the following action plan:

1. Identify best locations for APs and survey available power. New APs will require more power than previous standards.
2. Identify structural support for AP installation. Unlike earlier APs, the 802.11n models house multiple radios and are therefore too heavy (11 lbs.) to simply hang from a drop ceiling.
3. Install 1000BaseT copper SFPs in network switches to provide gigabit connections to 802.11n APs (needed because the APs  will exceed 100BaseT throughput back to the switch).

Here's our current timeline:

• Pilot of either Cisco or Aruba 802.11n network in English area of OHS.
• Phase 2 network infrastructure deployment spring 2009
• 802.11g managed APs deployed to elementary schools summer 2009
  
• 802.11n managed APs installed in RCI, OMS, OHS summer 2009
  
• All plans are dependent upon funding, which has not yet been approved.