Apr 14 2009

Wireless for One-to-One

Student computer programs require some unique considerations when rolling out a wireless network.

Anyone who works in the IT department at a school district knows that your operations are different than your corporate counterparts. But those who are involved in one-to-one programs often find yourselves facing different issues than your corporate or educational brethren. One area where you differ is how you architect your wireless networks. The following are some suggestions for designing or re-designing your wireless network, keeping one-to-one notebook programs in mind.

Select Your Equipment

The first step when setting up your wireless network (WLAN) is deciding what equipment to use. You may not know how many access points or controllers you will need at this time, but you should determine that later when conducting the wireless site survey.

When shopping for wireless equipment, there are a few key features that you may want to keep in mind. The first is radio frequencies. When this article was written, the 802.11n standard had not been ratified, and it doesn’t look like it will happen in the near future. Keeping this in mind, you need to decide whether you want to purchase “pre-n” equipment that may or may not meet the standard when it is released.

Many manufacturers are guaranteeing the equipment will be "flash upgradeable" to the ratified standard, but make sure you can get those updates for no additional fees. It’s hard to go back to your superintendent or board of education six months after you purchase the WLAN and ask for money to upgrade it again.

If you decide to go with "n" equipment, you will certainly need a gigabit connection to each AP in order to provide the increased bandwidth that it will require. There is nothing wrong with purchasing wireless networking equipment that meets the current standards (802.11a, b and g), and upgrading some APs in a year or two when the standard has been ratified.

The second key feature that you will want to look for is a wireless controller that allows for one central point of management of your WLAN. Try to imagine needing to change a setting on your APs and having to change 50 of them one at a time. A controller can be a huge time savings, but it may cause a performance bottleneck on the network. Different controllers require different network architectures and are worth investigating. Wireless controllers from Trapeze Networks and Enterasys allow the APs to handle local switching and not route all traffic back to the controller (whereas some controllers route all traffic to the controller potentially causing a bottleneck). Lastly, when selecting your WLAN equipment, you will need to decide if you are going to provide outdoor access making your entire campus wireless.

Conducting Your Site Survey

Now that you have selected your equipment, you are ready to start your site survey. The site survey could be the single most important phase of your deployment. The purpose of the site survey is to determine coverage areas and locate dead spots in your building. Oftentimes a site survey will indicate areas where you may need to place additional access points, or areas where you can forego an access point or two. If you already have an existing WLAN, you may be able to improve your network by using some wireless analysis tools and examining your coverage area.

There are many different tools out there for analyzing a wireless network: both free and purchased. NetStumbler is an open-source product that many network administrators use when tracking down wireless issues. NetStumbler will allow you to see the different access points, the channels they are operating on and the signal strength that is being observed.

Fluke Networks has an entire line of products designed to help you troubleshoot or design your wireless infrastructure. The InterpretAir software from Fluke Networks is a site survey software that you can use to map your network, as well a determine coverage areas based on the WLAN equipment you are using. Trapeze Networks has a site survey tool that can tell you exactly where to place your APs after you run through a wizard that asks you about your building construction and user locations.

If you opt to go the professional route for your site survey, be sure to get references from other sites they have been surveyed, and see how those networks are performing. Performing a site survey is crucial to your network’s performance and shouldn’t be skipped. There is a possibility that you could cut the costs for your network by having a professional site survey conducted.

Capacity Planning

When setting up your WLAN for a one-to-one environment, keep in mind the number of users who may be accessing that AP at any one time. The beginning of the school day may be the busiest time of day for the network for many schools as students are getting online to submit homework, check e-mail and catch up with their friends. Many WLAN access points claim to support a theoretical maximum of 256 clients, but real-world performance is about 10 percent or 25 clients. Networks that experience slow performance are most likely suffering from not enough APs but may offer plenty of coverage area. By having a higher concentration of APs, in the event of a failure, other APs may pick up the slack and increase their broadcast levels to accommodate for the outage. A higher concentration of APs will allow the network administrator to restart an AP in the event of a malfunctioning unit.

Encryption and Authentication

There are currently two main types of encryption used on WLANs presently: WEP and WPA. WEP encryption is substantially weaker than WPA but, depending on what kind of data you are trying to protect, it still may be a good fit. If you are using WEP to encrypt student data, you may be fine. However, staff members who may be accessing your SIS or online gradebook application may benefit from the added strength of WPA encryption.

WPA encryption is much stronger and can be managed with randomly changing keys, via the 802.11x standard. Each time a notebook changes APs, it has to re-authenticate against the system, which in the case of 802.11x has to hit your RADIUS or authentication servers and may cause logon delays. If you determine that you are going to go with 802.11x, you may need to add additional logon servers and/or RADIUS servers to handle the authentication and keep the rest of your network performing adequately. This is a key point where one-to-one programs differ from other educational environments, or even corporate environments. In the corporate world, users aren’t getting up every 45 minutes and moving to another part of the building with the need to re-authenticate.

Fail-over and Redundancy

One of your last steps is to determine how much redundancy or fail-over you will need. Consider purchasing multiple wireless controllers so that if one of them has a problem or needs to be rebooted during the school day then interruptions are kept to a minimum. Check to see whether the APs can have a “master” and a “slave” controller so they will automatically switch over to the controller that is online. As mentioned earlier, having a strong concentration of APs will allow for them to be rebooted if necessary while still providing service to your users.

Installing or upgrading a wireless network is a major investment in your infrastructure and shouldn’t be taken lightly. Proper planning, equipment selection and proper implementation will ultimately determine the success or failure of your WLAN. When in doubt, ask other schools what equipment they are using and how satisfied they are. Taking a short trip to see a WLAN system in action may be the best way to help narrow down your choices.