Case Study: Dartmouth College adds video and voice to its Wi-Fi
Students get to talk to their library
By Tim Greene, Network World | Network World US | Published: 01:00, 04 March 2005
Dartmouth College in New Hampshire has embraced Wi-Fi for data so enthusiastically that the school's IT chief is leaping into running voice and video over it. The venture calls for tripling the number of access points on campus, swapping out old wireless gear for smarter equipment and partnering with a start-up that is still putting the finishing touches on its technology.
With video set to go into production in April, the college is beefing up its Wi-Fi network to support four channels of educational video, says Brad Noblet, director of technical services for the college. "We have a little over 600 access points today covering 150 buildings in a mile square. I'm going to come close to tripling that in order to increase the amount of bandwidth so I can deliver video and handle a number of concurrent VoIP telephone conversations."
The current Wi-Fi network, based on Cisco gear, is used primarily for e-mail, instant messaging and Web surfing, he says, but the school has greater needs.
Staff need video to be noticed
"A lot of the faculty feel like to capture the attention of their students, they have to do more than just stand there and talk," he says. That means adding video presentations as part of the curriculum.
Ideally that would mean student laptop access to audio, video and data in classrooms, but that would require an Ethernet jack at each desk, a huge infrastructure upgrade. "We want to take four channels for teaching and learning and make those available on wireless as well as wired so we can again have this mobile classroom effect," Noblet says. "You don't need a smart classroom." The new wireless gear will support existing data applications and Internet access.
The school has teamed up with Video Furnace, a start-up that multicasts video to laptops using client software agents downloaded to PCs when users select the encrypted videostreams they want. The company supports Macintosh, Linux and Windows operating systems, all of which are used on campus. In addition to supporting the educational streams, Video Furnace also will deliver commercial cable TV to the campus over Dartmouth's converged wired IP network, Noblet says.
Choosing 802.11a to make the best of bandwidth
Because each computer needs 400 kbit/s to 2 Mbit/s of bandwidth to screen video content (depending on screen size and resolution), efficient use of bandwidth is key.
Bandwidth for 802.11a is provided at 55 Mbit/s using its own radio frequency. 802.11b supports 11 Mbit/s, and 802.11g supports 55 Mbit/s, but 802.11b and 802.11g share the same frequency. If an 802.11b device associates with an access point, the access point drops down to 11 Mbit/s for 802.11g users as well.
That led Noblet to choose 802.11a. "I'm going to be able to get on the order of 20 to 25 streams per access point," he says.
Noblet is packing access points in high density for areas such as dorms that are likely to have large numbers of users, to ensure coverage during peak times. He is swapping out Cisco access points for Aruba Wireless Networks access points because Aruba supports intelligent switching. "Cisco was not in that game" when he started the project, he says (it has bought Aruba rival Airespace since then) .
Intelligent load-balancing by the switch
The intelligence he wants includes Aruba wireless switches' ability to load balance requests from laptops. In an area with overlapping access points, the switches send messages that force laptops to less-busy access points to maximise the number of users associated with the wireless network.
The switches also adjust power of access point transmissions to maximise the area in which wireless devices can get a signal.
The intelligent switches, in combination with mapping tools, also make it easier to install access points effectively. "The wireless switch can force access points to signal one another so they can get an indication of who can hear who and develop a coverage map that gets plotted graphically on a screen," Noblet says. Using that map, technicians installing access points can see where more access points are needed. "When we put up the original 600 access points, it damn near killed us to do it manually," he says.
Relating Wi-Fi to floorplans
The tool plots Wi-Fi coverage on architectural drawings of buildings. "So I can see how's my coverage in this given building and be able to pinpoint where I need to move an access point or maybe I need to add an additional access point," he says.
Noblet spent a lot of time with Aruba developing location-sensing tools to go along with the switches. Now the switches can tell him the rough location of a wireless device associated with the network, and this can help run the campus more efficiently.
For instance, a student on an unstaffed floor of the library who is wearing a VoIP communicator badge made by Vocera could ask, "Where are the Shakespeare folios located?" Voice recognition software would translate the question and deliver an automated voice response to tell the student where the folios are in relation to where the questioner is standing.
Similarly, students with laptops in a lab could query a server how to use the piece of lab gear sitting in front of them, and the server could respond with a Web page containing a user manual.
And more VoIP too
The video project should also increase use of VoIP over Wi-Fi. Most Wi-Fi VoIP phones employ 802.11b, which supports only eight concurrent VoIP calls. More access points means support for more VoIP, Noblet says, which should help accelerate the college's migration to VoIP. So far about 4,000 of 7,000 phone lines have been converted to VoIP, but only a few hundred of those today are W-Fi, he says.