Faculty Directions, Spring 2006 - A Cable I'll Keep
Chuck Heck
CCIT
We're all hopelessly addicted to anything wireless. So much so that one of the first things we do with all of our electronic do-dads is attempt to eliminate any wires that may be involved. Case in point: Do you know anyone that uses a wireless earphone with their cell phone? It's not enough to use a phone, untethered from the phone line. Now we have to have a wireless "hands free device" so as we meet people on the street they won't be able to tell if we're on the phone, or simply a bit off center.
Wireless is a big thing when it comes to computers, too. The University has an extensive wireless network for laptops, and many of us have wireless networks at home. The advent of the tablet PC has users of those devices looking for a way to cut the video cord that keeps them tethered to lecterns and wall panels in Technology Enhanced Classrooms - and still be able to display their video for the class.
Let's take a look at why you can't shed that clunky VGA cable at the moment. Some manufacturers sell "wireless" projectors. The main selling point is one of convenience. A presenter can walk into a conference room, plug a projector into wall power, fire up a laptop, and deliver a presentation, generally PowerPoint, with a minimum amount of effort. When finished, turn off everything, pick up and leave with a minimum amount fuss. Another application is a collaborative meeting. Some projectors can support multiple feeds and act as a hub when more than one person needs to present to the group. In each of these examples, the presenters, either solo or in the group, would have the software necessary loaded on their laptops to manage these connections, and each would know how to use it. Without the software, there would be no communication with the projector. Distribution and training would be an issue if every laptop on campus needed the software. Visitors from off campus wouldn't be able to present on campus without the software, and likely wouldn't arrive with it. Wireless projectors have met with mixed success in the market place. NEC has wireless units, while InFocus has dropped the wireless adapter that has been part of their product line.
Let's take software out of the mix and look at the current breed of wireless networks. These run at advertised speeds of 11 megabits per second (mbps) (802.11b) or 54 mbps (802.11a/g). Actual speeds are much less, with 802.11b having a throughput of about 5mbps, 802.11g 25mbps if there is no 802.11b traffic (in which case it falls back to 802.11b speeds), and 802.11a 25mbps. As a shared connection, you don't get the full amount of available bandwidth if someone else is using the connection at the same time you are, and you never know if someone is. The more people are sharing a connection, the less bandwidth each has, which has a direct impact on sending video to a projector. In a recent test at Syracuse University of a Linksys WPG54G Wireless-G Presentation Player, under lab conditions, a PowerPoint presentation managed a 1 mbps average throughput, and a full screen movie came close to a 4 mbps average, but with unacceptable jitter. Insufficient bandwidth was the problem. Add to this the fact that wireless video adapters today allow you to have a wireless video connection, or a traditional "surf the net" connection, but not both simultaneously. So in today's wireless environment you start out with a connection that is less than adequate under ideal conditions, and only goes downhill when taken into a large classroom with laptops, wireless access and high levels of shared access activity. This has been the experience of tablet PC users on campus.
We need also consider the trade off of convenience and security. There are issues of setting up laptops to run in ad hoc rather than enterprise mode. Ad hoc mode allows devices to talk directly with each other, without having to use the University wireless network, and is the favored method of transmitting wireless video. When closing down a wireless adhoc connection, it's important to reset the connection to enterprise mode. The software Panasonic uses does this. Others don't. During its test of the Linksys product mentioned above, Syracuse discovered that any PC within range of the Presentation Player that had the player software installed could hijack a presentation. This likely isn't a problem in small groups, but in a large lecture hall the potential exists for unwanted content to make its way to the screen.
So, can wireless projection be used successfully? Sure. It is used off campus where permanently installed technology isn't available, and the campus wireless network doesn't interfere. The content delivered is mostly PowerPoint slides.
What does the future hold? At the present time the next generation of wireless networking is under development. Referred to as 802.11n, it promises to quadruple the speed of current a and g networks and perhaps solve the bandwidth issues we experience today. Of equal, or more importance, is solving the security issues that surround the current technology. With the solution of the bandwidth problem, demand for wireless projectors may increase. If that happens there will be market pressure to solve the security issues that are impeding sales. All of this is several years down the road, though.
Until then, I'm keeping my trusty, low tech, well understood, VGA cable.