As enterprises expand their adoption of 802.11n wireless LAN technology, they will begin to exploit the technology's high bandwidth capabilities to deliver video over wireless LAN -- but that will mean engineering the conversion from multicast video to unicast.
Network engineers are spending their wireless budgets on 802.11n technology as never before. According to Gartner's most recent wireless LAN equipment market share report, 802.11n spending accounted for 45% of wireless equipment shipments in the third quarter of this year, up from 30% in the previous quarter.
Right now, the most common use of video over wireless networks is wireless video surveillance, DeBeasi said.
"That's pretty common because all you need is some power somewhere and a wireless connection and you're good to go," he said. "Less common is video training over wireless …. As the new [802.11n] technology permeates throughout enterprises, and as the technology gets faster and more reliable and secure, you'll see more applications loaded on top of it."
Liberty University in Lynchburg, Va., launched video over wireless LAN on its campus two months ago, using a new 802.11n network from Aruba Networks. The wireless network delivers satellite television programming via IPTV to students across the campus, according to IT director Jimmy Graham.
Switching from legacy Cisco to Aruba 802.11n wireless LAN
Liberty's wireless LAN, which was installed in late 2008, consists of 700 Aruba AP 125 access points spread out across the schools dorms, classrooms and public areas, Graham said. The network replaced a legacy Cisco wireless LAN composed of fat APs that had been haphazardly built out over the years as individual requests for wireless coverage came into the IT department. Graham said he considered buying his new WLAN from Cisco, but at the time Cisco's access points could not run with full features on a standard Power over Ethernet (PoE) infrastructure. (Cisco launched a standard PoE-compatible access point, the 2x3 MIMO Aironet 1140, not long after Liberty's Aruba network went live.)
Wireless LAN could mean nixing costly switches
For reasons beyond the convenience of mobility, the university was interested in offering pervasive wireless to students in order to pull back some of its network switches, which in turn would allow it to save money on power and upkeep. Currently every dorm on campus has two wired network drops. If the school's 11,000 or so students move toward accessing the network primarily through the wireless LAN, Graham could start pulling back some of his switches. He is planning to audit wireless usage this year to make that determination.
"If we see a 20% drop in usage, I can't see us pulling back switches, but if there's a 50% decrease, then I could see us pulling back half of our switches," he said.
But the leading barrier to getting students engaged in wireless was the school's IPTV system. Like most colleges, Liberty supplies television service to dorm residents, and since the dorms weren't wired for cable, the school chose to run satellite television via IPTV to students' rooms. Students accessed the IPTV via the Ethernet network drops in their rooms. The school wanted to enable its wireless LAN to carry the IPTV feed.
Prepping a network for video over wireless LAN: Supporting multicast video
The move to run video over a wireless network requires organizations to make certain engineering adjustments, depending on the type of application the organization plans to use, DeBeasi said. In some situations, the enterprise will need to engineer its network to support multicast to unicast conversion.
"If it's a live stream to multiple people, like a training video, and it's going to go to multiple people at the same time, then you need to have multicast support," DeBeasi said. "It needs to go from a server through the network and to, let's say, you and me and three other people. There's a challenge with wireless network in how they handle multicast."
Ruckus Wireless, a competitor to Aruba and Cisco, recently announced a new patent for an algorithm that helps its networks make intelligent decisions with multicast-to-unicast conversion. Other vendors, like Aruba, need to do some custom engineering to make this happen for their customers.
The problem with multicast video over wireless LAN is that users have a different quality of experience depending on their proximity to the nearest access point. The network can transmit the multicast video stream over the wireless LAN at a low packet rate to ensure that distant users have a good experience, but closer users will not. And if the multicast transmits at a high packet rate, the opposite will happen.
Some enterprises can solve this problem by translating multicast to unicast, sending out four, five or six streams of video over the wireless network at different rates, allowing endpoints to pick an optimal stream based on their location and network conditions. But this doesn't come without challenges. Once the network converts multicast to unicast, the number of packets going out over the network increases exponentially. An organization will most likely have to run this video over the 5 GHz channel on an 802.11n network, which has more channels available than the 2.4 GHz channel.
Graham worked with Aruba to engineer the network so that the wireless LAN controller would convert the IPTV multicast video to unicast streams, ensuring a good quality of experience for all students.
Graham is also using quality of service (QoS) features within his back-end wired network and his Aruba network to ensure that the wireless network can support network activity in addition to IPTV video. He tested the network to ensure that students could run file transfers, access university file servers, and browse the Internet while watching IPTV.
Let us know what you think about the story; email: Shamus McGillicuddy, News Editor