A new WLAN enterprise video wireless transmission optimization

　From IPTV streaming to FaceTime video, enterprise video applications are growing rapidly. Typically these videos are sent and received via mobile devices connected to the enterprise wireless LAN. Now network administrators must implement a new WLAN design to optimize wireless video transmission without performance degradation.

　　The challenges of video WLAN design go far beyond bandwidth limitations

　　When building a wireless local area network (WLAN) to support video applications, capacity is obviously a factor to consider, but capacity is more than a simple bandwidth issue. The bandwidth requirements of video applications are affected by resolution, frame rate and codec. For example, a 720p or 1080p surveillance camera recording 6-10 frames per second (FPS) and encoded with H.264 requires 1 to 2 Mbps of bandwidth. However, viewing a 72-inch HD video at 120-240 FPS may require up to 30 Mbps of bandwidth to achieve a satisfactory viewing experience.

　　Codecs can reduce throughput at the expense of quality, but it supports multiple IPTV channels. And mirroring data can also use up available AP or RF capacity. The popularity of video in high-density environments, such as classrooms and dormitories, has intensified the competition for online time. To make matters worse, many video streams are multicast to reduce the load on wired networks, but over Wi-Fi, multicast reduces the data rate to the weakest (oldest and furthest) clients. In a hall filled with a variety of consumer electronic devices, the problem of poor quality is bound to exist unless further measures are taken to optimize and prioritize video transmission.

　　Defining capacity requirements for wireless video applications

　　The first step to ensuring wireless video performance is to establish the network capacity and performance requirements needed for video and multimedia applications in the WLAN. Wireless network vendor Aruba Networks recommends classifying video into the following categories:

　　Broadcast IPTV over Wi-Fi. This requires streaming latency-insensitive traffic down a single line for each channel's users over many high-bandwidth (1 to 4 Mbps for SD or 6 to 10 Mbps for HD) channels.

　　◆ Live event video streaming (webcasting) over Wi-Fi. This requires unidirectional downstream delivery of latency-insensitive traffic, specifically over a single high-bandwidth (1-4 Mbps) channel for all users to watch.

　　◆ IP surveillance recording over Wi-Fi. This requires uplink or downlink transmission of delay-insensitive traffic, using many channels to deliver video of varying quality (500 Kbps to 2 Mbps) for a small audience.

　　◆Interactive video conferencing. This is two-way delivery of traffic that is subject to traffic latency and jitter (up to 150 to 200 milliseconds), but requires low symmetrical bandwidth (1 Mbps) on both sides.

　　◆ Video on demand (training, pre-recorded programming). This requires single-channel delivery of latency-insensitive traffic, with multiple users per channel consuming high-bandwidth channels (1 to 4 Mbps for SD or 6 to 10 Mbps for HD).

　　These examples illustrate all the changes in WLAN deployments for video and multimedia: directivity, throughput, latency and jitter tolerance, and the number of channels and users. Another key metric is error tolerance, low packet error rates are usually desirable, but can also cause problems for UDP multicast.

　　Design Considerations: 802.11n Wireless LAN for Wireless Video Delivery

　　Fortunately, enterprise WLAN products are mature enough to provide a solid foundation for video and other multimedia applications. Video WLANs should use 802.11n to increase capacity, density, and reliability. Key 802.11n features and design considerations include:

　　Channel bonding and spatial multiplexing through multiple-input multiple-output (MIMO) antennas increase the capacity of each radio to 450 Mbps (3x3) or 600 Mbps (4x4) rates, enabling each AP to support more video users.

　　◆The available throughput per user will be limited by the capabilities of Wi-Fi clients, especially smartphones and tablets with 1x1 MIMO (up to 65 Mbps, decreasing with distance). This may be sufficient for a single video stream, but keep in mind that slower clients may bring down video performance for each user, and design the WLAN to account for these lower data rates.

　　◆ Leverage 802.11n standard options such as A-MPDU (MAC Protocol Data Unit) and block acknowledgement to further increase data throughput for delay-insensitive one-way video streaming.

　　◆802.11n devices can support 2.4 GHz and/or 5 GHz. When higher throughput is needed, take full advantage of 5 GHz channels. For example, use the coverage designed by the Forecast WLAN Planner to replace APs to meet the uplink and downlink bandwidth needs of throughput, user density, and user rate. But don't assume that a strong signal will result in high-quality video, and verify performance frequently.

　　◆Use Wi-Fi Multimedia (WMM) prioritization to allow video to have more uptime than data, but without consuming all available bandwidth. Give applications that are sensitive to latency and jitter (such as VoIP, video conferencing, etc.) higher priority than one-way data flows. WMM admission control may help avoid overloading an AP.