Monday, November 14, 2011

The reality of video over wireless architecture


In just the last few years, video application usage has increased significantly and is comprising a greater portion of Internet traffic every day. Rich-media-hungry smartphones and tablets have flooded the marketplace
and more applications that drive video usage continue to arrive on the market.


Providing high-quality video over wireless poses challenges above and beyond sheer bandwidth requirements. For starters, video traffic has very low tolerance for packet loss in the transport network from video server to video client. High or variable latency can also cause issues for streaming video applications.
Wireless networks must take these factors into consideration during the design phase.Video over wireless becomes even more challenging in high density, high-usage scenarios such as classrooms or training
rooms where dozens of users may be simultaneously accessing a single video source. Worst-case scenarios must be considered when designing wireless networks that will be used for such applications.


A key to delivering high-quality video over wireless is sufficient bandwidth capacity of the wireless network and its ability to deliver high throughput in actual operation. Video operates at a constant bit rate so it becomes a math problem to determine the overall capacity required of the network based on maximum number of expected users and the bandwidth required by the highest rate applications. Video is frequently the highest bandwidth application expected on most networks.

To generate higher capacity , people always refer to multicast approach. With multicast video, a single video stream is sent from the source with users desiring to watch the stream subscribing to it. This reduces bandwidth consumption on the network since a separate stream does not need to be established and maintained between the video source and each individual station. This works well for wired networks; however in wireless, multicast packets are re-transmitted if packet loss is experienced a common occurrence in wireless. If a multicast video packet is corrupted, all wireless users subscribed to that video will experience degraded quality.

In fact, the wireless infrastructure still being considered immature in dealing with video streaming. Though we have MIMO wireless , but as the number of user increase, the capacity will gradually decrease.




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