HD Video Over Wi-Fi: It's a Question of Quality
It seems as if Wi-Fi is everywhere nowadays. In fact, it can be said that it has become the de facto home networking technology due to its flexibility and ease of use for Internet surfing and data connectivity. With new IP-based video content and the proliferation of portable displays such as iPads, users increasingly desire to use Wi-Fi networks to distribute video throughout their homes.
While applications such as Web browsing and e-mail can operate effectively using traditional Wi-Fi solutions, video and multimedia streaming applications place greater demands on a home network because they have unique requirements.
Until now, service providers have been reluctant to offer wireless in-home video distribution to residential subscribers because of issues of quality and reliability, both of which impact customer satisfaction.
The Trouble with Conventional Wi-Fi
Operating mostly in the 2.4 GHz radio spectrum, the Wi-Fi radio spectrum is quite narrow and supports very few channels, leading to congestion in urban areas with neighboring Wi-Fi systems. Compounding the problem, Wi-Fi shares the same frequency as microwaves, cordless phones and other appliances, which, in many cases, leads to limited throughput or spotty reception.
And although Wi-Fi is designed to share many devices on the same radio channel, using a collision avoidance technique (CSMA) the mechanism is inadequate for high-bandwidth applications such as video.
All of these factors impact the level of performance needed for video distribution. No network operator wants to deliver services that fail to meet the expectations of subscribers, nor do they want to deal with the increased number of support calls and truck rolls that would ensue.
Video-Grade Wi-Fi Meets the Requirements
Despite the known problems with Wi-Fi, the advantages of Wi-Fi networking remain compelling ? they include easy, fast and cost-effective installation, as well as the flexibility to place set-top boxes (STBs) and TVs anywhere in the home. Users don't want to be limited by coax jacks locations. In addition, service providers have to support the changing viewing habits of customers who are spending more and more time consuming video content on their Wi-Fi powered iPads and laptops.
Service providers want to offer reliable Wi-Fi that can deliver video consistently throughout the home. In order to overcome the challenges of distributing HD video over the traditional 2.4 GHz band, service providers are now adding incremental support for the 5 GHz radio band to create concurrent dual-band Wi-Fi access point devices in which the clean 5 GHz spectrum is used for video streaming.
This is a step in the right direction, but still not enough. Most conventional Wi-Fi implementations are optimized for best effort, peak-rate data streaming. However, video is very sensitive to packet loss, latency and jitter, which results in artifacts on the consumers' screens. In addition, whole-home coverage and consistent signal becomes mandatory: Consumers may have their STBs and TVs located in various corners of the home and can't be expected to move them in order to get a better signal, nor will they tolerate flicker on their screen when someone crosses the room and blocks the radio signal momentarily.
What is a Video-Grade Wi-Fi Access Point?
A video-grade Wi-Fi access point is designed to stream video reliably throughout the home and with the right level of quality of service. It needs to work well with any third-party Wi-Fi client to stream multiple high-bandwidth HD movies simultaneously to multiple portable screens, tablets and STBs throughout the home effectively while maintaining a flicker-free picture. This must be accomplished seamlessly without any proprietary "secret sauce," enabling a good user experience on all portable devices, which typically do not have embedded video-grade Wi-Fi due to size and power constraints.
Range and throughput consistency are two of the most important parameters of video-grade Wi-Fi. A combination of digital beam forming and antenna diversity has proven to provide the right combination of performance and cost for video-grade Wi-Fi technology. While a conventional 802.11n MIMO system transmits from multiple antennas, a digital beam forming enabled Wi-Fi system does so while controlling the phase of the transmitted signals, to gain coherent signal summation at the client location, effectively increasing the received power on the iPad or STB.
The implementation of digital beam forming in a way that does not require any collaboration from a smart Wi-Fi client is the key to achieving gains when transmitting HD video to portable devices.
Streaming to multiple client devices simultaneously is even more difficult. A video-grade access point must have the right quality of service mechanism to make sure that video traffic is protected against other types of traffic. More importantly, it must ensure that all video streams are treated equally and do not interfere with each other. Some solutions may include a scheduled access, "slicing up" air time into well calculated "time slots" ensuring that every video stream to every iPad and STB in the home receives the required bandwidth.
Finally, one of the main concerns heard from service providers regarding Wi-Fi for video applications is interference. Interfering signals may eventually affect even the relatively clean 5 GHz band. A video-grade Wi-Fi system would typically leverage the wide spectrum benefits of the 5 GHz band. It would continuously observe and assess any interferences emanating from the various spectrum channels and make a real time channel swap in case a cleaner channel is required to avoid interfering signals.
Consumers want to take advantage of HD video content and view it on any portable device or STB anywhere in their home. This means a better quality Wi-Fi solution is an absolute requirement in the home. Home gateways that support concurrent dual-band, video-grade Wi-Fi solutions and support wireless STBs, connected TVs and tablets will ensure a superior viewing experience.
Lior Weiss is vice president of marketing at Celeno Communications.