Wireless Joey to test 802.11ac’s mettle

Posted By on Jan 10, 2014 | 0 comments

Among Dish’s CES announcements this week was the introduction of the new Wireless Joey client to their Hopper DVR.  The Wireless Joey will receive content from its paired Hopper via a dedicated 802.11ac wifi network.  (On a related note, ViXS and Quantenna announced integration of Quantenna’s 4×4 802.11ac chipset into a ViXS reference design for a 4K/HEVC STB, aimed at wireless display of Ultra HD.)

Celeno pioneered the effort to harden wifi for in-home delivery of service provider video several years ago, with an early implementation of beamforming intended for a dedicated 5 GHz 802.11n network.  802.11ac standardizes critical elements of beamforming, with the goal of making beamforming more widely available, and more reliably interoperable among devices using different wifi chipsets.  (802.11ac also adds new modes with higher order modulation, and support for wider transmission channels, to enable higher throughput than 802.11n in certain circumstances, but these have much less relevance to improving the quality of video delivery.)

It will be very interesting to see whether the Wireless Joey proves reliable at displaying 802.11ac-delivered video.

It may seem odd to question whether the latest, greatest wifi technology will be reliable for video delivery.  After all, AT&T started using wifi STBs for it’s U-verse service a few years ago; millions of people watch OTT (over-the-top) internet video using devices such as AppleTV, Roku, Chromecast, and Smart TVs, most using older, low-end (and in many cases 2.4 GHz only) wifi adapters; and 802.11ac is the most reliable wifi revision yet, operating solely on the much less congested 5 GHz band, which offers many more non-overlapping channels than the 2.4 Ghz band.

There’s been a dearth of publicly available information on the results experienced with existing service-provider deployments such as AT&T’s, however, and there are reasons to feel uncertain.

Virtually all internet video is delivered using HTTP adaptive streaming, which is quite good at mitigating occasional throughput problems, because it uses deep buffers—even up to as much as a minute of buffering.  The price for this buffering is significant delays to acquire a new video stream, low-quality video at the start of the session, or a combination of both.  This has proved an acceptable experience for OTT devices like AppleTV and Roku, and services like Netflix and Hulu, where watching different videos is always separated by menu navigation.  But that’s not the channel-surfing viewing experience consumers expect for their “normal” TV service, from a provider like Dish, where consumers remain extremely sensitive to channel-change delays, always expect the video quality to be excellent, and don’t expect one TV to be showing content delayed by 60 or 30 or even 5 seconds compared to another.  And given it is part of a DVR system, consumers will expect trick modes to work like a conventional DVR—another thing for which HTTP adaptive streaming is not well-suited.

That means Dish certainly won’t be using conventional HTTP adaptive streaming with deep buffers.  They will have to use something with much lower latency, much closer to what they currently use for wired Joeys.  As a result, the quality of video for the Wireless Joey will be much more sensitive to momentary performance issues with the wireless link than are OTT devices.  So whether or not the dedicated 802.11ac network is able to provide consistent, reliable delivery will be critical.

802.11ac does have the advantage that it uses the much less congested 5 GHz band, but 5 GHz has a significant downside, also: in wireless, the higher the frequency, the shorter the range.  So while 802.11ac can be expected to outperform at close range, how well it will perform at longer range (such as where the Hopper is in one corner of the house, and Wireless Joey is in an opposite corner) or where the device is placed sub-optimally (such as inside a cabinet, or behind a TV) remains to be seen.

Then also, the capacity and congestion advantage of 5 GHz relative to 2.4 GHz is a statement about the present, not the future.  In the US, the 2.4 GHz band supports 3 non-overlapping 20 MHz wide channels.  The 5 GHz band supports 21 non-overlapping 20 MHz channels, including the DFS band (not supported by all devices).  But 802.11ac mandates support for 80 MHz wide channels (and optionally for 160 MHz wide channels).  In practice, even 802.11n normally uses 40 MHz wide channels at 5 GHz.  There are 9 non-overlapping 40 MHz channels, and just 4 non-overlapping channels at an 80 MHz width.  As devices rapidly transition to 802.11ac support, the relative capacity and congestion of the 5 GHz band is liable to end up looking a lot like the 2.4 GHz band currently looks.

That reality underscores what is, arguably, the biggest challenge for in-home wireless distribution of service provider video: the environment is very dynamic.  When a wired device is installed, the wiring is a closed ecosystem, and a device that works well at the time of install is very likely to continue working well for a long time to come.  When a wireless device is installed, the environment is very likely to change.  The customer, or even a neighbor, bringing home a new piece of equipment, or even simply moving equipment, can change it.  As a result, it’s not nearly as clear that a device which works well at the time of install will continue working well.

None of this is to say that 802.11ac video distribution can’t succeed.  After all, even Ultra HD 4K video would represent just a small fraction of 802.11ac channel capacity, and advanced 802.11ac features conceivably could prove sufficient to deliver reliable quality in a high percentage of cases.  But until we have more practical experience, nor should anybody assume that success is assured.  So we should all look forward to seeing what the real-world experience turns out to be for devices like the Wireless Joey.