HDVoice: On The Cheap & Analog RJ-11 Style

HDVoice RJ-11 Wall Plate A short while back I addressed the question of how DECT & CAT-iq may foster the broad deployment of HDVoice. At that time I described one possible scenario where carriers would deploy customer premises equipment (CPE) with an on-board cordless base station. Although a frontrunner, and the basis of Comcast’s (decidedly non-HD) HomePoint service, this is not the only approach afoot. There’s another possibility arising that involves conveying HDVoice over a plain old analog RJ-11 connection.

At first glance HDVoice and analog lines would certainly seem to be mutually exclusive. The common wisdom is that wideband telephony requires the use of an all-IP call path. This is in fact a generalization, and not absolutely true.

Firstly, it has long been possible to pass wideband audio, in the form of G.722 encoded media, over the PSTN by way of ISDN connections. Also known as BRI interfaces, an ISDN connection supports  up to two 64 kbps channels (bearer channels) and one D channel for the purposes of call setup & teardown signaling. High-quality voice using G.722 was one of the selling points of ISDN in the 1980s.

Broadcasters have long used ISDN lines as a high quality, low latency way to get audio between locations, most typically so that voice talent could “phone-in” their work. However, the use of ISDN is waning as IP-based networks have come to dominate the landscape, offering higher data rates at lower cost.

PolycomVTX1000-300 Secondly, Polycom’s VTX-1000 conference phone is able to pass wideband audio over a POTS line when calling others of its kind. The VTX-1000 uses a hybrid approach, using the POTS line in much the same manner as early internet  users relied upon dial-up modems for internet access.

The VTX-1000 features an on-board v.32 modem, passing the AMR-WB encoded audio (50 Hz – 7 KHz @ 12.65 kbps) across what is basically a point-to-point network connection. It essentially tunnels though the PSTN, not unlike a fax machine, passing digital data over the analog line.

Neither of those approaches offer a practical means of allowing widespread deployment of HDVoice. Yet there is another, potentially very practical approach to deploying a large number of HDVoice end-points using an analog RJ-11 connection for the last link.

ARRIS-Touchstone-eMTA-300 Arris Corp claims that they can HDVoice enable as many as 15 million of their existing cable CPE by way of a firmware upgrade. These existing products use an Intel chipset that can deliver wideband telephony over existing DOCSIS networks, but the existing CPE provide only an analog RJ-11 connection for use with a traditional home phone.

While the Arris CPE may be able to handle G.722 streams, passing the resulting analog signals to the RJ-11 jack, there would seem to be no analog phones capable of taking advantage of that higher quality analog signal. By design traditional analog telephones deliberately roll-off frequency response pursuant to PSTN standards.

Introducing unwanted high-frequency information into a signal destined for analog to digital conversion creates a very real problem called “aliasing.” (see Nyquist theorum, aliasing) All A/D convertors filter their input signals specifically to avoid this problem.  It would seem that some new kind of analog phone would be required to realize the benefits of HDVoice  by way of the Arris CPE.

Gigaset-C610IP-243 Enter Gigaset. Earlier this week Gigaset’s Tony Stankus told me that they have beta firmware that supports the use of wideband audio via the analog interface on their DECT base stations. Thus a Gigaset C610A cordless phone could be connected to an Arris cable box by way of an analog RJ-11, and deliver a real HDVoice experience to the home user.

The advantage to this approach is principally cost. The CableCo need only deploy a firmware upgrade to their existing CPE, and recommend or even resell the Gigaset DECT phones to users desiring the HDVoice experience. This is clearly cheaper than deploying new, CAT-iq capable CPE on a large scale.

One potential down-side to this approach is that it doesn’t address IP connectivity to the DECT base. As such it doesn’t provide the kind of data services (email access, Facebook & Twitter integration, weather & headlines, etc) that Comcast trumpeted as features of HomePoint. However, I suspect the reality is that such services have little value on the 1.5” LCD display of a cordless phone handset.

Doug Mohney of HDVoiceNews notes in an article for TMCs IP Telephony Online Community that the newer Gigasets, specifically the C610A, would be the primary targets for his new firmware. According to Doug;

“While I like the idea of Gigaset getting more aggressive in brand awareness, I love the fact that Gigaset’s IP phones can be firmware upgraded to support analog HD voice. Tony Stankus, these days Product & Marketing Director for Gigaset USA, said any Gigaset IP phone with an Ethernet interface could get a firmware upgrade to support analog 7 kHz through the FXO port, but the emphasis would be on phones such as the C610 and newer models.

Enabling analog 7 kHz means you can take a Gigaset IP phone — well, more importantly, the DECT base station, so you get cordless functionality — plug it into a cable MTA box that supports 7 kHz and G.722, and you get a phone that supports analog HD voice with existing cable hardware. Two firmware upgrades — one for the cable gear for the Intel Puma 5 chipset so support G.722 and 7 kHz out of the FXO ports, one for the Gigaset hardware — and you have an end-to-end cordless HD voice solution for the home. ”

Perhaps this new firmware requires the increased hardware resources (memory & CPU) of the newer DECT base. We can safely assume it would be compatible with older handsets, just as we use the C610A with the older A58H and C59H handsets. CAT-iq compliance means that all the handsets pass G.722 encoded media to & from the base radio.

I might also guess that, if warranted, Gigaset could offer a new, cheaper, non-IP capable model of the DECT base that was still capable of wideband analog connectivity. I’m sure that the CableCo’s would be interested in whatever cost savings could be managed, making the end-user cost attractive while sustaining a reasonable margin.

If this were to happen in a big way then other players, like Canada’s VTech, the largest maker of cordless phones in the world, would likely get into the game. It would certainly rationalize their claims of “HD Audio” on devices that only support analog connectivity.

There you have it. There may just be a new kind of analog home phone in our future. Despite it’s old skool, analog connectivity it may well be HDVoice capable.

  • Donny

    Has anyone put this into practice? I’m very interested!!

    • mjgraves

      Not to my knowledge. It all hinges on a CableCo pushing a firmware release to an Arris MTA. As no CableCo has as yet committed to HDVoice this has yet to happen.