Four Network Considerations

Four network considerations

1. HD Voice uses an added codec in a VOIP phone but is fully interoperable with standard narrowband SIP phones. This is because HD Voice adds another available mode but doesn't remove the ones that are already there; the phone can still support whatever narrowband codecs and connections you had before. If an HD phone calls a narrowband phone, they'll connect in narrowband and work fine. If it calls an HD phone, they can connect in wideband-and will sound a whole lot better than what you're used to.

2. Check that the call routing supports HD Voice. The public switched telephone network (PSTN) today hasn't yet moved to HD, so even if both endpoints are HD-capable, selecting a route over PSTN will force the call down to narrowband. Yes, they'll connect, but they'll connect in conventional narrowband because they're throttled by the PSTN network. To avoid this, routing across private networks and IP networks can preserve full HD quality. So give careful consideration to your dial plan and IP trunking to maximize the extent to which connections can be end-to-end HD Voice.

3. Check that the LAN and WAN can handle G.711 data rates. G.722 uses the same bit rate for HD Voice as G.711 uses for narrowband audio (64Kbps or about 80Kbps with network overhead). But if a user has implemented a high-compression codec such as G.726 or G.729 for a narrowband VOIP system, HD calls could increase network bandwidth. Especially in such systems, the bandwidth and WAN device capacities-including queue and buffer sizes-should be examined.

4. Enable HD Voice features. The most important feature that people will need, of course, is bridging-and the more people on a call, the more important it becomes to have HD Voice connections because the sound gets muddy so easily on conference calls. An easy win-win is to consider starting with an HD Voice-enabled conferencing service provider.

Most important user consideration

Lastly, educate the users. A favorite story about HD deployment is an organization that equipped all of their desktops with wideband phones and enabled people to call desk-to-desk in HD. But when people called out to the PSTN, the calls were in narrowband. As a result, IT received complaints that the PSTN calls sounded bad by comparison. The way they solved this was by turning off HD completely so users had nothing to compare to! 

The moral of this story: Educate your users about HD Voice. Let them know that some calls will not be HD (but no call will sound worse than it did before) because the networks are still catching up. It's like talking to someone who's on a cell phone-you can have the best phone in the world and they'll still sound lousy.

But the world is rapidly moving to HD Voice and that's why the right decision is to be thinking future-proof.

 Jeffrey Rodman is Co-Founder and CTO of the Voice Division at Polycom. Jeffrey has been at the forefront of audio and video communications for most of his career. Following a BSEE Cum Laude and MSEE in Electronic Engineering from CSUN, Jeffrey spent six years developing and enhancing video and test capabilities for military-guided missile systems for Hughes Aircraft Company. During this time, Jeffrey also created a novel approach to sound synthesis that formed the foundation for his Master's thesis. Jeffrey also co-founded Specialty Video Systems to market digital video effects to the entertainment industry.

In 1980, Jeffrey joined Harris Video Systems where he became Director of Engineering, pioneering new digital video processing systems for broadcast and production applications. In 1984, Jeffrey was recruited to build a hardware engineering organization and implement a revolutionary architecture for the then-new startup PictureTel (later PicTel), building the foundation for a family of systems that has transformed the videoconferencing industry. Jeffrey continued on as Director of Hardware Development through PictureTel's formative years.

Jeffrey co-founded Polycom in 1990, and has been instrumental in the realization of Polycom's iconic products for voice, video, network communications and other media. He can be reached at jeffrey.rodman@polycom.com.