How to Make an HD Phone Call

The PSTN is a marvel, allowing anybody with a phone number to talk to anybody else regardless of geography. The system is also antiquated, using technology that delivers sound quality inferior to AM radio. By contrast, Voice-over-IP is technically capable of delivering better than CD quality sound. For phones this type of capability is often termed “HD Voice”.

For a call to use HD Voice, its entire path must be over IP, with no PSTN legs. There are two classes of reason why this rarely happens, technical and business. The business reason is that telephone companies compensate each other for calls on the PSTN. These termination charges are a significant source of revenue for VoIP service providers, and an incentive to favor the old, inferior technology. There are several technical reasons. Convenience of dialing is a debatable one. On the one hand, every phone has a numeric keypad, and phone numbers are familiar to the point that people find them intuitive. On the other hand, email-style addressing of phone calls is widely used by Skype (News - Alert) and similar PC-based services. Using email-style addressing for phone calls (“SIP addressing”) is problematic with a phone keypad, but modern phones have built-in directories and recent call lists, so most calls can be made this way rather than by having to enter a new address.

Going to SIP addressing guarantees end-to-end IP connectivity and it’s easy to do technically: provision your firewall to make your VoIP system reachable over the Internet, then add SIP records to your DNS. Having done that, there is a simple method to allow calls made with old-style phone numbers to complete over IP end-to-end. It is called ENUM. Organizations like E164.org provide databases of IP addresses associated with phone numbers. It is trivial to add your phone numbers to such databases. This covers inbound calls. Then you need to provision your phone system to check an ENUM database when making outbound calls. Again, not rocket science.

If you take the simple steps of adding SIP records to your DNS, registering your numbers in an ENUM database and doing an ENUM lookup on outbound calls, your phone bills will plummet and your calls will sound vastly better. IT

Michael Stanford (News - Alert) has been an entrepreneur and strategist in Voice-over-IP for over a decade. Visit his blog at www.wirevolution.com.

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