Leased line loss may be VoIP gain

Leased lines have played a fundamental part in the transmission of voice across radio communications networks. Now with the proliferation of IP networks and telco infrastructures that are geared up for multimedia transport, the end is in sight for the good old trusted leased line.

However, the demise of this service will provide benefits to organisations that are well equipped to tap into the immense potential of its replacement - Voice over IP.

The Telstra private lines service (PAPL) has been in operation for many years, as have other comparable services all over the world. PAPL provides voice-grade leased lines that are crucial to the operation of many multi-site mobile radio networks.

Typically, leased lines are used to interconnect two or more radio repeater sites thereby enabling an organisation to extend their radio coverage beyond a single site and across a broad region.

They are also used to connect dispatch communications centres with radio transmitters that are further away.

The service is reliable but it is expensive. As an example, the cost of operating a four-wire leased line between two sites separated by 50 km could be more than $10,000 a year.

Installation costs are normally close to a thousand dollars, depending on the number of exchanges used.

Telstra previously announced that from 1 December 2006, it would no longer be providing this service to new users. Although existing users will not be affected, many in the industry see this as a signal that Telstra will eventually wind up the service.

And you couldn't blame them. Telstra, like most telcos around the world, is moving towards an infrastructure that is based on IP packet switching and will enable the convergence of voice, data and video.

That is the bad news.

The good news is that Voice over IP looks to be a ready-made replacement to leased lines, offering a number of benefits.

IP networks are becoming more and more accessible in both the metro and regional areas.

In my company's experience, most large organisations (both government and commercial enterprises) already have their own private wide area networks based on IP. Additionally, ADSL is now within easy reach of most other organisations, ensuring that even modest internet connections of 256 Kbps are readily available.

Usually, these IP services have not been installed for voice communications but rather for email and other corporate IT functions. So the additional cost of using this existing infrastructure, in place of leased lines, is marginal.

But even the cost to install a basic ADSL connection for voice communications can be as low as $49 per month (plus standard line rental).

However, moving across from PAPL to VoIP requires an understanding of the nature of this technology. Consideration should be given to the impact on an organisation's network bandwidth as well as the special needs of radio systems.

Bandwidth minimisation is achieved through voice compression, a major feature of VoIP that also facilitates the use of low speed connections.

However, voice compression is not compatible with radio signalling techniques and when coupled with the nature of UDP transmission, this can introduce reliability issues, if the right equipment is not used.

A few years ago, when my company first ventured into the new world of radio over IP (VoIP for radio), these issues were not well known or appreciated. In fact, most organisations did not have the expertise to fully understand these issues.

Radio technicians tended to be unfamiliar with IP terminology, let alone its technical aspects, potential and limitations. IP was considered to be something solely the domain of the IT people.

Since that time, we have witnessed the transformation of many organisations (including radio dealers and integrators) producing a radio workforce that is skilled at IP. A number of organisations that we work with have had the foresight to provide re-training of their radio communications staff.

It is also clear to us that many organisations have seen the convergence of radio and IT and have taken the step of merging their previously separate radio and IT groups into a single communications entity.

It is also becoming more common to find traditional IT people who are interested in radio. This is not unexpected when you consider that the job of integrating radio networks into the corporate data structure often falls to those that manage the IT systems.

Clearly, the demise of the leased line needn't be a concern for organisations that rely on such connections to operate their radio networks. There is much to be gained from moving to VoIP, not least the cost savings.

It is important, however, that implementation be carried out with the right advice, techniques and equipment.

In our experience, smart organisations have already laid the foundations for this by providing cross training of their radio and IT staff.

The obvious replacement of the leased line with VoIP for radio communications will usher in a new era of converged communications and provide a multitude of advantages and opportunities.