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Are the days of traditional TDM PSTN numbered?

Despite advances in technology providing us all with multiple ways to communicate, telecommunications remains a central part of business and, indeed, everyday life.  But it is the advent of IP telephony that has enabled the industry to keep pace and move with the times.

Traditional telephony is based on the public switched telephone network (PSTN) which consists of voice services based on time-division multiplexing (TDM).  Just as packet-based data services have largely replaced circuit-switched data, packet voice is slowly replacing TDM voice.

But with huge numbers of assets tied up in the public switched telephone network, questions about next-generation voice services are surely critical – apart from anything else, financially.  So where does the industry go from here?

In many cases, providers are starting to offer blended IP and legacy systems that offer additional unified communications (UCC) capabilities, such as messaging, presence web-based and video conferencing. At the heart of these offerings is SIP, or session initiation protocol, which controls communication sessions within these environments. 

SIP and Hosted Voice are both natural successors to traditional TDM voice, as they both allow organisations to take advantage of the cost-savings offered by IP voice (where you don’t have to buy a separate ‘trunk’ for your voice and data but can run them both over one pipe) as well as increased numbering flexibility and business continuity that IP offers.

While, hosted voice is seen by some to offer more flexibility than SIP as you move most of the hardware from the premises into the Cloud, SIP is likely to win-out initially as it requires the least change to the traditional PBX infrastructure that most businesses will have in place already.  Customers can take SIP channels managed via their existing hardware by adding in a relatively low-cost SIP Gateway to their existing switch.

Working in this way means that customers can experiment with IP Voice alongside their existing PSTN and ISDN services thus de-risking their first steps into IP migration.   As IP Voice (if configured correctly) can offer the same quality of voice now as ISDN/PSTN - the migration to completely IP-based systems is likely to be sooner rather than later.  Whether SIP then migrates to fully hosted voice remains to be seen but the move to IP is happening now.