SIP endpoints such as softphones / headsets used for IP based enterprise VoIP calls,  for WiFi calls, and for calls from third party communication apps such as WhatsApp, Viber etc. are becoming the norm. And with continued integration on the phone side (see Apple CallKit), these will continue to proliferate.

However, 3G is not going anywhere for a long period of time.  Subscribers are projected to continue to grow. And that means SS7 based phone calls.  

Combine the two together, and that means there will be more and more SS7 to SIP phone calls. I mean, while there will be more and more WhatsApp, Lync, and Viber phone calls between those that have those apps, there will also be calls to/from those with an SS7 base (3G) and those with an IP / VoIP / WiFi base. And even within the SS7 family, there are different variants because of regionality and slight variations in standards.  And then there’s SIGTRAN as well.  It’s complex. There is a lot of SS7 to SIP interworking required to cover all the different use cases.

Because user networks will invariably vary, and because coverage is important for any service provider, the need for interworking between the two types of networks will be an important part of any service provider for years to come.  For more information please read this whitepaper.