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August 27, 2018

Steering of Roaming SS7 and Diameter Comments, Untruths / Truths and Myths

In multiple conversations on the topic of Steering of Roaming (SoR) both in legacy SS7 networks and LTE Diameter based networks I continue to hear:

“I already have an SS7 SoR system (Over the Air, Message based, or Hybrid) and my network is migrating to LTE – I am going to wait and get a solution specific to LTE/EPC/Diameter.”

“Steering of Roaming is different for LTE/EPC/Diameter – I will have two separate systems one for the legacy network (SS7) and one for the LTE network.”

“I have built out my LTE network but don’t have roaming agreements yet so I don’t have to address SoR in the LTE network yet.”

It never ceases to amaze me that there is so much confusion on this topic when the reality is SS7 vs. Diameter Roaming “Same concepts different protocols”.

Oops, once again there are other issues at play that complicate an otherwise simple concept. So what are the complicating issues?

We cannot flash cut a network, so the SS7 and Diameter networks must coexist – i.e. a hybrid network infrastructure.
The LTE network is a flat technology data only network – So what about Circuit Switch Fallback, and Voice over LTE (VoLTE)?
Multimode devices roaming between 3G – SS7 based networks and 4G – LTE/EPC Diameter Based networks.
Are operators using the same or different roaming agreements?

With these issues in the network, it is not surprising that the results of a survey performed by Informa Telecoms & Media, indicated that LTE steering of roaming was number 2 in the top 3 challenges for LTE Roaming as indicated by mobile service providers.

The migration of mobile communications from 2G/3G SS7 based networks to LTE Diameter based networks will take place over YEARS. This being the case, SoR solutions must address roam steering concepts over both networks and protocols. The good thing is — the fundamental concepts of roaming and more specifically mobile station registration is the same in both networks – the difference is the signalling protocols. SoR must have the ability to handle both the SS7 and Diameter protocols. This capability ensures that roamers can be steered to preferred networks regardless of underlying technology. With a broader range of subscriber roaming comes improved Quality of Experience for subscribers, more brand loyalty, and reduced subscriber churn.

Due to the hybrid nature of today’s mobile networks a subscriber might be roaming to a network and using LTE data services. The subscriber then attempts to place a voice call, and no VoLTE services are available – in this case, the mobile network may use Circuit Switched Fall Back (CSFB) to provide either voice or text services. Special SS7 messages are sent to the home network to accomplish the CSFB. SoR solutions must recognize and react to these signals in order to provide voice or text-based services to the subscriber.

Roaming solutions should not be built in silos on a per network technology or protocol basis but rather be designed to handle both technologies. This dual technology concept will support LTE to LTE, CSFB and LTE to 2G/3G interworking thus providing the broadest range of roaming capabilities for subscribers. Additionally, the SS7 and Diameter duality gives service providers the ability to negotiate the most efficient, cost-effective, and higher revenue generating Inter-Operator Tariffs / Roaming Agreements.