When Bharti Airtel first approached us to help them create a geo-redundant disaster recovery (DR) solution for their pan-India VoLTE service, little did we know that it would need to be done during a pandemic. The project was only a couple of months old when the pandemic and lockdown happened. Our first thought was “how is it possible to continue?” But, once we reviewed our options, we realized we were more than able to get it done.

The challenge

The project was the largest we’ve carried out for a voice over LTE or VoLTE deployment. Bharti Airtel is running a service for 150+ million 4G/LTE subscribers. The core network is spread across India with 12 hubs controlling 22 circles. They wanted to ensure that the service experience for their customers was seamless. Although they had redundancy built into each regional hub, they wanted a DR solution that would work even if an entire regional hub went down — they needed geographical redundancy.

When deployed as a cloud solution, VoLTE uses the data capacity of the 4G/LTE network and a cloud-based IMS server (IP Multimedia Subsystem) located in the core network to provide a full range of voice and, potentially, video communications for both consumers and enterprises. Services such as the Bharti Airtel Emergency Alerts Service, which allows subscribers to alert up to 10 loved ones with one call, also rely on the availability of the system during disaster situations. It is critical, therefore that these business- and mission-critical applications are highly reliable, secure and available, even in case of a disaster. Thus, Bharti Airtel turned to Nokia to design a disaster recovery (DR) solution that would ensure the reliable delivery of its VoLTE services to all its customers.

Being cloud-based, it is possible to create an n+1 redundant solution or, in this case, 12 hubs plus 1 redundant hub. This 12+1 DR solution provides disaster recovery backup, including the IMS functions needed for VoLTE. In case one of the 12 Airtel regional hubs fails, there is an automatic cutover to the redundant DR hub without any service interruption. The Kharadi, Maharashtra, location was chosen for the redundant DR site hosting all of the VoLTE Core VNFs (including CFX, NTAS, NN and MRF) on the Nokia CloudBand platform.

Leveraging global experience

Being the largest project of its kind, it raised several challenges. Although we didn’t have a reference project of the same size and scale, the experts across the globe were able to guide us and extend help based on their prior experience. This is one of the main advantages of being part of the Global Services team at Nokia. We have teams working with customers worldwide that can offer valuable insights and learnings. The global organization also helped us to fill local skills shortages using remote experts from around the world.

The ability to supplement local resources with global ones was one of the keys to coping with COVID-19 during the initial lockdown. Even the smallest and simplest of activities, became the biggest of challenges. One such challenge was obtaining SIM cards and handsets for testing, which were restricted.

But good project governance and a spirit of “One-Team” that included both local and global resources made the project a success.

Delivering against all odds

The core objective of the entire program was “to handle one full hub failure, in the event of an exigency”. As it turned out, we managed to delight the customer even before the project was formally live. Several times during the project, while we were still in execution, actual hubs went down and the live traffic had to be moved either manually or by auto switchover to the redundant DR site. Despite not being formally launched, it managed to hold the live subscriber traffic with equal stability and robustness, leading to elevated network uptime and sustained subscriber satisfaction, two of the key KPIs of this project, for the customer.

Many lessons have been learned during the pandemic. In some cases, we have realized that we need to upgrade our systems and be better prepared. In other cases, we have learned that we are more than capable of supporting remote work in global businesses. Ironically, while building a geo-redundant DR solution, we realized that Nokia Global Services had geo-redundancy as well. This proved to be one of the key aspects to meet the customer’s expectations and delivering this important project even in the middle of the pandemic.

If you are interested in learning more about the Bharti Airtel VoLTE DR solution, we’ve prepared a case study that you can download here.