4G systems have been continuously evolving to cope with the emerging
challenges of human-centric and machine-to- machine (M2M) applications.
Research has also now started on 5G systems. Scenarios have been proposed and
initial requirements derived. 4G and beyond systems are expected to easily
deliver a wide range of human-centric and M2M applications and services in a
scalable, elastic, and cost efficient manner. The 3GPP IP multimedia subsystem
(IMS) was standardized as the service delivery platform for 3G networks.
Unfortunately, it does not meet several requirements for provisioning
applications and services in 4G and beyond systems. However, cloudifying it
will certainly pave the way for its use as a service delivery platform for 4G
and beyond. This article presents a critical overview of the architectures
proposed so far for cloudifying the IMS. There are two classes of approaches;
the first focuses on the whole IMS system, and the second deals with specific
IMS entities. Research directions are also discussed. IMS granularity and a
PaaS for the development and management of IMS functional entities are the two
key directions we currently foresee.Comment: 8 pages, 3 figures, 1 table, this paper has been accepted in IEEE
Communications Magazine and will appear in January 2016 issue of the Network
and Service Management Serie