In the context of our discussion on IMS and SIP, Paul Golding makes the connection between IMS, SIP and 3G:
In my opinion, 3G is IMS. What SIP enables is a generic “connecting” protocol. We don’t necessarily have to be interested in connecting users to make a voice call. In other words, SIP isn’t just a “calling” protocol.
Thus far, mobile networks have been almost exclusively concerned with voice calls. The data model that has emerged so far is WAP, which is essentially “Web-lite”. The paradigm is connecting users with information in the form of Web pages (portals etc.)
However, the essential nature of mobile technology is connecting people. This Person-to-Person (P2P) nature will be a dominant feature of mobile computing. We need to grasp what P2P “connecting” is all about. Today, we talk to each other. But, tomorrow, we shall: Click to play, to share, to view, to update, to invite, to compare, to tag, to consult, to message, to conference
Click to connect!
GSM only allows “dial to talk”, which is why we need SIP. With SIP, we can do all the above things.
I believe that the future of the 3G era is:
3G = SIP + Presence
3G = IMS + Presence
IMS allows operators to build an infrastructure that will support this paradigm. Therefore IMS will become important in the future of the 3G era. 3G is IMS.
MobileInfo writes on the need to look beyond 3G:
3G performance may not be sufficient to meet needs of future high-performance applications like multi-media, full-motion video, wireless teleconferencing. We need a network technology that extends 3G capacity by an order of magnitude.
There are multiple standards for 3G making it difficult to roam and interoperate across networks. we need global mobility and service portability
3G is based on primarily a wide-area concept. We need hybrid networks that utilize both wireless LAN (hot spot) concept and cell or base-station wide area network design.
We need wider bandwidth
Researchers have come up with spectrally more efficient modulation schemes that can not be retrofitted into 3G infrastructure
We need all digital packet network that utilizes IP in its fullest form with converged voice and data capability.
OFDM is one of the technologies which will be the cornerstone for 4G networks. Wave Report writes about OFDM: Frequency division multiplexing (FDM) is a technology that transmits multiple signals simultaneously over a single transmission path, such as a cable or wireless system. Each signal travels within its own unique frequency range (carrier), which is modulated by the data (text, voice, video, etc.)Orthogonal FDM’s (OFDM) spread spectrum technique distributes the data over a large number of carriers that are spaced apart at precise frequencies. This spacing provides the orthogonality in this technique which prevents the demodulators from seeing frequencies other than their own. The benefits of OFDM are high spectral efficiency, resiliency to RF interference, and lower multi-path distortion. This is useful because in a typical terrestrial broadcasting scenario there are multipath-channels (i.e. the transmitted signal arrives at the receiver using various paths of different length). Since multiple versions of the signal interfere with each other (inter symbol interference (ISI)) it becomes very hard to extract the original information.
From Indias viewpoint, investing in the research and development of next-generation networks like 4G is something which should be strongly considered.