We are witnessing a technology shift in telecom networks from the TDM-based circuit switching to packet switching based technologies like ATM and IP. We are also seeing a growing emergence of revenue based on service differentiation, with explosion in demand for the Internet and other data services. However, the increased data traffic volume is congesting the core and access of traditional telecom networks, which were optimized to handle calls with an average three minutes of holding time as against the average holding time of 20 minutes for Internet sessions.

Next-generation Networks
The above, coupled with the global deregulation, has led to the emergence of next-generation networks (NGNs), with more and more service providers shifting towards packet-based networks. VoIP, which was initially considered a threat by service providers, has gained acceptance and the new networks are considered to be a step toward fulfilling the promise of multimedia. All this has contributed to a need for a flexible network that is capable of providing the present and next-generation services. This is the foundation of ‘network convergence’, with inter-working of packet-based IP and the traditional switched circuit networks (SCN) or PSTN networks being the first step toward the ‘next-generation networks’.

Addressing the Multi-operator Environment
In the new multi-operator environment, operators will like to carry the maximum traffic through their networks to maximize revenues. They also need flexible charging plans to address different customer segments.

The flexibility in charging depends on the methodology used for charging calls and issuing bills to customers. In case of long-distance calls, more than one operator is likely to be involved—two on the access side and at least one long-distance operator—with the call revenue shared by operators based on some mutual commercial agreements. Billing may be performed by either the access provider or by the NLDO.

CDR-based Charging
The CDR-based charging/billing—successfully deployed worldwide and supported by all switching technologies using CCS7 signaling deployed in India—provides the highest level of flexibility to operators.

CDRs can be transferred in near real-time to billing centers by switches for off-line processing and generation of bills as well as other statistics for subscribers and other operators.

The charging of calls is difficult to perform in real time in today’s complex environment. Since CDRs are generated at different points in the network, the real bills can be computed by off-line processing of CDRs at billing centers and any operator can issue the bill based on a pre-defined revenue-sharing formula. Thus, the following advantages appear to emerge:

• Flexibility for operators
• Avoid real-time modification of data at exchanges
• Accuracy of charging
• Meet subscribers’ demands on per call basis
• Easier dispute settlement mechanism between operators
• Data can be used for network QoS (as well as other subscriber statistics) and can be determined on per call basis.

Standardization
The European Standardization Institute ETSI’s ‘TIPHON’ project was established to address inter-operability between SCN and IP networks for voice applications (as well as related multimedia issues) and has an involvement of both ITU-T and ETSI (www.etsi.org/tiphon). It addresses various inter-working scenarios between SCN and IP networks as well as functional layers. ETSI’s document ETR101 619 serves as a comprehensive reference for inter-operator accounting and charging in a multi-operator environment.

Niraj K Gupta