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Issue of April 2003 
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Vendor Voice: Voice over IP
Making the most out of VoIP

Businesses can deploy new technologies like VoIP and yet protect their investments in legacy systems, using integrated solutions. by Rajesh Tuli

Convergence was the buzzword in the high-end enterprise market. Even as technologies became available across the world, there remained a wide gap between the availability of this converged technology and its actual application, because of the lack of broadband access in the country. So a majority of PBXs and DLCs (Digital Loop Carriers) remained pure voice switches.

Indian consumers have acknowledged the rapidly changing nature of technology and also the advantages each technology presents. With easier availability of broadband connectivity, the consumer expects premium data access services. But there is still a limitation on distance for transmission of high-bandwidth data over copper wire. So there was a need for a new generation of broadband DLCs, that would act as street cabinets to provide connectivity to various subscribers in the neighborhood. DLC is like a concentrator of telephony traffic. The distance limitation of carrying high-speed data on copper will see more systems acting as neighborhood nodes, or streets cabinets rather than central switches.

The challenge lies in effectively implementing a network that optimizes a variety of signals from voice, data and video services. The solution is to provide for adequate protection for existing investments in legacy systems while providing for seamless integration with high-speed data. That would enable existing networks to provide multi-service access platforms without congesting existing expensive networks deployed by telecom companies for toll quality voice services.

Hence these street cabinets will become even more intelligent and would provide a bouquet of voice and data services on copper wire to consumers. These street cabinets would concentrate voice traffic and divert it to main exchanges over fat voice pipes on copper. Street cabinets would also concentrate data traffic and intelligently separate it from the voice traffic, and may directly send it to the IP cloud, possibly via the main exchange.

Let's evaluate the various factors involved and the direction that the new generation switches are likely to take in the VoIP space.

VoIP (Voice over Internet Protocol) has been legalized in India for limited applications, but it would soon find acceptability as a prime mode of communication. This would make long distance telephony inexpensive, which means many are likely to make their switching platforms IP compatible. So far IP telephony is possible using expensive IP phones (Rs 2,000 onwards) or through PC based solutions. In comparison, regular analog phones are extremely inexpensive, so it seems as if IP phones will never replace analog phones.

In its present form IP telephony would require a separate network akin to LAN networks, using separate cabling. But for large-scale usage in corporate environments there would be a need to integrate these two forms of telephony so that a corporate executive has only one telephone on his table, and the switch would have to be intelligent enough to route a certain set of calls (long distance calls) on IP, and another set of calls on regular circuits. Similarly, all incoming calls, irrespective of the medium of transport, should arrive at the usual telephone instrument.

Presently data networks and circuit-switched voice networks are essentially independent units with limited interconnect. There is a great need to develop cost effective systems that would carry voice and data over the same existing set of copper cables—at speeds that would meet the requirements of data and voice communication within a corporate institution. The need for a transparent intermix is all the more evident as the transport cost of voice over data channels would be far lesser than its transport over dedicated circuit switched channels. This is because IP technology provides for packetization, whereby a given bandwidth is shared for multiple channels of communication. In a circuit-switched environment each communication channel requires dedicated bandwidth.

Despite the transport cost, the circuit-switched environment cannot be ignored because of the vast availability of this legacy telecom network, and also because the customer premises equipment on these networks are extremely cost effective. The telephone or device to convert the voice signal into a transportable form on circuit switches are much cheaper than their generic substitutes for doing the same on IP or data channels. Circuit switched networks have further advantages as they still offer supremacy in quality of service and also continuity of the same telephone numbering plans.

So there is a great need to provide total integration of the two networks so as to take advantage of cheaper transport on one side and of cost-effective end customer equipment like analog telephones, faxes and answering machines on the other hand. This should be possible on the existing set of telephone wires with transparent interconnect with the circuit switched world.

The solution to address the circuit switching and data switching needs of corporate business houses is to provide integrated solutions using a single device. This can be done using built-in VoIP cards for supporting long distance communication over Internet. These VoIP cards have powerful DSPs for doing voice compression, echo cancellation, comfort noise generation and packetization. Gateways and gatekeepers based on H.323 are built into these cards. The gatekeeper software handles the routing of voice packets to various destinations through the Internet. Various applications like least cost routing, private networking, etc can be implemented using these VoIP cards. Using these VoIP cards, it has become possible to reach any extension in the switch, from any part of the world, through the Internet.

As a concept it is about developing the packetizing capability into the switch itself, so that it is used as a shared resource instead of providing this capability at the customer end, as in SIP or H.323 devices. It is this concept of shared resource development that will bring down the costs. The VoIP card along with the simple telephone instrument can be compared to the SIP or H.323 device.

The switch will essentially have the router capability, whereby it would allocate IP addresses to each analog and digital extension user to be able to integrate data switching and dynamic bandwidth allocation to the user extensions. Such router capabilities providing independent IDs can have additional advantages like setting up a pool of extensions for receiving fax, voicemail or modem calls. Router capabilities would further allow telephone and data calls to be routed by name as well.
Such voice and data servers would essentially shrink the telecom world much the same way as Internet has brought people together. Once the switch is connected to the IP cloud there is no significance of distance.

Most businesses would prefer to use VoIP as the preferred mode of communication for long distance telephony. This is the only integrated solution that does not require a separate data network for VoIP calls and would allow usage of existing low cost analog telephony equipment for transparently receiving or making calls. Alternate solutions are expensive requiring separate data networks using computers with multimedia kits or IP phones for voice communication, which makes the solution not only expensive but also difficult to operate as the user will have to make and receive calls from the circuit-switched world on separate telephones. The solution will be intelligent enough to automatically route certain calls over IP networks and others over circuit switched channels. It will use the same telephone instrument for accessing both channels hence eliminating the need for separate networks.

The writer is CEO, Coral Telecom. He can be reached at

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