India’s success over the last one and half decades in providing high quality software professionals to the world has prompted us to take a relook at ourselves. The question that is being asked is whether we can sustain this success and make it grow – can IT in India become a force to reckon with in the world? The IT Task Force has recently set a yearly revenue target of Rs.400,000 crores from this industry. Is it realisable? Can we have a few million people working in this industry in the next five to seven years? Can this industry be used as a spring-board for India to get into the forefront of modern technology?

These and many other similar questions are indeed being raised. But will these goals remain a mere dream or become a reality? This paper looks at one of the many, and probably one of the more important tasks that needs to be carried out for achieving such a goal – the task of providing an affordable telecom and Internet network all over India. Without wide-spread access to the telecom and Internet networks, one cannot even dream of expanding our IT industry.

The reality today is grim. We have less than two telephones per hundred population, (as opposed to one for every two persons in the developed world). The Internet, which is the crucial component in today's IT revolution is accessible today only through a telephone. The number of Internet connections in India has barely crossed 200,000. There is a yearning for more telephones and Internet connections. But will this yearning be satisfied?

Not many of us know that today it takes approximately Rs.35,000 to install a new telephone connection in India (this is per-line cost of the complete telecom network). Assuming 15% as finance charge on such an investment and even a low figure of 15% for operation, maintenance and obsolescence cost, and assuming no other charges such as license fees, connectivity costs etc., it would require 30% of Rs.35,000 per year, or approximately Rs.10,500 per year of revenue from each telephone, just to break even. How many in India can afford to pay such a large telephone bill? Is it more than 2–3% of our population? How then can we carry out an IT revolution?

Let us look at the way Internet access is provided today. One has to buy a modem and connect a computer to a telephone line. Then one dials an Internet Service Provider’s telephone number and gets connected to an ISP router, which connects one to the Internet. This seemingly simple technique has a number of pitfalls.

How do we expect to provide Internet connectivity to "millions" in such a situation? The high investment required to install a telephone line and the problems of providing Internet service on such a telephone network make our task very difficult. What is the solution?

Such complex problems do not have easy answers. The TeNeT (Telecommunication & Computer Network) Group of IITM has been groping hard for some answers to these questions over the past few years. We present in this paper our thoughts on the approach that needs to be taken towards solving such problems. We have pursued this approach over the years and this paper will briefly describe some of the systems and technologies developed under the leadership of the TeNeT Group, which could contribute significantly towards the solution. However, it is appropriate to point out that neither the approach suggested nor the technologies developed are sacrosanct. Many such efforts and multiple such answers are needed. We hope that the efforts of the TeNeT Group will add to other efforts in the country to enable installation of several hundred million telephone and Internet connections in India.

The reason that the cost of installing a telephone line in India is close to Rs.35,000 is because this cost is around $1,000 in the West and we have by and large imported the technology as well as the approach to build the telecom network. In the West innovations were used to bring down the cost per line of the telephone network. However, once the cost came close to $1,000 per line, with the economics and affordability in the developed economies being what it is, telephones became available to most people. It made little economic sense to bring down the cost further at this stage. The R&D efforts were therefore directed to increase value for money, and provide more features and services at the same cost. The emphasis, rightly enough, shifted to providing mobility, higher bandwidth and other features.

The requirements in India are different. Telephones at Rs.35,000 are affordable only to a few. Our approach therefore has to be different. We need to use technological advances to reduce costs further and make telecom widely affordable in our country. We need to bring down the cost to say, Rs.10,000 per line. At such a cost, the revenue required per line would be barely Rs.250 per month, which would be affordable to 100–150 million of our people.

Now, such a drastic reduction of per-line costs while also providing affordable Internet access is difficult and will take time. But with rapid enchancements taking place in telecom technologies, it appears a worthwhile task for the R&D community in India. R&D tasks are by their nature not easy and Indian Telecom professionals should welcome such challenges.

A key to solving the Internet tangle lies in the differences between voice and Internet calls. First, a little more detailed examination of the telephone and Internet traffic reveals that the average Internet traffic is very unlikely to exceed the voice traffic. During a voice conversation, the traffic is pretty much at full rate at all the time. Therefore a 64 kbps voice call for about 6 minutes in an hour (0.1 E)is expected to generate a total traffic (each way) of 64 ´ 60 ´ 6 kbits or approximately 2.9 Mbytes of traffic. The telephone network is designed to handle such traffic per line.

Now, let us look at Internet traffic. Assume the line is used throughout the busy hour. This is the worst case – in reality the data Erlang is about 0.15 – 0.3 E. But Internet traffic is not constant or continuous. Instead it is bursty. A burst of data is transmitted as a packet at the peak rate of 64 kb/s and then the line is quiet till a response is obtained. Even after the response is obtained, the user takes time examining the received data on screen before transmitting fresh packets. No data is normally received during this time Rarely is the actual data transmitted, in a long session, more than 10% of the peak rate. Thus taking 10% burstiness, the total data transmitted (each way) on an Internet connection would rarely be more than 64 ´ 60 ´ 60 ´ 0.1 kbits or 2.9 Mbytes.

This is indeed a revelation. Internet traffic is not more than voice traffic even in the worst situation. Therefore for Internet access at upto 64kbps, existing telephone network has the traffic carrying capacity. The problems that the telephone network is circuit-switched. Voice communication from one line occupies a PSTN circuit for only 10% of the time even during the busy hours. An Internet session, on the other hand, could occupy a PSTN circuit nearly 100% of time in a busy hour, whether data is actually being transmitted or not. This could result in excessive congestion and even a collapse of the network.

The solution will be to find a way of not occupying the telecom network resources 100% of time for Internet access. If a way is found to statistically multiplex Internet traffic from several on-line users and then carry the traffic through the circuit switched network, the ubiquitous telephone network would be capable of handling long Internet sessions. The key is that such multiplexing be carried out in the network as close to the users as possible. Such an approach has been used in the systems and technologies developed by the TeNeT group in recent years.

In recent years, developments in the area of fibre optics and microwave radio technology, have reduced the cost of the backbone telecom network to about Rs.1,000 – 1,500 per line. Similarly with the access network getting separated from the exchange, the cost of the main exchange today is around Rs.1,200 per line. The key contributor to the telecom network cost today is the access network, which is sometimes as high as Rs.22,000 in urban areas. The cost in rural areas may be several times higher.

The TeNeT Group and its associates has developed a Fibre Access Network (optiMA), Wireless in Local Loop system (corDECT) and a Direct Internet Access System (DIAS), which aim to significantly reduce access cost and at the same time enable large scale usage of Internet. Using these technologies it is possible to set up a total network today at an average cost of Rs.16,000 per line. These systems flexibly enable rapid expansion of the telecom and Internet network both in urban and rural areas. Let us first take a brief look at these system technologies.

optiMA Fibre Access Network

This fibre-to-the-curb (or street-corner) system provides one of the most cost-effective means of deploying telephones especially in dense urban areas. The system consists of a Remote Terminal (RT) deployed at street-corners as shown in Fig.2. The single cabinet with a built in power plant and battery, serves about 500 subscribers and could be located at a PCO or a street-corner kiosk. The subscribers are connected to the RT on copper (either POTS or ISDN) or on wireless (the last 500-800 m). The RTs on the street-corner are connected to a Central Office Mux (COMUX), located at the main exchange premises using a fibre-optic ring as shown in Fig.3. The ring network enables the system to withstand any single failure of fibre link. The COMUX is connected to the main exchange on standard E1 lines using V5.2 protocol and to the radio exchange (DIU) to serve wireless subscribers. As shown in Fig.3, a Remote Access Switch with Modems (RASM) connected to the main exchange on E1 would ensure that Internet traffic from different users are statistically multiplexed before entering the backbone telecom network. The RASM also enables a guaranteed 56 kbps Internet connectivity as the analog portion of the loop is now reduced to 500 - 800m. The cost of the POTS access solution using optiMA is astoundingly low, approximately Rs.7,500 per line. The wireless connection would cost around Rs.13,000 and the use of multiwallset providing connections to four subscribers in a building would bring down the cost to around Rs.7,000 per line.

corDECT Wireless in Local Loop system, based on the DECT standard, has an interesting architecture, especially for its fixed part. The fixed part consists of a DECT Interface Unit (DIU) acting as a 1000 – line wireless switching unit providing a V5.2 interface towards the main exchange, and weather-proof Compact Base Stations (CBSs). These are connected to the DIU on either three pairs of copper wire carrying signal as well as power, or fibre/radio using E1 links through a base station distributor (BSD). The subscriber terminal is a wallset (WS), with either a built-in antenna or a rooftop antenna providing a line-of-sight link to a CBS. The WS has an interface for a standard telephone (or fax machine, modem or payphone) and an additional RS232 interface for a computer, enabling Internet connection at 35 or 70 kbps. No modem is required for Internet access, since all links between the WS and DIU are digital, as shown in Fig 4.

Efficient transmission of packet-switched Internet data on a circuit-switched network is achieved by combining a RAS with the corDECT system. The connection is digital all the way from subscriber to ISP. The Internet call from a WS to a RAS does not enter the exchange at all, but terminates in the access network itself. Only the concentrated IP traffic from the RAS to the ISP traverses through the exchange and PSTN.

All subsystems are built primarily using digital signal processors (DSPs), with the DIU having nearly 100 DSPs. This soft solution, while cutting down development time and affording design flexibility, also ensures that the cost of the fixed part is no more than 15% of the total per-line cost in a fully loaded corDECT system. This allows deployment flexibility for both dense urban and sparse rural areas.

A new operator who wishes to initially deploy 5,000 lines in a mid-sized town or city in the very first year would use the deployment scenario shown in Fig.5. All the DIUs are collocated with the main exchange and connected to it using the V5.2/E1 interface. Each DIU is connected to a BSD located on a rooftop at a suitable part of the town using a point-to-point 8 Mb/s microwave link. At the BSD site, a cluster of about 12-15 CBSs (each serving 50-70 subscribers at 0.1 Erlangs each), along with the microwave equipment, are mounted on a 15m rooftop tower to serve an area of 2-3 km.

This deployment uses no cables and can be made operational in two to three months at a total deployed cost of Rs.15,000 per subscriber.

Later, the operator could increase the number of lines by using an optical fibrE grid to connect BSDs to the DIUs. A CBS cluster now serves 1,000 subscribers within a 700m to 1 km radius. Here, many subscriber installations may not need line-of-sight links to the CBS. Once again, the total deployed cost of the access solution is under Rs.15,000 per subscriber, including the cost of optical fibre cable and cable-laying.

The corDECT system also offers an excellent deployment opportunity for a small town and its surrounding rural areas at a similar cost. The mode of deployment is similar to that in Fig.5, except that the DIU itself is at the tower base and there is no BSD. To serve about 1,000 subscribers, an operator needs a tower (about 35m high) in the town centre. The microwave link connects the DIU to the nearest trunk exchange. The base stations now serve subscribers within a radius of 10 km using wallsets with rooftop antennas providing line-of-sight links.

Deployment in sparse rural areas is possible using the corDECT relay base station (RBS). A two-hop DECT link is used to provide connection to the subscriber. One link is from the WS to the RBS, which is mounted on a tower typically 25m in height. The other DECT link is from the RBS to CBS, which is also mounted on a tall tower (say 40m). Both the RBS and CBS use high-gain directional antennas, making a 25km link possible. The 5km maximum link distance due to the guard-time limitation of DECT is overcome by the use of auto-ranging and timing adjustment. This technique is used in the RBS to support a 25km link, and to enhance the CBS range to 10km. This provides a subscriber density as low as 0.5 subscriber/km² at a total cost of Rs.18,000 per line.

The Direct Internet Access System (DIAS) allows service providers to provide high bandwidth Internet access to residential and corporate subscribers, in addition to voice services, without any changes to the existing cabling infrastructure. In contrast to current residential PSTN (Public Switched Telephone Network) and ISDN (Integrated Switched Digital Network) dial-up access, the DIAS provides an Always On Internet Access that is permanently available at the customer's premises. Using DSL techniques, seamless voice and data connectivity is provided to the customer over the same pair of copper wires.

Implementation of this system is done using the existing cable plant. All that is required is the installation of the IAN (Integrated Access Node) at the exchange and a DSU (Digital Subscriber Unit) at the customer premises.

The DIAS has a DSU that combines voice and data packets on a single twisted-pair wire at the subscriber's premises. At the service provider's premises, an IAN separates the voice and data traffic from a number of subscribers and routes them independently to the PSTN and the Internet respectively. The IAN is connected to the PSTN via the E1 V5.2 port, and to the Internet either through 2 E1 data ports or through the Ethernet port. Alternatively, the PSTN connectivity can be achieved through the POTS ports of the exchange with the addition of an optional subscriber multiplexer module, that converts a single E1 line into multiple POTS lines.

The DIAS system provides 2 types of voice and data services:

• The BDSU (Basic Digital Subscriber Unit) is designed for the SOHO (Small Office Home Office) and residential Internet user. It provides a permanent Internet connection at a maximum data rate of 144 Kbps, which drops to 80 Kbps when the telephone is in use and transparently goes back to 144 Kbps when the telephone is not in use.
• The HDSU (High bitrate Digital Subscriber Unit), which is designed for corporate subscribers, can provide voice connectivity for upto 8 telephones and a permanent data bandwidth of upto 2 Mbps, which drops by 64 Kbps for each telephone call.

Deployment in Urban and Rural Areas

The technologies and systems described above, used along with standard PDH and SDH fibre-optic and microwave links and widely-available main exchanges and routers, enable flexible planning and rapid commissioning of a telecom and Internet network in both urban and rural areas. The examples described here will illustrate this.

But before we proceed, let us describe what we call an Access Centre (AC). The Access Centre is a self-contained unit which could provide voice and Internet connectivity to subscribers using either plain old copper, wireless or using DSL on copper. It combines corDECT, optiMA and DIAS access systems today and has the capacity of including other access systems tomorrow. Fig.7 shows one such Access Centre. It is a single cabinet with a built-in power plant and battery back-up. corDECT BSDs are mounted in the cabinet to drive base stations and thereby provide wireless connectivity to subscribers. OptiMA RTs or Versatile Remote Unit (VRU) provide POTS connectivity within a radius of a kilometre. Similarly DIAS IANs provide voice as well as Internet connectivity using BDSUs or HDSUs. Some Access Centres would also contain a DIU to which the BSDs in other ACs are parented. The Access Centre has been designed to be housed in a small 100 sq.ft. room and could easily be used by a franchise operator to provide service in a neighbourhood.

A telecom and Internet network would contain a Switching Centre connected to several Access Centres using either PDH/SDH microwave or fibre links connected as shown in Fig.8 or as a ring. The Switching Centre would consist of a main exchange, Internet routers, some Remote Access Switches and a Network Management system to manage the network. The Switching Centre would be connected to a national and International Internet network, national and international voice network as well as to the other switching centers of the operator located in other cities/districts.

The network described above is versatile, flexible and expandable. It provides different kinds of services including voice telephony, dial-up Internet connection and permanent Internet connections. The network can be deployed in large cities, in small towns and in sparse rural areas using the corDECT Relay Base Station.

Fig.9 shows the typical deployment in a large urban centre. Access Centre are located at about 20 places, each serving roughly an area of 1.6 ´ 1.6 km. About 1,000 subscribers are provided connectivity from each Access Centre. To start service quickly, a few ACs can be connected to the Switching Centre using point-to-point 8 Mbps radio links. In the mean-time, the work on a fibre-optic SDH ring network would commence to connect all the AC to the Switching Centre. It is possible to provide 20,000 subscribers connectivity in this manner in about a year at a cost of Rs.20,000 per line. With larger deployment, the cost would decrease. It is important to note that this network not only provides voice but also Internet connectivity without loading the telephone network. This is because most of the Internet traffic is seperated at the Access Centres and carried from thereon on a packet-switched network.

Fig.10 shows a plan of a similar network designed for a rural area. Thanjavur is one of the better-off districts of TamilNadu with rich agricultural land. The proposed network consists of two Switching Centres located at Thanjavur and Kumbakonam cities. Several Access Centres are located in small towns all over the district. Each AC serves not only the town, but also the surrounding rural areas. By using Relay Base Stations, a subscriber can be provided both voice as well as Internet connection as far as 25kms from the town. The ACs are connected to the Switching Centres using point-to-point microwave radio link. Once again, about 15,000 subscribers can be served all over the district at a cost around Rs.20,000 per line. The network can be set up in about a year.

For voice and Internet connectivity to become widely affordable and available, countries like India need a telecom network that costs much less than what prevails today. Such cost reductions are possible if one innovatively utilises the continuing technological developments in this area. Indian scientists and technologists have the capability of taking up such a challenge. Besides, if one is able to reduce the cost considerably, the market size in developing countries is huge. In fact, it much larger than the current market in the developed world. The Government, the planning bodies, industry and R&D organisations have to get together to take-up such a challenge. The task will not only bring out the very best from within us, it will also be exciting and sufficiently rewarding. Further, success in this endeavour could propel India into the front-ranking countries of the world.

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