Simultaneous access to Internet and telephone may soon become a reality

THERE IS good news for some Internet users in Chennai and Bangalore. About 1000 Internet users in the St. Thomas Mount telephone exchange in Chennai and 500 Internet users in R. T. Nagar telephone exchange in Bangalore, would soon have the facility of accessing the Internet and using the telephone simultaneously at any given point of time. The facility is already in place at Koppam some 250 km from Chennai, making 45 villages Internet ready through wireless.

The possibility of simultaneous access to Internet and telephone is in stark contrast to the prevailing situation where only one facility can be used at a time. This technology to be implemented by the Department of Telecommunications (DOT) in the two exchanges will be made possible using the CorDECT Wireless in Local Loop (WLL) jointly developed by five Chennai based companies, namely Midas Communication Technologies Pvt Ltd, Banyan Networks, Vembu Systems, Niligiri Networks and Polaris Software Laboratory along with the Indian Institute of Technology, Madras.

The CorDECT WLL technology essentially has a wall set which has either a built-in antenna or a rooftop antenna at the subscriber's end connected to the compact base station (CBS) which in turn is connected to the telephone exchange through DECT interface unit (DIU). A compact base station is designed to serve 1000 subscribers at a time. A proportional increase in base stations can meet the demands of a growing number of subscribers.

"We will be able to serve two kinds of subscribers with this technology - one where the wall set is connected to the base station through wireless and the other in which the wall set is connected to the existing land line (telephone connection). And in both cases we will be able to provide simultaneous voice and Internet connectivity," said Mr. Purohit B. Purohit, Director of Midas Communication Technologies. It will use the 1800-1900 MHz bandwidth.

Choice of connectivity

In the case of wireless connectivity to the base station, the subscriber has a choice of selecting either a 35 kbps (kilo bytes per second) or 70 kbps. In the case of the 35 kbps there is only one channel provided to the subscriber but another channel is established the moment both Internet and telephone are used. This enables the simultaneous use of both the facilities at any point of time. But in the case of 70 kbps connectivity, the subscriber is provided with two channels. The speed of Internet connectivity is 70 kbps when used independently and 35 kbps when the telephone is also used.

In the case of a wall set connected to the land line there are again two kinds of services provided. The 144 kbps connectivity has a facility to serve one telephone apart from the Internet and the other with 2 mbps connectivity with a capability of serving up to eight telephone connections. As in the case of wireless connectivity, the speed of Internet access drops when the telephone is also used. With the 144 kbps connectivity, the Internet access speed slows down to 80 kbps when the telephone is also used and 1.5 mbps when all the eight phones are used simultaneously with 2 mbps connectivity.

But how is it that the telephone connected through land line uses 64 kbps while only 35 kbps is required in the case of wireless connection? "We save on bandwidth by compressing it using certain coding techniques. This compression makes it possible to transfer lesser number of symbols," Mr. Purohit said. Apart from the speed of access, the technology will help save money for the subscriber if the wireless connectivity is used as he totally bypasses the DOT and the therefore the inflated telephone bill.

A base station has 120 channels and can meet the requirements of 1000 subscribers. "This number was arrived at considering that not all the subscribers will be using the telephone and Internet at the same time," Mr. Purohit said. The maximum distance that a base station can serve is 5 km line-of-sight but the number of base stations that will be set up even within 5 km will depend on the number of subscribers.

Will the Internet access through cable network be a better choice compared to the corDECT WLL technology? Mr. Purohit does not think so. "First of all cable connectivity will take time to take off in India.

Again the quality of the reverse path in a cable network will determine the quality of cable Internet. But very importantly, cable Internet shares the bandwidth giving scope for reduced speed of connectivity when more users access the Internet," Mr. Purohit said. CorDECT WLL technology on the other hand can maintain the same speed of access even when all the subscribers are logged on to the Internet as each subscriber has a dedicated channel.

Similarly, will Reliance Industries which has plans to lay a fibre optic cable from Maharashtra via Karanataka and Chennai to Singapore prove a threat to the acceptance of CorDECT WLL technology? Dr. Ashok Jhunjhunwala, Telematics & Optical Communication Laboratory, IIT, Madras, feels otherwise. "Fibre optic cable will be our backbone. All our DECT interface units (DIU) will be connected to the telephone exchange using fibre optics. But access to individual subscribers will be through wireless. So fibre optics will only complement and help the growth of our technology," he said.

"For a city like Chennai a wireless connection would be able to meet the demand of 1-1.5 lakh subscribers if the base stations are installed at 1 km radius. It can go up to 2.5 lakh subscribers if it they are installed at 500 metres radius," said Dr. Jhunjhunwala.

But to begin with, he feels the base stations would be installed at 1 km radius. "Initially the base stations would be installed in clusters at one point instead of being put up as individual units. Clustering a few base stations in lieu of spreading them out would work out feasible," he said.

Apart from the technological advantages, it will help DOT save on the cost of connection to new subscribers. This technology will cost about Rs12,000-15,000 per line in urban areas and Rs15,000- 18,000 in rural areas compared to DOT's present expenditure of Rs35,000 per connection in urban and Rs. 75,000 to Rs. 1.3 lakhs in rural areas.

While installing the wall set for existing subscribers will involve DOT, the spread of this technology will not face a bottleneck even if DOT exhibits a lackadaisical attitude. Internet service providers can always use this technology to connect its subscribers.

Such a move will prove to be the icing on the cake for the subscriber, as Internet access will not increase his telephone bill. "Satyam Infoway has shown a great deal of interest in our technology," Mr. Purohit said. It plans to use this technology in Hyderabad and World-Tel Communications may use it in Chennai. A bright future seems to finally beckon this technology that was for long bogged down by bandwidth allotment problems.

R. Prasad

Chennai

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