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Sci Tech
Last mile connection goes digital
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Direct Internet Access System (DIAS) allows the user to access the Net at 128 kbps speed and makes it available on an `always on' mode. It allows the customer to use Internet and telephone simultaneously.
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ACCESSING THE Internet from the confines of one's home especially during the day can prove to be a test to one's patience. Excruciatingly slow connectivity speed makes accessing the Net a nightmare especially if the price one pays for the slow speed is also factored in. Worry no more as help is at hand.
Digital Internet Access System (DIAS), an indigenously developed technology has come as manna from heaven for those seeking increased connectivity speed. A brainchild of Padma Shri award winner Ashok Jhunjhunwala of Electrical Engineering Department, IIT Madras, the technology makes it possible to access the Net using the existing copper line at an all time high speed of 128 kilo bits per second (kbps).
DIAS is not about speed alone — it makes the Net available around the clock on an`always on' mode. The icing on the cake is of course the ability to use both the Net and telephone simultaneously — a facility that was so far denied to users with dial up connection. The Internet connectivity speed will go up four fold from less than 30 kbps in the of dial up connection to 128 kbps with DIAS. But, the connectivity speed drops to 64 kbps when the Net and telephone are used simultaneously.
Cost of connectivity is another feather in its cap. One hour of Internet usage through a dial up connection would cost around Rs 40. Though the Internet connection charge is just Rs 10 per hour, engaging the telephone line for one hour works out to nearly Rs 26. Dropped connections only add to the cost as the Internet Service provider (ISP) levies an additional charge every time a fresh login is made.
If proof of the pudding is in the eating then the intense customer demand in four exchanges in Kolkota where DIAS has been installed says it all. "The customers are happy with the technology and there is good demand for DIAS in these exchanges and elsewhere," said Somnath Maity, General Manager (Planning), Calcutta Telephones. Already one exchange has witnessed full capacity utilisation by customers. "We have placed orders for more DIAS systems to be installed in 50 telephone exchanges in Kolkata," he noted. A senior Bharat Sanchar Nigam Ltd (BSNL) official based in Delhi said that the customer response has not been very encouraging. The flat rate of Rs 1800 per month has proved to be a dampener especially with the residential customers. According to him a rental and usage based charging would prove to be an attraction to these low user customers.
BSNL has no inkling about the net usage pattern and finds itself constrained in introducing it right away. Nevertheless such a system is expected to be introduced in the near future.
DIAS uses the digital subscriber line (DSL) family of technology to facilitate carrying both voice and data (Internet). "Certain DSL technologies carry voice in an analogue form. But DIAS converts both voice and data into digital format," said K.V. Nair, Chief Operating Officer, Banyan Networks Pvt Ltd, Chennai. Banyan Network is the company that had developed the technology.
The customer premises equipment (CPE) installed at the customer's end has a digital modem with two ports that allow both the telephone and Internet to be used. The hardware in the CPE allocates 64 kbps for voice and the remaining 64 kbps for data. However when only the Net is used the hardware allocates 128 kbps for Internet using dynamic bandwidth allocation. But why is 64kbps allocated for voice when a lesser amount would suffice? "We could have used compression technology to reduce the allocation to 16-32kbps. But this would have increased the cost of the technology," Mr. Nair elucidated. Short durations for which the phone is used, he feels, does not necessitate going in for advanced technology which would jack up the price paid by the customer.
The highlight of the technology is its ability to use the existing copper line to transfer data at 128 kbps speed for the last mile connection from the customer's house to telephone exchange. DIAS uses symmetric data transfer based on the basic rationale that the quantum of data flowing from and to the computer is the same. It thus opens the door for high-end applications like Internet based entertainment, Net education, gaming, e-commerce to name a few.
Compare this with ADSL (asymmetrical digital subscriber line) that works on the premise that the data flow is asymmetric. That is, data accessed by a person is more than the data sent to the server. It works best for low-end Internet applications like normal browsing and e-mailing.
These advantages apart, DIAS unlike ADSL will be able to work on existing copper. This is not the case with ADSL as its performance is directly linked to the quality of copper. The poor quality of copper with inadequate twists and too many joints except in very select pockets will prove detrimental to its success.
Any number of twists either more or less than the prescribed number will affect the impedance and hence the quality of data flow. Likewise, joints also affect the quality of copper. These problems not withstanding the existing copper wires are able to carry voice as it is in the order of 4 KHz. All these make DIAS a better technology compared to ADSL.
"We developed DIAS considering Indian conditions and to serve Indian customers," Mr. Nair commented. Yet, it has its own share of limitations. It would not work beyond 5 km from a telephone exchange. "This is basically because the signals die beyond this distance. After all we are only coding the signals and the sensitivity comes down with distance," Mr. Nair explained.
The technology was first deployed by MTNL, Mumbai two years ago. Its installed capacity is nearly 2000 in 15 odd cities and has a customer base of 200. More cities would be offering this technology by this year end. Repeat orders from Kolkota, Gujarat, Karnataka, Maharashtra, Kerala and Madhya Pradesh only serve as a pointer to its acceptance by BSNL.
Apart from cost advantage, speed and `always on' features, the technology will witness growth and acceptance when various high-end Internet applications become a common place. "Dial up connection will remain as an entry level for accessing the Net but will not change the way the Net is being used for serious business," Mr. Nair noted. BSNL has about 38 million phone lines. "Even if five per cent of its subscribers go in for DIAS there could be an Internet revolution of sorts," he felt
R. Prasad
in Chennai
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