IIT devises wireless internet access system

The WLL system is cheaper than wired lines and provides internet access at 35 kilobytes per second kbps. It can be upgraded to provide access at 70 kbps and does away with the problem of telecom network congestion, Ashok Jhunjhunwala, professor at IIT8217;s Department of Electrical Engineering, said.

The system was unveiled during the science congress in Chennai in January where it provided instant telephone and internet access to the participants over the entire Anna University campus. Its details were reported at recent conference on communications technologies here.

The Mahanagar Telephone Nigam Limited MTNL has placed orders for two trial systems in Delhi and Mumbai, according to scientists who demonstrated the system.

It allows the subscriber to connect to any telephone or facsimile machine. Internet access is provided without the need for a modem by directly connecting the personal computer to the WLL subscriber terminal.

The system incorporates a remote access switch which helps reduce congestion in the network while the net is being accessed.

In current systems, an internet user blocks the line from the time he connects and browses the net to the time he downloads the required text.

Internet calls are of long duration, and each of them holds up the circuit from the subscriber all the way to the Internet Service Provider ISP, Jhunjhunwala explained.

This results in congestion in the trunk route between the subscriber8217;s exchange and the ISP8217;s exchange which is designed for short-duration voice telephone traffic. Also, the subscriber pays the telecom charges for the duration of the call.

In the WLL system, the subscriber is connected to the RAS, which is linked to the internet service provider. All calls from the internet subscribers terminate at the RAS, which is placed at the subscriber8217;s exchange.

The RAS multiplexes or simultaneously transmits several data over a single carrier, reducing the trunk network congestion considerably.

Since the trunk network is not used by the subscriber and the call terminates at the RAS itself, the call charges for internet access can be reduced, Jhunjhunwala said.

An additional advantage with the IIT8217;s WLL system is that the line is free to make and receive telephone calls even when the internet is being accessed, he said.

However, if the RAS is used with conventional wired lines, voice calls cannot be made or received when internet access is on.

The IIT8217;s RAS costs far less than imported products available today, Jhunjhunwala said.

He said the IIT system can be deployed in urban areas with high subscriber density, as well as sparsely populated rural areas with low subscriber density. It is weather-proof and easy to install and maintain.

IIT8217;s WLL system is based on digital European cordless phone technology devised by the European Telecommunications Standards Institute.

It comprises a control system called DECT Interface Unit DIU that interfaces with the local exchange, base stations that transmit signals, wall sets that receive signals from the base station and the user hand sets. The telephone, fax or modem can be connected to the wall set.

Each system consists of one DIU linked to upto 20 base stations, which are in turn connected to 1,000 wall sets.

For internet connection, each DIU is linked to two RAS, which are connected to four or five subscribers. The RAS maintains a consolidated link with the ISP.