The Hindu Business Line : Use telecom copper cable for data access: Expert

ADVANCEMENT of technology has not translated into higher data rates and cheaper access to packet data network, including Internet, from landline telephone.

Nothing much has been done either to exploit the possibilities of the existing twisted wire copper pair in the last mile, says Mr P. Abraham Paul, a telecom consultant with 45 years of experience in the field.

In any fixed network system, the telephone subscriber's cable network contributes up to 80 per cent of the cost.

With increasing competition from wireless networks, service providers of wired line systems such as BSNL and MTNL are struggling to retain their customers.

Although they have a good scope in the copper connectivity to their subscribers, it remains massively underutilised.

With some ingenuity and purposeful thinking, these copper wires can be converted into badly needed data access links for home and business users. The technology for this is readily available, too.

The coder-decoder (Codec) device in the line interface at the telephone exchange has been found to compress the data handling capability in the last mile from 64 kilo bits per second (kbps) to just within the range of 4 kbps to 6 kbps. A Codec device is used in the digital exchange to convert analogue speech and signal content to digital information.

Mr Paul told Business Line that the telephone exchanges are necessarily designed to take care of the telephone call traffic during the busiest part of the day.

The number of switching paths and resources required in the telephone exchange and the system capacity are decided on the possibility of simultaneous call attempts and the average occupancy of the resources to optimise the cost of the system.

The telephone call traffic is the product of the `number of call attempts' and the `average occupancy' of the resources involved in the calls.

The average holding time of a voice call is around 60 to 90 seconds. (This average holds good for both successful and unsuccessful call attempt durations).

The average holding time of calls connected to Internet Service Providers (ISPs) is around 300 to 900 seconds.

The higher usage time is due to high access time, peripheral functions, low bit rate in the last mile and inefficient network elements.

The landline exchanges currently use the same `circuit switched' paths for voice calls and for calls getting connected to ISPs. So, the increase in average holding time of the calls to ISPs has direct impact on the system. The impact is low as far as the proportion of calls to ISPs is comparatively small, done during `slack hours' where the systems have enough spare capacity.

The impact is severe when a significant portion of the subscribers accesses the Internet during the high traffic hours and when the system works on its optimum capacity.

Normally, the systems are designed to cater to a 30 per cent of overload during the busy hour. If 5 per cent of the subscribers use the Net during the busy hour, it will consume this 30 per cent overload reserve capacity and any higher load will result in system congestion.

To give circuit switched Internet access to 20 per cent of subscribers, the system capacity needs to more than be doubled, which, however, is not economically viable or technically feasible. Therefore, no telecom company can afford this method to provide Internet access to bulk customers.

The end result is that Internet telephony is not taking off according to the need of the day. Also, users are charged exorbitantly for the higher access duration due to snags in technology implementation by the telephone service providers.

In order to make maximum possible use of the expensive copper wire pair readily available in the last mile, it is necessary to develop cheaper digital phones that can convert voice energy to digital information and transport it over frame relay to the exchange.

Asynchronous Transfer Mode (ATM) switching mechanism can switch and transit the digital information across the network. It can also directly handle bulk amount of digital streams multiplexed into STM (Synchronous Transfer Mode).

It is not practical to totally replace existing analogue phones in one go. The viable alternative is therefore, to provide add-on desktops at user premises to enable digital devices to pass digital information over TCP/IP interface to the line bypassing the analogue phone.

Similarly, at the telephone exchange end, the digital information bypasses the voice switching system and is handled by TCP/IP servers or directly by ATM Switches.

These systems are readily available and being used in the GPRS (General Packet Radio System) in the GSM network.

Switching systems using different technology are also available and being used in landlines also.

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