Tata Teleservices has hit back at cellular operators by submitting videos to the Telecom Regulatory Authority of India that apparently show Delhi's cell firms offering coverage beyond their licensed areas.

The move comes after Hutch had submitted similar videos showing Tata Teleservices and Reliance Infocomm offering limited mobility services beyond the permissible limits of a local call area.

In a communication to Trai, Tata Teleservices has said spillage of signals from one telecom circle to another is a normal phenomenon in WLL and cellular services.

It goes on to say, "In case of GSM operators, the spillage of signals is an accepted fact across the world. Even in the Delhi telecom circle, the signals of licencees of the Delhi circle are found in the border areas of the adjoining circles beyond their licence areas. This would confirm that cellular operators are still facing similar signal spillage problems despite the much greater number of subscribers they have on their networks."

Tata Teleservices, which offers limited mobility services under the brand name Tata Indicom, has pointed that the videos were merely in support of its claims that radio frequency spillage was "unintentional and not peculiar to our network only."

Radio frequency is dependent on several factors such as topography, irregular demarcation of calling areas and traffic density.

It was almost impossible to abruptly limit the propagation of signals within a specific distance or draw a specific boundary, the letter explained.

Maintaining that it was offering services as per licence conditions, Tata Teleservices said the service provider either had to configure its network in such a manner that the signals faded away in the border areas, resulting in poor quality of services in these areas, or provide service with optimum signal strength and meeting service levels stipulated by Trai, which would result in some amount of signal spillage into the adjoining areas.

Tata Teleservices has said since it has a subscriber base of 50,000 users and a capacity for 150,000, "with further growth of subscribers, the overall footprint of the (Tata services) should shrink to cover only Delhi."