A study conducted by Indian Telecom market regulator, the Telecom Regulatory Authority of India, has established that mobile network congestion has become more severe in the first three months of current calendar year. It has resulted in increased call drop and cheap quality of voice over the line.

The regulator has found that the congestion levels were above the permissible limits at 76 places, as compared to 66 places last year.

The problem was reported to be more severe in Bihar, Andhra Pradesh, Kolkata, Assam and Himachal Pradesh. It evaluated the congestion levels at the points of interconnection (PoI) at which traffic exchange of different telecom operator's takes place.

Congestion level should be minimum for customers to enable them communicate with other networks in the given telecom circle.

According to the norms set by the regulator, congestion level of 0.5 per cent is allowed, which implies that one call should be dropped out of 200 calls made between two operators.

Bharti Airtel, after Tata Tele services, is found to be the lowest congested network. Meanwhile the country's Cellular Mobile Telephone Subscriber base increased to 391.76 million in March, as compared to 346.89 million in December 2008.