The Minister of State for Communication and Information Technology, Shri Milind Deora today informed Rajya Sabha in written reply to a question that though MTNL is, in general, meeting the Quality of Service (QoS) benchmarks prescribed by Telecom Regulatory Authority of India (TRAI) in respect of mobile services, some complaints of subscribers are received. These complaints, as and when received, are attended to promptly by MTNL.TRAI has mandate to monitor the Quality of Service and conduct the periodical survey, in accordance with the provisions of TRAI Act. As per TRAI Report on QoS parameters for quarter ending March, 2011, the call drop rates in respect of MTNL in Delhi is 1.60% against TRAI specification of < 2%. Quality of Service (QoS) improvement is a continuous process. To further improve the QoS, measures like BTS addition, capacity augmentation and upgradation, antenna tilting, optimization of network and drive test are undertaken on a continuous basis by MTNL.