Regulator Trai has found leading mobile operators such as Airtel, Vodafone and state-run BSNL using the Radio Link Time-Out technology at high levels, a network parameter allegedly being used for masking call drops. A Trai report on network drive tests conducted in Hyderabad said "11 out of 14 networks" tested failed to meet call drop benchmark set under service quality norms. The report said that 2G networks of Bharti Airtel, Vodadone, state-run BSNL, Tata Docomo and Telenor have set higher RLT (radio link time-out) values than other operators. RLT is one of the parameters which decides for how long the call should be sustained if the signal quality drops below a certain threshold. However, official sources have claimed that telecom operators are using the technology for masking call drops to escape heightened vigilance by the regulator. This is also resulting in higher bills for subscribers. The drive test found that leading telecom operators have set RLT values well above 40 level. "Vodafone 2G and Telenor 2G would also exceed the benchmark if RLT (radio link time-out) of 40 is assumed. With RLT as 40, Call Drop Rate will increase to 2.2 per cent for Vodafone 2G and 2.7 per cent for Telenor," Trai said in its drive test report released today. The regulator said that call drop rates for Airtel and Docomo will also increase if RLT of 40 is considered. However, for state-run BSNL it said that the company was using RLT value higher than 40 at around 35 per cent of its mobile sites but it did not encounter any scenario where the value was breached. This is second city where Vodafone has been found using RLT parameters more than its peer networks. Previously, the drive test was conducted in Delhi, where Vodafone and Aircel were found using such technology. The drive test found three areas in Hyderabad Banjara Hills, Secunderabad and Gandhamguda accounting for about 60 per cent of total dropped calls. "On excluding the dropped calls in above mentioned areas, call drop rate benchmarks are met (or are close to 2 per cent) for all operators," the report said. The regulator also found 3G connection of Idea Cellular hooked on to its 2G network most of the time depriving benefit of high speed data to its subscribers. "On its (Idea) 3G enabled SIM card, most idle time was spent on 2G network. Most calls were thus initiated on its 2G network. This aspect could be an issue for a 3G user who would not be able to avail 3G data service, for a major period," the report said. The test was conducted between May 5-7, 2016, covering an area of 300 kilometer.