Japanese cellular carrier, NTT DoCoMo, is all set to invest $2.5 billion in Tata Teleservices, according to a Mint report. Tata Teleservices, the sixth-largest, cellular carrier in India, operates a CDMA network and is set to launch a GSM network soon. The $2.5 billion investment will give NTT DoCoMo a 26 percent stake in Tata Teleservices, hence valuing the company at $9.61 billion. Tata Teleservices claims to have about 29 million subscribers on its network.