Deutsche Telekom, owner of T-Mobile USA, is in talks to buy MetroPCS Communications and combine it with T-Mobile, which could shore up two struggling US wireless industry players. T-Mobile is the fourth-largest cellphone company, with 33.2 million subscribers. With 9.3 million customers, MetroPCS is fifth. A deal would give T-Mobile more airwave space, a critical factor as cellphone carriers expand. Last year, regulators blocked number two AT&T from buying T-Mobile for $39 billion, citing the threat to competition.