The company's predecessor, VoiceStream Wireless, began building a regional, 2G , 1900 MHz GSM, circuit switched, digital cellular network in 1994 and first offered service in 1996 in Honolulu and Salt Lake City . From that starting point, the network has expanded in size through acquisitions of other cellular-network operators and additional spectrum purchases. The network has also expanded in capabilities through the introduction of new technologies. VoiceStream upgraded the 1900 MHz network to include packet switching via General Packet Radio Service (GPRS), then increased packet switched data transmission speeds via Enhanced Data Rates for GSM Evolution . In 2006, the company spent $ billion to purchase 120 D, E or F block 1700 MHz AWS licenses  and began rolling out 3G UMTS services in those frequency bands. The company upgraded network equipment and back-haul capabilities to enable HSPA (High Speed Packet Access), and later HSPA+ and LTE services.