In cellular radio, referring to systems based on the first digital standards, including Digital-AMPS (D-AMPS), Global System for Mobile Communications (GSM), Personal Digital Cellular (PDC), and Personal Communications System (PCS). See also cellular radio, D-AMPS, digital, GSM, PDC, and PDH. 2.5G (Two point Five Generation) In cellular radio, referring to digital systems and standards that are midway, or transitional, between 2G and 3G. Such systems include Enhanced Data rates for GSM Evolution (EDGE), General Packet Radio Service (GPRS), High-Speed Circuit Switched Data (HSCSD), and Universal Mobile Telecommunications System (UMTS). See also 2G, 3G, cellular radio, digital, EDGE, GPRS, and HSCSD.