| 单词 | 32 |
| 释义 | 32 communications channels are split into 30 kHz voice channels using frequency modulation (FM). As an analog system, AMPS derives channels using frequency division multiple access (FDMA) and bidirectional communications is achieved through frequency division duplex (FDD) with the downlink in the 869–894 MHz band and the uplink in the 824–849 MHz band. AMPS supports low speed modem transmission at rates generally limited to 6.8 kbps. Although once widely deployed in the United States, Australia, the Philippines, and other countries, AMPS has almost entirely been replaced by digital technology. Australian regulators mandated a cutover from analogue (Aussie for analog.) AMPS to digital GSM and CDMA, beginning December 31, 1999, in Melbourne, and gradually extending throughout the country during 2000. Motorola subsequently developed Narrowband AMPS (N-AMPS), which improved system capacity. In the United States, the Federal Communications Commission (FCC) authorized carriers to cease support for analog systems as of March 1, 2008. Digital AMPS (D-AMPS), standardized as IS-54 and IS-136, is essentially a digital version of AMPS. See also 1G, A Carrier, analog, B Carrier, carrier, CDMA, cellular radio, D-AMPS, digital, downlink, FCC, FDD, FDMA, FM, GSM, handoff, modem, N-AMPS, non-wireline carrier, uplink, and wireline carrier. |
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