| 单词 | PACS (Personal Access Communications Services) |
| 释义 | PACS (Personal Access Communications Services) A digital cordless telephony total system stan- dard that addresses both the air interface and network infrastructure. A modification of the WACS (Wireless Access Communication System) specification, PACS was developed in the U.S. for licensed Personal Communications Services (PCS) applications, although several unlicensed versions exist as well. The licensed version of PACS employs frequency division duplex (FDD) to support downstream transmission in the 1930–1990 MHz band and upstream transmission in the 1850–1910 band, with channel spacing at 300 kHz. Each channel will support a data rate of 384 kbps with µ/4 quaternary phase shift keying (µ/4 QPSK) as the modulation technique. Each RF channel supports seven users through time division multiple access (TDMA).Voice encoding is adaptive differential pulse code modulation (ADPCM) at 32 kbps. See also ADPCM, air interface, channel, cordless telephone, digital, downstream, encode, FDD, modulation, PCS, µ/4 QPSK, TDMA, and upstream. |
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