| 单词 | PDU (Protocol Data Unit) |
| 释义 | PDU (Protocol Data Unit) permits.The basic user channel rate is 9.6 kbps, although various channel rates can be achieved, depending on the carrier implementation. As compared to AMPS, CDMA offers the advantages of improved bandwidth utilization (as much as 10:1 or even 20:1) and time division multiple access (TDMA) (as much as 6:1), soft handoff, variable-rate speech coding, and support for both voice and data.The IS-95-B specification supports symmetric data rates of 4.8 kbps and 14.4 kbps per channel; as many as eight channels can be aggregated to support a data rate up to 115.2 kbps. CDMA offers additional advantages in terms of maximum cell size due to improved antenna sensitivity, and battery time due to precise power control mechanisms.The first commercial systems were installed in South Korea and Hong Kong in 1995, and in the United States in 1996. See also 2G, AMPS, analog, band, bandwidth, BPSK, carrier, CDMA, cellular radio, CELP, channel, digital, downlink, encode, EIA, EVRC, FDD, frequency, handoff, modulation, OQPSK, signal, symmetric, TDMA, TIA, and uplink. |
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