| Wireless Data
Transmission |
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| n | Existing
1st- and 2nd-generation cellular systems |
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| provide
good coverage, but at modest data rates |
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| only |
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| n | Current
research focus: 3rd-generation cellular |
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| systems
(IMT-2000, UMTS) |
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| – | provide
ubiquitous coverage (including satellite) |
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| – | international
standardization |
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| – | ambitious
data rates: 144 kbps for user in vehicle, 384 |
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| kpbs
for walking user, 2 Mbps for stationary users |
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| – | overlay
of different-sized cells, complicated spectrum |
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| management |
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