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L9 - Higher-generation mobile communication 2.5G 3G 4G Goal...

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Higher-generation mobile communication 2.5G, 3G, 4G ..... Goal - higher data rates, support multimedia. However, evolution to higher rates is not necessarily coming in discrete steps. Ref: IEEE Commun. Mag., April 2005, pp. 48- 56, other articles. Revision -peak data rates increased - 153 kb/s to 1.8 Mb/s. Ref. IEEE Commun. Mag., Feb. 2005, pp. 65- 125 on beyond 3G. Orthogonal frequency division multiplexing - something like the multiple channels of DSL. Ultra Wideband transmission
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More up-to-date information in IEEE Communications magazine: May 2010 issue - broadband wireless services, starting on Page 86. August 2010 issue - 4G technology starting 0n Page 38. Complex schemes: -splitting stream of traffic into multiple channels - using feedback to select suitable channels - avoid interference - using error correction and retransmission schemes. A video channel requires the capacity of about 60 voice channels - much more demanding.
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Some data can be broadcast to many receivers (multicast). One to one transmission is called unicast. Unicast and multicast signals may share communication facilities.
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DSL versus Cable TV DSL - A dedicated private channel – about 256 kb/s upstream, 1+ mb/s downstream. Cable TV - can provide much higher capacity in both directions. - Must be shared - Not private. - Capacity varies with usage of others - Needs an access method as in mobile networks
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Summary of the physical layer – Chapter 2 A) fundamental limitations – distortion, bandwidth, noise, channel capacity. B) Media - Guided – twisted pair, coaxial cable, optical fiber. Attenuation – dB/km, capabilities.
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