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Lecture 7: Channel capacity and multiplexing

Lecture 7: Channel capacity and multiplexing. Anders Västberg vastberg@kth.se 08-790 44 55. Concepts. Data rate Channel capacity Signal Bandwidth Channel Bandwidth Noise Error rate. Bandwidth limited channel Hartley’s law. C Channel capacity (bit/s) M Discrete Levels

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Lecture 7: Channel capacity and multiplexing

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  1. Lecture 7: Channel capacity and multiplexing Anders Västberg vastberg@kth.se 08-790 44 55

  2. Concepts • Data rate • Channel capacity • Signal Bandwidth • Channel Bandwidth • Noise • Error rate

  3. Bandwidth limited channelHartley’s law C Channel capacity (bit/s) M Discrete Levels B Channel bandwidth (Hz)

  4. Bandwidth limited and noisy channelShannon’s law C Channel capacity (bit/s) SNR=P/N Signal to Noise ratio (not in dB!) B Channel bandwidth (Hz)

  5. Shannon’s Law

  6. Bandwidth and Capacity

  7. Multiplexing • The signals of the different users are multiplexed at the transmitter and then transmitted as one entity. • Examples of broadcast network: • Radio and TV broadcast systems • Downlinks in a mobile cellular communication system • Downlinks in a satellite communication system

  8. Multiple Access • Examples of Multiple Access systems: • Uplink in a mobile cellular system • Uplink in a satellite communication system

  9. Multiplexing/Multiple Access • Frequency division multiplexing (multiple access) (FDM/FDMA) • Channel bandwidth greater than signal bandwidth • Time division multiplexing (multiple access) (TDM/TDMA) • Channel capacity greater than signal data rate

  10. FDM/TDM

  11. Frequency divison multiplexing |H(f)| f Signal bandwidth Guard band

  12. Time divison multiplexing • Bit interleaving • Block interleaving • Synchronous TDM • Time slots fixed and pre-assigned to sources • Asynchronous TDM • Time given to sources with data to send 1 0 1 1 0 0 1 1 1 1 1 1 0 0 1 1 0 1

  13. Homework before F8 • Beskriv principen för DSSS? • Vad är snabb och långsam FHSS?

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