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 channel Hartley’s law CChannel capacity (bit/s) MDiscrete Levels BChannel bandwidth (Hz)

4. Bandwidth limited and noisy channel Shannon’s law CChannel capacity (bit/s) SNR=P/NSignal to Noise ratio (not in dB!) BChannel 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 Guard band Signal bandwidth |H(f)| f

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 10110011 10110011 1 1

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