07-PL - PhysicalLayer: DataEncoding&Transmission 1...

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1 Physical Layer: Data Encoding & Transmission
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2 Network Interface Card (NIC) LL in part,  PL in total are implemented in NIC Ethernet card, 802.11 card, … NIC is semi-autonomous Listens to the link independent of the CPU Talks to CPU after reception of a new frame CPU talks to the card to send a frame Has connectivity to both the I/O bus and the network link CPU cache Memory I/O Bus Link Bus interface Link interface NIC I/O Bus Interface PCI Link Interface Link Interface
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3 Steps in Transmission of a Datagram to a Neighbor Datagram Datagram H Datagram H EDC Bit error prone link Datagram Datagram H D’ EDC‘ LL All bits in D’ OK? N Detected error Y Encode Bits  to the Link  LL Decode Bits  from the Link  PL PL
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4 Encoding - Definitions Data : Something which carries meaning Can be  analog , e.g., radio, TV signals or  digital  such as data files etc. For this course, we are ONLY interested in  digital  data encoding Signal : Encoded data, i.e., what is  transferred on the link (wired or wireless) Analog : Represents data with continuously  varying electromagnetic waves Digital : Represents data with a sequence of  voltage pulses LL Frame Datagram Datagram H Datagram H EDC Add Framing  Information Encode Bits  to the Link  PL LL Link
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5 Encoding Digital Data Digital Data  (0s and 1s) can be encoded as an  Analog Signal Signal on the link is an electromagnetic wave of some frequency Signal can also be photonic pulses of a given wavelength over optical  fiber 3 general methods Amplitude Shift Keying Frequency Shift Keying Phase Shift Keying
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6 Digital Data to Analog Signal:ASK Digital Data = m(t) Modem Analog Signal = s(t)  s(t) = A cos(2*PI*fc*t) – binary 1 s(t) = 0                          – binary 0
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7 Digital Data to Analog Signal:FSK Digital Data = m(t) Modem Analog Signal = s(t)  s(t) = A cos(2*PI*f1*t) – binary 1 s(t) = A cos(2*PI*f2*t) – binary 0
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8 FDM + FSK on Voice Grade Line Full-duplex
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07-PL - PhysicalLayer: DataEncoding&Transmission 1...

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