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					Computer Networks
 Chapter 2: Physical Layer



       Farzad Rojan
          Computer Networks – Chapter 2




Introduction
Transmission Media
Wireless Transmission
Communication Satellites
Public Switched Telephone Network
Mobile Network
Computer Networks – Chapter 2

       Introduction
       Fourier Analysis
Computer Networks – Chapter 2

       Introduction
Bandwidth-Limited Signals
                       Computer Networks – Chapter 2

                         Transmission Media



   Magnetic Media
       How cheap? How fast?
   Twisted pair cable
       CAT-3, CAT-5, CAT-5e, CAT-6
       UTP and STP



           (a) Category 3 UTP                (b) Category 5 UTP.
                    Computer Networks – Chapter 2

                      Transmission Media



   Coaxial Cable
       Wideband and long distance
       Multi-band transmission
       Two way transmission by split band
                     Computer Networks – Chapter 2

                       Transmission Media



   Fiber optics
       Ultra Wideband and long distance
       Multi-band transmission by wave-length division
        multiplexing
       Up to Terra bps
       No electromagnetic interfrence.
                  Computer Networks – Chapter 2

                    Transmission Media



   Transmission of light in fiber optics
                      Computer Networks – Chapter 2

                        Transmission Media



   Fiber cables
       Multi mode
       Single mode
                    Computer Networks – Chapter 2

                      Transmission Media



   Light Sources
       LED
       Semiconductor Laser
                     Computer Networks – Chapter 2

                       Transmission Media



   Comparison of fiber and copper
       Distace 5 km vs. 50 km
       Crosstalk
       Weight 8000 kg vs. 100 kg per km
       Capacity low vs. ultra high
       Electrical interface cheap vs. expensive
                    Computer Networks – Chapter 2

                    Wireless Transmission



   Wireless communication
       Electromagnetic spectrum
                    Computer Networks – Chapter 2

                     Wireless Transmission



   Wireless communication
       Radio transmission
                        Computer Networks – Chapter 2

                        Wireless Transmission



   Wireless communication bands
       Industrial, scientific and medical bands (ISM)
           Unlicenced bands (low power)
                 Computer Networks – Chapter 2

                Communication Satellites



   Communication satellites
                  Computer Networks – Chapter 2

                 Communication Satellites



   Satellites bands




   Transponders: low noise receivers high power
    transmitters about 80 MHz bandwidth
                   Computer Networks – Chapter 2

                   Communication Satellites



   VSAT
       1m diameter antenna
       19.2 kbps
                      Computer Networks – Chapter 2

                     Communication Satellites



   Iridium (LEO)
       66 satellites (element 77 is iridium)
       Moving cells
                     Computer Networks – Chapter 2

                    Communication Satellites



   Globalstar
       48 satellites at 750 km
       Ground station switching
                    Computer Networks – Chapter 2

                    Communication Satellites



   Teledesic
       30 satellites at 1350 km
       100 Mbps up- and 720 Mbps downlink internet
       Planned for year 2005
                     Computer Networks – Chapter 2

                Public Switched Telephone Network



   Public switched telephone network
       Spread out of the world
       Modems are used for data transfer
       The cheapest for access network
   Structure of telephone network
                       Computer Networks – Chapter 2

                 Public Switched Telephone Network


   New circuit routing in telephone network




   Local loops
       Wired or wireless
       Digital or analog
                     Computer Networks – Chapter 2

                Public Switched Telephone Network

   Local loops
       Wired or wireless
       Digital or analog
                    Computer Networks – Chapter 2

               Public Switched Telephone Network

   Digital subscriber lines (XDSL)
       HDSL, VDSL and ADSL
                    Computer Networks – Chapter 2

               Public Switched Telephone Network

   Asymmetric Digital subscriber lines (ADSL)
       Discrete Multi Tone (DMT)
       ANSI T1.413 Allow (8/1 Mbps)
       Standard service (512/64 kbps)
       Premium service (1000/256 kbps)
                Computer Networks – Chapter 2

           Public Switched Telephone Network



   ADSL equipments
               Computer Networks – Chapter 2

          Public Switched Telephone Network



   FDM
               Computer Networks – Chapter 2

          Public Switched Telephone Network



   WDM
                     Computer Networks – Chapter 2

                Public Switched Telephone Network



   TDM
       Digital trunk T1 and Multiplexing
                     Computer Networks – Chapter 2

                Public Switched Telephone Network



   TDM
       Digital trunk T1 and Multiplexing
                         Computer Networks – Chapter 2

                    Public Switched Telephone Network



   TDM
       CCITT Digital trunk E1 and Hierarchy
           E1:   32×64 kbps=2.048 Mbps
           E2:   4E1       =8.848 Mbps
           E3:   4E2       =34.304 Mbps
           E4:   4E3       =139. 264 Mbps
           E5:   4E4       =565.148 Mbps
                        Computer Networks – Chapter 2

                  Public Switched Telephone Network



   SONET/SDH
       Synchronous optical network
           Different carriers internetwork
           Support international internetworking
           Multiplexing more channels
           Operation, administration and maintenance (OAM)
                     Computer Networks – Chapter 2

                Public Switched Telephone Network


   SONET frame
       Basic frame are repeated every 125 µsec
       Basic frame contains 810 bytes
                 Computer Networks – Chapter 2

            Public Switched Telephone Network


   SONET and SDH trunk hierarchy
                        Computer Networks – Chapter 2

                Public Switched Telephone Network

Switching
   Circuit switching
   Message switching
   Packet switching
     Computer Networks – Chapter 2

Public Switched Telephone Network
                 Computer Networks – Chapter 2

                      Mobile Network



   1st generation: analog voice
   2nd generation: digital voice, SMS and data
   3rd generation: digital voice and data

				
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posted:2/9/2013
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