cn ch21 The Physical Layer Chapter 2

cn ch22 The Theoretical Basis for Data Communication Fourier Analysis Bandwidth-Limited Signals Maximum Data Rate of a Channel

cn ch23 Bandwidth-Limited Signals A binary signal and its root-mean-square Fourier amplitudes. (b) – (c) Successive approximations to the original signal.

cn ch24 Bandwidth-Limited Signals (2) (d) – (e) Successive approximations to the original signal.

cn ch25 Bandwidth-Limited Signals (3) Relation between data rate and harmonics.

cn ch26 Guided Transmission Data Magnetic Media Twisted Pair Coaxial Cable Fiber Optics

cn ch27 Twisted Pair (a) Category 3 UTP. (b) Category 5 UTP.

cn ch28 Coaxial Cable A coaxial cable.

cn ch29 Fiber Optics (a) Three examples of a light ray from inside a silica fiber impinging on the air/silica boundary at different angles. (b) Light trapped by total internal reflection.

cn ch210 Transmission of Light through Fiber Attenuation of light through fiber in the infrared region.

cn ch211 Fiber Cables (a) Side view of a single fiber. (b) End view of a sheath with three fibers.

cn ch212 Fiber Cables (2) A comparison of semiconductor diodes and LEDs as light sources.

cn ch213 Fiber Optic Networks A fiber optic ring with active repeaters.

cn ch214 Fiber Optic Networks (2) A passive star connection in a fiber optics network.

cn ch215 Wireless Transmission The Electromagnetic Spectrum Radio Transmission Microwave Transmission Infrared and Millimeter Waves Lightwave Transmission

cn ch216 The Electromagnetic Spectrum The electromagnetic spectrum and its uses for communication.

cn ch217 Radio Transmission (a) In the VLF, LF, and MF bands, radio waves follow the curvature of the earth. (b) In the HF band, they bounce off the ionosphere.

cn ch218 Politics of the Electromagnetic Spectrum The ISM bands in the United States.

cn ch219 Lightwave Transmission Convection currents can interfere with laser communication systems. A bidirectional system with two lasers is pictured here.

cn ch220 Communication Satellites Geostationary Satellites Medium-Earth Orbit Satellites Low-Earth Orbit Satellites Satellites versus Fiber

cn ch221 Communication Satellites Communication satellites and some of their properties, including altitude above the earth, round-trip delay time and number of satellites needed for global coverage.

cn ch222 Communication Satellites (2) The principal satellite bands.

cn ch223 Communication Satellites (3) VSATs using a hub.

cn ch224 Low-Earth Orbit Satellites Iridium (a) The Iridium satellites from six necklaces around the earth. (b) 1628 moving cells cover the earth.

cn ch225 Globalstar (a) Relaying in space. (b) Relaying on the ground.

cn ch226 Public Switched Telephone System Structure of the Telephone System The Politics of Telephones The Local Loop: Modems, ADSL and Wireless Trunks and Multiplexing Switching

cn ch227 Structure of the Telephone System (a) Fully-interconnected network. (b) Centralized switch. (c) Two-level hierarchy.

cn ch228 Structure of the Telephone System (2) A typical circuit route for a medium-distance call.

cn ch229 Major Components of the Telephone System Local loops  Analog twisted pairs going to houses and businesses Trunks  Digital fiber optics connecting the switching offices Switching offices  Where calls are moved from one trunk to another

cn ch230 The Politics of Telephones The relationship of LATAs, LECs, and IXCs. All the circles are LEC switching offices. Each hexagon belongs to the IXC whose number is on it.

cn ch231 The Local Loop: Modems, ADSL, and Wireless The use of both analog and digital transmissions for a computer to computer call. Conversion is done by the modems and codecs.

cn ch232 Modems (a) A binary signal (b) Amplitude modulation (c) Frequency modulation (d) Phase modulation

cn ch233 Modems (2) (a) QPSK. (b) QAM-16. (c) QAM-64.

cn ch234 Modems (3) (a) V.32 for 9600 bps. (b) V32 bis for 14,400 bps. (a) (b)

cn ch235 Digital Subscriber Lines Bandwidth versus distanced over category 3 UTP for DSL.

cn ch236 Digital Subscriber Lines (2) Operation of ADSL using discrete multitone modulation.

cn ch237 Digital Subscriber Lines (3) A typical ADSL equipment configuration.

cn ch238 Wireless Local Loops Architecture of an LMDS system.

cn ch239 Frequency Division Multiplexing (a) The original bandwidths. (b) The bandwidths raised in frequency. (b) The multiplexed channel.

cn ch240 Wavelength Division Multiplexing Wavelength division multiplexing.

cn ch241 Time Division Multiplexing The T1 carrier (1.544 Mbps).

cn ch242 Time Division Multiplexing (2) Delta modulation.

cn ch243 Time Division Multiplexing (3) Multiplexing T1 streams into higher carriers.

cn ch244 Time Division Multiplexing (4) Two back-to-back SONET frames.

cn ch245 Time Division Multiplexing (5) SONET and SDH multiplex rates.

cn ch246 Circuit Switching (a) Circuit switching. (b) Packet switching.

cn ch247 Message Switching (a) Circuit switching (b) Message switching (c) Packet switching

cn ch248 Packet Switching A comparison of circuit switched and packet-switched networks.

cn ch249 The Mobile Telephone System First-Generation Mobile Phones: Analog Voice Second-Generation Mobile Phones: Digital Voice Third-Generation Mobile Phones: Digital Voice and Data

cn ch250 Advanced Mobile Phone System (a) Frequencies are not reused in adjacent cells. (b) To add more users, smaller cells can be used.

cn ch251 Channel Categories The 832 channels are divided into four categories: Control (base to mobile) to manage the system Paging (base to mobile) to alert users to calls for them Access (bidirectional) for call setup and channel assignment Data (bidirectional) for voice, fax, or data

cn ch252 D-AMPS Digital Advanced Mobile Phone System (a) A D-AMPS channel with three users. (b) A D-AMPS channel with six users.

cn ch253 GSM Global System for Mobile Communications GSM uses 124 frequency channels, each of which uses an eight-slot TDM system

cn ch254 GSM (2) A portion of the GSM framing structure.

cn ch255 CDMA: Code Division Multiple Access Allow each station to transmit over entire frequency spectrum all the time. Multiple simultaneous transmissions are separated using coding theory. Colliding frames may not be totally garbled. There are techniques to separate signals sent by different senders. Similar to a party where different conversations use different language. Extract desired signal and reject others as random noises. Each bit time is subdivided into m short intervals called chips, typically chips per bit. Each station is assigned a unique m-bit code or chip sequence. To send a bit 1, a station sends its chip sequence. To send a bit 0, a station sends the complement of its chip sequence. For m=8, A is assigned A sends as bit 1, and as bit 0.

cn ch256 Simple Analysis of CDMA Assume 1 MHz band for 100 stations Use FDM, one station has 10kHz and 10 kbps (assume 1 bit per Hz) Use CDMA, one station has 1MHz, and 1Mchips per seconds. If CDMA uses less than 100 chips per bit then CDMA will be more efficient.

cn ch257 CDMA Coding Theory Let’s use bipolar notation +1 for binary 1 (chip signal), -1 for binary 0. A bit1, A send or ( ). Let S be the m-chip vector for station s and for its negation. Two chip sequence S and T are orthogonal if ST=0. if ST=0 then S =0 All chip sequences must be pariwise orthogonal. S =-1 CDMA Example Let S=A+ +C, SC=(A+ +C)C=AC+ C+CC=0+0+1=1

cn ch258 CDMA – Code Division Multiple Access (a) Binary chip sequences for four stations (b) Bipolar chip sequences (c) Six examples of transmissions (d) Recovery of station C’s signal

cn ch259 Walsh-Hadamard Matrix for Orthogonal Spreading Sequence a)The Walsh-Hadamard Matrix provides the Orthogonal Chip Sequences of length n=2m. Replacing 0 with signal -1 and 1 with signal +1. b)It can be recursively constructed. W 1 =[0]. W 2n = where contains complement elements of W n.

cn ch260 CDMA Sending Channel 1: 110 -> > (-1,-1,-1,-1),(-1,-1,-1,-1),(+1,+1,+1,+1) Channel 2: 010 -> > (+1,-1,+1,-1),(-1,+1,-1,+1),(+1,-1,+1,-1) Channel 3: 001 -> > (+1,+1,-1,-1),(+1,+1,-1,-1),(-1,-1,+1,+1) Sum Signal: (+1,-1,-1,-3),(-1,+1,-3,-1),(+1,-1,+3,+1) Chip Sequence c1: (-1,-1,-1,-1) c2: (-1,+1,-1,+1) c3: (-1,-1,+1,+1) c4: (-1,+1,+1,-1)

cn ch261 CDMA Receiving/Decoding Sum Signal: (+1,-1,-1,-3),(-1,+1,-3,-1),(+1,-1,+3,+1) Channel 2 Sequence: (-1,+1,-1,+1),(-1,+1,-1,+1),(-1,+1,-1,+1) Correlator Output: (-1,-1,+1,-3),(+1,+1,+3,-1),(-1,-1,-3,+1) Integrated Output: -4, +4, -4 Binary Output: 0, 1, 0

cn ch262 Power Control/Assignment For the CDMA to work, the power levels of signals from all stations should be the same (or within certain tolerance level) when received by the receiver. A good heuristic: Each mobile station sends signal with the power level inverse of that received from the base station. The base station can tell mobile station to increase/decrease its power.

cn ch263 Third-Generation Mobile Phones: Digital Voice and Data Basic services an IMT-2000 network should provide High-quality voice transmission Messaging (replace , fax, SMS, chat, etc.) Multimedia (music, videos, films, TV, etc.) Internet access (web surfing, w/multimedia.)

cn ch264 Cable Television Community Antenna Television Internet over Cable Spectrum Allocation Cable Modems ADSL versus Cable

cn ch265 Community Antenna Television An early cable television system.

cn ch266 Internet over Cable Cable television

cn ch267 Internet over Cable (2) The fixed telephone system.

cn ch268 Spectrum Allocation Frequency allocation in a typical cable TV system used for Internet access

cn ch269 Cable Modems Typical details of the upstream and downstream channels in North America.