EE 179: Introduction to Communications

Professor Andrea Goldsmith

Outline

Course Information and Policies

Communication Systems Today

Future Systems

Design Challenges

Course Information(see web or handout for more details)

Instructor: Andrea Goldsmith, Packard 371, andrea@ee, Ext: 56932, OHs: M 1-2pm, W 12-1pm, Th 5:30-6:30.

Class Homepage: www.stanford.edu/class/ee179 (temporary page at www.stanford.edu/class/ee104/index179.html)

TAs: Neil Achtman,neil18@stanford.edu, OHs and Email OHs: TBD Ragiv Agrawal, ragivag@wsl, OHs and Email OHs: TBD

Class mailing list: ee179-students (automatic for registered students), ee179-staff for instructor/TAs, guest list available

Discussion Section: T 6-7pm (tentative) Book: An Introduction to Analog and Digital

Communications

Grading: HWs 30%, Midterm 30%, Final 40% Prerequisites: EE102a or equivalent

Class Policies Exam policy:

Exams must be taken at their scheduled times.

Exceptions only in very rare circumstances.Midterm: 2/13 from 11-12:30pmFinal: 3/18 from 8:30-11:30am.

HW policy: Assigned Wednesday, due following

Thursday. Lose 25% credit per day late. Up to 3 students can collaborate on 1

writeup. All collaborators must work out all problems.

Communication Systems

Provide for electronic exchange of multimedia dataVoice, data, video, music, email, web pages, etc.

Communication Systems TodayRadio and TV broadcasting (covered later in the

course)Public Switched Telephone Network (voice,fax,modem)Cellular Phones Computer networks (LANs, WANs, and the Internet)Satellite systems (pagers, voice/data, movie

broadcasts)Bluetooth

PSTN Design

Local exchange Handles local callsRoutes long distance calls over high-speed lines

Circuit switched network tailored for voice Faxes and modems modulate data for voice

channel DSL uses advanced modulation to get 1.5 Mbps

Local SwitchingOffice (Exchange)

Local SwitchingOffice (Exchange)

Long Distance Lines(Fiber)Local Line

(Twisted Pair)

FaxModem

Cellular System Basics

Geographic region divided into cells Frequencies/timeslots/codes reused at spatially-separated locations (analog systems use FD, digital

use TD or CD) Co-channel interference between same color cells. Handoff and control coordinated through cell base stations

BASESTATION

Cell Phone Backbone Network

BSBS

MTSO PSTN MTSO

BS

San Francisco

New York

Internet

Local Area Networks (LANs)

LANs connect “local” computers Breaks data into packets Packet switching (no dedicated channels) Proprietary protocols (access,routing, etc.)

01011011

1011

0101 0101

101101011011

Wireless Local Area Networks (WLANs)

WLANs connect “local” computers (100m range)

Breaks data into packets Channel access is shared (random

access) Backbone Internet provides best-

effort service

01011011

InternetAccessPoint

0101 1011

Wide Area Networks:The Internet

Many LANs and MANs bridged together

Universal protocol: TCP/IP (packet based).

Guaranteed rates or delays cannot be provided.

Hard to support user mobility. Highly scalable and flexible topology

01011011 Internet

1011

0101

Bridge MANLAN

Satellite andFiber Lines

Bridge LAN

Satellite Systems

Cover very large areas Different orbit heights

GEOs (39000 Km) versus LEOs (2000 Km)

Optimized for one-way transmissionRadio (XM, DAB) and movie (SatTV) broadcasting

Most two-way systems struggling or bankruptExpensive alternative to terrestrial systemA few ambitious systems on the horizon

Paging SystemsBroad coverage for short messagingMessage broadcast from all base

stationsSimple terminalsOptimized for 1-way transmissionAnswer-back hardOvertaken by cellular

Bluetooth

Cable replacement for electronic devicesCell phones, laptops, PDAs, etc.

Short range connection (10-100 m)1 data (721 Kbps) and 3 voice (56 Kbps)

channelsRudimentary networking capabilities

Future Systems

Nth Generation CellularNth Generation WLANsNth Generation InternetWireless EntertainmentSensor Networks Smart Homes/AppliancesAutomated Cars/FactoriesTelemedicine/LearningAll this and more…

Ubiquitous Communication Among People and Devices

Ad-Hoc Networks

Peer-to-peer communications. No backbone infrastructure. Routing can be multihop. Network topology is dynamic.

Sensor NetworksEnergy is the driving

constraint

Nodes powered by nonrechargeable batteriesData flows to centralized location.Low per-node rates but up to 100,000 nodes.Data highly correlated in time and space.Nodes can cooperate in transmission,

reception, compression, and signal processing.

Distributed Control over Wireless Links

Packet loss and/or delays impacts controller performance. Controller design should be robust to network faults. Joint application and communication network design.

Automated Vehicles - Cars - UAVs - Insect flyers

Design Challenges Hardware Design

Precise componentsSmall, lightweight, low powerCheapHigh frequency operation

System DesignConverting and transferring informationHigh data rates Robust to noise and interferenceSupports many users

Network DesignConnectivity and high speedEnergy and delay constraints

Main Points Communication systems send information

electronically over communication channels

Many different types of systems which convey many different types of information

Design challenges include hardware, system, and network issues

Communication systems recreate transmitted information at receiver with high fidelity

Focus of this class is design and performance of analog and digital communication systems