Professor Andrea Goldsmith 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: HW policy: Exams must be taken at their scheduled times. Exceptions only in very rare circumstances. Midterm: 2/13 from 11-12:30pm Final: 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 data Voice, data, video, music, email, web pages, etc. Communication Systems Today Radio 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 Circuit switched network tailored for voice Local Switching Office (Exchange) Local Switching Office (Exchange) Long Distance Lines (Fiber) Fax Modem Local Line (Twisted Pair) Local exchange Handles local calls Routes 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

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 BASE STATION

Cell Phone Backbone Network San Francisco BS BS New York MTSO MTSO PSTN BS Internet

Local Area Networks (LANs) 01011011 1011 0101 0101 1011 01011011 LANs connect “local” computers Breaks data into packets Packet switching (no dedicated channels) Proprietary protocols (access,routing, etc.)

Wireless Local Area Networks (WLANs) 1011 01011011 0101 Internet Access Point WLANs connect “local” computers (100m range) Breaks data into packets Channel access is shared (random access) Backbone Internet provides best-effort service

Wide Area Networks: The Internet 01011011 1011 LAN Bridge MAN Bridge LAN 0101 Satellite and Fiber Lines 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 Local: 100m range For efficiency and fairness, data is packetized. Packet routing: packets may take different routes, may entail delays on some routes, lost packets, packets arriving out of order (bad for video). Mobility hard to support due to underlying routing and addressing protocols Optimized for stationary data users, in contrast to cellular networks optimized for mobile voice users. - How will these networks support multiple applications (voice, data, video, and whatever else comes down the pike?)

Satellite Systems Cover very large areas Different orbit heights GEOs (39000 Km) versus LEOs (2000 Km) Optimized for one-way transmission Radio (XM, DAB) and movie (SatTV) broadcasting Most two-way systems struggling or bankrupt Expensive alternative to terrestrial system A few ambitious systems on the horizon

Paging Systems Broad coverage for short messaging Message broadcast from all base stations Simple terminals Optimized for 1-way transmission Answer-back hard Overtaken by cellular

Bluetooth Cable replacement for electronic devices Cell phones, laptops, PDAs, etc. Short range connection (10-100 m) 1 data (721 Kbps) and 3 voice (56 Kbps) channels Rudimentary networking capabilities

Future Systems Ubiquitous Communication Among People and Devices Nth Generation Cellular Nth Generation WLANs Nth Generation Internet Wireless Entertainment Sensor Networks Smart Homes/Appliances Automated Cars/Factories Telemedicine/Learning All this and more…

Ad-Hoc Networks Peer-to-peer communications. No backbone infrastructure. Routing can be multihop. Network topology is dynamic. -No backbone: nodes must self-configure into a network. -In principle all nodes can communicate with all other nodes, but multihop routing can reduce the interference associated with direct transmission. -Topology dynamic since nodes move around and link characteristics change. -Applications: appliances and entertainment units in the home, community networks that bypass the Internet. Military networks for robust flexible easily-deployed network (every soldier is a node).

Sensor Networks Energy is the driving constraint Nodes powered by nonrechargeable batteries Data 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 Automated Vehicles - Cars - UAVs - Insect flyers Packet loss and/or delays impacts controller performance. Controller design should be robust to network faults. Joint application and communication network design.

Design Challenges Hardware Design System Design Network Design Precise components Small, lightweight, low power Cheap High frequency operation System Design Converting and transferring information High data rates Robust to noise and interference Supports many users Network Design Connectivity and high speed Energy 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