Lecture 1: Wireless communications systems Aliazam Abbasfar

Outline Course Information and policies Course Syllabus Communication Systems Design Challenges

Course Information Instructor : Aliazam Abbasfar Office Hours : Sa-Tu Classes? Grading: HWs 10%, Midterm 60%, Project 30% Prerequisites: Digital Communications

Class policies Exam dates are fixed (No make-up exams) Midterm: TBD Final: 88/11/7 Academic honesty HW should be your own work Turn off your cell phones during lectures

Course Syllabus Overview of Wireless Communications (1) Wireless propagation (4) Diversity (6) Narrowband/Wideband Modulation (6) Spread Spectrum Techniques (4) Multiple access techniques (2) Cellular concept/standards (3) Multiple Input/output Systems (MIMO) (4) Wireless Networks and Resource Management (1)

References David Tse and Pramod Viswanath, Fundamentals of Wireless Communications, Cambridge University Press, 2005Fundamentals of Wireless Communications Andrea Goldsmith, Wireless Communications, Cambridge University PressWireless Communications Theodore S. Rappaport, Wireless communications, principles & practice, Prentice Hall, 1996 A.R.S. Bahai, B.R. Saltzberg, M. Ergen, “Multi- Carrier Digital Communications, Theory and Applications of OFDM,” 2nd Ed., Springer 2004 R. Peterson, R. Ziemer, D. Borth, Introduction to Spread Spectrum Communications, Prentice Hall, 1995.

Communication started in wireless form smoke/torch/flash signaling Modern communication goes back to Telegraph (Morse 1837) wireline communications digital replaced old technologies Telephone (Bell 1876) introduced telephony Analog communication wireline Radio transmission was born decades later (Marconi 1895) Radio technology has been growing rapidly ever since longer distances with better quality less power, and smaller, cheaper equipments Communication systems overview

Reliable (electronic) exchange of information Voice, data, video, music, , web pages, etc Communication Systems Today Radio and TV broadcasting Public Switched Telephone Network (voice, fax, modem) Computer networks (LANs, WANs, and the Internet) Cellular Phones Satellite systems (TV broadcast, voice/data, pagers) Bluetooth/wireless devices Sensor networks Communication Systems

AM radio broadcast started in 1920 E. Armstrong invented super heterodyne AM receiver FM was invented in 1933 TV broadcast Commercial TV began in London (BBC 1936) FCC authorized TV bands in 1941 Satellite broadcast services Rapid migration to digital broadcast Radio and TV broadcasting

Satellite types: Geosynchronous (GEO)40,000Km Medium-earth orbit (MEO) 9000 Km Low-earth orbit (LEO)2000 Km GEOs first suggested in a sci-fi book (A.C. Clark 1945) First deployed satellites No Geo Soviet Union’s Sputnik in 1957 NASA/Bell Laboratories’ Echo-1 in 1960 Telestar I was launched in 1962 Relay TV signals between US and Europe First commercial Sat (Early Bird – 1965) GEOs Wide coverage Good for downlink broadcast no good in uplink (high power) large delay (bad for voice service) Satellite systems

LEOs Lower power Smaller delay Need many satellites Shift towards LEOs in 1990 Global domination Compete with cellular systems Failed miserably (Iridium ) Big, power hungry mobile terminals Natural area for satellite systems is broadcasting Now operate in 12GHz band 100s of TV and radio channels All over the world Global Positioning System (GPS) Satellite signals used to pinpoint location Popular in cars, cell phones, and navigation devices Satellite systems

LAN/Ethernet technology in 1970 wireline was popular again 10 Mbps data rate far exceeded anything available using radio Wireless LAN was enabled by ISM band (FCC 85) No license – free band But, must have low power profile resulted in high costs ($1400 vs $200 Ethernet) Wired Ethernets today offer data rates over 1 Gbps Performance gap between wired and wireless LANs is likely to increase over time Additional spectrum allocation might help WLANs are preferred due to their convenience freedom from wires Communication networks

Provides high-speed data within a small region 1G : 26 MHz spectrum MHz ISM band Data rate : 1-2 Mbps No standard Not very successful 2G : 80 MHz spectrum GHz ISM band Data rate : 1.6 Mbps (raw data rates of 11 Mbps) IEEE b standard Direct sequence spread spectrum range : 150m IEEE a wireless LAN standard operates with 300 MHz of spectrum in the 5 GHz U-NII band. Data rate : Mbps multicarrier modulation European counterpart : HIPERLAN Type 1, is similar to the IEEE a wireless LAN standard Wireless LAN overview

802.11n is the latest WLAN standard Close to finalization Operates in 2.4 and 5.0 GHz ISM bands Adaptive OFDM technology MIMO technology (2-4 antenna) Data rates up to 600 Mbps Range 60 m Wimax (802.16) : Wide area wireless network standard System architecture similar to cellular Hopes to compete with cellular OFDM/MIMO is core link technology Operates in 2.5 and 3.5 MHz bands Different for different countries, 5.8 also used. Bandwidth is MHz Fixed (802.16d) : 75 Mbps max, up to 50 mile cell radius Mobile (802.16e) : 15 Mbps max, up to 1-2 mile cell radius Latest standards

The most successful application of wireless networking It began in 1915, wireless voice transmission between New York and San Francisco 1946 public mobile telephone service in 25 cities across US Initial systems used a central transmitter to cover an entire metropolitan area limited capacity the maximum # of users was only 534 (30 years after first link) Solution came in 50's and 60's (Bell Labs) Cellular concept Frequency reuse First cellular system deployed in Chicago in 1983 Analog system Very popular - already saturated by 1984 Cellular systems

2 nd Generation (2G) Digital communications Higher capacity More services (voice, data, paging) So many competitors Only 3 standards in US! GSM is most popular Multi-mode devices 3G Based on CDMA technology WCDMA and CDMA2000 4G ? Cellular systems

Cable replacement RF technology (low cost) Short range (10m, extendable to 100m) 2.4 GHz band (crowded) 1 Data (700 Kbps) and 3 voice channels, up to 3 Mbps Widely supported by telecommunications, PC, and consumer electronics companies Few applications beyond cable replacement Bluetooth

Optimized for one-way communications Short messaging Message broadcast from all base stations Simple terminals Mostly replaced by cellular Similar systems Electronic shelf labels Paging Systems

7.5 Ghz of “free spectrum” in US (underlay) High data rates, up to 500 Mbps UWB is an impulse radio: sends pulses of tens of picoseconds(10-12) to nanoseconds (10-9) Duty cycle of only a fraction of a percent A carrier is not necessarily needed Multipath highly resolvable: good and bad Limited commercial success to date Ultra wideband Radio (UWB)

Low-Rate WPAN Data rates of 20, 40, 250 Kbps Support for large mesh networking or star clusters Support for low latency devices CSMA-CA channel access Very low power consumption Frequency of operation in ISM bands IEEE / ZigBee Radios

Information exchange between people and/or devices, anywhere, anytime home applications : new intelligent devices that interact with each other (smart homes) connectivity between business machines; phones, computers, servers, etc Wireless entertainment : provide wireless access to multi-media contents Wireless internet access Wireless sensor networks Automated cars – UAVs In-body networks Cannot pick a segment for success, but foresee a bright future for the whole industry Wireless vision

We will have many different systems and standards Different segments have different specs Multimedia Requirements QoS depends on the application Rate and delay requirements Requires cross layer design Future systems VoiceDataVideo Data rate8-32 Kbps1-100 Mbps BER PER< 1%0 Delay< 100ms- TrafficContinuousBurstyContinuous

Wireless evolution Rate Mobility 2G3G 4G b WLAN 2G Cellular Other issues: Coverage Latency Cost Energy n Wimax/3G

System constrains Rate, delay, energy System optimization System adaptation (link, MAC, network, application) resource management Scheduling Data prioritization Resource reservation Access scheduling Achieve robustness by using diversity Link diversity (antenna, channel) Route diversity Power control Cross layer design

Wireless channels are a difficult and capacity-limited broadcast communications medium Traffic patterns, user locations, and network conditions are constantly changing Applications are heterogeneous with hard constraints that must be met by the network Energy and delay constraints change design principles across all layers of the protocol stack Design challenges

Ad hoc/mesh wireless networks flexible/ (robust) network infrastructure Indoor/outdoor Cellular/LAN integration Cooperative networks Maximize network capacity Relay nodes Network coding Cross layer design critical Emerging technologies

For data collection and distributed control Hard energy/delay constraint Each node sends only finite number of bits Energy/delay trade offs Nodes cooperate in transmission, reception, and processing Optimization for node/network lifetime Design nodes cooperation Completely new framework Must consider TX, RX, and processing Wireless sensor networks

Underlay Cognitive radios cause minimal interference to primary users Interweave Cognitive radios find spectral holes Overlay Cognitive radios overhear and enhance noncognitive radio transmissions Cognitive Radio

Spectral Allocation by ? Worldwide spectrum controlled by ITU-R Plays a key role in communication sector growth Allocation strategies Dedicated/public band Auction bands Overlay/Underlay Cognitive radios Innovations are still needed Spectrum Regulation

The wireless vision encompasses many exciting systems and applications Technical challenges in all layers of the system Cross-layer design emerging as a key theme in wireless Existing and emerging systems provide excellent quality for certain applications but poor interoperability. Standards and spectral allocation heavily impact the evolution of wireless technology Summary

Reading Carlson Ch. 1 Proakis Ch. 1