Wireless & Cellular Communications Slides are adopted from Lecture notes by Professor A. Goldsmith, Stanford University. Instructor presentation materials for the book: Wireless Communications, 2nd Edition, A. F. Molisch, 2010. Fall 2015 RezaMohammadkhani,PhDEmail: Mohammadkhani@gmail.com University of Kurdistan, Iran. WWW:eng.uok.ac.ir/mohammadkhani 2 Outline Overview of Wireless Communications Wireless Channel Models Path loss, Shadowing, Fading models (statistical models) Capacity of Wireless Channels Digital Modulation & its Performance Diversity Multicarrier Modulation OFDMA Spread Spectrum Multiuser Systems FDMA, TDMA, CDMA
Grading Policy 3 Midterm Exam 30% Final Exam 40% Project(s) 20% Homework 10% References 4 Required: A. Goldsmith, Wireless Communications, Cambridge University Press, 2005. Recommended books: Andreas Molisch, Wireless communications, Wiley-IEEE Press, 2nd Ed, 2010. D. Tse and D. Vaswanth, Fundamentals of Wireless Communications, Cambridge University Press, 2005. [Online version is available]
5 Overview of Wireless Systems History of wireless 6 Ancient Systems Smoke Signals, Carrier Pigeons, Maxwell: theory Hertz fundamental experiments confirming Maxwell s theory 1890-1905 First experiments for wireless information transmission Tesla, Marconi
7 History of wireless (2) Many sophisticated military radio systems were developed during and after WW2 Development of cellular telephony: 1950s 1980s exponential growth since 1988, with about 6 billion users worldwide today 8 History of wireless (3) Cellular systems GSM (Global System for Mobile communications) First deployment in early 1990s in Europe In 2005, more than 1 billion users IS-95 (cdmaone) 2nd-generation system based on different multiple-access scheme Used mainly in US and Korea PDC (Pacific Digital Cellular) Third-generation systems (3G) Several different standards All based on CDMA
Current/Emerging Wireless Systems 9 Current: 4G Cellular Systems (LTE-Advanced) 4G Wireless LANs/WiFi (802.11ac) Satellite Systems Bluetooth.. Emerging 5G Cellular and WiFi Systems mmwave Systems Ad/hoc and Cognitive Radio Networks Energy-Harvesting Systems Much room For innovation Future of Wireless Communications 10 Next-generation Cellular Wireless Internet Access Wireless Multimedia Sensor Networks Smart Homes/Spaces Automated Highways In-Body Networks All this and more
11 Internet of Things (IoT) 12 Types of Wireless Services
Broadcast 13 1. The information is only sent in one direction. 2. The transmitted information is the same for all users. 3. The information is transmitted continuously. 4. In many cases, multiple Txs send the same information. Paging 14 1. The user can only receive information, but cannot transmit. 2. The information is only received by a single user. 3. The amount of transmitted information is very small.
15 Cellular Phones 1. Bidirectional information flow. A user can transmit and receive information at the same time. 2. User can be anywhere. 3. A call can originate from the network or the user. 4. A call is intended for a single user. 5. High mobility of the users. 16 Cordless Phones The BS does not need to find the location of the MS. No central system. Each user has one BS. A direct connection from BS to MS. No network operator to charge the user! Cordless phone connecting a single mobile user device to a public landline system Wireless PABX wireless Private Automatic Branch exchanges (PABXs)
Wireless LANs & PANs 17 Wireless Local Area Network (WLAN) Connecting a laptop computer to the Internet. data rate: 1-100 Mbit/s Ad-hoc network Personal Area Network (PAN) -- coverage area smaller than WLAN Bluetooth Body Area Networks data rate > 100 Mbit/s Body-Area Networks Fixed Wireless & Satellite 18 Fixed wireless access systems Long distances between BS and MS No mobility requirements high data rates (it can also be used for voice systems) WiMax standard (IEEE 802.16) Satellite cellular communications Cover very large area No high density (Erlang/km^2) communications from within buildings is almost impossible.
19 Range vs. Data-rate [Molisch, 2010] 20 Data rate vs. Mobility
21 Use of Spectrum Spectrum dedicated to service and operator Spectrum dedicated to a service Free spectrum Use of Spectrum 22 Spectrum dedicated to service and operator Spectrum dedicated to a service Free spectrum 2.45 GHz is the best known example it is allowed to operate microwave ovens, WiFi LANs, and Bluetooth wireless links, among others, in this band. Ultra Wide Bandwidth systems (UWB) Adaptive spectral usage or cognitive radio
23 Spectral Reuse (why?) In licensed bands and unlicensed bands BS Cellular Wifi, BT, UWB, Reuse introduces interference 24 Cognitive Radios I P CRTx CRRx NCR NCR CR MIMO Cognitive Underlay Cognitive radios support new users in existing crowded spectrum without degrading licensed users Utilize advanced communication and DSP techniques Coupled with novel spectrum allocation policies Multiple paradigms CR NCRTx Cognitive Overlay NCRRx (MIMO) Underlay (interference below a threshold) Interweave finds/uses unused time/freq/space slots Overlay (overhears/relays primary message while cancelling interference it causes to cognitive receiver)
25 Duplexing & Multiple Access 26 Duplexing & Multiple Access Within each frequency band, multiple users need to communicate with one BS (multiple access) Cellphones have to be able to transmit & receive voice communications (Duplexing)
27 DUPLEX Frequency-division Duplex (FDD) Examples: Nordic Mobile Telephony (NMT), Global System for Mobile communications (GSM), Wideband CDMA (WCDMA) 28 DUPLEX Time-division Duplex (TDD) Examples: Global System for Mobile communications (GSM), Wideband CDMA (WCDMA)
29 MULTIPLE ACCESS Freq.-division multiple access (FDMA) Examples: Nordic Mobile Telephony (NMT), Advanced Mobile Phone System (AMPS) 30 MULTIPLE ACCESS Time-division multiple access (TDMA) Example: Global System for Mobile communications (GSM)
31 MULTIPLE ACCESS Code-division multiple access (CDMA) Examples: CdmaOne, Wideband CDMA (WCDMA), Cdma2000 32 MULTIPLE ACCESS Carrier-Sense multiple access (CSMA)
33 References 34 A. Goldsmith, Wireless Communications, Cambridge University Press, 2005. Andreas Molisch, Wireless communications, Wiley-IEEE Press, 2nd Ed, 2010. Wireless Communications lecture notes by Professor A. Goldsmith, Stanford University.