Digital Communications EEE3012 - Spring 2019
Instructor Dong In Kim dikim@skku.ac.kr 299-4585 office hours: Wed/Fri (3 4pm) in 23528 TA by appointment Jong Ho Moon (299-4663 or menia1492@naver.com) hand in all assignments to room 23517 (or in class)
Text Textbooks John G. Proakis and Masoud Salehi Fundamentals of Communication Systems, 2 nd Ed. References Simon Haykin Communication Systems, 5 th Ed. Bernard Sklar Digital Communications, 2nd Ed. Prentice Hall. 2001. Schaum s outlines (Hsu), 2 nd Ed
Web Course web-page notes assignments handouts/old test/exams userid: ece password: pluto
Grading Grading policy assignments 10% final project 20% midterm 25% final 45%
Syllabus 1. Baseband Transmission of Digital Signals (2 weeks) effect of limited channel bandwidth (ISI) pulse shaping with zero ISI effect of channel noise realization of matched filter adaptive equalizer 2. Signal-Space Analysis (2 weeks) geometric representation of signals design of optimum receiver correlation receiver matched-filter receiver performance of error
Syllabus 3. Band-Pass Transmission of Digital Signals (4 weeks) coherent detection of modulated signals phase-shift keying (PSK) quadrature PSK (QPSK) M-ary PSK (MPSK) M-ary quadrature amplitude modulation (QAM) coherent frequency-shift keying (FSK) noncoherent detection of modulated signals optimum quadrature receiver noncoherent orthogonal modulation noncoherent binary FSK differential PSK
Syllabus 4. Multicarrier Modulation and OFDM (1.5 weeks) orthogonal frequency-division multiplexing (OFDM) modulation/demodulation in OFDM systems OFDM system implemented via FFT algorithm applications of OFDM wireless LANs LTE cellular systems 5. Information and Forward Error Correction (2.5 weeks) channel capacity linear block codes convolutional codes turbo codes
Syllabus 6. Digital Transmission in Fading Multipath Channels (2 weeks) channel model for time-varying multipath channels performance of binary modulation in Rayleigh fading channels multiple antenna systems (e.g., MIMO) spread-spectrum communication systems direct-sequence spread spectrum frequency-hopped spread spectrum digital cellular communication systems 7. Ultra-low Power Communications for IoT Devices (1 week) ambient backscatter communication bi-static scatter radio
주요성과 주요논문및기술성과 초저전력 (µwatt) Ambient Backscatter 무선통신기술 김동인교수 1895년마르코니가최초로 3km 무선통신에성공한이후로 1990년대에셀룰러이동통신의보급에이르기까지무선통신분야는지속적으로진화하면서일상의삶에많은변화를가져왔다. 그러나최근에들어서서사물인터넷 (IoT: Internet-of-Things) 의등장으로기기간 (M2M: Machine-to-Machine) 통신의필요성이커지면서저전력으로동작하는 IoT 센서의에너지자립을위한초저전력 (ultra-low power) 무선통신기술의개발이많은연구자의주목을받고있다. 특별히, Ambient Backscatter 무선통신기술은소모전력이 µwatt 정도의초저전력으로동작이가능하여 M2M 통신의실현에매우중요한기술로인식되고있다. 무선에너지하비스팅통신융합연구센터에서는마이크로파 (RF) 기반원거리무선충전기술을개발하여최근 50m 거리에서무전원 (battery-less) 으로동작하는센서플랫홈을구현하여성공적으로시연을하였다 ( 데모영상 : http://www.youtube.com/ watch?v=9lpe1_1xoyq). 이러한원거리무선충전으로 µwatt 단위의에너지를공급받아동작하는 IoT 센서의경우환경오염, 대기변화등측정한데이터를 AP에업로드하기위해서는초저전력으로동작하는새로운무선통신기술의개발이요구되고있다. 그림 1. Backscatter 무선통신시스템 (a) 송신부, (b) 수신부 그림 2. Ambient Backscatter 무선통신시스템구조 Ambient Backscatter 무선통신기술의동작은그림 1에서 TV 또는셀룰러 / 와이파이신호등주변의전자파신호를이용하여 IoT 센서에수신된전자파를센서의안테나를통해흡수 ( 임피던스정합, 즉안테나의임피던스와 load modulator의임피던스를일치시키는경우 ) 하거나또는반사 ( 임피던스부정합 ) 하는간단한안테나스위칭을통해센서의데이터를전송할수있다. 따라서종래의마르코니무선통신에서신호의변조및전송과정에서필요한 amplifier, mixer, A/D converter 등많은전력을소모하는능동소자를사용하지않고, 그림 2의 Backscatter transceiver A에서수동소자만으로간단히안테나스위칭을통해주변의전자파신호를흡수 ( 데이터 0 )/ 반사 ( 데이터 1 ) 하는동작으로인접한 Backscatter transceiver B에서수신에너지의변화를감지하여전송된데이터를쉽게복호할수있다. Backscatter 무선통신에서데이터전송을위한안테나스위칭에소모되는전력은 µwatt 단위이며, 특별히데이터 0 을전송하는경우주변의전자파를흡수하여에너지를수집할수있어센서의수명 (lifetime) 을길게유지할수있는이점이있다. 현재연구의흐름은크게두방향으로진행되고있으며, Ambient Backscatter 기반대규모 (massive) M2M 통신에서 IoT 센서상호간에미치는간섭을제거할수있는주파수천이 (FS: frequency-shifting) 방식과, 주사용자 (PU: Primary User) 의신호및스펙트럼을동시에활용하여이차사용자 (SU: Secondary User) 에해당하는 IoT 센서의에너지및스펙트럼의효율을동시에높여주는 Cognitive Backscatter 통신방식이이에해당한다. 전자의경우는미국워싱톤대학의센서연구그룹에서주도적으로연구를수행하고있으며, 후자의경우는본연구센터와국제공동연구를수행하고있는싱가포르난양공대 (NTU) 와함께선도적인연구를수행하고있다. 위의국제공동연구를수행하여최근에무선통신분야최우수저널인 IEEE Communications Surveys & Tutorials (Impact Factor: 20.230) 에 Ambient Backscatter Communications: A Contemporary Survey 및 IEEE Wireless Communications (Impact Factor: 9.202) 에 Ambient Backscatter Assisted Wireless Powered Communications 을각각발표하고, 아울러 Cambridge University Press 출판사의지원으로 Ambient Backscatter Communication Networks 의교재를이분야에서최초로집필하여동분야의연구를선도적으로이끌고있다.