RADIO SYSTEMS – ETI 051 Contents Lecture no: 1 • Course information • What is a radio system? Introduction • Some concepts Ove Edfors, Department of Electrical and Information Technology Ove.Edfors@eit.lth.se 2010-03-16 Ove Edfors - ETI051 2 Course web-site • All course information is available at: http://www.eit.lth.se/course/ETI051 COURSE INFORMATION • Most important: – Continuously updated schedule – Lecture handouts (available before each lecture) – Exercises – Any additional material 2010-03-16 Ove Edfors - ETI051 3 2010-03-16 Ove Edfors - ETI051 4
Textbook Schedule • Three recurring components – Lectures : [Ove Edfors] Wireless Wireless • Published by Wiley/IEEE Normal times: TUESDAYS (10-12) and THURSDAYS (10-12) Press in September 2005. Communications Communications NOTE: Several exceptions, todayz – Exercise classes : [Johan Kåredal] • Available through most on- FRIDAYS (08-10) line web book stores NOTE: Several exceptions! SEE DETAILED SCHEDULE ON COURSE HOME PAGE! SEE DETAILED SCHEDULE ON COURSE HOME PAGE! • Same book as in the Channel Modelling course (ETI085) • Two special components Andreas F. Molisch – Student presentations : • Authored by Andreas F. At the end of the course Molisch, former professor of – Written exam : Radio Systems at Lund University/LTH. Friday, May 28, 14.00-19.00 2010-03-16 Ove Edfors - ETI051 5 2010-03-16 Ove Edfors - ETI051 6 Lectures Exercise classes • Overview of the contents in the textbook • Exercises from the textbook • Additional material • During exercise classes, some of the exercises will be analysed in detail • Application examples • By working through the exercises beforehand, you can give valuable input on which exercises to focus on during classes 2010-03-16 Ove Edfors - ETI051 7 2010-03-16 Ove Edfors - ETI051 8
Reading and presenting a Written exam journal paper • During the course you will read and give a short presentation of a recent (scientific) journal paper in the area. • How? • Performed in groups of TWO or THREE students. – Total of 5 hours • Propose your own topic/paper or select from a list of – Part A : 1.5 hours – closed book questions (15 points) suitable papers. – Part B : 3.5 hours – open book problems (15 points) • Presentations (about 10 minutes each) will be done at the end of the course. • When? Friday, May 28, 14.00-19.00 • THIS IS A COMPULSORY PART OF THE COURSE! THIS IS A COMPULSORY PART OF THE COURSE! Participate in a group that reads and presents a paper. Participate in a group that reads and presents a paper. Attend the presentations given by other students. Attend the presentations given by other students. 2010-03-16 Ove Edfors - ETI051 9 2010-03-16 Ove Edfors - ETI051 10 Radio system? • From Merriam-Webster Dictionary – Radio: 1 : of, relating to, or operated by radiant energy 2 : of or relating to electric currents or phenomena (as electromagnetic radiation ) of frequencies between WHAT IS A about 15 kHz and 100 GHz – System: RADIO SYSTEM? 1 : a regularly interacting or interdependent group of items forming a unified whole • ”Radio systems” can be used for many purposes, e.g. – Detection and ranging (Radar) – Astronomical observation (Radio telescope) – Heating food (Microwave oven) – Navigation (GPS, etc.) – Communication (Cellular telephony, etc.) 2010-03-16 Ove Edfors - ETI051 11 2010-03-16 Ove Edfors - ETI051 12
Some questions to ask Example: Microwave oven Why is 2.45 GHz used? • What do we want to achieve with our system? Dielectric permittivity and dielectric loss of water between 0°C and 100°C – This gives us design constraints (system requirements) • What frequency band should we use? – Properties of the radio channel changes with frequency – Radio spectrum is firmly regulated • Which technology should we use? – Not all technologies can perform the task – Cost is important (design, production, deployment, etc.) Most absorbtion here Microwave oven here Graph from www.sbu.ac.uk/water/ microwave.html 2010-03-16 Ove Edfors - ETI051 13 2010-03-16 Ove Edfors - ETI051 14 Example: Human eye Example: Radar Why is the human eye sensitive at the electromagnetic wavelengths Distance d (frequency band) we call visible light? Calculation of distance Transmitted pulse Is it a coincidence or a ”clever Received pulse 8 × Δt design”? d = c × Δt = 3 × 10 2 2 Time (This is not radio waves, but it illustrates Δ t the importance of the used frequency band.) The accuracy of our ”measured” time delay determines the accuracy of the ”measured” distance. Does this have any influence on the bandwidth requirement? Graph from http://earth.usc.edu/geol150/weather/ 2010-03-16 Ove Edfors - ETI051 15 2010-03-16 Ove Edfors - ETI051 16
Example: Mobile telephony Amplifiers with low dynamic range can be made more power efficient than highly linear amplifiers. Does this affect the choice of modulation SOME CONCEPTS technique? Radio signal Radio signal Amplitude Amplitude 2010-03-16 Ove Edfors - ETI051 17 2010-03-16 Ove Edfors - ETI051 18 SINGLE LINK A rough breakdown into areas Link budget – a central concept ”POWER” [dB] This is a P T X Fundamental problems simple L f ,T X in wireless communications G a,T X version of the link budget. Gain Propagation Digital transmission Mobile L p CRITERION and antennas over wireless communications TO MEET: channels systems Loss Required G a, R X L f ,R X C/N at Deterministic Probabilistic Modulation Multiple access C receiver input N Channel models Speech and Cellular telephony Noise reference level channel coding Narrow-band Wide-band Speech coding Equalization channels channels Antenna Noise gain Wireless data Antenna Propagation Transmitter Receiver Transmitter Receiver Diversity networks Antennas gain loss Transmit Feeder Feeder Received power loss loss power 2010-03-16 Ove Edfors - ETI051 19 2010-03-16 Ove Edfors - ETI051 20
SINGLE LINK SINGLE LINK Link budget – depends on what? Required C/N – a central concept • Some examples: Quality IN Quality OUT – Regulations (transmit power, etc.) (C/N) DETECTOR DETECTOR – Antenna placement (feeder loss) – Antenna type and quality (antenna gain) – Frequency band and environment (propagation loss) DETECTOR CHARACTERISTIC The detector characteristic – Receiver design (noise power) is different for different Quality OUT – Modulation, coding and signal processing (required C/N) system design choices. REQUIRED QUALITY OUT: This is a rather This is a rather complex issue that we complex issue that we Audio SNR will spend quite some will spend quite some Perceptive audio quality effort on. effort on. Bit-error rate Quality IN Packet-error rate (C/N) etc. 2010-03-16 Ove Edfors - ETI051 21 2010-03-16 Ove Edfors - ETI051 22 SINGLE LINK THE RADIO CHANNEL Required C/N – depends on? Some properties • The most important: This one is usually • Path loss – Required output quality determined by – Roughly, received power decays with some exponent the application of distance • ... then, through the detector characteristic: ∝ × − Received power Transmitte d power Distance Propagatio n exponent – Signal constellation • Large-scale fading – Modulation type – Large objects, compared to a wavelength, in the – Error-correcting codes All these will have signal path obstruct the signal to be chosen in a – Equalization system design – Antenna processing process • Small-scale fading – Synchronization – Objects reflecting the signal causes multipath – etc. propagation from transmitter to receiver 2010-03-16 Ove Edfors - ETI051 23 2010-03-16 Ove Edfors - ETI051 24
THE RADIO CHANNEL THE RADIO CHANNEL Path loss Large-scale fading TX RX Received power Received power [log scale] 2 ∝ 1 / d D D C C 4 ∝ 1 / d d B B Movement A A Position A B C D Distance, d [log scale] 2010-03-16 Ove Edfors - ETI051 25 2010-03-16 Ove Edfors - ETI051 26 THE RADIO CHANNEL THE RADIO CHANNEL Small-scale fading Small-scale fading (cont.) Signal on reflected path arrives later Signal on direct TX RX TX RX path arrives first Constructive (self-)interference Destructive (self-)interference With a large number of With a large number of reflection points the reflection points the interference pattern interference pattern = = + + becomes extremly becomes extremly complicated. complicated. 2010-03-16 Ove Edfors - ETI051 27 2010-03-16 Ove Edfors - ETI051 28
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