Lecture 1 - September Title 26, Ultra Wide Band Communications

Transcription

1 Lecture 1 - September Title 26, 2011 Ultra Wide Band Communications

2 Course Presentation Maria-Gabriella Di Benedetto Professor Department of Information Engineering, Electronics and Telecommunications (DIET) Jocelyn Fiorina Associate Professor SUPÉLEC, Département de Télécommunications Luca De Nardis Assistant Professor Department of Information Engineering, Electronics and Telecommunications (DIET) Guido Carlo Ferrante Master Thesis student Department of Information Engineering, Electronics and Telecommunications (DIET) 2

3 Course Presentation UWBCOM Mailing List Course Website 3

4 Course Notes Understanding Ultra Wide Band Radio Fundamentals by Maria-Gabriella Di Benedetto & Guerino Giancola Published by Prentice Hall ISBN: Published: June 17, 2004 Copyright

5 Course Organization PART 1 UWB Basics Introduction to UWB Communications Generation of UWB radio signals Spectral characteristics of UWB radio signals PART 2 UWB single user communications Link Budget for an UWB radio link Receiver structures for AWGN channels Receiver structures for multipath-channels PART 3 UWB multi user communications MUI models for Impulse Radio Time Reversal PART 4 UWB special features Pulse Shaping in UWB Locationing and Positioning with UWB 5

6 Practice Work List of practice work lessons that will be given during the course (Adopted simulation tool: MATLAB ) UWB vs. non UWB Generation of 2PPM-TH-UWB and 2PAM-TH-UWB signals Shaping the spectrum of a 2PPM-TH-UWB signal by changing the properties of the TH code (periodicity and cardinality) Link Budget for UWB links Performance of an UWB receiver in the presence of AWGN channels Performance of an UWB receiver in the presence of multipath-affected channels Theoretical performance of multi-user UWB networks Verification of the validity of the SGA Evaluation of the effect of differentiation on the spectrum of an UWB signal Meeting the emission masks Accuracy of Least Square Error algorithms 6

7 Lesson 1 Introduction to UWB Communications

8 UWB in modern communication systems (1/3) The last few years have witnessed an increased interest of both chip manufacturing companies and standardization bodies in UWB 8 and others

9 UWB in modern communication systems (2/3) Interesting UWB features are: 1. Flexibility Spectral flexibility (coexistence) Flexibility in providing wireless access to heterogeneous applications. Flexibility in system design (cross-layer system optimization). 2. Robustness Robustness to interference (external and internal) 3. High-precision ranging capabilities 4. High capacity 5. Low cost 9

10 UWB in modern communication systems (3/3) Main challenges for UWB are: 1.Acquisition and synchronization of UWB signals 2.Power constraints 3.Accurate propagation models 4.Accurate interference models 5.Efficiency of implementation 10

11 UWB domain of application (1/2) Increased interest towards UWB Coexistence: Strong power emission constraints imposed by regulatory bodies UWB is emerging as an appealing transmission technique for applications requiring either high bit rates over short ranges or low bit rates over medium-to-long ranges 11

12 UWB domain of application (2/2) High bit rates over short ranges Low bit rates over medium to long ranges Long-range sensor networks Cable replacement for high bit rate data transfers WPANs for multimedia traffic Non-real-time data applications ( , instant messaging ) Wearable devices 12

13 What is UWB? (1/5) A signal is UWB if its bandwidth is large with respect to the carrier or center frequency of the spectrum, that is, if its Fractional Bandwidth (FB) is high. FB = f H ' f & f H + $ % 2 f L L #! " f L f H 13

14 What is UWB? (2/5) The common adoption of the term UWB comes to us from the radar community, and refers to electromagnetic waveforms with an instantaneous fractional bandwidth greater than about Traditionally, UWB signals have been obtained by transmitting very short pulses with typically no Radio Frequencies modulation In communication systems, very short refers to a duration of the pulse that is typically about a few hundred picoseconds This technique goes under the name of Impulse Radio (IR) 14

15 What is UWB? (3/5) Impulse Radio was the primal technique for transfering information over the wireless medium In Guglielmo Marconi s first experiments, back in , Morse Code messages were transmitted over two miles using pulsed transmission. Marconi's handwritten notes for the specifications for the '7777' Patent Marconi s 7777 Patent 15

16 What is UWB? (4/5) In December 1900, Reginal Fessenden used impulse radio signals for transmitting speech over one mile In 1946 a remarkable microwave radio relay system was developed by Black, Beyer, Grieser, and Polkinghorn. This system was based on the transmission of pulses that were position-modulated and ensured two-way voice transmission over radio links totalling 1600 miles, and one-way over 3200 miles During the 1970s, the first patent for an impulse radio receiver to be used in communication systems is filed by Gerald F. Ross. 16

17 What is UWB? (5/5) The term Ultra Wide Band was coined by the U.S. Department of Defense in 1989 During the 1990s, relevant researches about Impulse Radio are carried out at the University of Southern California by Scholtz and Win. During the 1990s, a few small and medium-sized enterprises reintroduced the idea of wireless communications based on the impulse radio paradigm 17

18 FCC regulation about UWB emissions (1/6) In order to verify the possibility for UWB systems to coexist with other existing systems, several measurement campaigns were performed in the United States by research institutes and agencies. Measurement reports were commissioned to the National Telecommunications and Information Administration (NTIA) by the Federal Communication Commission (FCC) The final report was released by NTIA in March

19 FCC regulation about UWB emissions (2/6) The most influential milestone in the history of UWB was set in 2002, when the FCC approved in the U.S. the first guidelines allowing the intentional emission of UWB signals and specified emission masks 19

20 FCC regulation about UWB emissions (3/6) In the FCC document, UWB is presented as a technology with enormous potentials In the same report, however, we find explicit concern about the need for emission masks, due to the unknown effects that UWB transmissions may have on other communication systems. 20

21 FCC regulation about UWB emissions (4/6) FCC indoor emission mask FCC outdoor emission mask 21

22 FCC regulation about UWB emissions (5/6) According to the FCC rules, the UWB concept is not limited to Impulse Radio Any signal is UWB provided that its fractional bandwidth is greater than 0.2 or its occupied bandwidth is greater than 500 MHz. The 500 MHz minimum bandwidth limit sets a threshold at 2.5 GHz Below the threshold signals are UWB if their fractional bandwidth exceeds 0.20 Above the threshold signals are UWB if their bandwidth exceeds 500 MHz 22

23 FCC regulation about UWB emissions (6/6) The effect of the FCC release was twofold 1. The FCC regulation of UWB emissions raised the interest of major chip manufacturers 2. Discussions were triggered around the advantage of the Impulse Radio scheme vs. the traditional carrier-based continuous transmission alternative 23

24 IEEE UWB standardization activities (1/4) The dichotomy between impulsive and nonimpulsive UWB was reflected in the diatribe on UWB standardization, in particular in the framework of the IEEE High Rate Alternative PHY Task Group (IEEE a Task Group ) The IEEE a Task Group is working to provide a higher speed PHY enhancement amendment to for applications involving imaging and multimedia 24

25 IEEE UWB standardization activities (2/4) Two different proposals for a physical layer based on UWB have been under discussion during several years: a Multi-Band (MB) approach combining frequency hopping with Orthogonal Frequency Division Multiplexing (OFDM) a second approach using Direct-Sequence UWB, or DS-UWB, which preserves the original pulsed nature of UWB In the minutes of a IEEE a Task Group meeting held in November 2004, the DS-UWB had obtained a majority of votes. A final agreement was however never reached. 25

26 UWB standards for high-rate data networks (3/4) 26

27 UWB standards for high-rate data networks (4/4) After three years of dispute without a decision being reached, the IEEE near unanimously voted to kill the a task group. The reason for the disband was that consensus could not be reached between the two groups behind MB-OFDM and DS-UWB as to which technology would become the a standard. Each group formed its own consortium: WiMedia Alliance (for MB-OFDM) ( UWB Forum (for DS-UWB) (not exists anymore) 27

28 UWB standards for low-rate data networks (1/2) Regarding the introduction of UWB in low-rate, location-enabled applications, standardization took its first steps within the IEEE a Task Group, that is an evolution of IEEE Standard for low-rate WPANs with multi-month to multi-year battery life. IEEE features include data rates of kbps, power management to ensure low power consumption, and low complexity. 28

29 UWB standards for low-rate data networks (2/2) Within the , the Low Rate Alternative PHY Task Group (TG4a) is working to provide high precision ranging / location capability (1 meter accuracy and better) and ultra low power. In March 2005, TG4a selected two optional PHYs consisting of: a UWB Impulse Radio (operating in unlicensed UWB spectrum) a Chirp Spread Spectrum (operating in unlicensed 2.4GHz spectrum). 29

30 Band Plan for IEEE a (1/2) IEEE a proposes a uniform band plan for the UWB devices Narrower Band ~ 500 MHz TG4a Proposed Band Plan Frequency MHz Wider Band ~ 1300 MHz 30

31 Band Plan for IEEE a (2/2) a devices will operate in two frequency ranges: Low Frequency Band (LBF): MHz (mandatory) High Frequency Band (HFB): MHz (optional) TG4a Proposed Band Plan Frequency MHz LBF HBF 31

32 Worldwide Band Plan DAA: Detect And Avoid USA Japan (DAA) Europe (DAA) Europe Japan 4 TG4a Proposed Band Plan Frequency MHz a LBF a HBF