From Maxwell s Equations to Cognitive Radio

Transkript

1 From Maxwell s Equations to Cognitive Radio Friedrich K. Jondral Delft (The Netherlands), November 15, 2007 Prof. Dr.rer.nat. F. Jondral

2 Topics Historic Remarks Radio Communications Software Defined Radio Software Communications Architecture Cognitive Radio Regulation 2

4 Some Important Events UMTS, WLAN, CR GSM, SDR digital signal processing, DR Shannon, television transistor audio broadcast Marconi's experiments Hertz's experiments Maxwell equations

5 The Starting Point Maxwell's equations (1873) v v v. rot H = J + D v v. rot E = B v div D =ρ v div B = 0 James Clerk Maxwell, H v E v D v B v v J ρ magnetic field electric field electric displacement magnetic flux density current density volume charge density There is nothing as practical as a convincing theory. 5

6 Generation of Sine Waves z θ r Heinrich Hertz, x Karlsruhe 1887: Electromagnetic waves propagate through free space Hertzian dipole Metallic walls reflect electromagnetic waves Electromagnetic waves exhibit the properities of light waves (reflection, diffraction, refraction, polarization, interference,...) 6

7 Pioneering Radio Experiments Guglielmo Marconi First radio transmission experiments 1899 over the English Channel 1901 transatlantic from Poldhu (Cornwall) to Signal Hill / St. John s (Newfoundland) 7

8 Modulation { c i } () = () π + () +ϕ() s t a t cos 2 f f t t t α amplitude, f c carrier frequency ϕ phase, f i information frequency analog digital multi carrier spread spectrum AM ASK based on FFT DS SSB FSK DMT FH RSB PSK OFDM TH FM QAM COFDM 8

9 Digitalization / Coding Sampling theorem, 1949 If the real signal s(t) is integrable over the whole real axis band limited by B, i.e. s( t) o S( f ): S( f) = 0 f B then s(t) is determined by its values s(kδt), k Ζ, periodically taken at the time difference Δ= t 1 2B : () = ( Δ ) s t s k t k= ( Δ ) ( Δ ) sin2πb t k t 2πB t k t Claude E. Shannon, Source coding Channel coding (FEC) Cryptographic coding 9

10 Networking Radios are normally integrated into networks In many cases radio networks serve as access networks to fiber optic backbones We have to distinguish commercial, security and military networks Autarky is of special interest for military and security applications Military applications may call for low probability of intercept and for advanced crypto requirements 10

11 Audio Receivers Philips Philetta, 1958 TELEFUNKEN Gavotte, 1971 Nordmende Carmen,

12 Professional Short Wave Receiver (analog) TELEFUNKEN TFK801, ca

13 Professional Short Wave Receiver (analog) Funkwerke Köpenik EKD 500, ca

14 Professional Short Wave Receiver (digital) DASA E

15 Mobile Phones Apple i-phone, 2007 Motorola Razor,

17 Mobile Spectrum in Europe , f [MHz] GSM 5150 DECT UTRA- TDD 5350 UTRA- FDD MSS ISM WLAN WiMAX Future WiMAX 17

18 Mobile Standards mobility/range high velocity Source: Klaus-D. Kohrt: 3G und WIMAX Konkurrenten oder Partner? ntz, Heft 1, 2007, S vehicle pedestrian stationary long distance traffic urban traffic walking nomadic fixed inhouse personal environment GSM/GPRS DECT Bluetooth 3G/UMTS EDGE flash OFDM HSPA WLAN (IEEE x) 3G successor systems >2014 IEEE e WiMAX IEEE Mbit/s user data rate 18

19 Hierarchical Cells Zone 4: Global Zone 3: Suburban Zone 2: Urban Zone 1: In-Building World-Cell Macro-Cell Micro-Cell Pico-Cell Source: UMTS Task Force Report 19

20 4 th Generation Network? System Structure beyond 3G : horizontal handover between a system possible return channels vertical handover between systems distribution layer DAB and/or DVB full coverage global roaming full mobility not necessary individual links Increased mobility and cell size cellular layer hot spot layer personal network layer 2G: e.g. GSM IMT-2000 UMTS full coverage and hot spots global roaming full mobility individual links full coverage hot spots global roaming local mobility individual links short range communication global roaming individual links fixed (wired) layer X X X X X X X X X X X X X no mobility global roaming individual links 20

21 The Key Question Personal Area Networks Wireless Local Area Networks Cordless Phones Cellular Networks Broadcast Networks Satellite Networks Pico Cells Micro Cells Macro Cells Global Cells Voice Data Video Multimedia Location & Navigation Infotainment What does a subscriber need? One specific device for each and every situation or one device that serves all situations? 21

22 Standards Definition: A communications standard is a set of documents that describes the functions of a communication system in such a way that a manufacturer can develop terminals or infrastructure equipment on this basis. Remarks: (i) Standardization is one necessary condition for making a communication system successful on the market. (ii) Today, standardization encompasses all kinds of communication networks. Will standards continue to play an outstanding role in future communication systems? 22

23 Standards Summary Radio communication standards define transmission systems w.r.t. specific services like voice, video, data, multimedia, broadcast, location, navigation etc. The accompanying transmission modes and protocols depend on data rate bandwidth, velocity, type of service etc. Mobile radio communication starts with the channel properties. 23

25 Definitions 1) Digital Radio (DR): The baseband signal processing is invariably implemented on a DSP. Software Radio (SR): An ideal SR directly samples the antenna output. Software Defined Radio (SDR): An SDR is a realizable version of an SR: Signals are sampled after a suitable band selection filter. transmit receive radio frequency RF radio frontend analog-to-digital conversion A/D control (parametrization) baseband processing data processing to user from user 1) According to J. Mitola,

26 Radio Types since 1980 Time Frame Radio Type Signal Processing Hardware Adaptivity Features Services 1980 μp-controlled Analog Radio Analog circuits, μp AGC, AFC Voice 1990 Digital Radio (DR) DSP ALE with ACA, adaptive filters, equalizers Voice, data, SMS 2000 Software Defined Radio (SDR) FPGA Adaptive coding and modulation, multiband, multistandard, multirole Multimedia 2010 Cognitive Radio (CR) GPP Location, spectral environment, velocity Location based applications, sensor networks, internet of things 26

27 Radio Evolution Adaptivity increases No. of transistors on an IC Moore s law: Cognitive Radio The packing density of transistors on an integrated circuit increases by a factor of two every two years. Software Defined Radio Digital Radio 10 4 μp-controlled Analog Radio

28 Multi Standard Terminal Bluetooth GPS GSM, GPRS, EDGE, UMTS, HSPA, S3G, LTE UWB ZigBee WiMax NFC WLAN DVB-H 28

29 Multi Band, Multi Standard Approach Integration Use technology development (Moore s law) to miniaturize current solution Examples: - On-chip VCOs - Integration of passive components in RF ICs - WCDMA and GSM on general baseband IC Architecture Facilitate multi-band multi-standard Examples: - Use homodyne instead of heterodyne receivers - SDR - Modular and expandable software architecture The right architecture is key 29

30 Reuseable Radio Architecture Customer Applications Middleware Service Platform Network Access Service Data Communication Services MMI and Multimedia Services Application Platform Services Operation Services Hardware Abstraction Layer (HAL) Product specific Hardware General radio architecture All platforms use the same open and stable APIs Hardware depends on product configuration (WCDMA, EDGE, GPRS,... ) 30

31 Topics Historic Remarks Wireless Communications Software Defined Radio Software Communications Architecture Cognitive Radio Regulation 31

32 SCA: SDR Reconfigurability / Portability Thesameplatform can host multiple waveforms with the same platform services The same waveform can be implemented on multiple platforms with the same waveform software waveform 1 waveform 2 abstraction layer API waveform abstraction layer API platform platform 1 platform 2 reconfigurability portability 32

33 SCA: System Sructure CORBA Adapter Software API Security Boundary Black IDL Red CORBA API Software Non-CORBA Software (Legacy) Management Objects CORBA Adapter Source: M. Robert, J.H. Reed, J. Smith: The Joint Tactical Radio System (JTRS) Software Communcations Archtecture (SCA) Core Framework (CF): A Tutorial Non-CORBA Software (Legacy) Hardware API OS API API Hardware File System Configuration Files Trans. Security 33

34 SCA: General Features The SCA fixes standards in waveform implementations, i.e. SCA is a framework The SCA defines the SW for an SDR applicable within the Joint Tactical Radio System (JTRS) The underlying HW as well as the SW is described in object oriented terms Moreover, Structure Application Program Interfaces (APIs) and the Security Environment are described in the SCA All components of an SCA compliant radio must be documented in a generally accessible form SCA compliance is certified by an evaluation center 34

35 JTRS SCA from JPO SCA Specification, V2.2 35

37 Cognitve Radio: Definitions Joseph Mitola / Gerald Maguire, 1991 (IEEE Pers. Comm., vol. 6, no. 4, 1999): Radio etiquette is the set of RF bands, air interfaces, protocols, and spatial and temporal patterns that moderate the use of radio spectrum. Cognitive radio extends the software radio with radio-domain model-based reasoning about such etiquettes. Simon Haykin, 2005 (IEEE J. Select. Areas in Comm., vol. 23, no. 2, 2005): Cognitive radio is an intelligent wireless communication system that is aware of its surrounding environment (i.e. its outside world), and uses the methodology of understanding-by-building to learn from the environment and adapt its internal states to statistical variations in the incoming RF stimuli by making corresponding changes in certain operating parameters (e.g. transmit power, carrier-frequency and modulation strategy) in real-time, with two primary objectives in mind: - highly reliable communications whenever and wherever needed; - efficient utilization of the radio spectrum. Friedrich K. Jondral, 2005 (EURASIP J. on Wireless Comm. and Networking, 2005, no. 3): A cognitive radio (CR) is an SDR that additionally senses its environment, tracks changes, and reacts upon its findings. A CR is an autonomous unit in a communications environment that frequently exchanges information with the networks it is able to access as well as with other CRs. BNetzA, 2006: Cognitive radio is a radio or system that senses and is aware of its operational environment and can dynamically and autonomously adjust its radio operating parameters. Note: Cognitive radio may benefit from SDR implementation techniques. 37

38 Cognitive Radio: Tasks Evaluate the actual transmission request: Data rate, BER, delay,, own location, partner s location, time Choose the suitable transmission mode: Modulation, coding, MIMO, transmit power,, w.r.t. the hardware available, the interference temperature limit Look for a transmission resource: Spectrum holes Get in touch with the communications partner: Negotiate about the resource to be used, agree upon possible alternatives and upon the transmission mode for the reverse link, exchange channel state information (CSI) Choose the suitable receiver adjustment 38

39 Cognitive Characteristics Awareness (with respect to the transmitted waveform, RF spectrum, communication network, localization and geography, available services, user needs, language, situation, security policy, ) Intelligence Learning Adaptivity Reliability Efficiency 39

40 Mitola s Cognition Cycle A necessary condition for highest flexibility in mobile communications is a general rethinking in spectrum allocation: Open access In order to make open access feasible Cognitive Radios are necessary. Outside World Pre-Process Parse OBSERVE Receive a Message Read Buttons Infer on Context Hierarchie New States Prior States Send a Message Set Display ORIENT Establish Priority LEARN Immediate Urgent Normal ACT Save Global States Initiate Process(es) PLAN Register to Current Time DECIDE Allocate Resources Generate Alternatives Evaluate Alternatives Source: Joseph Mitola III: Cognitive Radio An Integrated Agent Architecture for Software Defined Radio. KTH Stockholm,

41 CR Properties Mitola's cognition cycle is very general. The properties of cognitive radios may be divided into two groups user centric properties (support functions like finding an appropriate restaurant, recommendation of a travel route, supervision of apointments,...) technology centric properties - spectrum monotoring - localization - awareness of processing capabilities (partitioning and scheduling of processes) - information and knowledge processing - time - 41

42 Technology Centric Cognitive Radio RF Signals Spectral Environment Transmission Spectral Environment RF Signals Monitoring Monitoring Reception Spectrum Holes Noise Statistics Traffic Volume Spectrum Holes Noise Statistics Traffic Volume Reception Channel measurement and modeling Interference Temperature Available Channel Capacity Station A Transmission Power and Spectrum Management Transmission Power and Spectrum Management Available Channel Capacity Interference Temperature Station B Channel measurement and modeling 42

44 Regulation Today spectrum is regulated by governmental agencies, e.g. the American Federal Communications Commission (FCC) or the Bundesnetzagentur (BNetzA) Spectrum is assigned to users or licensed to them on a long term basis normally for huge regions like whole countries This may lead to wasting of resources Vision: Resources are assigned where and as long as they are needed, spectrum access is organized by the network (i.e. by the end users) 44

45 Spectrum Utilization Measurements ( MHz) electric electric field field strength strength dbμv/m dbμv/m density density of of the the time time between between arrivals arrivals dbs dbs -1-1 Lichtenau (Germany), September

46 Self Regulation Wireless LANs (IEEE x) ISM band: MHz WLAN band: MHz and MHz Ultra Wide Band 40 UWB EIRP Emission Level in dbm Part 15 Limit fc greater than 3.1 GHz fc less than 960 MHz 10 0 Frequency in GHz

47 Advanced Spectrum Management Spectrum reallocation: The reallocation of bandwidth from government or other long-standing users to new services such as mobile communications, broadband internet access, and video distribution. Spectrum leases: The relaxation of the technical and commercial limitations on existing licensees to use their spectrum for new or hybrid (for example, satellite and terrestrial) services and granting most mobile radio licensees the right to lease their spectrum to third parties. Spectrum sharing: The allocation of an unprecedented amount of spectrum that could be used for unlicensed or shared services. Source: G. Staple, K. Werbach: The End of Spectrum Scarcity. IEEE Spectrum, March 2004, pp

48 Cognitive Radio: Spectral Efficiency *) CR technology is perfectly suited to opportunistically employ the wireless spectrum Flexible spectrum utilization is allowed by frequency agility dynamic frequency selection adaptive modulation transmit power control location awareness negotiated use CRs could skillfully navigate their way through interference and greatly improve spectral efficiency FCC and other regulators are altering their rules in order to allow for more flexible use of the licensed wireless spectrum *) from N. Devroye, P. Mitran, V. Tarokh: Limits on Communications in a Cognitive Radio Channel. IEEE Communications Magazine, June 2006, pp

49 Secondary Frequency Markets *) Spectrum leasing: Allowing unlicensed users to lease any part or all of the spectrum of a licensed user Dynamic spectrum leasing: Temporary and opportunistic usage of spectrum rather than a longer-term sublease Private commons: A licensee could allow unlicensed users access to his spectrum without a contract, optionally with an access fee Interruptible spectrum leasing: Suitable for a lesser that wants a high level of assurance that any spectrum temporarily in use, or leased, to an incumbent CR could be efficiently reclaimed if needed **) *) from N. Devroye, P. Mitran, V. Tarokh: Limits on Communications in a Cognitive Radio Channel. IEEE Communications Magazine, June 2006, pp **) e.g. T. A. Weiss, F.K. Jondral: Spectrum Pooling: An Innovative Strategy for the enhancement of Spectrum Efficiency. IEEE Communications Magazine, Radio Communications Supplement, March 2004, pp. S8-S14 49

50 Thank you! 50