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Cognitive Radio Networks Dr. Kwang‐Cheng Chen Di ti i h d P f d I i T H Ch iDistinguished Professor and Irving T. Ho Chair Graduate Institute of Communication Engineering & Department of Electrical Engineering National Taiwan University, Taipei, Taiwan ROC Email: chenkc@cc.ee.ntu.edu.tw April 1, 2009 1KC Chen, NTU EE & GICE OutlinesOutlines Air‐Interface Migration toward 4Gg SDR, Terminal Device Architecture, and SoC Cooperative Cognitive Radio to CognitiveCooperative Cognitive Radio to Cognitive Radio Network CRN Architecture and OperationCRN Architecture and Operation CRN Spectrum Sensing T i CRN A i i R iTrust in CRN, Association, Routing Cooperative Relay Networking Coding for CRN Cooperative Relay Routing and Applications April 1, 2009 2 g pp KC Chen, NTU EE & GICE Air‐Interface Technology Roadmap CDMA2000 IS‐95 CDMA2000 (3GPP2) EvDO UMB ? IMT Advanced IEEE 802.16e IEEE 802 16m 4G TDD ? IMT‐Advanced Mobile WiMAX IEEE 802.16m 4G TD SCDMA HSPA TDD GSM GPRS WCDMA HSPA (HSDPA/ 3G LTE TD‐SCDMA HSPA‐TDD GPRS EDGE (3GPP) (HSDPA/ HSUPS) 3G LTE NB/TDMA CDMA/FDD CDMA/TDDMuch more air‐interfaces on WLAN, WPAN, WBAN, …. April 1, 2009 3 / OFDMA Much more air interfaces on WLAN, WPAN, WBAN, …. KC Chen, NTU EE & GICE TruthTruth What is 4G? No one really knows. It comes around 2020 (IMT‐2020?) or 2025 What did 3G not accomplish? • Wireless packet switching • Wireless Internet (NOT ireless access to Internet)• Wireless Internet (NOT wireless access to Internet) • Internet backbone for wireless What are new services, applications, scenarios?, pp , What are new technologies? By 2020, there will be trillions wireless devices.y , Challenge for spectrum efficiency Challenge for network architecture April 1, 2009 4KC Chen, NTU EE & GICE Consumer Networks High Definition Flat-Panel TV Digital Camera MP3 Consumer Networks SpeakerSpeaker WiMAX PDA or Wireless Game Console HandsetWireless Gateway VoIP Speaker S k Game Console or Home Router PCPublic Networks Speakeror Internet IEEE ComSoc: Consumer Networks would be April 1, 2009 5 KC Chen, NTU EE the driving force for future communication technology. KC Chen, NTU EE & GICE Personal NetworksPersonal Networks Not just personal area networks (PAN), it is networking toward ( ) d i d i ievery (consumer) device around a person in every environment, including cellular, WMAN, WLAN, WPAN, WBAN. From Aalborg University April 1, 2009 6KC Chen, NTU EE & GICE Fundamental Factors in Future Wireless Communications MIMO to Yield Gigabit Wireless A t & RF/ i d d t h l t f tili MIMO Antenna & RF/mixed mode technology to fertilize MIMO Terminal device architecture with small form factor Spectrum Utilization in Unlicensed and even Licensed Bandsp Cognitive Radios • SDR and new DSP technology • Re configurable MAC• Re‐configurable MAC • Power management Cooperative Communications • Radio resource management, mobility management Network Efficiency Multiple access QoS Routing mobile IP Multiple access, QoS, Routing, mobile IP Cognitive Radio Networks Network throughput per bandwidth! April 1, 2009 7KC Chen, NTU EE & GICE PHY Technology Toward Spectrum Efficiency Frequency Reuse High‐dimensional modulation with FEC Adaptive modulation & coding (AMC) to reach icapacity Multiple‐input‐multiple‐output (MIMO) T i di i d i di iTransmit diversity and receive diversity Realization of MIMO B f iBeamforming Spatial multiplexing (SM) Space time codes (STC)Space‐time codes (STC) Mobile WiMAX as an example of wireless packet switching cellular system April 1, 2009 8 88 switching cellular system KC Chen, NTU EE & GICE OutlinesOutlines Air‐Interface Migration toward 4Gg SDR, Terminal Device Architecture, and SoC Cooperative Cognitive Radio to Cognitive Radio Cooperative Cognitive Radio to Cognitive Radio Network CRN Architecture and Operationp CRN Spectrum Sensing Trust in CRN Association Routing Trust in CRN, Association, Routing Cooperative Relay Networking Coding for CRN Cooperative RelayNetworking Coding for CRN Cooperative Relay CRN Mobility and International Standards April 1, 2009 9KC Chen, NTU EE & GICE Software Defined Radio (SDR)Software Defined Radio (SDR) Cognitive Radio (CR) is considered as an intelligent version of SDR, but we are g going to tell “more than that”! Form and lead a research team of 4 top national universities for B3G Lead students to develop one of early high‐speed OFDM modem using TI DSP (First place of 2000 TI Analog and Digital SDR prototype developed in 2001, allowing hi h b d idth hi h h i t FH d DS Challenge in Asia Pacific Region) high‐bandwidth high hopping‐rate FH and DS with TI‐DSP as processing core April 1, 2009 KC Chen, NTU EE & GICE 10 SDR Hardware Architecture Antenna ROM Controller Antenna (Array) ROM System & Frequency S l tiController & Digital Signal RF & IF A/D D/A Selection g Processor / External Control & RAM Micro‐ Processor BUS Multimedia I/O April 1, 2009 11 BUS I/O KC Chen, NTU EE & GICE SDR Software Architecture Applications: Real‐Time DSP Algorithms: SDR Software Architecture Applications: OS Protocol Stack: MAC DSP Algorithms: Mod/Demod User‐Interface Multimedia / MAC Link Radio Resource / Codec SynchronizationRF & IF Appl. S/W Radio Resource Logic Channel Network Mgt. RAKE Rx. Equalization MIMO Processing & IF QoS Security MIMO Processing Channel Est.A/D D/A DSP & HW Micro‐ Controller Micro‐ Processor April 1, 2009 12KC Chen, NTU EE & GICE Current Mobile Terminal HWCurrent Mobile Terminal HW IrDA Power/Battery Management Bluetooth WLAN WiMAXSIM Baseband Processor Multimedia Co‐Processor WiMAX UWB FM SIM DVB/DAB‐T DVB‐H RF PA Memory DSC SD/MS MP3 A MP3 MPEG, H.264 LCD DriverMore effective mechanism f l i l i i April 1, 2009 13 Antenna LCD Controller for multiple co‐existing systems is needed. KC Chen, NTU EE & GICE Challenges to Wireless Communication SoCChallenges to Wireless Communication SoC Entire Memory PLL Entire Module Memory Memory MCU Power Mgt & Analog Digital Signal Processor(s) RF Digital Logic Digital portion follows Moorse’s law but analog portion not! April 1, 2009 14 Digital portion follows Moorse s law but analog portion not! KC Chen, NTU EE & GICE Digital Radio ProcessingDigital Radio Processing RF AD DA Baseband Inner & Outer RF AD DA Baseband Inner Receiver SimpleSimple RF Functions Requiring new algorithms and new processing, with effective ADC, while TI 1st generation using Pentium processor It is revolution from communication system, and likely useful for cognitive radio realization April 1, 2009 15 for cognitive radio realization KC Chen, NTU EE & GICE Processor TechnologyProcessor Technology Von Newmann machine (general purpose)(g p p ) ALU Memory Single bus for data and program Improvements such as RISC, multiple ALUs, cache memory and multiple corememory, and multiple‐core Digital Signal Processor (special purpose) Multiple ALUsMultiple ALUs Data bus and program bus MemoryMemory How about future communication processor and network processor April 1, 2009 16 network processor KC Chen, NTU EE & GICE OutlinesOutlines Air‐Interface Migration toward 4Gg SDR, Terminal Device Architecture, and SoC Cooperative Cognitive Radio to CognitiveCooperative Cognitive Radio toCognitive Radio Network CRN Architecture and OperationCRN Architecture and Operation CRN Spectrum Sensing T i CRN A i i R iTrust in CRN, Association, Routing Cooperative Relay Networking Coding for CRN Cooperative Relay Routing and Applications April 1, 2009 17 g pp KC Chen, NTU EE & GICE Cognitive CommunicationsCognitive Communications Cognitive Radio J Mit l III t id i i i ll i d t J. Mitola III to provide pioneer vision allowing secondary users to utilize spectrum when it is not used by primary systems, even in licensed bands FCC d li i f ffi i FCC to endorse applications for spectrum efficiency • Less than 10% of licensed spectrum being used by time average • Various measurements support the same conclusion Upon to this scenario, cognitive radio is primarily a link‐level technology for dynamic access of radio spectrum for physical layer radio transmission. However, after dynamic spectrum access at link‐level, how to transport the packets successfully through? Cognitive radios (CR) should provide networking macro‐scale Cognitive radios (CR) should provide networking macro‐scale diversity, as Cognitive Radio Networks (CRN) consisting of PS and CRs. April 1, 2009 18KC Chen, NTU EE & GICE Well Known Dynamic Spectrum AccessWell‐Known Dynamic Spectrum Access Spectrum sensing: Cognitive radio discovers spectrum hole by spectrum sensing D namic Spectr m Access Dynamic Spectrum Access: Cognitive radio communicate with other Cognitive radio terminals to access spectrum holes dynamically April 1, 2009 19 What after successful CR transmission? KC Chen, NTU EE & GICE Cognitive Radio as Link Level TechnologyCognitive Radio as Link Level Technology CR senses the spectrum of primary system (PS) being “ il bl ” h i k h i i d“available”, then transmits packets to the receiving node. Foundation of Cognitive Radio technology CR is thus a link level technology requiring CR is thus a link level technology requiring Reliable sensing information for spectrum utilization Dynamic spectrum accessDynamic spectrum access Possible programmable (or software) radio to support • Appropriate frequency band operating • Appropriate communication parameters and protocol Existing examples: • In IEEE 802 11h at 5G Hz band 11a signal to avoid primary radar signalsIn IEEE 802.11h at 5G Hz band, 11a signal to avoid primary radar signals • In IEEE 802.15.2 and Bluetooth 2.0, adaptive frequency hopping Bluetooth to avoid other co‐existing systems with higher power • DAA (detection and avoidance) for UWB April 1, 2009 20 • DAA (detection and avoidance) for UWB KC Chen, NTU EE & GICE Spectrum SensingSpectrum Sensing The goal of CR spectrum sensing is to identifyThe goal of CR spectrum sensing is to identify “available opportunity” to transmit. Fundamental: Energy detectionFundamental: Energy detection • RSSI from RF Reliable: Feature extractionReliable: Feature extraction • Carrier frequency • Symbol rateSymbol rate • Other spectral correlation methods Cooperative sensingCooperative sensing Distributed sensing April 1, 2009 21KC Chen, NTU EE & GICE Beyond Link‐Level CRBeyond Link Level CR However, using the concept of CR, what after , g p , the dynamic (or opportunity) spectrum access? There must exist a networking mechanism to g transport the packets from source node, via cognitive radio transmission, to destination node. C iti di t k (CRN) i t j t f dCognitive radio network (CRN) is not just formed by CRs. CRN consists of CRs PS cooperative relay networkCRN consists of CRs, PS, cooperative relay network codes. Using OSI structure, CRN shall have functions fromUsing OSI structure, CRN shall have functions from data link layer, network layer, and more, in addition to physical layer. April 1, 2009 22KC Chen, NTU EE & GICE Cognitive Radio Networks (CRN)Cognitive Radio Networks (CRN) Cognitive radio is not just a new generation of software radio, to sense spectrum. Cognitive radio shall sense the communication and networking environments.g Integration of cognitive radios and existing infrastructure (PS) to optimize communications and networks To optimize networking efficiency per unit bandwidthp g y p Future terminal devices shall be cognitive and determine the most appropriate way of communications, that is, to form cognitive radio networkscognitive radio networks. It does not make a lot of sense to distinguish infrastructure or ad hoc for such multi‐hop peer‐to‐peer communications in applications and servicesservices It is wireless/wired heterogeneous networking, with hybrid of primary radio networks and cognitive radio networks It creates a lot of challenges April 1, 2009 23 KC Chen, NTU EE It creates a lot of challenges KC Chen, NTU EE & GICE Technology Challenges to CRNTechnology Challenges to CRN CR links are dynamically available and likely uni‐directional, in the multiple‐system co‐existing environments Routing • (Inter‐system) Handover(Inter‐system) Handover • (Joint) Radio Resource Management • Scheduling and QoS A i ti d S it Association and Security • Security for cooperative networking (traditional approaches might not be feasible) T t d h i• Trusted mechanism Link‐level • Cognitive/Cooperative MAC, Dynamic Spectrum Access • Error control techniques such as HARQ Service Architecture, Business Models, and Regulations April 1, 2009 24KC Chen, NTU EE & GICE CRN via Cooperative Networkingp g Cooperative Relay AP AP /BS Cooperative Relay AP /BS Internet /BS Opportunistic Transmission Wireless Device Transmission Route #2‐b Opportunistic Transmission Route #1 Device Opportunistic Transmission R t #2 Destination Node Cooperative Node To relay packet(s) Route #2‐a Packet Transportation April 1, 2009 25 CR Source Node Transportation KC Chen, NTU EE & GICE Cooperative Communications and NetworksCooperative Communications and Networks Origin from diversityg y Microscopic: MIMO is a kind of antenna cooperation Macroscopic: cooperation among (network) nodes to have better i l isignal reception Nodes can cooperate to relay packets (routing) • Amplify‐and‐forward (AF)p y ( ) • Decode‐and‐forward (DF) • Compress‐and‐forward (CF) Source Destination Intermediate Helping Node April 1, 2009 26 Intermediate Helping Node KC Chen, NTU EE & GICE Cognitive radio is NOT just a linkCognitive radio is NOT just a link level technology!gy Cognitive radio “networks” shall beCognitive radio networks shall be the final goal in future wireless communicationscommunications. April 1, 2009 27KC Chen, NTU EE & GICE OutlinesOutlines Air‐Interface Migration toward 4Gg SDR, Terminal Device Architecture, and SoC Cooperative Cognitive Radio to CognitiveCooperative Cognitive Radio to Cognitive Radio Network CRN Architecture and OperationCRN Architecture and Operation CRN Spectrum Sensing T i CRN A i i R iTrust in CRN, Association, Routing Cooperative Relay Networking Coding for CRN Cooperative Relay Routing and Applications April 1, 2009 28 g pp KC Chen, NTU EE & GICE Ubiquitous Cognitive Radio Heterogeneous Networks [Chen et al. ACM ICUMIC 2008] Ad Hoc Network Mesh Network Infrastructure CRN is in general an heterogeneous ad hoc network April 1, 2009 29 ad hoc network KC Chen, NTU EE & GICE Elements of Cognitive Radio NetworksElements of Cognitive Radio Networks Primary System(s)y y ( ) Licensed band Unlicensed band (multiple‐systems co‐existing)Unlicensed band (multiple systems co existing) Cognitive Radio(s) Dynamic access while primarysystem is idleDynamic access while primary system is idle Cognitive Radio Networks Th CR f i t kThose CRs forming a network CRN terminals can leverage multiple co‐existing systems/networks to form a more general CRNsystems/networks to form a more general CRN • Inter‐system/network operation • Topology can be either infrastructured, ad hoc, or mesh April 1, 2009 30 KC Chen, NTU EE Topology can be either infrastructured, ad hoc, or mesh KC Chen, NTU EE & GICE Cognitive Radio CapabilitiesCognitive Radio Capabilities Sense the communication environments spectrum holes geographic location geographic location available wire/wireless communication systems/networks available services Analyze and learn information from the environments with user’s f d d dpreferences and demands Reconfigure itself by adjusting system parameters conforming to certain Reconfigure itself by adjusting system parameters conforming to certain policies and regulations. April 1, 2009 31KC Chen, NTU EE & GICE Terminal Capability Of Cognitive Radio NetworksTerminal Capability Of Cognitive Radio Networks Cognitive Capability Self‐Organized Capability Spectrum sensing Spectrum sharing Location identification Spectrum/Radio resource management Mobility/Connection Location identification Network/Service discovery y/ management Trust/Security management Reconfigurable Capability Adaptive modulation/coding Transmit power controlTransmit power control Dynamic system/network access April 1, 2009 32KC Chen, NTU EE & GICE Network ArchitectureNetwork Architecture I l CRN i d h t k ith In general, CRN is an ad hoc network with various kinds of network entities, which is different from the legacy ad hoc networkdifferent from the legacy ad hoc network. In such an heterogeneous ad hoc network, we can further divide network entities intocan further divide network entities into different groups by their network architecturesarchitectures. Infrastructure Ad HocAd Hoc Mesh April 1, 2009 33KC Chen, NTU EE & GICE Network Architecture InfrastructureNetwork Architecture – Infrastructure / l ll l d BS/AP control all accesses in a centralized manner MS can only access a BS/AP in an one‐hop manner. MSs under the transmission range of the same BS/AP shall communicate with g / each other through the BS/AP. Communications between different cells are routed through backbone/core networks. April 1, 2009 34KC Chen, NTU EE & GICE Network Architecture Ad HocNetwork Architecture – Ad Hoc b bl h d h f Communications between MSs are established without infrastructure supports Links may be established via different wireless communication y technologies. Legacy communication technologies/protocols i Dynamic spectrum access April 1, 2009 35KC Chen, NTU EE & GICE Network Architecture MeshNetwork Architecture – Mesh / k l d f l b kb BSs/APs work as wireless routers and form wireless backbones MSs can either access the BSs/APs directly or use other MSs as multi‐hop relay nodesy April 1, 2009 36KC Chen, NTU EE & GICE Primary SystemPrimary System A primary system is referred to an existing wireless communication system which operates in one or many fixed frequency bands with a certain level of priorityfrequency bands with a certain level of priority. Primary System in Licensed Bands Primary System in Licensed Bands Which has the highest priority to access frequency bands Primary System in Unlicensed Bands Primary System in Unlicensed Bands Systems coexist with each other April 1, 2009 37KC Chen, NTU EE & GICE Cognitive Radio SystemCognitive Radio System A cognitive radio system neither has a fixed operating frequency band nor has privilege to access that band. D i ll t h l t i tDynamically use spectrum holes to communicate C i i R di B S i (CR BS) Cognitive Radio Base Station (CR‐BS) Gateway between wired and wireless networks d k f ( dProvide network management functions (e.g. radio resource management, mobility management, security management) Cognitive Radio Mobile Station (CR‐MS) April 1, 2009 38KC Chen, NTU EE & GICE Links in CRNLinks in CRN • CRN consists of eight kinds of likely uni‐directional and g y dynamic links, which demonstrates a unique feature in such dynamic networking. • Each of the three network architectures may be composed of one or several kinds of links 1. CR‐MSCR‐MS 2. CR‐MSCR‐BS 3 CR‐MSPR‐BS3. CR‐MSPR‐BS 4. CR‐BSCR‐BS 5. PR‐MS and PR‐BS 6. PR‐MSCR‐MS 7. PR‐MSCR‐BS April 1, 2009 39 8. PR‐MSPR‐MS KC Chen, NTU EE & GICE CRN OperationCRN Operation The networking operation of a node in CRN CRN S t S i CRN Spectrum Sensing • Not just to detect “available spectrum”, but also to detect “available systems” under programmable capability E d i CR f ( i ) d i PS• Every node is a CR, even for (cooperative) nodes in PS Association • CR is ready to transmit packets and must start association of CRN (without knowing network topology) • Relay node to determine “whether to accept cooperative relay request” from certain node, based on trust level (likely not possible to complete se rit he k)security check) • That is, admission control of CRN Dynamic Spectrum Access • Multiple access and transmission Routing • Cooperative relay system/network/CRs to determine routing April 1, 2009 40 p y y / / g KC Chen, NTU EE & GICE Cognitive Radio Network Terminal Architecture Applications & Services Cognitive Radio Network Terminal Architecture Radio Resource Allocation Bandwidth/Channel Allocation Handoff/Roaming Network f bl / g Routing, QoS, Security Cooperative Communications Coordinator f S lfRe‐configurable MAC & Networking Protocol of Self‐ Organized Communication & Networking Data Link & MAC Cognitive Radio Software Defined Radio ADC DAC & Networking PHY RF 1 RF N ……. April 1, 2009 41 KC Chen, NTU EE RF‐1 RF‐N.. KC Chen, NTU EE & GICE Cognitive CycleCognitive Cycle Radio/Wireless Medium RF Analysis BB‐PHY AnalysisAnalysis Channel State & RF S /U Rate‐Distance Self‐Organized C di & AD/DA & Filtering RF System/User Analysis Coordinator & Spectrum Utilization De isionRe‐configurable SDR g Network A l i Decision Radio Resource e co gu ab e MAC April 1, 2009 42 Analysis Packets/Traffic KC Chen, NTU EE & GICE Economy of Cognitive RadioEconomy of Cognitive Radio Practical realization of cognitive radio technology Practical realization of cognitive radio technology lies in balanced interests among 4 parties [H.B. Chang K C Chen N Prasad CW Su IEEE VTCChang, K.C. Chen, N. Prasad, C.W. Su, IEEE VTC 2009] I ti t i d t ff i f Incentives to primary users, due to suffering from Overall spectrum utilization Interests of service provider(s) Spectrum access opportunity to cognitive radio users We implement spectrum auction algorithm to ensure win‐win situation among above 4 partiesensure win win situation among above 4 parties April 1, 2009 KC Chen, NTU EE & GICE 43 Spectrum Management PolicySpectrum Management Policy Vickrey AuctionVickrey Auction (multi‐unit sealed‐bid) is adopted, which is faster than English (sequential)auction April 1, 2009 KC Chen, NTU EE & GICE 44 OutlinesOutlines Air‐Interface Migration toward 4Gg SDR, Terminal Device Architecture, and SoC Cooperative Cognitive Radio to Cognitive Radio Cooperative Cognitive Radio to Cognitive Radio Network CRN Architecture and Operationp CRN Spectrum Sensing Trust in CRN Association Routing Trust in CRN,Association, Routing Cooperative Relay Networking Coding for CRN Cooperative RelayNetworking Coding for CRN Cooperative Relay CRN Mobility and International Standards April 1, 2009 45KC Chen, NTU EE & GICE Spectrum SensingSpectrum Sensing Th l f CR t i i t id tif The goal of CR spectrum sensing is to identify “available opportunity” to transmit. Fundamental: Energy detectionFundamental: Energy detection • RSSI from RF Reliable: Feature extraction C i f• Carrier frequency • Symbol rate • Other spectral correlation methods Cooperative sensing Distributed sensing M f t i i CRN More for spectrum sensing in CRN To identify co‐existing systems possibly to cooperate in different frequency bands (unlicensed and even licensed) April 1, 2009 46 q y ( ) KC Chen, NTU EE & GICE Spectrum Sensing for CRN RF AD BB‐DSP MAC & Network Features Spectrum Sensing for CRN [Chen et al. WPMC 2007] Frequency Bandwidth RSSI Symbol Rate Carrier & Timing Pil t Si l Multiple Access Protocol Radio Resource Allocation ARQ & Traffic Pattern /RSSI SINR Estimation Pilot Signal Channel Fading System/User Identification Routing/Mobility Information System/User Identification Modulation Parameters FEC Type & Rate MIMO Parameters Sensing/Cognition of Cognitive Radio Channel State & Rate‐DistanceMIMO Parameters Power Control of Cognitive Radio Network Terminal Assisted Information for MUD Self‐Organized Coordinator Decision of Spectrum Optimization & Utilization Packets April 1, 2009 47 4747KC Chen, NTU EE 47 RF AD/DA & Filtering BB‐SDR Re‐configurable MAC Network Functions KC Chen, NTU EE & GICE Spectrum Sensing in Multiple Co‐existing Systems [Yu and Chen, IEEE VTC 2008] Allow adaptation to different possible systems (PS and/or CR) for cooperative relayand/or CR) for cooperative relay Based on feature extraction F d t l f ( b l/b d t )Fundamental frequency (symbol/baud rate) Power spectrum density pattern 4th order cumulant4th order cumulant Suqarer BPF ADC Fundamental Frequency ADC SpectrumEstimation SVD detection Trispectrum EVD MUSIC April 1, 2009 48 Estimation EVD MUSIC KC Chen, NTU EE & GICE Example to operate at 2 4G Hz ISM BandExample to operate at 2.4G Hz ISM Band Spectrum magnitude after squarer with SNR=10 dB Estimation of power spectrum density with Microwave ovensquarer with SNR=10 dB and roll‐off factor=0.5 density with Microwave oven and 802.11g (carrier frequency=2437 MHz) April 1, 2009 49 (carrier frequency 2437 MHz) KC Chen, NTU EE & GICE Flow chart of general multiple systems sensing algorithm at 2.4GHz ISM band Spectral line(s) observation )(2cos1 )()}({)( 22 22 TtZ ttrEtr P ii )(11 )(2cos 2 20, 22 1 1, t Z TtZ T P iii i iii i )( 22 1 t T wi i MUSIC Pseudospectrum M i H music iiR )( pp M Qm m H i 1 2|| qp April 1, 2009 50KC Chen, NTU EE & GICE Hidden Terminal ProblemHidden Terminal Problem CR’s carrier sensing may still be under jeopardyg y j p y due to hidden terminal problem! CR‐Rx PS‐Rx Blocking CR‐Tx Interference From CR to PS PS‐Tx PS‐Rx CR Tx Range From CR to PS CR‐Tx Range April 1, 2009 51 PS‐Tx Range KC Chen, NTU EE & GICE Distributed or Cooperative SensingDistributed or Cooperative Sensing DistributedDistributed Sensing CR‐Rx PS‐Rx Blocking CR‐Tx Cooperative Sensing PS‐Tx PS‐Rx CR Tx Range Cooperative Sensing PS‐Tx Range CR‐Tx Range April 1, 2009 52KC Chen, NTU EE & GICE CRN TomographyCRN Tomography Spectrum sensing for spectrum hole targets at link‐p g p g level CR, but CRN requires information beyond. Only passive detection? CRN needs information about radio resource, rather than spectrum holes CRN h i f i i ll i d CRN tomography is a sort of statistically measuring and inferring techniques that provide the CRN parameters and traffic patterns without special‐purposeand traffic patterns without special‐purpose cooperation of the radios belonging to heterogeneous systems.y [Yu and Chen, IEEE VTC‐Spring 2009] Inferring not just detection/estimation April 1, 2009 KC Chen, NTU EE & GICE 53 Radio Resource TomographyRadio Resource Tomography Radio Resource Tomography Algorithm: Assuming cooperative AMC, 1 Set initial probing power from1. Set initial probing power from minimum value 2. Determine AMC of PS 3 Transmit probing signal3. Transmit probing signal 4. Adjust probing power based on AMC of PS 5. Calculate max. allowable CR With above channel model, the purpose of spectrum sensing is 5. Calculate max. allowable CR transmission power from SINR actually to identify the maximum transmission power of cognitive radio, subject to regulation and SINR. April 1, 2009 KC Chen, NTU EE & GICE 54 radio, subject to regulation and SINR. OutlinesOutlines Air‐Interface Migration toward 4Gg SDR, Terminal Device Architecture, and SoC Cooperative Cognitive Radio to Cognitive Radio Cooperative Cognitive Radio to Cognitive Radio Network CRN Architecture and Operationp CRN Spectrum Sensing Trust in CRN Association Routing Trust in CRN, Association, Routing Cooperative Relay Networking Coding for CRN Cooperative RelayNetworking Coding for CRN Cooperative Relay CRN Mobility and International Standards April 1, 2009 55KC Chen, NTU EE & GICE Trust in CRNTrust in CRN Trust forms the foundation of CRN Ensuring smooth operation of CRN to support ubiquitous computing with dynamic topology In many cases (such as association and routing/relaying packets), it is not practical nor possible nor desirable to proceed security functions. By the concept of cooperative networking • If trusted, amplify‐and‐forward • If secured, AF and possible compress‐and‐forward Examples of applications Examples of applications “Trust” from originally existing system (i.e. primary system) and regulator Leverage another existing cognitive radio to route its packets Leverage PS to forward its packets April 1, 2009 56KC Chen, NTU EE & GICE Related Work on TrustRelated Work on Trust T d i Trusted computing deals with components inside a set or a territory / b i Internet/web computing treats trust as a kind of reputation/credits given b h i ( h th ’ i )by a mechanism (such as other’s scoring) Ad hoc network Artificial intelligence Artificial intelligence Social science It still needs a mathematical framework. [please see K.C. Chen, et al. ACM ICUMIC 2008] April 1, 2009 57 ] KC Chen, NTU EE & GICE Trusted AssociationTrusted Association There are only two possible decisions for y p association in CRN based on trust measure, that is, to accept association and to reject association When a node in CRN (primary system or secondary systems) receives a request of association from a new node (i.e. to join this CRN) i f i i l d i iCRN), it forms a statistical decision as Based on the trust measure associated with this node decision can be formed while 10)( i anode, decision can be formed, while means “accept” the association and means “reject” the association. 1,0,)( iai 1a 0a April 1, 2009 58 j KC Chen, NTU EE & GICE Decision on Trusted AssociationDecision on Trusted Association DefineDefine When a priori information of trust is unknown and the cost function cannot be well defined,and the cost function cannot be well defined, the decisioncan be based on the Neymann‐ Pearson criterion That is givenPearson criterion. That is, given optimize April 1, 2009 59KC Chen, NTU EE & GICE Measurement of ReasoningMeasurement of Reasoning Cox AxiomsCox Axioms Degree of certainty can be ordered There exists a function to map certainty of aThere exists a function to map certainty of a statement to its negation/complement Degree of reasoning R(AB) is related to the g g ( ) conditional reasoning R(A|B) and R(B) by some function g • R(AB) = g(R(A|B),R(B)) Any reasoning system consistent with Cox Axioms b i l b bili hmust be equivalent to probability theory. Trust model in CRN indeed applies. April 1, 2009 60KC Chen, NTU EE & GICE Update of Trust by Machine LearningUpdate of Trust by Machine Learning A station in CRN (either PS or CRs) shall keep update the table f t t f i hb i t ti hi h iof trust for neighboring stations, which requires some learning process. [Chen et al. Wiley Wireless Comm & Mobile Computing, 2009] Suppose denotes the state transition probability under new observation at time n; denotes the measurement probability. The Bayes Filter p y y Algorithm consists of the following equations: where is the normalization constant. The first equationwhere is the normalization constant. The first equation represents the update rule, which provides the prediction, and second equation is actually the measurement update. April 1, 2009 61KC Chen, NTU EE & GICE OutlinesOutlines Air‐Interface Migration toward 4Gg SDR, Terminal Device Architecture, and SoC Cooperative Cognitive Radio to CognitiveCooperative Cognitive Radio to Cognitive Radio Network CRN Architecture and OperationCRN Architecture and Operation CRN Spectrum Sensing T i CRN A i i R iTrust in CRN, Association, Routing Cooperative Relay Networking Coding for CRN Cooperative Relay Routing and Applications April 1, 2009 62 g pp KC Chen, NTU EE & GICE Origin of Cooperative RelayOrigin of Cooperative Relay From MIMO, cooperative diversity to exploit spatial diversity among distributed singlespatial diversity among distributed single‐ antenna terminals, under fading channels [Laneman and Wornell IEEE T‐IT 2003][Laneman and Wornell, IEEE T IT, 2003] • distributed STBC and all‐selected strategy [Laneman, Tse, Wornell, IEEE T‐IT, 2004] • Useless if the number of relays >> columns of STBC • MRC is optimal for AF to achieve full diversity order of 1+K (number of relays)(number of relays) • Relay selection has higher bandwidth efficiency than repetition based strategy [S d i E ki A h IEEE T C 2003][Sendonairs, Erkip, Aazhang, IEEE T‐Com, 2003] • Optimal ML detector for DF • Uplink capacity increases April 1, 2009 63 p p y KC Chen, NTU EE & GICE Cooperative CommunicationCooperative Communication Nodes with single‐antenna can form virtualNodes with single antenna can form virtual multiple antenna communications ( l l l(More precisely, multiple access channel but relay channel can not be precisely calculated) April 1, 2009 64 be precisely calculated) KC Chen, NTU EE & GICE Relay StrategyRelay Strategy Typical 2‐stage relaying strategyTypical 2 stage relaying strategy A source transmits and all other nodes listen These cooperating nodes re‐transmit or relay theThese cooperating nodes re‐transmit or relay the source message to the destination, with appropriate relay strategy (i.e. relay selection)appropriate relay strategy (i.e. relay selection) X + hs,1 ns,1 Relay 1 X + hs,i ns,i Relay i y h Relay Selection X + hr,d nr,d X + hs,K ns,K Relay K (“best”) Source Destination April 1, 2009 65 X + h0 n0 Source KC Chen, NTU EE & GICE Relay Selection (I)Relay Selection (I) To apply distributed STC, channel state information (CSI) are il bl f ll ibl li kavailable for all possible links. Opportunistic relay Selects the “best” relay node among relay candidates to support Selects the best relay node among relay candidates to support tradeoff between multiplexing and diversity, similar to (antenna) MIMO [Bletaes Khisti Reed Lippman IEEE JSAC 2006] [Bletaes, Khisti, Reed, Lippman, IEEE JSAC 2006] DF or AF operates based on two possible policies to select “best” node (thus path), with possible “collisions” 2,2, ||,||min:1Policy diisih 2 , 2 , ||||2P li diish 2 , 2 , ,, |||| :2Policy diis diis ih iis noderelay and sourcebetween amplitude fading :, April 1, 2009 66 , ndestinatio and noderelay between amplitude fading :, idi KC Chen, NTU EE & GICE Relay Selection (II)Relay Selection (II) Multiple sources and destinations [Whittneben Rankov IEEE VTC 2004] [Whittneben, Rankov, IEEE VTC 2004] [Whittneben, Hammerstroem, IEEE WCNC 2005] • Multiple AF relays • Multiuser interference is cancelled by orthogonalization of channels among source‐destination pairs CDMA and OFDM signalingCDMA and OFDM signaling Memoryless relay networks [Gamadam, Jafar, IEEE JSAC 2007][ , , ] AF is near‐optimal at low transmit power in a parallel network DF is near‐optimal at high transmit power in a serial network Research Challenges High SNR: tradeoff between diversity and multiplexing L SNR f April 1, 2009 67 Low SNR: outage performance KC Chen, NTU EE & GICE Extension to Wireless NetworksExtension to Wireless Networks Multinode Cooperation p [Sadek, Su, Liu, IEEE T‐SP 2007] the asymptotic performance of a simple cooperative scenario in which h l b h l f h d heach relay combines the signals from the source and the previous relay is exactly the same as that for a much more complicated scenario in which each relay combines the signals from the source and all the previous relays full diversity equal to the number of cooperating nodes is indeed achievableachievable Mobility of source affects the performance much more than the mobility of destination, for both amplify and forward (AF) y , p y ( ) and demodulate and forward (DF) relays [Gomadam, Jafar, IEEE WCNC 2005] April 1, 2009 68KC Chen, NTU EE & GICE Cooperative and Opportunistic SchedulingCooperative and Opportunistic Scheduling Rate adaptation and energy efficiency Basic Procedure [Zhang, et al. IEEE Network, 2007] Channel probing Credit calculations Data transmission Flow scheduling and optimal scheduling depends on N b f i hb i t itt• Number of neighboring transmitters • Coherence time of fading channel • QoS requirements Throughput optimal control of cooperative relay networks Throughput optimal control of cooperative relay networks Maximum differential backlog algorithm taking into accounts the cooperative gains, to jointly optimize routing, scheduling, and radio resource allocation [Yeh and Berry, IEEE T‐IT, 2007] Opportunistic Routing Cooperative and Cognitive MAC April 1, 2009 69 Coope at e a d Cog t e C KC Chen, NTU EE & GICE OutlinesOutlines Air‐Interface Migration toward 4Gg SDR, Terminal Device Architecture, and SoC Cooperative Cognitive Radio to Cognitive Radio Cooperative Cognitive Radio to Cognitive Radio Network CRN Architecture and Operationp CRN Spectrum Sensing Trust in CRN Association Routing Trust in CRN, Association, Routing Cooperative Relay Networking Coding for CRN Cooperative RelayNetworking Coding for CRN Cooperative Relay CRN Mobility and International Standards April 1, 2009 70KC Chen, NTU EE & GICE Cognitive Radio Relay Network (CRRN)Cognitive Radio Relay Network (CRRN) As cooperative relay is the fundamental operation of CRN, CRRN shall be explored. Wemay use network coding to explore the fundamental properties of (cooperative) relay network for CRs, while most existing research April 1, 2009 71 in physical layer rather than networking level KC Chen, NTU EE & GICE Network Coding for Cognitive Cooperative Relay O h R l Network: Tandem Replay One‐hop Relay Interference to PS from CR is unavoidable and unbounded. Tandem Relay The network capacity of such network is constrained by the smallest link capacity among all links. H CR t t th t k d t it April 1, 2009 72 Hence CR can connect to the network and transmit through those links other than the smallest capacity. KC Chen, NTU EE & GICE Network Coding for Cognitive Cooperative Relay Network: Cooperative Relay Network capacity of PS v = min (a+b, b+c) April 1, 2009 73KC Chen, NTU EE & GICE Network Coding for Cognitive Cooperative Relay Network: Parallel Cooperative Relay April 1, 2009 74KC Chen, NTU EE & GICE Network Coding for Cognitive Cooperative Relay Network Using network coding to explore cognitive cooperative relay network via basic structures (i.e tandem, cooperative relay, parallel cooperative relay) CR’s maximum network capacity in CRRN under the constraint CR s maximum network capacity in CRRN under the constraint of avoiding interference to PS Link capacity allocation to achieve maximum network capacity capac ty a ocat o to ac e e a u et o capac ty can be formulated as a multi‐commodity flow problem to be solved by linear programming l d l l f d Simulations over randomly generating topologies for PS and CRs show 92% of chances that CRRN can enhance overall network capacity (PS92% of chances that CRRN can enhance overall network capacity (PS and CRN) Increasing 1.3 times of capacity in average [Huang Lai Chen PHYCOM 2008] April 1, 2009 75 [Huang, Lai, Chen, PHYCOM, 2008] KC Chen, NTU EE & GICE OutlinesOutlines Air‐Interface Migration toward 4Gg SDR, Terminal Device Architecture, and SoC Cooperative Cognitive Radio to CognitiveCooperative Cognitive Radio to Cognitive Radio Network CRN Architecture and OperationCRN Architecture and Operation CRN Spectrum Sensing T i CRN A i i R iTrust in CRN, Association, Routing Cooperative Relay Networking Coding for CRN Cooperative Relay Routing and Applications April 1, 2009 76 g pp KC Chen, NTU EE & GICE Preliminary Study on Routing in CRNPreliminary Study on Routing in CRN with Unidirectional Links CRN links are generally dynamically g y y y available and can only warrantee unit‐directional transmission, which i bj i igives a new subject in routing April 1, 2009 77KC Chen, NTU EE & GICE Link Properties of CRN (1/2)Link Properties of CRN (1/2) Transmission Power ControlTransmission Power Control Due to different spectrum holes detected by CRs, they may transmit in different power levels and thus forms unidirectional links Primary System CR System April 1, 2009 78KC Chen, NTU EE & GICE Link Properties of CRN (2/2)Link Properties of CRN (2/2) Trust RelationTrust Relation CRN is formed by different parties and groups which may or may not trust each other. Trust relation is inherently unidirectional, thus the logical links between different parties/entities are also unidirectional. • Or due to dynamic nature of CR linksOr, due to dynamic nature of CR links Simple example: A B B trusts A, thus it may help relay packets for A. Link (A, B) forms However, A doesn’t trust B. No link (B, A) April 1, 2009 79 ( , ) KC Chen, NTU EE & GICE Link Model of CRNLink Model of CRN Physical Linksy If node B is within node A’s transmission range, then (A, B) forms a directed physical link Logical Links If (A, B) is a physical link and B is willing to relay packets for A, then (A, B) is also a logical linkB) is also a logical link. Data Link: this link can only pass data packets. Control Link: this link can only pass control packets such as routing y p p g tables. In the following discussion, we assume that as long as a link is a physical link, it is also a logical link. April 1, 2009 80KC Chen, NTU EE & GICE Unidirectional Link Routing Algorithm Classification Proactive Type Distance Vector Distance‐Vector Link State Reactive Typeyp Dynamic Source Routing (DSR) AODV with bidirectional abstract H b id Hybrid: ZRP (zone routing protocol) with unidirectional links • ZRP divides the network into different zones and takes the advantage of pro‐active discovery within a node's local neighborhood (Intrazone Routing Protocol), and use a reactive protocol for communication between these neighborhoods (Interzone Routing Protocol). The Broadcast Resolution Protocol forwards a route request.Broadcast Resolution Protocol forwards a route request. April 1, 2009 81KC Chen, NTU EE & GICE Routing for Wireless Ad hoc NetworksRouting for Wireless Ad hoc Networks Dynamic source routing protocol (DSR) is an on‐demand protocol designed to restrict the bandwidth consumed by control packets in ad hoc wireless networks by eliminating the periodic table‐update messages required in the table‐ d i hdriven approach. Ad hoc On Demand Distance Vector (AODV) routing algorithm builds routes using a route request / route reply query cycle When a builds routes using a route request / route reply query cycle. When a source node desires a route to a destination for which it does not already have a route, it broadcasts a route request (RREQ) packet across the network. Nodes receiving this packet update theiracross the network. Nodes receiving this packet update their information for the source node and set up backwards pointers to the source node in the route tables. In addition to the source node's IP address, current sequence number, and broadcast ID, the RREQ also , q , , contains the most recent sequence number for the destination of which the source node is aware. April 1, 2009 82KC Chen, NTU EE & GICE Reactive Type Routing ‐ DSRReactive Type Routing DSR 5 1 2 3 5 3 1‐2‐3 1‐4 3 4 3 1‐2 4 3 2 1 2 Route E 1 1 1 Error Route Discovery Route Maintenance DSR is easy and suitable, but need extra link maintenance April 1, 2009 83 mechanism KC Chen, NTU EE & GICE AODVAODV D DRREQ RREPD DRREQ Reverse Path RREP Forward Path S S timeout 84 Reverse Path Setup Forward Path Setup AODV assumes there’s reverse link, which does not work in April 1, 2009 84 84 unidirectional link KC Chen, NTU EE & GICE Reverse Distance Vector Algorithm [2]Reverse Distance Vector Algorithm [2] B C D Each node collect incoming links and build an in tree and C A C’ tree links and build an in‐tree, and pass it to other out‐neighbors. B C D B C DB C D ’ A AA C D’ tree B’ tree B D A This algorithm helps establish reverse route for every incoming link April 1, 2009 85 A’ tree link. KC Chen, NTU EE & GICE Opportunistic Link PS Active Primary PS Traffic or Signaling Opportunistic Link y System Timing CR Spectrum Hole Available to CR (Link availability for CRN) Transmission Power Ramping Tsense Cognitive Radio Spectrum Sensing C Transmission Tsense Radio Timing g (a) CR Transmission Opportunity Window PNAμ N A PAAPNNN A PANλ (b) Continuous‐Time Markov Chain model (c) Embedded Discrete‐time Markov Chain for Link AvailabilityApril 1, 2009 86KC Chen, NTU EE & GICE RAN 1 Routing of Opportunistic Links is different from Infrastructure or Internet RAN 1 . . (Uplink) Opportunistic Routing! RAN i. . CR Co‐existing Multi Radio ( p ) CRN MS CR Multi‐Radio Primary Systems RAN j RAN k CR Source MS CR CR MS MS MS CR Sink CR CR MS MS Sink CR CR Cognitive Radio Relay Network (CRRN) (Downlink) CRNApril 1, 2009 87KC Chen, NTU EE & GICE Routing of Opportunistic Links: CRN Local On‐Demand (CLOD) [Chen et al[Chen et al. Wiley Wireless Communications &Mobile Computing, April 1, 2009 KC Chen, NTU EE & GICE 88 & Mobile Computing, 2009] Complex NetworksComplex Networks Conjecture: Routing of opportunistic linksConjecture: Routing of opportunistic links tends to Poisson throughput From random graph theory YES!From random graph theory, YES! Furthermore, CRN in coexisting multi‐radio systems/networks looks similar tosystems/networks looks similar to • Internet/Web connections (complex networks from statistical mechanics)) • Social networks • Much more What is the theory of large and/or complex networking? Any unified theory? April 1, 2009 KC Chen, NTU EE & GICE 89 Applications of CRN April 1, 2009 KC Chen, NTU EE & GICE 90 The reason to apply cognitive radiosThe reason to apply cognitive radios Imagine you order a home robot in 2020g y Your house and surrounding has fully equipment of • Sensor networks for intelligent living (beyond digital home) l l di l d h f l i di li i d• Plat panel display around everywhere for multimedia applications and control of …… • People are mobile requiring huge communication bandwidth • Everything is connected to Internet To help you have a better life, your parents have a safe/healthy life, your kids have a safe/happy/educated life, your wife have an easy lifeyour kids have a safe/happy/educated life, your wife have an easy life Do NOT say: you are going to program the robot to link (through communication networking) all these devices( g g) Over trillion wireless devices by then Most are using spectrum no higher than a few G Hz April 1, 2009 91KC Chen, NTU EE & GICE Smart HomeOne day… Y b h b In 2020, this may be your “k h ” BTW, How is Dad in the hospital? You buy a new home robotsmart “kitchen” Report: Emergency! Where is the fire extinguisher? I am at (2014,324,897) Report: It is safe now!Report: He is OK. Warning I am on fireInternet Warning, I am on fire I t t April 1, 2009 92 It is impossible for you to set/program the new home robot to link all these devices. They should learn to cooperate by all means. Internet KC Chen, NTU EE & GICE Cognitive Radio Network– Bridge the World Together In above scenarios, the different systems (sensor and the , y ( outside communication systems) should rely on cognitive radio to bridge them April 1, 2009 93KC Chen, NTU EE & GICE Robot with Cognitive RadioRobot with Cognitive Radio When Robots equipped with cognitive radio, they can connect q pp g , y to various kinds of systems April 1, 2009 94KC Chen, NTU EE & GICE Health Care SensorsHealth Care Sensors When aged people suffer from some disease (ex. heart attack), g p p ( ), sensors of body area network can inform emergency system through cognitive radio network April 1, 2009 95KC Chen, NTU EE & GICE Health Care SensorsHealth Care Sensors Robot then inform ambulance to take over the emergency g y situation April 1, 2009 96KC Chen, NTU EE & GICE Safety Home SensorSafety Home Sensor Robot is able to communicate other device by its cognitive If a cup of water is turnover……This is probably a dangerous environment for elders…. But if there’s a robot and sensor network Robot is able to communicate other device by its cognitive radioin the house to cooperate to solve the problem and avoid dangerous situation April 1, 2009 97KC Chen, NTU EE & GICE New Research FrontierNew Research Frontier How intelligent devices react in an optimal way g p y based on sensor network(s)? Information fusion Decision Control f Instead of piece‐wise theory, any universal theory to execute? E l [H d Ch IEEE VTC S i 2009]Example: [Huang and Chen, IEEE VTC‐Spring 2009] using an example of firefighting robot to explain advantages to think thoroughly g g y Complete theory is prepared for submission, to explain why sensor fusion, Kalman filter or statistical learning and fuzzy logic are special caseslearning, and fuzzy logic are special cases. April 1, 2009 KC Chen, NTU EE & GICE 98 IEEE SCC41 Dynamic Spectrum AccessIEEE SCC41 Dynamic Spectrum Access IEEE 1900 from 1Q2005, then SCC41 from April 2007 IEEE 1900.1: Standard Definitions and Concepts for Spectrum Management and Advanced Radio System Technologies • Cognitive functionality in wireless communication network (CFWCN) to ITU‐R Study Group 8, WP 8A IEEE 1900.2: Recommended Practice for Interface and Co‐existence Analysis IEEE 1900.3: Recommended Practice for Conformance Evaluation of Software Defined Radio Modules IEEE 1900.4: Co‐existence Support for Reconfigurable, HeterogeneousIEEE 1900.4: Co existence Support for Reconfigurable, Heterogeneous Air Interfaces IEEE 1900.A: Dependability and Evaluation of Regulatory Compliance for Radio Systems with Dynamic Spectrum Accessfor Radio Systems with Dynamic Spectrum Access International standardization has started! April 1, 2009 99KC Chen, NTU EE & GICE Concluding Remarksg Dynamic spectrum access to enhance spectrum efficiency is a solution to crowded spectrumsolution to crowded spectrum Cooperative networking of CRs to form CRN is a new technology challenge for future wireless communications,technology challenge for future wireless communications, without increasing more air‐interfaces Terminals are smarter and smarter, which makes new services, , , new operations, and new business models possible and needed. Applications in service robots, health/medical cares, intelligent living, etc. Toward ubiquitous computing Toward ubiquitous computing Are you ready for networking trillion wireless devices within a few G Hz band for intelligent applications? Be cognitive! April 1, 2009 100 g pp g KC Chen, NTU EE & GICE To be published in Mid‐April 2009 1. Wireless Communications 2. Software Defined Radio 3. Wireless Networks 4. Cooperative Communications 5. Cognitive Radios 6. Cognitive Radio Networks 7. Spectrum Sensing 8. Medium Access Control 9. Network Layer Design 10. Trust and Security 11 S M11. Spectrum Management April 1, 2009 KC Chen, NTU EE & GICE 101
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