Koilpillai / Dec 2012 / Cognitive Radio1IITB TVWS&CR Workshop Electrical Engineering IIT Madras Control Channel AspectsforCognitive Radio Networks R. David Koilpillai Department of Electrical Engineering Indian Institute of Technology Madras TV White Space and Cognitive Radio Workshop IITBombay December 17, 2012 Koilpillai / Dec 2012 / Cognitive Radio2IITB TVWS&CR Workshop Electrical Engineering IIT Madras What is a Control Channel ? When you turn ON your cell phone How does it find the network ? (synchronization) How does the network recognise the mobile ? How do you obtain service if you are Roaming How does network locate where mobile is currently ?(incoming call) How does mobile let network know it wants to make a call ? (outgoing) How does handover occur if mobile changes location during call ? Answer to all of these questions is the Control Channel(s) Focus on Control Channel aspects in todays talk Koilpillai / Dec 2012 / Cognitive Radio3IITB TVWS&CR Workshop Electrical Engineering IIT MadrasTwo Types of Networks Infrastructure-based Networks Cellular networks Infrastructure includes Basestation, Basestation controller, and Core network All operations controlled by infrastructure Over air-interface, BTS is Master and MS is Slave Infrastructure-less Networks Peer-to-peer(Bluetooth, ZigBee, ) All nodes have equal capability Nodes may assume different roles based on need Decisions made by peer entities Both cases need the functionality of Control Channel(s) Consider both cases for Cognitive Radio NetworksKoilpillai / Dec 2012 / Cognitive Radio4IITB TVWS&CR Workshop Electrical Engineering IIT Madras Family of Networks Hierarchy of wireless networks Wide range of data rates, range Significant developments inWAN / MAN Increasing number of users Need for capacity need for spectrum ?? Cognitive Radio - An attractive option Ref: Cordeiro et al., IEEE 802.22: The First Worldwide Wireless Standard based on Cognitive Radio,IEEE, 2005 Koilpillai / Dec 2012 / Cognitive Radio5IITB TVWS&CR Workshop Electrical Engineering IIT Madras Outline of Presentation SDR Cognitive Radio a paradigm shift Spectrum sensing Cognitive Radio Networks Control Channel designs Challenges and Opportunities Focus on Control Channel aspects Koilpillai / Dec 2012 / Cognitive Radio6IITB TVWS&CR Workshop Electrical Engineering IIT Madras A Interesting Incident From Spectrum April 2011 article by Prof. K. J. Ray Liu (U Maryland) June 7 2010 - Apple CEO Steve Jobs unveiling iPhone4 Failed demonstration 571 Wi-Fi basestations Repeated appeals still not enough capacity to handle demo Source: K.J. Ray Liu, Spectrum April 2011 Koilpillai / Dec 2012 / Cognitive Radio7IITB TVWS&CR Workshop Electrical Engineering IIT Madras Game Theory What happened at Apple iPhone demo ? Room full of bloggers Each wanting to post iPhone information need to stay connected Total 571 Wi-Fi Access Points active Repeated requests (Jobs) to turn off Wi-Fi connections Most people complied some did not Assumption: If others have disconnected, then take advantage Source: K.J. Ray Liu, Spectrum April 2011 Do not know other peoples decision Group behaviour Greedy / selfish behaviour Rational participants in any conflict for resources Will always act selfishly Result: No one was able to watch demo Question: Why not cooperate ??? Koilpillai / Dec 2012 / Cognitive Radio8IITB TVWS&CR Workshop Electrical Engineering IIT Madras CooperationSource: K.J. Ray Liu, Spectrum April 2011 Cooperation Sharing information Control Channel essential for users to share information Koilpillai / Dec 2012 / Cognitive Radio9IITB TVWS&CR Workshop Electrical Engineering IIT Madras SDR Today Ref: www.vanu.com A commercial product Multistandard, multichannel GSM / GPRS / EDGE CDMA/ EV-DO Flexibility Scaleability Cost-effectiveness Koilpillai / Dec 2012 / Cognitive Radio10IITB TVWS&CR Workshop Electrical Engineering IIT Madras SDR Cognitive RadioKoilpillai / Dec 2012 / Cognitive Radio11IITB TVWS&CR Workshop Electrical Engineering IIT Madras SDR Cognitive RadioCognitive Radio =SDR + Sense + Learn + Adapt + Use SDR Frequency + WaveformAgilityWideband RF Frontend High speed DSP Koilpillai / Dec 2012 / Cognitive Radio12IITB TVWS&CR Workshop Electrical Engineering IIT Madras Cognitive Radio Motivation Increasing demand for radio spectrum Broadband wireless demand is rapidly growing Current approach to spectrum allocation Fixed allocation to licensed users Existing scenario Under-utilization of spectrum Spatial and temporal spectral holes exist Innovative approach to improve spectrum utilization Cognitive Radio Initiated by FCC regarding secondary usage of spectrum Cognitive Radio techniques much broader than DSA A radio that is aware of its surroundings and adapts intelligently Reed et al.Koilpillai / Dec 2012 / Cognitive Radio13IITB TVWS&CR Workshop Electrical Engineering IIT Madras SDR Cognitive RadioKoilpillai / Dec 2012 / Cognitive Radio14IITB TVWS&CR Workshop Electrical Engineering IIT Madras Spectrum Sensing Koilpillai / Dec 2012 / Cognitive Radio15IITB TVWS&CR Workshop Electrical Engineering IIT Madras Methods of Spectrum SensingEnergy DetectorCorrelation-based detectorCyclostationarity-based detectorHybrid Detector Filter bank Method Multi-taper Method (MTM) Sensing Criteria (Regulatory) Sensing Period Detection Sensitivity Koilpillai / Dec 2012 / Cognitive Radio16IITB TVWS&CR Workshop Electrical Engineering IIT Madras Aspects of Spectrum SensingTime-varying channelLack of apriori information SNR level, interference, Signal blockage (shadowing, hidden-node) Primary signal transition ON OFF Single shot detection vs. sequential detection Interference due to other CR users Decentralized vs centralized approach Cooperative sensing Control channel for information sharingKoilpillai / Dec 2012 / Cognitive Radio17IITB TVWS&CR Workshop Electrical Engineering IIT Madras Frequency T I M E SpectralAdaptation Waveforms OFDM in Cognitive RadioRef: B. Fette, SDR Technology Implementation for the Cognitive Radio, General Dynamics OFDM Orthogonal Frequency Division Multiplexing - Multicarrier modulation Non-Contiguous OFDM (for CR) Multiple Access OFDM Koilpillai / Dec 2012 / Cognitive Radio18IITB TVWS&CR Workshop Electrical Engineering IIT Madras Control Channel in Cellular SystemsKoilpillai / Dec 2012 / Cognitive Radio19IITB TVWS&CR Workshop Electrical Engineering IIT Madras Radio Interface Protocol User Plane Radio Bearers PDCP BMC Logical Channels Transport Channels Control Plane User Plane RRC Signaling Radio Bearers RLC MAC PHY L3 radio network layer L2 radio link layer L1 radio physical layer Koilpillai / Dec 2012 / Cognitive Radio20IITB TVWS&CR Workshop Electrical Engineering IIT MadrasRadio Interface Protocols Physical Layer (PHY) Transport data from higher layers via physical channels Provides transport channels to the MAC layer Dedicated channels and Common channels Medium Access Control (MAC) Provides services to RLC via logical channels Logical channels characterized by type of data carried Traffic channels and Control channels Radio Link Control (RLC) Reliable data transmission in control plane and user plane Radio Resource Control (RRC) Present in both control plane and user plane protocol stacks Controls all radio-related functionality Koilpillai / Dec 2012 / Cognitive Radio21IITB TVWS&CR Workshop Electrical Engineering IIT MadrasGSM Control Channels Frequency Correction Channel (FCCH) BTS is Master; MS is Slave (DL only) Reference tone (unmodulated carrier +67.7 KHz) Synchronization Channel (SCH) Information for frame synchronization Base station ID, TDMA frame number within hyperframe (0,275647), Broadcast Control Channel (BCCH) Broadcasts (to all mobiles) general information about cell Location area identity, Max transmit power on RACH, Min. Rx level for access Configuration of common control channels Paging Channel (PCH)Random Access Channel (RACH) Slotted Aloha, channel shared by all mobiles Control channel essential for effective communications Koilpillai / Dec 2012 / Cognitive Radio22IITB TVWS&CR Workshop Electrical Engineering IIT Madras GSM Logical ChannelsLogical Channels ControlChannels TrafficChannels Full rate Half rate Physical channel one time-slot on a GSM carrier Many logical channels multiplexed on single physical channelDedicatedCC BroadcastCCCommonCCFCCH SCH BCCH RACH PCH AGCH SDCCH SACCH/FACCH Koilpillai / Dec 2012 / Cognitive Radio23IITB TVWS&CR Workshop Electrical Engineering IIT Madras Bluetooth & ZigBeeKoilpillai / Dec 2012 / Cognitive Radio24IITB TVWS&CR Workshop Electrical Engineering IIT Madras Bluetooth Universal radio interface Operates in 2.4 GHz ISM band (license-free, globally) Short range connectivity Adhoc networks Multiple simultaneous links Low-power, low-cost 1 Mbps, bidirectional Range: 10-100m Advantages over Infrared - NLOS Line-of-sight Ref: J. Haartsen, Ericsson Review, 1998 Koilpillai / Dec 2012 / Cognitive Radio25IITB TVWS&CR Workshop Electrical Engineering IIT Madras Bluetooth Time Division Duplex (TDD) single frequency Tx/Rx Symmetric and asymmetric transmission Timeslot duration 625 microsecs 2.4 GHz unlicensed ISM band Interference: Microwave ovens, cordless, Frequency hopping to avoid interference Pseudo-random hop sequence If collision occurs Error correction mechanisms will correct errors Ref: J. Haartsen, Ericsson Review, 1998 Koilpillai / Dec 2012 / Cognitive Radio26IITB TVWS&CR Workshop Electrical Engineering IIT Madras Bluetooth Piconets / scatternets for adhoc connectivity Synchronous and Asynchronous connections Voice and real-time applications Packet-data applications Master unit and slave units Master controls all timing in piconet Supports authentication and encryption Ref: J. Haartsen, Ericsson Review, 1998 Koilpillai / Dec 2012 / Cognitive Radio27IITB TVWS&CR Workshop Electrical Engineering IIT Madras Bluetooth Networking Bluetooth units within range adhoc connection Piconets (peer-to-peer) One unit assumes role of Master (establishes piconet) BT units in Standby Mode Subset of 32 carriers (out of 69) as wake-up carriers Chosen by own identity Wake-up sequence visit each wake-up carrier once Listening interval = 18 slots (Correlate incoming signal with own identity) Establish Connection (via Inquiry) Transmitinquiry access code (common to all BT units) Inquiry wake-up carriers Recipient responds with ID and clock Paging to establish connection Ref: J. Haartsen, Ericsson Review, 1998 Koilpillai / Dec 2012 / Cognitive Radio28IITB TVWS&CR Workshop Electrical Engineering IIT Madras ZigBee For Control and Sensor Networks Based on the IEEE 802.15.4 StandardRef: Diamond et al., ZigBee Presentation, EE 418/518PHY 868MHz / 915MHz / 2.4GHz MAC Network Star / Mesh / Cluster-Tree Security 32- / 64- / 128-bit encryption Application API ZigBee Alliance IEEE802.15.4 Customer SiliconStackApp ZigBee Alliance Network, Security & Application layers IEEE 802.15.4 PHY and MAC specifications Focus on low data rate, long battery life and secure networking Supports wireless mesh networking Koilpillai / Dec 2012 / Cognitive Radio29IITB TVWS&CR Workshop Electrical Engineering IIT Madras ZigBee Specifications Dual PHY (2.4GHz and 868/915 MHz) Data rates 250 kbps (2.4 GHz), 40 kbps (915 MHz), and 20 kbps (868 MHz) Direct Sequence Spread Spectrum (CDMA) Optimized for low duty-cycle applications ( 500 MHzor Fractional BW FCC permits unlicensed use of UWB (2002) Methods for UWB OFDM-based UWB(OFDM-UWB) Impulse radio based UWB(IR-UWB) 2 . 02>|.|

\| +L HL Hf ff fSource: Arslan et al., Cognitive Wireless Communication Networks, Springer Koilpillai / Dec 2012 / Cognitive Radio50IITB TVWS&CR Workshop Electrical Engineering IIT Madras UWB-based CCCEach CR node is equipped with UWB interface ForCCC Other radio interfaces for data communication UWB cause negligible interference to NB systems Using a common spreading code, nodes discover each other UWB radio interfaces with low complexity and power consumption May be able to achieve radio range of 100 m UWB spreading code common to all nodes After two nodes connect, fix spreading code message exchange Accessing CCC via Aloha scheme Commonly used in UWB systems Koilpillai / Dec 2012 / Cognitive Radio51IITB TVWS&CR Workshop Electrical Engineering IIT Madras Research / Design Challenges CCC Design Security of CC seldom addressed in licensed systems Anti-Jamming techniques widely known New challenges in CR networks Impact of jamming on PU Activity Will affect CC of CR Network Needs to be investigated CRAHN Cognitive Radio Ad Hoc Networks CCC jamming in CRAHN Does not have single node with authority for coordinated action Cluster-based CCC Challenge if Cluster Head is compromised Key Issue- Jamming-resilient CCC Scheme Koilpillai / Dec 2012 / Cognitive Radio52IITB TVWS&CR Workshop Electrical Engineering IIT Madras 802.22 Spectrum Sensing IEEE 802.22 CR-based WRAN PHY and MAC layer protocols Contention based DAB protocol with centralised architecture Each cell Base station (BS) + Associated Secondary users (CPEs) BS and CPEs perform in-band and out-of-band sensing BS indicates the channels to sense, sensing period and false alarm Two stage sensing Fast Sensing rapid measurements s 1 msec (per channel) Fine Sensing 25 msec (per channel) Search for particular signatures of licensed transmissions Avoid intra-network interferencce Koilpillai / Dec 2012 / Cognitive Radio53IITB TVWS&CR Workshop Electrical Engineering IIT Madras 802.22 Dynamic Frequency Hopping Increase 802.22 performance Communicatingon Channel i (in-band channel) Observe availability of next working Channel j (Out of band) To avoid interference to PU, CR network hops to Channel j Begin sensing on Channel i Each user has two receivers Sensing and transmission done in parallel Simultaneous Sensing and Data Transmission (SSDT) Guard bands mitigate interference Dynamic Frequency Hopping Community (DFHC) of coordinated WRANs Koilpillai / Dec 2012 / Cognitive Radio54IITB TVWS&CR Workshop Electrical Engineering IIT Madras 802.22 Double Frequency Hopping Double Hopping for three neighbouring cells Tdata = Transmit time,Tsens = Sensing time No transmission during Quiet period (QP) After Tdata, hop to Sensing Frequency and after Tsens return to working frequency Max number of Neighbour cells= Tdata / TsensKoilpillai / Dec 2012 / Cognitive Radio55IITB TVWS&CR Workshop Electrical Engineering IIT Madras Summary The context of Cognitive Radio A paradigm shift in wireless communications Role of Common control channels (CCC) Cellular, Bluetooth, Zigbee Aspects of CCC for CRs Design of CCC CCC a key enabler for CR Networking Exploit the full potential of CR technology Significant effort needed to design CCC Overall, CR is an exciting field Koilpillai / Dec 2012 / Cognitive Radio56IITB TVWS&CR Workshop Electrical Engineering IIT Madras Best wishes to all participantsof TVWS & CR Workshop Thank You !Q&A davidk@iitm.ac.in Koilpillai / Dec 2012 / Cognitive Radio57IITB TVWS&CR Workshop Electrical Engineering IIT Madras David Koilpillai Profile Education B.Tech,IIT Madras, MS, PhD Caltech, USA Work ExperienceIIT Madras (2002 present) Professor, Electrical Engineering Department Dean (Planning)(October 2011 present)CEWiT Chief Scientist (Jan 2007 July 2007) Co-Chair, IIT Hyderabad Task Force (June 2008 Dec 2009) Ericsson Inc, USA (1990-2002) Director, Advanced Technologies, Research and Patents (R&D team of 75 engineers) Professional Areas of expertise: Cellular, wireless systems, DSP 32 Issued US patents, 3 Indian patent applications Publications: 11 Journal, 45 Conference Research Interests: Broadband wireless communications, 4G cellular, Cognitive Radio Ericsson Inventor of Year Award 1999 Fellow, Indian National Academy of Engineering