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
[email protected] 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