Effective Utilization of Radio Frequency Spectrum in Communication Networks using

Cognitive Radio

Presented by

J. Sarada LakshmiResearch Scholar

Dept. of Computer Science and Systems Engg.Andhra University

Jammi_sarada@yahoo.com

Contents• Introduction• Cognitive Radio• Architecture & Protocol Stack• CR Functions– Spectrum Sensing– Spectrum Decision– Spectrum Sharing– Spectrum Mobility

• Conclusion & Future Directions

Today’s Wireless Network• Radio Frequency Spectrum ranges from 3KHz

to 300GHz used for wireless communication.• Most portion of the Spectrum (Licensed) is

assigned to Licensed users where the users can use exclusively without any interference.

• Few portion of the spectrum is left which is used for industrial, scientific and medical purpose(ISM band) which is unlicensed.

• Wireless technologies like Wi-Fi, Bluetooth, Cordless phones,3G etc operate on unlicensed band.

LICENSED BAND(Primary Users)

UNLICENSED BAND(Secondary Users/Cognitive Radio Users)

• A report from FCC concluded that licensed bands are under-utilized where as unlicensed are becoming scarce.

• Fixed Spectrum assignment policy leads to inefficient utilization of spectrum

• To overcome this problem Cognitive Radio (CR) emerged as a key technology to dynamically access the licensed radio spectrum in an opportunistic manner by the secondary users without making any harmful interference to primary users.

Spectrum Hole Concept

• Temporarily unused licensed radio frequencies by primary users called as white spaces or spectrum holes

Cognitive Radio• Cognitive Radio (CR) is an intelligent wireless

communication technology to dynamically access the licensed radio spectrum in an opportunistic manner by the secondary users without causing any interference to primary users.

• CR uses a radio called Software Defined Radio(SDR).

• SDR can dynamically change the parameters of spectrum like operating frequency, bandwidth, modulation scheme and transmission power.

Objectives of CRSpectru

m Sensing

Spectrum

Decision

Spectrum

Sharing

Spectrum

Mobility

Cognitive Radio Architecture

• Classified into– Infrastructure based CR Network–CR Adhoc Network• Co-operative• Non Co-operative

Communication Protocols for Cognitive Radio

Spectrum Sensing• Primary User Detection: – To detect the unused frequencies (spectrum holes)

over a frequency band.– To monitor the Spectrum band during the CR user

transmission in order to detect the presence of primary users to avoid interference.

• According to Ian F. Akyildiz [1], PU detection techniques classified into three groups’– Primary transmitter detection – Primary Receiver detection – Interference temperature management.

• Sensing Control: Co-ordinates the sensing operations and its neighbors in a co-operative manner.

sensing controlInterference Avoidance

(In-band sensing)Sensing Time

How long to sense the spectrum?

Transmission TimeHow long to transmit data?

Fast Discovery(out-of-band sensing)

Sensing orderWhich spectrum to sense first?

Stopping RuleWhen to stop searching/sensing?

Spectrum Decision

• Find out the best spectrum among the available bands.• Based on channel characteristics and

primary user activities.

• Spectrum Characterization:– Observe the characteristics of each available

spectrum

RF Environme

ntcharaterizat

ion

channel identificati

onChannel capacity

Switching Delay

Channel Interferenc

eChannel Holding

time

Error Rate

CR Location

Path Loss

• Spectrum Selection: • From the characteristics observed for each

available band, the most appropriate band should be selected.

• Then the reconfiguration of channel parameters according to the channel selection should be done in spectrum decision.

Spectrum Sharing

• Provides mutual sharing of spectrum band by multiple CR users without making any interference to primary users.

• CR MAC protocols used for controlling the access of radio spectrum by CR users simultaneously. CR MAC Protocols

Random AccessSRAC MAC

HC MACDOSS

Time slottedC-MAC

HybridOS-MAC

Cog-MeshPOMDP

SYN-MACOppurtunistic MAC

Spectrum Mobility

• Functionalities of Spectrum mobility .– Spectrum Handoff– Connection Management

• CR users occupy the licensed band in an opportunistic way so they have to switch to another band when a primary user is observed--Spectrum handoff.

• Handoff can be done in 2 ways.– Pro-active– Re-active

• Connection Management: Spectrum handoff requires CR user to switch from current spectrum frequency to new frequency band which result in some latency. This latency time should be known so that CR user can guess the impact of temporary disconnection and preserve the ongoing communication with minimum performance degradation.

Conclusion and Future Directions• Cognitive Radio –Next generation

heterogeneous wireless network and provides the co-existence of different wireless technologies.

• Applications of Cognitive Radio:–E-health Services–Intelligent Transportation system–Emergency networks

• Open challenges for deployment of Cognitive Radio are– Accurate Sensing– Proactive Spectrum decision– Efficient and balanced usage of spectrum holes.– Seamless spectrum mobility and QoS provisioning.

• Finally Cognitive Radio is without any doubt a critical path to the wireless communication networks in future.

References

• [1] Ian F.Akyildiz, Won-Yeol Lee,Kaushik R.Chowdary “CRAHNS: Cognitive radio adhoc networks” Adhoc Networks, ELSEVIER, Vol. 7,No. 5,July 2009, PP 810-836.

• [2] Jose Marinho, Edmundo Monteiro “Cognitive Radio : survey on communication protocols, spectrum decision issues and future research directions” Wireless networks (2012) 18:147-164.

• [3] Ian F.Akyildiz, won-yeol Lee,Mehmet C.Vuran,Shantidev Mohanty “Next generation/dynamic spectrum access/Cognitive radio wireless networks: A Survey” Computer networks journal Elsevier (2006) 2127-2159.

• [4] Tevfik yucek and Huseyin Arslan “A Survey of Spectrum Sensing Algorithms for Cognitive Radio Applications” IEEE Communications surveys & tutorials Vol. 11 No. 1 first quarter 2009.

• [5] Moshe Timothy Masonta ,Mjumo Mzyece, Ntsibane “Spectrum Decision in Cognitive Radio Networks: A Survey” IEEE Communications surveys & tutorials Vol. 15 No. 3 Third quarter 2013.

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• [9] Pushp Maheswari, Awadesh Kumar singh: “A Survey on spectrum Handoff techniques in Cognitive Radio Networks”,IEEE International Conference on Contemporary Computing and Informatics(IC3I), May 2014.

• [10] Ian F.Akyildiz, won-yeol Lee,Mehmet C.Vuran,Shantidev Mohanty, “ A survey on spectrum management in cognitive radio networks”,IEEE Communications Magazine,vol.46,no.4,PP.40-48,April 2008.

• [11] Simon Haykin, “Cogniive Radio:Brain empowered wireless communications”, IEEE J.Selected Areas Communications, vol.23, no.2,pp.201-220,Feb 2005.

• [12] Simon Haykin, ”Spectrum sensing for Cognitive Radio”, Proceedings of the IEEE, vol.97, no.5, pp 849-877, May 2009.

• [13] MITOLA. J., “The Software Radio Architecture”, IEEE Communications Magazine, Vol 33, No. 5, pp. 26-38, 1995.

• [14] Sai Shankar N, Carlos Cordeiro and Kiranchallapali, ”Spectrum agile radios: Utilization and Sensing architectures”, Proc. The first IEEE symposium on new Frontiers in Dynamic Spectrum Access Networks, pp. 160-169,2005.

• [15] Aleksander Jovicic and Pramod Viswanath, “Cognitive Radio: An Information-Theoretic Perspective”, IEEE transactions on information theory 2008.

• [16] Fredrich K.Jondral,”Software Defined Radio-Basics and Evolution to Cognitive Radio”, EURASIP Journal on Communications and Networking 2005.

Any Queries?Thank You