cognative radio communication system

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Cognitive Radio Communication Systems:

Cognitive Radio Communication Systems -Rajeshree D. Raut, Assistant Professor, E & C,SRKNEC, Nagpur. 28 th March 2009

Part I – Basics of CR Part II – Performance Optimization of CR :

Part I – Basics of CR Part II – Performance Optimization of CR

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Contents of Part I Inefficiency on Spectrum Utilization What is Cognitive Radio All things to all people Key Elements Cognitive Cycle Various Approaches Various Types Main Functions of Cognitive Radio Potentials Benefits Sharing Scenarios Technical Hurdles

Inefficiency on Spectrum Utilization:

Inefficiency on Spectrum Utilization

What is Cognitive Radio :

What is Cognitive Radio

Mitola Defination:

Mitola Defination

SDR Forum Definition:

SDR Forum Definition

All things to all people :

All things to all people

Key Elements :

Key Elements

Cognitive Cycle:

Cognitive Cycle

Various Approaches:

Various Approaches Interwave, Underlay & Overlay

Interwave Approach contd.:

Interwave Approach contd .

Interwave Approach contd.:

Interwave Approach contd .

Underlay Approach:

Underlay Approach Allows the cognitive users to operate on a certain frequency band, either unoccupied or not, provided that the interference caused to primary users remains below a fixed threshold.

Overlay Approach:

Overlay Approach

Overlay Approach contd.:

Overlay Approach contd.

Various Types:

Various Types Full Cognitive Radio (“Mitola Radio”) Spectrum Sensing Cognitive Radio Licensed Band Cognitive Radio (e.g. WRAN-Wireless Regional Area Network, unused Television Channels) Unlicensed Band Cognitive Radio

Main Functions of Cognitive Radio :

Main Functions of Cognitive Radio Spectrum Sensing * Transmitter detection ( Cognitive Radios must have capability to determine if a signal from a primary transmitter is locally available, matched filter detection, energy detection, etc.) * Cooperative detection ( Information from multiple Cognitive Radio users are incorporated for primary user detection.) * Interference based detection Spectrum Management * Spectrum analysis * Spectrum decision Spectrum Mobility ( for Seamless operation exchanges its frequency of operation) Spectrum Sharing ( Spectrum Scheduling method)

Potentials Benefits :

Potentials Benefits

Potentials Benefits contd.:

Potentials Benefits contd.

Sharing Scenarios:

Sharing Scenarios

Technical Hurdles:

Technical Hurdles

Technical Hurdles contd.:

Technical Hurdles contd. The Hidden Node Problem

Technical Hurdles contd.:

Technical Hurdles contd. The Hidden Node Solutions

Technical Hurdles contd.:

Technical Hurdles contd. Control Mechanisms

Technical Hurdles contd.:

Technical Hurdles contd. Spectrum Mobility

Part II Performance Optimization for Cognitive Communication Systems:

Part II Performance Optimization for Cognitive Communication Systems

Points to be Covered:

Points to be Covered Performance Improvement /maintenance over CR Advance Source Coding Techniques (Perceptual Coding) Spread Spectrum Techniques/ Multiple Access Techniques, CDMA Channel Coding Techniques Conclusion & Scope for Research Honors/ Publications

Data Compression at Low BW Advance Source Coding Algorithms:

Data Compression at Low BW Advance Source Coding Algorithms

Perceptual Coding::

Perceptual Coding: Perceptual coding uses a model of the destination, i.e. the human being who will be using the data, rather than a model of the signal source. Perceptual coding attempts to remove parts of the signal that the human cannot perceive.

Perceptual Coding (cont.)::

Copyright 1993, 1995, 1998, 2001,2003 James D. Johnston now at Microsoft Corporation Perceptual Coding (cont.): Perceptual coders will, in general, have a lower SNR than a source coder, and a higher perceived quality than a source coder of equivalent bit rate.

Masking (Human Acoustics):

Masking (Human Acoustics) In the presence of the signal, the noise sounds much quieter (almost undetectable) Due to the anatomy of the ear, loud sounds mask quieter sounds at nearby frequencies Effectively, the threshold of hearing is raised to the masking threshold The masking threshold can be estimated using a psychoacoustic model and exploited by the coder Signal Signal + Noise (SNR = 24 dB) Noise

Subband Coding:

Subband Coding Sub-band filter bank Scale and Quantize Multiplex and Data Format Code Side Info FFT Psycho-acoustic model ENCODER Digital Audio In De-Multiplex Descaler & Dequantizer Inverse filter bank Decode Side Info DECODER Digital Audio Out Coded Audio In Coded Audio Out Masking thresholds

Psychoacoustics:

Psychoacoustics Substantial improvements to our sub-band coder are possible using psychoacoustics Psychoacoustics is the study of how sound is perceived by the ear-brain combination Of interest to us: how the threshold of hearing is not constant In fact, the threshold of hearing constantly changes due to masking …

A Typical Psychoacoustic Model::

A Typical Psychoacoustic Model: Cochlear Filter Modeling Threshold Estimation Absolute Threshold, Time artifact control, forward masking Tonality Calculation Short Term Signal Spectrum Short Term cochlear energy model Tonality Estimate Estimated Psychoacoustic Threshold

Additional Side Information:

Additional Side Information The audio signal is processed in discrete blocks of samples known as frames Each frame of each sub-band is: Scaled to normalise the peak signal level Quantised at a level appropriate for the current signal-to-mask ratio The receiver needs to know the scale factor and quantisation levels used This information must be embedded along with the samples The resulting overhead is very small compared with the compression gains

Transform Coding:

Transform Coding It is an improved version of subband coding, wherein an additional KLT (Karhaunen Loeve) Block is include to find the uncorrelated spectral domains. A DFT concatenated with DCT can give similar results & is economical for implementation.

A simplified view of CELP:

7 Dec'08 Comp30291 Section 8 38 A simplified view of CELP Derive LPC filter coeffs Find fundamental (pitch) frequency Construct excitation from codebook entry & long term predictor LPC synthesis filter Compute cross-correlation to measure similarity Control codebook search to maximize similarity. Apply perceptual weighting Speech Trans- mit Transmit results of search

Performance at higher BW:

Performance at higher BW Channel Coding at low BER, maitaining data rates SS Techniques to maintain performance at High Data Rates.

Conclusions:

Conclusions

Scope for Research:

Scope for Research 1. Adaptive systems from the heart of CR 2. SDR’s are the best form of Adaptive Systems 3. SDR Implementations of the various key elements of Communication Systems is the demanded research in this field 4. Spectrum Sensing & Selection of Optimal bandwidth in the available Spectra.

Key References for Cognitive Radio Systems :

Key References for Cognitive Radio Systems Richard Lau and etal., “ Cognitive Adaptive Radio Teams”, work supported by DARPA Qiwei Zhang and etal.,“ Adaptive OFDM System Design For Cognitive Radio” Tomoaki Ohtsuki, “Rate Adaptive Indoor Infrared Wireless Communication Systems Using Repeated and Punctured Convolution Codes”, 1999 IEEE J. E. Kleider and W.M. Campbell, “An Adaptive –Rate Digital Communication System for Speech”, 1997 IEEE . “Cognitive Radio”, from Wikipedia, the free Encyclopedia

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Honors Received Reviewer for IEEE Communication Letters. Reviewer for the International Open Access Journal IJCA and appointed over its Editorial Panel. Reviewer for the IEEE International Conference TENCON-2009., Singapore. Reviewer for the WSEAS International Conferences, 2009-10. Highly Appreciated for the Voice Presentation as a Speaker with the Lecture entitled “BER Performance Maintenance at High Data Rates in Cognitive Radio”, given at CONIELECOMP 2010, at Mexico, Feb 24 th 2010

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Publications Total count - 22 International Publications - 08 (06- International Journals{02- Open Access}, 02- IEEE Explore Digital Library) IEEE Transactions Special Issue WSEAS Transactions on Communications IJCA- International Open access Journal on Computer Applications WSEAS- System Science & Simulation in Engineering IJCSCT- International Journal on Computing Sciences & Communication technology, APIIT India & Stafford Shire University U.K. International Conferences- 08 (USA, Mexico, Italy, India, Malaysia) Paper at WSEAS, Italy nominated in Best papers for the Conference National Conferences-08 (Paper at NIIT Rourkela Best paper in the Conference)

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