Spectrum Sensing in Cognitive Radio - Fading, Diversity and User Cooperation By Sanjeewa P. Herath...
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Transcript of Spectrum Sensing in Cognitive Radio - Fading, Diversity and User Cooperation By Sanjeewa P. Herath...
Spectrum Sensing in Cognitive Radio - Fading, Diversity and User
CooperationBy
Sanjeewa P. Herath
Examination Committee:1.Dr. R.M.A.P. Rajatheva (chairman),2.Prof. Kazi m. Ahmed,3.Dr. Poompat saengudomlert.
MASTER THESIS COMPETITION18TH May 2009
Wireless access & Cognitive Radio• Wireless access – high demand – Every one with mobile phones– Demand: High speed internet, TV, on-line movie
• But, the available radio resource is very limited
• Advantages– High speed internet, bandwidth– Low cost – Not using additional resources– Good QoS, Routing implementation
Conventional Licensed User (Primary User) NetworkUnlicensed User (Cognitive User) Access
• Solution: Allow cognitive user access
?
PU 1 PU 2PU 3 idle
CU 2CU 1
How to Detect?
Detection by Cognitive Users
• Measure the energy content– Can use in CDMA, 3G, Wi-Max, 4G/OFDMA etc– Guaranteed security to primary users– Cost effective, simple in structure, less hardware
PU Transmits Energy/PowerCU 2CU 1
The objective
• IEEE 802.22 – First cognitive radio standard– 90% detection reliability even when 0 dB signal-to-
noise ratio (SNR)
PU
CU
WALL
WAL
L
(2) LOW SIGNAL ENERGY
(1) MULTIPATH PROPAGATION
Very weak signal
PU Base Station
Diversity Combining
• Concept– Multiple copies of the same signal– Combine them
PU
CU
WALL
WALL
(1) MULTIPATH PROPAGATION
Very weak signal
PU Base Station
Remove Fading Effects
Contribution• Analysis of communication systems is complex• High chance of making mistakes
1. Theoretical analysis– PDF approach (new)– MGF approach (new)
2. Simulation Model (new)
• Solution: Two way analysis
Diversity Combining
Detection with MRC diversity (Rayleigh, False alarm probability 0.1, u=1)
Two way analysis
0 dB
More Diversity• Six different diversity techniques are
proposed– Motivation: Less complex, low cost solutions
• Proposed schemes1. Maximal Ratio (MRC) - 20% 2. Equal gain (EGC) - 16%3. Square-law (SLC) - 12%4. Square-law selection (SLS) - 10% 5. Selection (SC) - 11 %6. Switch-and-stay (SSC) - 2%
Cooperative Detection
• Concept– PU assists CU to detects its presence – Tolerate capacity by PU
PU
CU
WALL
(2) LOW SIGNAL ENERGY
Very weak signalPU Base Station Improve signal strength
• Algorithm based solution– Convex optimization
• Based on IEEE 802.22 standard
Cooperative Detection
Cooperative Detection (2 Subcarriers, AWGN Nc
i={2,1}, Nbi={2,2})
Flexible
Low Data Rate
Industrial Contribution• 66% (out of 90%) is achieved– 30 % by energy detection– 20 % by diversity– 16 % by cooperation
• The rest of 24% by CU cooperation• Relax assumption– Channel estimation– User mobility
Future Work
Contribution to Academia (7)1) Sanjeewa Herath, Nandana Rajatheva,``Analysis of Equal Gain Combining
in Energy Detection for Cognitive Radio over Nakagami Channels,“ IEEE GLOBECOM `08, pp. 1-5, Nov.-Dec. 2008, USA.
2) Sanjeewa Herath, Nandana Rajatheva, Chintha Tellambura,``On the Energy Detection of Unknown Deterministic Signal over Nakagami Channels with Selection Combining,“ IEEE CCECE `09, May 2009, Newfoundland, Canada.
3) Sanjeewa Herath, Nandana Rajatheva,``Analysis of Diversity Combining in Energy Detection for Cognitive Radio over Nakagami Channels,"Accepted for IEEE Int. Conf. ICC `09, Jun. 2009, Germany - to appear.
4) Sanjeewa Herath, Nandana Rajatheva, Chintha Tellambura,``Unified Approach for Energy Detection of Unknown Deterministic Signal in Cognitive Radio over Fading Channels,“Accepted for IEEE Int. Conf. ICC `09, Jun. 2009, Germany - to appear.
5) Sanjeewa Herath, Nandana Rajatheva, Poompat Saengudomlert, ``Primary and Cognitive User Cooperation in Detection,“ Submitted for IEEE GLOBECOM '09, Nov.-Dec. 2009, USA.
Contribution to Academia (7)1) Sanjeewa Herath, Nandana Rajatheva, Chintha
Tellambura,``Performance Analysis of Square Law, Switch and Stay Diversity Techniques for Energy Detection over Nakagami Fading Channel,” In preparation to be submitted to IEEE Transactions on Communications.
2) Sanjeewa Herath, Nandana Rajatheva, Chintha Tellambura,``Energy Detection of Unknown Deterministic Signal in Fading and Diversity Reception,”In preparation to be submitted to IEEE Transactions on Communications.