Cooperative tv spectrum sensing in cognitive radio BY DEEPAK PORIYA
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Transcript of Cooperative tv spectrum sensing in cognitive radio BY DEEPAK PORIYA
Cooperative TV Spectrum Sensing in Cognitive Radio :for Wi-Fi Networks
PRESENTED BY :DEEPAK KUMAREC6 111424B.TECH NIT KURUKSHETRA
Content
INTRODUCTION
SYSTEM MODEL : WI-FI ZONE
ENERGY DETECTION ALGORITHM
SPECTRUM SENSING:
SINGLE USER
COOPERATIVE SENSING
TOTAL DETECTION ERROR PROBABILITY
OPTIMAL SENSING TIME
NUMERICAL RESULT
CONCLUSION
INTRODUCTION
SHORTAGE OF SPECTRUM
USE OF TV SPECTRUM IN WI-FI NETWORKS
ACCURACY :
• S E N S I N G T I M E
• N O . O F S E N S I N G n O D E S [ S U ’ S ]
OBJECTIVE :
O P T I M A L N O . O F S U ’ S
O P T I M A L S E N S I N G T I M E
M I N I M I Z A T I O N O F D E T E C T I O N E R R O R P R O B A B I L I T Y
SYSTEM MODEL: WI-FI ZONE
CPE : CUSTOMER PREMISES
EQUIPMENT [ SMART PHONE
LAPTOPS ETC. ]
ELEMENTS:
o PU
o SU
o FC [ FUSION CENTER ]
ENERGY DETECTION ALGORITHM
Primary Signal
Y(t) = { 𝑛 𝑡 𝐻𝑜ℎ𝑠 𝑡 +𝑛 𝑡 𝐻1
}n(t) =white noise
h =channel coefficient
False Alarm Probability
𝑃𝑓 = 𝑃 𝑌 > 𝜆 𝐻𝑜
Miss Detection Probability
𝑃𝑚 = 𝑃(𝑌 < 𝜆|𝐻1)
Ho is the hypothesis of absence of primary user
H1 is the hypothesis of presence of primary user
SINGLE USER spectrum SENSING :
FRAME :𝜏 + (𝑇 − 𝜏)
𝝉= SENSING TIME
T−𝝉= DATA TRANSISSION
TIME
Single user SPECTRUM sensing
Transmission throughput: 1. Secondary User Throughput
2. Primary User Throughput
o First term corresponds to the secondary user throughput
o Second term corresponds to the primary user throughput
o T is frame duration and τ is spectrum sensing time.
o P(H0) [P(H1) ] is a probability for primary user being absent [present ].
o C0 (C1) is a secondary user’s channel capacity under the hypothesis H0(H1).
COOPERATIVE SPECTRUM SENSING
Cooperative spectrum sensing schemes :
To determine the presence of primary user (PU) with the collected information from secondary users (SUs) at a fusion center (FC).
Three kind of decision rules :
OR RULE
AND RULE
K OUT-OF- N-RULE
OR-RULE
The OR-rule declares presence of PU as long as at least one SU detects the PU.
The OR-rule has very low mis-detection probability which is helpful to protect the primary user.
Relatively high false alarm probability which makes the spectrum usage inefficient.
AND RULE
The AND-rule declares presence of PU only when all Su’s report of PU presence.
The AND-rule has very low false alarm which makes spectrum usage efficient.
It may not protect the primary user from strong interferences from the secondary users.
Quality of services for primary user is not guaranteed.
K -out -of -n -rule
K-out-of-N-rule which declares the presence of primary user when more than K-out-of-N SUs detect presence of primary user.
Special cases of K-out-of-N-rule with different values of K.
OR RULE : WHEN K=1
AND RULE : WHEN K=N
RULE
RULE
RULE
TOTAL DTECTION ERROR PROBEBILITY
Total detection error probability is defined as the average of mis-detection probability and false alarm probability
P(H0) is a probability for primary user being absent .
P(H1) is a probability for primary user being present.
OPTIMAL KOpT FOR K-OUT –OF –N RULE:
OPTIMAL SENSING TIME FOR MULTIPLE USERS
The longer spectrum sensing time guarantees low detection error probability BUT it reduces transmission throughput because data are not transferred during sensing time.
Throughput consists of two terms:
Secondary user throughput
Primary user throughput.
TOTAL THROUGHPUT
THE PRIMARY USER THROUGHPUT
The total throughput
For Optimal sensing time R_total
has to be differentiated in terms of
spectrum sensing time τ and set
to zero.
It is too complex to obtain
analytical expression for optimal
sensing time.
Instead it can be numerically found
such as the sensing time which
yields the highest total throughput.
SECONDARY THROUGHPUT
NUMERICAL RESULT
Optimal number KOUT of secondary users for K-out-of-N-rule
Compare optimal spectrum sensing time and transmissionthroughput for three detection rules.
Assumption:
o The frame duration is 100ms.
o The frequency bandwidth of primary user is 3MHz.
o The signal-to noise power ratio =20dB.
o C0 = log2(1+SNR) = 6.6582 bps.
o P(H0)=P(H1)=0.5.
Optimal number of secondaRY users
o Three detection error
Probabilities (Pt Pf Pm) versus
number of secondary users K
o Vertical dotted line corresponds
to KOUT .
MATLAB IMPLEMENTion:
o Optimal K increases from
13 to 23 as mis-detection
probability decreases from
0.26 to 0.01.
o Larger K usually increases
mis-detection probability
but decreases false alarm
probability.
o However when mis-
detection probability is
very low larger K is better
to reduce false alarm
probability.
Total throughput:
Blue line for primary user
Red line for secondary user
Green line for total throughput
OPTIMAL SENSING TIME FOR MULTIPLE USERS
Total throughput for three
kinds of detection
rules versus sensing time.
o OR rule: 1.26ms
o AND-rule: 1.56ms
o K out-of-N-rule: 0.84ms
CONCLUSIONS
A cognitive radio system using a vacant TV channel in a Wi-Fi zone to achieve increased data transmission capacity for a Wi-Fi service.
We derived the optimal threshold number of secondary users for K-out-of-N-rule of cooperative spectrum sensing in the constraint of minimum detection error probability.
We also numerically presented the optimal sensing time which maximizes the data throughput.
This proposed CR scheme may solve the spectrum shortage problem due to explosively increasing Wi- Fi data traffic due to smart phones.
THANK YOU PRESENTED BY :DEEPAK KUMAR ROLL NO .111424EC6 B.TECH