study

Dynamic Channel Selection

Algorithm for Cognitive Radios

Circuits and Systems for Communications, 2008. ICCSC 2008. 4th IEEE International Conference on

26-28 May 2008 Page(s):275 - 278

Digital Object Identifier 10.1109/ICCSC.2008.64









Advisor: Wen-Hsing Kuo

Presenter: Che-Wei Chang

Network Model

GV , E 

V : is the set of the cognitive users

N  V : and E is the set of links between the active cognitive users







Su

The set of neighbors of active cognitive user u, u V





d u 

The degree of cognitive user u .







D  max d u  (1)

uV

2

Dynamic Spectrum Sharing Algorithm(1/2)



For i   u (here u  1 ), Pi ,u  v is expressed by



Pi ,uv  1  p 

Sv

(2)



While for i   u , Pi ,u  v is given by

Pi ,uv  p1  p 

Sv

(3)

Then the average probability of success over a frame for transmission u  v

is given by 1 N

Pu v 

N

 P

i 1 i ,u v





1  N  1 p

 1  p  Sv (4)

N



3

Dynamic Spectrum Sharing Algorithm(2/2)



The system throughput for each available channel is written as

1  N  1 p

P

1

 1  p  Sv (5)

N uV N

~

For analysis more tractable, the system throughput P is approximated by P

1  N  1 p

V N 1  p  avg

~ 1 (6)

P

S



N u



S avg denotes the average degree in the CR network, which is given by



Savg  1 / N uV Su (7)









4

Simulation Results(1/4)

Number of Average Number of Average

Number of Number of

active CR degree in CR p active CR degree in CR p

channels channels

users network users network

1 5 2 0.16 1 5 3 0.06

1 10 2 0.26 1 10 3 0.16

1 15 2 0.28 1 15 3 0.2

1 20 2 0.3 1 20 3 0.22

1 25 2 0.3 1 25 3 0.22

1 30 2 0.32 1 30 3 0.22



Table 1. Table 3. Table 2.

Degree = 2 Number of Average

Number of

active CR degree in CR p

channels

users network

1 5 5 0

1 10 5 0.08

1 15 5 0.1

Degree = 3

1 20 5 0.12

1 25 5 0.14

1 30 5 0.14 5

Simulation Results(2/4)









Fig.2. System throughput comparison versus the number of active CR users for K=1

6

Simulation Results(3/4)









Fig.3. The system throughput in terms of the number of active CR users for K=2

7

Simulation Results(4/4)









Fig.4. The system throughput versus the number of available channels for N=5

8

Thanks for your attention!