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书 书 书

50

 

2015

       

西

 

 

 

 

 

 

 

JOURNAL OF SOUTHWEST JIAOTONG UNIVERSITY

        Vol. 50  No. 1 Feb. 2015

稿

20131126

:国

61102069

);江

BK20140828

:刘

1984 -

),男

,讲

,博

,研

线

Email

liuxinstar1984@ nuaa. edu. cn

:刘

,仲

线

西

2015

50

):

6671.    

02582724

2015

01006606    DOI

10. 3969 / j. issn. 02582724. 2015. 01. 010

认知无线电带宽频谱感知性能分析及优化

 

 

(南

,江

苏南

210016

 

:为

线

,根

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使

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,通

,最

使

MATLAB

仿

,结

:相

,当

0. 5

,带

使

30%

;当

0. 2

,带

使

0. 3

bit / s

/ Hz.

:认

线

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TN92   

Optimization and Performance Analysis for

Bandwidth Spectrum Sensing in Cognitive Radio

LIU Xin

  ZHONG Weizhi

College of Astronautics

Nanjing University of Aeronautics and Astronautics

Nanjing 210016

China

Abstract

To decrease interference to primary user

PU

in cognitive radio

CR

),

a bandwidth

spectrum sensing model of secondary user

SU

over the whole frame was built through dividing the

communication bandwidth into sensing frequency band and transmission frequency band

according to

the status variation of PU. In this model

SU uses part of the bandwidth to perform spectrum sensing

and the rest to transmit data in a frame. Subject to the constraints of the interference to PU and the

false alarm probability of SU

the spectrum efficiency of SU was maximized through jointly optimizing

sensing bandwidth proportion and detection probability. Using the MATLAB software to simulate the

interference probability and the spectrum efficiency

it is found that compared to the conventional time

spectrum sensing

the bandwidth spectrum sensing decreases the interference probability to PU by 30%

with the false alarm probability of 0. 5

and improves the spectrum efficiency of SU by 0. 3

bit / s

/ Hz

with the interference probability of 0. 2.

Key words

cognitive radio

spectrum sensing

spectrum efficiency

optimization

   

线

cognitive radio

CR

)通

用户(

secondary user

SU

)择机使用主用户

primary user

PU

)未

使

,大幅度提

. SU

,需

PU

,如

PU

存在

SU

必须停止传输

,避免对

PU

24

SU

PU

,因

PU

CR

,即

SU

PU

,检

PU

(2)

 

,等

:认

线

Marinho

“先听后传”的

CR

媒体访问控制(

media access

control

MAC

)层

,通

MAC

,可

SU

PU

;丁

PU

,用

SU

CR

,分

SU

,感

CR

Liang

89

,通

,最大化

SU

Choi

PU

,主

SU

10

SU

使

,其

SU

PU

,避

PU

1 

PU

1. 1 

    SU

,能

PU

SU

,实

PU

,表

,不存在

PU

,否

SU

PU. SU

,表

11

),

  Ω

hs

+ n

),

  Ω

{

σ

PU

SU

PU

;假

Ω

Ω

PU

m = 1

,…

、检

,则

M = tW

M m = 1

,根

据中心极限定理

)近

,表

σ

σ

/ M

),

  Ω

((

1 + γ

σ

,(

1 + 2γ

σ

/ M

),

  Ω

{

)表

、方

γ = p

/ σ

),能

检测的虚警概率

和检测

12

= P

Z≥λ Ω

( (

λ

σ

- 1

)

)

= P

Z≥λ Ω

 

( (

λ

σ

- γ

- 1

)

1 + 2

γ

)

:函

π

+∞ x

-t22

dt .

)和

),

= Q

1 + 2

γQ

- 1

+ γ

Wt

1. 2  PU

    PU

ONOFF

1314

. ON

PU

,即

Ω

OFF

PU

,即

Ω

PU

Ω0

+ u

  P

Ω1

+ u

Ω

Ω

Ω

Ω

PU

Ω0

T 0

tu

-u0t

dt =

1 - e

-u0T

- Te

-u0T

   Ω Ω

1  PU

Fig. 1  PU state model

2 

2. 1 

    SU

使

个可用的信道中选择一个最可能空闲的信

15

,主

使

SU

,因

、检

SU

,需

PU

,并

69

SU

线

使

,只

(3)

西

 

 

 

 

 

 

 

50

PU

SU

,否

SU

,当

SU

,此

PU

SU

PU

   









 

















 







 

2 

Fig. 2  Time spectrum sensing model

SU

线

,一

线

,另

线

SU

使

,其

SU

知和数据传输是同时进行的

,因此

SU

在整个数据帧内可以随时检测

PU

的活动状

. SU

PU

,需

线

SU

,否

SU

PU

  



 









 





 

  





 

3 

Fig. 3  Bandwidth spectrum sensing model

,且

,时

SU

PU

SU

PU

SU

PU

PU

= P

Ω1

(

1 - P

+ P

T - t

Ω0

)

SU

PU

,因

SU

PU

SU

PU

= P

Ω1

1 - P

10

2. 2  SU

   

αW

0 ≤α≤1

)、

SU

1 - α

SU

PU

SU

PU

= log

(

1 +

σ

)

= log

(

1 +

σ

1 + γ

)

}

11

SU

SU

C =

1 - α

)(

Ω0

1 - P

  P

Ω1

1 - P

12

)代

12

),有

α

1 - α

×

Ω0

1 - Q

1 + 2

γQ

- 1

+ γ α

WT

)]

  P

Ω1

1 - P

},

13

α

3 

   

:在

PU

SU

,通

α

,最

SU

,表

max

α

Pd

α

),

s. t. P

≤β

  P

≤0. 5

  0≤α≤1

}

14

β

≤0. 5

SU

据式(

10

),由

≤ β

得到

≥ v

v = 1 -

β / P

Ω1

13

),由

)的

α

)是

,即

α

α

因此只有当

= v

才能取得最大

= v

,式

14

)简

α

max

α

α

1 - α

×

     

1 - Q

+ A

α

))

+ A

),

s. t. P

≤0. 5

  0≤α≤1

}

15

1 + 2

γQ

- 1

);

  A

= γ

WT

= P

Ω0

  A

= P

Ω1

1 - v

15

)是

,即

α

],使

α

)取

α

)关于

α

的一阶和二阶导数

,表

C′

α

1 - α

2 2π

α

exp

- 0. 5

+ A

α

(4)

 

,等

:认

线

 

1 - Q

+ A

α

))

+ A

),

16

C″

α

= -

4α 2

π

exp

- 0. 5

+ A

α

×

(

 

α +

α

1 - α

+ A

α

)

17

16

),由

> 0

> 0

> 0

0 ≤

≤1

lim

α→0

C′

α

2 2π

α

exp

- 0. 5A

2 0

= + ∞

lim

α→1

C′

α

= -

1 - Q

+ A

))

+ A

< 0

}

18

18

)表

,存

α

],使

C′

α

,即

α

α

)的

面说明

α

是极大值点

= Q

α

≤0. 5

,得到

+ A

α ≥0

,代入式(

17

)可

C″

α

< 0

,即

α

)是

,因

α

16

α

)的

α

,算

)初

α

min

= 0

α

max

= 1

,以

δ = 10

- 3

)令

α =

α

min

+ α

max

/ 2

)如

C′

α

≡C′

α

min

),令

α

min

= α

)如

C′

α

≡C′

α

max

),令

α

max

= α

)重

),直

α

max

- α

min

≤δ

)令

α

α

min

+ α

max

/ 2.

+ A

α≥0

α≥

/ A

,因

15

)的

α = max

α

,(

/ A

19

log n

),其

n = 1 / δ.

4 

仿

   

仿

,帧

T = 5 ms

、带

W = 1 kHz

、状

= u

= 0. 5

、噪

σ

= 0 dB

·

mW

SU

功率

p = 10 dB

·

mW

SU

PU

间信道增

- 10 dB

PU

QAM

quadrature amplitude modulation

89

时间频谱感知模型中

SU

干扰概率的比较

,在

,带

PU

,这

SU

PU

,避

PU

SU

,因

PU

            







   

4 

Fig. 4  Interference probabilities of different sensing models

是干

= 0. 20

0. 15

0. 10

0. 05

,对

SU

α

线

,即

α

使

SU

α

,这

α

,低

SU

,而

α

,高

SU

,表

SU

PU

,因

理地选择

,使之在频谱效率和干扰间获得

                             



   



    α

5 

SU

Fig. 5  SU spectrum efficiency comparison with different interference probabilities

SNR

- 4

- 6

- 8

- 10 dB

SU

α

线

,并

SNR

= 0. 02

0. 10

0. 20

,带

型频谱效率的比较

从图

中可以看

,当

= 0. 10

0. 20

,带宽感知能够获得更高

,这

,相

感知的虚警概率更低

,即

SU

的频谱利用率更

;当

= 0. 02

,带

(5)

西

 

 

 

 

 

 

 

50

,是

,两

SU

,而

,可

             



  



  



  



        



   



    α

6 

SNR

SU

Fig. 6  SU spectrum efficiency comparison with different SNRs              



  



  



  



  



  



         



   



     

7 

SU

Fig. 7  SU spectrum efficiency comparison with different sensing models and interference probabilities

,带

SU

频谱效率

= 0. 2

0. 5

0. 6

0. 8

= 0. 8

0. 5

0. 4

0. 2

,根

式(

),相应的

PU

Ω0

= 0. 8

0. 5

0. 4

0. 2.

                                   



  



     

8 

SU

Fig. 8  SU spectrum efficiency comparison with different state transfer rates

,当

= 0. 2

= 0. 8

SU

,此

PU

,因

SU

5 

 

   

CR

,允

SU

使

,其

SU

,相

,带

PU

PU

;当

,带

步将研究基于时间和带宽的二维频谱

  KRENIK W

BATRA A. Cognitive radio techniques for wide area networks

∥Design Automation Conference. Anaheim

IEEE

2005

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brainempowered wireless communications

. IEEE Journal on Selected Areas in Communications

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):

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FRYE J M

PURSLEY M B

et al. Spectrum monitoring during reception in dynamic spectrum access cognitive radio networks

. IEEE Transactions on Communications

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):

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GU Xuemai

et al. Optimal periodic cooperative spectrum sensing based on weight fusion in cognitive radio networks

. Sensors

2013

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):

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,谭

,徐

线

性能的分析[

四川大学学报

:工程科学

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):

168172. LIU Xin

TAN Xuezhi

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. Journal of Sichuan University

Engineering Science Edition

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MONTEIRO E. Cooperative sensing beforetransmit in Adhoc multihop cognitive radio scenarios

∥ International Conference on Wired Wireless Internet Communications. Santorini

Springer Verlag

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,杨

,赵

线

优化[

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EDWARD C Y P

et al. Sensingthroughput tradeoff for cognitive radio networks

. IEEE Transactions on Wireless Communications

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LIANG Y C

GUAN Y L. Optimization of cooperative sensing in cognitive radio networks

a sensingthroughput tradeoff view

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10

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YOO S J. Timeconstrained detection probability and sensing parameter optimization in cognitive radio networks

. Eurasip Journal on Wireless Communications and Networking

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TAN Xuezhi. Optimization for weighed cooperative spectrum sensing in cognitive radio network

. Applied Computational Electromagnetics Society Journal

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12

  PEH E C Y

LIANG Y C

GUAN Y L

et al. Cooperative spectrum sensing in cognitive radio networks with weighted decision fusion schemes

. IEEE Transactions on Wireless Communications

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13

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JEON W S

JEONG D G. Adaptive and distributed access to spectrum holes in cognitive radio system

. Wireless Personal Communications

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DJOUADI S M

LI H. State estimation over a semiMarkov model based cognitive radio system

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POOR H V. Optimal multiband joint detection for spectrum sensing in cognitive radio networks

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(中

:唐

 

   

:周

 



《西南交通大学学报》创刊

60

周年

    2014

12

22

,在西南交通大学九里校区镜湖宾馆多功能厅隆重举行了《西南交通大学学报

(以

《学

》)创

60

《学

》是

,从

1954

60

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49

200

,刊

4000

,已

,特

、交

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,生

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《学

》得

,被

《工

》(

Ei Compendex

)、中

、中国科学引文数据库来源期刊(

CSCD

)、中国科技论文统计源期刊(科技核心期刊)、英国

INSPEC

、德

数学文摘(

Zentralblatt MATH

)、美国《剑桥科学文摘》(

CSA

)、日本科学技术社数据

Bibliographic Databases

)、波

Index Copernius

)、台

《学

》的

,核

、核

2011

卷中

,《学报》的复合影响因子(

UJIF

)名列

430

种综合性科学技术类期刊之首

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F5000

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