指導老師 :王瑞騰 老師學生 :盧俊傑

On Cognitive Radio Networks with Opportunistic Power Control Strategies in Fading ChannelsIEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 7, NO. 7, JULY 2008

Outline INTRODUCTION SYSTEM MODEL OPPORTUNISTIC POWER CONTROL STRATEGY THE IMPACT OF IMPERFECT CHANNEL ESTIMATION NUMERICAL RESULTS CONCLUSION

INTRODUCTION we consider a cognitive radio system in

fading wireless channels and propose an opportunistic power control strategy for the cognitive users.

The achievable rate of a cognitive user under the proposed power control strategy is analyzed and simulated, taking into account the impact of imperfect channel estimation.

SYSTEM MODEL1) Self-goal: Trying to transmit as much information forhimself as possible.2) Moral-goal: Maintaining the primary user’s outage probabilityunaffected.

: white Gaussian noise

: white Gaussian noise

: Rayleigh fading

: Rayleigh fading

: Rayleigh fading

: Rayleigh fading

f

g

PX

CX

PZ

CZ

PY

CY

Primary transmitter

Cognitive transmitter

Primary receiver

Cognitive receiver

f

g

PX

CX

PZ

CZ

PY

CY

Primary transmitter

Cognitive transmitter

Primary receiver

Cognitive receiver

OPPORTUNISTIC POWER CONTROL STRATEGY

1

0

-b

1

0

-b

THE IMPACT OF IMPERFECT CHANNEL ESTIMATION

1

0

-b

1

0

-b

1

0

-b

1

0

-b

NUMERICAL RESULTSThe maximum transmit power of the cognitive userThe maximum transmit power of the primary user

CONCLUSION The opportunistic power control strategy for the cognitive user, which has been proved to be optimal in the sense that it maximizes the achievable rate of cognitive user while guaranteeing the outage probability of the primary user not to be degraded.

The simulation results verify its effectiveness in enhancing the robustness of our strategy.