Cognitive radio is able to share the spectrum with primary licensed user,which greatly improves the spectrum efficiency.We study the optimal power allocation for cognitive radio to maximize its ergodic capacity under ...Cognitive radio is able to share the spectrum with primary licensed user,which greatly improves the spectrum efficiency.We study the optimal power allocation for cognitive radio to maximize its ergodic capacity under interference outage constraint.An optimal power allocation scheme for the secondary user with complete channel state information is proposed and its approxi-mation is presented in closed form in Rayleigh fading channels.When the complete channel state in-formation is not available,a more practical transmitter-side joint access ratio and transmit power constraint is proposed.The new constraint guarantees the same impact on interference outage prob-ability at primary user receiver.Both the optimal power allocation and transmit rate under the new constraint are presented in closed form.Simulation results evaluate the performance of proposed power allocation schemes and verify our analysis.展开更多
This paper presents an approximate expression to transmission capacity of ad hoc networks by using stochastic geometry. For there is no general close-form expression to the transmission capacity of ad hoc networks, by...This paper presents an approximate expression to transmission capacity of ad hoc networks by using stochastic geometry. For there is no general close-form expression to the transmission capacity of ad hoc networks, by using Taylor series, we obtain the exact series expression to transmission capacity first, then we take partial summation to yield an n-th order approximate expression. Further- more, compared with the exact expression under a special case, the accuracy of the n-th order ap- proximation has been studied. The numerical results show that the accuracy of the approximation is mainly determined by the order n, and a high accuracy can be obtained when the node density or the outage constraint is close to zero .展开更多
基金Supported by the National Natural Science Foundation of China (No. 60972008)
文摘Cognitive radio is able to share the spectrum with primary licensed user,which greatly improves the spectrum efficiency.We study the optimal power allocation for cognitive radio to maximize its ergodic capacity under interference outage constraint.An optimal power allocation scheme for the secondary user with complete channel state information is proposed and its approxi-mation is presented in closed form in Rayleigh fading channels.When the complete channel state in-formation is not available,a more practical transmitter-side joint access ratio and transmit power constraint is proposed.The new constraint guarantees the same impact on interference outage prob-ability at primary user receiver.Both the optimal power allocation and transmit rate under the new constraint are presented in closed form.Simulation results evaluate the performance of proposed power allocation schemes and verify our analysis.
文摘This paper presents an approximate expression to transmission capacity of ad hoc networks by using stochastic geometry. For there is no general close-form expression to the transmission capacity of ad hoc networks, by using Taylor series, we obtain the exact series expression to transmission capacity first, then we take partial summation to yield an n-th order approximate expression. Further- more, compared with the exact expression under a special case, the accuracy of the n-th order ap- proximation has been studied. The numerical results show that the accuracy of the approximation is mainly determined by the order n, and a high accuracy can be obtained when the node density or the outage constraint is close to zero .
