Abstract
In this paper, we consider the physical layer security problem of the wireless communication system. For the multiple-input, multiple-output (MIMO) wireless communication system, secrecy capacity optimization artificial noise (SCO−AN) is introduced and studied. Unlike its traditional counterpart, SCO−AN is an artificial noise located in the range space of the channel state information space and thus results in a significant increase in the secrecy capacity. Due to the limitation of transmission power, making rational use of this power is crucial to effectively increase the secrecy capacity. Hence, in this paper, the objective function of transmission power allocation is constructed. We also consider the imperfect channel estimation in the power allocation problems. In traditional AN research conducted in the past, the expression of the imperfect channel estimation effect was left unknown. Still, the extent to which the channel estimation error impacts the accuracy of secrecy capacity computation is not negligible. We derive the expression of channel estimation error for least square (LS) and minimum mean squared error (MMSE) channel estimation. The objective function for transmission power allocation is non-convex. That is, the traditional gradient method cannot be used to solve this non-convex optimization problem of power allocation. An improved sequence quadratic program (ISQP) is therefore applied to solve this optimization problem. The numerical result shows that the ISQP is better than other algorithms, and the power allocation as derived from ISQP significantly increases secrecy capacity.
Highlights
Secure transmission is a fundamental problem in wireless communications due to the broadcast nature of the wireless medium
The lower bound on secrecy capacity after adding secrecy capacity optimization artificial noise (SCO−artificial noise (AN)) is: g
The results show that the lower bound on secrecy capacity increases with power allocation, implying the high effectiveness of the improved sequence quadratic program (ISQP) algorithm
Summary
Secure transmission is a fundamental problem in wireless communications due to the broadcast nature of the wireless medium. Considering the following cases: the eavesdropper is closer to the transmitter, or the eavesdropper has more antennas than the transmitter These mentioned conditions will make the eavesdropper’s channel better than the legitimate channel and reduces the effectiveness of the physical layer security technology. The secrecy capacity of a wireless communication system using SCO−AN is limited by transmission power Considering this limitation, this paper constructs a power distribution function for SCO−AN and the information-bearing signal. The expression for the channel estimation errors is derived for the first time This expression can be applied to future physical layer security research examining imperfect channel estimation.The power allocation function is converted to a function with only one variable–the. Denotes the mathematical expectation; k · k denotes the norm of a vector; and | · | denotes the determinant of a matrix
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