In this work, a directional modulation-based technique is devised to enhance the security of a multi-antenna wireless communication system employing M-PSK modulation to convey information. The directional modulation method operates by steering the array beam in such a way that the phase of the received signal at the receiver matches that of the intended M-PSK symbol. Due to the difference between the channels of the legitimate receiver and the eavesdropper, the signals received by the eavesdropper generally encompass a phase component different than the actual symbols. As a result, the transceiver which employs directional modulation can impose a high symbol error rate on the eavesdropper without requiring to know the eavesdropper's channel. The optimal directional modulation beamformer is designed to minimize the consumed power subject to satisfying a specific resulting phase and minimal signal amplitude at each antenna of the legitimate receiver. The simulation results show that the directional modulation results in a much higher symbol error rate at the eavesdropper compared to the conventional benchmark scheme, i.e., zero-forcing precoding at the transmitter.
In this work, a directional modulation-based technique is devised to enhance the security of a multi-antenna wireless communication system employing M-PSK modulation to convey information. The directional modulation method operates by steering the array beam in such a way that the phase of the received signal at the receiver matches that of the intended M-PSK symbol. Due to the difference between the channels of the legitimate receiver and the eavesdropper, the signals received by the eavesdropper generally encompass a phase component different than the actual symbols. As a result, the transceiver which employs directional modulation can impose a high symbol error rate on the eavesdropper without requiring to know the eavesdropper's channel. The optimal directional modulation beamformer is designed to minimize the consumed power subject to satisfying a specific resulting phase and minimal signal amplitude at each antenna of the legitimate receiver. The simulation results show that the directional modulation results in a much higher symbol error rate at the eavesdropper compared to the conventional benchmark scheme, i.e., zero-forcing precoding at the transmitter.
In this work, a directional modulation-based technique is devised to enhance the security of a multi-antenna wireless communication system employing M-PSK modulation to convey information. The directional modulation method operates by steering the array beam in such a way that the phase of the received signal at the receiver matches that of the intended M-PSK symbol. Due to the difference between the channels of the legitimate receiver and the eavesdropper, the signals received by the eavesdropper generally encompass a phase component different than the actual symbols. As a result, the transceiver which employs directional modulation can impose a high symbol error rate on the eavesdropper without requiring to know the eavesdropper's channel. The optimal directional modulation beamformer is designed to minimize the consumed power subject to satisfying a specific resulting phase and minimal signal amplitude at each antenna of the legitimate receiver. The simulation results show that the directional modulation results in a much higher symbol error rate at the eavesdropper compared to the conventional benchmark scheme, i.e., zero-forcing precoding at the transmitter.
In this paper, we consider a physical layer security (PLS) problem for a hybrid wiretapping wireless system in millimeter-wave transmission, where the active eavesdropper and passive eavesdropper (Eve) may coexist to intercept the confidential messages and emit jamming signals. To achieve secure and reliable transmission, we propose a switched phased-array directional modulation (DM) scheme that employs multi-beam symbol-level precoding with aided artificial noise (AN) technique at the transmitter, and array reception at legitimate users (LU). Here we consider a more practical case that the information of the eavesdropper (Eve) is unknown by the transmitter. Leveraging DM beamforming, we aim to minimize transmit message power by optimizing the beamforming vector, subject to prescribed symbol-level constraints, thus generating exact/relaxed phases at LU. The remaining transmit power can be utilized to generate AN. Additionally, by means of the minimum variance distortionless response method at the LU, the jamming caused by active Eve can be efficiently eliminated. Simulation results demonstrate the superiority of the proposed scheme.
This paper introduces a multi-beam secure communication scheme for hybrid near-field and far-field (hNF) scenarios, primarily designed to address the challenges faced by sixth-generation (6G) networks in simultaneously managing near-field and far-field communications. This method significantly reduces the signal quality at eavesdroppers(Eves) while ensuring high-quality reception for legitimate users, effectively enhancing communication security. At the transmitter, this study employs multi-beam symbol-level directional modulation to ensure secure and reliable transmission in a mixed eavesdropping environment. Given the uncertainty about eavesdropper information, the transmission beamforming vectors are specially designed to meet specific symbol-level constraints, thereby ensuring effective reception for legitimate users. Experimental and simulation results demonstrate the effectiveness of our approach in improving secrecy performance, reducing transmission power, and enhancing energy efficiency, offering a practical solution to the security challenges faced by future wireless networks.
Wireless communication security can be enhanced by leveraging the characteristics of the physical (PHY) layer, where discriminatory scrambling can be employed at the symbol level to either improve the signal quality of the legitimate receiver or degrade that of the eavesdroppers. However, in the presence of multiple passive eavesdroppers with more antennas than the transmitter, the transmitted signals can still be reliably separated from random disturbances. To mitigate this challenge, we propose a two-dimensional vectorized secure transmission scheme. Unlike existing transmission schemes (where the same data symbol is sent over each antenna with a predesigned complex weight at a time), in the proposed scheme, a sequence of data symbols in a predefined order (named symbol vector) is first pre-superposed through pre-coding with a random complex matrix prior to been sent as a vector in parallel over each transmitting antenna at a time. As a result, physical randomness of the legitimate channel is introduced into the received signals at passive eavesdroppers in the pre-coding procedure. Moreover, to ensure that transmitted data symbols can be recovered in the right order, each symbol vector is sent repeatedly, according to the principle of maximum entropy. To ensure the intended receiver can recover the transmitted symbol vector, the random pre-coding matrices are selected such that a linear constraint imposed by the CSI of the legitimate channel is satisfied. In addition, an extended maximum likelihood (ML) detection method is developed for the desired receiver while the random pre-coding matrices are not required to be transmitted. We then analyze its security based on the signal detection theory to demonstrate that the intended receiver can recover the transmitted symbol vectors while the eavesdroppers are not capable of doing so. We also evaluate the performance of the proposed scheme to demonstrate its effectiveness.
In this paper, directional modulation (DM) is investigated to enhance physical layer security. Practical transmitter designs are exploited under imperfect channel state information (CSI) and hardware constraints, such as finite-resolution phase shifters (PSs) and per-antenna power budget. Tailored for the practical issues in realizing DM, a series of practical scenarios are investigated. Starting from the scenario where eavesdroppers (Eve)s' information is completely unknown, corresponding designs are proposed to optimize legitimate users (LU)s' receiving performance while randomizing the Eves' received signal. When the Eves' CSI is imperfectly known, in the second scenario, the Eves' receiving performance is further deteriorated by imposing destructive interference to the Eves. For each scenario, three algorithms are proposed under hardware constraints and imperfect CSI, i.e., one direct-mapping algorithm suitable for high/moderate number of bits in PSs, one heuristic algorithm with improved receiving performance at the cost of complexity, and one iterative-closed-form algorithm with enhanced practicality of symbol-level based DM. Simulation demonstrates that the algorithms achieve lower symbol error rate (SER) at the LUs while significantly deteriorating the Eves' SER, leading to an improved secrecy throughput over the benchmarks.
The paper proposes a novel approach for securing the wireless communication by designing the signal in a way that makes its modulation format direction-dependent. The idea is to exploit the multi antennas at the transmitter to superimpose a space-time varying interfering component (at the modulation rate) while staying orthogonal to the desired receiver's direction. Unlike conventional interference or artificial noise injection techniques, the proposed approach impedes an arbitrary eavesdropper from blindly separating the information data symbols from the injected interference due to its space-time varying nature.