This paper proposes a robust, energy-efficient multi-user OFDM chaotic vector cyclic shift keying (MU-OFDM-CVCSK) system for channels impaired by multi-user interference (MUI), Gaussian, and impulsive noise. The system’s co-designed transceiver uses cyclic shifts of a single reference signal for energy efficiency, while a novel receiver combines low-rank matrix factorization with a truncated-quadratic loss function to suppress both MUI and noise. In particular, the transmitted signal’s cyclical structure enables iterative reference refinement, further enhancing performance. We provide a comprehensive analysis of the algorithm’s convergence, complexity, energy efficiency, power spectral density, peak-to-average power ratio, and derive the bit error rate (BER) expressions. Simulations demonstrate superior BER performance compared to benchmark schemes in challenging interference and noise conditions.

In traditional multi-user orthogonal frequency division multiplexing differential chaos shift keying (MU-OFDM-DCSK) systems, the noisy correlation of reference signals with overlapped information-bearing signals from multiple users degrades the bit error rate (BER). This paper devises a MU-OFDM-DCSK receiver that enhances the BER performance for uplink transmission. In our design, the challenges of reducing multi-user interferences (MUIs) and noise in both reference and information-bearing chaotic signals are addressed via leveraging the low-rank structure of the received signal matrix. By exploiting low-rank matrix factorization, a novel objective function is constructed. Minimization of this function, which corresponds to a least squares optimization, can effectively decode the transmitted data bits, even in the presence of additive white Gaussian noise (AWGN) and MUIs. The BER of our scheme is analyzed and verified in both AWGN and multipath Rayleigh fading channels. Theoretical developments including uniqueness of matrix factorization and algorithm convergence as well as complexity, are also provided. Simulation results demonstrate that our designed receiver yields smaller BER than benchmark schemes.

In this paper, we propose a novel dual index pulse position modulation differential chaotic shift keying (DI-PPM-DCSK) system for wireless covert communication. Unlike conventional PPM schemes, at the transmitter, we propose to modulate index bits with the positions of both the reference and information-bearing signals, thereby incorporating more index bits into each symbol. Thus both energy efficiency and data rate can be improved. Besides, the information-bearing modulated signals are hidden with the artificial noise to enhance the covertness of communications. At the receiver, we propose to demodulate the information bits by calculating the coherence of adjacent symbols. Moreover, we derive analytical expressions for the bit error rate (BER) and covert performance of the system, which are validated through numerical simulations. The results demonstrate that the proposed system achieves superior data rate and BER performance compared to existing counterparts over fading channels. Furthermore, the covertness is validated with both theoretical analysis and simulation results.

Traditional device-to-device (D2D) communication improves the power consumption, communication delay and resource efficiency, but limited to communication range of devices. To this end, this paper proposes a novel UE-specific reconfigurable intelligent surface (RIS) aided D2D relay communication approach to enhance the network capacity by exploring the degrees of freedom of time, space and reuse mode. The capacity enhancement problem is formulated to maximize the overall spectral efficiency of cellular users (CUs) and D2D users (DUs) to find out the optimal reuse partners i.e., CUs and power control with a decoupling algorithm. Simulation results show that the proposed approach significantly improves the access rate and increases the total spectrum efficiency by 45.6% compared with the direct D2D communication, and outperforms traditional D2D relay scheme in terms of higher 35.2% total spectrum efficiency and less 29.3% power consumption.

Self-Organizing Network (SON) is a promising and enabling technology for network automation that is an important component of 6G native-intelligence. Coverage and Capacity Optimization (CCO) is one of key use cases to self-optimize users’ experience. However, the temporal granularity of CCO as a network-level optimization is comparatively larger when contrasted with that of Radio Resource Management (RRM). Moreover, the Key Performance Indicators (KPIs) and Network Configuration Parameters (NCPs) to be adjusted may overlap between both optimization techniques. To further mitigate Operation, Administration, and Maintenance (OAM) cost and address conflicts arising from different optimization techniques, this study initially presents a framework for SON-RRM intelligent optimization. Subsequently, a cross-layer Deep Reinforcement Learning approach (cl-DQN) is proposed to address the challenge of delineating the optimization tasks of SON-RRM with different temporal granularities, taking CCO as an use case. The simulation results demonstrate that the proposed cl-DQN based CCO-RRM intelligent optimization approach outperforms traditional CCO, with 6% capacity as well as 4% coverage & capacity improvements respectively. Additionally, it reduces the OAM cost stemming from antenna parameter adjustments, with a maximum reduction of 93%.

In order to meet increasing demands of higher energy efficiency and better reliability performance for the multiuser Internet of things (IoT) secure communications, in this paper, we design a reliable and energy efficient superposition modulation (SM) and singular value decomposition (SVD) detection based multi-user orthogonal frequency division modulation-based differential chaos shift keying (SM-MU-OFDM-DCSK) transceiver for IoT devices. At the transmitter, we propose to superimpose and overlap the information-bearing chaotic signals for higher energy efficiency. Since the chaotic modulated signals of each user share identical reference chaotic signals, the transmitted superimposed signal matrices have the low-rank property. Then at the receiver, we apply the SVD-aided detection to recover these low-rank signals, which can suppress the noise to attain better reliability performance. Moreover, we prove that the proposed design can achieve the maximum likelihood detection performances. Furthermore, we derive the theoretical bit rate, energy efficiency and bit error rate expressions over additive white Gaussian noise (AWGN) channel. Simulation results are then provided to validate the theoretical derivations. Subsequently, the simulated performances over AWGN and fading channels are investigated to show that higher energy efficiency and better reliability performances than benchmark schemes can be achieved in industrial IoT scenarios.

Radio frequency watermarking systems embed the secret watermark bits into host bits for secure transmissions. However, malicious users may initiate falsifying attacks via broadcasting wireless channels. Meanwhile, the interferences of watermark signals to host signals will degrade the bit error rate (BER) performances. With the aim to enhance both the security and the reliability performances, we propose to utilize the Hash function to generate the unique digital digest of host signals for the integrity check. Then the lightweight encryption and spreading are conducted to compose the watermark signals. At the receiver, reverse operations are performed to recover both host signals and watermark signals. Then the retrieved digest is used to check the integrity and validity of host signals to combat falsifying attacks. Subsequently, we derive the bit error rate (BER) and the information leakage expressions. Simulation results are then provided to validate the proposed design.

In this paper, we design a novel orthogonal time frequency space modulation based differential chaos shift keying (OTFS-DCSK) transceiver for reliable information transmissions. In this design, we exploit the orthogonal time frequency space (OTFS) modulation which is a two-dimensional modulation designed in the delay-Doppler domain, to combat multiplicative channel fading. Besides, since the OTFS-DCSK signal matrix is rank-1, we propose to utilize a singular vector decomposition (SVD) aided detection at the receiver to suppress the additive white Gaussian noise (AWGN) to further enhance the reliability. Thanks to the diversity obtained from OTFS modulation and the noise-suppression achieved by the SVD aided detection, the proposed OTFS-DCSK transceiver significantly improves the reliability performance, particular in the high-mobility wireless communications over the dual-dispersive channels caused by multipath propagation effects and Doppler shift effects. Simulation results validate the proposed OTFS-DCSK system outperforms the benchmark systems over AWGN, multipath and dual-dispersive fading channels.

In this paper, we devise a sparse-coded orthogonal frequency division multiplexing (OFDM) differential chaos shift keying (DCSK) communication system based on low-rank matrix recovery which can handle Gaussian background noise and outlier-contaminated symbols simultaneously. As the noise-free OFDM-DCSK symbol matrix has rank 1, we exploit the vector outer product for its modeling, while sparse coding is also applied to reduce the transmission energy. To demodulate information bits from the sparse-coded signal, we formulate an objective function which consists of a sum of Frobenius norm for rank-1 matrix recovery and$\ell _{0}$-norm for identifying the possibly outlier-contaminated symbols, with a self-adaptive weight parameter. The resultant optimization problem is solved iteratively via block coordinate descent, and the Laplacian kernel with the Silverman’s rule is adopted for outlier detection. Theoretical analysis including convergence of the objective function, bit error rate (BER), energy efficiency and computational complexity, are provided. Simulation results show that the proposed system has comparable mean square error and BER performance with the$\ell _{p}$-norm minimization based matrix recovery approach at$p=2$in additive white Gaussian noise, and is superior to that of$p=1$in Middleton class A noise, even when sparse coding is applied. Moreover, compared with other binary DCSK systems, our system achieves higher energy efficiency thanks to the sparse coding.

With the increasing diversity of mobile apps, users install many apps in their smartphones and often use several apps together to meet a specific requirement. Because of the evolution of user habits and app functions, the set of apps using at the same time, i.e., app usage context, may change over time, which represents the dynamic correlation of different apps and even the evolution trend of the whole app ecosystem. Therefore, understanding how an apps usage context changes over time is very meaningful. In this paper, based on a seven-year app usage dataset, we explore the long-term app usage context dynamics and understand the underlying reasons and influence factors behind. Specifically, we build app co-occurrence graphs in different periods and learn app embeddings accordingly by leveraging graph embedding algorithm. We then measure the change of app usage context by the distance between neighboring app embeddings. As for the whole app ecosystem, we find that the change rate of app usage context undergoes up and down phrases, and varies in different app-categories. Furthermore, we explore three influence factors correlated with such dynamics. These results will be helpful for stakeholders to better understand the evolution of mobile users app usage behavior.

The noises embedded in signals will degrade the signal processing quality. Traditional denoising algorithms might not work in practical systems since the statistical characteristics of noises might not be learned. To address this issue, we propose an efficient residual shrinkage convolutional neural network (RSCNN) aided denoiser based on the principle of the domain transformation, shrinking and inverse transforming operations conducted by the traditional denoiser. The proposed RSCNN is composed by the batch normalization layer, domain transformation layers, the shrinkage module and inverse transformation layers, wherein transformation layers consist of convolutional layers and the nonlinear activation function. Moreover, we propose a thresholds learning subnetwork to automatically determine the thresholds, so as to enhance noise suppressing performances. Furthermore, we compose the data set by preprocessing the received signals, and design the loss function according to different denoising requirements. To validate the efficiency and universality of the RSCNN aided denoiser, we apply the proposed RSCNN denoiser to three different application scenarios, including the modulation recognition, detection and decoding. After the offline training, at the online deployment stage, we utilize the RSCNN denoiser to reduce the noise power and improve the signal to noise ratios. Simulation results demonstrate that the proposed intelligent denoiser can efficiently improve the signal processing capabilities to achieve higher modulation recognition accuracy, better detection and decoding performances with lower complexity than benchmark schemes.

Downlink mobile edge computing (MEC) networks are requiblack to serve increasing large number of Internet of Things (IoT) devices with limited battery capacity. In order to serve massive user equipments with low power consumption requirements, in this paper, we propose an energy-efficient multi-carrier non-orthogonal multiple access (MC-NOMA) design which allows more than two IoT devices to multiplex and access the same subcarrier band. With the aim to minimize the total transmit energy while meeting the demands of each IoT device such as the low latency, in our design, we first derive the optimal successive interference cancellation (SIC) policy and minimum power allocated to every IoT device. Then we propose an optimal greedy algorithm to allocate the frequency blocks, and formulate the optimization of the computational resource allocation as a min-max problem. Subsequently, we characterize the MC-NOMA network with the potential game model, and present a scheduling scheme to manage massive IoT devices. Simulation results demonstrate that our proposed scheme can consume 3-10 dB less energy in a MEC network deployed with 256 IoT devices compablack with the conventional orthogonal multiple access (OMA) scheme and non-orthogonal multiple access (NOMA) scheme.

In this paper, we propose a pre-coded multi-carrier$M$-ary chaotic vector cyclic shift keying (PC-MC-$M$-CVCSK) transceiver for reliable information transmissions. In this design, we exploit the principle of diagonalization to combat noises and interferences. At the PC-MC-$M$-CVCSK transmitter, we propose to precode the$M$-ary modulated symbols based on the discrete Fourier transform (DFT) and the reverse matrix of an eigenvalue matrix. Meanwhile, the chaotic generator outputs chaotic sequences, which are then cyclically shifted and used to modulate precoded symbols. At the receiver, reverse operations are conducted to recover the data. Moreover, we prove that a circulant matrix can be constructed by selecting the cyclic shift length, while the DFT aided processing will diagonalize the circulant matrix. Thanks to the diagonalization design, the inner product of information-bearing chaotic vectors becomes zero, thus signals can be orthogonalized to suppress interferences. Furthermore, theoretical performances of the proposed transceiver, including the bit error rate (BER), the symbol rate, the energy efficiency and the spectrum efficiency, and the computational complexity are analyzed. Simulation results validate the exact analysis. Furthermore, the results demonstrate that the proposed PC-MC-$M$-CVCSK system outperforms the counterpart schemes, which can provide$M$-ary high symbol rate transmission services with enhanced reliability performances.

In this paper, we propose a Sparse Code Spreading-aided Multi-Carrier Differential Chaos Shift Keying (SCS-MC-DCSK) transceiver to improve the efficiency and reliability performances for multiuser transmissions. With the aim to improve the spectrum efficiency and enhance the reliability, we construct a multi-dimension codebook based on a factor graph matrix to spread information bits in a non orthogonal way, thus the signals could overlap and multiple users are allowed to share all sub-carrier resources via the non orthogonal spreading. The information bits using the same codebook are regarded as a layer, while each user could choose to use one or multiple layers. Then the resultant symbols are spread by the reference chaotic sequence and its quadrature version generated by Hilbert transform in the time domain. At the receiver, reverse operations are conducted, and we propose the Minimum Distance (MD) detection method to retrieve the estimates. Furthermore, theoretical performances, including the Symbol Error Rate (SER), capacity, energy efficiency, spectrum efficiency and computational complexity, are analyzed and compared among the proposed design and benchmarks. Simulation results are then provided to validate the theoretical analysis. Moreover, the Bit Error Rate (BER) performances under different channel conditions demonstrate the superior reliability and efficiency to benchmarks.

Narrow band Internet of Things (NB-IoT) systems support massive devices to connect with the wide area network with the low energy consumption. However, due to the broadcasting property and variant conditions of wireless channels, both the security and the reliability performances are required to be improved for NB-IoT terminals. In this paper, we propose a multidimensional orthogonal code (MOC) aided radio frequency (RF) watermark scheme to enhance both the security and the reliability performances. In our design, we exploit the repeat transmission mechanism in NB-IoT systems, and propose to use the repeated signal as the host signal to carry multiple low-power watermark signals, wherein different orthogonal codewords are utilized as the embedding coefficients to hide the host signals. Thanks to the orthogonality of MOC watermarks, the mutual interferences among the transmitted signals can be effectively suppressed, thus the reliability performances could be improved. Furthermore, we derive the theoretical bit error rate (BER) and analyze the efficiency as well as the covertness. Simulation results validate the theoretical analysis. Moreover the results demonstrate that using the proposed MOC aided RF watermark design, NB-IoT systems can achieve better reliability and covertness performances as well as higher security performances than counterpart schemes.

In this paper, we propose a novel two-dimensional frequency and time diversity aided orthogonal frequency division multiplexing based differential chaos shift keying (OFDM-DCSK) system. Our aim is to provide secure and robust transmissions for practical wireless systems, where perfect channel state information (CSI) may not be available at the receiver, by exploiting the natural high security of chaotic sequences and frequency diversity gains brought by the frequency hopping (FH). In our design, the information bits are firstly modulated by chaotic chips, then non-repetitive FH operations are performed on both reference chips and chaotic modulated symbols. After the inverse fast Fourier transform (IFFT), the non-repetitive reference chips and chaotic modulated symbols are respectively transmitted over different subcarriers. Subsequently, the receiver recovers the information using the received reference chaotic chips which naturally embed the channel frequency response (CFR) of all subcarriers. We then analyze the energy and spectral efficiencies, derive the bit error rate (BER) and information leakage expressions, and provide a detailed complexity analysis of the proposed scheme. Simulation results verify the effectiveness of our derivations and demonstrate that the proposed system achieves better BER and security performances compared with the benchmark system, especially when the CSI is imperfect or unknown.

In this paper, we present a frequency hopping (FH) orthogonal frequency division multiplexing-aided differential chaos shift keying (OFDM-DCSK) modulation system for cognitive radio (CR) systems operating over non contiguous bands. Our aim is to provide reliable transmissions for CR transceivers which may hardly get the exact and perfect channel state information (CSI). In our design, we utilize the natural high security of chaotic sequences and the frequency diversity brought by the FH. The information bits are firstly modulated by chaotic chips, then both reference chips and chaotic modulated symbols are carried out FH operations and hopped non-repetitively. After performing the inverse fast Fourier transform (IFFT) over available non-contiguous spectrum bands, the resultant OFDM symbols are transmitted and the non-repetitive reference chips are respectively transmitted over different subcarriers. Subsequently, the receiver would retrieve the information using the received reference chaotic chips which naturally embed the channel frequency response (CFR) of all subcarriers. The bit error rate (BER) expressions are derived and simulations results verify the effectiveness of our derivations, which demonstrate that the presented system can achieve better BER than counterpart systems, especially when the CSI is not exact or unknown.

In this paper, we proposed a novel carrier interferometry (CI) code index modulation aided orthogonal frequency division multiplex (OFDM) differential chaotic shift keying (DCSK) communication system. In our design, we utilize the orthogonality property of CI codes matrix, and propose to transmit more information bits using the index of the CI codes matrix. The input information stream is divided into two subsets. One subset is modulated by the chaotic sequence and then spread by the information-bearing CI codes matrix which carries another information subset. At the receiver, the non-coherent chaotic demodulation and the maximum likelihood detection are respectively performed on these two subsets to retrieve the information. Since more bits can be transmitted while not requiring extra chaotic sequences and remaining the same overall energy, the energy efficiency is improved. Additionally, thanks to the spreading in the frequency domain achieved by the usage of CI codes, the peak to average power ratio (PAPR) can be suppressed. Moreover, theoretical performances including the energy efficiency, the bit error rate (BER) expressions are analyzed. Simulation results are provided to validate the theoretical analysis, and demonstrate the satisfactory PAPR and BER performances achieved by our design.

In this paper, we present a general iterative receiver for multi-carrier differential chaos shift keying (MC-DCSK) systems. The imperfect channels conditions may induce transmission errors which will degrade the reliability performances. In order to address this issue, we propose an iterative demodulation structure to improve bit error rate (BER) performances by improving the signal to noise ratio (SNR) of reference chaotic signals. At the presented iterative receiver, we propose to evaluate correlation coefficients between the reference chaotic signals and each information-bearing chaotic modulated signal. Then they are used to update and feedback the reference chaotic signal for the next iteration. With the aid of the renewed reference signals, a similar procedure is carried out until the iteration stopping criteria is reached and the threshold decisions are provided. The presented general iterative receiver can be applied to any MC-DCSK systems without introducing any additional modules at transmitters. Theoretical analysis is provided to prove the iteration convergence and to derive the BER performances. Simulation results verify the effectiveness of the theoretical analysis, which demonstrates that better reliability performances can be achieved over additive white Gaussian noise (AWGN) and fading channels compared with counterpart systems.

In this paper, we present a novel noise resistent diagonal iteration-based carrier interferometry (DICI) codes for spreading optical orthogonal frequency-division multiplexing (OOFDM) symbols, and thereby suppressing the peak to average power ratio (PAPR) for high data rate OOFDM based systems. Considering that the high date rate transmission requires the subcarrier number to be large, and that the large subcarrier number may induce smaller intervals between the symbols and higher PAPR and thus leading to the performance degradation, we propose to use DICI codes to enlarge the intervals and suppress the noises including the signal- dependent noises in intensity modulated system and the phase noises in coherent modulated systems to improve the performances. More explicitly, we perform the diagonal iteration on the carrier interferometry (CI) codes by calculating the Kronecker product of identity matrix and CI code matrix, thus the matrix extension is achieved by the DICI codes. Moreover, we prove that the presented DICI codes are orthogonal and invertible. Simulations are performed and the results demonstrate the outstanding bit error rate (BER) and PAPR performances of the proposed DICI-aided spreading OOFDM systems.

In this paper, we propose a noise suppressing chaos generator to improve the bit error rate (BER) performances for the high-order differential chaos shift keying (DCSK) systems. The presented chaos generator outputs the overlapping chaotic sequences for the information modulation, which use a buffer for temporary storage, and the stored chaotic sequence is used to modulate the information bit while the second element of the chaotic sequence is fed back to serve as the initial value to generate chaotic sequence for the modulation of the next information bit. Namely, the different information bit may share the same chaotic segments of the whole chaotic sequence. Thus, the repetitive transmission of the same reference chaotic segments suppress the channel noise, and the BER performance of high-order DCSK systems are improved. We derive the theoretical BER expression for the proposed scheme over additive white Gaussian noise (AWGN) channel. The simulation results match the theoretical BER, and demonstrate that the BER performances have been improved with the use of noise-suppressing chaos generator.

In visible light communication (VLC) system, the color shift keying (CSK) modulation scheme has been employed and combined with orthogonal frequency division multiplexing (OFDM) to improve the spectrum efficiency. However, the traditional fast Fourier transform (FFT) based OFDM module requires the CSK symbols to be Hermitian symmetric, which induces the waste of the bandwidth. In this paper, we propose a real-Fourier domain-based CSK OFDM scheme using the discrete Hartley transform (DHT), which is capable of transforming the real-valued signal to a real-valued signal and removes the requirement of Hermitian symmetry. Hence the spectrum utilization is approximated doubled thanks to removal of the requirement of Hermitian symmetry in conventional FFT-based OFDM systems. Moreover, the theoretical symbol error rate (SER) is evaluated for the asymmetrically-clipped optical OFDM (ACO-OFDM) and the DC-biased optical OFDM (DCO-OFDM) with CSK scheme. We then simulate the performance of CSK modulated DHT- based OFDM system, and the results show that the presented DHT-CSK-OFDM system can provide higher spectral efficiency while maintaining the same error performance as compared with the counterpart FFT-based OFDM systems.

In this paper, we present a new equalizer based on probabilistic neural networks (PNN) for visible light communication (VLC) systems. While traditional artificial neural networks (ANN) type equalizers have to identify the distribution of the received signal, in our method kernel density estimation (KDE) is exploited to obtain the probability density function (PDF) of the states of the received signal, which reduces the computational complexity, especially when severe inter symbol interference (ISI) exists and when the number of signal states in the observation space increases. Then the constructed PDF is used to find the optimal Bayes solution at the receiver. Moreover, the decision feedback (DF) mechanism is utilized for further performance enhancements. The simulated bit error rate (BER) performances of the presented PNN based equalizers are compared with linear equalizer (LE) and conventional decision feedback equalizer (DFE). Simulation results demonstrate that the PNN-based equalizer without and with DF outperform LE and conventional DFE, respectively, thanks to the employment of KDE.

FD-MC-CDMA is an attractive frequency domain CDMA system that provides high performance in multi-path fading channels by exploiting both diversity gain and multi-user detection (MUD) gain. In FD-MC-CDMA, by decomposing the entire subcarrier set into multiple non-contiguous subcarrier sets, the number of interfering users within each subcarrier set is significantly reduced. As a direct result, an optimal maximum likelihood MUD receiver can be implemented at low complexity. In this paper, we first revisit previously developed phase rotation spreading code design to bring signal space diversity to conventional MC-CDMA systems. Similarly, due to the binary nature of the spreading codes, full diversity is not always exploited in FD-MC-CDMA system. Then we combine the phase rotated spreading code design scheme with FD-MC-CDMA system to exploit full diversity. With the phase rotated spreading codes and the exploitation of full diversity, the new FD-MC-CDMA system offers significant performance enhancement compared with the original FD-MC-CDMA system along with conventional MC-CDMA system. Simulation results over multi-path fading channels confirm the performance gain of the proposed scheme.

Visible light communication (VLC) networks can provide high‐rate transmissions with advantages such as high security, low power consumption and so on. Multiple users get access to the VLC network according to the carrier sense multiple access with collision avoidance (CSMA/CA) mechanism defined by IEEE 802.15.7 media access control layer specifications. In this study, the authors propose an energy efficient medium access scheme to improve the performance of IEEE 802.15.7 CSMA/CA mechanism under unsaturated traffic conditions. Aiming at reducing the power consumed on unnecessary waiting and at improving the channel utilisation efficiency, they first apply a successive transmission scheme on the node, which has completed one successful transmission and gets the chance of transmitting the next packet without backoff delay period according to the network condition. Then, a dynamic contention window is exploited to mitigate the collisions, where they derive the optimal minimum contention window based on throughput analysis. The power consumption can be reduced with improved throughput, when both the traffic load and the number of nodes in the network are taken into account. Simulation results demonstrate that the authors’ proposed scheme outperforms the IEEE 802.15.7 CSMA/CA scheme with respect to the average power consumption, system throughput and packet dropping probability.

In this paper, we apply advanced encryption standard (AES) to improve the security of chaotic cognitive radio (CCR) system. More specifically, we propose to encrypt the information with AES, then the AES-encrypted information is modulated by frequency domain based chaos sequences and transmitted over the non continuous subcarriers sensed by the CCR. Both the transmitter and the receiver share the secret of AES encryption, while the eavesdroppers could not retrieve the information without any information of the secret. The simulation results verify that the AES-assisted CCR system offers a high security. The information effectively hides and the power spectral density of the `Lena' image is smoothed with AES encryption. Furthermore, the bit error rate analysis demonstrate that the malicious users can not retrieve the original information due to the high bit error rate without AES secret key.