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This paper proposes a new type of complementary code, i.e., 3-D complementary code (3DCC), which integrates space–time coding and code division multiple access under a unified framework for multiple-input–multiple-output (MIMO) system implementation. Owing to its ideal correlation properties, the 3DCC ensures orthogonal transmissions among users and antennas. Analytical studies given in this paper will show that the proposed 3DCC-MIMO system is able to support both transmit diversity and multiplex at the same time, with its unique agility to switch between them according to different channel environments and system configurations. Additionally, multiuser interference (MUI) is eliminated in a 3DCC-MIMO system for both synchronous and asynchronous transmissions over a flat-fading channel with a relatively low complexity. Simulation results are also provided to verify the correctness of analysis and demonstrate the superiority of the proposed MIMO system in terms of its MUI-free performance. [ABSTRACT FROM PUBLISHER]

Motivated by growing demand for high-speed wireless communications, we proposed to implement code division multiple access systems based on orthogonal complementary codes (OCC-CDMA). While an OCC-CDMA system indeed offers ideal correlation properties, its capacity is strictly constrained by the number of element codes each user may use. In this paper, we suggest to use in-phase/quadrature (I/Q) column-wise complementary (IQCC) codes to implement a CDMA system to support $2M$ users, where $M$ stands for the number of element codes in a flock of IQCC codes assigned to a user. The IQCC codes were designed to fit quadrature phase-shift keying modulation, where odd and even chips can be transmitted via I and Q carriers. We analyze correlation properties of the IQCC codes and introduce a CDMA system design based on the codes. The analytical results show that out-of-phase autocorrelation and cross-correlation functions are zero for any relative time shifts. Thus, a CDMA system implemented by the IQCC codes has an inherent capability to mitigate multiple access interference and multipath interference. [ABSTRACT FROM PUBLISHER]

Cyber-physical systems (CPSs) integrate the computation with physical processes. Embedded computers and networks monitor and control the physical processes, usually with feedback loops where physical processes affect computations and vice versa. CPS was identified as one of the eight research priority areas in the August 2007 report of the President's Council of Advisors on Science and Technology, as CPS will be the core component of many critical infrastructures and industrial control systems in the near future. However, a variety of random failures and cyber attacks exist in CPS, which greatly restrict their growth. Fortunately, an intrusion detection mechanism could take effect for protecting CPS. When a misbehavior is found by the intrusion detector, the appropriate action can be taken immediately so that any harm to the system will be minimized. As CPSs are yet to be defined universally, the application of the instruction detection mechanism remain open presently. As a result, the effort will be made to discuss how to appropriately apply the intrusion detection mechanism to CPS in this paper. By examining the unique properties of CPS, it intends to define the specific requirements first. Then, the design outline of the intrusion detection mechanism in CPS is introduced in terms of the layers of system and specific detection techniques. Finally, some significant research problems are identified for enlightening the subsequent studies. [ABSTRACT FROM PUBLISHER]

The blood circulation system in a human body provides a unique and natural trust zone for secure data communications in wireless healthcare systems such as body area networks. Unfortunately, biometric signal authentication using physiological attributes in wireless healthcare has not been extensively studied. In this paper, we propose a data authentication approach utilizing electrocardiography (ECG) signal patterns for reducing key exchange overhead. The major contribution of this research is to apply stochastic pattern recognition techniques in wireless healthcare. In the proposed approach, the inter-pulse interval (IPI) signal pattern at transmitter side is summarized as a biometric authentication key using Gaussian mixture model (GMM). At the receiver side, a light-weight signature verification scheme is adopted that uses IPI signals gathered locally at the receiver. The proposed authentication scheme has the advantage of high sample misalignment tolerance. In our earlier work, we had demonstrated the concept of stochastic authentication for ECG signal, but the signature verification process and GMM authentication performance under time synchronization and various sample points were not discussed. Here, we present a new set of analytical and experimental results to demonstrate that the proposed stochastic authentication approach achieves a low half total error rate in ECG signals verification. [ABSTRACT FROM PUBLISHER]