An adaptive low-overhead resource discovery protocol for mobile ad-hoc networks

In this paper we propose a Distributed Hash Table (DHT)-based peer-to-peer resource discovery protocol designed for large-scale Mobile Ad-hoc NETwork (MANET). The proposed Mobile Resource Discovery Protocol (MRDP) uses a distributed dynamic clustering algorithm to adaptively and rapidly group nodes in a MANET for resource discovery purpose, and utilizes DHTs to efficiently cache resource information in a peer-to-peer manner. We provide a probabilistic lower bound on the performance of the MRDP. We also present simulation results under different scenarios to show that MRDP has low message overheads and its performance is highly insensitive to the size of the MANET. These characteristics make MRDP suitable for large-scale MANETs.     

Joint detection for OFDM-CDMA communications in multipath fading channels

This paper proposes and compares four block joint detection algorithms for the orthogonal frequency division multiplexing (OFDM)-code division multiple access (CDMA) communication systems. The performance of the proposed OFDM-CDMA joint detectors with orthogonal and non-orthogonal spreading sequences are investigated in mobile radio channels. The proposed OFDM-CDMA detectors are zero forcing (ZF) and minimum mean square error (MMSE) detectors with decision feedback (DF) structures. The proposed joint detectors do not require discrete Fourier transform (DFT) or fast Fourier transform (FFT) operations and can be used to compensate the channel distortion. Hence for hardware implementation, the proposed detectors are more efficient than the conventional methods. The channel sorting method offers approximately 2 dB gain for the DF joint detectors and reduces the impairing effect of error propagation. The bit error rate (BER) performance of orthogonal codes is better than that of non-orthogonal ones in time varying channels. Simulation examples are given to demonstrate the effectiveness of the proposed detectors.     

Optimized Packet Scheduling Management: Maximizing Bandwidth Utilization for Next-Generation Mobile Multimedia Communications

Base stations in next-generation broadband mobile networks (NGBMNs) must efficiently schedule different kinds of multimedia packets providing different quality of service (QoS) classes. During the past 10?years, many researchers have experimented with various packet scheduling schemes. In this paper we will propose a batch-arrival queuing model for evaluating NGBMN multimedia packet scheduling systems, and for obtaining three performance measures: packet loss rate (PLR), queuing delay (QD), and bandwidth utilization (BU). The three measures can be used to solve utilization optimization problems with QoS constraints. Specifically, a combination of a traffic statistic plus maximum PLR and QD constraints can be used to maximize BU for a multimedia packet scheduling management architecture. According to results from mathematical tests of the proposed model, it offers an efficient approach to managing scheduling buffers. The model and optimized parameters can be applied to flexible bandwidth deployment and classified buffer size control, thus enhancing profitability.     

Advanced environmentally friendly coatings prepared from amine-capped aniline trimer-based waterborne electroactive polyurethane

Electroactive waterborne polyurethane (EWPU) containing conjugated segments of electroactive amino-capped aniline trimer (ACAT) unit was successfully prepared and characterized. Iodine-doped EWPU with conductivity 1.2 × 10⁻⁶ S cm⁻¹ was detected. The electroactivity of EWPU was evaluated by performing electrochemical cyclic voltammetry studies. It was worth noting that the EWPU coating was found to exhibit enhanced corrosion protection effects on cold-rolled steel (CRS) electrodes as compared to the corresponding non-electroactive waterborne polyurethane (NEWPU) coating based on a series of electrochemical measurements in 3.5 wt% NaCl electrolyte. A possible mechanism for the enhanced corrosion protection ability of the EWPU coatings on the CRS electrode could be interpreted as the redox catalytic capabilities of the aniline trimer units existed in EWPU induce the formation of passive metal oxide layers on the CRS electrode, as further evidenced by SEM and XPS studies. The thermal stability of EWPU was also investigated by thermogravimetric analysis (TGA).     

Call blocking probability and bandwidth utilization of OFDM subcarrier allocation in next-generation wireless networks

Various studies have devised OFDM subcarrier-allocation schemes in next-generation wireless networks. However, the subcarrier-allocation system performance has seldom been assessed, especially in terms of the call blocking probability (CBP) and bandwidth utilization.(BU). This study proposes a batch-arrival bath-loss queueing model to evaluate the performance or the subcarrier-allocation system,and derives expressions for calculating two important system performance measurements, CBP and BU. Simulation results. indicate that the measures appear to work. The model should be helpful for constructing OFDM based wireless networks.     

Design and analysis of direct-action CMAC PID controller

This paper is to propose a direct-action (DA) cerebellar model articulation controller (CMAC) proportional-integral-derivative (PID) controller. The proposed controller, termed the DAC-PID controller, can generate four simple types of the nonlinear functions and then determine a control effort from those functions to control the process. In addition, the real-coded genetic algorithm is used to tune the parameters of the DAC-PID controller such that we can optimize those parameters. The performance of the proposed controller is also discussed in the sense of quantitative analysis. Simulation results demonstrate that the DAC-PID controller is superior to the conventional PID controller tuned by Ziegler–Nichols method and, moreover, as better as the optimal PID controller and the optimal fuzzy-PID controller.