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Very small aperture terminal (VSAT) at Ku-band is very attractive in complex terrestrial and marine environment of military or disaster scene. The small aperture antenna characteristic of VSAT leads to strong interference to adjacent satellite systems. This situation is severely aggravated as Geostationary Satellite Orbit (GSO) becomes extremely congested. Various national and international agencies have imposed regulations on VSAT adjacent satellite interference (ASI). One regulation, called ∆T /T method, is used for accessing the necessity of ASI coordination, which is sophisticated and inconvenient to carry out. Another regulation imposed limit on off-axis effective isotropic radiated power (EIRP) of terminal, and specified the maximum allowable off-axis EIRP spectral density (OESD). This paper described and analyzed the salient features of these ASI regulations. Upon demonstration of their compatible and complementary relationships, it is shown that the simpler EIRP rule can be an alternative for the more complex ∆T/T method for ultra-small terminals (USAT). In this way, it will help reduce the complexity of the coordination determining procedure.

Research on modeling and simulation of Link-16 has attracted much attention nowadays. However as one kind of legacy system, Link-16 was not constructed based on layering principles and it is not well compatible with Global Communication Grid (GCG), also known as Global Grid (GG) that has been developed with military requirement in mind. This paper concentrates on applying Global Information Grid (GIG) layering principles on modeling and simulation of Link-16 data link. The following paper is divided into two approaches, the first issue is considered in a general way for briefing GIG layering principles and secondly we analyze the Link-16 system in layering principles to see if this tactical information distribution system can be divided into distinct sub layers.

In contrast with Phase-Locked Loop (PLL), Frequency Locked Loop (FLL) has better dynamic performance. There were papers dealing with noise performance of FLL. However, under the circumstance of CW input, there were large gap between simulation results and theory results which were obtained from published papers. This paper analysis the reason of the gap and proposes an improved calculation method in the condition of four-quadrant arctangent and cross product discriminator. Results show that the improved calculation method fits the simulation result very well.

Al 2 O 3 thin films were characterized by optical and structural properties, as well as LIDT under 355 nm Nd:YAG laser. It was found that the deposition temperature had no clear effect on the LIDT in our experiments.

On the basis of analyzing the limitations of mobile IP protocol in pervasive computing environment and in combination with the technological advantages of mobile agent, this paper introduces a mobile-agent-based application model of pervasive mobile devices. With the introduction of mobile agent into the pervasive mobile devices, the application model enables all corresponding IP messages to go through the mobile agent, which can directly detect the status information of the IP messages, thus making it possible to switch the mobile devices smoothly. Through handoff delay analysis and simulation experiments, the paper also analyses and contrasts the performance of the pervasive mobile devices before and after the mobile agent is introduced. The results show that with the introduction of mobile agent, the pervasive mobile devices can switch smoothly and swiftly, decrease handoff delay and the status information in the process of the transmission and reduce the loss ratio of handoff of the mobile devices, thus effectively improving the performance of the mobile networks in the pervasive computing environment.

In this paper, we describe and analyze a new two-step frequency estimation algorithm for pilot symbol assisted modulation (PSAM) systems with a non-uniform pilot pattern. The burst structure includes some consecutive pilots at the beginning of each burst and some sparse ones over the burst. Compared with the FFT-based (Fast Fourier Transform based) algorithm, its computational complexity is reduced greatly. It facilitates the estimation of large frequency offsets and high accuracy. Its estimation range is about plusmn20% of the symbol rate and its accuracy is close to the Cramer-Rao bound (CRB) for a low signal-to-noise ratio (SNR).

We propose an iterative data-aided algorithm based on maximum likelihood criteria for carrier frequency estimation in burst-mode phase shift keying (PSK) transmission. The proposed algorithm has a low threshold and its estimation range is large, about plusmn40% of the symbol rate. In addition, its accuracy is close to the Cramer-Rao bound (CRB) at signal-to-noise ratio (SNR) above threshold. The performance of the proposed algorithm is better and its computational complexity is also lower compared with previous ML-based algorithms.

In traditional feedback structure of direct sequence spread spectrum (DS-SS) receiver, delay lock loop is a prevailing approach to estimate the timing error. However, in burst communication, it is hard for DLL to be in transient state or lock the signal with high accuracy. In this paper, an efficient feedforward PN code timing recovery scheme is proposed for DS-SS systems. The received signal after the chip-matched filter is two times over-sampled. The characteristics of DS-SS signal are explored to make the synchronization scheme efficient and simple in such a low sampling rate. Three sets of correlation values with different timing offsets are stored to estimate the code timing and carrier phase error. With very low computational complexity, the proposed scheme can make the performance approaches to the DS- SS systems with ideal synchronization in an AWGN channel.

In this paper, we describe and analyze an efficient non-date-aided (NDA) symbol timing recovery algorithm named the Quadratic Approximation (QA) algorithm. Compared with the Tone Filtering (TF) algorithm, the algorithm presented here is low-complexity. It requires only one multiplication per burst. Its performance is better than that of the TF algorithm in terms of the estimated standard deviation and sensitivity to frequency offsets.

In this paper, an efficient iterative timing and carrier phase recovery scheme is proposed for LDPC-Coded Direct Sequence Spread Spectrum (DS-SS) systems. The received signal after the chip-matched filter is two times over sampled per chip. The characteristics of DS-SS signal and LDPC decoder are explored to make the synchronization scheme efficient and simple in such a low sampling ratio. Three sets of correlation values provided by three correlators with different timing offsets are stored to estimate timing and carrier phase. The estimation is performed once per decoding iteration based on the maximum likelihood theory aided by hard decision obtained from LDPC decoder. The overall complexity of this scheme is very low and the performance of the proposed scheme approaches that with the ideal synchronization on AWGN channel.

A simplified ML-based iterative synchronization scheme is proposed in this paper for LPDC-coded systems. Symbol timing and carrier phase are estimated in a simple way based on the maximum likelihood theory aided by hard decision obtained from LDPC decoder. The synchronized samples input to the decoder are updated when a new iterative estimation for symbol timing and carrier phase is completed. The synchronized samples are reconstructed by quadratic interpolation which is very simple and can be implemented in parallel. This approach is applied to a LDPC-coded QPSK system over AWGN channel. Simulation results demonstrate that the performance of the proposed scheme approaches that with the ideal synchronization

A distributed control system (DCS) based on two-layer networks for experimental teaching is presented in this paper. Three sets of equipments are used as process objects with their parameters such as pressure, temperature, level and flow rate being controlled variables. This system has multiform training functions. Students can not only set up basic experiments about the process control, but can also design complicated control system. The result of 4 years' use shows: it is an ideal engineering simulating system for students major in industrial automation.

In this paper, two reduced-complexity timing detectors for MC-CDMA signals based on incorporating the on-time arm in timing error signal update are proposed and analyzed. By theoretical analysis and simulations, it is shown that the simplified approaches provide superior performance for low Eb/N0 with respect to the classical non-coherent early-late gate detector.

A novel timing tracking algorithm suited for multi-carrier DS-CDMA signals by introducing vector rotation and samples selecting is proposed and studied. Numerical results shows that the new scheme has a remarkable hardware simplicity advantages but no performance degradation when compared to the conventional non-coherent delayed-lock loop (DLL).