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In order to solve the problem of the high outage probability and longtime service interruption during the handover process between platforms in high altitude platform stations (HAPS) communication system, the adaptive handover scheme based on cooperative transmission was proposed. The platform node, which has higher channel gain, was selected for cooperative transmission to improve the system reliability,...
In stratosphere, the cell handover performances of high altitude platform station (HAPS) communication system was affected by the quasi-stationary state of platform. The traditional handover algorithms based on the fixed thresholds usually can effectively deal with the handover issue caused by terminals' mobility. However given the platform disturbances, these algorithms show poor handover. At this...
By the effect of stratospheric winds, the position and attitude of high altitude platform are in the quasi-stationary state. This paper describes and discusses the swing state of the platform and on this basis, establishes antenna beam coverage geometry model, analyzes the impact of swinging state on handover. the average and maximum handover probability of the different tier cellular have been deduced...
In this paper, the widely used numerical optimization method for estimating linear frequency modulated signal parameters is modified. To this purpose, an improved Dividing RECTangles (DIRECT) algorithm, called the Lipschitz constant assisted DIRECT (L-DIRECT) algorithm, is proposed to substitute for the commonly used Grid Search method. The proposed global optimization algorithm can provide initial...
In the paper, the widely used numerical optimization method for linear frequency modulated (LFM) signal parameters estimation is modified. To this purpose, an improved Dividing RECTangles (DIRECT) algorithm is proposed to substitute for the commonly used grid search method. The proposed global optimization algorithm can provide initial estimates for local optimization algorithms such as Newton and...
Opportunistic relaying is an important relay selection scheme for cooperative communication, it can dynamically select relay depending on instantaneous channel condition, which is a especially suitable for distributed networks. Some cooperative MAC based on opportunistic relaying have been proposed to enhance the system throughput. However, since the throughput is normally related to their energy...
Opportunistic relaying is an important relay selection scheme for cooperative communication, which can dynamically select relay depending on instantaneous channel condition. A great deal of research has been conducted to study opportunistic relaying from the viewpoint of PHY layer and information theory. However, owing to the impact resulting from opportunistic relaying, there is no guarantee to enhance...
The paper presents a cooperative MAC based on opportunistic relaying for ad hoc networks. In the proposed MAC, the cooperative scheme will be activated on the condition that the source contended the channel successful, but the destination receives the inaccurate packets because of the channel noise. Based on opportunistic relaying, the neighbor which has the best channel condition to the destination...
The eigenspace-based (ESB) beamformer provides much robustness to pointing errors. However, it couldn't deal with small sample size which could degrade its performance severely. Forward-backward smoothing technique can improve the performance of beamformers with small sample size. Base on the character that the Forward-backward smoothing matrix is an generalized symmetrical conjugate matrix, The paper...
Based on the real-value characteristic of the non-circular sources, a new virtual array (VA) beamforming method is proposed. The method first extends the original array utilizing the conjugate data of the receiving signals and then applies the extended VA to adaptive beamforming. By analyzing its performance some drawbacks are found in the covariance matrix and the beam pattern, so the corresponding...
The eigenspace-based (ESB) beamformer demonstrates much more robust capabilities than the minimum variance distortionless (MVDR) beamformer. However, when the pointing error falls in some certain positions near the mainlobe edge or the integer times of half of the mainlobe width, its performance will suffer from severely degradation. To avoid the certain positions, the paper proposed a modified algorithm...
This paper discusses the problem of designing thinned linear and planar arrays with low peak sidelobe levels. It is concluded that the near-optimal method known as simulation is genetic algorithm. We see that genetic algorithm performs better on this synthesis problem by comparing the simulation results of uniform random arranged arrays (URA) and give a necessary analysis.
In this paper, we present a cooperative MAC protocol called automatic relay cooperative MAC (ARC-MAC) for wireless Ad Hoc networks. ARC-MAC develops the 802.11 DCF to five handshakes, which is suitable for cooperative transmission. According to the channel condition, neighbors decide whether it is a relay by itself, and the relay helps the source transmitting packets with a definite probability. An...
For the problem of carrier acquisition and tracking of high-dynamic spread spectrum signals, the analysis is presented for the influence of Doppler frequency shifts to the design of PLL (Phase Locked Loops), FLL (Frequency Locked Loops), and loop filters. A new design scheme of digital complex soft loop is proposed, and the simulation results show that the problem of fast carrier acquisition and tracking...
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