以提高接通率为中心 全面提高GSM系统的运行质量

围绕提高ＧＳＭ系统接通率这一课题，全面提高ＧＳＭ网的运行质量，结合黄石市实际情况，分析接通率低的主要因素，并为完成指标及提高接通率制定出具体措施。

Game theoretic analysis for pricing-based incentive mechanism in non-dedicated cooperative relay networks

In non-dedicated cooperative relay networks, each node is autonomous and selfish in nature, and thus spontaneous cooperation among nodes is challenged. To stimulate the selfish node to participate in cooperation, a pricing-based cooperation engine using game theory was designed. Firstly, the feasible regions of the charge price and reimbursement price were deduced. Then, the non-cooperative and cooperative games were adopted to analyze the amount of bandwidth that initiating cooperation node(ICN) forwards data through participating cooperation node(PCN) and the amount of bandwidth that PCN helps ICN to relay data. Meanwhile, the Nash equilibrium solutions of cooperation bandwidth allocations(CBAs) were obtained through geometrical interpretation. Secondly, a pricing-based cooperation engine was proposed and a cooperative communication system model with cooperation engines was depicted. Finally, an algorithm based on game theory was proposed to realize the cooperation engine. The simulation results demonstrate that, compared with the system without pricing-based incentive, the proposed system can significantly improve the ICN's metric measured by bit-per-Joule and increase the PCN's revenue.

Energy Efficient Data Collection in Hierarchical Wireless Sensor Networks

The majority of the energy consumption by the sensors is the energy requirement for data transmission in Wireless Sensor Networks （WSNs）. Therefore, introducing mobile collectors to collect data instead of nmlti-hop data relay is essential. However, for rmny proposed data gathering ap-proaches, long data deNNy is the train problenm. Hence, the problem of how to decrease the energy consumption and the data deNNy needs to be solved. In this paper, a low deNNy data collection mechanism using multiple mobile collectors is pro- posed. First, a self-organization clustering algorithm is designed. Second, sensor nodes are organized into three-level clusters. Then a collection strategy based on the hierarchical structure is proposed, which includes two rules to dispatch mobile collec- tors rationally. Simulation results show that the proposed mechanism is superior to other existing approaches in terms of the reduction in energy ex-penditure and the decrease in data deNNy.

Feedforward attitude control for a TDRS with mobile antennas

In this paper, feedforward attitude control law for a Tracking and Data Relay Satellite （TDRS） with mobile antennas is proposed. To track or point the target spacecraft with median/law orbit, the large mobile antennas have to move in a wide range. The movement of such mobile antennas disturbs the satellite attitude conscquently. Conventionally, the main body of thc satellitc and the mobile antennas are controlled independently. The proposed controller first estimates the angular momentum which the mobile antennas will produce based on tiLe momentum conservation equation. Next, it computes the desired velocity of reaction wheels to compensate the disturbance due to the antenna motion. It then adds the errnr of the wheels＇ velocity between a desired one and a current value as a feedforward signal to the control system. The proposed controller is demonstrated using a mathematical simulation, of which these results coincide well with analytical results.

Performance evaluation of the fixed relay in OFDMA systems

Performance of fixed relays in orthogonal frequency division multiple access （0FDMA） systems, especially the coverage and capacity performance at the cell edge, is evaluated in this paper. Two methods, theoretical analysis and calculation and Monte Carlo simulation, are used for the evaluations. By theoreti- cal analysis and calculation, frequency efficiency equation of a relay is introduced and numerical results are calculated. Monte Carlo simulation results also verify that the calculation method is reasonable. The evaluation shows that a relay can increase system performance to a certain level if it is designed appropriately, otherwise it will be harmful for the system performance, even to reduce it.

Performance analysis of relay-aided free-space optical communication system over gamma-gamma fading channels with pointing errors

The average bit error rate(ABER) performance of a decode-and-forward(DF) based relay-assisted free-space optical(FSO) communication system over gamma-gamma distribution channels considering the pointing errors is studied. With the help of Meijer's G-function, the probability density function(PDF) and cumulative distribution function(CDF) of the aggregated channel model are derived on the basis of the best path selection scheme. The analytical ABER expression is achieved and the system performance is then investigated with the influence of pointing errors, turbulence strengths and structure parameters. Monte Carlo(MC) simulation is also provided to confirm the analytical ABER expression.