TP-Satellite: A New Transport Protocol for Satellite IP Networks

As a result of the exponential growth of the worldwide Internet, satellite systems are used to support broadband Internet access. Existing TCP protocols perform very well for Internet access on wired networks. However, in the case of satellite channels, due to the effects of high bandwidth asymmetry, long propagation delay, high sporadic bit error rate (BER) and burst errors, TCP performance degrades significantly. In this paper, a new end-to-end transport protocol, TP-Satellite, is proposed for satellite IP networks. TP-Satellite replaces the traditional slow start algorithm with a novel super start algorithm. In order to distinguish congestion events from link errors, a new scheme is introduced, which is based on alternate transmission of different class priority packets. Bandwidth asymmetry problems are addressed by the adoption of a modified negative acknowledgement (M-NACK) strategy, which periodically sends M-NACK packets. Simulation results show that TP-Satellite enhances the throughput performance on the forward path, reduces the bandwidth used in the reverse path, and offers a fair share of network resources.     

针对ATN over IP方案的明确拥塞通告模型及映射算法

基于对ATN与IP网络拥塞控制机制的比较,本文针对AT Nover IP方案提出了IP子网隧道中的明确拥塞通告(ECNT)模型,将明确拥塞通告(ECN)引入了AT Nover IP方案;还提出了ECNT模型中实现IP网络明确拥塞通告(ECN)与ATN网络传输层协议COTP中拥塞指示位(CE)的映射算法(ECN/CE),用以解决由于IP网络中TCP协议与ATN网络中COTP协议所采用的两种拥塞避免在机制上的差别而造成的拥塞信息跨网络传输的困难。仿真结果表明,与没有引入ECN的IP子网隧道模型相比,ECNT模型和ECN/CE算法可以解决IP网络为ATN的网络进行数据传输时的拥塞问题。     

TCP-ATCA： Improved Transmission Control Algorithm in Satellite Network

An adaptive transmission control algorithm based on TCP （TCP-ATCA） is proposed to reduce the effects of long propagation delay and high link error rate of the satellite network on the performances. The flow control and the error recovery are differentiated by combined dynamic random early detection-explicit congestion notification （DRED-ECN） algorithm, and, moreover, the pertaining congestion control methods are used in TCP-ATCA to improve the throughput. By introducing the entire recovery algorithm, the unnecessary congestion window decrease is reduced, and the throughput and fairness are improved. Simulation results show that, compared with TCP-Reno, TCP-ATCA provides a better throughput performance when the link capacity is higher （ ≥600 packet/s）, and roughly the same when it is lower. At the same time, TCP-ATCA also increases fairness and reduces transmission delay.     

AeroMTP: A fountain code-based multipath transport protocol for airborne networks

Airborne networks(ANs) are special types of ad hoc networks that can be used to enhance situational awareness, flight coordination and flight efficiency in civil and military aviation.Compared to ground networks, ANs have some unique attributes including high node mobility, frequent topology changes, mechanical and aerodynamic constrains, strict safety requirements and harsh communication environment.Thus, the performance of conventional transmission control protocol(TCP) will be dramatically degraded in ANs.Aircraft commonly have two or more heterogeneous network interfaces which offer an opportunity to form multiple communication paths between any two nodes in ANs.To satisfy the communication requirements in ANs, we propose aeronautical multipath transport protocol(Aero MTP) for ANs, which effectively utilizes the available bandwidth and diversity provided by heterogeneous wireless paths.Aero MTP uses fountain codes as forward error correction(FEC) codes to recover from data loss and deploys a TCP-friendly rate-based congestion control mechanism for each path.Moreover, we design a packet allocation algorithm based on optimization to minimize the delivery time of blocks.The performance of Aero MTP is evaluated through OMNe T++ simulations under a variety of test scenarios.Simulations demonstrate that Aero MTP is of great potential to be applied to ANs.     

A Novel Onboard-gateway-based Mechanism to Improve TCP Performance in Aeronautical Satellite Networks

The IP-based networks on aircraft serve to support Internet services via satellites. However, in aeronautical satellite hybrid net- works,the TCP protocol performance often deteriorates due to improper decreases and slow recovery of the congestion window. This paper proposes a window size determination and notification mechanism, onboard-gateway-based mechanism (OGBM), which is based on the onboard gateway in the networks on aircraft. A cross-layer approach is adopted by the onboard gateway to obtain the satellite link bandwidth information. And then, by the gateway, through changing the receiver’s advertised window field in ACK packets, TCP sources are notified of the window size of each TCP source calculated on the ground of bandwidth delay product and flow numbers. The mechanism is able to avoid improper changes of TCP window and serve multiple users. Simulation results show that the mechanism with the fairness index close to 1 improves TCP performance in aeronautical satellite networks.     

空间数据通信协议SCPS—TP应用研究

目前对Vegas拥塞避免机制在SCPS—TP协议上的应用已经有了一定的研究;由于在航天测控网中存在着网络拓扑结构改变现象,这会严重影响Vegas机制的性能。本文提出一种基于BP神经网络的Vegas改进算法,设法减小航天测控网网络拓扑结构改变对Vegas机制性能的影响。仿真实验表明,该算法明显提高了SCPS—TP协议在航天测控网中的数据传输性能。     

基于MIT的扇区流量管理决策

为缓解空中交通拥堵和减少航班延误,建立了扇区流量管理模型,并定义扇区容量超负荷频率指标,提出基于尾随间隔(MIT)的3种扇区流量管理决策方案,分析了郑州某个高空管制扇区8:00~9:00时段流量管理实例,结果表明合理的流量决策方案不仅能够缓解扇区拥堵,而且减少了41%的延误,验证了扇区流量管理决策方案的有效性及实用性,可以为决策者提供一定的决策支持。     

积分滑模控制在飞艇舵面故障中的应用

针对飞艇运动姿态的小扰动模型,利用极点配置方法设计了积分滑模控制器。对飞艇"×"型舵面出现的故障,给出了期望的特征根,并选择合适的特征向量来构造积分滑模面。给出了一种快速的趋近律形式,并证明了其稳定性。仿真结果表明,与PD控制器相比,积分滑模控制器能使飞艇的运动姿态保持良好。     

Distortion minimization for multimedia transmission in NOMA HAP-UAV integrated aerial access networks

Aerial access networks have been envisioned as a promising 6G solution to enhance the ground communication systems in both coverage and capacity. To better utilize the spectrum and fully explore different channel characteristics, this paper constructs an integrated network comprising the High Altitude Platform (HAP) and Unmanned Air Vehicles (UAVs) with the Non-Orthogonal Multiple Access (NOMA) technology. In order to improve the transmission quality of images and videos, a power management scheme is proposed to minimize the distortion of the transmissions from the HAP and UAVs to the terminals. The power control is formulated as a non-convex problem constrained by the maximal transmit power and the minimal terminal rate requirements. The variable substitution and the first-order Tailor’s expansion is used to transform it into a sequence of convex problems, which are subsequently solved through the gradient projection method. Simulation demonstrates the signal distortion and error rate improvement achieved by the proposed algorithm.     

TCP协议在空间网络中的传输时延分析

探讨了为适应空间网络环境对TCP协议机制进行的一些改进,通过模拟实验,对协议改进方案的性能进行了分析和比较。实验结果表明：协议改进后能够减小时延,避免不必要的重传,提高了信道的利用率。     

综合飞行/矢量推进系统控制器分离方法

详细阐述了综合飞行/矢量推进系统控制器分离问题,并给出了采用解析法求解控制器分离问题的步骤.以解析的控制器分离为基础,提出了一种基于非线性最小二乘方法的控制器分离的优化方案,该优化方案非常有效并且很便于实现.利用此优化方案,求取了一个最优的控制器分离.非线性仿真实验表明:最优分离子控制器几乎达到了同集中控制器一样的闭环性能,所讨论的控制器分离方案是相当合适和成功的.      

基于EtherCAT通信的双直线电机位置联动控制系统设计

针对传统脉冲、模拟量控制系统在实时性、稳定性和同步性方面的不足,提出了一种基于EtherCAT工业实时以太网通信的双直线电机位置联动控制方案。设计了3种位置联动控制模式,详细分析了EtherCAT的分布时钟补偿算法,并搭建了联动控制试验平台,对所设计的控制系统进行了试验验证。试验结果表明,采用EtherCAT通信的双直线电机位置联动控制系统实时性高,双轴同步、交替响应性能良好,适用于同步精度和响应速度要求都较高的应用场合。     

TCP/IP协议在发动机试验测控网络中的应用研究

阐述了TCP/IP协议及其在测控网络中的应用特点，分析了可能发生的如以太网拥塞和传送数据包丢失等实际问题，并提出了相应的解决办法，在发动机试验测控网络中获得了成功应用。     

基于短时傅里叶变换的Duffing振子微弱信号检测

研究了Duffing振子信号检测过程中混沌、间歇混沌和大周期状态的时频特征,提出了一种基于检测统计量的任意频率信号检测方法。通过对系统不同状态下的输出序列进行短时傅里叶变换(STFT)发现,等幅线和三维时频分布能够体现出不同状态的显著差异,且可以完全区分出每一种状态。从构造统计量的易实现性出发,用三维时频分布中的幅时曲线作为衡量不同状态的依据,并将不同频率对应的幅时曲线的均值最大量作为检测统计量,该统计量的计算可以借助快速傅里叶变换(FFT)操作提高时效性。在此基础上,引入频率控制单元,给出了任意频率信号的检测方法步骤,方法的关键是将检测统计量最大值处所在的频率作为待测信号频率范围的一个端点,另一个端点为毗邻的两个检测统计量值较大者所在频率点。实验给出了不同状态的检测统计量范围,进而以此范围为判据,实现了振子对任意频率信号的检测,说明了方法的可行性,为Duffing振子信号检测问题的研究提供了一种新的思路。     

Integrated active fault-tolerant control using IMM approach

An integrated fault detection, diagnosis, and reconfigurable control scheme based on interacting multiple model (IMM) approach is proposed. Fault detection and diagnosis (FDD) is carried out using an IMM estimator. An eigenstructure assignment (EA) technique is used for reconfigurable feedback control law design. To achieve steady-state tracking, reconfigurable feedforward controllers are also synthesized using input weighting approach. The developed scheme can deal with not only actuator and sensor faults, but also failures in, system components. To achieve fast and reliable fault detection, diagnosis, and controller reconfiguration, new fault diagnosis and controller reconfiguration mechanisms have been developed by a suitable combination of the information provided by the mode probabilities from the IMM algorithm and an index related to the closed-loop system performance. The proposed approach is evaluated using an aircraft example, and excellent results have been obtained     

涡扇发动机进口畸变条件下的优化控制规律

提出了一种满足涡扇发动机不同进口畸变要求的控制规律.在涡扇发动机低进口畸变条件下通过提高增压比来提高性能,在高进口畸变条件下降低增压比并辅助导叶角调节以提高发动机裕度.根据不同的进口畸变条件下的裕度要求,提出了带边界缓冲区的差分进化算法(DEBZ),在包线内优化获取发动机增压比及导叶角控制规律.结合模型、控制器和控制规律完成涡扇发动机全包线仿真.仿真结果表明:采用该控制规律在畸变指数为2的条件下,涡扇发动机推力性能能够提高8%以上,而在畸变指数为8的条件下,涡扇发动机的可用裕度可以满足稳定要求,同时推力性能能够提高1%以上.      

Optimal acknowledgment frequency over asymmetric space-internet links

The acknowledgement (ACK) strategy of transmission control protocol (TCP) has been modified to delay the ACKs for a configurable period of time that is related to the round-trip time (RTT) to improve its performance in asymmetric links such as space communications. A general relationship between the asymmetric channel ratio and the optimal ACK frequency to achieve maximum throughput is not available. This paper studies the optimal ACK frequency with respect to the channel RTT to achieve the maximum throughput over various asymmetric, geo-stationary earth orbit (GEO)-satellite links using a test-bed. It is found that when the asymmetric channel ratio is as high as about 100/1, the optimal ACK frequency must be increased with an increase in asymmetric ratio to complement the impact of the reduction of ACK channel rate. As a rule of thumb, every two-fold increase in asymmetric ratio requires the optimal ACK frequency to be increased by one ACK per RTT. A regression model was built to reflect the relationship between the optimal ACK frequency and the asymmetric channel ratio and has been validated     

高速飞行器空腔脉动压力主动控制与非线性数值模拟

空腔脉动压力(空腔噪声)预测是高速飞行器内埋弹舱的关键技术之一。非线性噪声求解方法是近年来新提出的一种噪声求解方法,为研究该方法对空腔噪声的预测性能,将雷诺平均Navier-Stokes(RANS)方程与之相结合。首先,通过RANS求解空腔周围流场,得到初始湍流统计平均解,其中包含平均流场基本特征及强制设定的湍流脉动的统计描述。然后,采用非线性噪声求解方法重构噪声源并高精度模拟压力脉动的传播,计算了马赫数Ma=1.5和Ma=5条件下的空腔噪声。结果表明,噪声特性计算值与试验结果基本吻合,说明非线性噪声求解方法对于高速空腔流动噪声具有较好的预测能力。在此基础上,研究了马赫数Ma=1.5和Ma=5条件下在空腔前缘加入气帘喷流主动控制措施对噪声的抑制作用,并得出在超声速和高超声速条件下,气帘喷流对于空腔脉动压力都有较好的抑制作用。     

Further studies on efficient AFEC schemes for Ka-bandsatellite systems

Adaptive fade margin is required to counter the severe but varying rain attenuation in Ka satellite communications. In searching for a suitable rain countermeasure, the effectiveness of the adaptive forward error control (AFEC) scheme is studied. Two AFEC schemes using convolutional codes and concatenated codes are proposed and their performance analyzed. The schemes can provide a progressively adaptive fade margin of 10.1 and 10.4 dB, respectively, in excess of the systems fixed fade margin. To improve the efficient use of shared resources of the system, an AFEC scheme using double coding is introduced, and its performance is analyzed. In this scheme a single codec is used repeatedly, and as a result the hardware cost is reduced and the utilization increased. The effective usable capacity of a conceptual AFEC resource sharing scheme using Golay double coding is also analyzed     

Excitation control of a synchronous generator using a lookup table

A scheme involving the use of a lookup table is developed for the excitation control of a synchronous generator. The proposed control scheme, generator speed deviation, and acceleration deviation are taken as the input signals. These input signals are sampled and converted to linguistic terms before they are fed into the controller. The controller generates the desired output (control) signal by using a set of production rules (if-then rules) that are based on previous experience to relate the input signals to the output. The output signal is converted from linguistic terms to a numerical value before it is sent to the excitation system of the synchronous machine. To demonstrate the effectiveness of the proposed control scheme, digital simulations of a synchronous generator subject to a three-phase fault under different operating conditions were performed. It was found that the controller can improve the dynamic performance of a synchronous generator over a wide range of operating conditions. Since the controller does not require model identification, it is computationally efficient and is suitable for online excitation control, using a microcomputer