Mega-Constellations Based TT&C Resource Sharing: Keep Reliable Aeronautical Communication in an Emergency

With the development of the transportation industry, the effective guidance of aircraft in an emergency to prevent catastrophic accidents remains one of the top safety concerns. Undoubtedly, operational status data of the aircraft play an important role in the judgment and command of the Operational Control Center(OCC). However, how to transmit various operational status data from abnormal aircraft back to the OCC in an emergency is still an open problem. In this paper, we propose a novel Telemetry, Tracking,and Command(TT&C) architecture named Collaborative TT&C(CoTT&C) based on mega-constellation to solve such a problem. CoTT&C allows each satellite to help the abnormal aircraft by sharing TT&C resources when needed, realizing real-time and reliable aeronautical communication in an emergency. Specifically, we design a dynamic resource sharing mechanism for CoTT&C and model the mechanism as a single-leader-multi-follower Stackelberg game. Further, we give an unique Nash Equilibrium(NE) of the game as a closed form. Simulation results demonstrate that the proposed resource sharing mechanism is effective, incentive compatible, fair, and reciprocal. We hope that our findings can shed some light for future research on aeronautical communications in an emergency.

Simulation Design of Baseband Optimal Digital Communication System with Non-Ideal Channel

This paper aims to discuss how to effectively suppress intersymbol interference by optimizing the filter design, so as to achieve a distortion-free output effect, and effectively compensate the transmission characteristics of the baseband transmission system in a non-ideal channel environment, so as to minimize the impact of intersymbol crosser. The simulation experiment model of digital optimal baseband transmission and the overall structure of the system are designed based on the Matlab simulation platform, and the parameters of each module in the simulation experiment model are set. The working process and performance of the digital optimal baseband transmission system are simulated, and the conditions and performance of the digital optimal baseband transmission system are verified according to the simulation results.

Echo state network based symbol detection in chaotic baseband wireless communication

The Chaotic Baseband Wireless Communication System(CBWCS)is expected to eliminate the Inter-Symbol Interference(ISI)caused by multipath propagation by using the optimal decoding threshold that is the sum of the ISI caused by past decoded bits and the ISI caused by future transmitting bits.However,the current technique is only capable of removing partial effects of the ISI,because only past decoded bits are available for the suboptimal decoding threshold calculation.The unavailability of the future information needed for the optimal decoding threshold is an obstacle to further improve the Bit Error Rate(BER)performance.In contrast to the previous method using Echo State Network(ESN)to predict one future bit,the proposed method in this paper predicts the optimal decoding threshold directly using ESN.The proposed ESN-based threshold prediction method simplifies the symbol decoding operation by avoiding the iterative prediction of the output waveform points using ESN and accumulated error caused by the iterative operation.With this approach,the calculation complexity is reduced compared to the previous ESN-based approach.The proposed method achieves better BER performance compared to the previous method.The reason for this superior result is twofold.First,the proposed ESN is capable of using more future symbols information conveyed by the ESN input to obtain more accurate threshold rather than the previous method in which only one future symbol was available.Second,the proposed method here does not need to estimate the channel information using Least Squared(LS)method,which avoids the extra error caused by inaccurate channel information estimation.Simulation results and experiment based on a wireless open-access research platform under a practical wireless channel show the effectiveness and superiority of the proposed method.

基于遗传算法的TT&C测控资源优化调度(英文)

TT&C测控资源调度是一个涉及卫星、测控站以及调度准则等多方面因素的复杂优化问题。针对这一优化问题,根据测控调度的一般原则和优化准则,建立了相应的优化模型,并给出了基于遗传算法求解该问题的方法和步骤;最后,通过两个示例分析,演示验证了该方法对于解决一般测控调度问题的有效性。

带局部交互的多星TT&C调度合作协同进化

针对现有合作协同进化机制较少利用局部协同信息的问题,通过对多星TT&C资源调度的合作协同进化求解进行改进,在全局协同的基础上加强局部交互,为每个个体设定一个表明其与所有相邻子种群合作效果的进化性能指标——局部交互值,将该值作为选择操作中衡量个体优劣的尺度之一,以局部交互值与各子适应度之和的差值决定个体变异率,使变异具有自适应性,从而减少由子种群代表个体选择的非全局性造成的优秀个体丢失现象。仿真实验结果表明该方法能较好地提高求解质量。

TT&C系统中测距误差的频率特性分析法

以往的文献中,多用群时延来分析TT&C的测距误差,这种方法不够准确和全面。本文采用幅、相频率特性和相位波动特性来分析TT&C信道中的测距误差。详细讨论了由于信道频率特性和相位波动特性变化产生的测距误差,给出了测距侧音相位的数学表达式。运用这些公式可以计算出这些因素对测距漂移误差的影响,提高测距精度。

航天TT&C调度的拉格朗日松弛策略

根据航天遥测、跟踪和指挥(TT&C)调度的测控需求,建立航天测控调度问题的0-1整数规划模型,运用(λ,ν)、(μ,ν)和(λ,μ)3种策略对模型中的约束进行松弛,通过次梯度优化算法求得每种松弛问题的上界。利用2个场景验证上界(目标函数值)的有效性,调度结果表明,3种松弛策略中以次梯度优化算法得到的上界差别最小。

TT＆C站的距离零值标校及其误差分析

本文对采用上行调频、下行调相、多侧音测距体制的TT＆C站的距离零值标校方法、标校设备进行了讨论,并对标校误差进行了分析。

Networked TT&C for Mega Satellite Constellations:A Security Perspective

Satellite constellations are promising in enabling the global Internet.However,the increasing constellation size also complicates tracking,telemetry and command(TT&C)systems.Traditional groundbased and space-based approaches have encountered significant obstacles due to,e.g.,the limited satellite visible arc and long transmission delay.Considering the fast development of intersatellite communications,synergy among multiple connected satellites can be exploited to facilitate TT&C system designs.This leads to networked TT&C,which requires much less predeployed infrastructures and even performs better than traditional TT&C systems.In this paper,we elaborate system characteristics of networked TT&C compared with traditional ground-based and spacebased TT&C,and propose the unique security challenges and opportunities for networked TT&C,which includes secure routing and trust mechanisms.Furthermore,since networked TT&C is a novel scenario with few relevant researches,we first investigate the current researches on secure routing and trust mechanisms for traditional terrestrial and satellite networks,and then accordingly deliver our security perspectives considering the system characteristics and security requirements of networked TT&C.

Beamforming of Whole Airspace Phased Array TT&C System Based on Linear Subarrays

The whole airspace phased array telemetry,track and command(TT&C)system is regarded as the development tendency of next generation TT&C system,and the distribution of the antenna units and the beamforming technology have sparked wide interest in this field.A method for antenna distribution is proposed based on the linear subarrays technology.A symmetrical truncated cone conformal array is composed of the linear subarrays placed on the generatrix.The impact of truncated cone bottom radius and elevation angle on beamforming are studied and simulated.Simulation results verify the system design.

Design of an adaptive precoding/STBC baseband transceiver on a reconfigurable architecture

Precoding and space-time block coding （STBC）techniques using the uniform channel decomposition （UCD）are proposed to improve the bit error rate （BER） of themultiple-antenna communication system, but at a cost of areduced data rate. In order to achieve a higher overall systemperformance, a novel adaptive transceiver architecture whichflexibly combines both UCD and UCD ＋ STBC technologies isproposed. The channel state information （CSI） feedback pathwas added to the precoder to select which coding method wasto be used, i.e. UCD alone or UCD ＋ STBC. With thesmaller constellation sizes, Matlab simulation results showthat, the adaptive transceiver architecture will select the UCD-only mode under the higher SNR conditions in order to achievea higher bit rate. The UCD ＋ STBC mode will be selectedunder the lower SNR conditions （e. g., SNR 〈 10 dB） inorder to maintain good BER performance at the cost of areduced data rate. This architecture was implemented andverified using both UMC 0.18 ASIC process technology and aXilinx xc4vlx Virtex-4 FPGA at 150 MHz. The simulationresults demonstrate that the required number of reconfigurablearithmetic unit slices grows linearly with the channel matrixsize, while the number of adder array unit and reconfigurablelogic unit slices increases slightly with the constellation size.

NUMERICAL SIMULATION OF TIME-DOMAIN EM SCATTERING BY SHALLOW SUBSURFACE OBJECTS

The time-domain ElectroMagnetic(EM) scattering by buried objects in dispersive media is calculated with FD-TD method. The FD-TD formula in Debye dispersive media (both the complex permeability and the complex permittivity are described by Debye equations) are deduced, and the absorbing boundary condition is given. The validity of FD-TD method in lossy media is verified through comparing the FD-TD’s results and the other ones. The propagation of transient pulses in dispersive media is studied in detail. The scattering pulses and the wiggle traces for typical buried objects are given.

ALGORITHMS AND ARCHITECTURE IMPLEMENTATIONS OF MIMO OFDM BASEBAND RECEIVER BASED ON THE SIMD DSP CORE

This letter presents a programmable single-chip architecture for Multi-lnput and Multi-Output （M1MO） OFDM baseband receiver. The architecture comprises a Single Instruction Multiple Data （SIMD） DSP core and three coprocessors that are used for synchronization, FFT and channel decoder. In this MIMO OFDM system, the Zero Correlation Zone （ZCZ） code is used as the synchronization word preamble of packet in the physical layer in order to avoid the interference from other transmitting antennas. Furthermore, a simple channel estimation algorithm is proposed which is appropriate tbr the SIMD DSP computation.

Method to Realize TT&C of Spacecraft In-Orbit from Ground-Based to Space-Ground-Based Mode

Currently, TT&C of spacecraft is performed by a ground system. Because more and more spacecrafts are launched into orbits, it is difficult for the ground system to meet the TT&C requirements of the spacecrafts. To explore a new, effective and economical TT&C mode is absolutely necessary. A method is proposed to use SGBM mode in TT&C spacecrafts in low earth orbits, here. Firstly, the principle of the mode is discussed; secondly, the system to simulate the mode is designed; thirdly, the relative issues to use the mode are indicated; fourthly, the experimental results (simulation) to apply the mode to TT&C spacecrafts are analyzed; and finally dawn is the main conclusion of the method.

Continuous-Wave Interference Mitigation for Acquisition Method in Unified Carrier TT&C Systems

An interference mitigation for acquisition method,based on both energy center and spectrum symmetry detection,has been proposed as a possible solution to the problem of signal acquisition susceptibility to continuous-wave interference(CWI)in unified carrier telemetry,tracking,and command(TT&C)systems.With subcarrier modulation index as a priori condition,the existence of CWI is determined by comparing the energy center with the symmetric center.In the presence of interference,the interference frequency point is assumed and culled;sequentially,the spectral symmetry is used to verify whether the signal acquisition is realized.Theoretical analysis,simulations,and experimental results demonstrate that the method can realize the acquisition of the main carrier target signal with an interference-to-signal ratio of 31 dB,which represents an improvement over the existing continuous-wave interference mitigation for acquisition methods.

Introduction to the TT&C Scheme for Chang’e⁃5 Mission

Chang’e-5 mission is China’s first lunar sample return mission.It contains several new flight phases compared with the previous lunar missions,such as the lunar take-off and orbit insertion phase,the rendezvous and docking phase,etc.Chang’e-5 mission is extremely complicated and full of new challenges.This paper sorts out the characteristics and the difficulties in telemetry,tracking,and command(TT&C)of Chang’e-5 mission.The main technical contribution is a reliable general design of the TT&C system,including the application of X-band TT&C in launch and early orbit phase(LEOP),multiple targets simultaneous TT&C in X-band,lunar surface benchmark calibration,high-precision and rapid orbit trajectory determination for the lunar surface take-off,remote guidance rendezvous and docking,the determination of the initial navigational value for the separation point of the Chang’e-5 orbiter and returner,and the design of the reentry measurement chain.Based on this scheme,a global deep space TT&C network and interplanetary reentry measurement chain have been established for China,and near-continuous TT&C support for China’s first extraterrestrial object sampling and return mission has been realized,ensuring reliable tracking,accurate measurement and accurate control.The global deep space network can provide TT&C support comparable to that of National Aeronautics and Space Administration(NASA)and European Space Agency(ESA)for subsequent lunar and deep space exploration missions.The techniques of rapid trajectory determination of lunar take-off and orbit entry,as well as high precision and remote guidance of lunar orbit rendezvous and docking can lay a technological foundation for the future manned lunar exploration missions and planetary sampling and return missions.

A Low Power Non-Volatile LR-WPAN Baseband Processor with Wake-Up Identification Receiver

The paper proposes a low power non-volatile baseband processor with wake-up identification(WUI) receiver for LR-WPAN transceiver.It consists of WUI receiver,main receiver,transmitter,non-volatile memory(NVM) and power management module.The main receiver adopts a unified simplified synchronization method and channel codec with proactive Reed-Solomon Bypass technique,which increases the robustness and energy efficiency of receiver.The WUI receiver specifies the communication node and wakes up the transceiver to reduce average power consumption of the transceiver.The embedded NVM can backup/restore the states information of processor that avoids the loss of the state information caused by power failure and reduces the unnecessary power of repetitive computation when the processor is waked up from power down mode.The baseband processor is designed and verified on a FPGA board.The simulated power consumption of processor is 5.1uW for transmitting and 28.2μW for receiving.The WUI receiver technique reduces the average power consumption of transceiver remarkably.If the transceiver operates 30 seconds in every 15 minutes,the average power consumption of the transceiver can be reduced by two orders of magnitude.The NVM avoids the loss of the state information caused by power failure and energy waste caused by repetitive computation.

Chinese TT＆C Network Capable of Connecting with the International TT＆C Networks

On December 19, the Chinese and French TT&C networks conducted a successful cooperation in jointly tracking and measuring a French experimental satellite. During ChinaFrance TT&C networking the three ground monitoring stations of the Xi'an Satellite Control Center (XSCC)accurately completed locating and acquisition of the satellite and transmitted data in the 3-circle relay tracking and measuring,