Subjects: Geosciences >> Space Physics submitted time 2017-01-22
Abstract： In order to ensure quantum science experiments can be developed smoothly, a high data rate two-way link for Space-Ground microwave communication must be established. Via following the study on Consultative Committee for Space Data Systems (CCSDS) and taking into account the scientific requirements of microwave communication link for quantum science experiment satellite, the physical layer hardware architecture and modulation/demodulation algorithm of microwave communication link for the satellite are presented.The uplink modulation type of the microwave communication link is SRRC-OQPSK, which accord with CCSDS spectrum standard. The specification of uplink data rate is 1.024Mbps,. The downlink modulation type of the microwave communication link is SRRC-OQPSK/GMSK, and the data rate is 4Mbps. By compatible tests with several ground stations, we find that the sensitivity of carrier acquisition is superior to -100dBm, and AGC ability is greater than 43dB. Moreover, the bit error rate of actual transmission is superior to 1�0-9 as the received signal level is equal to -96 dBm. The measured results indicate that the physical layer design scheme of microwave communication link meets the requirements of space quantum science experiments.
Peer Review Status:
Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： A new bi-phase modulation (BPM) pulse UWB transmitter manufactured by discrete components is designed. The transmitter consists of mono-polar sub-nanosecond pulse generator, bipolar pulse generator,and high speed microwave switch. The transmitter transmit positive and negative pulses when controlled by clock signal as well as data ' 1' and data ' 0',respectively. Experimental results show that the generated pulse width is below 400 ps,the bandwidth is more than 1. 5 GHz,and the data rate is up to 50 Mbps. It can be used in the pulse UWB (ultrawideband) communication systems.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： Combining with Nakagami fading channel model,Rayleigh channels and Rician channels were analyzed between sounding rockets and ground station during the flight course.It takes an example of a variable modulation system with four types of modulations,including BPSK,QPSK,16QAM and 64QAM,and proposes a method to acquire the optimum signal-to-noise ratio switch threshold,according to different elevation angles of ground receiving station. The optimum threshold could maximize the throughput,while satisfying BER goal.Furthermore, the paper analyzes and compares the throughput difference with optimum signal-to-noise ratio switch threshold,BPSK modulation method and constant-BER signal-to noise ratio threshold. The results show that,by adoption of the optimum threshold,system throughput is 3.89 times and 1.043 times higher than the other two methods,respectively. The results could provide reference and basis for the application of variable modulation technology into practical sounding rockets projects.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-04-22
Abstract：针对数传、测距一体化的调制方式高斯最小频移键控复合伪码测距(Gaussian minimum shift keying+pseudo-noise,GMSK+PN)信号的信噪比估计,提出了一种精度较高、复杂度较低的快速算法。该算法采用层状结构分解的方式,将信号分解为若干信号单元,对每一个分解的信号单元进行功率分配计算或信噪比估计,最后快速准确地计算出整个信号的信噪比。信噪比在1~13dB之间时,估计误差小于0.5dB。利用Simulink仿真工具,验证了该算法的有效性。
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-04-22
Abstract： For the small satellites formation flying， the distance between satellites must be determined and an adequate inter-satellites communication medium must be used to transmit the science data. In order to minimize device complexity， this paper studied a system capable of simultaneously transmitting high rate telecommunication and ranging. through simulations by Simulink in different ranging modulation index， obtained the bit error rate of telecommunication data. By analyzing the characteristics of GMSK+PN signal， an effective demodulation scheme for GMSK+PN is developed by this paper.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-04-22
Abstract： In order to save channel resources， asynchronous digital multiplexer， which can multiplex different rate， different burst time slot digital source， has been widely applied. Aims to reduce the maximum extent possible source packet data transmission delay， improve channel utilization， design scheme of a greedy asynchronous dynamic digital multiplexer is proposed. The priority scheduling strategy of sources is given too. Two kinds of multiplex model are described by hardware description language. Simulations for greedy dynamic multiplexer and virtual channel multiplexer， under the condition of different physical frame length and two source model， have been carried out by Modelsim. The simulation results show that， for the average transmission delay and delay jitter， the greedy dynamic multiplexing is superior to the virtual channel multiplexing， and is more effective in saving resource of source cache.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-04-22
Abstract： In order to ensure the success of space exploration mission， the small satellite formation requires reliable inter-satellite communications. Based on 802.11， small satellite formation network protocol architecture was designed. Firstly， network protocol stack was built according the OSI stack layers， the key parameters of physical layer and data link layer of was tuned to meet the requirement of inter-satellite communication， the network layer routing protocol was analysed， and then the satellite network formation model was made and analysed. With the aid of the network simulation tool NS3， performance of four typical formation network was simulated. Simulation results show that the network protocol architecture ensures inter-satellite communications based on 802.11. Although network performance varies greatly in different flyning formations， it can be adjusted according to the task requirements.
Peer Review Status:Awaiting Review
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