Flying on the mission orbit at the Earth-Moon L2, the Chang'e-4 relay sattellite carried out the experiment of regenerative pseudo-random code ranging, during which the regenerative pseudo-random code ranging and the sidetones ranging were both utilized. The regenerative pseudo-random code ranging data and the side tone ranging data of the Chang’E 4 relay satellite, which are flying on the mission orbit at the Earth-Moon L2 libration point, are used to evaluate their orbit determination accuracies. The results show that the RMS of the regenerative pseudo-random code ranging data is one order of magnitude better than that of the sidetones ranging data, and the orbit determination and prediction accuracy of the regenerative pseudo random code ranging data is twice as good as that of the side tone ranging data. This is a reliable reference for the application of regenerative pseudo-random code ranging in the future Chinese deep space exploration missions.

According to the interferometric observation data of Jiamusi deep space station and Kashi deep space station of China deep space network during the mission of Chang'E-4 prober, the orbit determination accuracy of real-time data and post-correction data respectively combined with the USB data is analyzed. The difference between the Earth Moon transfer section and the precise orbit is 100 meters, and the difference between the ring moon section and the precise ephemeris is 10 meters. At the same time, the influences of VLBI data weight setting on the orbit accuracy is analyzed. In view of theChina deep space network in subsequent deep space missions such as Chang’E 5, a time-sharing acquisition mode is proposed to reduce the amount of VLBI data. The influence of this mode on orbit accuracy is analyzed by using the measured VLBI data of Chang’E 4 prober. The results show that the real-time data accuracy of China’s deep space network VLBI data has reached the accuracy of post-correction data, which can support the follow-up deep space exploration tasks in China. At the same time, for 2 to 3 hours per day of common viewing time of two stations, in the time-sharing acquisition mode, the total 20 minutes per day data and 1 minute acquisition step can ensure that the orbit accuracy does not decrease.

China’s deep space interferometry system has participated in orbit measurement for the Chang’E-5 mission officially, which has provided high-precision angular position information. The tropospheric delay hybrid model was proposed to ensure the accuracy of real-time interferometry. Using the non-continuous tracking technology, fast intercontinental interferometry was carried out for the first time, which provided high-precision angular position with the advantage of baseline length. The performance was evaluated based on the orbit measurement results of Chang’E-5 probe. These results show that the deep-space interferometry system has played an important role in the fast orbit determination.

The TT&C (Tracking Telemetry and Command) resources are usually limited for the deep space exploration mission of micro-nano satellites. It is necessary to analyze the orbit determination accuracy under the limited resource of TT&C. The orbit determination precision of Longjiang-2 lunar microsatellite is analyzed. Longjiang-2 microsatellite only has USB orbital measurement data, and the TT&C resources in the lunar phase are relatively tight. There are two stations are used to track the Longjiang-2 satellite every day,and a total of about 3-4 hours of orbital measurement data is available. Firstly,the Longjiang-2 mission is introduced and the factors which have effect on orbit determination are presented. Secondly, the dynamical model is given. The orbit determination precision of earth-moon transfer orbit is analyzed. Lastly,the effects of perturbative force, wheeloff loading and data arc length are studied and then the orbit determination strategy is proposed. The orbit determination precision of lunar orbit is given. The conclusions can provide useful reference for the future deep space exploration mission of micro-nano satellites.

The very long baseline interferometry (VLBI) in China Deep Space Net (CDSN) mainly uses the classical model for tropospheric delay modification in real-time processing, while the measuring accuracy is constrained by the model performance. In view of this problem, an accurate regional tropospheric delay model is constructed. Firstly, the correction factor of Saastamoinen zenith tropospheric delay is determined by comparison of measured and estimated value, which leads to the zenith delay estimation bias reducing to about 0.9 ps from 1.24 ns. Secondly, in order to overcome the restriction of meteorological data, the UNB3m model with height correction is introduced to construct reginal atmospheric parameter estimation model, and results show that the estimation bias of atmospheric pressure, temperature and vapor pressure is about 3.9 mbar, 6.7 K, 0.63 mbar, respectively, moreover, the difference of zenith delay is about 14 ps when the measured and modeled meteorological data are as input, which enhances the real-time performance of zenith delay estimation. Finally, the characteristics of Niell mapping function are analyzed and the factor a in dry function is confirmed as the key parameter, whose optimal value is obtained by least-square processing. The measured data processing results show that the tropospheric delay estimation bias is about 0.3 ns when the elevation angle is 10°, which decreases nearly an order compared with the original model. Furthermore, the orbit determination error of Chang’E-4 detector is basically identical when using measured and the proposed tropospheric delay model, both results are significantly better than that of the original model. The regional model proposed here is of meteorological data independence and of high accuracy, which improves the support ability of VLBI system in CDSN for real-time orbit determination.

Orthogonal frequency division multiplexing (OFDM) modulation-based broadband power line communication technology provides efficient and reliable information transmission for the smart grid, smart home and the “last mile”. However, OFDM is highly sensitive to the synchronous error, which may reduce its performance. To solve this problem, the polyphase sequence was chosen as the primary synchronization signal multi-user frame structure and a new polyphase sequence family (for user group of search) was used as the main sync signal. In order to combat inter-user interference caused by other users of training sequence, he design of the sequence set not only to take into account each sequence with better autocorrelation properties, that is a higher peak-to-peak sidelobe ratio, also requires a good cross-correlation characteristics. In multi-user systems, different users use different sequences as the synchronization preambles and this does not increase the system complexity. On the authors’ self-made hardware platform the proposed synchronization solution was realized, and the experiment and simulation results show that the synchronization design is more suitable for power line environment.

The model of OFDM(Orthogonal Frequency Division Multiplexing) system based on power line communication is introduced and the channel and noises of power line communication are modeled. Since the synchronization training sequence with repeated structure is applied, there are three virtual sub-carriers between every two data-loaded adjacent sub-carriers in frequency-domain, which can be used in data-aided estimation. The guard virtual sub-carriers at both ends of OFDM system in frequency-domain are used in blind SNR(Signal to Noise Ratio) estimation. Simulative results show that, in data-aided estimation, the precision of the proposed algorithm is similar to that of Boumard algorithm if the actual SNR is relatively high, otherwise it is higher than that of MMSE algorithm or Boumard algorithm; in blind SNR estimation, it is higher than that of M2M4 algorithm in most conditions.

OFDM (orthogonal frequency division multiplexing)-based broadband power line communication offers reliable data transmission solution for smart grid and the “last mile” question. This paper presents a design and implementation on timing synchronization algorithm for PLC. A polyphase sequences sets based preamble is proposed which provide not only better merit factor and peak to average power ratio but also minimum interference caused by other user's preamble. We evaluate the performance of the proposed scheme using a power line channel simulation model which contains multipath propagation, highly varying path loss and disturbance by impulse noise. At last, we implement the hardware system and test the proposed timing synchronization scheme in real office environment.

To achieve high-speed power line carrier communication in smart grid, OFDM technology is a very good choice. But the high peak-to-average power ratio (PAPR) of OFDM is a bottleneck of its practical application, and it will bring a range of problems, such as increasing the complexity of A/D conversion and reducing the effectiveness of RF power amplifiers. In this paper, TI's C6713 DSP chip is used to achieve two major algorithms of reducing peak-to-average power ratio of OFDM system, which are the clipping method and the selective mapping method. This work has some practical significance on the implementation of OFDM system in the power line carrier communication.

Adaptive orthogonal frequency division multiplexing(AOFDM) offers reliable data transmission solution for medium voltage powerline communication with low SNR and frequency selective attenuation. Signal-to-noise ratio (SNR) estimator is a key decision parameter in adaptive transmission. In this paper, a virtual carrier based SNR estimation algorithm is proposed. Algorithm can be applied to two cases; one is for data-aided estimation and the other for blind estimation. SNR estimator use virtual carrier in synchronization train sequence or virtual carrier generated by oversampling. Second-moments of received signal is calculated to deduce the result. The performance is compared with other algorithms through Monte-Carlo simulation. The result shows that it is a feasible algorithm for MV powerline communications.

Orthogonal Frequency Division Multiplexing (OFDM) based broadband power line communication provide better information exchange scheme for smart grid. This paper presents and analysis the design and implementation procedure of timing synchronization algorithm for OFDM system, on the TMS320C6713 Digital Signal Processor of TI, in the Low Voltage power line communication (PLC). Synchronization algorithm is one of most essential algorithms in the OFDM based broadband power line communication system. Measure based LV power line channel model was given first. Then, our synchronization method is introduced to against horrible noise and interference in LV power line channel. Preamble with special structure is used to enhance the performance of algorithm. Finally the performance on the real PLC situation is listed. The results confirmed that it is a feasible synchronization solution for power line communications.

The emerging smart grid requires more reliable communication technology. This paper presents a coded adaptive BFSK PLC solution for medium voltage power line communication with low SNR and frequency selective attenuation. The measure based powerline channel model in China is given first, then the data transmission system is proposed for MV PLC. Three centre frequencies is used to optimize data transmission, the system changes centre frequency adaptively according to the SNR estimation results. The differential demodulation receiver is analyzed include decode algorithm and other key algorithms. Finally, we implements the system on ADSP-bf533. The results confirmed that it is a feasible system solution for MV power lines.

In this paper, on the basis of the analysis of power line channel characteristic,we firstly build a power line channel mode. And then, we elaborate the spectrum theory and its main performance indexes. At last, the direct sequence spread spectrum communication system is build by MATLAB/Simulink using the power line channel mode. The simulation results prove that the Spectrum-spread Technology can be used in Power Line Communication.