The 1/f family of fractal random processes model a truly extraordinary range of natural and man-made phenomena, many of which arise in a variety of signal processing scenarios. Yet despite their apparent importance, the lack of convenient representations for 1/f processes has, at least until recently, strongly limited their popularity. In this paper, we demonstrate that 1/f processes are, in a broad sense, optimally represented in terms of orthonormal wavelet bases. Specifically, via a useful frequency domain characterization for 1/f processes, we develop the wavelet expansion's role as a Karhunen-Loeve-type expansion for 1/f processes. As an illustration of potential, we show that wavelet based representations naturally lead to highly efficient solutions to some fundamental detection and estimation problems involving 1/f processes

Wavelet-based representations for the 1/f family of fractal processes : Fractals in electrical engineering

Fast acquisition in space telemetry and telecontrol communication system is challenged significantly by the high dynamic and low signal-to-noise ratio. Increasing the dwell time to obtain better acquisition sensitivity, based on two-dimensional time-frequency search, is impossible because of resource limitation in receiver. To tackle these problems, this study proposes a two-stage differential acquisition (TSDA) algorithm. The differential coherent integration is employed by the first stage of TDSA to extend integration time, during which keystone transform and fast Fourier transform are used to compensate the linear code phase drift and obtain high accumulation gain. The carrier-frequency offset is estimated in terms of the code phase difference between the two parts of received signal divided by the second stage of TSDA in which the two-dimensional searching process is avoided. The proposed TSDA algorithm and the traditional acquisition methods are compared under the same acquisition time and typical parameters of S-band space telemetry and telecontrol communication system. Simulation results demonstrate that the proposed TSDA algorithm attains a higher acquisition probability and better acquisition sensitivity than the traditional acquisition methods.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-com.2016.0996

Long-term integration based on two-stage differential acquisition for weak direct sequence spread spectrum signal

To acquire weak signals GPS reiceiver requires longer observation intervals to accumulate sufficient energy from the signal of intermediate frequency. Full bit method avoids effects of the data bit modulation thereby preserves a longer coherent integration yet consumes too much time and resources. In this paper, an enhanced full bit method is proposed, which aims at speeding up the full bit acquisition remarkably and maintain the superiority in receiving weak signals. All the acquisitions are based on the constant false alarm rate (CAFR) criteria. However, it is difficult to acquire the theoretical detection probability of the full bit method. Thus, an approach to it is given in this paper, and as a standard compared with the enhanced full bit results. The simulation results show that the new method increases the speed of acquisition by 28% on the average; the detection probability of the new method stay close to the full bit method; when non-coherent integration number equals 40, signals whose C/N 0 (carrier-to-noise ratios) are as low as 19 dB·Hz can be acquired.

Enhanced full bit acquisition algorithm for software GPS receiver in weak signal environment

https://cyberleninka.org/article/n/212737.pdf

Weak signal acquisition enhancement in software GPS receivers – Pre-filtering combined post-correlation detection approach

In high dynamic circumstance, high-speed relative movement between spacecraft and receiver causes not only the carrier Doppler frequency offset but also the code-frequency offset. To tackle the problem of linear code phase drift in fast acquisition, this paper proposes a novel acquisition algorithm based on compensating the code-frequency offset. In the proposed algorithm, the carrier Doppler frequency offset is searched by fixed frequency step, then the code-frequency offset compensation for each dwell in Tong detector can be calculated to eliminate the impact of code phase drift. Furthermore, to reduce the computational complex and hardware resources, a folding structure is adopted in the parallel code phase search. Theoretical and simulation results verify the effectiveness of the proposed algorithm.

A code Doppler compensation algorithm in acquisition for high dynamic spread spectrum signals

Considering autonomous and AD-HOC networking of AFF, such as topology, multiple access mode, integrated
mode of inter-satellite communication and measurements, and data transfer protocol, are presented and studied in this
paper. Inter-satellite non-coherence spread spectrum ranging via full-duplex asynchronous communication link of
CCSDS Proximity-1 transfer frame is deeply researched, and Sufficient simulation and engineering experiments are
implemented and plenty of results are obtained, which show that the integrated mode of intra-satellite communication
and measurement achieves excellent precision, integrates multiple functions in one device with more effective
utilization ratio of channel in radio link. The production of principles and technologies in this dissertation has many
academic and engineering values, can be used in many fields in the future.

The study on integrated mode of inter-satellite communication/measurement in autonomous formation flyer

Considering the requirements for the lunar rover positioning in the future lunar reconnaissance, several methods of lunar rover positioning are compared and analyzed firstly, and a new method is proposed in this paper according to the characters of the lunar rover activities, which uses the asynchronous transmission incoherent spread-spectrum communication/ranging system, and dual-UHF-antenna short-baseline carrier coherent angle detection method, to achieve high accuracy of ranging and azimuth angle results, and can figure out the rectangular coordinates position and vector of the lunar rover. The autonomous and real time precise positioning of the lunar rover over the whole activities on the moon can be realized with the use of the new method proposed here.

Study for rover position systems based on lunar lander-robotic rover communication link in CE-3 mission

Gravity field measurement for the interested planets and their moos in solar system, such as Luna and Mars, is one important task in the next step of deep-space mission. In this paper, Similar to GRACE mission, LLSST and DOWR technology of common-orbit master-slave satellites around task planet is inherited in this scheme. Furthermore, by inter-satellite 2-way UQPSK-DSSS link, time synchronization and data processing are implemented autonomously by master-slave satellites instead of GPS and ground facilities supporting system. Conclusion is derived that the ISL DOWR based on 2-way incoherent time synchronization has the same precise level to GRACE DOWR based on GPS time synchronization. Moreover, because of inter-satellite link, the proposed scheme is rather autonomous for gravity field measurement of the task planet in deep-space mission.

The scheme of LLSST based on inter-satellite link for planet gravity field measurement in deep-space mission

Phase noise presents a treatment of the problem of charactering, analyzing and measuring short-term frequency instabilities of ultrastable oscillation as well as of loop-controlled oscillation As yet no entirely satisfactory framework has been described for such noise, wavelet bases are used to provide a construction for phase noise In general, the most widely used model for oscillators phase noise is power law noise model This paper first addresses the conception of phase noise and introduces several general methods to generate phase noise Then, the theory of orthonormal wavelet expansion is presented We develop the wavelet expansion as a Karhunen-Loeve expansion for power law noise After that, the generation of power law noise which is based on the orthonormal wavelet expansion is introduced specifically Finally, the simulated phase noise both in time domain and frequency domain are obtained

Xue Li

Papers

Enhanced full bit acquisition algorithm for software GPS receiver in weak signal environment

The study on integrated mode of inter-satellite communication/measurement in autonomous formation flyer

Study for rover position systems based on lunar lander-robotic rover communication link in CE-3 mission

The scheme of LLSST based on inter-satellite link for planet gravity field measurement in deep-space mission

The generation of phase noise based on wavelet transform