A comparison of digital transmission techniques under multichannel conditions at 2.4 GHz in the ISM BAND

In order to meet the observation quality criteria of micro-UAVs, and particularly in the context of the « Trophée Micro-Drones », ISAE/SUPAERO is studying technical solutions to transmit a high data rate from a video payload onboard a micro-UAV. The laboratory has to consider the impact of multipath and shadowing effects on the emitted signal. Therefore fading resistant transmission techniques are considered. This techniques paper have to reveal an optimum trade-off between three parameters, namely: the characteristics of the video stream, the complexity of the modulation and coding scheme, and the efficiency of the transmission, in term of BER

Spread spectrum techniques for indoor wireless IR communications

Multipath dispersion and fluorescent light interference are two major problems in indoor wireless infrared communications systems. Multipath dispersion introduces intersymhol interference at data rates above 10 Mb/s, while fluorescent light induces severe narrowband interference to baseband modulation schemes commonly used such as OOK and PPM. This article reviews the research into the application of direct sequence spread spectrum techniques to ameliorate these key channel impairments without having to resort to complex signal processing techniques. The inherent properties of a spreading sequence are exploited in order to combat the ISI and narrowband interference. In addition, to reduce the impact of these impairments, the DSSS modulation schemes have strived to be bandwidth-efficient and simple to implement. Three main DSSS waveform techniques have been developed and investigated. These are sequence inverse keying, complementary sequence inverse keying, and M-ary biorthogonal keying (MBOK). The operations of the three systems are explained; their performances were evaluated through simulations and experiments for a number of system parameters, including spreading sequence type and length. By comparison with OOK, our results show that SIK, CSIK, and MBOK are effective against multipath dispersion and fluorescent light interference becausc the penalties incurred on the DSSS schemes are between 0-7 dB, while the penalty on OOK in the same environment is more than 17 dB. The DSSS solution for IR wireless transmission demonstrates that a transmission waveform can he designed to remove the key channel impairments in a wireless IR system

Characterization of causes of signal phase and frequency instability Final report

Characteristic instabilities in phase and frequency errors of reference oscillator

Introduction to Random Signals and Noise

Random signals and noise are present in many engineering systems and networks. Signal processing techniques allow engineers to distinguish between useful signals in audio, video or communication equipment, and interference, which disturbs the desired signal. With a strong mathematical grounding, this text provides a clear introduction to the fundamentals of stochastic processes and their practical applications to random signals and noise. With worked examples, problems, and detailed appendices, Introduction to Random Signals and Noise gives the reader the knowledge to design optimum systems for effectively coping with unwanted signals.\ud \ud Key features:\ud • Considers a wide range of signals and noise, including analogue, discrete-time and bandpass signals in both time and frequency domains.\ud • Analyses the basics of digital signal detection using matched filtering, signal space representation and correlation receiver.\ud • Examines optimal filtering methods and their consequences.\ud • Presents a detailed discussion of the topic of Poisson processed and shot noise.\u

Spatial Characteristics of Distortion Radiated from Antenna Arrays with Transceiver Nonlinearities

The distortion from massive MIMO (multiple-input--multiple-output) base stations with nonlinear amplifiers is studied and its radiation pattern is derived. The distortion is analyzed both in-band and out-of-band. By using an orthogonal Hermite representation of the amplified signal, the spatial cross-correlation matrix of the nonlinear distortion is obtained. It shows that, if the input signal to the amplifiers has a dominant beam, the distortion is beamformed in the same way as that beam. When there are multiple beams without any one being dominant, it is shown that the distortion is practically isotropic. The derived theory is useful to predict how the nonlinear distortion will behave, to analyze the out-of-band radiation, to do reciprocity calibration, and to schedule users in the frequency plane to minimize the effect of in-band distortion