Abstract
This paper provides an overview of recent results of a design, development and performance evaluation study of satellite gateways to receive and manage the traffic from a large population of uncoordinated user terminals. In particular, direct satellite access scenarios for machine-to-machine communications and the Internet of Things have been targeted. Tests were carried out in a representative laboratory environment emulating realistic system scenarios. Performance results, as presented in this paper indicate that the proposed gateway architecture, based on an efficient access protocol, is capable of managing a very high number of uncoordinated terminals transmitting short messages with a low duty cycle. The applicability of the proposed solution to both geostationary and non-geostationary satellite systems has also been examined. The key concept of the gateway is based on a novel receiver architecture that implements the linear minimum mean square error (MMSE) spread spectrum signal detection and successive interference cancellation techniques. The receiver uses features such as a multi-stage detector together with a robust preamble detection. The end-to-end solution includes also the use of a new waveform with a quasi-constant envelope at the terminal to modulate and transmit data packets to be received and detected by the gateway via a satellite link.
Highlights
In the past decade, the ever-growing demand for machine-to-machine (M2M) communications and the emerging market of the Internet of Things (IoT) has led to a high research interest and industry development of efficient protocols for collecting data from a large and uncoordinated population of user terminals via satellite.A direct satellite access can play a key role in collecting data from remote areas for applications such as the IoT, and M2M
This feature enables a cost reduction of the transmitters by improving the power efficiency. It allows the non-linear power amplifiers to operate closer to the saturation point without distorting the transmitted signal. This scheme provides a sharper power spectrum in the presence of non-linearity at the transmitter, much lower spectral side lobes, in order to better exploit the available bandwidth especially in the case of narrowband channels, Implementation of the minimum mean square error (MMSE) receiver based on the multi-stage detector/despreader (MSD) approximation [9], which ensures a better performance when coupled with the quadrature phase shift keying (QPSK) modulation at the transmitter, Implementation of a more robust preamble searching and detection algorithm, in order to deal with harsher channel conditions (e.g., larger frequency offsets and Doppler rate values, typical of Low Earth Orbit (LEO) or Medium Earth Orbit (MEO) satellites scenarios)
The measured packet loss ratio (PLR) was compared in the case of no power randomization—where all the bursts were received with the same carrier-to-noise ratio (C/N) values equal to the target value listed in Table 3—and in the case of a burst power randomized in a 5 dB range, i.e., for every burst a random number was drawn from a uniform distribution between 0
Summary
The ever-growing demand for machine-to-machine (M2M) communications and the emerging market of the Internet of Things (IoT) has led to a high research interest and industry development of efficient protocols for collecting data from a large and uncoordinated population of user terminals via satellite. It allows the non-linear power amplifiers to operate closer to the saturation point without distorting the transmitted signal This scheme provides a sharper power spectrum in the presence of non-linearity at the transmitter, much lower spectral side lobes, in order to better exploit the available bandwidth especially in the case of narrowband channels, Implementation of the MMSE receiver based on the multi-stage detector/despreader (MSD) approximation [9], which ensures a better performance when coupled with the QPSK modulation at the transmitter, Implementation of a more robust preamble searching and detection algorithm, in order to deal with harsher channel conditions (e.g., larger frequency offsets and Doppler rate values, typical of Low Earth Orbit (LEO) or Medium Earth Orbit (MEO) satellites scenarios). Matrices are in upper case bold while scalar variables are either in upper or lower case italic
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