1,720,986 research outputs found
Iterative carrier synchronization in the absence of distributed pilots for low SNR applications
Full text linkWe consider the advanced modulation and coding schemes used in CCSDS (Consultative Committee for Space Data Systems) standards for deep space telemetry and telecommand. They are based on a powerful turbo or low-density parity check (LDPC) outer code and binary modulation formats that, for those schemes foreseen to be employed at the lowest baud rates, may contain an unsuppressed carrier to help synchronization. In this paper, we face the problem of carrier phase synchronization for these modulation and coding schemes
On the use of PN Ranging with High-rate Spectrally-efficient Modulations in Satellite Payload Telemetry Links
Full text linkPseudo Noise (PN) ranging is a ranging technique that has been recently introduced in near-Earth space research (SR) missions. For these, at the state-of-the-art, the PN ranging signal is combined with a high-rate telemetry stream binary modulated in phase. The coupling of the two, together with the 10 MHz bandwidth constraint imposed for this class of missions, translates into a data rate bound of approximately 10 Mbps. The purpose of this article is to prove the feasibility of overcoming the current data rate limitation by defining a communication architecture that foresees the coupling of the PN ranging signal with a high-order modulated telemetry stream. To achieve the goal, we study the feasibility of pairing the PN ranging with filtered high-order modulations in satellite payload telemetry links and investigate the simultaneous demodulation of the telemetry stream while tracking the ranging sequence. Accordingly, we design a receiver scheme that is able to perform a closed-loop parallel cancellation of the ranging and the telemetry signal, reciprocally. From our analysis, we find that the non-constant envelope property, characterizing the considered modulation set, causes an additional jitter on the PN ranging timing estimation that, on the other hand, can be controlled and reduced by properly sizing the receiver loop bandwidth, without limiting the timing synchronization dynamic. Our study proves that the use of filtered high-order modulations combined with PN ranging outperforms the state-of-the-art in terms of spectral efficiency and achievable data rate while having comparable ranging performance
C) for Space Missions
Full text linkThis paper presents a tutorial on the Tracking, Telemetry, and Command (TT&C) for spacecraft and satellite missions. In particular, it provides a thorough summary of the design of the TT&C, starting from elementary system aspects and going down to the details of the on-board TT&C subsystem design, its units, and the physical layer. The paper is then complemented with a description of emerging TT&C techniques and technologies, the standardization framework, and practical examples of actual spacecraft design of European space missions. The here-presented tutorial is thought for professionals (also in other telecommunication engineering fields) willing to face the challenges and state-of-the-art of the TT&C, and know more about this fundamental function that allows us to control and monitor our spacecraft on a daily basis
Adaptive Rate-Maximizing Channel-Shortening for ISI Channels
No full textWe consider detection over intersymbol interference channels that are unknown at the receiver. For such a kind of systems, we consider an alternative approach to the design of a reduced-complexity receiver based on channel shortening without the explicit estimation of the channel impulse response. The proposed solution allows a simplification of the receiver architecture and a faster convergence for channels with a long memory and a few number of poles
Optimal Transmit Filters for ISI Channels under Channel Shortening Detection
No full textWe consider channels affected by intersymbol interference with reduced-complexity, mutual information optimized, channel-shortening detection. For such settings, we optimize the transmit filter, taking into consideration the reduced receiver complexity constraint. As figure of merit, we consider the achievable information rate of the entire system and with functional analysis, we establish a general form of the optimal transmit filter, which can then be optimized by standard numerical methods. As a corollary to our main result, we obtain some insight of the behavior of the standard waterfilling algorithm for intersymbol interference channels. With only some minor changes, the general form we derive can be applied to multiple-input multiple-output channels with intersymbol interference. To illuminate the practical use of our results, we provide applications of our theoretical results by deriving the optimal shaping pulse of a linear modulation transmitted over a bandlimited additive white Gaussian noise channel which has possible applications in the faster-than-Nyquist/time packing technique
A multi-sample discrete-phase BCJR algorithm for phase noise channels
Full text linkIn this paper, we consider channels affected by Wiener phase noise and derive a detection algorithm that exploits oversampling at the receiver for tracking better the phase noise variations. The resulting algorithm is a multi-sample discrete-phase BCJR that outperforms receivers using a single sample per symbol and maximizes the achievable information rate over phase noise channels. Finally, we assess the suitability of the multi-sample discrete-phase BCJR for performing iterative detection and decoding with standard codes
Digital PLLs for phase noise channels: a concept based on the Tikhonov distribution
Full text linkWe explore the concept of a digital phase-locked loop (PLL) of the first type, derived as an alternative solution to Kalman's estimation problem by employing the Tikhonov distribution rather than the traditional Gaussian model.
The resulting Tikhonov PLL is a complex-valued nonlinear filter that is simple to implement and demonstrates interesting features in channels affected by strong phase noise. We present a comparative analysis including the classical PLL and Kalman filter to highlight the strengths of the Tikhonov PLL in such contexts
Channel Shortening for Nonlinear Satellite Channels
No full textWe design of an efficient channel shortener for nonlinear satellite channels. When the memory of the channel is too large to be taken into account by a full complexity detector, excellent performance can be achieved by properly filtering the received signal followed by a reduced-state detector. This letter derives closed-form expressions for the front-end filter and the target response of the reduced-state detector
Data detection method and data detector for signals transmitted over a communication channel with inter-symbol interference
No full textA data detection method, having the steps of: a. receiving a signal transmitted over a communication channel, the signal being representative of at least a stream of interfering symbols xk, each representing one or more bits of a transmitted message; b. filtering the received signal through at least a filter bank having at least a first filter representative of a linear response of the channel and a second filter representative of a non-linear response of the channel, and sampling the filtered signals at the symbol rate, thus obtaining respective sequences of filtered samples rk (1) rk (3); and c. jointly computing the a posteriori probabilities of N>1 consecutive symbols xk. A data detector for carrying out such a method, and a method of transmitting data over a nonlinear channel, optimizing spectral efficiency when data detection is performed using such a method is also provided
Advanced techniques for spectrally efficient DVB-S2X systems
No full textWe investigate different techniques to improve the spectral efficiency of systems based on the DVB-S2 standard, when the transmitted signal bandwidth cannot be increased because it has already been optimized to the maximum value allowed by transponder filters. We will investigate and compare several techniques involving different sections of the transceiver scheme. The techniques that will be considered include the use of advanced detection algorithms, the adoption of time packing, and the optimization of the constellation and shaping pulses. The low-density parity-check codes recently proposed for the evolution of the DVB-S2 standard will be considered, as well as the adoption of iterative detection and decoding. Information-theoretical analysis will be followed by the study of practical modulation and coding schemes. Copyright © 2015 John Wiley & Sons, Ltd
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