Satellite television is probably most used satellite technology today. One of the biggest providers is the ASTRA system of geostationary satellites. Television satellite standard widely used is the DVB-S which establi...
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ISBN:
(纸本)9781509000531
Satellite television is probably most used satellite technology today. One of the biggest providers is the ASTRA system of geostationary satellites. Television satellite standard widely used is the DVB-S which established a unified standard for a satellite transmission accepted both by customers as well as the industry. Standard DVB-S2 has improvements in efficiency (bits/Hz) and adaptive as well as variable coding and modulation. While DVB-S digital satellite standard has constant modulation and coding, standard DVB-S2 can adopt both modulation and coding depending on the weather conditions, channel interference, etc. Both technologies still co-exist today. This paper analyses the parameters of both DVB-S and DVB-S2 standards such as bit error rate, modulation error rate, signal to noise ratio and signal level in different weather conditions. The measurements were performed in clear sky, clouds and rain conditions. They included extensive coverage of digital video signal in thirty different weather conditions. The results showed that DVB-S2 standard performs similar to DVB-S standard in clear sky conditions as well as cloudy weather, while for rain DVB-S2 excels. Bit error rate for DVB-S2 standard stayed the same regardless of weather conditions and about four orders of magnitude compared to DVB-S standard.
In this article there is presented a new method for spectral efficiency optimized transmission in a broadcast network, in which besides maximizing exploitation of network's resources there will be provided physica...
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ISBN:
(纸本)9781467328210;9781467328203
In this article there is presented a new method for spectral efficiency optimized transmission in a broadcast network, in which besides maximizing exploitation of network's resources there will be provided physical layer security for each user's data, i.e., transmission scenario is designed in a way that data of each user just is detected at the corresponding receiver with a proper error probability and error of detection at the unintended receivers is acceptably high. A bit error rate (BER) constraint for each user and an average power constraint for the transmitter are provisioned while a weighted sum of spectral efficiencies is maximized. In the proposed method there is used discrete rate adaptation through adaptivemodulation and coding based on signal to noise ratio (SNR) of the links. Accurate and approximate solutions are presented to solve the optimization problem. The approximate solution besides having little difference with the accurate solution in the performance view has acceptable complexity. Numerical evaluation signifies that considering security constraint results in a little decrease in achievable rates, but in turn it helps to keep confidentiality of the information.
A channel allocation (CA) method is proposed that allocates frequency channels to the cells of a mobile network taking into account the frequency reuse pattern employed and the interference caused by neighboring TV br...
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A channel allocation (CA) method is proposed that allocates frequency channels to the cells of a mobile network taking into account the frequency reuse pattern employed and the interference caused by neighboring TV broadcasters. The proposed CA is optimal in the sense that it maximizes channel utilization and at the same time achieves a very high level of fairness among the network users. The proposed method is implemented employing a Genetic Algorithm based iterative scheme. Due to its reduced computational complexity, the practical application of the proposed CA scheme is characterized by short completion time. To increase granularity the method can be extended to incorporate adaptive coding and modulation. It can also handle uncommon traffic conditions by dynamically reallocating channels to emergency cells.
Spectrum Sensing (SS) and Power Control (PC) have been two important concepts of Cognitive Radio (CR). In this paper, a mechanism combining these two topics is proposed to allow a cognitive user, also called Secondary...
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ISBN:
(纸本)9781479958931
Spectrum Sensing (SS) and Power Control (PC) have been two important concepts of Cognitive Radio (CR). In this paper, a mechanism combining these two topics is proposed to allow a cognitive user, also called Secondary User (SU), to access the frequency band of a Primary User (PU) operating based on an adaptive coding and modulation (ACM) protocol. The suggested SS technique considers Higher Order Statistical (HOS) features of the signal and an efficient Machine Learning (ML) detector, the Support Vector Machine (SVM), in order to constantly monitor the modulation scheme of the PU. Once the Automatic modulation Classification (AMC) is ensured, the SU can attempt to access the frequency band of the PU and increase its transmitting power until it causes a change of the PU's modulation scheme due to interference. When the SU detects the change of the PU's modulation scheme, then it reduces its transmitting power to a lower level so as to regulate the induced interference. This adaptive Power Control (APC) algorithm converges to the aforementioned interference limit and guarantees preservation of the PU link QoS.
Atmospheric turbulence causes the receive signal intensity on free space optical (FSO) communication links to vary over time. Scintillation fades can stymie connectivity for milliseconds at a time. To approach the inf...
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ISBN:
(纸本)9781628410174
Atmospheric turbulence causes the receive signal intensity on free space optical (FSO) communication links to vary over time. Scintillation fades can stymie connectivity for milliseconds at a time. To approach the information-theoretic limits of communication in such time-varying channels, it necessary to either code across extremely long blocks of data - thereby inducing unacceptable delays - or to vary the code rate according to the instantaneous channel conditions. We describe the design, hardware implementation, and system performance of an FSO modem that employs low-density parity-check (LDPC) coding in an incremental redundancy (IR) hybrid automatic repeat request (HARQ) protocol. Independent tests performed by the U.S. Government demonstrate that our protocol effectively adapts the LDPC code rate to match the instantaneous channel conditions. For links with fixed throughput, this translates to the longest possible range in the presence of optical scintillation;for links with fixed range, this translates to the highest possible average throughput. By leveraging an LDPC that is amenable to low-complexity, high-throughput implementation in hardware, our modem is able to provide throughputs in excess of 850 Mbps on links with ranges greater than 15 kilometers.
The evolution of satellite communication towards packet-based communication and the adoption of modern physical layer techniques, such as adaptive coding and modulation, raise new issues, brought by this variability, ...
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ISBN:
(纸本)9781479935123
The evolution of satellite communication towards packet-based communication and the adoption of modern physical layer techniques, such as adaptive coding and modulation, raise new issues, brought by this variability, for scheduling algorithms. This paper addresses the problem of GSE packets scheduling over DVB-S2 with QoS support by adopting a utility-based scheduling strategy. Utility functions are considered as a mean to encompass parameters from several layers into a single scheduling process. By making use of a first-order approximation, a low complexity scheduling algorithm is derived from the utility functions optimization problem, adaptable to a wide range of functions. The algorithm determines the characteristics of the next BBFrame to be send, and which GSE packets it should contain. We focus particularly on delay as a joint metric to represent QoS requirements, and assess the performance of our algorithm and the relevance of our assumptions using comparative simulations.
Tills manuscript addresses the maximum-a-posterion-(MAP)-based automatic modulation classification (AMC) for wireless orthogonal frequency division multiplexing (OFDM) systems with adaptive coding and modulation (ACM)...
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ISBN:
(纸本)9781479903566
Tills manuscript addresses the maximum-a-posterion-(MAP)-based automatic modulation classification (AMC) for wireless orthogonal frequency division multiplexing (OFDM) systems with adaptive coding and modulation (ACM). The proposed classifier for quadrature amplitude modulation (QAM) schemes which utilizes the channel reciprocity in time-division duplex (TDD) systems requires the knowledge about the joint probabilities of the subcarrier-wise bit efficiencies at the transmitter and receiver side. In contrast to prior heuristic approaches, these probabilities are calculated analytically (with some approximations) if the transmitter and receiver apply the same hit loading algorithm on their erroneously estimated channel state information. Numerical results reveal that the precise knowledge of the joint probabilities improves the reliability of the automatic modulation classifier significantly, especially for high signal-to-noise power ratios (SNR).
This manuscript addresses the maximum-a-posteriori-(MAP)-based automatic modulation classification (AMC) for wireless orthogonal frequency division multiplexing (OFDM) systems with adaptive coding and modulation (ACM)...
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ISBN:
(纸本)9781479903573
This manuscript addresses the maximum-a-posteriori-(MAP)-based automatic modulation classification (AMC) for wireless orthogonal frequency division multiplexing (OFDM) systems with adaptive coding and modulation (ACM). The proposed classifier for quadrature amplitude modulation (QAM) schemes which utilizes the channel reciprocity in time-division duplex (TDD) systems requires the knowledge about the joint probabilities of the subcarrier-wise bit efficiencies at the transmitter and receiver side. In contrast to prior heuristic approaches, these probabilities are calculated analytically (with some approximations) if the transmitter and receiver apply the same bit loading algorithm on their erroneously estimated channel state information. Numerical results reveal that the precise knowledge of the joint probabilities improves the reliability of the automatic modulation classifier significantly, especially for high signal-to-noise power ratios (SNR).
Blind decoding, used on control channels of some multi-user wireless access systems, is a technique for achieving adaptivemodulation and coding. The idea is to adapt the modulation and coding scheme to the channel qu...
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ISBN:
(纸本)9781467309219;9781467309202
Blind decoding, used on control channels of some multi-user wireless access systems, is a technique for achieving adaptivemodulation and coding. The idea is to adapt the modulation and coding scheme to the channel quality but instead of signaling the parameters used explicitly, the receiver blindly tries a number of fixed parameter combinations until a successful decoding attempt is detected, with the help of a cyclic redundancy check. In this paper we suggest a new method for reducing the complexity and energy consumption associated with such blind decoding schemes. Our idea is to use a mini-CRC injected early in the data stream to determine if the current decoding attempt is using the correct modulation and coding parameters. We analyze and exemplify the complexity gain of this approach and also investigate the impact of the rearrangement of the CRC scheme in terms of the probability of undetected error. The presented results for the complexity gain are promising and the impact on the error detection capability turns out to be small if any.
In this paper a novel approach is presented for the design of a multibeam satellite system. It is based on the assumption that terminals have the capability to decode the links from the orthogonal transmissions that a...
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ISBN:
(纸本)9781467326766
In this paper a novel approach is presented for the design of a multibeam satellite system. It is based on the assumption that terminals have the capability to decode the links from the orthogonal transmissions that are present at any location of a conventional coloured multi-beam satellite system. Terminals would not only decode the transmission intended to the beam where it is located but also the transmissions intended to its adjacent beams. The key observation is that orthogonal frequencies and/or polarizations used for such transmissions can actually be considered as available offered throughput instead of being just wasted. This is of particular interest for multicast scenarios. This paper investigates this approach and an analytical model of a multilink reception is derived. Specifically, we obtain analytical expressions for the per user terminal (UT), per beam and system aggregated throughput. We apply the analysis assuming the adaptive physical layer reception of the Digital Video Broadcasting over Satellite 2nd generation (DVB-52). We show that for a realistic antenna and a four colour system, transmissions intended to the adjacent orthogonal beams can be decoded as spectral efficiencies spread over a wide range up to 16APSK. In particular, we show that assuming reception of both the intended and the strongest orthogonal signal and a uniform distribution of users a spectral efficiency reduction in 25% for the intended beam results in a spectral efficiency increase of 150% due to multi-link reception and so a net gain of 125% can be achieved. Furthermore, the service would target a larger number of users that a state-of-the-art design would do with the consequent revenue benefit.
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