Revistas
Revista:
IEEE TRANSACTIONS ON QUANTUM ENGINEERING
ISSN:
2689-1808
Año:
2022
Vol.:
3
Págs.:
2100312
We have presented a method to detect degenerate errors in sparse quantum codes in a computationally efficient manner. We have also shown how this method is less complex than other existing strategies to compute the logical error rate of sparse CSS quantum codes. Making use of our scheme, we have shown how sparse quantum codes have a significant percentage of degenerate errors. This means that the discrepancy between the logical error rate and the physical error rate is exacerbated for sparse quantum codes. Our results show that, for specific families of QLDPC codes, performance may be up to 20% better than would be expected from previous results in the literature that are based on the physical error rate. In addition, these simulation outcomes serve to show how performance may be improved by constructing degenerate quantum codes, and they also speak toward the positive impact that modified decoding strategies can have on the performance of sparse quantum codes.
Revista:
PHYSICAL REVIEW, A
ISSN:
2469-9926
Año:
2022
Vol.:
106
N°:
6
Págs.:
062428
Surface codes are generally studied based on the assumption that each of the qubits that make up the surface code lattice suffers noise that is independent and identically distributed (i.i.d.). However, real benchmarks of the individual relaxation (T1) and dephasing (T2) times of the constituent qubits of state-of-the-art quantum processors have recently shown that the decoherence effects suffered by each particular qubit actually vary in intensity. In consequence, in this paper we introduce the independent nonidentically distributed (i.n.i.d.) noise model, a decoherence model that accounts for the nonuniform behavior of the decoherence parameters of qubits. Additionally, we use the i.n.i.d. model to study how it affects the performance of a specific family of quantum error correction codes known as planar codes. For this purpose we employ data from four state-of-the-art superconducting processors: ibmq_brooklyn, ibm_washington, Zuchongzhi, and Rigetti Aspen-M-1. Our results show that the i.i.d. noise assumption overestimates the performance of surface codes, which can suffer up to 95% performance decrements in terms of the code pseudothreshold when they are subjected to the i.n.i.d. noise model. Furthermore, we consider and describe two methods which enhance the performance of planar codes under i.n.i.d. noise. The first method involves a so-called reweighting process of the conventional minimum weight perfect matching (MWPM) decoder, while the second one exploits the relationship that exists between code performance and qubit arrangement in the surface code lattice. The optimum qubit configuration derived through the combination of the previous two methods can yield planar code pseudothreshold values that are up to 650% higher than for the traditional MWPM decoder under i.n.i.d. noise.
Revista:
PHYSICAL REVIEW, A
ISSN:
2469-9926
Año:
2022
Vol.:
105
N°:
1
Págs.:
012432
Recent experimental studies have shown that the relaxation time T-1 and the dephasing time T-2 of superconducting qubits fluctuate considerably over time. Time-varying quantum channel (TVQC) models have been proposed in order to consider the time-varying nature of the parameters that define qubit decoherence. This dynamic nature of quantum channels causes a degradation of the performance of quantum error correction codes (QECCs) that is portrayed as a flattening of their error rate curves. In this article we introduce the concepts of quantum outage probability and quantum hashing outage probability as asymptotically achievable error rates by a QECC with the quantum rate RQ operating over a TVQC. We derive closed-form expressions for the family of time-varying amplitude damping channels and study their behavior for different scenarios. We quantify the impact of time variation as a function of the relative variation of T-1 around its mean. We conclude that the performance of QECCs is limited in many cases by the inherent fluctuations of their decoherence parameters and corroborate that parameter stability is crucial to maintain the excellent performance observed over static quantum channels.
Revista:
IEEE ACCESS
ISSN:
2169-3536
Año:
2021
Vol.:
9
Págs.:
89093 - 89119
The well-documented capacity-approaching performance of sparse codes in the realm of classical communications has inspired the search for their quantum counterparts. Sparse quantum codes are generally built as the amalgamation of two robust classical codes and are decoded via classical decoding algorithms. However, the quantum paradigm presents phenomena that act in a deleterious manner on sparse quantum codes when they are decoded based on classical methodologies. One such phenomenon is known as degeneracy, and it is a major contributor to why sparse quantum codes do not entirely evoke the stupendous error correcting abilities of their classical counterparts. In this paper, we adopt a group theoretical approach to discuss the issue of degeneracy as it relates to sparse quantum codes. Furthermore, we compare the decoding process of sparse quantum codes with that of sparse classical codes, illustrating the challenges that appear in the quantum domain. Finally, we provide a detailed example to illustrate the effects of degeneracy on sparse quantum codes and the challenges of designing an optimum decoder for these schemes.
Revista:
PHYSICAL REVIEW, A
ISSN:
2469-9926
Año:
2021
Vol.:
103
N°:
2
Págs.:
022617
Quantum low-density-generator-matrix (QLDGM) codes are known to exhibit great error correction capabilities, surpassing existing quantum low-density-parity-check (QLDPC) codes and other sparse-graph schemes over the depolarizing channel. Most of the research on QLDPC codes and quantum error correction (QEC) is conducted for the symmetric instance of the generic Pauli channel, which incurs bit flips, phase flips, or a combination of both with the same probability. However, due to the behavior of the materials they are built from, some quantum devices must be modelled using a different channel model capable of accurately representing asymmetric scenarios in which the likelihood of a phase flip is higher than that of a bit flip. In this work, we study the design of QLDGM CSS codes for such Pauli channels. We show how codes tailored to the depolarizing channel are not well suited to these asymmetric environments and we derive methods to aptly design QLDGM CSS codes for this paradigm.
Revista:
IEEE ACCESS
ISSN:
2169-3536
Año:
2021
Vol.:
9
Págs.:
65449 - 65465
In this paper we consider the problem of transmitting spatially Correlated Information Sources (CIS) over the Additive White Gaussian Noise (AWGN) Multiple Access Channel (MAC) with transmitted energy constraint. It is well known that the system performance is optimized if the codewords are designed to take advantage of the correlation among sources in the multiple access channel. To that end, we make use of Rate Compatible Modulation (RCM) codes, whose sparse nature is advantageous to preserve the source correlation in the MAC. In order to exploit the source correlation, the proposed RCM-CIS system is comprised of a set of RCM codes that share the same random structure but with each code having its own weight values that are jointly designed. At the receiver, non-binary decoding is applied to avoid short length cycles that arise in the factor graph, which is obtained by jointly considering the source correlation and the RCM codes. Simulation results show that for high throughput transmission rate RCM-CIS has good performance in terms of the BER vs SNR, attaining values below the Shannon limit if source-channel separation is assumed. As shown by the numerical results, the proposed RCM system inherits the high error floors encountered in point-to-point RCM codes. In order to lower the error floor, we propose the use of a Low Density Generation Matrix (LDGM) code in parallel with the proposed RCM structure. The LDGM system transmits a small fraction of the total coded sequence, and it is capable of correcting the residual errors produced by the RCM-CIS system.
Autores:
Josu Etxezarreta (Autor de correspondencia); Patricio Fuentes; Crespo, Pedro M.; et al.
Revista:
NPJ QUANTUM INFORMATION
ISSN:
2056-6387
Año:
2021
Vol.:
7
N°:
1
Págs.:
115
The decoherence effects experienced by the qubits of a quantum processor are generally characterized using the amplitude damping time (T-1) and the dephasing time (T-2). Quantum channel models that exist at the time of writing assume that these parameters are fixed and invariant. However, recent experimental studies have shown that they exhibit a time-varying (TV) behaviour. These time-dependant fluctuations of T-1 and T-2, which become even more pronounced in the case of superconducting qubits, imply that conventional static quantum channel models do not capture the noise dynamics experienced by realistic qubits with sufficient precision. In this article, we study how the fluctuations of T-1 and T-2 can be included in quantum channel models. We propose the idea of time-varying quantum channel (TVQC) models, and we show how they provide a more realistic portrayal of decoherence effects than static models in some instances. We also discuss the divergence that exists between TVQCs and their static counterparts by means of a metric known as the diamond norm. In many circumstances this divergence can be significant, which indicates that the time-dependent nature of decoherence must be considered, in order to construct models that capture the real nature of quantum devices
Revista:
PHYSICAL REVIEW A
ISSN:
1050-2947
Año:
2020
Vol.:
102
N°:
1
Quantum low-density generator matrix (QLDGM) codes based on Calderbank-Steane-Shor (CSS) con-structions have shown unprecedented error correction capabilities, displaying much improved performance in comparison to other sparse-graph codes. However, the nature of CSS designs and the manner in which they must be decoded limit the performance that is attainable with codes that are based on this construction. This motivates the search for quantum code design strategies capable of avoiding the drawbacks associated with CSS codes. In this article, we introduce non-CSS quantum code constructions based on classical LDGM codes. The proposed codes are derived from CSS QLDGM designs by performing specific row operations on their quantum parity check matrices to modify the associated decoding graphs. The application of this method results in performance improvements in comparison to CSS QLDGM codes, while also allowing for greater flexibility in the design process. The proposed non-CSS QLDGM scheme outperforms the best quantum low-density parity check codes that have appeared in the literature.
Revista:
IEEE ACCESS
ISSN:
2169-3536
Año:
2020
Vol.:
8
Págs.:
172623 - 172643
Quantum information is prone to suffer from errors caused by the so-called decoherence, which describes the loss in coherence of quantum states associated to their interactions with the surrounding environment. This decoherence phenomenon is present in every quantum information task, be it transmission, processing or even storage of quantum information. Consequently, the protection of quantum information via quantum error correction codes (QECC) is of paramount importance to construct fully operational quantum computers. Understanding environmental decoherence processes and the way they are modeled is fundamental in order to construct effective error correction methods capable of protecting quantum information. Moreover, quantum channel models that are efficiently implementable and manageable on classical computers are required in order to design and simulate such error correction schemes. In this article, we present a survey of decoherence models, reviewing the manner in which these models can be approximated into quantum Pauli channel models, which can be efficiently implemented on classical computers. We also explain how certain families of quantum error correction codes can be entirely simulated in the classical domain, without the explicit need of a quantum computer. A quantum error correction code for the approximated channel is also a correctable code for the original channel, and its performance can be obtained by Monte Carlo simulations on a classical computer.
Autores:
Peralta, G. (Autor de correspondencia); Garrido, P. ; Bilbao, J.; et al.
Revista:
SIMULATION MODELLING PRACTICE AND THEORY
ISSN:
1569-190X
Industry 4.0 applications foster new business opportunities, but they also pose new and challenging requirements, such as low latency communications and highly reliable systems. They would likely exploit novel wireless technologies (5G), but it would also become crucial using architectures that appropriately support them. In this sense, the combination of fog and cloud computing represents a potential solution, since it can dynamically allocate the workload depending on the specific needs of each application. In this paper, our main goal is to provide a highly reliable and dynamic architecture, which minimizes the time that an end node or user, spends in downloading the required data. In order to achieve this, we have developed an optimal distribution algorithm that decides the amount of information that should be stored at, or retrieved from, each node, to minimize the overall data download time. Our scheme is based on various parameters and it exploits Network Coding (NC) as a tool for data distribution, as a key enabler of the proposed solution. We compare the performance of the proposed scheme with other alternative solutions, and the results show that there is a clear gain in terms of the download time.
Revista:
IEEE ACCESS
ISSN:
2169-3536
Año:
2020
Vol.:
8
Págs.:
224246 - 224259
We propose a new Non-Orthogonal Multiple Access (NOMA) coding scheme based on the use of a Rate Compatible Modulation (RCM) encoder for each user. By properly designing the encoders and taking advantage of the additive nature of the Multiple Access Channel (MAC), the joint decoder from the inputs of all the users can be represented by a bipartite graph corresponding to a standard point-to-point RCM structure with certain constraints. Decoding is performed over this bipartite graph utilizing the sum-product algorithm. The proposed scheme allows the simultaneous transmission of a large number of uncorrelated users at high rates, while the decoding complexity is the same as that of standard point-to-point RCM schemes. When Rayleigh fast fading channels are considered, the BER vs SNR performance improves as the number of simultaneous users increases, as a result of the averaging effect.
Revista:
WIRELESS NETWORKS
ISSN:
1022-0038
Año:
2019
Vol.:
25
N°:
2
Págs.:
665 - 673
This paper proposes a novel scheme for the slow block fading Gaussian multiple access relay channel inspired by the compute-and-forward (CoF) relaying strategy. The CoF relaying strategy exploits interference to obtain significantly higher rates between users in a network by decoding linear functions of the transmitted messages. Unlike other approaches in the literature, our approach is valid for any number of transmitters and, most importantly, it only requires channel state information at the receiver side, while it still attains similar or higher rates than the other approaches found in the literature.
Revista:
EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING
ISSN:
1687-1472
Año:
2019
N°:
1
Págs.:
1 - 14
This paper proposes an extrinsic information transfer (EXIT) chart analysis and an asymptotic bit error rate (BER) prediction method to speed up the design of high rate RCM-LDGM hybrid codes over AWGN and fast Rayleigh channels. These codes are based on a parallel concatenation of a rate compatible modulation (RCM) code with a low-density generator matrix (LDGM) code. The decoder uses the iterative sum-product algorithm to exchange information between the variable nodes (VNs) and the two types of constituent check nodes: RCM-CN and LDGM-CN. The novelty of the proposed EXIT chart procedure lies on the fact that it mixes together the analog RCM check nodes with the digital LDGM check nodes, something not possible in previous multi-edge EXIT charts proposed in the literature.
Revista:
ENTROPY
ISSN:
1099-4300
Año:
2019
Vol.:
21
N°:
4
Págs.:
378
In this paper, we look at the problem of implementing high-throughput Joint Source- Channel (JSC) coding schemes for the transmission of binary sources with memory over AWGN channels. The sources are modeled either by a Markov chain (MC) or a hidden Markov model (HMM). We propose a coding scheme based on the Burrows-Wheeler Transform (BWT) and the parallel concatenation of Rate-Compatible Modulation and Low-Density Generator Matrix (RCM-LDGM) codes. The proposed scheme uses the BWT to convert the original source with memory into a set of independent non-uniform Discrete Memoryless (DMS) binary sources, which are then separately encoded, with optimal rates, using RCM-LDGM codes.
Revista:
ENTROPY
ISSN:
1099-4300
Año:
2019
Vol.:
21
N°:
12
Págs.:
1133
Quantum turbo codes (QTC) have shown excellent error correction capabilities in the setting of quantum communication, achieving a performance less than 1 dB away from their corresponding hashing bounds. Decoding for QTCs typically assumes that perfect knowledge about the channel is available at the decoder. However, in realistic systems, such information must be estimated, and thus, there exists a mismatch between the true channel information and the estimated one. In this article, we first heuristically study the sensitivity of QTCs to such mismatch. Then, existing estimation protocols for the depolarizing channel are presented and applied in an off-line manner to provide bounds on how the use of off-line estimation techniques affects the error correction capabilities of QTCs. Finally, we present an on-line estimation method for the depolarizing probability, which, different from off-line estimation techniques, neither requires extra qubits, nor increases the latency. The application of the proposed method results in a performance similar to that obtained with QTCs using perfect channel information, while requiring less stringent conditions on the variability of the channel than off-line estimation techniques.
Autores:
Goiuri Peralta (Autor de correspondencia); Cid-Fuentes, R.; Bilbao, J. ; et al.
Revista:
ELECTRONICS
ISSN:
2079-9292
Año:
2019
Vol.:
8
N°:
8
Págs.:
827
The introduction of the Internet of Things (IoT) is creating manifold new services and opportunities. This new technological trend enables the connection of a massive number of devices among them and with the Internet. The integration of IoT with cloud platforms also provides large storage and computing capabilities, enabling Big Data analytics and bidirectional communication between devices and users. Novel research directions are showing that Network Coding (NC) can increase the robustness and throughput of wireless networks, as well as that Homomorphic Encryption (HE) can be used to perform computations in the cloud while maintaining data privacy. In this paper, we overview the benefits of NC and HE along the entire vertical of cloud-based IoT architectures. By merging both technologies, the architecture may offer manifold advantages: First, it provides end-to-end data privacy, from end-devices to end-users. Second, sensitive data can be stored in public cloud platforms without concern about their privacy. In addition, clouds can perform advanced operations in a confidential manner, without the need to access actual data. Finally, latency can be reduced and the reliability of the system is increased. We show state-of-the-art works that demonstrate the role of both technologies in this type of architectures on a review basis. Furthermore, we describe the main characteristics of NC and HE and also discuss their benefits and limitations, as well as the emerging open challenge
Revista:
ENTROPY
ISSN:
1099-4300
Año:
2019
Vol.:
21
N°:
7
Págs.:
633
Quantum turbo codes (QTC) have shown excellent error Corrección capabilities in the setting of quantum communication, achieving a performance less than 1 dB away from their corresponding hashing bounds. Existing QTCs have been constructed using uniform random interleavers. However, interleaver design plays an important role in the optimization of classical turbo codes. Consequently, inspired by the widely used classical-to-quantum isomorphism, this paper studies the integration of classical interleaving design methods into the paradigm of quantum turbo coding. Simulations results demonstrate that error floors in QTCs can be lowered significantly, while decreasing memory consumption, by proper interleaving design without increasing the overall decoding complexity of the system.
Autores:
Goiuri Peralta; Pablo Garrido; Josu Bilbao; et al.
Revista:
SENSORS
ISSN:
1424-8220
The adoption of both Cyber¿Physical Systems (CPSs) and the Internet-of-Things (IoT) has enabled the evolution towards the so-called Industry 4.0. These technologies, together with cloud computing and artificial intelligence, foster new business opportunities. Besides, several industrial applications need immediate decision making and fog computing is emerging as a promising solution to address such requirement. In order to achieve a cost-efficient system, we propose taking advantage from spot instances, a new service offered by cloud providers, which provide resources at lower prices. The main downside of these instances is that they do not ensure service continuity and they might suffer from interruptions. An architecture that combines fog and multi-cloud deployments along with Network Coding (NC) techniques, guarantees the needed fault-tolerance for the cloud environment, and also reduces the required amount of redundant data to provide reliable services. In this paper we analyze how NC can actually help to reduce the storage cost and improve the resource efficiency for industrial applications, based on a multi-cloud infrastructure. The cost analysis has been carried out using both real AWS EC2 spot instance prices and, to complement them, prices obtained from a model based on a finite Markov chain, derived from real measurements. We have analyzed the overall system cost, depending on different parameters, showing that configurations that seek to minimize the storage yield a higher cost reduction, due to the strong impact of storage cost
Autores:
Santamaria, I. (Autor de correspondencia); Crespo, Pedro M.; Lameiro, C.; et al.
Revista:
ENTROPY
ISSN:
1099-4300
Non-circular or improper Gaussian signaling has proven beneficial in several interference-limited wireless networks. However, all implementable coding schemes are based on finite discrete constellations rather than Gaussian signals. In this paper, we propose a new family of improper constellations generated by widely linear processing of a square M-QAM (quadrature amplitude modulation) signal. This family of discrete constellations is parameterized by , the circularity coefficient and a phase phi. For uncoded communication systems, this phase should be optimized as phi * to maximize the minimum Euclidean distance between points of the improper constellation, therefore minimizing the bit error rate (BER). For the more relevant case of coded communications, where the coded symbols are constrained to be in this family of improper constellations using phi*, it is shown theoretically and further corroborated by simulations that, except for a shaping loss of 1.53 dB encountered at a high signal-to-noise ratio (snr), there is no rate loss with respect to the improper Gaussian capacity. In this sense, the proposed family of constellations can be viewed as the improper counterpart of the standard proper M-QAM constellations widely used in coded communication systems.
Revista:
IEEE COMMUNICATIONS LETTERS
ISSN:
1089-7798
Año:
2018
Vol.:
22
Págs.:
1754 - 1757
Revista:
ENTROPY
ISSN:
1099-4300
Revista:
WIRELESS COMMUNICATIONS AND MOBILE COMPUTING
ISSN:
1530-8669
This paper focuses on the modeling, simulation, and experimental verification of wideband single-input single-output (SISO) mobile fading channels for indoor propagation environments. The indoor reference channel model is derived from a geometrical rectangle scattering model, which consists of an infinite number of scatterers. It is assumed that the scatterers are exponentially distributed over the two-dimensional (2D) horizontal plane of a rectangular room. Analytical expressions are derived for the probability density function (PDF) of the angle of arrival (AOA), the PDF of the propagation path length, the power delay profile (PDP), and the frequency correlation function (FCF). An efficient sum-of-cisoids (SOC) channel simulator is derived from the nonrealizable reference model by employing the SOC principle. It is shown that the SOC channel simulator approximates closely the reference model with respect to the FCF. The SOC channel simulator enables the performance evaluation of wideband indoor wireless communication systems with reduced realization expenditure. Moreover, the rationality and usefulness of the derived indoor channel model is confirmed by various measurements at 2.4, 5, and 60¿GHz.
Revista:
IEEE TRANSACTIONS ON INFORMATION THEORY
ISSN:
0018-9448
Año:
2017
Vol.:
63
Págs.:
6000 - 6003
Revista:
SENSORS
ISSN:
1424-8220
Revista:
IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS
ISSN:
0733-8716
Año:
2016
Vol.:
34
N°:
7
Págs.:
1965 - 1977
The wide availability of power distribution cables provides an interesting no-new-wires communication channel. However, its electrical characteristics make it a harsh environment for the data transmission purpose and prevent the deployment of services with high reliability requirements. This paper proposes and implements an OSI-Layer2 network coding-based cooperative scheme with the aim of improving communication reliability in indoor narrowband powerline channels. The proposed scheme uses random linear network coding with a sliding window and relaying. We use network coding to replace the retransmissions triggered by legacy subsequent repeat request (ARQ) schemes. We evaluate the performance of our approach in terms of throughput and delay. Regarding the throughput achieved in harsh environments, we show that our scheme often more than doubles the throughput of existing legacy ARQ schemes. At the same time, and even under the large variation of traffic characteristics, it is shown that the delay is likely to be upper bounded by a few seconds, a bound that cannot be guaranteed in other existing transmission techniques.
Revista:
IEEE TRANSACTIONS ON SIGNAL PROCESSING
ISSN:
1053-587X
Año:
2015
Vol.:
63
N°:
12
Págs.:
3046 - 3061
Joint source-channel coding schemes based on analog mappings for point-to-point channels have recently gained attention for their simplicity and low delay. In this paper, these schemes are extended either to scenarios with or without side information at the decoders to transmit multiple descriptions of a Gaussian source over independent parallel channels. They are based on a lattice scaling approach together with bandwidth reduction analog mappings adapted for this multiple description scenario. The rationale behind lattice scaling is to improve performance through band-width expansion. Another important contribution of this paper is the proof of the separation theorem for the communication scenario of multiple description with side information at the decoders. This proof allows us to compare the performance of the proposed schemes with the theoretical limits when considering AWGN channels. Finally, when the channels are parallel slow-fading Rayleigh, the proposed schemes are optimal in terms of distortion exponent.
Revista:
EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING
ISSN:
1687-1499
This paper proposes a Decode-and-Forward (DF) relaying scheme for the multi-hop transmission in wireless networks, where the information generated by an independent source has to be sent to a far destination based on multiple-relay cooperation. The proposed DF scheme blends together convolutional channel coding with linear combination of blocks of data over a finite field using very short block lengths (K=13). We provide an extrinsic information transfer (EXIT) chart analysis to understand the good performance behavior of the proposed scheme when compared with other referenced schemes using much larger block lengths. This fact is corroborated by a set of Monte Carlo simulations. Moreover, the proposed DF scheme is suitable for large multi-hop networks since a negligible performance degradation is obtained when adding more hops.
Revista:
EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING
ISSN:
1687-1499
Año:
2013
Vol.:
2013
N°:
125
Págs.:
1 - 15
In this paper, we present a fundamental study on the stationarity and ergodicity of eight classes of sum-of-cisoids (SOC) processes for the modeling and simulation of frequency-nonselective mobile Rayleigh fading channels. The purpose of this study is to determine which classes of SOC models enable the design of channel simulators that accurately reproduce the channel's statistical properties without demanding information on the time origin or the time-consuming computation of an ensemble average. We investigate the wide-sense stationarity, first-order stationarity of the envelope, mean ergodicity, and autocorrelation ergodicity of the underlying random processes characterizing the different classes of stochastic SOC simulators. The obtained results demonstrate that only the class of SOC models comprising cisoids with constant gains, constant frequencies, and random phases is defined by a set of stationary and ergodic random processes. The analysis presented here can easily be extended with respect to the modeling and simulation of frequency-selective single-input single-output (SISO) and multiple-input multiple-output channels. For the case of frequency-selective SISO channels, we investigate the stationarity and ergodicity in both time and frequency of 16 different classes of SOC simulation models. The findings presented in this paper can be used in the laboratory as guidelines to design efficient simulation platforms for the performance evaluation of modern mobile communication systems.
Revista:
IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING
ISSN:
1932-4553
Año:
2013
Vol.:
7
Págs.:
163 - 174
Revista:
IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS
ISSN:
0733-8716
Año:
2013
Vol.:
31
N°:
8
Págs.:
1368 - 1378
This paper proposes a novel joint non-binary network-channel code for the Time-Division Decode-and-Forward Multiple Access Relay Channel (TD-DF-MARC), where the relay linearly combines - over a non-binary finite field - the coded sequences from the source nodes. A method based on an EXIT chart analysis is derived for selecting the best coefficients of the linear combination. Moreover, it is shown that for different setups of the system, different coefficients should be chosen in order to improve the performance. This conclusion contrasts with previous works where a random selection was considered. Monte Carlo simulations show that the proposed scheme outperforms, in terms of its gap to the outage probabilities, the previously published joint network-channel coding approaches. Besides, this gain is achieved by using very short-length codewords, which makes the scheme particularly attractive for low-latency applications.
Autores:
Bilbao, J.; Calvo, A.; Armendariz, I.; et al.
Revista:
JOURNAL OF TELECOMMUNICATIONS AND INFORMATION TECHNOLOGY
ISSN:
1509-4553
Año:
2013
Vol.:
2013
Págs.:
23 - 40
One of the most challenging research fields in which research community has taken a very active role is focused on trying to bring the features of wireless networks into line with the traditional wired solutions. Given the noisy and lossy nature of the wireless medium, it is more difficult to provide a comparable Quality of Service (QoS) and Reliability over wireless networks. This lack of reliability avoids the use of wireless solution in scenarios under harsh environment and mission-critical applications. In this paper we propose an inter-node collaborative schema with the aim of improving the achievable QoS level for multicast streaming, through the use of Network Coding and the algebra it is based on. We also present an implementation of the described algorithm on the OPNET discrete event simulation tool. Experimental results highlighting the performance achieved by the proposed algorithm and its improved efficiency as compared to other solutions are described.
Autores:
Khodaian, M.; Perez, J.; Khalaj, B.; et al.
Revista:
EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING
ISSN:
1687-1499
In this article, we present a cross-layer adaptive algorithm that dynamically maximizes the average utility function. A per stage utility function is defined for each link of a carrier sense multiple access-based wireless network as a weighted concave function of energy consumption, smoothed rate, and smoothed queue size. Hence, by selecting weights we can control the trade-off among them. Using dynamic programming, the utility function is maximized by dynamically adapting channel access, modulation, and coding according to the queue size and quality of the time-varying channel. We show that the optimal transmission policy has a threshold structure versus the channel state where the optimal decision is to transmit when the wireless channel state is better than a threshold. We also provide a queue management scheme where arrival rate is controlled based on the link state. Numerical results show characteristics of the proposed adaptation scheme and highlight the trade-off among energy consumption, smoothed data rate, and link delay.
Revista:
IEEE COMMUNICATIONS LETTERS
ISSN:
1089-7798
Año:
2012
Vol.:
16
N°:
9
Págs.:
1508 - 1511
This letter introduces a channel coding design framework for short-length codewords which can achieve lower error floor than previous approaches. The proposed code is based on combining convolutional coding with a q-ary linear combination and unequal energy allocation. Simulation results suggest that for very low Bit Error Rates (BER) the proposed system will exhibit lower error floors than previous approaches, with a small performance penalty at mid-range BERs. On the other hand, when selecting an error floor higher than the previous approaches, the loss in performance at mid-range BERs is negligible.
Revista:
IEEE TRANSACTIONS ON SIGNAL PROCESSING
ISSN:
1053-587X
Año:
2012
Vol.:
60
N°:
11
Págs.:
5880 - 5892
The complexity and delay introduced by efficient digital coding strategies may be a barrier in some real-time communications. In this sense, these last years, joint source-channel coding schemes based on analog mappings have gained prominence precisely for their simplicity and their implicit low delay. In this work, analog mappings originally designed for point-to-point communications are adapted to the case of parallel channels by following the multiple description strategy traditionally used in source coding. In principle, the coding scheme is designed to transmit over parallel AWGN on-off channels, which are characterized by the possibility of having failures. We also show that our scheme performs satisfactorily over slow Rayleigh fading parallel channels.
Revista:
IEEE TRANSACTIONS ON INFORMATION THEORY
ISSN:
0018-9448
Año:
2011
Vol.:
57
N°:
8
Págs.:
5444 - 5454
Revista:
EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING
ISSN:
1687-1499
This paper focuses on the data fusion scenario where N nodes sense and transmit the data generated by a source S to a common destination, which estimates the original information from S more accurately than in the case of a single sensor. This work joins the upsurge of research interest in this topic by addressing the setup where the sensed information is transmitted over a Gaussian Multiple-Access Channel (MAC). We use Low Density Generator Matrix (LDGM) codes in order to keep the correlation between the transmitted codewords, which leads to an improved received Signal-to-Noise Ratio (SNR) thanks to the constructive signal addition at the receiver front-end. At reception, we propose a joint decoder and estimator that exchanges soft information between the N LDGM decoders and a data fusion stage. An error-correcting Bose, Ray-Chaudhuri, Hocquenghem (BCH) code is further applied suppress the error floor derived from the ambiguity of the MAC channel when dealing with correlated sources. Simulation results are presented for several values of N and diverse LDGM and BCH codes, based on which we conclude that the proposed scheme outperforms significantly (by up to 6.3 dB) the suboptimum limit assuming separation between Slepian-Wolf source coding and capacity-achieving channel coding.
Revista:
SIGNAL PROCESSING
ISSN:
0165-1684
Año:
2011
Vol.:
91
N°:
8
Págs.:
1709 - 1718
In the absence of observation noise, it is known that it is possible to develop exact sampling schemes for a large class of parametric non-bandlimited signals, namely, certain signals of finite rate of innovation (FRI signals), either periodic or aperiodic, such as streams of Diracs, nonuniform splines or piecewise polynomials. A common feature of such signals is that they have a finite number of degrees of freedom per unit of time and they can be reconstructed from a finite number of uniform samples of the filtered signal. Unfortunately, the accuracy of such reconstruction substantially degrades when the samples are distorted by noise. For the case of periodic FRI signals, good algorithms based on the state space method have been proposed which are robust against noise. However, in the case of aperiodic signals, these algorithms may still fail to accurately reconstruct the signals due to ill-conditioning problems that often arise in the matrices involved. This paper proposes a new reconstruction method for aperiodic FRI signals that is also based on the state space method but has a considerably better numerical conditioning than previous reconstruction algorithms. This advantage is achieved by using a frequency domain formulation. (C) 2011 Elsevier B.V. All rights reserved.
Revista:
SIGNAL PROCESSING
ISSN:
0165-1684
Año:
2010
Vol.:
90
N°:
1
Págs.:
134 - 144
In early 2000, it was shown that it is possible to develop exact sampling schemes for a large class of parametric non-bandlimited noiseless signals, namely certain signals of finite rate of innovation. In particular, signals x(t) that are linear combinations of a finite number of Diracs per unit of time can be acquired by linear filtering followed by uniform sampling. However, when noise is present, many of the early proposed schemes can become ill-conditioned. Recently, a novel stochastic algorithm based on Gibbs sampling was proposed by Tan & Goyal [IEEE Trans. Sign. Proc., 56 (10) 5135] to recover the filtered signal z(t) of x(t) by observing noisy samples of z(t). In the present paper, by blending together concepts of evolutionary algorithms with those of Gibbs sampling, a novel stochastic algorithm which substantially improves the results in the cited reference is proposed. (C) 2009 Elsevier B.V. All rights reserved.
Revista:
IEEE TRANSACTIONS ON COMMUNICATIONS
ISSN:
0090-6778
Año:
2010
Vol.:
58
N°:
7
Págs.:
1984 - 1992
The Burrows-Wheeler Transform (BWT) [1] is a block sorting algorithm which has been proven to be useful in compressing text data [2]. More recently, schemes based on the BWT have been proposed for lossless data compression using LDPC [3]-[5] and Fountain [6] codes, as well as for joint source-channel coding of sources with memory [7], [8]. In this paper we propose a source-controlled Turbo coding scheme for the transmission of sources with memory over AWGN channels also based on the Burrows-Wheeler Transform. Our approach combines the BWT with a Turbo code and employs different energy allocation techniques for the encoded symbols before their transmission. Simulation results show that the performance of the designed scheme is close (within 1.5 dB) to the theoretical Shannon limit.
Revista:
IEEE COMMUNICATIONS LETTERS
ISSN:
1089-7798
Año:
2010
Vol.:
14
N°:
9
Págs.:
794 - 796
In this paper, we design a new energy allocation strategy for non-uniform binary memoryless sources encoded by Low-Density Parity-Check (LDPC) codes and sent over Additive White Gaussian Noise (AWGN) channels. The new approach estimates the a priori probabilities of the encoded symbols, and uses this information to allocate more energy to the transmitted symbols that occur less likely. It can be applied to systematic and non-systematic LDPC codes, improving in both cases the performance of previous LDPC based schemes using binary signaling. The decoder introduces the source non-uniformity and estimates the source symbols by applying the SPA (Sum Product Algorithm) over the factor graph describing the code.
Revista:
JOURNAL OF COMMUNICATIONS AND NETWORKS
ISSN:
1229-2370
Año:
2010
Vol.:
12
N°:
1
Págs.:
86-94
In this paper, we present a decentralized algorithm to find minimum cost quality of service (QoS) flow subgraphs in network coded multicast schemes. The main objective is to find minimum cost subgraphs that also satisfy user-specified QoS constraints, specifically with respect to rate and delay demands. We consider networks with multiple multicast sessions. Although earlier network coding algorithms in this area have demonstrated performance improvements in terms of QoS parameters, the proposed QoS network coding approach provides a framework that guarantees QoS constraints are actually met over the network.
Revista:
IEEE COMMUNICATIONS LETTERS
ISSN:
1089-7798
Año:
2010
Vol.:
14
N°:
3
Págs.:
235 - 235
Revista:
IEEE COMMUNICATIONS LETTERS
ISSN:
1089-7798
Año:
2010
Vol.:
14
N°:
4
Págs.:
336 - 338
This letter proposes a novel one-layer coding/shaping scheme with single-level codes and sigma-mapping for the bandwidth-limited regime. Specifically, we consider non-uniform memoryless sources sent over AWGN channels. At the transmitter, binary data are encoded by a Turbo code composed of two identical RSC (Recursive Systematic Convolutional) encoders. The encoded bits are randomly interleaved and modulated before entering the sigma-mapper. The modulation employed in this system follows the unequal energy allocation scheme first introduced in [1]. The receiver consists of an iterative demapping/decoding algorithm, which incorporates the a priori probabilities of the source symbols. To the authors' knowledge, work in this area has only been done for the power-limited regime. In particular, the authors in [2] proposed a scheme based on a Turbo code with RSC encoders and unequal energy allocation. Therefore, it is reasonable to compare the performance - with respect to the Shannon limit - of our proposed bandwidth-limited regime scheme with this former power-limited regime scheme. Simulation results show that our performance is as good or slightly better than that of the system in [2].
Revista:
MICROWAVE AND OPTICAL TECHNOLOGY LETTERS
ISSN:
0895-2477
Año:
2010
Vol.:
52
N°:
4
Págs.:
889-895
Antenna arrays that incorporate MIMO technology for indoor-outdoor network interconnection on the same terminal, i.e., for DCS 1800. PCS 1900, WCDMA, 3G. 802.11a/b/g. Bluetooth (R). ZigBee (R), WiMAX (TM), and UWB standards, are proposed. Staircase profile printed circuit antenaas, monopoles (PCM). and slots (PCS) with VSWR < 2 bandwidth mainly from 1.12 to 10.1 GHz are previously designed, simulated. constructed, and measured as antenna elements for those arrays. For comparison. prototypes for two-element PCM and PCS MIMO arrays have been constructed and measured, The choice should be made according to the directivity required by the final application and portable device size. For the worst signal interference case, the operational bandwidth ranges from 1.5 to 9.9 GHz and from 1.7 to 11.4 GHz for the PCM and the PCS MIMO arrays, respectively. VSWR is basically below two, average capacity loss 0.32 bps/Hz with respect to the ideal uncorrelated (2,2) case and envelope correlation lower than 20 dB. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 889-895, 2010: Published online in Wiley InterScience (www.interscience.wiley.com). DOI:10.1002/mop.25047
Nacionales y Regionales
Título:
MINECO Lineas Estratégicas: Few-qubit quantum hardware, algorithms and codes, on photonic and solid-state systems - (QUANTUM)
Código de expediente:
PLEC2021-008251
Investigador principal:
Pedro Crespo Bofill
Financiador:
AGENCIA ESTATAL DE INVESTIGACION
Convocatoria:
2021 AEI Proyectos de I+D+i en líneas estratégicas
Fecha de inicio:
01/10/2021
Fecha fin:
30/09/2024
Importe concedido:
77.314,00€
Otros fondos:
-
Título:
DECALOQC: Degenerate quantum error correction and theoretical limits of time-varying quantum channels
Código de expediente:
2021-CIEN-000077-02-01
Investigador principal:
Pedro Crespo Bofill
Financiador:
DIPUTACIÓN FORAL DE GIPUZKOA
Convocatoria:
Programa Red guipuzcoana de Ciencia, Tecnología e Innovación_DFG 2021
Fecha de inicio:
01/09/2021
Fecha fin:
30/09/2022
Importe concedido:
101.393,00€
Otros fondos:
-
Título:
Avances en codificación y procesado de la señal para la sociedad digital
Código de expediente:
PID2019-104958RB-C44
Investigador principal:
Jesús Gutiérrez Gutiérrez, Pedro Crespo Bofill
Financiador:
MINISTERIO DE CIENCIA E INNOVACIÓN
Convocatoria:
2019 AEI PROYECTOS I+D+i (incluye Generación del conocimiento y Retos investigación)
Fecha de inicio:
01/06/2020
Fecha fin:
31/01/2024
Importe concedido:
124.872,00€
Otros fondos:
-
Título:
Desarrollo de nuevas tecnologias y herramientas que aceleren la transicion a una produccion inteligente
Código de expediente:
KK-2020/00060
Investigador principal:
Xabier Insausti Sarasola
Financiador:
GOBIERNO VASCO
Convocatoria:
2020 GV Elkartek -Proyectos de apoyo a la investigacion colaborativa en areas estrategicas.Tipo 1.
Fecha de inicio:
01/04/2020
Fecha fin:
31/12/2021
Importe concedido:
116.322,00€
Otros fondos:
-
Título:
Control distribuido avanzado para la seguridad y la eficiencia energetica del transporte aereo
Código de expediente:
KK-2020/00044
Investigador principal:
Xabier Insausti Sarasola
Financiador:
GOBIERNO VASCO
Convocatoria:
2020 GV Elkartek -Proyectos de apoyo a la investigacion colaborativa en areas estrategicas.Tipo 1.
Fecha de inicio:
01/03/2020
Fecha fin:
31/12/2021
Importe concedido:
73.675,00€
Otros fondos:
-
Título:
Codificacion y procesado de señales para redes emergentes de comunicacion y de sensores inhalambricas
Código de expediente:
TEC2016-75067-C4-3-R
Investigador principal:
Pedro Crespo Bofill
Financiador:
MINISTERIO DE CIENCIA E INNOVACIÓN
Convocatoria:
2016 MINECO RETOS INVESTIGACION. PROYECTOS I+D+i
Fecha de inicio:
01/01/2017
Fecha fin:
31/12/2020
Importe concedido:
168.795,00€
Otros fondos:
-
