OpenRaiser/Intern-Atlas huggingface dataset:
Frequency Domain Hybrid-ARQ Chase Combining for Broadband MIMO CDMA Systems
Venue: arXiv cs.IT 2009
Year: 2009

In this paper, we consider high-speed wireless packet access using code division multiple access (CDMA) and multiple-input multiple-output (MIMO). Current wireless standards, such as high speed packet access (HSPA), have adopted multi-code transmission and hybrid-automatic repeat request (ARQ) as major technologies for delivering high data rates. The key technique in hybrid-ARQ, is that erroneous data packets are kept in the receiver to detect/decode retransmitted ones. This strategy is refereed to as packet combining. In CDMA MIMO-based wireless packet access, multi-code transmission suffers from severe performance degradation due to the loss of code orthogonality caused by both interchip interference (ICI) and co-antenna interference (CAI). This limitation results in large transmission delays when an ARQ mechanism is used in the link layer. In this paper, we investigate efficient minimum mean square error (MMSE) frequency domain equalization (FDE)-based iterative (turbo) packet combining for cyclic prefix (CP)-CDMA MIMO with Chase-type ARQ. We introduce two turbo packet combining schemes: i) In the first scheme, namely "chip-level turbo packet combining", MMSE FDE and packet combining are jointly performed at the chip-level. ii) In the second scheme, namely "symbol-level turbo packet combining", chip-level MMSE FDE and despreading are separately carried out for each transmission, then packet combining is performed at the level of the soft demapper. The computational complexity and memory requirements of both techniques are quite insensitive to the ARQ delay, i.e., maximum number of ARQ rounds. The throughput is evaluated for some representative antenna configurations and load factors to show the gains offered by the proposed techniques.
On the Algorithmic Complexity of the Mastermind Game with Black-Peg Results
Venue: arXiv cs.DS 2009
Year: 2009

In this paper, we study the algorithmic complexity of the Mastermind game, where results are single-color black pegs. This differs from the usual dual-color version of the game, but better corresponds to applications in genetics. We show that it is NP-complete to determine if a sequence of single-color Mastermind results have a satisfying vector. We also show how to devise efficient algorithms for discovering a hidden vector through single-color queries. Indeed, our algorithm improves a previous method of Chvatal by almost a factor of 2.
Gaussian Belief with dynamic data and in dynamic network
Venue: arXiv cs.AI 2009
Year: 2009

In this paper we analyse Belief Propagation over a Gaussian model in a dynamic environment. Recently, this has been proposed as a method to average local measurement values by a distributed protocol ("Consensus Propagation", Moallemi & Van Roy, 2006), where the average is available for read-out at every single node. In the case that the underlying network is constant but the values to be averaged fluctuate ("dynamic data"), convergence and accuracy are determined by the spectral properties of an associated Ruelle-Perron-Frobenius operator. For Gaussian models on Erdos-Renyi graphs, numerical computation points to a spectral gap remaining in the large-size limit, implying exceptionally good scalability. In a model where the underlying network also fluctuates ("dynamic network"), averaging is more effective than in the dynamic data case. Altogether, this implies very good performance of these methods in very large systems, and opens a new field of statistical physics of large (and dynamic) information systems.
Millimeter-Wave System for High Data Rate Indoor Communications
Venue: arXiv cs.NI 2009
Year: 2009

This paper presents the realization of a wireless Gigabit Ethernet communication system operating in the 60 GHz band. The system architecture uses a single carrier modulation. A differential encoded binary phase shift keying modulation and a differential demodulation scheme are adopted for the intermediate frequency blocks. The baseband blocks use Reed- Solomon RS (255, 239) coding and decoding for channel forward error correction (FEC). First results of bit error rate (BER) measurements at 875 Mbps, without channel coding, are presented for different antennas.
REC language is a live on IBM1130 simulator, EL lenguaje REC esta vivo en el simulador de la IBM 1130
Venue: arXiv cs.PL 2009
Year: 2009

REC (Regular Expression Compiler) is a concise programming language development in mayor Mexican Universities at end of 60s which allows students to write programs without knowledge of the complicated syntax of languages like FORTRAN and ALGOL. The language is recursive and contains only four elements for control. This paper describes use of the interpreter of REC written in FORTRAN on IBM1130 Simulator from -Computer History Simulation- Project.
Self-stabilizing Determinsitic Gathering
Venue: arXiv cs.MA 2009
Year: 2009

In this paper, we investigate the possibility to deterministically solve the gathering problem (GP) with weak robots (anonymous, autonomous, disoriented, deaf and dumb, and oblivious). We introduce strong multiplicity detection as the ability for the robots to detect the exact number of robots located at a given position. We show that with strong multiplicity detection, there exists a deterministic self-stabilizing algorithm solving GP for n robots if, and only if, n is odd.
What is the Value of Joint Processing of Pilots and Data in Block-Fading Channels?
Venue: arXiv cs.IT 2009
Year: 2009

The spectral efficiency achievable with joint processing of pilot and data symbol observations is compared with that achievable through the conventional (separate) approach of first estimating the channel on the basis of the pilot symbols alone, and subsequently detecting the data symbols. Studied on the basis of a mutual information lower bound, joint processing is found to provide a non-negligible advantage relative to separate processing, particularly for fast fading. It is shown that, regardless of the fading rate, only a very small number of pilot symbols (at most one per transmit antenna and per channel coherence interval) should be transmitted if joint processing is allowed.
Matrix Graph Grammars as a Model of Computation
Venue: arXiv cs.DM 2009
Year: 2009

Matrix Graph Grammars (MGG) is a novel approach to the study of graph dynamics ([15]). In the present contribution we look at MGG as a formal grammar and as a model of computation, which is a necessary step in the more ambitious program of tackling complexity theory through MGG. We also study its relation with other well-known models such as Turing machines (TM) and Boolean circuits (BC) as well as non-determinism. As a side effect, all techniques available for MGG can be applied to TMs and BCs.
Design of Learning Based MIMO Cognitive Radio Systems
Venue: arXiv cs.IT 2009
Year: 2009

This paper addresses the design issues of the multi-antenna-based cognitive radio (CR) system that is able to operate concurrently with the licensed primary radio (PR) system. We propose a practical CR transmission strategy consisting of three major stages: environment learning, channel training, and data transmission. In the environment learning stage, the CR transceivers both listen to the PR transmission and apply blind algorithms to estimate the spaces that are orthogonal to the channels from the PR. Assuming time-division duplex (TDD) based transmission for the PR, cognitive beamforming is then designed and applied at CR transceivers to restrict the interference to/from the PR during the subsequent channel training and data transmission stages. In the channel training stage, the CR transmitter sends training signals to the CR receiver, which applies the linear-minimum-mean-square-error (LMMSE) based estimator to estimate the effective channel. Considering imperfect estimations in both learning and training stages, we derive a lower bound on the ergodic capacity achievable for the CR in the data transmission stage. From this capacity lower bound, we observe a general learning/training/throughput tradeoff associated with the proposed scheme, pertinent to transmit power allocation between training and transmission stages, as well as time allocation among learning, training, and transmission stages. We characterize the aforementioned tradeoff by optimizing the associated power and time allocation to maximize the CR ergodic capacity.
A Domain Decomposition Strategy for Alignment of Multiple Biological Sequences on Multiprocessor Platforms
Venue: arXiv cs.DC 2009
Year: 2009

Multiple Sequences Alignment (MSA) of biological sequences is a fundamental problem in computational biology due to its critical significance in wide ranging applications including haplotype reconstruction, sequence homology, phylogenetic analysis, and prediction of evolutionary origins. The MSA problem is considered NP-hard and known heuristics for the problem do not scale well with increasing number of sequences. On the other hand, with the advent of new breed of fast sequencing techniques it is now possible to generate thousands of sequences very quickly. For rapid sequence analysis, it is therefore desirable to develop fast MSA algorithms that scale well with the increase in the dataset size. In this paper, we present a novel domain decomposition based technique to solve the MSA problem on multiprocessing platforms. The domain decomposition based technique, in addition to yielding better quality, gives enormous advantage in terms of execution time and memory requirements. The proposed strategy allows to decrease the time complexity of any known heuristic of O(N)^x complexity by a factor of O(1/p)^x, where N is the number of sequences, x depends on the underlying heuristic approach, and p is the number of processing nodes. In particular, we propose a highly scalable algorithm, Sample-Align-D, for aligning biological sequences using Muscle system as the underlying heuristic. The proposed algorithm has been implemented on a cluster of workstations using MPI library. Experimental results for different problem sizes are analyzed in terms of quality of alignment, execution time and speed-up.
Curse of Dimensionality in the Application of Pivot-based Indexes to the Similarity Search Problem
Venue: arXiv cs.DS 2009
Year: 2009

In this work we study the validity of the so-called curse of dimensionality for indexing of databases for similarity search. We perform an asymptotic analysis, with a test model based on a sequence of metric spaces $(Ω_d)$ from which we pick datasets $X_d$ in an i.i.d. fashion. We call the subscript $d$ the dimension of the space $Ω_d$ (e.g. for $\mathbb{R}^d$ the dimension is just the usual one) and we allow the size of the dataset $n=n_d$ to be such that $d$ is superlogarithmic but subpolynomial in $n$. We study the asymptotic performance of pivot-based indexing schemes where the number of pivots is $o(n/d)$. We pick the relatively simple cost model of similarity search where we count each distance calculation as a single computation and disregard the rest. We demonstrate that if the spaces $Ω_d$ exhibit the (fairly common) concentration of measure phenomenon the performance of similarity search using such indexes is asymptotically linear in $n$. That is for large enough $d$ the difference between using such an index and performing a search without an index at all is negligeable. Thus we confirm the curse of dimensionality in this setting.
The Rainbow Skip Graph: A Fault-Tolerant Constant-Degree P2P Relay Structure
Venue: arXiv cs.DS 2009
Year: 2009

We present a distributed data structure, which we call the rainbow skip graph. To our knowledge, this is the first peer-to-peer data structure that simultaneously achieves high fault tolerance, constant-sized nodes, and fast update and query times for ordered data. It is a non-trivial adaptation of the SkipNet/skip-graph structures of Harvey et al. and Aspnes and Shah, so as to provide fault-tolerance as these structures do, but to do so using constant-sized nodes, as in the family tree structure of Zatloukal and Harvey. It supports successor queries on a set of n items using O(log n) messages with high probability, an improvement over the expected O(log n) messages of the family tree.
Enhancing the robustness of scale-free networks
Venue: arXiv cs.NI 2009
Year: 2009

Error tolerance and attack vulnerability are two common and important properties of complex networks, which are usually used to evaluate the robustness of a network. Recently, much work has been devoted to determining the network design with optimal robustness. However, little attention has been paid to the problem of how to improve the robustness of existing networks. In this paper, we present a new parameter alpha, called enforcing parameter, to guide the process of enhancing the robustness of scale-free networks by gradually adding new links. Intuitively, alpha < 0 means the nodes with lower degrees are selected preferentially while the nodes with higher degrees will be more probably selected when alpha > 0. It is shown both theoretically and experimentally that when alpha < 0 the attack survivability of the network can be enforced apparently. Then we propose new strategies to enhance the network robustness. Through extensive experiments and comparisons, we conclude that establishing new links between nodes with low degrees can drastically enforce the attack survivability of scale-free networks while having little impact on the error tolerance.
Modeling System Safety Requirements Using Input/Output Constraint Meta-Automata
Venue: arXiv cs.SE 2009
Year: 2009

Most recent software related accidents have been system accidents. To validate the absence of system hazards concerning dysfunctional interactions, industrials call for approaches of modeling system safety requirements and interaction constraints among components and with environments (e.g., between humans and machines). This paper proposes a framework based on input/output constraint meta-automata, which restricts system behavior at the meta level. This approach can formally model safe interactions between a system and its environment or among its components. This framework differs from the framework of the traditional model checking. It explicitly separates the tasks of product engineers and safety engineers, and provides a top-down technique for modeling a system with safety constraints, and for automatically composing a safe system that conforms to safety requirements. The contributions of this work include formalizing system safety requirements and a way of automatically ensuring system safety.
Multilevel Coding over Two-Hop Single-User Networks
Venue: arXiv cs.IT 2009
Year: 2009

In this paper, a two-hop network in which information is transmitted from a source via a relay to a destination is considered. It is assumed that the channels are static fading with additive white Gaussian noise. All nodes are equipped with a single antenna and the Channel State Information (CSI) of each hop is not available at the corresponding transmitter. The relay is assumed to be simple, i.e., not capable of data buffering over multiple coding blocks, water-filling over time, or rescheduling. A commonly used design criterion in such configurations is the maximization of the average received rate at the destination. We show that using a continuum of multilevel codes at both the source and the relay, in conjunction with decode and forward strategy at the relay, performs optimum in this setup. In addition, we present a scheme to optimally allocate the available source and relay powers to different levels of their corresponding codes. The performance of this scheme is evaluated assuming Rayleigh fading and compared with the previously known strategies.
Time Delay Estimation from Low Rate Samples: A Union of Subspaces Approach
Venue: arXiv cs.IT 2009
Year: 2009

Time delay estimation arises in many applications in which a multipath medium has to be identified from pulses transmitted through the channel. Various approaches have been proposed in the literature to identify time delays introduced by multipath environments. However, these methods either operate on the analog received signal, or require high sampling rates in order to achieve reasonable time resolution. In this paper, our goal is to develop a unified approach to time delay estimation from low rate samples of the output of a multipath channel. Our methods result in perfect recovery of the multipath delays from samples of the channel output at the lowest possible rate, even in the presence of overlapping transmitted pulses. This rate depends only on the number of multipath components and the transmission rate, but not on the bandwidth of the probing signal. In addition, our development allows for a variety of different sampling methods. By properly manipulating the low-rate samples, we show that the time delays can be recovered using the well-known ESPRIT algorithm. Combining results from sampling theory with those obtained in the context of direction of arrival estimation methods, we develop necessary and sufficient conditions on the transmitted pulse and the sampling functions in order to ensure perfect recovery of the channel parameters at the minimal possible rate. Our results can be viewed in a broader context, as a sampling theorem for analog signals defined over an infinite union of subspaces.
Two snap-stabilizing point-to-point communication protocols in message-switched networks
Venue: arXiv cs.DS 2009
Year: 2009

A snap-stabilizing protocol, starting from any configuration, always behaves according to its specification. In this paper, we present a snap-stabilizing protocol to solve the message forwarding problem in a message-switched network. In this problem, we must manage resources of the system to deliver messages to any processor of the network. In this purpose, we use information given by a routing algorithm. By the context of stabilization (in particular, the system starts in an arbitrary configuration), this information can be corrupted. So, the existence of a snap-stabilizing protocol for the message forwarding problem implies that we can ask the system to begin forwarding messages even if routing information are initially corrupted. In this paper, we propose two snap-stabilizing algorithms (in the state model) for the following specification of the problem: - Any message can be generated in a finite time. - Any emitted message is delivered to its destination once and only once in a finite time. This implies that our protocol can deliver any emitted message regardless of the state of routing tables in the initial configuration. These two algorithms are based on the previous work of [MS78]. Each algorithm needs a particular method to be transform into a snap-stabilizing one but both of them do not introduce a significant overcost in memory or in time with respect to algorithms of [MS78].
PetFMM--A dynamically load-balancing parallel fast multipole library
Venue: arXiv cs.DC 2009
Year: 2009

Fast algorithms for the computation of $N$-body problems can be broadly classified into mesh-based interpolation methods, and hierarchical or multiresolution methods. To this last class belongs the well-known fast multipole method (FMM), which offers O(N) complexity. This paper presents an extensible parallel library for $N$-body interactions utilizing the FMM algorithm, built on the framework of PETSc. A prominent feature of this library is that it is designed to be extensible, with a view to unifying efforts involving many algorithms based on the same principles as the FMM and enabling easy development of scientific application codes. The paper also details an exhaustive model for the computation of tree-based $N$-body algorithms in parallel, including both work estimates and communications estimates. With this model, we are able to implement a method to provide automatic, a priori load balancing of the parallel execution, achieving optimal distribution of the computational work among processors and minimal inter-processor communications. Using a client application that performs the calculation of velocity induced by $N$ vortex particles, ample verification and testing of the library was performed. Strong scaling results are presented with close to a million particles in up to 64 processors, including both speedup and parallel efficiency. The library is currently able to achieve over 85% parallel efficiency for 64 processors. The software library is open source under the PETSc license; this guarantees the maximum impact to the scientific community and encourages peer-based collaboration for the extensions and applications.
The Gaussian Many-to-One Interference Channel with Confidential Messages
Venue: arXiv cs.IT 2009
Year: 2009

We investigate the $K$-user many-to-one interference channel with confidential messages in which the $K$th user experiences interference from all other $K-1$ users, and is at the same time treated as an eavesdropper to all the messages of these users. We derive achievable rates and an upper bound on the sum rate for this channel and show that the gap between the achievable sum rate and its upper bound is $\log_2(K-1)$ bits per channel use under very strong interference, when the interfering users have equal power constraints and interfering link channel gains. The main contributions of this work are: (i) nested lattice codes are shown to provide secrecy when interference is present, (ii) a secrecy sum rate upper bound is found for strong interference regime and (iii) it is proved that under very strong interference and a symmetric setting, the gap between the achievable sum rate and the upper bound is constant with respect to transmission powers.
Sparse Network Coding with Overlapping Classes
Venue: arXiv cs.IT 2009
Year: 2009

This paper presents a novel approach to network coding for distribution of large files. Instead of the usual approach of splitting packets into disjoint classes (also known as generations) we propose the use of overlapping classes. The overlapping allows the decoder to alternate between Gaussian elimination and back substitution, simultaneously boosting the performance and reducing the decoding complexity. Our approach can be seen as a combination of fountain coding and network coding. Simulation results are presented that demonstrate the promise of our approach.
Colorization of Natural Images via L1 Optimization
Venue: arXiv cs.CV 2009
Year: 2009

Natural images in the colour space YUV have been observed to have a non-Gaussian, heavy tailed distribution (called 'sparse') when the filter G(U)(r) = U(r) - sum_{s \in N(r)} w{(Y)_{rs}} U(s), is applied to the chromacity channel U (and equivalently to V), where w is a weighting function constructed from the intensity component Y [1]. In this paper we develop Bayesian analysis of the colorization problem using the filter response as a regularization term to arrive at a non-convex optimization problem. This problem is convexified using L1 optimization which often gives the same results for sparse signals [2]. It is observed that L1 optimization, in many cases, over-performs the famous colorization algorithm by Levin et al [3].
Cryptography for Multi-Located Parties
Venue: arXiv cs.CR 2009
Year: 2009

This note describes some cryptographic issues related to multi-located parties. In general, multi-located parties make it difficult for the eavesdropper to mount the man-in-the-middle attack. Conversely, they make it easier to address problems such as joint encryption and error correction coding. It is easier to implement the three-stage quantum cryptography protocol.