Correcting Erasures and Errors in Random Network Coding

Ernst M. Gabidulin, Nina I. Pilipchuk, Martin Bossert

DOI: 10.14209/sbrt.2010.96

Keywords: matrix rank code vector rank code random rank error rank row erasure rank column erasure network coding fast decoding algorithm

Abstract

Rank-metric codes in matrix representation are used by Koetter, Kschischang, Silva in their theory of random network coding. They showed that the decoding procedure can be reduced to decoding of rank codes. In this paper, we analyzed situations under different conditions at the decoder and establish if there are errors only or some type of mixture of errors and erasures. For correcting we used Gabidulin decoding algorithms. In many situations this analysis helps to choose a suitable algorithm and to eliminate some of computing operations. An example is given.

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Rank codes – the State of Art

Ernst M. Gabidulin

DOI: 10.14209/sbrt.2010.1

Keywords: rank metric matrix rank code vector rank code random rank error rank row erasure rank column erasure fast decoding algorithm space-time code network coding public-key cryptography

Abstract

The State of Art for rank codes is presented. The theory and applications are considered.

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Control in Trellis Codes produced by Finite State Machines with Information Group Zp

Jorge Pedraza Arpasi

DOI: 10.14209/sbrt.2010.97

Keywords: Trellis codes dynamical systems controllability p-groups

Abstract

A trellis code is the image of a signal mapper from a time invariant group code produced by a Finite State Machine, FSM. Group codes can be described as dynamical systems and good group codes must be necessarily well behaved dynamical systems. For instance good group codes must be controllable and observable, among other properties of well-behaved systems. In this paper we work with trellis codes produced by Finite State Machines over non-abelian groups. The necessity of non-abelian groups on FSM is because there no exist any regular signal mapper between the outputs of a classical binary convolutional encoder and a M −PSK signal set. Also, it has been shown that the capacity of an AWGN channel using abelian group codes is upper bounded by the capacity of the same channel using PSK modulation eventually with different energies per symbol. We will show that when the trellis section group is non-abelian and the input group of the FSM is a cyclic group Zp = {0, 1, . . . , p − 1}, p prime, then the trellis code produced by the FSM is noncontrollable.

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Electromagnetic Interference Simulation of a Cell Phone in an Aircraft System Using Domain Decomposition Method

Juliano F. Mologni, Mateus Bonadiman, Leandro Percebon, Cesareo L. R. Siqueira, Marco A. R. Alves, Filipe Braumgratz, Edson Fonseca

DOI: 10.14209/sbrt.2010.99

Keywords: Domain Decomposition Method (DDM) Electromagnetic coupling Electromagnetic Interference (EMI) Electromagnetic Compatibility (EMC) Finite Element Method (FEM) Electromagnetic radiation effects

Abstract

Laboratorial experiments to investigate the behavior of numerous embedded avionics installations to onboard electromagnetic interference (EMI) are extremely complex and costly. Even if all electronic subsystems in an aircraft are validated under the electromagnetic compatibility (EMC) standards, the integration between them can create numerous points of potential hazards that affects the total electromagnetic behavior of the entire system, hazards that can be detected only when the first complete aircraft prototype is available, and whose resolution at this phase of the development process is very time consuming and expensive. Numerical techniques such as the finite element method (FEM) present a reliable solution to analyze EMI responses enabling additional analysis of any portable electronic device without impact the in-service aircraft schedules. FEM technique requires a considerable computational resource to solve large field problems, and in order to create a reliable model of an aircraft interior, a new procedure called domain decomposition method (DDM) was used taking advantage of parallel processing. In order to address the concern for cellular phone EMI to an aircraft monopole antenna and a wiring harness, a full numerical methodology was developed including actual diagnostic signals. The study presents complete results regarding EMI and communication channel analysis addressing the potential hazards of a cell phone in an aircraft’s electronic system.

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Capacity of CSMA under Nakagami Fading

Elvio J. Leonardo, Michel D. Yacoub

DOI: 10.14209/sbrt.2010.2

Keywords: Wireless communication CSMA Nakagami fading

Abstract

This paper investigates the throughput performance of carrier sense multiple access (CSMA) in a packet radio network and Nakagami fading environment. The approach considered includes the signal capture model with incoherent addition of interfering signals. The cases of uniform attenuation for all terminals (or perfect power control) as well as unequal average power levels are studied. Analytical and numerical results are presented.

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Ascending chain of semigroup rings and encoding

Tariq Shah, Atlas Khan, Antonio Aparecido de Andrade

DOI: 10.14209/sbrt.2010.3

Keywords: Semigroup ring BCH code alternant code Goppa code Srivastava code

Abstract

Let B be any finite commutative ring with identity. · · · ⊂ B[X; 1ak Z0] · · · ⊂ B[X; a12 Z0] ⊂ B[X; a1 Z0], where a ∈ {2, 3, 5, 7, · · ·}, k ≥ 1, is the descending chain of commutative semigroup rings. All these semigroup rings are containing the polynomial ring B[X; Z0]. In this paper initially we introduced the construction technique of cyclic codes through a semigroup ring B[X; 1 ak Z0] instead of a polynomial ring. After this we separately considered BCH, alternant, Goppa, Srivastava codes and by this new constructions we improve the several results of [1] by adopting the same lines as in [1].

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A New Model for VoIP Traffic Generation

Carlos Ignacio de Mattos, Eduardo Parente Ribeiro, Carlos Marcelo Pedroso

DOI: 10.14209/sbrt.2010.4

Keywords: Traffic Models Voice over IP Voice Codecs

Abstract

In this work a new model for VoIP traffic generation is proposed. The innovation of this model consists in modeling the user behavior instead of the aggregated traffic. We have analyzed the call holding time and the time interval between calls to characterize the user behavior. In order to provide an accurate packet generation, the data nature was modeled by identifying the time for packet transmission and the time interval between packets. Those variables of the proposed model were characterized with probability distributions. The parameters of the distributions were obtained with the analysis of real data collected from two major Brazilian telecommunications carriers. A VoIP traffic simulator was implemented and its results were compared with real data to validate the model. The similarity between synthetic and real data indicates that our model works properly and can be used for VoIP networks modeling and workload generation.

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Mobile Station Location using Genetic Algorithm Optimized Radio Frequency Fingerprinting

Rafael Saraiva Campos, Lisandro Lovisolo

DOI: 10.14209/sbrt.2010.5

Keywords: Mobile Station Location Radio Frequency Fingerprints Propagation Modeling Genetic Algorithms First Generation Population Correlation Space

Abstract

Radio Frequency Fingerprinting estimates the mobile station location by comparing a measured radio frequency fingerprint with a set of previously collected or generated reference fingerprints. This set is referred to as the search or correlation space. Genetic algorithms can be used to optimize both the location accuracy and the time required to produce a position fix, reducing the size of the search space. This paper proposes an innovation in such application of genetic algorithms, restricting the first generation population to the predicted best server area of the serving sector measured by the mobile station. In field tests in a GSM cellular network in a dense urban environment, this approach achieved reductions of 20% and 15% in the 50-th and 90-th percentile location errors, respectively, in comparison to the original formulation, where the initial population is randomly distributed throughout the whole service area. An average reduction of 91% in the time to produce a position fix was also observed

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A Traffic Policing Mechanism for Wimax Systems Based on Multifractal Modeling

Josemar A. Santos Jr, Flávio G. C. Rocha, Flávio H. T. Vieira

DOI: 10.14209/sbrt.2010.6

Keywords: Multifractal Traffic IEEE 802.16 Policing algorithms Wireless Traffic

Abstract

In this paper, we analyze the queueing performance in terms of loss rate of an OFDM (Orthogonal FrequencyDivision Multiplexing)/TDMA(Time Division Multiplexing Access) based Wimax system taking into account the multifractal behavior of the wireless traffic flows. To this end, first, we show evidences of multifractal characteristics on wireless traffic traces. These findings motivated us to propose a traffic policing and control scheme based on a multifractal envelope process in order to maintain the traffic flows wellbehaved, i.e., in accordance to the desired parameters. Simulations and comparisons to other methods are carried out to verify the efficiency of the proposed traffic policing.

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Vertical Handoff Algorithms for Heterogeneous 3G Networks

Leandro Bento Sena Marques, Shusaburo Motoyama

DOI: 10.14209/sbrt.2010.100

Keywords: --

Abstract

One of main challenges of fourth generation wireless networks (4G) will be the integration of various mobile technologies such as CDMA 1xEV-DO RA, UMTS/HSDPA and WiMAX. In this paper, the interoperability between the CDMA 1xEV-DO RA and the UMTS/HSDPA in the 4G context is investigated. New algorithms for vertical handoff traffic acceptance are proposed considering the link occupation, the buffer occupation, the radio signal strength (RSS) or the quantum size (DRR) of each 3G system, taken individually or in combination of them, as inputs for decision of vertical handoff process. Different algorithms are evaluated through QoS metrics such as the average packet delay and the loss percentage in function of vertical handoff traffic load. The results showed that depending on the chosen algorithm it is possible to assure the QoS of 1xEV-DO RA and UMTS/HSDPA systems and still to accept a good amount of vertical handoff traffic.

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