Optimal Policy for Initial Selection Radio Access Technology in Next Generation Wireless Networks

Rodolfo W. L. Coutinho, Vitor L. Coelho, Joao C. W. A. Costa, Glaucio H. S. Carvalho

DOI: 10.14209/sbrt.2010.24

Keywords:

Abstract

In this paper, we propose an optimal Joint Call Admission Control (JCAC) in next generation wireless networks, where different radio access technologies (RAT) coexist in a colocated way, and we study the impact of the different RAT’s radius coverage area in the system performance. By assuming that each incoming service request may be admitted in its native RAT or in an alternative RAT, we design an optimal JCAC that has to decide in which type of RAT the incoming call has to be admitted. This decision is evaluated under the consideration that the co-located RATs have different coverage areas. Numerical results show that variation in the proportionality of the radius of RAT coverage area impact on system performance.

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On the Impact of Non-Linear High Power Amplifiers on Coded OFDM

Ian Alves Ulian, André Noll Barreto

DOI: 10.14209/sbrt.2010.25

Keywords: OFDM PAPR non-linear power amplifier total degradation channel coding

Abstract

The high peak-to-average power ratio (PAPR) is one of the main disadvantages of OFDM systems, which reduces the transmission efficiency with non-linear power amplifiers and causes unwanted distortions and out-of-band radiation. There are many schemes proposed in the literature to mitigate this problem. However, the majority of these contributions only analyse the PAPR reduction and do not consider the system BER performance in the presence of an amplifier. When BER analysis for non-linear amplifiers is found in the literature, it is usually done not considering channel coding, even though OFDM in most real systems is coded. In this contribution we investigate the performance of an OFDM system in terms of total degradation, also considering channel coding, and show that with strong coding the effect of a nonlinear amplifier is far less negative than in an uncoded system. We also see that some schemes that effectively reduce PAPR, may in fact bring about very little performance gain when coding is taken into account.

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Quantum Permanent Compromise Attack to Blum-Micali Pseudorandom Generator

Elloá B. Guedes, Francisco M. de Assis, Bernardo Lula Jr.

DOI: 10.14209/sbrt.2010.26

Keywords: Blum-Micali Generator Quantum Attack Grover Algorithm

Abstract

This paper presents a quantum permanent compromise attack to the Blum-Micali pseudorandom generator whose security is based on the assumption of intractability of the discrete logarithm problem. The proposed attack makes use of the Grover’s quantum search extension for multiple solutions and of quantum parallelism to recover the generator’s internal state with high probability. This attack compromises the unpredictability of the Blum-Micali cryptographic secure pseudorandom generator, since it recovers all previous and future output, as well as the generator’s seed. Compared to the classical equivalent attack, the quantum algorithm proposed has a quadratic speedup, and represents a menace against the security of a pseudorandom generator used in many real-world cryptosystems.

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Comparative Analysis of PMD and PDL on DOP in Optical Communication Systems for NRZ, RZ and CSRZ Signals

Fátima Regina Caldeira Barroso, Raymundo Nogueira Sá Netto, João Batista Rosa Silva

DOI: 10.14209/sbrt.2010.27

Keywords: Coherence matrix degree of polarization PDL PMD Stokes parameters

Abstract

This paper presents a numerical analysis of the dispersive effects of light polarization in optical fibers. This study analyzed the behavior of the degree of polarization using the Jones matrix method for modeling the transmission channel as a concatenation of 15 sections of polarization scramblers of PMD and PDL, using the RZ, RZ and CSRZ rectangular digital signals. The numerical simulation considers the effects of first order PMD and PDL

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Performance of WHT-STC-OFDM in Mobile Frequency Selective Channel

Luciano Leonel Mendes, Renato Baldini Filho

DOI: 10.14209/sbrt.2010.28

Keywords: Time-variant frequency-selective channel OFDM Space-Time Coding Walsh-Hadamard Transform

Abstract

High data rate systems usually employ Orthogonal Frequency Division Multiplexing and Space-Time Coding to improve the performance on a mobile time-variant frequency-selective channel. Nonlinearities introduced by the power amplifier can be minimized by performing a WashHadamard Transform on the data symbol prior the Inverse Fast Fourier Transform (IFFT) at the transmitter. This procedure reduces the peak-to-average power ratio of the OFDM symbol. An extra advantage of the WHT combined with OFDM is the performance improvement on a frequency-selective channel. The aim of this paper is to present an analytical expression to estimate the performance of the WHT-STCOFDM taking into account the receiver/transmitter mobility, the channel frequency response and the noise added by the channel. The theoretical results are corroborated by computer simulations.

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Interference Analysis of Coexistence Scenarios in TV White Spaces

Robson D. Vieira, Edgar B. Souza, Andre M. Cavalcante, Riku Pirhonen, Padam Kafle, Andrei Malkov, Zexian Li

DOI: 10.14209/sbrt.2010.126

Keywords: TV band white spaces interference analysis

Abstract

Broadband wireless systems in TV White Spaces have gained considerable attention since FCC started the process in 2004 and later 2008 published the first rules for TV band devices. Several companies, mainly in the US, are looking at the new opportunities and are putting efforts to develop standards in industry forums and IEEE. Since white spaces spectrum is accessed in opportunistic way, it can be seen as a step towards the deployment of cognitive networks. In order to evaluate the benefits and challenges for technologies which may operate in the TV white spaces spectrum, the analysis of radio frequency issues has an important role. Out of band emissions and intermodulation products from other channels are examples of RF impairments that should be considered in the interference analysis. When some of the requirements are not fulfilled, cell coverage and spectral efficiency can be reduced. In this paper, an interference analysis, taking in account the RF impairments, was done for several coexistence scenarios in the White Spaces (WS) context. The analysis was done not only considering the FCC rules but also investigating other RF parameters.

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Node Deployment by Stochastic Point Processes in Wireless Sensor Networks

Heitor S. Ramos, Marcelo G. Almiron, Alejandro C. Frery, Eduardo F. Nakamura, Antonio A. F. Loureiro

DOI: 10.14209/sbrt.2010.29

Keywords:

Abstract

Node deployment plays an important role in the design of wireless sensor networks (WSNs). Many important properties such as coverage, connectivity, data fidelity and lifetime are directed influenced by the way nodes are placed in the sensor field. In this work we show that the use of a stochastic point process, namely the C model, is able to increase the network lifetime by addressing the “energy hole” problem. Among the C model properties, this process can be easily simulated and, for any number of nodes in arbitrary areas, it is able to describe situations that range from deterministic (regular) placement of nodes to clusters of sensors in a small region. The model is herein described and is assessed in terms of the coverage, connectivity, data fidelity and lifetime by using computer simulation. In particular, we compare the C process with the mostly used deployment strategy, namely the uniform randomly placement (URP), being the latter a particular case of the former.

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An Application Server Approach for Number Portability in IMS networks

Rafael Gava de Oliveira, Paulo Sigrist, Wilson A. Higashino, Cassiano O. Becker, Carlos E. Pagani, Joaquim Silva

DOI: 10.14209/sbrt.2010.107

Keywords: Number Portability Telecommunication NGN IMS Application Server

Abstract

Number portability (NP) is an important requirement present in most telephony networks. Typically, NP is regulated by local legislation and is inherently against the very nature of routing in circuit-switched networks, which can complicate its deployment. The technological move towards IP-based networks demands treatment of legacy numbers portability, so as to enable interoperability among technologies and allowing progressive substitution of old networks. This paper aims at presenting an application serverbased approach for NP aimed at NGN networks, especially IMS. A test implementation is presented, along with a discussion of currently used approaches, as well as of the one here proposed. Test results validate the approach and show good overall performance.

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A Code for Correcting Quantum Erasures

G. O. dos Santos, F. M. de Assis, A. F. de Lima

DOI: 10.14209/sbrt.2010.106

Keywords: quantum error-correction code quantum erasure GHZ states

Abstract

Quantum states are very delicate, so quantum error-correction procedures are believed to be essential for the successful implementation of quantum communications or computations. To erroneous qubits where the position is known, Grassl et al. [Phys. Rev. A 56, 33 (1997)] proposed an error model which they called quantum erasure channel. In this paper we present a quantum code capable of protecting nqubit of information against the occurrence of t erasures. This code is based on GHZ states.

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A UWB Power Delay Profile Data Acquisition for Indoor Environments Using a Spectrum Analyser

Andréa Duarte Carvalho, Luiz Cezar Trintinalia

DOI: 10.14209/sbrt.2010.30

Keywords: measurements indoor radio propagation spectrum analyzer

Abstract

This paper presents a measurement system for indoor characterization of UWB channels. The presented method uses a scalar network analyzer (SNA) or a spectrum analyzer (SA) with tracking generator, connected to two antennas: a receiving and a transmitting one. This setup, which obtains only the magnitude data of the frequency response, makes the method less expensive when compared with other setups presented in the literature. From the magnitude data of the frequency response, a processing algorithm obtains the phase data of the frequency response making it possible to calculate the channel power delay profile. The tests for validation of the method are detailed herein

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