Saulo Queiroz

Maximal Spectral Efficiency of OFDM with Index Modulation under Polynomial Space Complexity

IEEE Wireless Communications Letters

In this letter, we demonstrate a mapper that enables all waveforms of OFDM with Index Modulation ... more In this letter, we demonstrate a mapper that enables all waveforms of OFDM with Index Modulation (OFDM-IM) while preserving polynomial time and space computational complexities. Enabling all OFDM-IM waveforms maximizes the spectral efficiency (SE) gain over the classic OFDM but, as far as we know, the computational overhead of the resulting mapper remains conjectured as prohibitive across the OFDM-IM literature. We show that the largest number of binomial coefficient calculations performed by the original OFDM-IM mapper is polynomial on the number of subcarriers, even under the setup that maximizes the SE gain over OFDM. Also, such coefficients match the entries of the so-called Pascal's triangle (PT). Thus, by assisting the OFDM-IM mapper with a PT table, we show that the maximum SE gain over OFDM can be achieved under polynomial (rather than exponential) time and space complexities.

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Optimal Mapper for OFDM With Index Modulation: A Spectro-Computational Analysis

IEEE Access

In this work, we present an optimal mapper for OFDM with index modulation (OFDM-IM). By optimal w... more In this work, we present an optimal mapper for OFDM with index modulation (OFDM-IM). By optimal we mean the mapper achieves the lowest possible asymptotic computational complexity (CC) when the spectral efficiency (SE) gain over OFDM maximizes. We propose the spectro-computational (SC) analysis to capture the trade-off between CC and SE and to demonstrate that an N-subcarrier OFDM-IM mapper must run in exact (N) time complexity. We show that an OFDM-IM mapper running faster than such complexity cannot reach the maximal SE whereas one running slower nullifies the mapping throughput for arbitrarily large N. We demonstrate our theoretical findings by implementing an open-source library that supports all DSP steps to map/demap an N-subcarrier complex frequency-domain OFDM-IM symbol. Our implementation supports different index selector algorithms and is the first to enable the SE maximization while preserving the same time and space asymptotic complexities of the classic OFDM mapper.

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Influence of Routing Protocol on VoIP Quality Performance in Wireless Mesh Backbone

by Saulo Queiroz and Edjair Mota

… , 2008. NGMAST'08. …, Jan 1, 2008

In this paper we focus on the following question: how routing protocols, working under different ... more In this paper we focus on the following question: how routing protocols, working under different channel conditions, can influence the human perceived quality of VoIP calls in a wireless mesh backbone? In order to respond this question, we propose a study case where we analyze two routing approaches in a 802.11 Wireless Mesh Backbone, namely, reactive AODV and proactive OLSR. We calculated the voice speech quality by making use of a reviewed version of ITU-T E-Model proposed in previous work. Results obtained from highly credible stochastic simulation environment, also described in this paper, showed that AODV performs better in very hostile mediums while OLSR presents better results when more friendly mediums take place.

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Voice over Wireless Mesh Networks: A Case Study in the Brazilian Amazon Region during the Rainy Season

by Saulo Queiroz, Edjair Mota, and João Luis Gomes Moreira

… , 2009. WAINA'09. …, Jan 1, 2009

In this paper we present the results of an experimental analysis of the behavior and performance ... more

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Impact evaluation of radio propagation models on performance parameters of application layer in Wireless Mesh Backbone simulation

by Saulo Queiroz and Edjair Mota

IEEE Symposium on Computers and Communications, 2008., Jul 2008

In this paper we propose a VoIP study case to evaluate the impact of different radio propagation ... more In this paper we propose a VoIP study case to evaluate the impact of different radio propagation models on performance parameters of application layer in simulation studies of Wireless Mesh Backbones. For each presented model, we carried out experiments taking into account the credibility aspects suggested by simulation theory of stochastic processes. Results showed that, for the same scenario, using different propagation models, voice speech quality can switch from acceptable to unacceptable.

Análise de desempenho de tráfego VoIP utilizando o Protocolo IP Security

by Saulo Queiroz and Edjair Mota

Anais do I Workshop de …, Jan 1, 2004

Influence of Propagation Modeling on VoIP Quality Performance in Wireless Mesh Network Simulation

by Saulo Queiroz and Edjair Mota

… and Simulation of …, Jan 1, 2008

In this paper we evaluate the influence ofradio propagation modeling on VoIP quality in wireless ... more

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Towards an efficient header compression scheme to improve VoIP over wireless mesh networks

by Saulo Queiroz and Edjair Mota

… , 2009. ISCC 2009. …, Jan 1, 2009

Header compression techniques can improve the speech quality of VoIP applications. However, its d... more Header compression techniques can improve the speech quality of VoIP applications. However, its deployment over wireless mesh environments may not offer much improvement, since the wireless and multi-hop characteristics of such a network impose a high packet loss rate. In this work, we propose a new approach for header compression, using packet aggregation to cooperate with the header compression scheme. Simulation results show that the new cooperative approach can decrease significantly the packet loss, impacting positively on the speech quality.

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Towards an Efficient Header Compression Scheme to Improve VoIP over Wireless Mesh Networks

by Edjair Mota and Saulo Queiroz

Header compression techniques can improve the speech quality of VoIP applications. However, its d... more Header compression techniques can improve the speech quality of VoIP applications. However, its deployment over wireless mesh environments may not offer much improvement, since the wireless and multi-hop characteristics of such a network impose a high packet loss rate. In this work, we propose a new approach for header compression, using packet aggregation to cooperate with the header compression scheme. Simulation results show that the new cooperative approach can decrease significantly the packet loss, impacting positively on the speech quality.

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Header compression for VoIP over multi-hop wireless mesh networks

by Edjair Mota and Saulo Queiroz

… , 2008. ISCC 2008. …, Jan 1, 2008

With the increasing deployment of wireless mesh net-works, the usage of a number of services in s... more

Concordo, Discordo ou DependeAssim é o Fórum da Controvérsia Acadêmica

… do Workshop de …, 2003

Resumo: É indiscutível que as tecnologias de informação e comunicação têm contribuído significati... more

Um Ambiente Telemático para Mediar a Controvérsia Acadêmica

This article presents Versus, a virtual learning environment for mediating activities in the coop... more This article presents Versus, a virtual learning environment for mediating activities in the cooperative learning method called Academic Controversy. Although it is a well known method, there is no report of using it within distance learning or computer mediated situations. Versus also uses Concept Maps as media for knowledge representation. Resumo. Esse artigo apresenta o Versus, um ambiente virtual de aprendizagem para mediar as atividades do método de aprendizagem cooperativa denominado Controvérsia Acadêmica. Apesar de ser bastante conhecido, não há na literatura levantada, relato de uso desse método em situações não presenciais ou com o auxílio do computador. No Versus, os Mapas Conceituais foram utilizados como mídia para representação do conhecimento.

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Otimizaç oes em uma pilha SIP de código aberto visando o uso de VoIP em plataformas embarcadas

Um Ambiente Telemático para Mediar a Controvérsia Acadêmica

Anais do Simpósio …, 2003

This article presents Versus, a virtual learning environment for mediating activities in the coop... more This article presents Versus, a virtual learning environment for mediating activities in the cooperative learning method called Academic Controversy. Although it is a well known method, there is no report of using it within distance learning or computer mediated situations. Versus also uses Concept Maps as media for knowledge representation. Resumo. Esse artigo apresenta o Versus, um ambiente virtual de aprendizagem para mediar as atividades do método de aprendizagem cooperativa denominado Controvérsia Acadêmica. Apesar de ser bastante conhecido, não há na literatura levantada, relato de uso desse método em situações não presenciais ou com o auxílio do computador. No Versus, os Mapas Conceituais foram utilizados como mídia para representação do conhecimento.

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UPNs: User-provided Networks-Technical Report: Living-examples, challenges, advantages

Throughout the history of the Internet, several technologies and networking architectures have em... more

An alternative approach for header compression over wireless mesh networks

… , 2009. WAINA'09. …, 2009

Header compression techniques theoretically can improve the speech quality of multimedia applicat... more Header compression techniques theoretically can improve the speech quality of multimedia applications. However it introduces a new impairment directly related to the loss of packets, that can impact negatively on the quality. Its deployment over wireless mesh networks needs special treatment due to the usually high loss rates of such a network. This work shows an evaluation of an alternative approach for header compression over wireless mesh networks. Experiments by means of stochastic simulation showed that under some network characteristics the proposed approach shows significant improvements in the packet loss.

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Header compression for VoIP over multi-hop wireless mesh networks

… , 2008. ISCC 2008. …, 2008

With the increasing deployment of wireless mesh net-works, the usage of a number of services in s... more

Managing sensing and cooperation to analyze PUE attacks in Cognitive Radio Ad Hoc Networks

ABSTRACT In Cognitive Radio Ad Hoc Networks (CRAHNs), malicious Secondary Users can exploit CR (C... more ABSTRACT In Cognitive Radio Ad Hoc Networks (CRAHNs), malicious Secondary Users can exploit CR (Cognitive Radio) capabilities to perform Primary User Emulation Attacks (PUEA). These attacks pretend the transmission of a Primary User (PU), giving to malicious users the priority of using licensed frequencies over well-behaved unlicensed Secondary Users (SU). Since CRAHNs are envisioned as a solution for the frequency spectrum underutilization, PUEA is a threat, compromising these networks operation and easily resulting in Denial of Services (DoS). While the state of the art has focused on evolving architectural design issues (i.e. centralized non-cooperative to decentralized cooperative schemes) another key design aspect was left behind: the decision criterion, which is typically assumed as unique metric (e.g. the received signal power). To fill this gap, we propose INCA, a novel multIple criteria scheme for the deceNtralized and Cooperative Analysis of the PUEA presence in CRAHNs. INCA follows two phases. On the first, each SU employs multiple criteria to define a hypothesis about the potential existence of attacks; whereas on the second, these hypotheses are exchanged among neighbors, and each SU employs the Bayes theorem to calculate the final probability of a PUEA. Simulation results show the improvement and effectiveness of the multi-criteria approach.

Translating Full Duplexity into Capacity Gains for the High-Priority Traffic Classes of IEEE 802.11

A flexible multi-criteria scheme to detect primary user emulation attacks in CRAHNs

ABSTRACT Cognitive Radio Ad Hoc Networks (CRAHNs) are prone to Primary User Emulation Attacks (PU... more ABSTRACT Cognitive Radio Ad Hoc Networks (CRAHNs) are prone to Primary User Emulation Attacks (PUEAs), a particular security issue in which malicious unlicensed users manipulate their cognitive radio parameter values to monopolize the spectrum usage pretending transmissions of Primary Users. Works in the literature propose to detect or mitigate these attacks, however they are based on network architectural approaches and node operation, without intending to be flexible to unexpected attack behaviors and prepared for attack adaptations that intend to circumvent defense mechanisms. Existing proposals are intrinsically tied to predefined criteria, and the addition of new one requires the design of a different solution. Intending to fill this gap, we propose INCA, a novel multIple criteria scheme for a deceNtralized and Cooperative Analysis of the PUEA presence in CRAHNs. INCA is composed of two phases that employ, respectively, the Normalized Weighted Additive Utility Function to achieve flexibility, and the Bayes theorem to provide a distributed cooperation among nodes, in which the detection of the presence of attacks by a node is partially conditional to the detection by other nodes. Results from exhaustive simulations show that INCA can improve the analysis of the presence of PUEA in all evaluated scenarios, mostly when both phases are applied.

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