Energy and Spectral Efficiencies Trade-off in Multiple Access Interference-Aware Networks

Alvaro R. C. Souza, Taufik Abraão, Fábio R. Durand, Lucas H. Sampaio, Paul Jean E. Jeszensky

DOI: 10.14209/sbrt.2012.1

Keywords: Energy efficiency spectral efficiency DS/CDMA distributed power control

Abstract

This work analyzes the power allocation problem in DS/CDMA systems under the energy efficiency (EE) metric, maximizing the transmitted information per energy unit. As the spectral efficiency (SE) is one of the most important performance metrics and is maximized with infinite power, the trade-off between these two metrics (EE-SE trade-off) are investigated and characterized in relation to multiple-access interference (MAI) power level, resulting that the optimum operating point is the max-EE point and the EE limitation imposed by MAI. To corroborate these results, we develop two algorithms for power allocation based on distributed instantaneous SINR level.

Download

Chain of finite rings and construction of BCH Codes

Antonio Aparecido de Andrade, Tariq Shah, Attiq Qamar

DOI: 10.14209/sbrt.2012.3

Keywords: Units of local ring BCH code McCoy rank direct product of local rings

Abstract

For a non negative integer t, let A0 ⊂ A1 ⊂ · · · ⊂ At−1 ⊂ At be a chain of unitary commutative rings, where each Ai is constructed by the direct product of suitable Galois rings with multiplicative group A ∗ i of units, and K0 ⊂ K1 ⊂ · · · ⊂ Kt−1 ⊂ Kt be the corresponding chain of unitary commutative rings, where each Ki is constructed by the direct product of corresponding residue fields of given Galois rings, with multiplicative groups K ∗ i of units. This correspondence presents four different type of construction techniques of generator polynomials of sequences of BCH codes having entries from A ∗ i and K ∗ i for each i, where 0 ≤ i ≤ t. The BCH codes constructed in [1] are limited to given code rate and error correction capability, however, proposed work offers a choice for picking a suitable BCH code concerning code rate and error correction capability.

Download

Metaheurísticas Aplicadas a Gerência de Recursos de Rádio em Redes Multi-Acesso 4G

Yuri V. L. de Melo, Vicente A. de Sousa Jr.

DOI: 10.14209/sbrt.2012.6

Keywords: Redes 4G Algoritmo Genético Tabu Search,CRRM Seleção de Acesso

Abstract

As redes de comunicações sem fio estão se tornando mais heterogêneas tanto em termos tecnológicos como em modelos de negócios das operadoras. Essa tendência, aliada ao crescimento da demanda por novos serviços, reforça a ideia que as redes modernas de comunicação sem fio deverão ser capazes de prover múltiplos serviços sob uma arquitetura de rede unificada, composta de várias redes de acesso de rádio, a chamada rede Multi-Acesso. Este trabalho de iniciação científica tem como objetivo o estudo de estratégias de Gerência de Recursos de Rádio em redes Multi-Acesso, mas especificamente a maneira de alocar usuários em tais redes, i.e., a Seleção de Acesso. Em [1], uma abordagem via otimização foi adotada e a busca da solução ótima do problema de seleção de acesso foi obtida através de Algoritmos Genéticos. Este trabalho tem como objetivo estender os estudos apresentados em [1] através do uso do algoritmo Tabu Search [2] como estratégia de busca da solução ótima. A intenção e obter soluções com menor custo computacional em relação a estratégia usada anteriormente. As soluções propostas foram prototipadas por meio de simulação e como objetivo final, o desempenho das mesmas foi avaliado e comparado.

Download

Performance evaluation of QoS in wireless networks using IEEE 802.11e

Laio B. Vilas Boas, Pedro M. C. Massolino, Rafael T. Possignolo, Cintia B. Margi, Regina M. Silveira

DOI: 10.14209/sbrt.2012.7

Keywords: QoS IEEE 802.11e Simulation MANET Ad Hoc Wireless

Abstract

The increase demand for Quality of Service (QoS) in computer networks and the recent popularization of wireless networks required a standard to bring QoS to such networks. The IEEE 802.11e, a complement to the 802.11 family, answers to these requirements implementing such QoS mechanisms. The main contribution of this work is to provide an evaluation of the final IEEE 802.11e standard. Using the ns-2 simulator, we compare it against IEEE 802.11a with a FIFO queue, as well as priority and round robin arbiter queues. We also consider different scenarios, both in ad hoc and infra-structure modes. Our results show that the IEEE 802.11e can improve the QoS of a wireless network in all scenarios.

Download

Simulação no COMSOL de Diferentes Configurações de Nanoantenas Cilíndricas

Gustavo L. Silvano, Karlo Q. da Costa

DOI: 10.14209/sbrt.2012.215

Keywords: Nanoantena nanoantena cilíndrica nanodipolo nanobarra onda plana THz COMSOL plasmônica.

Abstract

O presente trabalho visa estudar o comportamento de nanoantenas quando excitados de várias formas, além de uma análise das respostas em relação à geometria da antena. Será utilizado uma nanobarra e um nanodipolo sendo excitados por uma onda plana, e em seguida o nanodipolo será excitado por uma fonte de tensão. Para isso será utilizado o software COMSOL Multiphysics 3.4, e os resultados serão comparados com um programa baseado no Método dos Momentos (MoM), além de referencias provindas da literatura.

Download

Parameter Optimization in ACO-MuD DS/CDMA

José Carlos Marinello Filho, Reginaldo Nunes de Souza, and Taufik Abrão

DOI: 10.14209/sbrt.2012.216

Keywords: Ant colony intelligence multiuser detection input parameters optimization computational complexity DS-CDMA

Abstract

A simple and efficient methodology for tuning the input parameters applied to the ant colony optimization multiuser detection (ACO-MUD) in direct sequence code division multiple access (DS-CDMA) is proposed. The motivation in using a heuristic approach is due to the nature of the NP complexity posed by the wireless multiuser detection optimization problem. The challenge is to obtain suitable data detection performance in solving the associated hard complexity problem in a polynomial time. Previous results indicated that the application of heuristic search algorithms in several wireless optimization problems have been achieved excellent performance-complexity tradeoffs. Regarding different system operation and channels scenarios, a complete input parameters optimization procedure for the ACO- MUD is provided herein, which represents the major contribution of this work. The performance of the ACO-MUD is analyzed via Monte-Carlo simulations. Simulation results show that, after convergence, the performance reached by the ACO-MUD is much better than the conventional detector (CD), and somewhat close to the optimum likelihood detector (OMuD). Flat Rayleigh channels is initially considered, but the input parameter optimization methodology is straightforward applicable to selective fading channels scenarios, as well as to joint time-spatial wireless channels diversities.

Download

Improving the Performance of Adaptive Modulation Systems by the Modulation Diversity Technique

Rafael Fernandes Lopes, Waslon Terllizzie Araujo Lopes, Marcelo Sampaio de Alencar, Wamberto Jose Lira de Queiroz

DOI: 10.14209/sbrt.2012.9

Keywords: Adaptive modulation Modulation diversity Per- formance evaluation.

Abstract

This paper proposes a combination of the adap- tive modulation with the modulation diversity technique, which associates a suitable constellation rotation angle θ with the independent interleaving of the symbol components. Since the optimal rotation angle depends on the chosen modulation order and fading severity degree, the constellation rotation angle is dynamically changed according to the channel parameters. A new approximate expression for the pairwise error probability (PEP) is derived to allow the dynamic evaluation of the optimal value of θ. A performance analysis considering a system with parameters similar to the UMTS/HSDPA protocol is performed. The evaluation of the proposed system has shown that significant gains, in terms of the average system bit error rate, are achieved for high signal-to-noise ratio values.

Download

Hybrid Local Search Polynomial-Expanded Linear Multiuser Detector

Reinaldo Gotz, Taufik Abrão

DOI: 10.14209/sbrt.2012.8

Keywords: suboptimum search algorithms polynomial ex- panded multiuser detection Gerschgorin circles DS/CDMA

Abstract

In order to reduce computational complexity in- herent to cross-correlation matrix inversion in DS/CDMA sys- tem, this work proposes a hybrid multiuser detector based on polynomial expansion (PE-MuD) followed by a low complexity local search procedure, aiming at obtaining a near-optimum multiuser bit-error-rate (BER) performance, but with an amount of computational processing saving time. The proposed hy- brid PE-MuD receiver topology is analyzed under realistic wireless mobile channels, as well as useful system operation scenarios. Simulations results have indicated an improvement in performance-complexity trade-off regarding the classical linear multiuser detectors (MuD) performance, particularly, the mean square error minimization-based detector (MMSE).

Download

Análise da Impedância de Entrada de Nanodipolos Cilíndricos Utilizando o Método dos Momentos

Janilson L. de Souza, Karlo Q. da Costa

DOI: 10.14209/sbrt.2012.11

Keywords: Nanodipolos metálicos cilíndricos Método dos Momentos (MoM) impedância superficial finita.

Abstract

Este artigo apresenta uma análise da impedância de entrada de nanodipolos metálicos cilíndricos utilizando o Método dos Momentos (MoM) para solução da equação integral do campo elétrico, com aproximação linear da corrente, funções base senoidal e impedância superficial finita. São apresentadas algumas simulações variando parâmetros geométricos da nanoestrutura, onde serão comparadas com os resultados calculados pelo software Comsol Multiphysic.

Download

IEEE 802.11n: On Performance of Channel Estimation Schemes over OFDM MIMO Spatially- Correlated Frequency Selective Fading TGn Channels

Roger Pierre Fabris Hoefel

DOI: 10.14209/sbrt.2012.12

Keywords: 802.11n; MIMO OFDM; channel estimation

Abstract

In this paper, we investigate the performance of Least Square (LS), Time Delay Truncation (TDT) and Model- Based (MB) channel estimation schemes specially designed to operate in a orthogonal frequency division multiplexing (OFDM) multiple input multiple output (MIMO) IEEE 802.11n system. We conclude, founded on analytical and simulation results over spatially correlated frequency selective TGn channels, that the TDT scheme presents the best performance in low signal-to-noise ratio (SNR) regime, whereas the performance of the LS scheme outperforms substantially the TDT and MB channel estimation schemes in high SNR regime.

Download