Abstract:Resumo-A codificac ¸ão wavelet surgiu como uma técnica de codificac ¸ão de canal alternativa para minimizar os efeitos nocivos dos canais de comunicac ¸ão sem fio caracterizados pelo desvanecimento. Diferente de técnicas clássicas de codificac ¸ão, nas quais o ganho de codificac ¸ão surge através da adic ¸ão de uma redundância controlada a informac ¸ão, a robustez conseguida pela codificac ¸ão wavelet contra os efeitos do desvanecimento ocorre em func ¸ão de uma diversidade temporal gerada sobre a informac ¸ão… Show more
“…e condition given by equation 3denotes that the rows of a wavelet matrix with rank m and gender g have a norm m 1/2 and are mutually orthogonal to each other, even when shifted by a multiple of m. Equation 2shows that the sum of the elements in the first row of the wavelet matrix is equal to the matrix rank, while the sum of the elements in each one of the remaining rows is zero [4].…”
Section: Concepts Of Wavelet Codingmentioning
confidence: 99%
“…where I is the identity matrix with rank m. From each element z i of vector Z, the values assumed by the transmitted bits x i can be estimated by [4] x…”
Section: Wavelet Decodingmentioning
confidence: 99%
“…However, when such diversity is provided by appropriate techniques, prominent advantages can be achieved by maintaining the spectral e ciency of the system at appropriate values. Wavelet coding is a transmission technique that can be used for this purpose [4].…”
Section: Introductionmentioning
confidence: 99%
“…Wavelet coding was initially proposed by Tzannes and Tzannes [5], being characterized by using wavelet matrices for information coding [2]. Because of the orthogonality property of the rows in the wavelet matrices, the information can be retrieved at the receiver through a bank of correlators that match the rows used for coding [4].…”
Section: Introductionmentioning
confidence: 99%
“…Simplicity regarding the wavelet coding process led to the investigation of this transmission technique applied to di erent communication scenarios, such as at fading channels [6], frequency selective channels [4], analysis of channel estimation errors [7,8], and identi cation of modulation schemes designed by genetic algorithms [9], in OFDM systems on a 4.9 Gbps W-Band Radio-over-Fiber Link [10] and in wireless adaptive control systems [11].…”
In mobile communication systems, the signals propagate through multipath over time-varying channels, which are subject to distortion caused by fading and Doppler shifts. In order to minimize such distortions, coding techniques and transmission diversity can be employed, e.g., wavelet coding. In this work, the wavelet coding is investigated in scenarios of cognitive radio systems with dynamic spectrum access. Cognitive radio systems with dynamic spectrum access should be able to sense unoccupied frequency bands for opportunistic transmissions, as well as detect the presence of primary users when they occupy their licensed spectrum. Therefore, an essential element for the accurate operation of cognitive radio systems encoded by wavelet coding is the ability to sense the signals encoded by this technique. It is effectively demonstrated that the possibility of sensing such signals is associated with a suitable design of the signal constellation used in the modulation of the coded symbols. The constellation design of these is performed via genetic algorithms using a multiobjective optimization approach. The developed system is evaluated according to the robustness to time-varying flat fading through a bit error probability (BER) versus Eb/N0 analysis. The spectral sensing ability is also addressed employing the cyclostationary analysis. The results denote the feasibility of using wavelet coding in radio scenarios with dynamic spectrum access, with good performance in terms of BER and signal detection rates.
“…e condition given by equation 3denotes that the rows of a wavelet matrix with rank m and gender g have a norm m 1/2 and are mutually orthogonal to each other, even when shifted by a multiple of m. Equation 2shows that the sum of the elements in the first row of the wavelet matrix is equal to the matrix rank, while the sum of the elements in each one of the remaining rows is zero [4].…”
Section: Concepts Of Wavelet Codingmentioning
confidence: 99%
“…where I is the identity matrix with rank m. From each element z i of vector Z, the values assumed by the transmitted bits x i can be estimated by [4] x…”
Section: Wavelet Decodingmentioning
confidence: 99%
“…However, when such diversity is provided by appropriate techniques, prominent advantages can be achieved by maintaining the spectral e ciency of the system at appropriate values. Wavelet coding is a transmission technique that can be used for this purpose [4].…”
Section: Introductionmentioning
confidence: 99%
“…Wavelet coding was initially proposed by Tzannes and Tzannes [5], being characterized by using wavelet matrices for information coding [2]. Because of the orthogonality property of the rows in the wavelet matrices, the information can be retrieved at the receiver through a bank of correlators that match the rows used for coding [4].…”
Section: Introductionmentioning
confidence: 99%
“…Simplicity regarding the wavelet coding process led to the investigation of this transmission technique applied to di erent communication scenarios, such as at fading channels [6], frequency selective channels [4], analysis of channel estimation errors [7,8], and identi cation of modulation schemes designed by genetic algorithms [9], in OFDM systems on a 4.9 Gbps W-Band Radio-over-Fiber Link [10] and in wireless adaptive control systems [11].…”
In mobile communication systems, the signals propagate through multipath over time-varying channels, which are subject to distortion caused by fading and Doppler shifts. In order to minimize such distortions, coding techniques and transmission diversity can be employed, e.g., wavelet coding. In this work, the wavelet coding is investigated in scenarios of cognitive radio systems with dynamic spectrum access. Cognitive radio systems with dynamic spectrum access should be able to sense unoccupied frequency bands for opportunistic transmissions, as well as detect the presence of primary users when they occupy their licensed spectrum. Therefore, an essential element for the accurate operation of cognitive radio systems encoded by wavelet coding is the ability to sense the signals encoded by this technique. It is effectively demonstrated that the possibility of sensing such signals is associated with a suitable design of the signal constellation used in the modulation of the coded symbols. The constellation design of these is performed via genetic algorithms using a multiobjective optimization approach. The developed system is evaluated according to the robustness to time-varying flat fading through a bit error probability (BER) versus Eb/N0 analysis. The spectral sensing ability is also addressed employing the cyclostationary analysis. The results denote the feasibility of using wavelet coding in radio scenarios with dynamic spectrum access, with good performance in terms of BER and signal detection rates.
Resumo-A codificação wavelet de canal objetiva reduzir efeitos deletérios de canal de comunicação sem fio sobre um sinal transmitido e emprega comumente uma decodificação símbolo a símbolo. Este trabalho investiga o emprego de decodificador de Viterbi para códigos wavelet e compara, em termos da taxa de erro de bits, o desempenho do sistema operando sobre canal com desvanecimento Rayleigh, quando aplicada a decodificação de Viterbi, em relação à decodificação tradicional. Os resultados de simulação demonstraram que a decodificação de sequência proporciona desempenho superior à decodificação símbolo a símbolo.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.