Perancangan Automatic Gain Control pada Modem Orthogonal Frequency Division Multiplexing (OFDM) dalam rentang Frekuensi Audio

Orthogonal frequency-division multiplexing (OFDM) merupakan metode modulasi digital di mana sebuah sinyal dibagi menjadi beberapa saluran subcarrier pada frekuensi yang berbeda. Teknologi ini cocok untuk televisi digital, dan sedang dipertimbangkan sebagai metode untuk mendapatkan kecepatan tinggi transmisi data digital melalui saluran telepon konvensional. Pada penelitian ini sistem ini akan diaplikasikan untuk mengirimkan suara secara real time. Salah satu permasalahan dalam pengembangan sistem OFDM ialah masalah peningkatan data rate OFDM dengan menggunakan Mapping 64 QAM dan penambahan Automatic Gain Control (AGC) untuk memperbaiki performa sinyal pada receiver. Dengan peningkatan Mapping pada sistem diharapkan jumlah sinyal yang dioperasikan menjadi lebih besar mencapai 8 kpps. Berdasarkan hasil simulasi dan implementasi Automatic Gain Control pada modem OFDM dalam jangkauan frekuensi audio dapat disimpulkan Automatic Gain Control dapat mengatasi fluktuasi sinyal suara yang diterima setelah melewati kanal terutama dalam penggunaan modulasi yang cukup besar seperti 64 QAM. Hasil simulasi menunjukkan kemampuan Automatic Gain Control dengan metode ini mampu secara efektif memperbaiki performa suara pada walaupun dari sisi jumlah bit error masih menunjukkan hasil yang kurang baik terhadap variasi frekuensi offset, panjang FFT dan variasi frekuensi sampling. Kata kunci : Automatic Gain Control, OFDM, mapping, FF

Portfolio peak algorithms achieving superior performance for maximizing throughput in WiMAX networks

The Mobile WiMAX IEEE 802.16 standards ensure provision of last mile wireless access, variable and high data rate, point to multi-point communication, large frequency range and QoS (Quality of Service) for various types of applications. The WiMAX standards are published by the Institute of Electric and Electronic Engineers (IEEE) and specify the standards of services and transmissions. However, the way how to run these services and when the transmission should be started are not specified in the IEEE standards and it is up to computer scientists to design scheduling algorithms that can best meet the standards. Finding the best way to implement the WiMAX standards through designing efficient scheduler algorithms is a very important component in wireless systems and the scheduling period presents the most common challenging issue in terms of throughput and time delay. The aim of the research presented in this thesis was to design and develop an efficient scheduling algorithm to provide the QoS support for real-time and non-real-time services with the WiMAX Network. This was achieved by combining a portfolio of algorithms, which will control and update transmission with the required algorithm by the various portfolios for supporting QoS such as; the guarantee of a maximum throughput for real-time and non-real-time traffic. Two algorithms were designed in this process and will be discussed in this thesis: Fixed Portfolio Algorithms and Portfolio Peak Algorithm. In order to evaluate the proposed algorithms and test their efficiency for IEEE 802.16 networks, the authors simulated the algorithms in the NS2 simulator. Evaluation of the proposed Portfolio algorithms was carried out through comparing its performance with those of the conventional algorithms. On the other hand, the proposed Portfolio scheduling algorithm was evaluated by comparing its performance in terms of throughput, delay, and jitter. The simulation results suggest that the Fixed Portfolio Algorithms and the Portfolio Peak Algorithm achieve higher performance in terms of throughput than all other algorithms. Keywords: WiMAX, IEEE802.16, QoS, Scheduling Algorithms, Fixed Portfolio Algorithms, and Portfolio Peak Algorithms.The Mobile WiMAX IEEE 802.16 standards ensure provision of last mile wireless access, variable and high data rate, point to multi-point communication, large frequency range and QoS (Quality of Service) for various types of applications. The WiMAX standards are published by the Institute of Electric and Electronic Engineers (IEEE) and specify the standards of services and transmissions. However, the way how to run these services and when the transmission should be started are not specified in the IEEE standards and it is up to computer scientists to design scheduling algorithms that can best meet the standards. Finding the best way to implement the WiMAX standards through designing efficient scheduler algorithms is a very important component in wireless systems and the scheduling period presents the most common challenging issue in terms of throughput and time delay. The aim of the research presented in this thesis was to design and develop an efficient scheduling algorithm to provide the QoS support for real-time and non-real-time services with the WiMAX Network. This was achieved by combining a portfolio of algorithms, which will control and update transmission with the required algorithm by the various portfolios for supporting QoS such as; the guarantee of a maximum throughput for real-time and non-real-time traffic. Two algorithms were designed in this process and will be discussed in this thesis: Fixed Portfolio Algorithms and Portfolio Peak Algorithm. In order to evaluate the proposed algorithms and test their efficiency for IEEE 802.16 networks, the authors simulated the algorithms in the NS2 simulator. Evaluation of the proposed Portfolio algorithms was carried out through comparing its performance with those of the conventional algorithms. On the other hand, the proposed Portfolio scheduling algorithm was evaluated by comparing its performance in terms of throughput, delay, and jitter. The simulation results suggest that the Fixed Portfolio Algorithms and the Portfolio Peak Algorithm achieve higher performance in terms of throughput than all other algorithms. Keywords: WiMAX, IEEE802.16, QoS, Scheduling Algorithms, Fixed Portfolio Algorithms, and Portfolio Peak Algorithms