Improved Energy Detector for Wideband Spectrum Sensing in Cognitive Radio Networks

In this paper, an improved energy detector for a wideband spectrum sensing is proposed. For a better detection of the spectrum holes the overall band is divided into equal non-overlapping sub-bands. The main objective is to determine the detection thresholds for each of these subbands jointly. By defining the problem as an optimization problem, we aim to find the maximum aggregated opportunistic throughput of cognitive radio networks. Introducing practical constraints to this optimization problem will change the problem into a convex and solvable one. The results of this paper show that the proposed improved energy detector will increase the aggregated throughput considerably

Multiple Access Channel with Common Message and Secrecy constraint

In this paper, we study the problem of secret communication over a multiple-access channel with a common message. Here, we assume that two transmitters have confidential messages, which must be kept secret from the wiretapper (the second receiver), and both of them have access to a common message which can be decoded by the two receivers. We call this setting as Multiple-Access Wiretap Channel with Common message (MAWC-CM). For this setting, we derive general inner and outer bounds on the secrecy capacity region for the discrete memoryless case and show that these bounds meet each other for a special case called the switch channel. As well, for a Gaussian version of MAWC-CM, we derive inner and outer bounds on the secrecy capacity region. Providing numerical results for the Gaussian case, we illustrate the comparison between the derived achievable rate region and the outer bound for the considered model and the capacity region of compound multiple access channel.Comment: 11 pages, 7 figures, Accepted in IET Communication

DUKUNGAN SOSIAL PADA PENDERITA HIV/AIDS ATAU ODHA

Permasalahan sosial di Indonesia semakin hari semakain meningkat. Permasalahan sosial yang berhubungan dengan perilaku dan kesehatan seperti HIV dan AIDS menjadi suatu hal yang sebaiknya mendapatkan penanganan serius. AIDS merupakan singkatan dari Acquired Immune Deficiency Syndrome yaitu suatu kumpulan gejala yang ditimbulkan oleh virus kekebalan tubuh manusia. Virus tersebut dinamakan HIV (Human Immunodeficiency Virus). Perlu adanya dukungan sosial untuk meningkatkan rasa percaya diri dan untuk mengembangkan kualitas hidup Odha. Seperti yang didefinisikan oleh Sarafino bahwa ukungan sosial adalah kenyamanan, perhatian, penghargaan, maupun bantuan dalam bentuk lainnya yang diterimanya individu dari orang lain ataupun dari kelompok. Berdasarkan hasil observasi dan wawancara dengan salah satu subjek penderita Odha bahwa dukungan keluarga, teman sebaya, dan lingkungan sangat membatu kelancaran aktivitasnya sehari-hari. Adanya dukungan keluarga terutama yang membangkitkan kembali mental individu dalam menghadapi kehidupan, dukungan lingkungan yang memberikan tempat untuk bersosialisasi membuat individu bersemngat lagi. Kata Kunci: dukungan sosial, HIV, AIDS, ODH

Design of Finite-Length Irregular Protograph Codes with Low Error Floors over the Binary-Input AWGN Channel Using Cyclic Liftings

We propose a technique to design finite-length irregular low-density parity-check (LDPC) codes over the binary-input additive white Gaussian noise (AWGN) channel with good performance in both the waterfall and the error floor region. The design process starts from a protograph which embodies a desirable degree distribution. This protograph is then lifted cyclically to a certain block length of interest. The lift is designed carefully to satisfy a certain approximate cycle extrinsic message degree (ACE) spectrum. The target ACE spectrum is one with extremal properties, implying a good error floor performance for the designed code. The proposed construction results in quasi-cyclic codes which are attractive in practice due to simple encoder and decoder implementation. Simulation results are provided to demonstrate the effectiveness of the proposed construction in comparison with similar existing constructions.Comment: Submitted to IEEE Trans. Communication

Lowering the Error Floor of LDPC Codes Using Cyclic Liftings

Cyclic liftings are proposed to lower the error floor of low-density parity-check (LDPC) codes. The liftings are designed to eliminate dominant trapping sets of the base code by removing the short cycles which form the trapping sets. We derive a necessary and sufficient condition for the cyclic permutations assigned to the edges of a cycle $c$ of length $\ell(c)$ in the base graph such that the inverse image of $c$ in the lifted graph consists of only cycles of length strictly larger than $\ell(c)$. The proposed method is universal in the sense that it can be applied to any LDPC code over any channel and for any iterative decoding algorithm. It also preserves important properties of the base code such as degree distributions, encoder and decoder structure, and in some cases, the code rate. The proposed method is applied to both structured and random codes over the binary symmetric channel (BSC). The error floor improves consistently by increasing the lifting degree, and the results show significant improvements in the error floor compared to the base code, a random code of the same degree distribution and block length, and a random lifting of the same degree. Similar improvements are also observed when the codes designed for the BSC are applied to the additive white Gaussian noise (AWGN) channel