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신석주 朝鮮大學校 電子情報通信硏究所 2006 電子情報通信硏究所論文集 Vol.9 No.1
Performance of the access channel in cdma2000 and random access channel in WCDMA is studied in this paper. In such systems, the accessing user can degrade the performance of existing users by introducing extra interference such as packet collision and blocking. We study how much the random access channel in WCDMA is superior to an access channel in cdma2000 by employing more complicated channel structure. In addition, channel occupancy which is a measure of interference to other channel types in system is also investigated, respectively. Simulation is carried out to compare the performance of these channels under fixed frame error rates and varying offered load conditions.
A Pixel-based Encryption Method for Privacy-Preserving Deep Learning Models
Ijaz Ahmad,Seokjoo Shin 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2
In the recent years, pixel-based perceptual algorithms have been successfully applied for privacy-preserving deep learning (DL) based applications. However, their security has been broken in subsequent works by demonstrating a chosen-plaintext attack. In this paper, we propose an efficient pixel-based perceptual encryption method. The method provides a necessary level of security while preserving the intrinsic properties of the original image. Thereby, can enable deep learning (DL) applications in the encryption domain. The method is substitution based where pixel values are XORed with a sequence (as opposed to a single value used in the existing methods) generated by a chaotic map. We have used logistic maps for their low computational requirements. In addition, to compensate for any inefficiency because of the logistic maps, we use a second key to shuffle the sequence. We have compared the proposed method in terms of encryption efficiency and classification accuracy of the DL models on them. We have validated the proposed method with CIFAR datasets. The analysis shows that when classification is performed on the cipher images, the model preserves accuracy of the existing methods while provides better security.
Precise-Optimal Frame Length Based Collision Reduction Schemes for Frame Slotted Aloha RFID Systems
( Sunil Dhakal ),( Seokjoo Shin ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.1
An RFID systems employ efficient Anti-Collision Algorithms (ACAs) to enhance the performance in various applications. The EPC-Global G2 RFID system utilizes Frame Slotted Aloha (FSA) as its ACA. One of the common approaches used to maximize the system performance (tag identification efficiency) of FSA-based RFID systems involves finding the optimal value of the frame length relative to the contending population size of the RFID tags. Several analytical models for finding the optimal frame length have been developed; however, they are not perfectly optimized because they lack precise characterization for the timing details of the underlying ACA. In this paper, we investigate this promising direction by precisely characterizing the timing details of the EPC-Global G2 protocol and use it to derive a precise-optimal frame length model. The main objective of the model is to determine the optimal frame length value for the estimated number of tags that maximizes the performance of an RFID system. However, because precise estimation of the contending tags is difficult, we utilize a parametric-heuristic approach to maximize the system performance and propose two simple schemes based on the obtained optimal frame length―namely, Improved Dynamic-Frame Slotted Aloha (ID-FSA) and Exponential Random Partitioning-Frame Slotted Aloha (ERP-FSA). The ID-FSA scheme is based on the tag set estimation and frame size update mechanisms, whereas the ERP-FSA scheme adjusts the contending tag population in such a way that the applied frame size becomes optimal. The results of simulations conducted indicate that the ID-FSA scheme performs better than several well-known schemes in various conditions, while the ERP-FSA scheme performs well when the frame size is small.
ML Approaching MIMO Detection Based on Orthogonal Projection
Seungjae Bahng,Seokjoo Shin,Youn-Ok Park IEEE 2007 IEEE COMMUNICATIONS LETTERS Vol.11 No.6
<P>A detection algorithm for spatially multiplexed multiple input multiple output (MIMO) systems is proposed. The receiver first estimates the MIMO channel and rearranges the layers according to the measured SNRs. To determine the candidate vectors, an orthogonal projection combined with the M-algorithm is used. Without performing the exhaustive full search of the maximum likelihood (ML) method, the proposed algorithm can reach the performance which is closely akin to the ML method. The computational complexity markedly decreases: 0.66% over the ML method in terms of the number of real multiplications.</P>
향상된 색상 구성요소 스크램블링을 사용한 블록 기반 지각 암호화 알고리즘
Ijaz Ahmad,Seokjoo Shin 한국차세대컴퓨팅학회 2022 한국차세대컴퓨팅학회 학술대회 Vol.2022 No.05
Perceptual encryption (PE) is becoming popular for protecting image data as they are computationally inexpensive and retain certain image properties that are necessary for compression. PE methods not only provide security during transmission of image data but can also enable privacy-preserving computations on them. However, the presence of color information in the cipher image makes the existing PE algorithms vulnerable to jigsaw puzzle attacks. Therefore, this paper presents an extension of block-based PE methods that utilizes different keys for each color component when changing orientation of a block and pixel values in a block. Thus, offers better encryption performance as the color distribution of the original is changed significantly and the keyspace is expanded. The analysis on Tecnick dataset shows that the proposed PE method preserves compression performance of the existing methods while improving their encryption efficiency. In addition, the main advantage of the proposed method is that of being compatible with a widely used JPEG image standard, which makes it suitable for different outsourced multimedia applications such as, privacy-preserving deep learning, cloud-based photo storage, and social networking services.