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Unsupervised Log Message Anomaly Detection
Amir Farzad,T. Aaron Gulliver 한국통신학회 2020 ICT Express Vol.6 No.3
Log messages are now broadly used in cloud and software systems. They are important for classification and anomaly detection as millions of logs are generated each day. In this paper, an unsupervised model for log message anomaly detection is proposed which employs Isolation Forest and two deep Autoencoder networks. The Autoencoder networks are used for training and feature extraction, and then for anomaly detection, while Isolation Forest is used for positive sample prediction. The proposed model is evaluated using the BGL, Openstack and Thunderbird log message data sets. The results obtained show that the number of negative samples predicted to be positive is low, especially with Isolation Forest and one Autoencoder. Further, the results are better than with other well-known models.
OPTIMAL LINEAR CODES OVER ℤ<sub>m</sub>
Dougherty, Steven T.,Gulliver, T. Aaron,Park, Young-Ho,Wong, John N.C. Korean Mathematical Society 2007 대한수학회지 Vol.44 No.5
We examine the main linear coding theory problem and study the structure of optimal linear codes over the ring ${\mathbb{Z}}_m$. We derive bounds on the maximum Hamming weight of these codes. We give bounds on the best linear codes over ${\mathbb{Z}}_8$ and ${\mathbb{Z}}_9$ of lengths up to 6. We determine the minimum distances of optimal linear codes over ${\mathbb{Z}}_4$ for lengths up to 7. Some examples of optimal codes are given.
Performance Analysis of SEC-SC System
Lingwei Xu,Hao Zhang,T .Aaron Gulliver 보안공학연구지원센터 2015 International Journal of Future Generation Communi Vol.8 No.6
In order to achieve the balance between implementation complexity and system performance, a new hybrid combining technique named SEC-SC is proposed in this paper, which is composed of switch-and-examine combining (SEC) and selection combining(SC).The average symbol error probability (ASEP) and outage probability (OP) of the SEC-SC system over N-Nakagami fading channels is investigated. The exact ASEP expressions are derived for several modulation schemes, including phase shift keying (PSK), quadrature amplitude modulation (QAM), and pulse amplitude modulation (PAM). The exact closed-form OP expressions are also presented. Then the ASEP and OP performance under different conditions is evaluated through numerical simulations to verify the analysis. The simulation results showed that the performance of the SEC-SC system is improved with the diversity branches and the fading coefficient increased, but the level of improvement is declined as the number of cascaded components increased.
Performance Analysis of Switched Diversity Combining System
Lingwei Xu,Hao Zhang,T. Aaron Gulliver 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.2
The average symbol error probability (ASEP) and outage probability (OP) performance of the switched diversity combining (SDC) system over N-Nakagami fading channels is investigated in this paper. The probability density function (PDF) of the signal-to-noise ratio (SNR) is used to derive exact and approximate ASEP expressions for phase shift keying (PSK) and pulse amplitude modulation (PAM). Exact closed-form expressions for OP of the SDC system are also presented. The ASEP and OP performance under different conditions is evaluated through numerical simulation to verify the analysis. Results are presented which show that the performance of the SDC system is improved when the number of diversity branches and the fading coefficient is increased, but is degraded as the number of cascaded components is increased.
Performance Analysis of IDF Relaying M2M Cooperative Networks over N-Nakagami Fading Channels
( Lingwei Xu ),( Hao Zhang ),( T. Aaron Gulliver ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.10
Exact average bit error probability (BEP) expressions for mobile-relay-based mobile-to-mobile (M2M) cooperative networks with incremental decode-and-forward (IDF) relaying over N-Nakagami fading channels are derived in this paper. The average BEP performance under different conditions is evaluated numerically to confirm the accuracy of the analysis. Results are presented which show that the fading coefficient, the number of cascaded components, the relative geometrical gain, and the power allocation parameter have a significant influence on the average BEP performance.
Outage Probability Analysis of the VAF Relaying M2M Networks
Lingwei Xu,Hao Zhang,Tingting Lu,T. Aaron Gulliver 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.5
Based on variable-gain amplify-and-forward (VAF) relaying scheme, the lower bound on outage probability (OP) of the mobile-relay-based mobile-to-mobile (M2M) networks over N-Nakagami fading channels is investigated in this paper. By the method of the harmonic mean of positive random variables, the exact closed form expression of the lower bound on OP is derived. Then the OP performance under different conditions is evaluated through numerical simulations. The numerical simulation results coincide with the theoretical results well, and the accuracy of the analytical results is verified. The simulation results showed that: the fading coefficient, the number of cascaded components, the relative geometrical gain, and the power-allocation parameter have an important influence on the OP performance.