Dynamic Optimization of Active Queue Management Routers to Improve Queue Stability

Radwan, Amr Korea Multimedia Society 2015 멀티미디어학회논문지 Vol.18 No.11

This paper aims to introduce the numerical methods for solving the optimal control theory to model bufferbloat problem. Mathematical tools are useful to provide insight for system engineers and users to understand better about what we are facing right now while experiment in a large-scale testbed can encourage us to implement in realistic scenario. In this paper, we introduce a survey of the numerical methods for solving the optimal control problem. We propose the dynamic optimization sweeping algorithm for optimal control of the active queue management. Simulation results in network simulator ns2 demonstrate that our proposed algorithm can obtain the stability faster than the others while still maintain a short queue length (≈10 packets) and low delay experience for arriving packets (0.4 seconds).

Resource Allocation for Device-to-Device Communications Reusing Uplink in Cellular Networks

Radwan, Amr Korea Multimedia Society 2015 멀티미디어학회논문지 Vol.18 No.12

Efficient spectrum sharing is an important issue in Device-to-Device (D2D) communications underlaying cellular networks as it can mitigate the interference to cellular users and improve the performance of the systems. In this paper, we formulate the radio resource allocation in D2D communications as a mixed nonlinear integer programing. We show the formulated problem is NP-hard and thus a polynomial time algorithm to solve is not possible. Since such a problem is very hard to obtain the optimal solution within a short running time, we instead propose a fast heuristic suboptimal algorithm to mitigate the interference caused to cellular users and improve the performance of the systems. Simulation results are provided to evaluate the performance of the proposed algorithm.

Optimal Control Scheme for SEIR Model in Viral Communications

Radwan, Amr The Korea Institute of Information and Commucation 2016 한국정보통신학회논문지 Vol.20 No.8

The susceptible, exposed, infectious, and recovered model (SEIR) is used extensively in the field of epidemiology. On the other hand, dissemination information among users through internet grows exponentially. This information spreading can be modeled as an epidemic. In this paper, we derive the mathematical model of SEIR in viral communication from the view of optimal control theory. Overall the methods based on classical calculus, In order to solve the optimal control problem, proved to be more efficient and accurate. According to Pontryagin's minimum principle (PMP) the Hamiltonian function must be optimized by the control variables at all points along the solution trajectory. We present our method based on the PMP and forward backward algorithm. In this algorithm, one should integrate forward in time for the state equations then integrate backward in time for the adjoint equations resulting from the optimality conditions. The problem is mathematically analyzed and numerically solved as well. 최근 SNS (Social Networking Services)를 통한 사용자들 간 정보 확산이 폭발적으로 증가하고 있다. SEIR (Susceptible-Exposed-Infectious-Recovered model)모델은 전염병 예측에 널리 사용되는 수학적 모델로, 이러한 정보 확산은 SEIR를 이용하여 모델링 할 수 있다. 본 논문에서는 SEIR모델을 이용하여 최적 제어 이론의 관점에서 SNS의 정보 확산 모델을 도출하였다. 본 논문에서는 PMP (Pontryagin's Minimum Principle)에 기반한 forward-backward algorithm을 제안하였다. 이 알고리즘은 전방과 후방으로 가면서 state와 adjoint equation들을 통합하면서 동작한다. 수치해석을 통해 정보 내용의 impact value와 birth rate이 작으면 작을수록 더 많은 노드들이 해로운 정보를 필터링하는 것을 보였다.

A Framework of Rate Control and Power Allocation in Multipath Lossy Wireless Networks

Radwan, Amr,Kim, Hoon Korea Multimedia Society 2016 멀티미디어학회논문지 Vol.19 No.8

Cross-layer design is a concept, which captures the dependencies and interactions and enables information sharing among layers in order to improve the network performance and security. There are two key challenges in wireless networks, lossy features of links and power assumption of network nodes. Cross-layer design of congestion control and power allocation in wireless lossy networks has been studied in the existing literature; however, there has been no contribution proposed in the literature that exploits the path diversity. In this paper, we are motivated to develop a cross-layer design of congestion control and power allocation, which takes into account lossy features of wireless links and transmission powers of network nodes and can be implemented in a distributed manner. Numerical simulation is conducted to illustrate the performance of our proposed algorithm and the comparison with current alternative approaches.

Performance Enhancement for Device-to-Device Under laying Cellular Network Using Coalition Formation Game

Radwan, Amr,Kim, Hoon Korea Multimedia Society 2016 멀티미디어학회논문지 Vol.19 No.8

Interference in device-to-device (D2D) communication underlaying cellular network needs to be elaborately investigated because of channel sharing. The objective is to improve the quality of D2D communications while maintaining high performance for cellular users. In this paper, we solve the above problem by jointly considering channel allocation and power control using coalition formation game. Our cooperative game theoric approach allows to enhance network-wide performance. We design a merge-and-split algorithm to deal with the complexity of the combinatorial structure in coalition formation problem. The analytical and numerical results show that our algorithm converges to a stable point which achieves high network performance.

The North Korea Human Rights Act of 2004 Basic Questions Answered

Radwan, Tarik 가톨릭대학교 법학부 인권법연구소 2005 인권법연구 Vol.- No.1

An Analysis of Effective Throughput in Distr ibuted Wir eless Scheduling

RADWAN AMR MOHAMED ADEL AHMED AHMED 한국멀티미디어학회 2016 멀티미디어학회논문지 Vol.19 No.2

Several distributed scheduling policies have been proposed with the objective of attaining the maximum throughput region or a guaranteed fraction throughput region. These policies consider only the theoretical throughput and do not account the lost in throughput due to the time complexity of implementing an algorithm in practice. Therefore, we propose a novel concept called effective throughput to characterize the actual throughput by taking into account the time complexity. Effective throughput can be viewed as the actual transmitted data without including the control message overhead. Numerical results demonstrate that in practical scheduling, time complexity significantly affects throughput. The performance of throughput degrades when the time complexity is high.

Large Hydromagnetic Axisymmetric Instability of a Streaming Gas Cylinder Surrounded by Bounded Fluid with Non Uniform Field

Radwan, Ahmed Elazab,Elogail, Mostafa Abdelrahman,Elazab, Nasser Elsaid Department of Mathematics 2007 Kyungpook mathematical journal Vol.47 No.4

The magnetohydrodynamic axisymmetric instability of a streaming gas jet surrounded by bounded fluid with non-uniform field has been developed. The problem is formulated, solved and the boundary conditions are applied across the interfaces. The eigenvalue relation is derived and discussed analytically and the results are confirmed numerically. Some reported works are recovered as limiting cases from the present general results. The streaming has a destabilizing effect for all short and long wavelengths. The capillary force is stabilizing for short wavelengths but it is destabilizing for long wavelengths. The axial magnetic fields interior the gas and fluid media are stabilizing. The transverse field is destabilizing for all wavelengths. The radii ratio of the gas and fluid cylinders plays an important role for stabilizing the model and made it more realistic one than the full liquid jet or/and the ordinary hollow jet. The numerical analysis clarify the stable and unstable domains based on different values of the various parameters of the problem.

An Analysis of Effective Throughput in Distributed Wireless Scheduling

Radwan, Amr Korea Multimedia Society 2016 멀티미디어학회논문지 Vol.19 No.2

Several distributed scheduling policies have been proposed with the objective of attaining the maximum throughput region or a guaranteed fraction throughput region. These policies consider only the theoretical throughput and do not account the lost in throughput due to the time complexity of implementing an algorithm in practice. Therefore, we propose a novel concept called effective throughput to characterize the actual throughput by taking into account the time complexity. Effective throughput can be viewed as the actual transmitted data without including the control message overhead. Numerical results demonstrate that in practical scheduling, time complexity significantly affects throughput. The performance of throughput degrades when the time complexity is high.

Predictors for margin of resection >4 mm in the management of periocular basal cell carcinoma

Radwan Almousa 대한안과학회 2021 Korean Journal of Ophthalmology Vol.35 No.5

Purpose: To determine the margin of resection (MOR) for periocular basal cell carcinoma (BCC) and compare the outcomes of BCC treatment, namely Mohs micrographic surgery (MMS) and wide excision with later reconstruction (WELR). Methods: This is a retrospective, comparative, interventional study of patients who underwent surgical treatment of periocular BCC. One hundred forty-two patients were included. One hundred patients were treated with MMS and 42 with WELR. Inclusion criteria were primary periocular BCC with postoperative follow-up of ≥6 months, age more than 18-year-old. Exclusion criteria were, orbital extension, BCC origin outside the periocular area, or those associated with Gorling or nevoid BCC. The main outcome measure was variables associates with MOR >4 mm. Results: There was a positive correlation between the preoperative tumor horizontal and vertical diameter with the corresponding MOR, of 0.27 (p = 0.01) and 0.28 (p = 0.007), respectively. Receiver operating characteristics suggest that a tumor with a horizontal diameter ≥5 mm or a vertical diameter of ≥6 mm, might need MOR >4 mm. One patient in the MMS group had BCC recurrence compared to none in the WELR group, and one patient in the WELR had a positive surgical margin, which was cleared during the reconstruction. Conclusions: BCC tumor margins may extend far beyond clinical margins and the MOR required is often more than 3-4 mm. MMS ensures clear tumor margins but is not practical for all patients. A stratification system could help divide patients between the treatment strategies.