Iraqi Journal of Information and communication technology

Software- Defined Networking (SDN) is a network architecture approach enables the network to be intelligently and centrally controlled, or programmed, using software applications to helps operators manage the entire network consistently and holistically. Although SDN on the surface provides a simple framework for network programmability and monitoring, few have been said about security measures to make it resilient to hitherto security flaws in the traditional networks and the new threats the architecture is ushering in. One of the security weaknesses the architecture is ushering in due to separation of control and data plane is distributed Denial of Service (DDoS) attack. The main goal of this attack is to make network resources unavailable to legitimate users or introduce large delays. In this paper, the effect of a DDoS attack on SDN is presented, and automatic detection and mitigation of the attacks, using an SDN application written in python with the help of the Open Flow protocol

There have been active researches worldwide for evolving the next-generation networks such as 5G.The 5G network is predicted to ensure considerable mobile data traffic having large number of wireless connections .This is combined with high energy-efficiency and Quality of Service (QoS). For these reasons, 5G should be exploited the prospect of new developments, including multiple-input multiple-output (MIMO) technology and using higher frequencies such as the millimeter-wave (mm Wave) frequency band. Error correction techniques are commonly utilized to reduce transmission error and enhance QoS. In the present paper, polar codes with successive cancellation list (SCL) decoding is used in conjunction with mm Wave and MIMO system in order to gain the advantages ofthese techniques together. The mentioned combined techniques are simulated to show their performances over different wireless channel models mainly: an Additive White Gaussian Noise (AWGN) channel, flat fading channel, and mm Wave indoor fading channel models. The results of the simulation tests showed that combination of polar code with MIMO system improves the Bit Error Rate (BER) performance by at least 6 dB at high SNR compared to the case where no polar code being used

Adaptive Reduced Path Successive Cancellation List (ARP-SCL) decoding for polar codes is proposed in this paper. The aim here is to reduce the complexity of the conventional Successive Cancellation List (SCL)and a previously proposed Reduced Path SCL (RP-SCL) decoders. The complexity reduction is obtained at low and moderate signal to noise power ratio (SNR) regions. The operation of the proposed ARP-SCL decoder relied on the calculation of different optimum pruning parameters according to the operating SNR, while RP-SCL used single parameters set. Simulation tests are carried out to determine both the complexity and Bit Error Rate (BER)performances of the proposed ARP-SCL decoder in comparison with SCL and RP-SCL decoders. Additive White Gaussian Noise (AWGN) channel and two fading channel models simulating indoor 5G environment using millimetre Wave (mm Wave) with a carrier frequency of 28GHz and having either 50 or 400 MHz bandwidths are used. The results revealed that the proposed ARP-SCL decoder reduced the average processed paths up to 46.88%. The largest complexity reductions are obtained in the case of fading channel having 400 MHz bandwidth at high SNR regions. In most test conditions, the mentioned reduction in complexity is achieved without greatly sacrificing the required BER.

This paper introduces an iterative approach for the design of an optimum switching gain controller for a linear time-invariant single-input/single-output (SISO) system. The controller parameters are determined at different switching instants to improve the dynamic characteristics of a closed-loop system and satisfy a set of inequalities. The selected approach is based on solving a constrained parameter optimization problem. Optimization is carried out based on the genetic algorithm (GA) to find the optimum number of switching, optimum switching instants and optimum controller parameters vector. All that in the sense of minimizing a certain time-based objective function and satisfying a set of parametric and operating constraints. Constraints imposed on the controlled system may bein the form of design specifications and/or performance requirements. The technique is applicable for any controller structure and gives a set of optimum parameter values switched at optimum switching instants. Parameter values are a function of the system states at these instants. Different systems are examined to show the applicability of the presented approach