in wireless networks, mobility is an important issue because Internet connectivity can only be effective if it is available during the movement of a node. To enhance mobility, the IEEE802.16e standard has set procedures to design wireless access systems to operate on the move without any disruption of services. The major difference between mobile WiMAX and fixed WiMAX is mobility support. However, speed and trajectory of nodes are unpredictable and can vary even in identical circumstances. In this paper mobile node trajectory is studied under different codecs schemes in order to evaluate the effect of node movement, towards or away from the base-station, on end to end delay, jitter, mean opinion score and throughput of a VoIP application. The results showed that trajectory inward improves network performance since mobile node gets closer to the base-station and hence signal is improved and less power is required. arabic 12 English 67
I. Almerhag, N. Aboalgasem(5-2017)

A denial of service attacks are usually employed to interrupt the system's activity by getting a large number of fake requests, which leads to slowing down and stopping information system or network operations. This paper outlines the basic principles of DDoS attacks, explains how DDoS attack works. The paper presents an experimental using OPNET simulation tool in which traffic from three different applications VoIP, FTP, and HTTP is used to make the practical model with a firewall shield to model and simulate DDoS over Internet. However, three scenarios have been developed to illustrate different aspects of the DDoS over networks. The results clearly demonstrate how firewalls can be configured to mitigate DDoS attacks
Azeddien M. Sllame, Reema A. Saed, Mariam Abojella Msaad(5-2021)

LTE’s study phase began in late 2004. The overall goal was to select technology that would keep 3GPP’s Universal Mobile Telecommunications System (UMTS) at the forefront of mobile wireless well into the next decade. Key project objectives were set in the following areas: peak data throughput; spectral efficiency; flexible channel bandwidths; latency; device complexity; and overall system cost. The main decision was whether to pursue the objectives by continuing to evolve the existing W-CDMA air interface (which incorporates HSPA (highspeed packet access) or adopt a new air interface based on OFDM. arabic 5 English 27
Mariam Abojela Msaad, Amer R. Zerek, Fareda A. Elmaryami(1-2014)