In this paper a brief introduction to the concept of quality of service has been given. However, it mainly focuses on the classification of routing algorithms based on a number of different criteria like: protocols, structure, technologies in use, etc. And it concludes with a presentation of a common problem facing routing protocols, namely routing loops, and explained the known solutions to that problem. arabic 6 English 52
Ibrahim Almerhag, Ali Ganoun(6-2018)

The introduction of new services with different bandwidth requirements, e.g., data and multimedia, to cellular mobile radio networks makes many of the traditional mechanisms unusable or less efficient. The call admission control and the handover handling are the most sensitive issues to this extension. The performance of all services including the traditional voice and the new services can be dramatically effected if no appropriate schemes are used. In this research work, a new call admission and handover handling schemes for a cellular mobile network that offers two service types: voice and data is proposed. The data connections are assumed to be transmitted at different data rates, which are an integer multiple to that of one traffic channels, which are full speed(Cd1) & reduced peed(Cd2). In order to reduce the handover failure probability of data connections, the data mobile terminals (MT) are assumed to have the capability of transmitting at two different data rates. If the handover request can not be satisfied by the base station of the destination cell due to unavailable free traffic channels, the data mobile terminals tries with a lower data rate. The handover fails if the network is incapable on providing the minimum data rate at which the mobile terminal can transmit. The reduced data connection or data rate can be speeded up to full data rate or full speed as soon as enough bandwidth is available. The effect of different traffic and configuration parameters on the performance of the different models for two cell model with equal input traffic intensity, two cell model with different input traffic intensity, and two cell model with equal input traffic intensity considering the congestion rate for the highway model are studied as the models of this research. These models are built using MOSEL language (Modeling Specification and Evaluation Language). The results of investigating the mentioned models showed the effect of the handover, and speed of data on these different models.
W. ABUGHRES(1-2000)

In this paper, imposing the Hadamard Transform (HDT) on Orthogonal Space-Time Block Codes (OSTBC) schemes using multiple transmit antennas is proposed in order to increase the reliability and improve the error performance of wireless communications. It is referred to as joint Hadamard transform and OSTBC schemes with multiple transmit antennas. However, HDT is used to change the location of constellation points by converting the transmit symbols of OSTBC system, and hence extending the Euclidean distance between transmit symbols for a precise detection. Simulation results demonstrated that increasing the number of transmit antennas in OSTBC systems employing 8-PSK improves the Bit Error Rate (BER) performance as in the case of OSTBC 2×2 scheme where an SNR of about 13.5 dB is required to achieve a BER of 〖10〗^(-6), while only about 7 dB in OSTBC 8×8 scheme is required to obtain the same error probability. It is also demonstrated that imposing the Hadamard criteria on the OSTBC 2×2, 4×4, and 8×8 schemes has showed a performance improvement of about 3 dB, 6 dB and 9 dB, respectively, as compared to the conventional OSTBC systems.
Taissir Y. Elganimi, Marwan B. Elkhoja(4-2019)