The impact of propagation environment and traffic load on the performance of routing protocols in ad hoc networks

Wireless networks are characterized by a dynamic topology triggered by the nodes mobility. Thus, the wireless multi-hops connection and the channel do not have a determinist behaviour such as: interference or multiple paths. Moreover, the nodes' invisibility makes the wireless channel difficult to detect. This wireless networks' behaviour should be scrutinized. In our study, we mainly focus on radio propagation models by observing the evolution of the routing layer's performances in terms of the characteristics of the physical layer. For this purpose, we first examine and then display the simulation findings of the impact of different radio propagation models on the performance of ad hoc networks. To fully understand how these various radio models influence the networks performance, we have compared the performances of several routing protocols (DSR, AODV, and DSDV) for each propagation model. To complete our study, a comparison of energy performance based routing protocols and propagation models are presented. In order to reach credible results, we focused on the notion of nodes' speed and the number of connections by using the well known network simulator NS-2.Comment: 13 pages, 5 figures, International Journal of Distributed and Parallel Systems (IJDPS) Vol.3, No.1, January 201

Static Characterization of the Birefringence Effect in the Semiconductor Optical Amplifier Using the Finite Difference Method

Knowing the various physical mechanisms of the semiconductor optical amplifier (SOA) helps us to develop a more complete numerical model. It also enables us to simulate more realistically the static behavior of the SOAs’ birefringence effect. This way, it allows us to study more precisely the behavior of SOAs, and particularly the impact of the amplified spontaneous emission (ASE) or the pump and probe signals as well as the optical functions based on the non-linearity of the component. In static regime, the SOAs possess a very low amplification threshold and a saturation power of the gain which mainly depends on the optical power injected into the active region. Beyond the optical input power, the SOA is in the saturated gain regime which gives it a nonlinear transmission behavior. Our detailed numerical model offers a set of equations and an algorithm that predict their behavior. The equations form a theoretical base from which we have coded our model in several files.cpp that the Language C++ executes. It has enabled us, from the physical and geometrical parameters of the component, to recover all the relevant values ​​for a comprehensive study of SOAs in static and dynamic regimes. In this paper, we propose to make a static characterization of the effect of the nonlinear polarization rotation by realizing a pump-probe assemblage to control the power and state of polarization at the entering of the SOA

Dynamic Response of Two-Electrode Distributed Feedback Laser for Stable Signal Mode Operation

The longitudinal spatial hole burning (LSHB) effect has been known to limit the performance of distributed feedback (DFB) semiconductor lasers to achieve a better dynamic signal mode operation (DSMO). So, in order to ensure a stable (DSMO), we propose a novel device design of two electrode DFB lasers with longitudinal variation in the coupling coefficient (distributed coupling coefficient (DCC)), the structure also contains a phase shifted in middle of the cavity. By means of the finite difference time domain (FDTD) numerical method, we analyze dynamic response of our structure and we also compare the results with the conventional two electrode DFB laser (TE-DFB). The numerical simulation shows that, a better dynamic signal mode has been achieved by TE-DCC-DFB lasers in comparison with TE-DFB laser due to its better and high side mode suppression ratio (SMSR). Therefore, the TE-DCC-DFB lasers will be useful to extend the transmission distance in optical fiber communication systems