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In case of high dynamic topology, reactive routing protocols provide quick convergence by faster route discoveries and route maintenance. Frequent broadcasts reduce routing efficiency in terms of broadcast cost; B k , and expected time cost; E[t]. These costs are optimized using different mechanisms. So, we select three reactive routing protocols; Ad-hoc Ondemand Distance Vector (AODV), Dynamic Source Routing (DSR), and DYnamic Manet On-demad (DYMO). We model Expanding Ring Search (ERS); an optimization mechanism in the selected protocols to reduce B k and E[t]. A novel contribution of this work is enhancement of default ERS in the protocols to optimize B k and E[t]. Using NS-2, we evaluate and compare default-ERS used by these protocols; AODV-ERS1, DSR-ERS1 and DYMO-ERS1 with enhanced-ERS; AODV-ERS2, DSR-ERS2 and DYMO-ERS2. From modeling and analytical comparison, we deduce that by adjusting Time-ToLive (T T L) value of a network, efficient optimizations of B k and E[t] can be achieved.

This paper presents how enhanced Quality of Service (QoS) in IEEE802.11e is achieved by providing traffics with different priorities performing the access to the wireless medium. Particularly, the EDCF set of parameters defines the priorities of the admission control mechanism during the Contention-based Period (CP). This can subsequently be declined to a variation of network dynamicity. Reliability analysis of different traffic classes (video, voice and data), without considering both network topology and node's mobility constraints, is not well appropriate. Being based upon scenarios, our proposed approach reveals how the behaviour of the service differentiation scheme is greatly affected according to the nodes' mobility (position and velocity). Thus, three levels (Low, Medium, and High) of node's speed are discerned. Depending on the Access Aategories (AC's) in QoS Stations (QSAT's), the Wireless LAN has been implemented on various static and dynamic scenarios using NS-2. Performance of EDCF based on the main MAC-layer metrics, such as throughput, End-2-End delay and jitter, is deeply investigated.

Abstract-In this paper, we carry-out a study of the Quality of Service (QoS) mechanism in IEEE802.11e Enhanced Distribution Coordination Function (EDCF) and how it is achieved by providing traffics with different priorities. It can perform the access to the radio channel or just simply it can considerably be declined subsequently to a variation of network dynamicity. The results of the proposed analysis show that the EDCF scheduler looses the ability of the traffic differentiation and becomes insensitive to the QoS priority requirements. Consequently, it goes away from the region of stability and EDCF doesn't offer better performance than the conventional DCF scheme. Therefore, traffic specifications are weakly applied only for the channel occupation time distribution. During the handoff between the Base Stations (BS's), the response time of the data rate application within the roaming process grows to the initial throughput level. Performance metrics at the MAC layer, like throughput, End-2-End delay, and packet loss have been evaluated.

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