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The enhancement of channel access mechanism assures to provide Quality of Service (QoS) using the service differentiation mechanism over WLAN in IEEE802.11e. The service differentiation scheme is used in the Enhanced Distributed Channel Access (EDCA) MAC layer protocol and this protocol is used the random back-off window algorithm to provide QoS for the real time multimedia applications. However,...
Previous our research has introduced an optimal longcut route problem and a number of solutions to this problem. However, to date, the literature has only presented evaluations based on a single theoretical radio propagation model. Because throughput characteristics derived from radio propagation models significantly affects longcut route performance, this study introduces three simple models by referring...
There are two widely used interference models to characterize interference in wireless communication, protocol model and physical model. The protocol model simplifies the interference by considering only two concerned communication links (or nodes). It ignores the cumulative interference from other links (or nodes). On the other side, the physical model considers the cumulative interference of the...
In recent years, positioning systems for indoor areas using the existing wireless local area network infrastructure have become very popular and attractive. However, most systems only focus on the network deployment for positioning but overlook that the original purpose of these WLAN infrastructures is providing the required connectivity. Furthermore, experimental results related to such positioning...
The capture effect can occur in IEEE 802.11 distributed coordination function (DCF) wireless systems when packets arrive with different powers. Packets with high power can effectively swamp low power packets, such that they are received successfully, when otherwise a collision would have occurred. We present a network performance prediction model that accurately incorporates the capture effect into...
An efficient polling system with M-gated services is considered. The system consists of N stations, the packets of the station have been provided with M-gated services in continuous time. By the embedded Markov chain theory and the probability generating function method, we derived the closed form expressions for the mean queue length, the mean cyclic period characteristics of the system, and the...
In this paper we investigate the impact of a realistic physical layer on the H.264/AVC video transmission over Ad Hoc networks in urban environment. We propose a realistic Multiple Input Multiple Output (MIMO) physical layer which combines a determinist propagation model and a fine-grained model of wireless transmission errors. The determinist propagation model takes into account all the environmental...
QoS control and resource management in 802.11e WLANs to support real time and multimedia services remains an open problem. All the solutions that only aim to enhance the performance of the enhanced distributed channel access (EDCA) mechanism cannot resolve the performance degradation problem once the channel becomes saturated. Hence, an efficient admission control scheme in EDCA is a key to guarantee...
High variability of access resources in heterogeneous wireless networks and limited computing power and battery life of mobile computing devices such as smartphones call for novel approaches to satisfy the quality-of-service requirements of emerging wireless services and applications. Towards this end, we first investigate a Markov-based stochastic scheme for modeling and estimation of bandwidth and...
As IEEE 802.11 networks in a BSS are increasingly used to carry VoIP, concerns about QoS arise. The overall delay of all VoIP flows drastically increases when the number of VoIP sources approaches the capacity, due to the characteristics of CSMA/CA. We propose a novel call admission control with the Queue size Prediction using Computation of Additional Transmission (QP-CAT) to avoid admitting an excessive...
We consider a scenario in which users share an access point and are mainly interested in VoIP applications. Each user is allowed to adapt to varying network conditions by choosing the transmission rate at which VoIP traffic is received. We denote this adaptation process by end-user congestion control, our object of study. The two questions that we ask are: (1) what are the performance consequences...
In this study, the video transmission performances of 802.11 and 802.16 technologies are compared by using simulations. The integration of NS2 and EvalVid defined in literature is the simulation tool used in this work. 802.16 and EvalVid packets are patched in to NS2. A real video file is converted into MP4 format with preprocessing, then its transmission is simulated over NS2-EvalVid tool for both...
Quality of service (QoS) in wireless 802.11 networks cannot be achieved without the support for service differentiation at the medium access layer. IEEE802.11 suffers from QoS limitations that have often been summarized in the literature. We present simulation results to show the effectiveness of several proposed techniques of improving the QoS in the IEEE802.11 protocol. Specifically, we closely...
This paper investigates effects of pilot assisted channel estimation on dynamic resource allocation in a multiuser orthogonal frequency division multiplexing (OFDM) system. The channel estimation is done in each OFDM symbol through least-squared error (LSE) or minimum mean-squared error (MMSE) algorithm. The performance of each of these algorithms is evaluated through computer simulations. The maximal...
More and more users subscribing to wireless broadband services are seeking to have access to both WLAN and UMTS networks. We study individually optimal user-network association in an integrated WLAN and UMTS hybrid cell. The association problem is formulated within a non-cooperative game framework. In the formulation, mobile arrivals are assumed to follow the Poisson process and each mobile considers...
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