Finite Load Conditions Research Articles

Analytical Analysis of Applying Packet Fragmentation Mechanism on Both Basic and RTS/CTS Access Methods of the IEEE 802.11b DCF Network Under Imperfect Channel and Finite Load Conditions

The mathematical modeling and performance evaluation of the IEEE 802.11 network in all its various extensions (802.11b, 802.11a, 802.11g, 802.11e, 802.11n, etc.) have already been widely explored over the past years. However, the Packet Fragmentation Mechanism (PFM), which is proposed by the IEEE work group to enhance the MAC sub-layer of the IEEE 802.11 standard in an error-prone channel, has been missed in the available literature. Yet, the PFM is the only existing solution to reduce the influence of bit error rate and the length of data packets on the packet error rate, and consequently on the performances of IEEE 802.11 networks. In this paper, we propose a new three-dimensional Markov chain in order to model, for the first time in the literature, the PFM in both Basic and RTS/CTS access methods of the IEEE 802.11b DCF network under imperfect channel and finite load conditions. Then, we develop mathematical models to derive a variety of performance metrics, such as: the overall throughput, the average packet delay successfully transmitted, the average packet drop time, the delay jitter and the packet delay distribution. Performance analysis of applying PFM on both Basic and RTS/CTS access methods of the IEEE 802.11b DCF network under imperfect channel and finite load conditions shows original results and leads to new conclusions that could not be intuitively expected.

Kramers-like turnover in load-dependent activated dynamics

Recent advancement of experimental techniques at the single molecule level has demonstrated how an external load affects a chemical reaction which controls the transport of biological motor proteins. Majority of these studies are concerned with thermodynamically open systems. We have examined a prototype model reaction in terms of inertial Brownian motion of a particle in a force field subjected to an overdamped motion of a viscous load coupled harmonically to the particle. A general analytical expression for the rate constant has been derived to demonstrate that depending on the strength of harmonic coupling and drag coefficient of the load a Kramers-like turnover can be realized in the spatial diffusion-limited regime. The turnover reduces to a crossover between the two states characterized by zero-load and finite load conditions.

Performance evaluation of IEEE 802.11-based wireless LANs under finite-load conditions

Since its release in 1999, IEEE 802.11 became the defacto standard for Wireless Local Area Networks (WLANs). Despite its widespread deployment, analytical modeling efforts of the IEEE 802.11 standard have been focusing on the performance under saturated load conditions. This paper aims at analytically modeling and analyzing the performance of the IEEE 802.11-based networks. The model proposed in this paper follows exactly the real implementation of the DCF method. Extensive NS2 simulations are conducted to verify the results of the analytical model. Our model gives a new interpretation for the saturation behavior reported in the literature, relates the critical point (inflection point) to the various system and traffic parameters and analytically explains why the RTS/CTS mechanism is favorable for certain offered loads.

Performance analysis of IEEE 802.11 ad hoc networks in the presence of exposed terminals

The paper evaluates the performance effects of exposed terminals in IEEE 802.11 ad hoc networks in finite load conditions. It derives analytical models for the estimation of channel utilization and media access delay for IEEE 802.11 ad hoc networks in finite load conditions with and without exposed terminals. The simulation results show that the analytical estimated channel utilization and media access delay metrics are fairly accurate.

Performance analysis of IEEE 802.11 ad hoc networks in the presence of hidden terminals

The paper discusses analytical models for the estimation of channel utilization and media access delay for IEEE 802.11 ad hoc networks in finite load conditions in the presence of hidden terminals. The simulation results show that the analytical estimated channel utilization and media access delay metrics are fairly calculated.

Delay Performance Analysis and Evaluation of IEEE 802.11e EDCA in Finite Load Conditions

The paper presents an analytical model for the performance evaluation of IEEE 802.11e EDCA scheme under finite load conditions on the basis of various instances of delay metric (i.e., media access delay, queuing delay and total delay). The simulation results show that the analytical estimated instances of the delay metric are almost accurate. The paper exhibits that concerning the delay of serving classes, EDCA compared to the conventional DCF, favors high priority classes against low priority ones, while almost does not affect the behavior of medium ones.