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— We analyze the performance of the IEEE 802.11b wireless local area networks. We have observed that when some mobile hosts use a lower bit rate than the others, the performance of all hosts is considerably degraded. Such a situation is a common case in wireless local area networks in which a host far away from an Access Point is subject to important signal(More)
We consider wireless LANs such as IEEE 802.11 operating in the unlicensed radio spectrum. While their nominal bit rates have increased considerably, the MAC layer remains practically unchanged despite much research effort spent on improving its performance. We observe that most proposals for tuning the access method focus on a single aspect and disregard(More)
— We analyze in this paper the fairness of the 802.11 DCF (Distributed Coordination Function) access method. Short-term fairness is an important property of a MAC layer for obtaining short delays. We show that contrary to the common wisdom, a 802.11 cell with two hosts does not exhibit short-term unfairness. Many papers considered 802.11 as short-term(More)
Previously, we have analyzed the short-term fairness of the 802.11 DCF (Distributed Coordination Function) access method in the case of a network with two hosts. In this paper we extend the analysis to an increased number of hosts. We use two fairness indices. The first one is the number of inter-transmissions that other hosts may perform between two(More)
—In this paper, we review the most important performance characteristics of the 802.11 DCF wireless networks, point out some false common knowledge, and report on recent improvements. [1] uses the Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) access method: a station trying to transmit first checks if the channel is free, waits for the DIFS(More)
We consider the problem of running RPL on top of the IEEE 802.15.4 MAC layer-the two layers operate over two different structures, a directed acyclic graph in the case of RPL and a cluster-tree for IEEE 802.15.4. We propose to adapt the cluster-tree of IEEE 802.15.4 so that it can efficiently work coupled with RPL. Nodes in our modified cluster-tree can(More)
— In this paper, we introduce and evaluate novel adaptive schemes for neighbor discovery in Bluetooth-enabled ad-hoc networks. In an ad-hoc peer-to-peer setting, neighbor search is a continuous, hence battery draining process. In order to save energy when the device is unlikely to encounter a neighbor, we adaptively choose parameter settings depending on a(More)
An overwhelming part of research work on wireless networks validates new concepts or protocols with simulation or analytical modeling. Unlike this approach, we present our experience with implementing the <i>Idle Sense</i> access method on programmable off-the-shelf hardware---the Intel IPW2915/abg chipset. We also present measurements and performance(More)
In atypical deployment of IEEE 802.11 wireless LANs in the infrastructure mode, an access point acts as abridge between the wireless and the wired parts of the network. Under the current IEEE 802.11 Distributed Coordination Function (DCF) access method, which provides equal channel access probability to all devices in a cell, the access point cannot relay(More)