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In this paper, we evaluate the saturation throughput for an IEEE 802.11 based wireless network considering capture effect at the receiver, while nodes transmit with random powers. In this respect, we consider a scenario consisting of a specific number of wireless nodes. Then, we derive the transmission as well as collision probabilities with respect to the perfect capture effect. In order to maximize...
Recent experimental results have shown that the minimum signal-to-interference ratio required at a receiver (CPth) depends on the order of arrival of the overlapping frames. For a given sender-receiver distance, this differential capture capability of a receiver leads to two distinct interference ranges (ri) around the receiver, and its value is much smaller when the sender's frame arrives earlier...
The performance unfairness problem in a single cell IEEE 802.11 wireless local area network (WLAN) is considered. While existing research is based on the assumption that all nodes have the same transmission success probability and per-node throughput, this fairness exists only if all nodes within range of the access point can sense each other. Recent measurements suggest that this is not necessarily...
Current devices use a network selection policy that is mostly driven by the physical layer, choosing the point of attachment with the highest Received Signal Strength Indicator (RSSI). Unfortunately for 802.11 networks, RSSI is not a good indicator of actual network performance as it is normally the bandwidth to the Internet and not the wireless signal conditions which dictates the quality of service...
Experiments show that IEEE 802.11 DCF system exhibits unstable behavior in the congestion onset load range where the system starts to become saturated. This phenomenon is not well investigated due to the lack of proper models. In this paper, we propose a two-dimensional (2-D) Markov chain model by combining the well-known saturated model with newly created idle states. Closed-form solution to the...
This paper considers the medium access problem in the IEEE 802.11 standard. Although the transmission bit rates have clearly increased, some MAC related problems remain yet unsolved. The random channel contention suffers from short term unfairness and from the considerable reduction of the effective throughput due to the collision probability that increases with the number of contending nodes in the...
This paper presents an enhanced channel access mechanism for the newly introduced Mesh Deterministic Access (MDA) mechanism for IEEE 802.11s based Wireless Mesh Networks (WMNs). The MDA is an optional scheduled access mechanism which enables mesh nodes to negotiate periodic transmission opportunity (referred to as Mesh Deterministic Access Opportunity (MDAOP)) for a collision free transmission of...
Wireless frequency resources are often the limiting factor for WLAN throughput. Hence, wireless channel management is needed to mitigate co-channel interference and improve channel reuse efficiency in WLANs, particularly in those with high-density access point deployment. The key challenge is to accurately predict interference and its effect on network performance. This paper presents a new interference...
The 802.11 standard includes several modulation rates, each of which is optimal for a different channel condition. However, there are no simple and reliable methods for nodes to determine their current channel conditions. Existing link adaptation techniques use packet losses as an indication of poor channel conditions; however, when there is a significant probability of collision, this assumption...
IEEE 802.11-based mesh networks can yield a throughput distribution among nodes that is spatially biased, with traffic originating from nodes that directly communicate with the gateway obtaining higher throughput than all other upstream traffic. In particular, if single-hop nodes fully utilize the gateway's resources, all other nodes communicating with the same gateway will attain very little (if...
Wireless multihop communication is becoming more important due to the increasing popularity of wireless sensor networks, wireless mesh networks, and mobile social networks. They are distinguished from conventional multihop networks in terms of scale, traffic intensity and/or node density. Being readily-available in most of 802.11 radios, multirate facility appears to be useful to address some of these...
Future networks are aiming to hold more interactive services resulting in higher traffic volume, however Voice over Internet Protocol's (VoIP) high network resource allocation is still a handicap. Recent studies on network coding have proved greater throughput performance by combining packets before broadcasting them. This paper presents a design and implementation of a new methodology for VoIP services...
Cooperative communication techniques have earlier been applied to design of the IEEE 802.11 medium access control (MAC) and shown to perform better. High rate stations can help relay packets from low-rate stations resulting in better throughput for the entire network. However, this also involves additional energy costs on the part of the relay which can result in reducing the network lifetime. We...
In this paper we propose a game-theoretic approach for characterizing WiFi network performance in presence of intelligent nodes employing cognitive functionalities. We assume that a cognitive WiFi node is aware of its application requirements and is able to dynamically estimate the network status, in order to dynamically change its access strategy by tuning the contention window settings. We prove...
In this paper, we present a collision-free asynchronous multi-channel access protocol for Ad Hoc wireless networks using a single transceiver. Our protocol, dubbed AMMAC for Asynchronous Multi-channel Medium Access Control, targets low-cost and low-power deployments where nodes are equipped with a single transceiver. Other distinguishing features of AM-MAC include its simplicity and the fact that...
There have been a number of TCP variants proposed in the literature to combat random packet losses in wireless networks. In this paper we first perform a simulation study on the performance of these TCP variants in the context of IEEE 802.11 WLAN with various channel conditions, generated using different wireless error models and show that none of the existing TCP variants has superior performance...
This paper proposes a mathematical framework for evaluating the throughput of an 802.11 Distributed Wireless Network (DWN) when the system allows Multi-Packet Reception (MPR) in asynchronous operating mode. Differently from previous studies on MPR, which assume a certain synchronization between the different sources at the beginning of the respective transmissions, this work analyzes a fully distributed...
The success of dynamic spectrum access through simple listen-before-talk etiquettes has paved the way for opening up the spectrum. However, many problems still remain in these networks. Due to the complex nature of IEEE 802.11 networks, for instance, optimizing these networks regarding power, rate and carrier sense threshold remains a very tough challenge. In this paper, we introduce spatial learning...
Wireless multi-hop networks often rely on the use of IEEE 802.11 technology. Despite of the robustness of the IEEE 802.11 Distributed Coordination Function (DCF) for working in various network scenarios, it has been proven that critical inefficiencies can arise in the case of multi-hop packet forwarding. In this paper, we propose a MAC scheme, based on the visualization of the Point Coordination Function,...
Modeling computer networks is a complex task, as their behavior depends from several variables. Focusing on a single communication device, ISO/OSI and TCP/IP layered protocol stacks provide interoperability and fast deployment of networking solutions, but they limit the control on the interaction among protocols operating at different layers. As a consequence, the need is emerging to develop appropriate...
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