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Network convergence paradigm will substantially increase the pervasive use of WiFi-enabled smart mobile devices. Although various on-demand streaming services are already available over mobile WiFi-enabled devices, it remains a challenging problem due to WiFi's limited communication range, mobility and user population density issues. In this paper, we enhance our previous work on MOVi (Mobile Opportunistic...
We address the issue of misbehavior detection and reaction in IEEE 802.11 based Ad Hoc networks. Selfish misbehavior involves disobeying standard protocol mechanisms to gain unfair access to the channel at the expense of other users. We outline conditions on genuine (non-misbehaving) node's throughput to guarantee the presence of misbehavior, and propose non-adaptive and strong reaction mechanism...
BitTorrent has achieved a great success in the field of peer-to-peer (P2P) file sharing. Although BitTorrent allows peers to share files efficiently and scalably, it shows inefficiency when a client participates in multiple torrents where each of them concurrently competing for the limited link bandwidth. In this paper, we propose a new bandwidth allocation algorithm, which greedily increases the...
We present a lightweight algorithm for the estimation of the node achievable throughput and available bandwidth in IEEE 802.11 wireless networks. We consider a multirate WLAN with access point (AP), where there may be both elastic and inelastic traffic flows. Through our algorithm and leveraging previous theoretical results, the AP can estimate: (i) the available bandwidth that a new station wishing...
We propose cMAC, a centralized, polling-based protocol for wireless LANs. With cMAC, the access point (AP) sets nodes into the polling mode if they have backlogged data and polls them during the polling period. The AP also periodically opens the contention period to allow nodes with newly arrived data to send data and at the same time announce their queue states. The main feature of cMAC is that it...
This paper presents a novel Medium Access Control (MAC) protocol for 802.11 networks in which the nodes can adopt smart antenna systems. The presented protocol is designed to satisfy two fundamental requirements: the exploitation of adaptive arrays to increase the network throughput and the backward compatibility of the novel scheme with the 802.11 MAC layer. The developed solution allows the simultaneous...
In an IEEE 802.11 based mobile ad hoc network (MANET), a network node accesses a common wireless channel through the distributed coordinate function (DCF), which is provided at the medium access control (MAC) layer of the IEEE 802.11 standard. The binary exponential backoff (BEB) algorithm, which uses slotted contention windows, plays an important role in the DCF. This paper develops a mathematical...
IEEE 802.11 wireless transmissions suffer from a big security flaw as they are vulnerable to Denial of Service Attacks (DoS) which can degrade enormously their performance, especially their achieved throughput. One of the most harmful forms of these attacks is the jamming. In this paper, we provide an analytical model to study the effect of jamming on WLANs. Hence, we implement a physical layer jamming...
Utilizing multi-interfaces and multi-channels (MIMC) is essential in increasing capacity and performance of emerging wireless mesh networks. However, the current IEEE 802.11s draft which is a standardization activity of the WLAN based mesh network does not sufficiently consider these capabilities. This may lead to poor performance of the network in terms of throughput and scalability. In this paper,...
In WiFi networks, mobile nodes compete for accessing a shared channel by means of a random access protocol called Distributed Coordination Function (DCF). Although this protocol is in principle fair, since all the stations have the same probability to transmit on the channel, it has been shown that unfair behaviors may emerge in actual networking scenarios because of non-standard configurations of...
Wi-Fi enabled hand-held devices quickly occupied the consumer market as a result of the remarkable customer acceptance of IEEE 802.11 standard. But the widely used contention based medium access mechanism is unable to meet the increasing traffic demand of today's home users. Especially, delay sensitive multimedia contents suffer heavily from quality degradation under high traffic load. However, the...
Traditional contention-based random-access wireless MAC protocols such as IEEE 802.11 DCF are designed for single-hop wireless networks and do not perform well in multi-hop scenarios due to inefficiency in their medium reservation mechanisms. In this paper, we introduce a new MAC protocol, called EMAC, which improves the efficiency of wireless medium reservation for general asynchronous multi-hop...
This article presents a new MAC layer protocol for IEEE 802.11 EDCA-based ad-hoc networks with hidden nodes. The key idea of the proposed solution is based on an intelligent two-step reservation procedure which is combined with the advantages of EDCA service differentiation. The new protocol achieves significant performance improvement for high priority traffic (e.g., Voice) in terms of fairness,...
Due to the packet-fairness property of the 802.11 WLANs, the clients with low rates take longer time to transmit a packet and would reduce the overall network throughput, as well as the per-node throughput of those high data rate clients. We propose a collaborative relay method, which allows high data rate clients to relay traffic for the low data rate clients to improve the network throughput. There...
It is essential for emergency services to have reliable, adaptable, scalable and high throughput communication network. As one can not trust on the existing infrastructure, mobile ad hoc networks (MANET) can be a good alternative to provide rescue operations. Since partitioning problem of MANETs due to node mobility degrades the aggregate throughput and is unreliable due to idle periods when rerouting...
We propose a novel power saving strategy called Sleep during Neighbor-Addressed Frame (SNAF) for improving energy efficiency of IEEE 802.11 based wireless networks. IEEE 802.11 (Wi-Fi) radios that employ SNAF mode can turn OFF their wireless transceivers (i.e., put radios in sleep mode) within specific periods of neighbor-addressed frames while they are being received. The sleep duration of transceivers...
The use of multihop wireless networks based on the 802.11 technology has been growing. The primary advantages of this approach are mature technology and ease of deployment. However, the fairness property provided by the 802.11 DCF (distributed coordination function) in a single hop environment has been shown to be non-existent in a multihop environment. For example, in the multihop wireless backhaul...
In this paper, we address the problem of quantifying the impact of backoff misbehaving nodes in IEEE 802.11 networks. We propose two performance metrics, throughput gain ratio and throughput degradation ratio to quantify the performance gain of misbehaving nodes over legitimate nodes and the performance loss of legitimate nodes due to backoff misbehavior, respectively. We use asymptotic analysis to...
In this paper we propose a mixed bias approach which makes use of cross layer optimization. The cross-layer parameters are based on conditions in the network from multiple layers and are used to determine resource and time allocation for nodes in the network. Unlike existing proposals, we propose to bias against several parameters such as link quality and queue size in addition to node distance. We...
Distributed Coordinate Functions (DCF) is the mandatory medium access method for IEEE 802.11 Wireless Local Area Networks (WLANs), which is designed for infrastructure WLANs where all end users connect with Access Point (AP) with single-hop links. DCF doubles its Contention Window (CW) before each retransmission. However, in multi-hops WLANs, a node may encounter different kinds of transmission failures...
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