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One of the fundamental tasks of the MAC layer in wireless networks is coordinating channel access securely and efficiently. However, the contention-based medium access scheme used in IEEE 802.11 networks has been found to be suboptimal, especially for a large number of users. Moreover, it is vulnerable to misbehavior resulting in an unfair share of the wireless channel. To tackle these two problems,...
Rate adaptation algorithms (RAAs) in 802.11 networks can have a significant impact on network throughput. In order to attempt to maximize throughput, these algorithms dynamically adapt to inferred changes in the channel being used. Evaluating and comparing rate adaptation algorithms is extremely challenging due to the variability of channel conditions. Recent work on developing and evaluating new...
With the exponential growth in mobile data traffic taking place currently and projected into the future, mobile operators need cost effective ways to manage the load of their networks. Traditionally, this has been achieved by offloading mobile traffic onto Wi-Fi networks due to their low cost and ubiquitous deployment. Recently, LTE operating in the unlicensed spectrum has drawn significant interests...
In this paper, the multi-channel performance of large scale deployment of Long Term Evolution (LTE) in Unlicensed (LTE-U) band and WiFi using stochastic geometry is studied. LTE-U and WiFi cell placement is modeled as a Poisson Point Process (PPP), while transmission activity is modeled as hardcore simple sequential inhibition (SSI) point processes, which have been shown to accurately model Carrier...
The first giga-bit class wireless local area network (wireless LAN) below 6 GHz frequency (the IEEE 802.11ac standard) is attracting attention due to its capability of handling much more of the rapidly growing data traffic. The increased density of wireless LAN access points (APs), however, has induced inter-cell interference that severely degrades system performance. This problem seems to be getting...
Device-to-Device (D2D) communications can efficiently support the growth in mobile data traffic by offloading part of the traffic from the cellular infrastructure. D2D communications are influenced by the propagation conditions between mobile devices that depend on the antenna heights, presence of obstacles, and mobility of devices. Analytical and simulation studies have shown that link-aware opportunistic...
Carrier-grade Wireless Local Area Network (WLAN) is becoming an important complementary system to cellular networks for Mobile Network Operators (MNOs). Network controlled access network selection between cellular and WLAN is an essential functionality to optimize network performance and user experience. Automated configuration and optimisation of the network selection mechanism is of utmost importance...
Access Point (AP) selection in WiFi hotspots is driven by stations and it is based on the measured strongest RSSI (Received Signal Strength Indicator) level: any station connects to the AP that provides the higher physical data rate. Although simple and effective in low crowded scenarios with low-medium traffic load, this strategy performs inefficiently when the number of mobile users is high and...
The performance of wireless communication systems in difficult radio conditions needs to be enhanced. More and more systems use indeed advanced antenna techniques to do so. Especially one type of advanced antenna technique, beamforming, is found more and more often and presented as the promising overall answer to increase performance. The theory of beamforming is quite well known since a while, but...
This study presents new channel utilization methods for a multi-channel wireless backbone network (WBN). To flexibly and efficiently use multiple channels, we exploit OpenFlow as a baseline function. In this paper, we propose a new framework to build an OpenFlow-based multi-channel WBN and then implement two new channel utilization methods: (i) a flow direction aware channel assignment method (DCA)...
Very often a denser deployment of APs is required to increase the coverage and capacity in IEEE 802.11 WLAN. It increases the number of APs with overlapping coverage areas. Such overlapping eventually makes more and more clients to fall in the common coverage area of several APs. Interfering APs require different frequency channels for operation in order to avoid the co-channel interference between...
New PHY and MAC layer enhancements have been introduced in different IEEE 802.11 WLAN standards. These improvements have given birth to a wide range of bandwidth channels (up to 160MHz) and very high transmission data rates (> 1Gbps) to keep up with current and up-coming multimedia applications. The major reason for the inefficiency of different WLANs is that the current MAC layer randomly allocates...
Femtocell and WiFi play crucial roles in sustaining the continued growth in mobile traffic. Deploying Femtocells in WiFi hotspots would allow the access providers to provide more capacity for users and improve their quality of experience during mobility. Hence, the co-existence of Femtocell and WiFi carries critical importance for improving the total performance of the users and meeting the promised...
The concept of Participatory Sensing is centered on individuals that collect data using their smart phones (or other dedicated devices) to track the evolution of their work/living places. The main objective is to use the gathered data in order to enhance the offered quality of life. To maximize people involvement in this process we propose a ferry based architecture to leverage the contributors from...
The growing need for multimedia applications within wireless Local Area Networks (LAN) demands reliable and efficient broadcasting and multicasting transmission of throughput sensitive data, like audio and video. IEEE 802.11 standard which is the primary technology in wireless LANs was not initially designed to handle heavy broadcasting traffic. However, this raises a series of reliability problems...
As the wireless networks become more and more popular currently, how to guarantee the Quality of Service (QoS) for high bandwidth traffic is a prime concern. Compared with most existing Medium Access Control (MAC) protocols using only a single wireless channel as the transmission medium, multi-channel MAC protocols have attracted intensive attention recently because of their capabilities of significantly...
A new slotted split-channel medium access control (SSC-MAC) protocol is proposed for multihop wireless networks to maximize concurrent packet transmissions. By adjusting the relationship between the reservation slot (RS) on the control channel (CCH), data packet transmission slot (TS) on the data channel (DCH) and acknowledgment slot (AS) on the acknowledgment channel (ACH), the channel reservation,...
The Wireless Local Area Network (WLAN) has experienced tremendous changes through these days, both in usage and technological aspects. Recently, 802.11ac and 802.11ad protocols for WLAN have been standardized by IEEE. They are both amendments to the 802.11-2012 protocol and their primary Medium Access Control (MAC) technique is Distributed Coordination Function (DCF). What's more, in order to improve...
All over the world, the existing spectrum is already been saturated with ever increasing demand. Every day huge number of users is joined to the existing fixed band frequency but the bandwidth is not increasing. To solve this issue the cognitive radio is the best choice. Spectrum or white space detection is an essential and very important issue in cognitive radio communication. The aim of channel...
In recent years, the growth of Wireless Local Area Networks (WLANs) is enormous. Supporting voice applications over WLANs is of great interest in scientific and technical community. In this paper an analytical model is developed, based on a Markov chain, for the calculation of saturation throughput and average packet delay for IEEE 802.11 WLANs. A hybrid network scenario is studied with voice stations...
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