207 research outputs found
MAC Protocols for Wireless Mesh Networks with Multi-beam Antennas: A Survey
Multi-beam antenna technologies have provided lots of promising solutions to
many current challenges faced in wireless mesh networks. The antenna can
establish several beamformings simultaneously and initiate concurrent
transmissions or receptions using multiple beams, thereby increasing the
overall throughput of the network transmission. Multi-beam antenna has the
ability to increase the spatial reuse, extend the transmission range, improve
the transmission reliability, as well as save the power consumption.
Traditional Medium Access Control (MAC) protocols for wireless network largely
relied on the IEEE 802.11 Distributed Coordination Function(DCF) mechanism,
however, IEEE 802.11 DCF cannot take the advantages of these unique
capabilities provided by multi-beam antennas. This paper surveys the MAC
protocols for wireless mesh networks with multi-beam antennas. The paper first
discusses some basic information in designing multi-beam antenna system and MAC
protocols, and then presents the main challenges for the MAC protocols in
wireless mesh networks compared with the traditional MAC protocols. A
qualitative comparison of the existing MAC protocols is provided to highlight
their novel features, which provides a reference for designing the new MAC
protocols. To provide some insights on future research, several open issues of
MAC protocols are discussed for wireless mesh networks using multi-beam
antennas.Comment: 22 pages, 6 figures, Future of Information and Communication
Conference (FICC) 2019, https://doi.org/10.1007/978-3-030-12388-8_
Low-latency Networking: Where Latency Lurks and How to Tame It
While the current generation of mobile and fixed communication networks has
been standardized for mobile broadband services, the next generation is driven
by the vision of the Internet of Things and mission critical communication
services requiring latency in the order of milliseconds or sub-milliseconds.
However, these new stringent requirements have a large technical impact on the
design of all layers of the communication protocol stack. The cross layer
interactions are complex due to the multiple design principles and technologies
that contribute to the layers' design and fundamental performance limitations.
We will be able to develop low-latency networks only if we address the problem
of these complex interactions from the new point of view of sub-milliseconds
latency. In this article, we propose a holistic analysis and classification of
the main design principles and enabling technologies that will make it possible
to deploy low-latency wireless communication networks. We argue that these
design principles and enabling technologies must be carefully orchestrated to
meet the stringent requirements and to manage the inherent trade-offs between
low latency and traditional performance metrics. We also review currently
ongoing standardization activities in prominent standards associations, and
discuss open problems for future research
Wireless industrial monitoring and control networks: the journey so far and the road ahead
While traditional wired communication technologies have played a crucial role in industrial monitoring and control networks over the past few decades, they are increasingly proving to be inadequate to meet the highly dynamic and stringent demands of today’s industrial applications, primarily due to the very rigid nature of wired infrastructures. Wireless technology, however, through its increased pervasiveness, has the potential to revolutionize the industry, not only by mitigating the problems faced by wired solutions, but also by introducing a completely new class of applications. While present day wireless technologies made some preliminary inroads in the monitoring domain, they still have severe limitations especially when real-time, reliable distributed control operations are concerned. This article provides the reader with an overview of existing wireless technologies commonly used in the monitoring and control industry. It highlights the pros and cons of each technology and assesses the degree to which each technology is able to meet the stringent demands of industrial monitoring and control networks. Additionally, it summarizes mechanisms proposed by academia, especially serving critical applications by addressing the real-time and reliability requirements of industrial process automation. The article also describes certain key research problems from the physical layer communication for sensor networks and the wireless networking perspective that have yet to be addressed to allow the successful use of wireless technologies in industrial monitoring and control networks
Improving the Performance of Medium Access Control Protocols for Mobile Adhoc Network with Smart Antennas
Requirements for high quality links and great demand for high throughput in Wireless
LAN especially Mobile Ad-hoc Network has motivated new enhancements and work in
Wireless communications such as Smart Antenna Systems. Smart (adaptive) Antennas
enable spatial reuse, increase throughput and they increase the communication range
because of the increase directivity of the antenna array. These enhancements quantified
for the physical layer may not be efficiently utilized, unless the Media Access Control
(MAC) layer is designed accordingly.
This thesis implements the behaviours of two MAC protocols, ANMAC and MMAC
protocols in OPNET simulator. This method is known as the Physical-MAC layer
simulation model. The entire physical layer is written in MATLAB, and MATLAB is
integrated into OPNET to perform the necessary stochastic physical layer simulations.
The aim is to investigate the performance improvement in throughput and delay of the
selected MAC Protocols when using Smart Antennas in a mobile environment. Analytical
methods were used to analyze the average throughput and delay performance of the
selected MAC Protocols with Adaptive Antenna Arrays in MANET when using spatial
diversity. Comparison study has been done between the MAC protocols when using
Switched beam antenna and when using the proposed scheme.
It has been concluded that the throughput and delay performance of the selected protocols
have been improved by the use of Adaptive Antenna Arrays. The throughput and delay
performance of ANMAC-SW and ANMAC-AA protocols was evaluated in details
against regular Omni 802.11 stations. Our results promise significantly enhancement over
Omni 802.11, with a throughput of 25% for ANMAC-SW and 90% for ANMC-AA.
ANMAC-AA outperforms ANMAC-SW protocol by 60%. Simulation experiments
indicate that by using the proposed scheme with 4 Adaptive Antenna Array per a node,
the average throughput in the network can be improved up to 2 to 2.5 times over that
obtained by using Switched beam Antennas. The proposed scheme improves the
performances of both ANMAC and MMAC protocols but ANMAC outperforms MMAC
by 30%
Physical and Link Layer Implications in Vehicle Ad Hoc Networks
Vehicle Ad hoc Networks (V ANET) have been proposed to provide safety on the
road and deliver road traffic information and route guidance to drivers along with
commercial applications. However the challenges facing V ANET are numerous. Nodes
move at high speeds, road side units and basestations are scarce, the topology is
constrained by the road geometry and changes rapidly, and the number of nodes peaks
suddenly in traffic jams. In this thesis we investigate the physical and link layers of
V ANET and propose methods to achieve high data rates and high throughput.
For the physical layer, we examine the use of Vertical BLAST (VB LAST) systems
as they provide higher capacities than single antenna systems in rich fading
environments. To study the applicability of VB LAST to VANET, a channel model was
developed and verified using measurement data available in the literature. For no to
medium line of sight, VBLAST systems provide high data rates. However the
performance drops as the line of sight strength increases due to the correlation between
the antennas. Moreover, the performance of VBLAST with training based channel
estimation drops as the speed increases since the channel response changes rapidly. To
update the channel state information matrix at the receiver, a channel tracking algorithm
for flat fading channels was developed. The algorithm updates the channel matrix thus
reducing the mean square error of the estimation and improving the bit error rate (BER).
The analysis of VBLAST-OFDM systems showed they experience an error floor due to
inter-carrier interference (lCI) which increases with speed, number of antennas
transmitting and number of subcarriers used. The update algorithm was extended to
VBLAST -OFDM systems and it showed improvements in BER performance but still
experienced an error floor. An algorithm to equalise the ICI contribution of adjacent
subcarriers was then developed and evaluated. The ICI equalisation algorithm reduces
the error floor in BER as more subcarriers are equalised at the expense of more
hardware complexity.
The connectivity of V ANET was investigated and it was found that for single lane
roads, car densities of 7 cars per communication range are sufficient to achieve high
connectivity within the city whereas 12 cars per communication range are required for
highways. Multilane roads require higher densities since cars tend to cluster in groups.
Junctions and turns have lower connectivity than straight roads due to disconnections at
the turns. Although higher densities improve the connectivity and, hence, the
performance of the network layer, it leads to poor performance at the link layer. The
IEEE 802.11 p MAC layer standard under development for V ANET uses a variant of
Carrier Sense Multiple Access (CSMA). 802.11 protocols were analysed
mathematically and via simulations and the results prove the saturation throughput of
the basic access method drops as the number of nodes increases thus yielding very low
throughput in congested areas. RTS/CTS access provides higher throughput but it
applies only to unicast transmissions. To overcome the limitations of 802.11 protocols,
we designed a protocol known as SOFT MAC which combines Space, Orthogonal
Frequency and Time multiple access techniques. In SOFT MAC the road is divided into
cells and each cell is allocated a unique group of subcarriers. Within a cell, nodes share
the available subcarriers using a combination of TDMA and CSMA. The throughput
analysis of SOFT MAC showed it has superior throughput compared to the basic access
and similar to the RTS/CTS access of 802.11
Performance of a Busy-Tone Approach on 802.11 Wireless Network
The big evolution of modem applications in the wireless networks domain as the wireless videos remote access, big files transfer, streaming and downloading high definition videos etc, has led to using the mmWave technology (60 GHz for example) that represents an important solution for the se applications because of the advantages presented by this frequency band such as the high data rate transmission up to multi gigabits, also the large bandwidth that goes up to 7 GHz.
The use of the mm Wave technology requires a MAC protocol which ensures the channel sharing between users in a multi-node network, with directional antennas that increase spatial reuse and cover a wider area compared to the omnidirecti on al antennas.
Many access method approaches were used in order to resolve these problems, for instance, the methods that use a signaling channel, then methods that exploit directional antennas with directional frames, and those using beacons and many others ....
In our project, we worked on the adaptation of the 'Busy - Tone' method using the 802.11 ad protocol with directional antennas in addition to a coordination between 2.4 GHz and 60 GHz. This method offers a big solution to resolve the collisions of data and control packets
that affect and reduce the network capacity and lead to data loss. Simulation results showed the efficiency of this model by reducing collisions caused by hidden terminais, therefore, enhancing the performance of the network in terms oftransmission delay, retransmission attempts and throughput.
L'évolution des applications modernes dans le domaine des réseaux sans fils tel que 1 'accès à distance des vidéos sans fils, le transfert des gros fichiers, flux des vidéos à haute définition etc .... nécessite l'utilisation de la bande 60 GHz qui présente une solution très importante pour ces applications grâce aux avantages que présente cette bande tel que le taux de transmission des données qui atteint quelques Gigabits, et aussi grâce à la bande passante du canal qui est environ 7 GHz.
L'utilisation de cette bande de fréquence nécessite un protocole MAC qui assure le partage de canal entre les utilisateurs dans un réseau multi-noeuds. Ce protocole doit tenir compte les problèmes et les défis qui se produisent grâce à l'utilisation de la bande 60 GHz, tel que les problèmes des terminales cachées et exposées
Dans ce projet on a proposé une méthode qui se base sur l'adaptation de protocole 802.llad avec la méthode 'Busy-Tone 'parce qu'elle représente la solution la plus efficace pour résoudre les problèmes des collisions des paquets de donnés et les paquets de contrôle qui sont causés normalement par la présence des terminales cachées et exposées.
L'approche proposée consiste aussi à utiliser les antennes directives qm augmentent la réutilisation spatiale et couvre une portée plus grande par rapport à l'antenne omnidirectionnelle. Ces antennes ont été utilisées à côté des antennes omnidirectionnelles avec une coordination entre les deux, alors les antennes omnidirectionnelles sont utilisées pour envoyer les signaux 'Busy-Tone ' tandis que les antennes directives sont utilisées pour envoyer les paquets de données. Les résultats de la simulation ont montré une amélioration au niveau de la performance du réseau en terme du débit, du délai et les essaies de retransmission en comparant avec le standard 801.11ad.
La mise en oeuvre est effectuée dans le logiciel Matlab/Simulink. Les paramètres utilisés
dans les simulations sont des valeurs typiques des centrales existantes ou prises dans la
littérature. La conformité avec la littérature est réalisée grâce à une validation croisée
progressive de chaque sous-ensemble et du système globa
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