1,549 research outputs found
Investigation of Wireless Channel Asymmetry in Indoor Environments
Asymmetry is unquestionably an important characteristic of the wireless
propagation channel, which needs to be accurately modeled for wireless and
mobile communications, 5G networks, and associated applications such as
indoor/outdoor localization. This paper reports on the potential causes of
propagation asymmetry. Practical channel measurements at Khalifa University
premises proved that wireless channels are asymmetric in realistic scenarios.
Some important conclusions and recommendation are also summarized.Comment: Accepted in IEEE International Symposium on Antennas and Propagation
(APS17), San Diego, California, 9-14 Jul. 2017. arXiv admin note: substantial
text overlap with arXiv:1704.0687
Identifying Design Requirements for Wireless Routing Link Metrics
In this paper, we identify and analyze the requirements to design a new
routing link metric for wireless multihop networks. Considering these
requirements, when a link metric is proposed, then both the design and
implementation of the link metric with a routing protocol become easy.
Secondly, the underlying network issues can easily be tackled. Thirdly, an
appreciable performance of the network is guaranteed. Along with the existing
implementation of three link metrics Expected Transmission Count (ETX), Minimum
Delay (MD), and Minimum Loss (ML), we implement inverse ETX; invETX with
Optimized Link State Routing (OLSR) using NS-2.34. The simulation results show
that how the computational burden of a metric degrades the performance of the
respective protocol and how a metric has to trade-off between different
performance parameters
Rare: Resource Aware Routing for mEsh
An important element of any routing protocol used for Wireless Mesh Networks (WMNs) is the link cost function used to represent the radio link characteristic. The majority of the routing protocols for WMNs attempt to accurately characterise the radio link quality by constructing the link cost function from the measurements obtained using active probing techniques, which introduces overhead. In this paper we propose a new approach called Resource Aware Routing for mEsh (RARE) which instead employs passive monitoring to gather radio link information. This results in a smaller overhead than the other methods that require active network probing, and is load independent since it does not require an access to the medium. Moreover, se show that our RARE approach performs well in a real radio environment through a number of experiments performed on a static 17 node WLAN mesh testbed
A new routing metric for wireless mesh networks
In Wireless Mesh Networks the main goal is to achieve the best possible quality and efficiency of data transmission between source and destination nodes. To achieve such transmission, a routing algorithm should select better paths by taking the quality of wireless links into account. Simple path selection based on minimal hop count often leads to poor performance due to the fact that paths with low hop count often have higher packet loss rates. Better paths can be obtained by characterizing the actual quality of wireless link. A number of link quality aware routing metrics such as Expected Transmission Count (ETX), Expected Transmission Time (ETT), Weighted Cumulative Expected Transmission Time (WCETT), Metric of Interference and Channel Switching (MIC), Interference Aware Metric (iAWARE) etc have been explored. This study highlights some shortcomings of these routing metrics and proposes the design of a novel metric called ETX- 3 hop, which addresses the discussed weaknesses and works more efficiently under various link quality conditions. ETX-3hop consists of a more accurate method to measure the link quality and a path metric that better captures the quality of a path. The performance of the ETX-3hop metric is compared against the original ETX with different path metrics. In extensive simulations, ETX-3hop metric outperforms the original ETX metric in terms of network throughput
Exploring Symmetry in Wireless Propagation Channels
Wireless communications literature is very rich with empirical studies and
measurement campaigns that study the nature of the wireless propagation
channel. However, despite their undoubted usefulness, many of these studies
have omitted a fundamental yet key feature of the physical signal propagation,
that is, wireless propagation asymmetry. This feature does not agree with the
electromagnetic reciprocity theorem, and the many research papers that adopt
wireless channel symmetry, and hence rendering their modeling, unexpectedly,
inaccurate. Besides, asymmetry is unquestionably an important characteristic of
wireless channels, which needs to be accurately characterized for
vehicular/mobile communications, 5G networks, and associated applications such
as indoor/outdoor localization. This paper presents a modest and a preliminary
study that reports potential causes of propagation asymmetry. Measurements
conducted on Khalifa University campus in UAE show that wireless channels are
symmetric in the absence of symmetry impairments. Therefore, care should be
taken when considering some practical wireless propagation scenarios. Key
conclusions and recommendation are summarized. We believe that this study will
be inspiring for the academic community and will trigger further investigations
within wireless propagation assumptions.Comment: Accepted in IEEE European Conference on Networks and Communications
(EuCNC17), Oulu, Finland,12-15 Jun. 201
State-of-the-art of distributed channel assignment
Channel assignment for Wireless Mesh Networks (WMNs) attempts to increase the
network performance by decreasing the interference of simultaneous
transmissions. The reduction of interference is achieved by exploiting the
availability of fully or partially non-overlapping channels. Although it is
still a young research area, many different approaches have already been
developed. These approaches can be distinguished into centralized and
distributed. Centralized algorithms rely on a central entity, usually called
Channel Assignment Server (CAS), which calculates the channel assignment and
sends the result to the mesh routers. In distributed approaches, each mesh
router calculates its channel assignment decision based on local information.
Distributed approaches can react faster to topology changes due to node
failures or mobility and usually introduce less protocol overhead since
communication with the CAS is not necessary. As a result, distributed
approaches are more suitable once the network is operational and running.
Distributed approaches can further be classified into static and dynamic, in
regard to the modus of channel switching. In dynamic approaches, channels can
be switched on a per-packet basis, whereas in static approaches radios stay on
a specific channel for a longer period of time. Static assignments have been
more in focus, since the channel switching time for current Institute of
Electrical and Electronics Engineers (IEEE) 802.11 hardware is in the order of
milliseconds which is two orders higher than the packet transmission time.
Recently, surveys of channel assignment algorithms have been presented which
cover certain aspects of the research field. The survey in [1] introduces the
problem and presents a couple of distributed algorithms and [2] gives a broad
introduction to centralized and distributed approaches. The survey herein is
focused on distributed approaches for peer- to-peer network architectures.
This report describes the problem formulation for channel assignment in WMNs
and the fundamental concepts and challenges of this research area. We present
different distributed channel assignment algorithms and characterize them
according to a set of classification keys. Since channel assignment algorithms
may change the connectivity and therefore the network topology, they may have
a high impact on routing. Therefore, we present routing metrics that consider
channel diversity and adapt better to the multi- radio multi-channel scenario
than traditional routing metrics designed for single channel networks. The
presented algorithms are discussed and compared focusing on practical
evaluations in testbed and network environments. The implementation for real
networks is a hard and labor-intensive task because the researcher has to deal
with the complexity of the hardware, operating system, and wireless network
interface drivers. As a result, frameworks emerged in order to simplify the
implementation process. We describe these frameworks and the mechanisms used
to help researchers implementing their algorithms and show their limitations
and restrictions
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