1,418 research outputs found
Towards efficient coexistence of IEEE 802.15.4e TSCH and IEEE 802.11
A major challenge in wide deployment of smart wireless devices, using
different technologies and sharing the same 2.4 GHz spectrum, is to achieve
coexistence across multiple technologies. The IEEE~802.11 (WLAN) and the IEEE
802.15.4e TSCH (WSN) where designed with different goals in mind and both play
important roles for respective applications. However, they cause mutual
interference and degraded performance while operating in the same space. To
improve this situation we propose an approach to enable a cooperative control
which type of network is transmitting at given time, frequency and place.
We recognize that TSCH based sensor network is expected to occupy only small
share of time, and that the nodes are by design tightly synchronized. We
develop mechanism enabling over-the-air synchronization of the Wi-Fi network to
the TSCH based sensor network. Finally, we show that Wi-Fi network can avoid
transmitting in the "collision periods". We provide full design and show
prototype implementation based on the Commercial off-the-shelf (COTS) devices.
Our solution does not require changes in any of the standards.Comment: 8 page
Time-Driven Access and Forwarding for Industrial Wireless Multihop Networks
The deployment of wireless technologies in industrial networks is very promising mainly due to their inherent flexibility. However, current wireless solutions lack the capability to provide the deterministic, low delay service required by many industrial applications. Moreover, the high level of interference generated by industrial equipment limits the coverage that ensures acceptable performance. Multi-hop solutions, when combining frame forwarding with higher node density, have the potential to provide the needed coverage while keeping radio communication range short. However, in multi-hop solutions the medium access time at each of the nodes traversed additively contributes to the end-to-end delay and the forwarding delay (i.e., the time required for packets to be processed, switched, and queued) at each node is to be added as well. This paper describes Time-driven Access and Forwarding (TAF), a solution for guaranteeing deterministic delay, at both the access and forwarding level, in wireless multi-hop networks, analyzes its properties, and assesses its performance in industrial scenario
SourceSync: A Distributed Wireless Architecture for Exploiting Sender Diversity
Diversity is an intrinsic property of wireless networks. Recent years have witnessed the emergence of many distributed protocols like ExOR, MORE, SOAR, SOFT, and MIXIT that exploit receiver diversity in 802.11-like networks. In contrast, the dual of receiver diversity, sender diversity, has remained largely elusive to such networks.
This paper presents SourceSync, a distributed architecture for harnessing sender diversity. SourceSync enables concurrent senders to synchronize their transmissions to symbol boundaries, and cooperate to forward packets at higher data rates than they could have achieved by transmitting separately. The paper shows that SourceSync improves the performance of opportunistic routing protocols. Specifically, SourceSync allows all nodes that overhear a packet in a wireless mesh to simultaneously transmit it to their nexthops, in contrast to existing opportunistic routing protocols that are forced to pick a single forwarder from among the overhearing nodes. Such simultaneous transmission reduces bit errors and improves throughput. The paper also shows that SourceSync increases the throughput of 802.11 last hop diversity protocols by allowing multiple APs to transmit simultaneously to a client, thereby harnessing sender diversity. We have implemented SourceSync on the FPGA of an 802.11-like radio platform. We have also evaluated our system in an indoor wireless testbed, empirically showing its benefits.National Science Foundation (U.S.) (Award CNS-0831660)United States. Defense Advanced Research Projects Agency. Information Theory for Mobile Ad-Hoc Networks Progra
Overlapping Multi-hop Clustering for Wireless Sensor Networks
Clustering is a standard approach for achieving efficient and scalable
performance in wireless sensor networks. Traditionally, clustering algorithms
aim at generating a number of disjoint clusters that satisfy some criteria. In
this paper, we formulate a novel clustering problem that aims at generating
overlapping multi-hop clusters. Overlapping clusters are useful in many sensor
network applications, including inter-cluster routing, node localization, and
time synchronization protocols. We also propose a randomized, distributed
multi-hop clustering algorithm (KOCA) for solving the overlapping clustering
problem. KOCA aims at generating connected overlapping clusters that cover the
entire sensor network with a specific average overlapping degree. Through
analysis and simulation experiments we show how to select the different values
of the parameters to achieve the clustering process objectives. Moreover, the
results show that KOCA produces approximately equal-sized clusters, which
allows distributing the load evenly over different clusters. In addition, KOCA
is scalable; the clustering formation terminates in a constant time regardless
of the network size
Security and Privacy Issues in Wireless Mesh Networks: A Survey
This book chapter identifies various security threats in wireless mesh
network (WMN). Keeping in mind the critical requirement of security and user
privacy in WMNs, this chapter provides a comprehensive overview of various
possible attacks on different layers of the communication protocol stack for
WMNs and their corresponding defense mechanisms. First, it identifies the
security vulnerabilities in the physical, link, network, transport, application
layers. Furthermore, various possible attacks on the key management protocols,
user authentication and access control protocols, and user privacy preservation
protocols are presented. After enumerating various possible attacks, the
chapter provides a detailed discussion on various existing security mechanisms
and protocols to defend against and wherever possible prevent the possible
attacks. Comparative analyses are also presented on the security schemes with
regards to the cryptographic schemes used, key management strategies deployed,
use of any trusted third party, computation and communication overhead involved
etc. The chapter then presents a brief discussion on various trust management
approaches for WMNs since trust and reputation-based schemes are increasingly
becoming popular for enforcing security in wireless networks. A number of open
problems in security and privacy issues for WMNs are subsequently discussed
before the chapter is finally concluded.Comment: 62 pages, 12 figures, 6 tables. This chapter is an extension of the
author's previous submission in arXiv submission: arXiv:1102.1226. There are
some text overlaps with the previous submissio
ptp++: A Precision Time Protocol Simulation Model for OMNeT++ / INET
Precise time synchronization is expected to play a key role in emerging
distributed and real-time applications such as the smart grid and Internet of
Things (IoT) based applications. The Precision Time Protocol (PTP) is currently
viewed as one of the main synchronization solutions over a packet-switched
network, which supports microsecond synchronization accuracy. In this paper, we
present a PTP simulation model for OMNeT++ INET, which allows to investigate
the synchronization accuracy under different network configurations and
conditions. To show some illustrative simulation results using the developed
module, we investigate on the network load fluctuations and their impacts on
the PTP performance by considering a network with class-based
quality-of-service (QoS) support. The simulation results show that the network
load significantly affects the network delay symmetry, and investigate a new
technique called class probing to improve the PTP accuracy and mitigate the
load fluctuation effects.Comment: Published in: A. F\"orster, C. Minkenberg, G. R. Herrera, M. Kirsche
(Eds.), Proc. of the 2nd OMNeT++ Community Summit, IBM Research - Zurich,
Switzerland, September 3-4, 201
Wi-Fi Teeter-Totter: Overclocking OFDM for Internet of Things
The conventional high-speed Wi-Fi has recently become a contender for
low-power Internet-of-Things (IoT) communications. OFDM continues its adoption
in the new IoT Wi-Fi standard due to its spectrum efficiency that can support
the demand of massive IoT connectivity. While the IoT Wi-Fi standard offers
many new features to improve power and spectrum efficiency, the basic physical
layer (PHY) structure of transceiver design still conforms to its conventional
design rationale where access points (AP) and clients employ the same OFDM PHY.
In this paper, we argue that current Wi-Fi PHY design does not take full
advantage of the inherent asymmetry between AP and IoT. To fill the gap, we
propose an asymmetric design where IoT devices transmit uplink packets using
the lowest power while pushing all the decoding burdens to the AP side. Such a
design utilizes the sufficient power and computational resources at AP to trade
for the transmission (TX) power of IoT devices. The core technique enabling
this asymmetric design is that the AP takes full power of its high clock rate
to boost the decoding ability. We provide an implementation of our design and
show that it can reduce the IoT's TX power by boosting the decoding capability
at the receivers
- …