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Coexistence and Energy Efficiency in Wireless Networks
KTH, School of Electrical Engineering (EES), Communication Networks.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Dynamic spectrum access has been recently proposed to increase the utilization of the licensed spectrum bands, and support the constantly growing volumes of mobile traffic in the modern society. At the same time, the increasing demand for wireless connectivity, as a result of the rapid emergence of innovative wireless and mobile services, has led to the deployment of various wireless technologies in the open ISM bands. This thesis addresses the effective coexistence among the diverse wireless technologies in the above scenarios, and the energy efficiency of the deployed wireless systems, both listed among the key challenges that wireless networking is facing today.

We discuss cooperative sensing, a fundamental mechanism for allowing unlicensed users perform opportunistic access in the licensed spectrum. Considering the scenario where the users perform both sensing and unlicensed spectrum access, we evaluate the efficiency of multi-channel cooperative sensing schemes with respect to the per user achievable capacity. We conclude that a careful optimization of both the number of sensed channels, and the allocation of sensing duties to the network users is necessary to achieve high capacity gains in large-scale networks of unlicensed users.

We address a number of energy efficient design issues for sensor networks and wireless LANs. We study how to improve the energy efficiency of lowpower sensor networks operating under the interference from a coexisting WLAN. We propose a cognitive, cross-layer access control mechanism that minimizes the energy cost for multi-hop WSN communication, by deriving energy-optimal packet lengths and single-hop transmission distances, based on the knowledge of the stochastic channel activity patterns of the interfering WLAN. We show that the proposed mechanism leads to significant performance improvements on both energy efficiency, as well as end-to-end latency in multi-hop WSN communication, under different levels of interference. Additionally, we develop and validate the considered WLAN channel activity model and implement efficient, lightweight, real-time parameter estimation methods.

We investigate how to enhance the multi-hop communication performance in ad hoc WLANs, when 802.11 stations operate under a power saving dutycycle scheme. We extend the traffic announcement scheme of the 802.11 power saving mode, allowing the stations to propagate pending frame notifications to all nodes in the end-to-end forwarding path of a network flow. We study the performance of the proposed scheme with respect to end-to-end packet delay and signaling overhead, while we investigate the impact on the achievable duty-cycle ratios of the wireless stations. For the purpose of the evaluation, and for the comparison with the standard 802.11 power saving mechanism, we implement the protocol extension in a development platform.

Finally, we study how the combination of the objectives for energy efficiency and a high quality of service impacts the topology stability of selforganized ad hoc networks comprised of individual agents. Based on a noncooperative game theoretic model for topology formation, we identify key extensions in the nodes’ strategy profile space that guarantees a stable network formation under multi-objective player utility functions.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , vii, 64 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2015:009
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-165168ISBN: 978-91-7595-520-9 (print)OAI: oai:DiVA.org:kth-165168DiVA: diva2:807553
Public defence
2015-05-12, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:15 (English)
Opponent
Supervisors
Note

QC 20150424

Available from: 2015-04-24 Created: 2015-04-23 Last updated: 2015-04-24Bibliographically approved
List of papers
1. Spectrum sharing with low power primary networks
Open this publication in new window or tab >>Spectrum sharing with low power primary networks
2014 (English)In: 2014 IEEE International Symposium on Dynamic Spectrum Access Networks, DYSPAN 2014, IEEE Computer Society, 2014, 315-326 p.Conference paper, Published paper (Refereed)
Abstract [en]

Access to unused spectrum bands of primary networks requires a careful optimization of the secondary cooperative spectrum sensing, if the transmission powers in the two networks are comparable. In this case the reliability of the sensing depends significantly on the spatial distribution of the cooperating nodes. In this paper we study the efficiency of cooperative sensing over multiple bands, sensed and shared by a large number of secondary users. We show that the per user cognitive capacity is maximized, if both the number of bands sensed by the secondary network as a whole, and the subsets of these bands sensed by the individual nodes are optimized. We derive the fundamental limits under different sensing duty allocation schemes. We show that with some coordination the per user cognitive capacity can be kept nearly independent from the network density.

Place, publisher, year, edition, pages
IEEE Computer Society, 2014
Series
IEEE International Symposium on Dynamic Spectrum Access Networks, ISSN 2334-3125
Keyword
Cognitive Radio Networks, Access
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-140530 (URN)10.1109/DySPAN.2014.6817808 (DOI)000341654800037 ()2-s2.0-84902170102 (Scopus ID)978-147992661-9 (ISBN)
Conference
2014 IEEE International Symposium on Dynamic Spectrum Access Networks, DYSPAN 2014; McLean, VA; United States; 1 April 2014 through 4 April 2014
Note

QC 20140602

Available from: 2014-01-25 Created: 2014-01-25 Last updated: 2015-04-24Bibliographically approved
2. Energy Efficient COGnitive MAC for Sensor Networks under WLAN Co-existence
Open this publication in new window or tab >>Energy Efficient COGnitive MAC for Sensor Networks under WLAN Co-existence
2015 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 14, no 7, 18 p.4075-4089 p.Article in journal (Refereed) Published
Abstract [en]

Energy efficiency has been the driving force behind the design of communication protocols for battery-constrained wireless sensor networks (WSNs). The energy efficiency and the performance of the proposed protocol stacks, however, degrade dramatically in case the low-powered WSNs are subject to interference from high-power wireless systems such as WLANs. In this paper we propose COG-MAC, a novel cognitive medium access control scheme (MAC) for IEEE 802.15.4-compliant WSNs that minimizes the energy cost for multihop communications, by deriving energy-optimal packet lengths and single-hop transmission distances based on the experienced interference from IEEE 802.11 WLANs. We evaluate COG-MAC by deriving a detailed analytic model for its performance and by comparing it with previous access control schemes. Numerical and simulation results show that a significant decrease in packet transmission energy cost, up to 66%, can be achieved in a wide range of scenarios, particularly under severe WLAN interference. COGMAC is, also, lightweight and shows high robustness against WLAN model estimation errors and is, therefore, an effective, implementable solution to reduce the WSN performance impairment when coexisting with WLANs.

Publisher
18 p.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-165179 (URN)10.1109/TWC.2015.2416336 (DOI)000357805200043 ()2-s2.0-84937064980 (Scopus ID)
Note

QC 20150810

Available from: 2015-04-24 Created: 2015-04-24 Last updated: 2017-12-04Bibliographically approved
3. Discrete stochastic optimization based parameter estimation for modeling partially observed WLAN spectrum activity
Open this publication in new window or tab >>Discrete stochastic optimization based parameter estimation for modeling partially observed WLAN spectrum activity
2012 (English)In: Infocommunications Journal, ISSN 2061-2079, Vol. 4, no 2, 11-17 p.Article in journal (Refereed) Published
Abstract [en]

Modeling and parameter estimation of spectrum usage in the ISM band would allow the competing networking technologies to adjust their medium access control accordingly, leading to the more efficient use of the shared spectrum. Tn this paper we address the problem of WLAN spectrum activity model parameter estimation. We propose a solution based on discrete stochastic optimization, that allows accurate spectrum activity modeling and can be implemented even in wireless sensor nodes with limited computational and energy resources.

Keyword
Cognitive networks, Discrete stochastic optimization, WLAN spectrum activity
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-104923 (URN)2-s2.0-84865741948 (Scopus ID)
Funder
ICT - The Next Generation
Note

QC 20121114

Available from: 2012-11-14 Created: 2012-11-14 Last updated: 2015-04-24Bibliographically approved
4. Closing the gap between traffic workload and channel occupancy models for 802.11 networks
Open this publication in new window or tab >>Closing the gap between traffic workload and channel occupancy models for 802.11 networks
2014 (English)In: Ad hoc networks, ISSN 1570-8705, E-ISSN 1570-8713, Vol. 21, 60-83 p.Article in journal (Refereed) Published
Abstract [en]

The modeling of wireless network traffic is necessary to evaluate the possible gains of spectrum sharing and to support the design of new cognitive protocols that can use spectrum efficiently in network environments where diverse technologies coexist. In this paper we focus on IEEE 802.11 wireless local area networks and close the gap between two popular levels of modeling, macroscopic traffic workload modeling and microscopic channel occupancy modeling. We consider traffic streams generated by established traffic workload models and characterize the networking scenarios where a simple, semi-Markovian channel occupancy model accurately predicts the wireless channel usage. Our results demonstrate that the proposed channel occupancy model can capture the channel idle time distribution in most of the scenarios, while the Markovian assumption cannot be validated in all cases.

Keyword
802.11 Networks, Traffic models, Channel occupancy models, Statistical validation
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-140608 (URN)10.1016/j.adhoc.2014.05.001 (DOI)000339598700004 ()2-s2.0-84903793061 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme, 287613
Note

QC 20140822

Available from: 2014-01-28 Created: 2014-01-28 Last updated: 2017-12-06Bibliographically approved
5. Enhanced Power Saving Mode for Low-Latency Communication in Multi-Hop 802.11 Networks
Open this publication in new window or tab >>Enhanced Power Saving Mode for Low-Latency Communication in Multi-Hop 802.11 Networks
2014 (English)In: Ad hoc networks, ISSN 1570-8705, E-ISSN 1570-8713, Vol. 23, no December 2014, 18-33 p.Article in journal (Refereed) Published
Abstract [en]

The Future Internet of Things (IoT) will connect billions of battery-powered radio-enabled devices. Some of them may need to communicate with each other and with Internet gateways (border routers) over multi-hop links. While most IoT scenarios assume that for this purpose devices use energy-efficient IEEE 802.15.4 radios, there are use cases where IEEE 802.11 is preferred despite its potentially higher energy consumption. We extend the IEEE 802.11 power saving mode (PSM), which allows WLAN devices to enter a low-power doze state to save energy, with a traffic announcement scheme that facilitates multi-hop communication. The scheme propagates traffic announcements along multi-hop paths to ensure that all intermediate nodes remain awake to receive and forward the pending data frames with minimum latency. Our simulation results show that the proposed Multi-Hop PSM (MH-PSM) improves both end-to-end delay and doze time compared to the standard PSM; therefore, it may optimize WLAN to meet the networking requirements of IoT devices. MH-PSM is practical and software-implementable since it does not require changes to the parts of the IEEE 802.11 medium access control that are typically implemented on-chip. We implemented MH-PSM as a part of a WLAN driver for Contiki OS, which is an operating system for resource-constrained IoT devices, and we demonstrated its efficiency experimentally.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-132366 (URN)10.1016/j.adhoc.2014.06.001 (DOI)000342251600002 ()2-s2.0-84906309571 (Scopus ID)
Note

QC 20140826

Available from: 2013-10-25 Created: 2013-10-25 Last updated: 2017-12-06Bibliographically approved
6. The Stability of Multiple Objective RPL Tree Formation
Open this publication in new window or tab >>The Stability of Multiple Objective RPL Tree Formation
(English)Manuscript (preprint) (Other academic)
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-165178 (URN)
Funder
ICT - The Next Generation
Note

QS 2015

Available from: 2015-04-24 Created: 2015-04-24 Last updated: 2015-04-24Bibliographically approved

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