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Capacity analysis of densely deployed wireless LANs
KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Wireless LANs (WLANs) based on the IEEE 802.11 standard have become an integral part of today’s indoor wireless communication infrastructure. As WLAN deployments become more prevalent and densely deployed, the nodes in these WLANs start to create congestion and interference with each other. This congestion and interference fundamentally limits the performance of these coexisting WLANs. We analyze the capacity limits of such densely deployed WLANs.

We begin our analysis by investigating the suitability of the attributes of WLANs, namely their cooperative operation based on locally available information, for indoor high-capacity wireless access provisioning. We compare the cooperative class of wireless systems with another class of systems whose users behave selfishly. Following this qualitative assessment, we perform a detailed, qualitative analysis of the capacity of densely deployed WLANs in terms of a number of key environmental and operational parameters. The indoor propagation environment has a significant influence on the congestion and interference that these coexisting WLANs exert on each other. Therefore we investigate the impact of propagation environment on the aggregate throughput of densely deployed WLANs. As WLANs are deployed in close proximity of each other, the transmissions in one WLAN start to influence the outcome of transmissions in other WLANs. The manner in which the access points are deployed, and the manner in which stations associate themselves with the available access points around themselves is shown to be an influential factor in the performance of these coexisting WLANs. Therefore, we investigate the impact of random versus planned access point deployment on performance of densely deployed WLANs. Similarly, we investigate the impact of stations associating with the access point with the strongest signal or with another sufficiently strong access point in their vicinity. Furthermore, we investigate the throughput of densely deployed WLANs when operating with bounded delay. More specifically we examine the case when the input traffic arriving at the transmitters are expected to reach their destination within a certain time period, thus the transmit queues cannot grow without bounded and the system should operate at a stable point.

The indoor propagation environment, creates complex interference relationships between nodes in coexisting WLANs.These complex interference relationships are compounded by the node interactions dictated by the nonlinear algorithms in the IEEE 802.11 MAC protocol, thus the problem of estimating the performance of these coexisting WLANs by means of simple analytical models becomes difficult. In contrast, detailed packet level simulations provide accurate performance estimates, although such analyses are computationally expensive. Therefore we seek to provide a model to estimate the throughput of densely deployed WLANs based on empirical throughput results of detailed simulations of such densely deployed WLANs. In addition, in our effort to develop an empirical throughput model for densely deployed WLANs, we develop a measure which we call “cell congestion” to be able to order and compare different propagation environments, and an “effective density” concept which accounts for the influence of the propagation environment on the congestion and interference experienced by a WLAN deployment of a given density. We expect these concepts to be useful in improving the operation of WLANs to be able to meet the predicted increase in demand for capacity.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , x, 91 p.
Series
TRITA-ICT-COS, ISSN 1653-6347 ; 1410
National Category
Communication Systems
Identifiers
URN: urn:nbn:se:kth:diva-154343OAI: oai:DiVA.org:kth-154343DiVA: diva2:756604
Public defence
2014-10-24, Sal A, Electrum 1, KTH, Isafjordsgatan 26, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Wireless@kth
Note

QC 20141020

Available from: 2014-10-20 Created: 2014-10-17 Last updated: 2014-10-23Bibliographically approved
List of papers
1. Distributed multichannel random access networks with selfish users
Open this publication in new window or tab >>Distributed multichannel random access networks with selfish users
2010 (English)In: Proceedings of the Fifth International Conference on Cognitive Radio Oriented Wireless Networks Communications (CROWNCOM), 2010, 2010, 5577687- p.Conference paper, Published paper (Refereed)
Abstract [en]

Dynamic spectrum access (DSA) schemes allow the users to share spectrum resources by taking advantage of the variations in spectrum demand over time and space. Carrying out dynamic spectrum allocation centrally, however, can be a complex task. For this reason, distributed schemes in which users can access the available channels independently may be preferable to centralized DSA schemes. Cognitive radio systems, which enable user terminals to sense their environment and form their action accordingly, are particularly well-suited for distributed systems. On the other hand, the freedom in distributed schemes gives the users the option to act selfishly, which has decisive effects on system performance. In this paper we consider a distributed multichannel wireless random access system where users selfishly access the channels in the system. We analyze the behavior of the selfish users by modeling the system as a non-cooperative game and we identify all stable operating points (Nash equilibria) of this game. We then compare the performance of this system with a number of cooperative distributed DSA schemes in terms of user utilities. Our results show that the performance of the selfish multichannel random access system can be comparable to cooperative schemes.

Keyword
Cognitive radio, Complex task, Cooperative schemes, Distributed schemes, Distributed systems, Dynamic spectrum access, Dynamic spectrum allocations, Multi-channel, Multichannel random access, Nash equilibria, Noncooperative game, Operating points, Random access systems, Selfish users, Spectrum demand, Time and space, User terminals, User utility
National Category
Telecommunications Communication Systems
Identifiers
urn:nbn:se:kth:diva-50683 (URN)10.4108/ICST.CROWNCOM2010.9284 (DOI)2-s2.0-77958165163 (Scopus ID)978-1-4244-5885-1 (ISBN)
Conference
2010 5th International Conference on Cognitive Radio Oriented Wireless Networks and Communications, CROWNCom 2010; Cannes; France; 9 June 2010 through 11 June 2010
Note

QC 20111208. © 2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. QC 20111207

Available from: 2011-12-07 Created: 2011-12-07 Last updated: 2014-10-20Bibliographically approved
2. Distributed Dynamic Spectrum Access in Multichannel Random Access Networks with Selfish Users
Open this publication in new window or tab >>Distributed Dynamic Spectrum Access in Multichannel Random Access Networks with Selfish Users
2010 (English)In: Wireless Communications and Networking Conference (WCNC), 2010 IEEE, IEEE , 2010, 1-6 p.Conference paper, Published paper (Refereed)
Abstract [en]

Dynamic spectrum allocation schemes enable users to share spectrum resources by exploiting the variations in spectrum demand over time and space. Performing dynamic spectrum allocation centrally can be prohibitively complex. Therefore distributed schemes in which users can access the available channels independently may be preferable to centralized allocation. However, in distributed dynamic spectrum access, the lack of central coordination makes it difficult to utilize the system resources efficiently. Furthermore, if some or all of the users decide to deviate selfishly from the commonly agreed access procedure, this may have a decisive effect on system performance. In this paper we investigate the effect of incomplete information and selfish behavior on system performance in wireless access systems. We extend previous work by studying a distributed multichannel wireless random access system. Using a game-theoretic approach, we analyze the behavior of users in the selfish system and derive the transmission strategies at the Nash equilibrium. Our results show that lack of information leads to substantial degredation in performance of cooperative systems. We also show that there is a large incentive for selfish behavior in such cooperative systems. Selfish behavior of all users, however, causes further performance degradation, particularly in high load settings.

Place, publisher, year, edition, pages
IEEE, 2010
Keyword
Cognitive radio, Communications Society, Cooperative systems, Degradation, Game theory, Narrowband, Nash equilibrium, Resource management, Space technology, System performance
National Category
Telecommunications Communication Systems
Identifiers
urn:nbn:se:kth:diva-50684 (URN)10.1109/WCNC.2010.5506420 (DOI)000299203101103 ()2-s2.0-77955027345 (Scopus ID)978-1-4244-6396-1 (ISBN)
Conference
Wireless Communications and Networking Conference (WCNC), 2010
Note

QC 20111208. © 2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. QC 20111207

Available from: 2011-12-07 Created: 2011-12-07 Last updated: 2014-10-20Bibliographically approved
3. Selfish multi-channel random access in heterogeneous channels
Open this publication in new window or tab >>Selfish multi-channel random access in heterogeneous channels
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We analyze the behavior of selfish users in a multichannel random access system in which the propagation characteristics of the available channels in the system exhibit different statistics. We formulate the behavior of the selfish users as a Bayesian game and identify the transmission strategies at the Nash equilibria. Following this, we propose a simple iterative algorithm to obtain the transmission probabilities of the selfish uses at the Nash equilibria and investigate the convergence properties of this algorithm. Using the transmission probabilities of the selfish users at the Nash equilibria, we analyze the performance of the MRA system with selfish users in terms of sum and per-user utilities and compare this system with its cooperative and scheduling system counterparts. We find that selfish behavior results in significant performance loss compared to scheduling and cooperative systems, which increases as the system load increases.

National Category
Telecommunications Communication Systems
Identifiers
urn:nbn:se:kth:diva-51071 (URN)
Note

QC 20120328

Available from: 2011-12-09 Created: 2011-12-09 Last updated: 2016-06-20Bibliographically approved
4. Effect of propagation environment on area throughput of dense WLAN deployments
Open this publication in new window or tab >>Effect of propagation environment on area throughput of dense WLAN deployments
2013 (English)In: 9th IEEE Broadband wireless access workshop (BWA 2013), IEEE Computer Society, 2013, 333-338 p.Conference paper, Published paper (Refereed)
Abstract [en]

Indoor wireless LAN deployments have become ubiquitous. As WLAN deployments become increasingly dense, WLANs start to cause more and more contention and interference to each other, to the point that they cause significant throughput degradation to other WLANs. Since WLANs are one of the most commonplace solutions to provide indoor broadband data access, it is crucial to assess the throughput limits of WLANs in order to understand at what demand level novel broadband access mechanisms will be critically needed. The amount of contention and interference that coexisting WLANs create on each other is influenced by the indoor propagation environment such as existence of walls or clutter. Although the indoor propagation environment has a significant impact on the interaction between WLANs, and consequently on the area throughput, the relationship between the indoor propagation environment and achievable area throughput has not received much attention. In this paper, we investigate the area throughput of densely deployed WLANs in different indoor propagation environments by conducting detailed MAC layer simulations using OPNET. The results show that the propagation conditions have a profound impact on achievable area throughput; as much as several tens of times increase in highly cluttered environments compared to open areas.

Place, publisher, year, edition, pages
IEEE Computer Society, 2013
Keyword
Broadband networks, Broad-band data, Broadband access, Cluttered environments, Dense WLAN, Indoor propagation, MAC layer, Propagation environment, Throughput degradation
National Category
Communication Systems Telecommunications
Identifiers
urn:nbn:se:kth:diva-136227 (URN)10.1109/GLOCOMW.2013.6825009 (DOI)2-s2.0-84902950612 (Scopus ID)978-147992851-4 (ISBN)
Conference
2013 IEEE Globecom Workshops, GC Wkshps 2013; Atlanta, GA; United States; 9 December 2013 through 13 December 2013
Funder
Wireless@kth
Note

QC 20140912

Available from: 2013-12-06 Created: 2013-12-04 Last updated: 2014-10-20Bibliographically approved
5. Association and deployment considerations in dense wireless LANs
Open this publication in new window or tab >>Association and deployment considerations in dense wireless LANs
2014 (English)In: Vehicular Technology Conference (VTC Spring), 2014 IEEE 79th, IEEE conference proceedings, 2014Conference paper, Published paper (Refereed)
Abstract [en]

Wireless LANs based on the IEEE 802.11 standard are one of the most commonplace indoor wireless access solutions. As the ever growing demand for data consumption necessitates higher rates and volumes, it is fairly common to observe more and more WLANs being deployed in close proximity to each other. As distances between WLAN installations diminish, the access points (APs) and stations (STAs) in these WLANs create a complex interference environment, which is also compounded by the indoor propagation environment. In this paper, we investigate the impact of two important parameters related to the deployment and operation of densely deployed wireless LANs on the aggregate throughput obtained by all the nodes in these WLANs. The first such operational parameter we investigate is access point and user station association; namely, whether STAs associate with a random ``strong'' AP or the AP from which they obtain the strongest received power. The second operational parameter we consider is the way in which APs are placed in the indoor environment; namely, whether APs are deployed randomly or in a manner to reduce inter-AP interference. In order to account for the complex node interactions in the MAC layer, which is crucial for accurate performance estimation, we perform packet-level simulations using OPNET. Our results show that the type of node association used in densely deployed WLANs has a critical impact on the aggregate throughput. In comparison, the type of AP deployment used is not nearly as significant; varying from moderate to no impact at all.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2014
Series
IEEE Vehicular Technology Conference, ISSN 1550-2252
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-154336 (URN)10.1109/VTCSpring.2014.7022839 (DOI)2-s2.0-84936886431 (Scopus ID)
Conference
2014 79th IEEE Vehicular Technology Conference, VTC 2014-Spring, Seoul, South Korea, 18 May 2014 through 21 May 2014
Note

QC 20151214

Available from: 2014-10-17 Created: 2014-10-17 Last updated: 2016-11-11Bibliographically approved
6. Delay bound capacity analysis of dense WLANs
Open this publication in new window or tab >>Delay bound capacity analysis of dense WLANs
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Indoor WLAN deployments are becoming denser such that it is fairly common to observe several WLANs operating on the same channel. Increasing density creates more congestion and interference on these WLANs, which potentially has a significant impact on the delay and throughput performance of these WLANs. Therefore, we investigate the behavior of MAC layer delay and aggregate throughput in densely deployed WLANs in connection with different traffic arrival rates, propagation environments and deployment choices. The novelty of this work is that such a comprehensive study has not been performed before. We perform an extensive simulation study using OPNET by incorporating in our analysis a realistic MAC model and the impact of indoor propagation environment causing hidden nodes. We identify the relationship between delay and aggregate throughput in a system of densely deployed WLANs and propose guidelines for determining suitable WLAN deployment densities in different propagation environments.

National Category
Communication Systems Telecommunications
Identifiers
urn:nbn:se:kth:diva-154337 (URN)
Note

QS 2014

Available from: 2014-10-17 Created: 2014-10-17 Last updated: 2014-10-20Bibliographically approved
7. An empirical aggregate throughput model for dense WLANs
Open this publication in new window or tab >>An empirical aggregate throughput model for dense WLANs
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Due to the popularity of WLANs based on the IEEE 802.11 standard, these WLANs are being deployed in close proximity of each other in urban office and residential environments. This dense deployment of WLANs, in combination with the complex indoor propagation environment created by walls, make the performance analysis of such a system of WLANs difficult. Existing WLAN throughput models cannot accurately represent the aggregate throughput performance of these systems. Performing a packet-level analysis of each system of WLANs would be accurate but costly in time and computational resources. In this work, we propose an empirical aggregate throughput model for a system of densely deployed WLANs based on a comprehensive simulation analysis of such WLANs using OPNET. Our proposed model can estimate the throughput performance of a system of WLANs with fairly good accuracy in a range of propagation environments, deployment densities, deployment and association types.

National Category
Communication Systems Telecommunications
Identifiers
urn:nbn:se:kth:diva-154340 (URN)
Note

QS 2014

Available from: 2014-10-17 Created: 2014-10-17 Last updated: 2014-10-20Bibliographically approved

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