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Mobility and opportunistic resource allocation in wireless multimedia networks
KTH, School of Electrical Engineering (EES), Communication Networks.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In order to support increasing traffic loads, mobile operators need cost-effective solutions to improve the spectral efficiency of their cellular networks, or to off-load them by diverting some of the load to other networks. Advances in the radio resource management may to some extent reduce the need for costly new deployments. The resource management should not only focus on spectrum efficiency—it should try to meet the service requirements of applications that are expected to contribute large data volumes, such as video streaming. Many of those applications are multicast/broadcast in nature (e.g., mobile TV, data podcasting). Our focus in this thesis is on resource allocation mechanisms that exploit the mobility of users. The mobility induces channel quality fluctuations and creates intermittent connectivity, which both can be used to improve the resource efficiency of wireless multimedia systems. The thesis concentrates on two areas: link-layer resource allocation for video streaming in cellular networks and mobility-assisted content distribution in hybrid cellular/ad-hoc networks.

In the area of wireless video streaming, we study bit-rate allocation, statistical multiplexing, and channel-aware scheduling. The bit-rate allocation should provide a distortion-optimal assignment of source, channel, and pilot bit-rates under link capacity constraints. We derive an analytical model that captures the video distortion as a function of the bit-rates and, based on it, we study various bit-rate allocation strategies and their robustness to varying radio conditions. The statistical multiplexing can be used to smooth out the burstiness of video streams and avoid over-provisioning of transport channels. We study the statistical multiplexing gains of H.264 video streams, both in terms of bit-rate requirements and video quality. When multiple flows are multiplexed on a shared transport channel, multi-user scheduling becomes crucial for the performance. Channel-aware scheduling exploits fluctuations in radio conditions to optimize the assignment of channel resources. We study the impact of channel-aware scheduling on the performance of delay-sensitive applications and possible extensions of channel-aware schemes to multicast scenarios.

In the area of mobility-assisted content distribution, we study the resource efficiency of mobility-assisted podcasting and we propose an analytical model for pedestrian content distribution. The mobility-assisted podcasting exploits random encounters of mobile terminals equipped with short range radios to forward the podcast episodes, thereby relieving the strain on cellular networks. We provide results on the achievable spectrum and energy savings of such scheme. Finally, we introduce the “street model”, the first building block in a conceived library of analytical models that would be used to study the performance of pedestrian content distribution in some common case scenarios of urban mobility. Based on the “street model”, we study how various system parameters and node mobility affect the efficiency of content distribution in a grid of streets that represents a part of Stockholm’s downtown area.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , viii, 38 p.
Series
Trita-EE, ISSN 1653-5146 ; 2010:017
National Category
Telecommunications
Identifiers
URN: urn:nbn:se:kth:diva-12735ISBN: 978-91-7415-628-7 (print)OAI: oai:DiVA.org:kth-12735DiVA: diva2:318419
Public defence
2010-05-06, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC20100618Available from: 2010-05-07 Created: 2010-05-07 Last updated: 2010-06-18Bibliographically approved
List of papers
1. Trade-Offs in Bit-Rate Allocation for Wireless Video Streaming
Open this publication in new window or tab >>Trade-Offs in Bit-Rate Allocation for Wireless Video Streaming
2009 (English)In: IEEE transactions on multimedia, ISSN 1520-9210, E-ISSN 1941-0077, Vol. 11, no 6, 1105-1113 p.Article in journal (Refereed) Published
Abstract [en]

One of the central problems in wireless video transmission is the choice of source and channel coding rates to allocate the available transmission rate optimally. In this paper, we present a structural distortion model for video streaming over time-varying fading channels. Based on the model, we study the end-to-end distortion for various bit-rate allocation strategies and channel conditions. We show that the robustness to channel variations is crucial for the streaming performance when frequent bit-rate adaptations are not feasible. It is achieved at the expense of higher source distortion in the encoder. Our findings are illustrated on a practical problem of distortion-optimal selection of transport formats in an adaptive modulation and coding (AMC) scheme used in HSDPA.

National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-12777 (URN)10.1109/TMM.2009.2026096 (DOI)000269776700007 ()2-s2.0-70349459496 (Scopus ID)
Note
QC20100618Available from: 2010-05-11 Created: 2010-05-11 Last updated: 2017-12-12Bibliographically approved
2. Statistical Multiplexing Gains of H.264/AVC Video in E-MBMS
Open this publication in new window or tab >>Statistical Multiplexing Gains of H.264/AVC Video in E-MBMS
2008 (English)In: IEEE International Symposium on Wireless PervasiveComputing (ISWPC): Santorini, Greece, May 2008, 2008, 468-474 p.Conference paper, Published paper (Refereed)
Abstract [en]

With the increasing acceptance of H.264/AVC as a video coding standard for mobile multimedia, it becomes very important to control the extreme burstiness of the traffic generated by the H.264/AVC encoder. Statistical multiplexing of video streams can be used to reduce the bit rate variations. In practice, the number of video streams that can be multiplexed together is quite limited and therefore, additional mechanisms are needed to eliminate the residual burstiness and to adapt the bit rate of the bundle to the bit rate of the transport channel. Here we evaluate the potential statistical multiplexing gains with and without the coordination in the encoders. The gains are measured relative to the case where rate-controlled (capped) streams are delivered on individual transport channels.

National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-12778 (URN)10.1109/ISWPC.2008.4556252 (DOI)000258921600098 ()2-s2.0-51649104125 (Scopus ID)978-142441653-0 (ISBN)
Conference
IEEE International Symposium on Wireless Pervasive Computing (ISWPC)
Note

QC20100618

Available from: 2010-05-11 Created: 2010-05-11 Last updated: 2014-10-20Bibliographically approved
3. Video Streaming Performance under Proportional Fair Scheduling
Open this publication in new window or tab >>Video Streaming Performance under Proportional Fair Scheduling
2010 (English)In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 28, no 3, 399-408 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we study the performance of the proportional fair scheduler, which has been proposed for some of the emerging radio access systems. It maximizes the spectral efficiency of the systems, which is a strong incentive for network providers to use it. Our goal is to investigate how the proportional fair scheduling affects the performance of streaming users. Focus is on the throughput-delay trade-offs associated with proportional fair scheduling in CDMA/HDR systems. Special attention is devoted to defining appropriate performance measures and creating a realistic simulation environment. Our results indicate that the opportunistic scheduling may face difficulties in providing the user-level performance in cases where streaming flows constitute a significant share of the traffic load.

Keyword
video streaming, channel-aware scheduling, proportional fair, HSDPA, LTE
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-12779 (URN)10.1109/JSAC.2010.100411 (DOI)000277063600011 ()2-s2.0-79958016062 (Scopus ID)
Note
QC 20100618Available from: 2010-05-11 Created: 2010-05-11 Last updated: 2017-12-12Bibliographically approved
4. Multicast Scheduling with Resource Fairness Constraints
Open this publication in new window or tab >>Multicast Scheduling with Resource Fairness Constraints
2009 (English)In: Wireless networks, ISSN 1022-0038, E-ISSN 1572-8196, Vol. 15, no 5, 571-583 p.Article in journal (Refereed) Published
Abstract [en]

Integration of multicast and unicast data in future radio access networks will be necessary in order to improve the resource efficiency and provide new services. Such integration requires new and efficient resource sharing mechanisms. These mechanisms need to be optimized to provide the best possible trade-off between resource efficiency and fairness. In this article, we consider a case where streaming multicast users are multiplexed together with elastic unicast users on a common time-slotted channel. We derive a system model to study the performance of various resource allocations strategies under proportional and resource fairness constraints. Fairness is directly defined in terms of the users' utilities rather than of the throughputs they are assigned to. We also describe an extension of the well-known unicast proportional fair scheduler to the multicast scenario. Through extensive simulations we demonstrate the performance of this scheduler for various traffic loads and multicast group sizes.

Keyword
Multicast scheduling, Resource sharing, Proportional fairness, Video streaming, MBMS
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-12781 (URN)10.1007/s11276-007-0085-y (DOI)000264842000003 ()2-s2.0-63749117928 (Scopus ID)
Note
QC 20100618 5th International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks and Workshop, Limassol, CYPRUS, APR 16-20, 2007Available from: 2010-05-11 Created: 2010-05-11 Last updated: 2017-12-12Bibliographically approved
5. Multicast Scheduling for Scalable Video Streaming in Wireless Networks
Open this publication in new window or tab >>Multicast Scheduling for Scalable Video Streaming in Wireless Networks
2010 (English)Conference paper, Published paper (Refereed)
Abstract [en]

We consider how relatively simple extensions of popular channel-aware schedulers can be used to multicast scalable video streams in high speed radio access networks. To support the evaluation, we first describe a model of the channel distortion of scalable video coding and validate it using eight commonly used test sequences. We use the distortion model in a detailed simulation setup to compare the performance of six schedulers, among them the Max-Sum and Max-Prod schedulers, which aim to maximize the sum and the product of streaming utilities, respectively. We investigate how the traffic load, user mobility, layering structure, and users’ aversion of fluctuating distortion influence the streaming performance. Our results show that the Max-Sum scheduler performs better than other considered schemes in almost all scenarios. With the Max-Sum scheduler, the gain of scalable video coding compared to non-scalable coding is substantial, even when users do not tolerate frequent changes in video quality.

National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-12782 (URN)10.1145/1730836.1730847 (DOI)2-s2.0-77951272469 (Scopus ID)
Conference
ACM Multimedia Systems (MMSys)
Note
QC20100618Available from: 2010-05-11 Created: 2010-05-11 Last updated: 2010-06-18Bibliographically approved
6. Spectrum and Energy Efficiency of Mobility-Assisted Podcasting in Cellular Networks
Open this publication in new window or tab >>Spectrum and Energy Efficiency of Mobility-Assisted Podcasting in Cellular Networks
2010 (English)In: MobiOpp '10 Proceedings of the Second International Workshop on Mobile Opportunistic Networking, Association for Computing Machinery (ACM), 2010, 51-57 p.Conference paper, Published paper (Refereed)
Abstract [en]

We consider a wireless podcasting service for mobile users. That service can be provided by mobile operators in their coverage areas. Our focus is on dense urban environments. The latency and throughput requirements of the podcasting service are flexible and, therefore, podcast contents do not need to be delivered to all users via the operator’s network: they can be relayed from one user to another in a store-carry-and-forward fashion. Hence, mobility of users can be used as a supplementary transport mechanism to off-load the operator’s network and relieve strain on scarce spectrum resources. In this paper, we evaluate the achievable throughputs and spectrum savings of the mobility-assisted wireless podcasting for various mobility patterns and user densities in an area. We also estimate the energy consumption of the mobility-assisted podcasting for the case when Bluetooth radios are used for peer-to-peer communication.

Place, publisher, year, edition, pages
Association for Computing Machinery (ACM), 2010
Keyword
mobile communication systems, multicast, portable devices, store and forward networks
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-12783 (URN)10.1145/1755743.1755753 (DOI)2-s2.0-77952942749 (Scopus ID)978-1-60558-925-1 (ISBN)
Conference
The Second International Workshop on Mobile Opportunistic Networking, MobiOpp '10
Note

QC 20120328

Available from: 2013-03-18 Created: 2010-05-11 Last updated: 2013-09-09Bibliographically approved
7. An Analytical Model for Pedestrian Content Distribution in a Grid of Streets
Open this publication in new window or tab >>An Analytical Model for Pedestrian Content Distribution in a Grid of Streets
2010 (English)Report (Other academic)
Abstract [en]

Mobile communication devices may be used for spreading multimedia data without support of an infrastructure. Such a scheme, where the data is carried by people walking around and relayed from device to device by means of short range radio, could potentially form a public content distribution system that spans vast urban areas. The transport mechanism is the flow of people and it can be studied but not engineered. The question addressed in this paper is how well pedestrian content distribution may work. We answer this question by modeling the mobility of people moving around in a city, constrained by a given topology. The model is supplemented by simulation of similar or related scenarios for validation and extension. Our conclusion is that contents spread well with pedestrian speeds already at low arrival rates into a studied region. Our contributions are both the results on the feasibility of pedestrian content distribution and the queuing analytic model that captures the flow of people.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010
Series
Trita-EE, ISSN 1653-5146 ; 2010:016
Keyword
mobile communication systems, portable devices, public networks, store and forward networks
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-12784 (URN)
Note
QC20100618Available from: 2010-05-11 Created: 2010-05-11 Last updated: 2013-09-09Bibliographically approved

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Permanent link

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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
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  • text
  • asciidoc
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