@phdthesis {Simula.simula.1864,
	title = {Multipath Aggregation of Heterogenous Access Networks},
	year = {2012},
	school = {University of Oslo},
	type = {phd},
	abstract = {The explosive deployment of wired and wireless communication infrastructure has recently enabled many novel applications and sparked new research problems. One of the unsolved issues in today\&$\#$39;s Internet - the main topic of this thesis - is the goal of increasing data transfer speeds of end hosts by aggregating and simultaneously using multiple network interfaces. This objective is most interesting when the Internet is accessible through several, relatively slow and variable (typically wireless) networks, which are unable to single-handedly provide the required data rate for resource-intensive applications, such as bulk file transfers and high-definition multimedia streaming. Communication devices equipped with multiple network interfaces are now commonplace. Smartphones and laptops are often shipped with built-in network adapters of different wireless technologies, typically enabling them to connect to wireless local area networks and cellular data networks (such as WLAN and HSPA). At the same time, wireless network coverage has become so widespread that mobile devices are often located in overlapping coverage areas of independent access networks. However, even if multiple interfaces are successfully connected to the Internet, operating systems typically use only a single default interface for data transmission, leaving secondary interfaces idle. This technical restriction is based on the fact that the majority of current Internet traffic is conveyed by transport protocols (TCP and UDP) that do not support multiple IP addresses per endpoint. Another crucial factor is that path heterogeneity introduces packet reordering, which can negatively affect the performance of transport protocols and strain the buffer requirements of applications. This thesis explores the problem of multipath aggregation with the attempt to find solutions that achieve increased data throughput by concurrently utilizing heterogeneous and dynamic access networks. We strive for approaches that support existing applications without requiring significant modifications to the current infrastructure. The exploration starts at the IP layer with a study of the IP packet reordering that is caused by the use of heterogeneous paths. Our practical experiments confirm that multipath reordering exceeds the typical packet reordering in the Internet by an extent that renders the usual reordering metric useless. The outcome of our network-layer study is a proxy-based, adaptive multipath scheduler that is able to mitigate packet reordering while transparently forwarding a single transport connection over multiple paths. After introducing a novel metric for quantifying the benefit of path aggregation, our analysis continues on the transport layer, where we investigate TCP\&$\#$39;s resilience to multipath-inflicted packet reordering. While IP packet reordering is known for its destructive effect on TCP\&$\#$39;s performance, our practical experiments indicate that a modern implementation is significantly more robust to packet reordering than standard TCP and achieves a substantial aggregation benefit even in certain cases of extreme multipath hetiii iv erogeneity. In addition, we run a large set of emulation-based multipath experiments and identify several TCP parameters that lead to improved multipath performance when correctly tuned. Finally, we present an application-layer solution that builds upon the idea of logical file segmentation for streaming a single video to multihomed clients. The novelity of this approach lies in diverting standard protocol features (i.e., HTTP pipelining and range retrieval requests) from their intended purpose and using them for scheduling video segments over different paths. Interoperable with existing server infrastructure, our proposed solution can be deployed in a lightweight and purely client-based manner. We validate the proposed algorithms by implementing them into an existing video streaming platform.},
	author = {Kaspar, Dominik}
}
@inproceedings {Simula.simula.700,
	title = {Demo: Quality-Adaptive Video Streaming With Dynamic Bandwidth Aggregation on Roaming, Multi-Homed Clients},
	journal = {Proceedings of the 9th international conference on Mobile systems, applications, and services (MOBISYS)},
	year = {2011},
	month = {July},
	pages = {355-356},
	publisher = {ACM},
	type = {Conference},
	address = {New York},
	abstract = {In this paper, we combined our earlier work in quality adaptive streaming and bandwidth aggregation with automatic network detection. If a client detects and can connect to multiple networks, the bandwidth is aggregated dynamically, resulting in a higher video quality.},
	isbn = {978-1-4503-0643-0},
	author = {Evensen, Kristian and Petlund, Andreas and Kaspar, Dominik and Griwodz, Carsten and Halvorsen, P{\r a}l and Riiser, Haakon and Vigmostad, Paul},
	editor = {Agrawala, Ashok}
}
@inproceedings {Simula.simula.178,
	title = {Improving the Performance of Quality-Adaptive Video Streaming Over Multiple Heterogeneous Access Networks},
	journal = {Proceedings of the second annual ACM conference on Multimedia systems (MMSYS)},
	year = {2011},
	month = {February},
	pages = {57-68},
	publisher = {ACM},
	type = {Conference},
	abstract = {Devices capable of connecting to multiple, overlapping networks simultaneously are becoming increasingly common. For example, most laptops are equipped with LAN- and WLAN-interfaces, and smart phones can typically connect to both WLANs and 3G mobile networks. At the same time, streaming high-quality video is becoming increasingly popular. However, due to bandwidth limitations or the unreliable and unpredictable nature of some types of networks, streaming video can be subject to frequent periods of rebuffering and characterised by a low picture quality. In this paper, we present a client-side request scheduler that distributes requests for the video over multiple heterogeneous interfaces simultaneously. Each video is divided into independent segments with constant duration, enabling segments to be requested over separate links, utilizing all the available bandwidth. To increase performance even further, the segments are divided into smaller subsegments, and the sizes are dynamically calculated on the fly, based on the throughput of the different links. This is an improvement over our earlier subsegment approach, which divided segments into fixed size subsegments. Both subsegment approaches were evaluated with on-demand streaming and quasi-live streaming. The new subsegment approach reduces the number of playback interruptions and improves video quality significantly for all cases where the earlier approach struggled. Otherwise, they show similar performance.},
	isbn = {978-1-4503-0518-1},
	author = {Evensen, Kristian and Kaspar, Dominik and Griwodz, Carsten and Halvorsen, P{\r a}l and Audun Fosselie {Hansen} and Paal Einar {Engelstad}},
	editor = {Ketan Mayer-Pate {Begen}}
}
@inproceedings {Simula.simula.352,
	title = {Loss Differentiation and Recovery in TCP Over Wireless Wide-Area Networks},
	journal = {The Tenth International Conference on Networks (ICN 2011)},
	year = {2011},
	month = {January},
	publisher = {IARIA},
	type = {Conference},
	abstract = {The increasing speed and coverage of wireless wide- area networks (WWAN) has made technologies such as GPRS, UMTS, or HSDPA a popular way to access the Internet for both mobile and stationary users. However, depending on the scenario, WWAN can suffer from severe IP packet loss due to corruption, which is mistaken by TCP as an indication of path congestion. This paper presents an approach to solve the loss differentiation problem for the widespread scenario of wireless networks being used as access networks to the Internet. Our solution allows TCP to distinguish between congestion and corruption loss and to properly react to both phenomena. Loss differentiation is achieved by placing an assisting agent on the WWAN\&$\#$39;s base station, which replies a TCP sender in the wired Internet with a new type of acknowledgement. Without harming TCP\&$\#$39;s end-to- end semantics, these acknowledgements provide feedback about congestion on the wired path and corruption on the wireless path and support the sender in taking remedial action. Results from simulations indicate that our proposed corruption recovery algorithm significantly improves the TCP goodput. In addition, excessive RTO growth and pauses in the TCP flow that result from repeated packet corruption are considerably reduced.},
	isbn = {978-1-61208-002-4},
	author = {Bosau, Detlef and Unger, Herwig and Lada-On, Lertsuwanakul and Kaspar, Dominik}
}
@inproceedings {Simula.simula.662,
	title = {Mobile Video Streaming Using Location-Based Network Prediction and Transparent Handover},
	journal = {NOSSDAV},
	year = {2011},
	month = {May},
	pages = {21-26},
	publisher = {ACM},
	type = {Conference},
	edition = {21},
	address = {New York},
	abstract = {A well known challenge with mobile video streaming is fluctuating bandwidth. As the client devices move in and out of network coverage areas, the users may experience varying signal strengths, competition for the available resources and periods of network outage. These conditions have a significant effect on video quality. In this paper, we present a video streaming solution for roaming clients that is able to compensate for the effects of oscillating bandwidth through bandwidth prediction and video quality scheduling. We combine our existing adaptive segmented HTTP streaming system with 1) an application layer framework for creating transparent multi-link applications, and 2) a location based QoS information system containing GPS coordinates and accompanying bandwidth measurements, populated through crowd-sourcing. Additionally, we use real-time traffic information to improve the prediction by, for example, estimating the length of a commute route. To evaluate our prototype, we performed real-world experiments using a popular tram route in Oslo, Norway. The client connected to multiple networks, and the results show that our solution increases the perceived video quality significantly. Also, we used simulations to evaluate the potential of aggregating bandwidth along the route.},
	isbn = {978-1-4503-0777-2},
	author = {Evensen, Kristian and Petlund, Andreas and Riiser, Haakon and Vigmostad, Paul and Kaspar, Dominik and Griwodz, Carsten and Halvorsen, P{\r a}l},
	editor = {Krasic, Charles and Li, Kang}
}
@article {Simula.simula.860,
	title = {Using Bandwidth Aggregation to Improve the Performance of Quality-Adaptive Streaming},
	journal = {Signal Processing: Image Communication},
	volume = {27},
	number = {4},
	year = {2011},
	pages = {312-328},
	publisher = {Elsevier},
	abstract = {Devices capable of connecting to multiple, overlapping networks simultaneously is becoming increasingly common. For example, most laptops are equipped with LAN- and WLAN-interface, and smart phones can typically connect to both WLANs and 3G mobile networks. At the same time, streaming high-quality video is becoming increasingly popular. However, due to bandwidth limitations or the unreliable and unpredictable nature of some types of networks, streaming video can be subject to frequent periods of rebuffering and characterized by a low picture quality. In this paper, we present a multilink extension to the data retrieval part of the DAVVI adaptive, segmented video streaming system. DAVVI implements the same core functionality as the MPEG DASH standard. It uses HTTP to retrieve data, segments video, provides clients with a description of the content, and allows clients to switch quality during playback. Any DAVVI-data retrieval extensions can also be implemented in a DASH-solution. The multilink-enabled DAVVI client divides video segments into smaller subsegments, which are requested over multiple interfaces simultaneously. The size of each subsegment is dynamic and calculated on the fly, based on the throughput of the different links. This is an improvement over our earlier subsegment approach, which divided segments into fixed size subsegments. The quality of the video is adapted based on the measured, aggregated throughput. Both the static and the dynamic subsegment approaches were evaluated with on-demand streaming and quasi-live streaming. The new subsegment approach reduces the number of playback interruptions and improves video quality significantly for all cases where the earlier approach struggled. Otherwise, they show similar performance.},
	doi = {doi:10.1016/j.image.2011.10.007},
	author = {Evensen, Kristian and Kaspar, Dominik and Griwodz, Carsten and Halvorsen, P{\r a}l and Audun Fosselie {Hansen} and Paal Einar {Engelstad}}
}
@inproceedings {Simula.simula.690,
	title = {Using Multiple Links to Increase the Performance of Bandwidth-Intensive UDP-Based Applications},
	journal = {Proceedings of IEEE ISCC 2011},
	volume = {16},
	year = {2011},
	month = {June},
	pages = {1117-1122},
	publisher = {IEEE},
	type = {Conference},
	abstract = {Networked devices often come equipped with multiple network interfaces, and bandwidth aggregation is one of the many possible benefits of using multiple interfaces simultaneously. Real-world networks introduce several challenges that have often been ignored by related work on bandwidth aggregation. The challenges include limited connectivity due to NAT-boxes, link heterogeneity and link variability. In this paper, we present a transparent solution for proxy-based bandwidth aggregation that is able to overcome the different deployment and link heterogeneity challenges present in real-world networks. Our focus has been on increasing the performance of bandwidth-intensive UDP-based applications, and through evaluation we show that our solution efficiently aggregates bandwidth and increases the in-order throughput. Previously, we introduced a multi-link UDP proxy solution that improves in-order throughput. This paper presents a significant extension and improvement in terms of support for middle-boxes (NAT), congestion control, a client-based resequencer and support for all operating systems.},
	isbn = {978-1-4577-0678-3},
	author = {Evensen, Kristian and Kaspar, Dominik and Audun Fosselie {Hansen} and Griwodz, Carsten and Halvorsen, P{\r a}l},
	editor = {Adel S. {Elmaghraby} and Douligeris, Christos}
}
@inproceedings {Simula.ND.379,
	title = {Enhancing Video-on-Demand Playout Over Multiple Heterogeneous Access Networks},
	journal = {Consumer Communications and Networking Conference (CCNC)},
	year = {2010},
	publisher = {IEEE},
	type = {Conference},
	abstract = {Multimedia streaming is increasing in popularity and has become one of the dominating services on the Internet today. Even though user devices are often equipped with multiple network interfaces and in reach of several access networks at the same time, media streams are normally communicated over only one of the available Internet connections. In this paper, we explore the challenges and potential benefits of using multiple access networks simultaneously. Exploiting HTTP{\textquoteright}s capability of handling requests for specific byte ranges of a file, we present the implementation of a lightweight, application-layer, on-demand streaming service that requires no changes to existing servers and infrastructure. Based on real-world experiments with a multihomed host, we investigate the potential performance gains of video-on-demand playout. We achieve a bandwidth aggregation efficiency of 90\% when downloading over 3 heterogeneous access networks in parallel. In addition, we analyze the effect of file segmentation on the buffer requirements and the startup latency.},
	isbn = {978-1-4244-5176-0},
	author = {Kaspar, Dominik and Evensen, Kristian and Paal Einar {Engelstad} and Audun Fosselie {Hansen} and Halvorsen, P{\r a}l and Griwodz, Carsten},
	editor = {IEEE, }
}
@inproceedings {Simula.telco.2,
	title = {Quality-Adaptive Scheduling for Live Streaming Over Multiple Access Networks},
	journal = {The 20th International Workshop on Network and Operating Systems Support for Digital Audio and Video (NOSSDAV 2010)},
	year = {2010},
	month = {June},
	pages = {21-26},
	publisher = {ACM},
	type = {Conference},
	abstract = {Video streaming ranks among the most popular services offered through the Internet today. At the same time, accessing the Internet over public WiFi and 3G networks has become part of our everyday lives. However, streaming video in wireless environments is often subject to frequent periods of rebuffering and characterized by low picture quality. In particular, achieving smooth and quality-adaptive streaming of live video poses a big challenge in mobile scenarios. Building on the observation that the subjective video experience on mobile devices decreases when quality changes are more frequent than every 1 to 2 seconds, we present a client-side scheduler that retrieves segments of several video encodings over heterogeneous network interfaces simultaneously. By extending the DAVVI streaming platform with support for multihoming, the proposed scheduler{\textquoteright}s performance is experimentally evaluated. The results show that our scheduler reduces the video interruptions and achieves a higher and more stable average quality over multiple, truly heterogeneous wireless interfaces.},
	isbn = {978-1-4503-0043-8},
	author = {Evensen, Kristian and Kupka, Tomas and Kaspar, Dominik and Halvorsen, P{\r a}l and Griwodz, Carsten},
	editor = {Dick C. A. {Bulterman}}
}
@inproceedings {Simula.nd.439,
	title = {Using HTTP Pipelining to Improve Progressive Download Over Multiple Heterogeneous Interfaces},
	journal = {International Conference on Communications (ICC)},
	year = {2010},
	pages = {1-5},
	publisher = {IEEE},
	type = {Conference},
	abstract = {Today, mobile devices like laptops and cell phones often come equipped with multiple network interfaces, enabling clients to simultaneously connect to independent access networks. Even though applications, such as multimedia streaming and video-on-demand delivery systems, could potentially benefit greatly from the aggregated bandwidth, implementation and standardization challenges have so far hindered the deployment of multilink solutions. Previously, we have explored the benefits of collaboratively using multiple Internet connections to progressively download and play back large multimedia files. In this paper, we present an improved version of our approach that utilizes HTTP{\textquoteright}s capability of request pipelining in combination with range retrieval requests. While, in our earlier work, the optimal choice of file segmentation size presented a tradeoff between throughput and startup latency, the enhanced solution is able to overcome this tradeoff. The use of very small segments no longer impairs the efficiency of throughput aggregation, which additionally makes our solution robust against link variances and agnostic to network heterogeneity. Read},
	isbn = {978-1-4244-6404-3},
	author = {Kaspar, Dominik and Evensen, Kristian and Paal Einar {Engelstad} and Audun Fosselie {Hansen}},
	editor = {Wilhelm Leuschner {Takawira}}
}
@inproceedings {Simula.ND.307,
	title = {An Analysis of the Heterogeneity and IP Packet Reordering Over Multiple Wireless Networks},
	journal = {IEEE Symposium on Computers and Communications (ISCC)},
	number = {CFP09SCC},
	year = {2009},
	pages = {637-642},
	publisher = {IEEE},
	type = {Conference},
	abstract = {With the increasing deployment of wireless technologies, such as WLAN, HSPA, and WiMAX, it is often the case that simultaneous coverage of several access networks is available to a single user device. In addition, devices are also often equipped with multiple network interfaces. Thus, if we can exploit all available network interfaces at the same time, we can obtain advantages like the aggregation of bandwidth and increased fault tolerance. However, the heterogeneity and dynamics of the links also introduce challenges. Due to different link delays, sending packets of the same flow over multiple heterogeneous paths causes the reordering of packets. In this paper, we quantify how network heterogeneity and the use of multiple links affect IP packet reordering. We show with practical measurements, according to commonly used metrics, that packet reordering over multiple links exceeds the reordering caused by common connections in high-speed, wide-area networks. We also demonstrate the heterogeneity and reordering exceeds the assumptions presented in related work. By using sufficiently large buffers, packet reordering can be avoided. However, for devices with high resource constraints, the workload of using large buffers is expensive. Sender-side solutions of dividing and scheduling a packet sequence to available links towards the client can reduce the buffer requirements. Initial experiments with a static scheduler that has knowledge of average link delay and throughput estimates show that packet reordering can be reduced by only 38\% due to the dynamic heterogeneity of the two links.},
	isbn = {978-1-4244-4671-1},
	author = {Kaspar, Dominik and Evensen, Kristian and Audun Fosselie {Hansen} and Paal Einar {Engelstad} and Halvorsen, P{\r a}l and Griwodz, Carsten}
}
@misc {Simula.ND.373,
	title = {Bandwidth Aggregation Over Heterogeneous Wireless Links},
	howpublished = {Poster, Trilogy Summer School, Louvain-la-Neuve, Belgium},
	year = {2009},
	month = {August},
	abstract = {This is the poster presented at the Trilogy summer school in Louvain-la-Neuve, August 2009. It is a summary of our last 18 months of work on bandwidth aggregation over multiple heterogeneous wireless networks. The 2-page abstract is available here (http://simula.no/research/networks/kristrev-kaspar-simula-trilogy.pdf).},
	author = {Evensen, Kristian and Kaspar, Dominik}
}
@inproceedings {Simula.ND.369,
	title = {A Network-Layer Proxy for Bandwidth Aggregation and Reduction of IP Packet Reordering},
	journal = {The 34rd Annual IEEE Conference on Local Computer Networks (LCN)},
	year = {2009},
	month = {July},
	pages = {585-592},
	publisher = {IEEE},
	type = {Conference},
	abstract = {With today\&$\#$39;s widespread deployment of wireless technologies, it is often the case that a single communication device can select from a variety of access networks. At the same time, there is an ongoing trend towards integration of multiple network interfaces into end-hosts, such as cell phones with HSDPA, Bluetooth and WLAN. By using multiple Internet connections concurrently, network applications can benefit from aggregated bandwidth and increased fault tolerance. However, the heterogeneity of wireless environments introduce challenges with respect to implementation, deployment, and protocol compatibility. Variable link characteristics cause reordering when sending IP packets of the same flow over multiple paths. This paper introduces a multilink proxy that is able to transparently stripe traffic destined for multihomed clients. Operating on the network layer, the proxy uses path monitoring statistics to adapt to changes in throughput and latency. Experimental results obtained from a proof-of-concept implementation verify that our approach is able to fully aggregate the throughput of heterogeneous downlink streams, even if the path characteristics change over time. In addition, our novel method of equalizing delays by buffering packets on the proxy significantly reduces IP packet reordering and the buffer requirements of clients.},
	isbn = {978-1-4244-4488-5},
	doi = {10.1109/LCN.2009.5355198},
	author = {Evensen, Kristian and Kaspar, Dominik and Paal Einar {Engelstad} and Audun Fosselie {Hansen} and Griwodz, Carsten and Halvorsen, P{\r a}l}
}
@techreport {Simula.ND.289,
	title = {Multilink Transfer Over Heterogeneous Networks},
	year = {2008},
	note = {IEEE International Conference on Network Protocols (ICNP), Poster Session},
	publisher = {Simula Research Laboratory},
	abstract = {Multilink transfer is the method of connecting a single host over multiple access networks to the Internet, with the potential of increasing communication quality. However, link heterogeneity causes severe challenges on end-to-end traffic. We explain the problems in more detail and how we intend to solve them using a proxy solution.},
	author = {Kaspar, Dominik and Audun Fosselie {Hansen} and Griwodz, Carsten}
}
@inproceedings {Simula.ND.213,
	title = {A Robust Model-Based Approach to Indoor Positioning Using Signal Strength},
	journal = {IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)},
	year = {2008},
	publisher = {IEEE},
	type = {Conference},
	abstract = {A simple technique to estimate the position of a mobile node inside a building is based on the Received Signal Strength (RSS). In previous publications, we investigated the effectiveness of using circular array antennas and beamforming in order to enable an access point to estimate the position of a mobile inside a building. We also discussed the feasibility of using model-based radio maps to reduce the need for extensive offline measurements. In this paper, a positioning algorithm based on the relative order of the received signal strengths is discussed. This algorithm in conjunction with the ray-tracing propagation model can have promising performance for indoor environments and essentially eliminates the needs for an extensive set of a priori measurement, training or intricate calibration.},
	isbn = {978-1-4244-2643-0},
	author = {Sayrafian-Pour, Kamran and Kaspar, Dominik},
	editor = {Friedel, Paul and Aghvami, Hamid and Dohler, Mischa and Sibille, Alain}
}
@inproceedings {Simula.ND.110,
	title = {The Challenge of Mesh Routing in Ubiquitous Sensor Networks},
	journal = {22nd International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC)},
	year = {2007},
	month = {July},
	publisher = {Institute of Electronics Engineers of Korea},
	type = {Conference},
	abstract = {This informative paper describes the harsh environment in which sensor networks operate, explains challenges of routing in sensor networks and provides an overview of existing multi-hop routing.},
	isbn = {unknown},
	author = {Kaspar, Dominik and Kim, Eunsook and Kim, Hyoungjun}
}
@inproceedings {Simula.ND.108,
	title = {A Novel Model-Based Indoor Positioning Using Signal Strength},
	journal = {18th International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)},
	year = {2007},
	month = {September},
	pages = {1 - 5},
	publisher = {IEEE},
	type = {Conference},
	abstract = {A simple technique to estimate the position of a mobile node inside a building is based on the Received Signal Strength (RSS). In a previous publication, we investigated the feasibility of using circular array antennas and beamforming in order to enable an access point to estimate the position of a mobile inside a building. The approach utilized the two dimensional information (i.e. RSS for various azimuth directions) that is captured in a priori measured radio map. Generating these radio maps is not only extremely labor-intensive and time consuming but also sensitive to changes in the environment and possible source of interference. It would be interesting to find out if a deterministic propagation model such as ray tracing can be used to construct a radio map that effectively replaces the off-line manual measurements. In this paper, we investigate this issue and provide a novel positioning methodology that exhibits acceptable performance without the need for extensive set of measurements in the off-line mode. The performance for various parameters and building model accuracy will be presented and discussed.},
	isbn = {978-1-4244-1144-3},
	author = {Sayrafian-Pour, Kamran and Kaspar, Dominik},
	editor = {IEEE, }
}
@article {Simula.ND.109,
	title = {Application of Beamforming in Wireless Location Estimation},
	journal = {EURASIP Journal on Applied Signal Processing},
	volume = {2006},
	number = {2006},
	year = {2006},
	pages = {13},
	abstract = {A simple technique to estimate the position of a given mobile source inside a building is based on the received signal strength. For this methodology to have a reasonable accuracy, radio visibility of the mobile by at least three access points is required. To reduce the number of the required access points and therefore simplify the underlying coverage design problem, we propose a novel scheme that takes into account the distribution of RF energy around the receiver. In other words, we assume that the receiver is equipped with a circular array antenna with beamforming capability. In this way, the spatial spectrum of the received power can be measured by electronically rotating the main lobe around the 360-degree field of view. This spatial spectrum can be used by a single receiver as a means for estimating the position of the mobile transmitter. In this paper, we investigate the feasibility of this methodology, and show the improvement achieved in the positioning accuracy.},
	author = {Sayrafian-Pour, Kamran and Kaspar, Dominik}
}
@inproceedings {Simula.ND.107,
	title = {Source-Assisted Direction Estimation Inside Buildings},
	journal = {25th IEEE International Conference on Computer Communications (INFOCOM)},
	year = {2006},
	month = {April},
	pages = {1 - 8},
	publisher = {IEEE},
	type = {Conference},
	abstract = {Direction estimation inside buildings is a difficult and challenging task due to severe multipath signal propagation. Numerous algorithms and techniques exist that provide high resolution direction estimation under certain conditions and channel models; however, to our knowledge they all perform poorly at indoor environments. Here, we propose a technique that enables a receiver to achieve greater reliability in estimating source direction through some collaboration with the source. We assume that the receiver and the transmitter are synchronized and they are equipped with circular phased array antennas that have beamforming capability. If the transmitter-receiver pair always steer their main lobes into opposite directions, the spatial spectrum of the received power can be used as a mean for estimating the direction of the transmitting source. In this paper, we investigate the feasibility of this methodology, and show the achieved improvement.},
	isbn = {1-4244-0221-2},
	author = {Sayrafian-Pour, Kamran and Kaspar, Dominik},
	editor = {IEEE, }
}
@mastersthesis {Simula.ND.105,
	title = {Application of Directional Antennas in RF-Based Indoor Localization Systems},
	year = {2005},
	publisher = {Swiss Federal Institute of Technology Zurich (ETH)},
	type = {masters},
	abstract = {A simple technique to estimate the position of a given mobile source inside a building is based on the received signal strength. For this methodology to have a reasonable accuracy, radio visibility of the mobile node by at least three access points is required. To reduce the number of required access points and therefore, to simplify the underlying coverage design problem, a new scheme is presented that takes into account the distribution of RF energy around the receiver. In other words, it is assumed that the receiver is equipped with a circular antenna with beamforming capability. In this way, the spatial spectrum of the received power can be measured by rotating the antenna beam around the 360-degree field of view. This spatial spectrum can be used by the receiver as a means for estimating the position of a mobile transmitter. In this thesis, the feasibility of this methodology is investigated, and the improvement achieved in the positioning accuracy is shown.},
	author = {Kaspar, Dominik}
}
@inproceedings {Simula.ND.106,
	title = {Indoor Positioning Using Spatial Power Spectrum},
	journal = {16th International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)},
	year = {2005},
	pages = {2722 - 2726},
	publisher = {IEEE},
	type = {Conference},
	abstract = {A simple technique to estimate the position of a given mobile source inside a building is based on the received signal strength. For this methodology to have a reasonable accuracy, radio visibility of the mobile by at least three access points is required. To reduce the number of the required access points and therefore, simplify the underlying coverage design problem, we propose a new scheme that takes into account the distribution of RF energy around the receiver. In other words, we assume that the receiver is equipped with a circular antenna with beamforming capability. In this way, the spatial spectrum of the received power can be measured by rotating the antenna beam around the 360-degree field of view. This spatial spectrum can be used by a single receiver as a mean for estimating the position of a mobile transmitter. In this paper, we investigate the feasibility of this methodology, and show the improvement achieved in the positioning accuracy.},
	isbn = {9783800729098},
	author = {Sayrafian-Pour, Kamran and Kaspar, Dominik},
	editor = {IEEE, }
}
