Karl-heinz Krempels | RWTH Aachen University (original) (raw)

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Papers by Karl-heinz Krempels

2012 International Conference on Indoor Positioning and Indoor Navigation (IPIN), 2012

ABSTRACT Growing numbers of mobile devices in our daily life and their capability to fulfill chal... more ABSTRACT Growing numbers of mobile devices in our daily life and their capability to fulfill challenging computational tasks raise the question about new application fields beyond well-established tasks. While outdoor navigation became a standard task for many mobile devices, indoor positioning and navigation is still in the research and development stage. Even though complex buildings require aided guidance for visitors, today's mobile hardware is not able to deliver a reliable indoor navigation system. In this paper we describe a novel information system for indoor navigation in complex buildings. Users are guided through the building by using images of the surroundings and textual instructions. We avoid hardware-based user positioning due to its known drawbacks. Instead, users are involved into the navigation process and complete missing information through recognized context and logical constrains of their surroundings. The human navigation process based on recognition of certain unique locations and visual clues is the foundation of this work. The proposed system is universally applicable without restrictions on navigation devices or existing hardware in the building.

Proceedings of the 11th International Conference on Web Information Systems and Technologies, 2015

Proceedings of the 4th International Conference on Smart Cities and Green ICT Systems, 2015

Proceedings of the 4th International Conference on Smart Cities and Green ICT Systems, 2015

ABSTRACT Fostering the usage of alternative mobility modes, e.g., carsharing or carpooling become... more ABSTRACT Fostering the usage of alternative mobility modes, e.g., carsharing or carpooling becomes more and more urgent in modern urban planning. Politicians and city planners have already recognized that putting targeted incentives can influence people’s mobility behavior in an effective way. Agent-based simulations of transportation demand can be a valuable tool to support these planning processes. This work is based on a state-of-the-art transportation demand simulation and shows modeling and simulation modifications related with agents under the influence of incentives. These agents have been assessed in qualitative and quantitative studies prior to the simulation. Results show that agent-based simulation of transportation demand is suitable to evaluate impacts of transportation demand management measures. More specifically, all investigated measures show certain impacts on mobility mode choice, at which an incentive combination is most effective.

Proceedings of the 11th International Conference on Web Information Systems and Technologies, 2015

Wireless Information Networks and Systems, 2008

2008 IEEE International Symposium on Consumer Electronics, 2008

ABSTRACT Existing positioning approaches do not provide the required positioning accuracy for nav... more ABSTRACT Existing positioning approaches do not provide the required positioning accuracy for navigation systems in indoor environments. Novel approaches are based on pseudolites (pseudo satellites) which try to emulate GPS (Global Positioning System) satellites. Thus, conventional GPS receivers could be used, but the infrastructure becomes very expensive. Other approaches are based on tagged WLAN access points or GSM (Global System for Mobile Communication) base stations with a central tag directory. When a user wants to determine its position, he queries the central server for the geo coordinate of its current access point or base station. Finally, the server delivers the corresponding coordinate. In this paper we present a directory-less approach based on broadcasted geo tags for positioning in existing WLAN infrastructures.

2009 6th IEEE Consumer Communications and Networking Conference, 2009

ABSTRACT Current approaches for service discovery in Mobile ad-hoc Networks (MANETs) are optimize... more ABSTRACT Current approaches for service discovery in Mobile ad-hoc Networks (MANETs) are optimized for highly dynamic environments. These approaches do not scale in Wireless Mesh Networks (WMNs) which are intended for long-time usage. Service discovery approaches for static wired networks are also not applicable. We present a scalable two-layered approach for service discovery in WMNs where clients communicate with anycast with the best Service Cache (SC) to register or query for services. SCs do not replicate the client registrations immediately; instead they push their information to all other SCs on-demand only. To avoid severe duplicate information dissemination, appropriate cache replication techniques like backoff and send control mechanisms are presented. Finally, the measurements performed in the department's wireless mesh testbed are discussed with results and conclusions.

2008 1st IFIP Wireless Days, 2008

ABSTRACT In this paper we investigate and evaluate two cross-layer based service discovery protoc... more ABSTRACT In this paper we investigate and evaluate two cross-layer based service discovery protocols for wireless mesh networks. For both protocols we provide a testbed implementation and analyze the feasibility for real world usage. For the class of proactive protocols we encapsulate DNS based service discovery messages in a new message type for the optimized link state routing (OLSR) protocol. For the class of reactive protocols we introduce new message types for the dynamic MANET on demand routing (DYMO) protocol which discovers service and corresponding route in one message. As our results from a testbed show, some modifications have to be made before those protocols are really usable. With our results we deliver optimizations which make those protocols efficient under real conditions.

The 2005 IEEE/WIC/ACM International Conference on Web Intelligence (WI'05), 2005

As Service Descriptions formalisms increase in maturity, significant issues remain regarding how ... more As Service Descriptions formalisms increase in maturity, significant issues remain regarding how the description instances will actually be published, shared and discovered. By way of discussion and description of a prototype Service Description Search service, this paper discusses the distinction between the registry based approaches currently underway for service discovery and more open "publish and search" metaphors used by the current generation web.

Lecture Notes in Computer Science, 2008

This paper proposes a unified architecture for service discovery in Wireless Mesh Networks. In th... more This paper proposes a unified architecture for service discovery in Wireless Mesh Networks. In this architecture, routing clients and non-routing clients, which connect via a mesh gateway with Service Proxy (SP), can also participate seamlessly in the service discovery process. Therefore, the multicast DNS (mDNS) protocol is encapsulated in Optimized Link State Routing (OLSR) messages to make mDNS multi hop

2008 IEEE Wireless Communications and Networking Conference, 2008

The foregoing thesis is hereby approved as a creditable study in the area of Information Technolo... more The foregoing thesis is hereby approved as a creditable study in the area of Information Technology carried out and presented in a manner satisfactory to warrant its acceptance as a pre-requisite to the degree for which it has been submitted. It is understood that by this approval the undersigned do not necessarily endorse or approve any statement made, opinion expressed or conclusion drawn therein but approve the thesis only for the purpose for which it is submitted.

Informatik aktuell, 2009

This paper focuses on the problem of controlling service discovery cache reply storms in Wireless... more This paper focuses on the problem of controlling service discovery cache reply storms in Wireless Mesh Networks (WMNs). A reply storm could occur if the same redundant service reply is sent from multiple nodes where every node uses a different message sequence number. Currently, this problem cannot be detected by existing approaches which inspect only certain header information. To overcome

Mobile devices have obtained a significant role in our life providing a large variety of useful f... more Mobile devices have obtained a significant role in our life providing a large variety of useful functionalities and features. It is desirable to have an automated adaptation of the behavior of a mobile device depending on a change of user context to fulfill expectations towards practical usefulness. To enable mobile devices to adapt their behavior automatically there is a need

Until now navigation aids have primarily focused on outdoor scenarios, whether driving on highway... more Until now navigation aids have primarily focused on outdoor scenarios, whether driving on highways or, more recently, walking through cities. These systems use the Global Positioning System (GPS) for position information. Indoor navigation however cannot rely on GPS data, as the signals do not penetrate building structure. Thus other techniques are required to provide position information indoors. In this article

International Conference on Agents and Artificial Intelligence, 2009

International Conference on Agents and Artificial Intelligence, 2009

2012 International Conference on Indoor Positioning and Indoor Navigation (IPIN), 2012

ABSTRACT Growing numbers of mobile devices in our daily life and their capability to fulfill chal... more ABSTRACT Growing numbers of mobile devices in our daily life and their capability to fulfill challenging computational tasks raise the question about new application fields beyond well-established tasks. While outdoor navigation became a standard task for many mobile devices, indoor positioning and navigation is still in the research and development stage. Even though complex buildings require aided guidance for visitors, today's mobile hardware is not able to deliver a reliable indoor navigation system. In this paper we describe a novel information system for indoor navigation in complex buildings. Users are guided through the building by using images of the surroundings and textual instructions. We avoid hardware-based user positioning due to its known drawbacks. Instead, users are involved into the navigation process and complete missing information through recognized context and logical constrains of their surroundings. The human navigation process based on recognition of certain unique locations and visual clues is the foundation of this work. The proposed system is universally applicable without restrictions on navigation devices or existing hardware in the building.

Proceedings of the 11th International Conference on Web Information Systems and Technologies, 2015

Proceedings of the 4th International Conference on Smart Cities and Green ICT Systems, 2015

Proceedings of the 4th International Conference on Smart Cities and Green ICT Systems, 2015

ABSTRACT Fostering the usage of alternative mobility modes, e.g., carsharing or carpooling become... more ABSTRACT Fostering the usage of alternative mobility modes, e.g., carsharing or carpooling becomes more and more urgent in modern urban planning. Politicians and city planners have already recognized that putting targeted incentives can influence people’s mobility behavior in an effective way. Agent-based simulations of transportation demand can be a valuable tool to support these planning processes. This work is based on a state-of-the-art transportation demand simulation and shows modeling and simulation modifications related with agents under the influence of incentives. These agents have been assessed in qualitative and quantitative studies prior to the simulation. Results show that agent-based simulation of transportation demand is suitable to evaluate impacts of transportation demand management measures. More specifically, all investigated measures show certain impacts on mobility mode choice, at which an incentive combination is most effective.

Proceedings of the 11th International Conference on Web Information Systems and Technologies, 2015

Wireless Information Networks and Systems, 2008

2008 IEEE International Symposium on Consumer Electronics, 2008

ABSTRACT Existing positioning approaches do not provide the required positioning accuracy for nav... more ABSTRACT Existing positioning approaches do not provide the required positioning accuracy for navigation systems in indoor environments. Novel approaches are based on pseudolites (pseudo satellites) which try to emulate GPS (Global Positioning System) satellites. Thus, conventional GPS receivers could be used, but the infrastructure becomes very expensive. Other approaches are based on tagged WLAN access points or GSM (Global System for Mobile Communication) base stations with a central tag directory. When a user wants to determine its position, he queries the central server for the geo coordinate of its current access point or base station. Finally, the server delivers the corresponding coordinate. In this paper we present a directory-less approach based on broadcasted geo tags for positioning in existing WLAN infrastructures.

2009 6th IEEE Consumer Communications and Networking Conference, 2009

ABSTRACT Current approaches for service discovery in Mobile ad-hoc Networks (MANETs) are optimize... more ABSTRACT Current approaches for service discovery in Mobile ad-hoc Networks (MANETs) are optimized for highly dynamic environments. These approaches do not scale in Wireless Mesh Networks (WMNs) which are intended for long-time usage. Service discovery approaches for static wired networks are also not applicable. We present a scalable two-layered approach for service discovery in WMNs where clients communicate with anycast with the best Service Cache (SC) to register or query for services. SCs do not replicate the client registrations immediately; instead they push their information to all other SCs on-demand only. To avoid severe duplicate information dissemination, appropriate cache replication techniques like backoff and send control mechanisms are presented. Finally, the measurements performed in the department's wireless mesh testbed are discussed with results and conclusions.

2008 1st IFIP Wireless Days, 2008

ABSTRACT In this paper we investigate and evaluate two cross-layer based service discovery protoc... more ABSTRACT In this paper we investigate and evaluate two cross-layer based service discovery protocols for wireless mesh networks. For both protocols we provide a testbed implementation and analyze the feasibility for real world usage. For the class of proactive protocols we encapsulate DNS based service discovery messages in a new message type for the optimized link state routing (OLSR) protocol. For the class of reactive protocols we introduce new message types for the dynamic MANET on demand routing (DYMO) protocol which discovers service and corresponding route in one message. As our results from a testbed show, some modifications have to be made before those protocols are really usable. With our results we deliver optimizations which make those protocols efficient under real conditions.

The 2005 IEEE/WIC/ACM International Conference on Web Intelligence (WI'05), 2005

As Service Descriptions formalisms increase in maturity, significant issues remain regarding how ... more As Service Descriptions formalisms increase in maturity, significant issues remain regarding how the description instances will actually be published, shared and discovered. By way of discussion and description of a prototype Service Description Search service, this paper discusses the distinction between the registry based approaches currently underway for service discovery and more open "publish and search" metaphors used by the current generation web.

Lecture Notes in Computer Science, 2008

This paper proposes a unified architecture for service discovery in Wireless Mesh Networks. In th... more This paper proposes a unified architecture for service discovery in Wireless Mesh Networks. In this architecture, routing clients and non-routing clients, which connect via a mesh gateway with Service Proxy (SP), can also participate seamlessly in the service discovery process. Therefore, the multicast DNS (mDNS) protocol is encapsulated in Optimized Link State Routing (OLSR) messages to make mDNS multi hop

2008 IEEE Wireless Communications and Networking Conference, 2008

The foregoing thesis is hereby approved as a creditable study in the area of Information Technolo... more The foregoing thesis is hereby approved as a creditable study in the area of Information Technology carried out and presented in a manner satisfactory to warrant its acceptance as a pre-requisite to the degree for which it has been submitted. It is understood that by this approval the undersigned do not necessarily endorse or approve any statement made, opinion expressed or conclusion drawn therein but approve the thesis only for the purpose for which it is submitted.

Informatik aktuell, 2009

This paper focuses on the problem of controlling service discovery cache reply storms in Wireless... more This paper focuses on the problem of controlling service discovery cache reply storms in Wireless Mesh Networks (WMNs). A reply storm could occur if the same redundant service reply is sent from multiple nodes where every node uses a different message sequence number. Currently, this problem cannot be detected by existing approaches which inspect only certain header information. To overcome

Mobile devices have obtained a significant role in our life providing a large variety of useful f... more Mobile devices have obtained a significant role in our life providing a large variety of useful functionalities and features. It is desirable to have an automated adaptation of the behavior of a mobile device depending on a change of user context to fulfill expectations towards practical usefulness. To enable mobile devices to adapt their behavior automatically there is a need

Until now navigation aids have primarily focused on outdoor scenarios, whether driving on highway... more Until now navigation aids have primarily focused on outdoor scenarios, whether driving on highways or, more recently, walking through cities. These systems use the Global Positioning System (GPS) for position information. Indoor navigation however cannot rely on GPS data, as the signals do not penetrate building structure. Thus other techniques are required to provide position information indoors. In this article

International Conference on Agents and Artificial Intelligence, 2009

International Conference on Agents and Artificial Intelligence, 2009