Maike Kuhnert

Energy-Efficient Handoff Decision Algorithms for CSH-MU Mobility Solution

Vertical handoff (VHO) is the key feature to increase the seamless services availability (i.e., cloud services) in a heterogeneous network environment that especially plays an important role in emergency use cases for reliable information retrieval. For precise handoff decisions, latest proposed vertical handoff decision algorithms (VHDA) are, however, too complex and do not consider the restricted access to decision metrics of mobile phones with limited system resources. For addressing this issue and to benefit earlier from seamless service provisioning, we present feasible client based VHDA solutions ensuring context-aware QoS (i.e., high throughput, low power consumption) for specific use cases. Unlike related approaches, our solutions run completely locally on mobile phones without any required modifications on network side. In terms of performance analysis, we design a comprehensive simulation model for comparing the suggested VHDA solutions with different complexity levels. Moreover, we analyze the impact of an energy model, which is derived from experimental measurements, on handoff decision quality and the improvement of battery usage. Simulation results illustrate that VHDAs with energy model enhance the QoS of handoff decisions in terms of high throughput and low power consumption compared to a less approach.

Performance Evaluation of an Advanced Energy-Aware Client-Based Handover Solution in Heterogeneous LTE and WiFi Networks

The pervasive use of smartphones in daily life and the advanced expansion of cellular networks (LTE) has strongly increased the amount of mobile data traffic and has established the trend of always on connectivity. To cope with the huge amount of data, WiFi offload has become an indispensable solution. Keeping in mind the resource constraints of smartphones, energyaware applications are of high importance. Vertical handover decision algorithms (VHDA) are indispensable for the balance and coordination of heterogeneous networks capacity and the handling of the increased amount of data traffic. In this paper we present an energy metric for vertical handover decision algorithms (VHDA) derived from measurements. Furthermore, we propose a client-based lightweight handover solution with an integrated energy-aware vertical handover decision algorithm based on Fuzzy logic. We analyze the handover delay and the energy consumption in a laboratory as well as in a real environment and compare our results with a RSS based solution. We show that our client-based energy-aware handover solution (EC) fulfills the requirement of small handover delays (≤ 200ms) and outperforms RSS based solutions in terms of energy efficiency (E/Bit).

Performance evaluation of feasible and holistic CSH-MU handoff solution for seamless emergency service provisioning

Seamless service provisioning strongly depends on Vertical HandOff (VHO) as key technology that is especially indispensable for the successful management of emergency operations. Latest mobility solutions, including vertical handoff decision algorithms and executions, are related to high technical and economic costs preventing the immediate introduction of VHO technologies. In order to benefit at an earlier stage from seamless emergency services, we present a holistic cost-effective Client based Secure Handoff for Mobile Units (CSH-MU) solution combined with an energy-efficient Vertical Handoff Decision Algorithm (VHDA) that considers the limited system resources of mobile phones (e.g., restricted access to decision metrics, battery life). For performance evaluation and as proof of concept, we develop a comprehensive simulation model and a real experimental test bed to analyze the gain of our energy-efficient decision algorithm for TCP and UDP based applications. For this purpose, the developed energy model is derived from real measurements based on a mobile phone. Confirmed by the results, using the proposed VHDA with energy model enhances the performance in terms of higher throughput and lower power consumption.

Cloud voice service as over-the-top solution for seamless voice call continuity in a heterogeneous network environment

Abstract Despite the current introduction of the 4G mobile network technology Long Term Evolution (LTE) and the existing heterogeneous network infrastructure, hardly any service provider supports seamless cloud voice service owing to the high integration cost. In order to address this challenging issue, we present a cost-effective Virtual Room based vertical handoff (VOOH) as an Over-the-top (OTT) solution, which is network provider independent and only uses existing wireless access technologies (e.g., LTE, 2G/3G, WiFi) for connectivity purposes. That means no changes in the underlying network technologies are required that result in lower integration effort. Besides providing handoff of ongoing Voice over IP (VoIP) calls seamlessly between WiFi and LTE, unlike related solutions (e.g., Circuit-Switched Fall Back (CSFB)) VOOH presents a cost-effective OTT solution to support voice call continuity between LTE and the circuit-switched channel of 2G/3G networks. In the long term, VOOH also enables data-offloading (e.g., via WiFi) to lower the traffic load of cellular base stations. While our previous work has mainly focused on proof of concepts and experimental performance evaluations, this manuscript proposes a novel analytical and simulation model to analyze the scalability of the VOOH solution that is discussed for specific use case examples. Moreover, the impact of an enhanced VOOH (eVOOH) approach is presented to improve the system performance in terms of blocking probability. Based on the validated models, the results illustrate that eVOOH outperforms the original solution that is shown by lower call blocking probabilities.

Common information space for collaborative emergency management

Interoperability and lacks in communication and information sharing are amongst the most common flaws in nowadays emergency management. The socio-technical concept of a Common Information Space (CIS) enhances interoperability and communication even within an organization. In addition, cloud-based implementations of a CIS offer flexibility and adaptability to existing systems and processes. Even more, this allows the efficient integration of a CIS to existing systems and infrastructures. This paper presents a framework concept for cloud-based Common Information Space for emergency management with special regard to cross country use cases. We will present the SecInCoRe concept of a CIS, that somehow can be called a European version and extension of the Unified Incident Command and Decision Support (UICDS, now XChangeCore).

Cloud voice service for seamless roaming in heterogeneous networks

Todays heterogeneous networks are still in growing progress with the current introduction of Long Term Evolution. Despite the given infrastructure, hardly any service provider offers seamless voice call services due to the high integration cost. For addressing this issue, we introduce a feasible Virtual Room based Vertical Handoff (VOOH) cloud solution that only applies latest existing wireless access technologies (UMTS, LTE, WiFi) for connectivity purposes. Therefore, VOOH does not require any changes in the underlying network layers that result in low integration effort. Moreover, this solution uses the circuit-switched instead of packet-switched channel of UMTS to guarantee QoS for calls while handing over seamlessly from VoIP (via LTE or WiFi) to UMTS. Besides introducing the VOOH concept and its communication procedure, we present an analytical three-dimensional Markov model for performance evaluation that is validated by our developed event-discrete simulation model. Based on this model, a scalable and cost-effective design of VOOH as cloud service for specific use case examples and the obtained findings are discussed. The results presented in this paper illustrate that an enhanced VOOH (eVOOH) solution improves the VOOH performance up to 56% and thus allows to further minimize economic costs.

Seamless Context-Aware Voice Service in the Cloud for Heterogeneous Network Environment

The full coverage of continuous voice cloud services is still an open issue in an overlapping network, particularly with regard to heterogeneously public communication network infrastructures. However, hardly anyone of todays service providers offers seamless voice call continuity across these networks due to the high technical integration effort and economic cost. Given this backdrop, we present a feasible Virtual Room based Vertical Handoff (VOOH) solution. In contrast to its counterparts, VOOH is a network operator independent solution that only uses the todays existing wireless access technologies for connectivity purposes. The advantage of VOOH is that, e.g., mobile service providers can immediately provide advantage of seamless voice cloud service without any modifications in the underlying network layers. Besides illustrating the system architecture, we elaborate the operational details of the proposed solution and also analyze its performance based on real implementation over a public network infrastructure. The experimental results demonstrate that the handoff performance of the VOOH solution is not only competitive, but also less expensive compared to similar approaches. Furthermore, a Markov Chain model has been developed to show the effect of an enhanced VOOH solution on the handoff performance as QoS for different traffic loads.

Cost-Effective and Feasible Handoff Application for Mobile Phones

Heterogeneous networks with different wireless technologies increase the availability of Internet services (i.e., cloud services). However, latest mobile phones with at least two interfaces only access these services either via WiFi or UMTS/HSPA. From users view, an optimal use of heterogeneous networks with todays mobile phones includes seamless data transmission using vertical handoff (VHO) solutions. Caused by high technical and economic costs there exist no usable solutions for readily seamless data transfers. To benefit earlier from seamless service provisioning, we present a feasible client based handoff management solution for mobile phones (CSH-MU) with embedded vertical handoff decision algorithm (VHDA) that considers mobile devices power consumption for WiFi and UMTS communication. As proof of concept and for performance evaluation, a prototype is tested on different mobile phones in a real test bed for TCP and UDP based applications. The results show that the proposed solution is not only a feasible, but also a readily usable solution for mobile phones as well as outperforms network based solutions in terms of handoff delay. A further advantage is the costeffective and immediate integration in current mobile phones without requiring any changes in the used wireless network technologies (e.g., UMTS, WiFi).