Joerg Schneider

Access Schemes for Mobile Cloud Computing

Mobile Cloud Computing is widely accepted as a concept that can significantly improve the user experience when accessing mobile services. By removing the limitations of mobile devices with respect to storage and computing capabilities and providing a new level of security by a centralized maintenance of security-critical software for e.g. mobile payment applications, it is expected that it will find broad acceptance on the business as well as consumer side. Research indicates [1] that Mobile Cloud Computing will additionally help to make visions of context services become reality. However, Mobile Cloud Computing concepts rely on an always-on connectivity and will need to provide a scalable and - when requested - quality mobile access. ”Intelligent access” schemes meeting these requirements will be discussed in this paper. They exploit the specific information available by the ”Mobile Cloud Controller”, i.e., theusers’ location, context, and requested services, and significantly evolve the Heterogeneous Access Management schemes developed for the traditional heterogeneous access scenarios. In order to evaluate the performance of these intelligent radio access management concepts in the framework of mobile cloud computing, a specialized radio network simulator will be introduced. It will be shown that a Mobile Cloud Controller establishing a Context Management Architecture can provide the requested availability and quality of mobile connectivity.

A novel approach for combined Joint Call Admission Control and Dynamic Bandwidth Adaptation in heterogeneous wireless networks

Due to the fast evolution of mobile devices, a high penetration of notebooks and smart-phones, and the growing demand for high rate services, e.g. mobile video and P2P services, modern radio access networks require efficient means for call admission control and radio resource management. In particular, network operators, managing co-deployed, heterogeneous access technologies, are interested in an optimized utilization of their infrastructure while maximizing their revenue. For ensuring maximum operator gain and optimized system performance, we propose to handle diverse user service requests, ranging from voice only to bandwidth-consuming streaming services, collaboratively by a combined, heuristic Joint Call Admission Control (JCAC) and Dynamic Bandwidth Adaptation (DBA) approach. This approach aims at maximizing overall system utilization and, hence, the mobile network operators revenues, while keeping the blocking and dropping rates at acceptably low levels, and ensuring that Quality of Service (QoS) demands of the diverse services are met. Therefore, we introduce a novel utility definition of services which is used in the proposed algorithms. It represents a generic measurement of the profit that is gained by the mobile network operator. The JCAC and DBA algorithms are realized tightly coupled and ensure that a maximum number of requested services can be supported by the cooperatively managed, wireless systems in the considered service area. Further, system utilization is optimized by improving the QoS characteristics of the already granted elastic services. In order to evaluate the algorithms for a given scenario of co-deployed Long Term Evolution (LTE) and High Speed Packet Access (HSPA) network nodes, an event-driven simulation platform based on OMNeT++ has been developed, including all relevant entities of 3GPPs SAE. The results show an improvement in the overall gained utility of the mobile network operator compared to standard approaches, and optimized system performance w.r.t. utilization as well as acceptable low blocking and dropping rates.

A concept for context-enhanced heterogeneous access management

The heterogeneity of todays wireless access possibilities imposes challenges for efficient access and resource management across different radio access technologies (RATs). With upcoming 4G technologies and emerging mobile cloud computing, concepts such as fixed mobile convergence are driving the evolution toward comprehensive network management approaches. The proposed context-enhanced heterogeneous access management (HAM) concept accounts for network, terminal, and user context while simultaneously trying to accommodate users, facing different environmental conditions, with the best possible end-to-end performance. To quantify the potential benefit of incorporating context information, we present preliminary simulation results demonstrating that context-enhanced HAM systems will clearly outperform conventional systems.

Exploiting user and network context for intelligent radio network access

The availability of both static and dynamic context information has steadily been increasing in recent years. Accordingly, manifold use cases for this data, especially for consumer services, have been suggested. In this paper, we present a concept for how to use context information for intelligent radio network access (IRNA) purposes. Therefore, a context management architecture (CMA) is proposed that is able to handle context information and its respective providers and consumers efficiently. Since a Heterogeneous Access Management (HAM) imposes high requirements on context quality, especially with respect to availability, accuracy, delay, confidence, and relevance of context data, a context quality enabler (CQE) is integrated into the CMA. Finally, we describe the concept of a context-aware radio network simulator (CORAS) that models IRNA concepts, thus allowing for quantitatively evaluating the impact of user and network context information on simulation results.

A distributed broker system enabling coordinated access schemes in autonomous wireless networks

Autonomous wireless networks play an increasingly crucial role in todays society. Harsh environmental conditions, challenging deployment topologies, unreliable (or non-existing) power grids, as well as misguided control procedures of communications infrastructures by governmental authorities have made autonomous communication infrastructures a valuable asset for long-term development and wealth of societies. However, such wireless networks are in an early phase of their development and need to incorporate necessary equipment and algorithms for autonomous operation. This paper presents a concept and a concrete simulation scenario showing how a distributed context management system and the data collected and distributed by such a system can improve the performance of an autonomous, coordinated wireless mesh network (ACWMN). Research agrees that it is context awareness that will transform todays networks to incorporate autonomous, coordinated behavior. We further depict a concrete example simulation scenario where the access capacity of an ACWMN with WLAN radio access technology is significantly increased by coordinating user access with upper limits on the number of users that can concurrently request data services.

A concept for context-aware multihoming with heterogeneous radio access technologies

There are several radio access technologies providing connectivity for mobile devices. In the future, more and more mobile devices will be capable of supporting more than one access technology. For being able to use these technologies simultaneously, there is a need for multihoming capabilities. Due to the variety of access technologies and the ability to use them simultaneously, new concepts for managing multihoming are needed. Higher requirements on efficiency and user satisfaction put new challenges on decision processes for multihoming. These higher requirements can be met by incorporating context information in the decision process. To enable context-based decisions, there is the need for determining, acquiring, and managing the required context information as well as the need for a decision scheme facilitating this information.

Efficient Spectrum Sharing in Heterogeneous Wireless Environments

Abstract Today, spectrum is scarce because of the growing number of wireless devices and the steadily increasing demand for high data rates. Streaming and online gaming are a new kind of challenge for wireless networks in terms of delay and throughput. Systems like LTE enable high data-rates (100 MBit/s and above) combined with a low latency. Despite of all these new transmission technologies a major bottleneck is caused by the available spectrum. Furthermore this problem gets exacerbated by a static frequency assignment. To overcome this bottleneck new concepts for adaptive spectrum assignment with respect to load situation need to be developed. In this article we describe and evaluate an architecture which is able to handle different kinds of spectrum sharing techniques. Furthermore, our approach is able to deal with short time sharing (up to one minute). Therefore, we developed a Spectrum Management System (SMS) which is based on a hierarchical organized distributed hash table (DHT) architecture. Additionally, our system deploys databases for additional information like spectrum usage rules, incumbents or network coverage information (described by polygons). To enable the handling of time-critical spectrum data, we introduce a time synchronisation protocol named Lightweight Time Synchronisation (LT-Sync) which considers the system architecture and estimates transmission delays.

From context to context-awareness: model-based user classification for efficient multicasting

Engineering context-aware wireless networks capable of selfconfiguration, self-optimization, and self-healing requires a broad information base as well as sophisticated reasoning models for user and network behavior as well as for environmental conditions. The rise of smartphones and smart spaces has tremendously increased the availability of context information such as location, environmental conditions (temperature, light), or terminal capabilities. Moreover, the popularity of social networks has complemented these data with profile information about individual users. This paper outlines how available information enables self-optimization in wireless networks by designing according models. The chosen application scenario, classifying and grouping users and thus facilitating group-based multicasting, demonstrates the feasibility and the effectiveness of the described approach.