Mika Ylianttila

Handoff in hybrid mobile data networks

With the emergence of a variety of mobile data services with variable coverage, bandwidth, and handoff strategies, and the need for mobile terminals to roam among these networks, handoff in hybrid data networks has attracted tremendous attention. This article presents an overview of issues related to handoff with particular emphasis on hybrid mobile data networks. Issues are logically divided into architectural and handoff decision time algorithms. The handoff architectures in high-speed local coverage IEEE 802.11 wireless LANs, and low-speed wide area coverage CDPD and GPRS mobile data networks are described and compared. A survey of traditional algorithms and an example of an advanced algorithm using neural networks for PTO decision time in homogeneous networks are presented. The HO architectural issues related to hybrid networks are discussed through an example of a hybrid network that employs GPRS and IEEE 802.11. Five architectures for the example hybrid network, based on emulation of GPRS entities within the WLAN, mobile IP, a virtual access point, and a mobility gateway (proxy), are described and compared. The mobility gateway and mobile IP approaches are selected for more detailed discussion. The differences in applying a complex algorithm for HO decision time in a homogeneous and a hybrid network are shown through an example.

Optimization scheme for mobile users performing vertical handoffs between IEEE 802.11 and GPRS/EDGE networks

The next generation wireless networks are characterised by anywhere, anytime connectivity, enhanced data services and higher data rates to enduser. New technologies such as IEEE 802.11 WLAN, Bluetooth, HIPERLAN/2, GPRS/EDGE, cdma2000 and WCDMA aim to achieve this. To facilitate new services, and make them flexible and bandwidth efficient, vertical roaming of mobile nodes is a tempting possibility for operators. Benchmarks and metrics are needed to assess these issues. The need for qualitative and quantitative results for these parameters in a real time situation is critical. One such scenario is the effect on the network performance by means of effective throughput and handoff latency perceived by the mobile user, with increasing number of active users or network load. This paper presents simulation results for mean throughput and handoff delay obtained in vertical handoff and horizontal handoff in IEEE 802.11 and GPRS/EDGE networks. An optimization scheme for mobile users performing vertical handoffs is presented with analysis.

CloudThings: A common architecture for integrating the Internet of Things with Cloud Computing

The Internet of Things presents the user with a novel means of communicating with the Web world through ubiquitous object-enabled networks. Cloud Computing enables a convenient, on demand and scalable network access to a shared pool of configurable computing resources. This paper mainly focuses on a common approach to integrate the Internet of Things (IoT) and Cloud Computing under the name of CloudThings architecture. We review the state of the art for integrating Cloud Computing and the Internet of Things. We examine an IoT-enabled smart home scenario to analyze the IoT application requirements. We also propose the CloudThings architecture, a Cloud-based Internet of Things platform which accommodates CloudThings IaaS, PaaS, and SaaS for accelerating IoT application, development, and management. Moreover, we present our progress in developing the CloudThings architecture, followed by a conclusion.

Security in Software Defined Networks: A Survey

Software defined networking (SDN) decouples the network control and data planes. The network intelligence and state are logically centralized and the underlying network infrastructure is abstracted from applications. SDN enhances network security by means of global visibility of the network state where a conflict can be easily resolved from the logically centralized control plane. Hence, the SDN architecture empowers networks to actively monitor traffic and diagnose threats to facilitates network forensics, security policy alteration, and security service insertion. The separation of the control and data planes, however, opens security challenges, such as man-in-the middle attacks, denial of service (DoS) attacks, and saturation attacks. In this paper, we analyze security threats to application, control, and data planes of SDN. The security platforms that secure each of the planes are described followed by various security approaches for network-wide security in SDN. SDN security is analyzed according to security dimensions of the ITU-T recommendation, as well as, by the costs of security solutions. In a nutshell, this paper highlights the present and future security challenges in SDN and future directions for secure SDN.

Analysis of handoff in a location-aware vertical multi-access network

Integration of WLAN hotspots into next generation cellular networks requires considerations on location management, resource allocation, handoff algorithms and their sensitivity to mobility related features such as velocity of the mobile and the handoff delay. This article presents architecture for seamless location-aware integration of WLAN hotspots into cellular networks and provides an analysis for an optimal handoff decision in moving in and out of a hotspot. For a mobile station, it may be beneficial to know the whereabouts of the hotspots in order to facilitate optimal handoff between the two access networks. In an integrated cellular-WLAN environment, one has to consider location management as part of mobility management due to differences in the cell sizes of the two overlapping technologies. Location information acquired through GPS may be helpful in some cases for advanced location management. In this paper we propose a location-aware architecture to support vertical roaming among heterogeneous wireless access networks. The article includes a description of a preliminary system architecture and the procedures and algorithms needed to implement mobility and location management. In conclusion, a comparison is given of two handoff algorithms (power and dwell-timer based) for moving-in and moving-out transitions, and their sensitivity to mobile velocity and handoff delay.

Comparison of indoor geolocation methods in DSSS and OFDM wireless LAN systems

Geolocation methods for HIPERLAN/2 OFDM systems were reported previously. This paper continues to study the possibility of overlaying geolocation functions in 802.11 DSSS wireless LANs. In this paper, a delay measurement-based TDOA measuring method is proposed for 802.11 wireless LANs, which eliminate the requirement of initial synchronization in the conventional methods. The performance of the potential overlaid geolocation systems for DSSS and OFDM wireless LANs are analyzed and compared in terms of symbol synchronization performance.

Plug-and-play application platform: towards mobile peer-to-peer

While peer-to-peer (P2P) has emerged as a new hot communication concept among the Internet users, mobile usage of P2P applications is still taking its first steps. This article first elaborates the evolutionary process that P2P architectures are going through. Challenges and requirements for mobile P2P are then identified, followed by a definition of a novel Plug-and-Play Application Platform (PnPAP). This platform enables dynamic selections between diverse P2P and session management protocols while preserving the best available network connectivity through Holistic Connectivity (HCon) management. On-the-fly reconfiguration and run-time parameter optimization can be done with a lightweight interpretable state machine. The concept enables flexible and seamless communications for mobile devices in P2P networks.

Indoor geolocation using OFDM signals in HIPERLAN/2 wireless LANs

With the finalization of new series of IEEE 802.11 and ETSI HIPERLAN standards, it becomes very important and interesting to study the methods to integrate geolocation functionalities into the next generation wireless LANs. We investigate geolocation methods and system architectures using OFDM signals in HIPERLAN/2 wireless LANs. We propose a novel method to measure geolocation metrics by exploiting the HIPERLAN/2 MAC frame structure. Computer simulation results are presented to show the performance of the geolocation systems using OFDM signals.

An Overview of Wireless Indoor Geolocation Techniques and Systems

Wireless indoor networks are finding their way into the home and office environments. Also, exploiting location information becomes very popular for both wireless service providers and consumers applications. However, the indoor radio channel causes challenges in extracting accurate location information in indoor environment so that traditional GPS and cellular location systems cannot work properly in indoor areas. This paper provides an overview of the indoor geolocation techniques. After introducing an overall architecture for indoor geolocation systems, technical overview of two indoor geolocation systems are presented. To demonstrate the predicted performance of such systems some simulation results obtained from an indoor geolocation demonstrator are presented.

Performance evaluation of a Kademlia-based communication-oriented P2P system under churn

The phenomenon of churn has a significant effect on the performance of Peer-to-Peer (P2P) networks, especially in mobile environments that are characterized by intermittent connections and unguaranteed network bandwidths. A number of proposals have been put forward to deal with this problem; however, we have so far not seen any thorough analysis to guide the optimal design choices and parameter configurations for structured P2P networks. In this article, we present a performance evaluation of a structured communication-oriented P2P system in the presence of churn. The evaluation is conducted using both simulation models and a real-life prototype implementation. In both evaluation environments, we utilize Kademlia with some modifications as the underlying distributed hash table (DHT) algorithm, and Peer-to-Peer Protocol (P2PP) as the signaling protocol. The results from the simulation models created using Nethawk EAST (a telecommunication simulator software) suggest that, in most situations, a lookup parallelism degree of 3 and resource replication degree of 3 are enough for guaranteeing a high resource lookup success ratio. We also notice that, with the parallel lookup mechanism, a good success ratio is achieved even without the KeepAlive traffic that is used for detecting the aliveness of nodes. A prototype system that works in mobile environment is implemented to evaluate the feasibility of mobile nodes acting as full-fledged peers. The measurements made using the prototype show that, from the viewpoints of CPU load and network traffic load, it is feasible for the mobile nodes to take part in the overlay. Through energy consumption measurements, we draw the conclusion that in general the UMTS access mode consumes slightly more power than the WLAN access mode. Protocol packets with sizes of 200bytes or less are observed to be the most energy efficient in the UMTS access mode.