Vertical handover supporting pervasive computing in future wireless networks

Vertical handovers can transform heterogeneous networks into an integrated communication environment. Such integration can lead to seamless communication if context information is used to support vertical handovers. Seamless communication environments are needed for future pervasive/ubiquitous systems, which are context aware and can adapt to context changes, including network disconnections, changes in network quality of service and changes in user preferences. This paper describes a generic, context-aware handover solution for multimedia applications and illustrates how this handover works for redirection of communication between WLANs and GPRS or UMTS networks. A description of a prototype for WLAN/GPRS handover and the results of handover experiments are also presented.

Pervasive computing is a vision involving future generation computing environmentsnin which information and communication technologies are seamlessly integrated tonsupport diverse aspects of users' lifestyles. Pervasive computing environments willnsee sophisticated sensors, actuators, and monitoring devices embedded into livingnenvironments and interconnected with a variety of computing devices and networkingntechnologies. In the last decade, significant technological advances have led to thenproliferation of new devices, such as handheld computers (e.g., PDAs and mobilenphones), wearable computers and intelligent home and office appliances. Advances innnetworking technologies have also seen a shift from wired to wireless networks andnincreasing availability of wireless access in businesses and academic institutions, asnwell as in public hot spots located in libraries, coffee shops, and other public places.nAt the same time, developments in wireless technologies have equipped devices withnshort range connection capabilities, allowing computing devices and smart appliancesnlocated within close range of one another to form micro networks without any centralnnetwork infrastructure. Current cellular mobile technology is also providing lownspeed data connections and laying the foundations for future mobile networks thatnwill provide multimedia streaming capabilities to mobile devices.n n Together, these emerging technologies are enabling the vision of pervasive computingnto take shape, so that users are provided with the control and flexibility to performntheir computing tasks in a manner that suits their lifestyles and requirements. Sincenpervasive computing environments combine heterogeneous networking and devicentechnologies, pervasive systems are required to adapt to changes in the context innwhich computational applications operate. This adaptation can take various forms,nsuch as adaptation of applications, communication streams, or underlyingncommunication protocols. One possible type of communication protocol adaptation isnvertical handover between different networks (i.e., redirection of applications'ncommunication streams from one network to another).n n Vertical handover permits users to move freely between heterogeneous networks ornchange computing devices while maintaining application continuity. However, currentnvertical handover solutions are not context-aware and are restricted to reactions tondisconnections as users move out of network coverage. Since the vertical handovernmechanism relies on reactions to disconnections, disruption of the communicationnstream always occurs during the handover process, and the QoS requirements of thenapplication are likely to be violated. This is often inappropriate, especially fornmultimedia applications, which have stringent QoS requirements. A better solution fornpervasive systems is to perform vertical handovers in response to a wider set ofncontext changes, which may include (i) prediction of users moving in or out ofnnetwork coverage, (ii) changes in the network, leading to QoS that is unacceptable fornapplications, (iii) movement of users between different computing devices whilencontinuing their applications, or (iv) users entering preferred networks. This thesisnpresents an innovative solution for vertical handovers in pervasive systems that cannsupport all of these types of context-triggered handover.n n The thesis makes a number of significant research contributions. Firstly, it presents ancontext model that defines types of context information and context changes that arenrelevant to vertical handover in pervasive computing environments. Secondly, itndevelops a set of context evaluation and decision rules for triggering vertical handovernand performing stream adaptations to address QoS requirements. Thirdly, it defines angeneric vertical handover protocol and architecture for handover between networks orndevices. It also presents refinements to the generic solution that take into accountnfeatures of particular networking technologies. Fourthly, the thesis illustratesnmechanisms that can be incorporated into the vertical handover solution to counternand minimise QoS violations during changes between networks, in order to minimisenapplication disruption and maximise handover transparency for the user. Finally, as anproof of concept, the thesis presents a prototype that demonstrates the ability of thenproposed vertical handover architecture to support seamless computing, and alsonenables performance evaluation for various types of networking technology.n

Vertical handover management plays an essential role in wireless network technologies, mainly due to the rapid development of various radio access technologies (RATs) that require users to connect seamlessly from one RAT to another. However, in multiple RAT environments, vertical handover management encounters different challenges, including unnecessary handovers, handover failures, ping-pong handovers, and unsuitable access network selection. Essential in vertical handover management is maintaining the desired quality of service (QoS) by the mobile device user. The seamless movement of mobile device users as they run various applications depends on a well-performing vertical handover decision-making algorithm. This bears special significance in a heterogeneous network environment. This paper proposes a vertical handover algorithm that considers user preferences (i.e., a vertical handover algorithm that evaluates the application currently running on a user device). The main objective of the algorithm is to determine when it is necessary to perform the handover, depending on the applications running on the mobile device. The proposed algorithm utilizes a fuzzy logic system to assess whether the handover is necessary and a multiattribute decision-making (MADM) method to select the best available radio access network. A simulation scenario involving different applications at various mobile device velocities was developed. The results proved the algorithm’s effectiveness compared to some of the earlier proposed vertical handover algorithms. At velocities below 10 m/s and 30 m/s, the proposed algorithm had 0% and 15.02% unnecessary handovers, respectively, while the technique for order preference by similarity to ideal solution (TOPSIS) utility’s function-based algorithm obtained 12.38% and 23.24% at the same velocities, respectively. In addition, compared to TOPSIS, the obtained results of the proposed algorithm demonstrated a lower handover failure rate and ping-pong rate for a velocity span of 1–30 m/s for the considered user applications.

The emerging future heterogeneous wireless networks intend to provide a variety of adaptable services to mobile and nomadic users by using integrated heterogeneous network infrastructure. These networks are envisioned as the integration of different existing wireless network technologies such as WLAN, WiMAX, 2G, 2.5G, 3G, Bluetooth, etc., and future wireless network technologies. To integrate different network into a single heterogeneous network, the mobile station/user equipment (MS/UE) must discover all the available radio access networks ahead of time, select the appropriate network from the available radio access networks (RANs) and then seamlessly hand over the session to the desired/chosen network. This research paper presents a novel hybrid approach for network discovery, where the network will broadcast the updated network information using cell broadcast center (CBC) to the MS/UE and the MS/UE may also enquire from the network the additional information regarding the available networks, as opposed to centralized technique used in the existing cellular networks. The proposed solution suggests a network information repository (NIR) embedded in the core network, having the information of all the available radio access networks (RANs) in a specific location. The NIR will be populated and updated by the reporting agents (RAs) which are normal MS/UEs

Today, the number of versatile real-time mobile applications is vast, each requiring different data rate, Quality of Service (QoS) and connection availability requirements. There have been strong demands for pervasive communication with advances in wireless technologies. Real-time applications experience significant performance bottlenecks in heterogeneous networks. A critical time for a real-time application is when a vertical handover is done between different radio access technologies. It requires a lot of signalling causing unwanted interruptions to real-time applications. This work presents a utilization of learning algorithms to give time for applications to prepare itself for vertical handovers in the heterogeneous network environment. A testbed has been implemented, which collects PHY (Physical layer), application level QoS and users context information from a terminal and combines these Key Performance Indicators (KPI) with network planning information in order to anticipate vertical handovers by taking into account the preparation time required by a specific real-time application.

Continuous striving in the development of wireless mobile networks maximizes the possibility of user services and provides experience context rich and personalized services. In this way, for the development towards fully integrated 4G‐all IP network architecture, the interoperability between future generation wireless networks and seamless vertical handover (VHO) has become a crucially important issue. The proposed work is mainly focusing on exploring interoperability issues in heterogeneous networks considering development towards 4G and emphasizing on emerging IEEE 802.21 standard. Further, Simulation results were presented to showcase vertical handover (VHO) performance using IEEE 802.21. Simulation Analysis is done using Network Simulator (NS-2) with seamless mobility package extension.

Handover is an essential process in wireless networks where mobile node changes its access points during the call. Due to heterogeneity in the networks and coexistence of various wireless technologies like wireless fidelity (WiFi), long-term evolution (LTE), wireless interoperability for microwave access (WiMAX), etc., the vertical handover is essential for mobile unit. Vertical handover (VHO) happens to be amongst heterogeneous technologies. Media-independent handover (MIH) is an IEEE 802.21 framework that defines the horizontal and vertical handover process amongst IEEE and non-IEEE standards. MIH suggests an intermediate layer in the technology stack just above physical and media access control (PHY-MAC) layer and greatly relies on PHY-MAC for events and triggers for handover. The handover delays and subsequent packet loss decide quality of service in heterogeneous networks. The various triggers received from PHY-MAC layer rely on hardware/software design of underlying technology. The PHY layer of technologies like WiFi, WiMAX, and LTE relies on orthogonal frequency division multiplexing (OFDM). OFDM is an advanced version of multicarrier modulation system with high spectral efficiency, resistant to inter-symbol interference, high data rate, and less complex in design. In this paper, we propose design of OFDM transreceiver in GNU radio from our future perspective of MIH implementation in software defined radio (SDR) platform like Universal Software Radio Peripheral (USRP).Our design is based on various signal processing blocks and can successfully transfer the text in GNU radio platform.

The question of quality of service in networks of the latest generation is studied. The impact of heterogeneous traffic on the main quality of service indicators reflecting the probability of packet loss and delivery delay over time is evaluated. A model of quality of service in information communication networks has been developed to ensure low traffic delay. Taking into account the concept of quality in information communication networks, the issue of quality of service in networks of the latest generation becomes important from the standpoint of ensuring high reliability and reliability of information transmission, which significantly affects the quality of services provided to the user. This, of course, determines the need to control various parameters of equipment and communication lines, which are determined both by the features of the transmission system and by the parameters of leased channels and tracts. The basis for determining the quality of service, as mentioned above, is the provision of the international concept of quality of service (QoS). According to the requirements of the compliance control model proposed in the concept, the approach to quality indicators is structurally related to the OSI reference model. The main advantages of modern technologies of information communication networks are undoubtedly 5G technologies, which already support such resource-intensive services as massive machine-to-machine communication, ultra-reliable communication and low-latency communication. All of them require high data transfer rates, low millisecond latency, and connectivity of millions of devices. At the same time, it is necessary to ensure a high level of quality of service (QoS), which plays an important role in 5G technologies. The proposed model makes it possible to evaluate not only the quality of service of the combined traffic flow of Internet of Things, tactile Internet, and augmented reality services, but also the delivery delay and the probability of packet loss. The simulation results showed that the parameters of the quality of service of the traffic of the Internet of Things and other modern applications differ significantly during the service of the aggregate flow. When studying the service of aggregated traffic, it was established that the probability of packet loss is higher for it than for Internet of Things traffic. In addition, this difference becomes more significant when the intensity of the incoming load increases.

In the next generation heterogeneous wireless networks, a user with a multi-interface terminal may have network access from different service providers using various technologies. Vertical Handover (VHO) is the capability to switch on-going connections from one Radio Access Network (RAN) to another. This switching is based on the discovered accesses, QoS constraints, operator policies, user preferences and available system capacity and utilization. Optimizing the VHO process is an important issue of research, which leads to reduction of network signaling and mobile device power loss and on the other hand improves network quality of service (QoS) and grade of service (GoS). In this paper, a decision support system is developed to address the VHO problem. This system combines fuzzy logic and TOPSIS, a MCDM algorithm, to the problem of VHO. This combination decreases the influence of the dissimilar, imprecise, and contradictory measurements for the VHO criteria coming from different sources. A performance analysis is done and results are compared with traditional algorithms for VHO. These results demonstrate a significant improvement with our developed algorithm.

Wireless Sensor Networks (WSNs) comprise of groups of tiny sensor nodes that are deployed for collaborative missions such as environmental monitoring, target tracking and surveillance. Due to the miniature size of the nodes, they are typically deployed in large numbers and communicate via multiple hops through a wireless shared communication channel. The successful implementation of such networks is dependent on the enabling technologies (such as digital electronics and wireless communications), as well as the provisioning of Quality of Service (QoS) in the network. While there have been many efforts in QoS provisioning in traditional networks such as the Internet and Mobile Ad Hoc Networks (MANETs), these networks have very different characteristics from that of WSNs. Consequently, the QoS models and protocols that have been designed for the Internet and MANETs cannot be directly applied to WSNs. In this paper, we look at some of the existing QoS mechanisms in the networking literature, and the inherent characteristics of WSNs which make it challenging to provision for QoS in the network. We then identify some key performance metrics for WSN QoS and outline some mechanisms to achieve QoS in the sensor network. Finally, we propose WISER - a framework to enhance QoS in WIreless SEnsoR networks.

In heterogeneous wireless networks (HWNs), it is important to select a currently optimal network for applications demanded by communicating Mobile Nodes (MNs) through Vertical Handover (VHO). VHO problem in HWNs is modeled as a multi-criteria decision making (MCDM) problem. VHO process is very vital in HWNs networks and thus demand the application of very efficient MCDM algorithms. The use of efficient MCDM algorithms for heterogeneous network selection can provide MNs with satisfactory Quality of Service (QoS). We propose a novel MCDM algorithm called MULTIplicative form with Multi-Objective Optimization Ratio Analysis (MULTIMOORA). The performance of the MULTIMOORA is validated by comparing it with SAW, GRA, VIKOR and TOPSIS algorithms for voice, file download and video streaming traffic classes. Simulation results show that MULTIMOORA outperforms SAW, GRA and VIKOR. Moreover, results show it has similar performance with TOPSIS, in term of accuracy for all the network traffics considered.

The heterogeneous environment of cellular networks imposed the need for finding different vertical handover (VHO) mechanisms. VHO algorithms are presented in literature with different input parameters for various services related to different quality of service (QoS) classes (conversational, streaming, interactive and background), such as: cost, available bandwidth (ABW), MT speed, received signal strength (RSS), etc. These parameters are suggested by researchers or experts based on simulation analysis. Furthermore, the concept of identifying the effective parameters for VHO has not been widely studied. For this purpose, we proposed a new approach to extract the effective parameters and their priorities by using data mining (DM). Since voice call service is one of the most sensitive delay services, we collected real log data from servers of two mobile telecom companies in Lebanon, Touch and Alfa for Global System for Mobile Communications (GSM) and Universal Mobile Telecommunications System (UMTS) networks. After preprocessing and discretizing the data, the log file was then summarized and the frequent patterns (FP) were extracted. In this research, two new algorithms were designed. The first, is the Data Summarization Algorithm (DaSA) to summarize the preprocessed data. The second, is the Frequent Pattern Calculation Algorithm (FPCA) to find the frequency of the simultaneous occurrence of the obtained parameters.

Regarding of the problem of visible light communication (VLC) and WiFi heterogeneous network handover, most of the existing work focuses on the research of the vertical handover algorithm of heterogeneous networks, and the coordinated handover of horizontal handover (HHO) and vertical handover (VHO) of heterogeneous networks Strategies are rarely studied. Based on this, this paper proposes a new coordinated vertical handover (CVHO)scheme for heterogeneous networks. This scheme simplifies the motion model of the mobile terminal (MT), and proposes a handover algorithm to realize the coordinated handover of HHO and VHO of the network. The simulation results show that, compared with the traditional immediate vertical handover (IVHO)and dwell vertical handover (DVHO), this handover strategy can better meet the actual movement demands.

Future wireless networks will support the growing demands of heterogeneous services. Dynamic resource allocation is essential to guarantee quality of service (QoS) and enhance the network performance. We propose a novel resource allocation framework to cope with the time-varying channel conditions, co-channel interferences, and different QoS requirements in various kinds of services. We define a QoS measurement for delay sensitive applications. We introduce a credit system, where users have their autonomy to decide when and how to use their resources, and users can borrow or lend resources from the system. We also develop a simple feedback mechanism to report the system with the users' QoS satisfaction levels and channel conditions. Then the system will adapt its resource allocation strategy according to the users' feedbacks to favor the users with the bad QoS satisfaction levels or the good channels. We develop adaptive algorithms at both the user and system levels. From simulations, the proposed algorithms efficiently allocate the resources to different types of users. The users' delay constraints are satisfied and the links can survive under a long period of bad channels.

Mobile terminals have to accomplish vertical handovers among heterogeneous networks for the purpose of realizing seamless roaming and guaranteeing quality of service (QoS). Media Independent Handover (MIH) mechanism defined by IEEE 802.21 standard is a possible approach to this problem. In this paper, we propose a novel user-adaptive vertical handover scheme based on MIH in UMTS, Wi-Fi and WiMAX networks. It follows user-adaptive principles in which a user's QoS demand is taken into consideration in both handover initiation and decision making procedures. We define two kinds of handover triggers caused by unfulfilled QoS requirements or deteriorating wireless channel conditions. Compared with classical Multiple Attribute Decision Making (MADM) methods, a more flexible selection criterion to choose the network providing proper QoS according to a user's need is designed and discussed. The simulation results show that the proposed scheme provides smaller handover times and better QoS than the basic vertical handover scheme.