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Analysis of handoff in a location-aware vertical multi-access network
Abstract
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.
... The heterogeneous characteristics of the radios, in combination with an intelligent decision maker for interface selection, makes it possible to complement the limitations of each type of networks, improving flexibility and reliability of wireless communications. While some recent works have successfully proved the effectiveness of hybrid networking in vehicle-to-infrastructure (V2I) communications [10], [11], [12], [13], few of them have shed light on its potential for V2V communications. Vehicles may select one of the available radios to broadcast their data packets [14], or may send duplicated packets over multiple types of radios to ensure reliable packet delivery [15]. ...
... The high mobility of vehicles poses a unique challenge in handoff decisions, as network conditions around vehicles can change in a short period of time. Ylianttila et al. [10] design a location-based vertical handoff mechanism, integrating cellular and Wi-Fi networks. They employ precise vehicle positions, obtained by GPS, to detect the events that a vehicle entering a coverage area of a Wi-Fi access point. ...
... We can see that the distributed decision maker frequently causes large packet delivery delays. While it tries to balance the network load by probabilistically selecting the radio to use as in Eq. (10), the lack of global information on channel conditions and resource demands frequently makes the decision less optimal, leading the network traffic to concentrate on either of the radios. The centralized decision maker solves this problem by global optimization of the use of radio resources, with 96.6% of the data packets being delivered within 100 ms. ...
The emergence of new types of applications for connected cars is expected to increase data traffic in vehicular networks. A promising solution is to concurrently use multiple types of radios, dynamically selecting network interface(s) that are likely to achieve the highest performance (i.e., hybrid networking). In this paper, we propose an intelligent interface selection mechanism, tailored to hybrid vehicle-to-vehicle communications. We introduce a novel approach of hierarchical decision making, in which interface selection by vehicles is loosely controlled by a remote central server. The server provides vehicles with recommended interface selection strategy, which is optimized based on the statistical knowledge about road and network conditions. While the vehicles basically follow the recommended strategy, they are allowed to adjust it if they detect actual channel conditions deviating from the statistics on the server. The adjustments are carefully made based on the expected channel load information provided by the server, so that the changes of strategy do not harm the communication performance in neighboring geographical regions. Simulation results show that our solution can significantly reduce the end-to-end latency of packet delivery, compared to conventional selection mechanisms.
... Handover algorithm play important role in this task of optimum network selection. Several approaches such as Genetic algorithms, Fuzzy logic, Utility function and Multiple attribute decision making algorithms have been developed and suggested by researchers to provide ubiquitous access to user by means of vertical handover [4][5][6][7][8][10][11]. Among all the approaches, multiple attribute decision making algorithms are able to accumulate large number of context related attributes in network selection. ...
... Moreover location of mobile user play vital role in performing optimum handover among different networks. M. Ylianttila et.al [6] proposed a location aware architecture to support vertical roaming between WLAN hotspots and cellular networks. Power and dwell-timer based two handoff algorithms were used for moving-in and moving-out transitions between two networks. ...
... In this paper, handoff call dropping and call blocking, number handoffs where not addressed. Paper [13] explains that crosslayer solutions are mainly proposed for handoff management. It aims to achieve layer 3 handoff with help of layer 2. Layer 2 reports the signal strength and movement detection information in advance, the system can make better preparation for the network layer handoff so that the packet loss is eliminated and the handoff latency is reduced. ...
... User defined policies are used to decide the most suitable network to satisfy the user"s expectations. In [13], location information is used to perform transition analysis in deciding handoffs. None of these approaches define a complete cross-layer platform for mobility management. ...
Emerging wireless communication technology focuses the development to provide the communication support for mobile devices based on the user demand and network connectivity for high-speed data transfer like multimedia, video and Voice over IP(VoIP). In wireless network the main issue to be addressed is channel allocation and network connectivity. Because of the limited bandwidth resources, it is necessary to provide an efficient solution for bandwidth allocation to increase number of users. Maintaining the network connectivity improves the user satisfaction. Because of the mobility of user and continuous changes in network characteristics like bandwidth, error rate, delay and jitter assigning the "best" network channel is a challenging issue. Handover process has been done to maintain the connectivity. During handover choosing the best network with the QoS guarantee based on the user requirements and service type is the current research topic. Several works is going on in this area. Still there is no standard and efficient method implemented in real world. This paper proposes a frame work to make decision to choose the best network while handoff is triggered.
... 1) Dwell timer based Schemes: Authors in [37] and [39] present an architecture that suggests to use location and crosslayer information to trigger vertical handovers. They compared two handover algorithms from the perspective of how the difference in the effective data rates, the terminal velocity and the amount of handover delay affects the mean throughput in a region, both in moving-in and moving-out scenarios. ...
... Becvar et al. [46] propose a handover mechanism to maximize the handover prediction efficiency using the parameter of RSSI with hysteresis as in [39] and [45]. They have defined two thresholds for this parameter in order to exploit the best use of it. ...
Wireless networks are passing through a transition phase for the past few years now and this transition is giving a way towards the convergence of all IP-based networks to form the Next Generation Networks (NGNs). With the proliferation of these networks in daily life, users’ needs are also increasing and service operators are offering different services to satisfy their
customers for a better grade of service and an elevated quality of experience (QoE). However, a single operator cannot fulfill the huge demands of the users especially, if a user is nomadic. In nomadism, a user traverses number of available networks that might contain cellular or wireless data networks, usually known as heterogeneous wireless networks. These networks offer various services from email to live video streaming depending upon their capacity and nature. During this traversing procedure, a user switches among different networks to satisfy his/her needs in terms of quality of service. This process is commonly known as a vertical handover or handoff (VHO) due to the involvement of heterogeneous wireless networks in it. An extensive work has been carried out in this field in order to fulfill user demands for better QoS and QoE. In this paper, we give a detailed state-of-the- art of these existing vertical handover decision mechanisms that aim at providing ubiquitous connectivity to the mobile
users. We have categorized these vertical handover measurement and decision schemes on the basis of their employed techniques and parameters. Also, we present a comprehensive summary of their advantages and drawbacks. This paper gives its readers an overview of the active research initiatives in the area of handover decision making process in heterogeneous wireless networks and identifies the challenges behind the seamless services provisioning
during mobility.
... Therefore, selecting a target node with a V2V link with higher reliability is also an important problem that needs to be solved. Networked vehicles can obtain the position information of each vehicle in the network through GPS positioning system [21]. The moving speed and heading information of each vehicle can also be acquired by using sensors [22](for instance, speed sensor, acceleration sensor, etc.) equipped with the vehicle. ...
Abstract In the Internet of Vehicles (IoV), with the increasing demand for intelligent technologies such as driverless driving, more and more in-vehicle applications have been put into autonomous driving. For the computationally intensive task, the vehicle self-organizing network uses other high-performance nodes in the vehicle driving environment to hand over tasks to these nodes for execution. In this way, the computational load of the cloud alleviated. However, due to the unreliability of the communication link and the dynamic changes of the vehicle environment, lengthy task completion time may lead to the increase of task failure rate. Although the flooding algorithm can improve the success rate of task completion, the offloading expend will be large. Aiming at this problem, we design the partial flooding algorithm, which is a comprehensive evaluation method based on system reliability in the vehicle computing environment without infrastructure. Using V2V link to select some nodes with better performance for partial flooding offloading to reduce the task complete time, improve system reliability and cut down the impact of vehicle mobility on offloading. The results show that the proposed offloading strategy can not only improve the utilization of computing resources, but also promote the offloading performance of the system.
... The location-based HO-decision algorithm for dierent small cell networks is discussed in [64,65,72,73,75,76]. As described earlier, [64] and [65] keep the mobilityhistory of users to predict the target cell in small cell networks. ...
... In the following, we present a review of these related works. Ylianttila et al. [10] demonstrated the need for an adaptive dwell timer that can respond to variations in system conditions. In addition, they suggested that such a timer should have a finite value. ...
Abstract The coexistence of visible light communication (VLC) and WiFi elevates indoor wireless communications beyond 4G, by utilizing VLC for high-rate transmission and ensuring reliable mobile connectivity through WiFi. Nevertheless, the high susceptibility of VLC-line-of-sight (VLC-LoS) channel to blocking can result in excessive number of handovers between VLC and WiFi networks leading to huge signaling cost and degradation in overall system performance. Therefore, an efficient inter-system handover scheme is required for a successful integration of the two access technologies. To this end, a channel adaptive dwell vertical handover (CAD-VHO) scheme is presented, in this article, as an improvement on static D-VHO scheme. The width of the dwell timer employed in our scheme is altered based on the rate of blocking and recovery of VLC-LoS channel. As a result, the proposed CAD-VHO scheme is adaptive to the rate and extent of obstruction of VLC-LoS link due to user mobility and surrounding objects. Simulation scenario was set up as a dynamic network environment in an indoor setting with restless and stationary mobile terminals and surrounding mobile object. Based on the simulation results obtained, the CAD-VHO scheme can reduce the number of VHOs by as much as 80% whiles achieving a higher average data rate in most cases. Consequently, the proposed CAD-VHO scheme is highly efficient in minimizing VHO signaling cost and enabling a superior broadband service.
... Yalliantila et al. [45]. have presented a solution that uses GPS location and cross-layer information to decide vertical handovers. ...
Vehicular ad hoc networks represent one of the most important applications of wireless ad hoc networks. In highways, where different networks exist, frequent and sometimes unnecessary switches from one network to another may occur, which degrade network performance and affect applications, especially those that require high quality networks such as multimedia applications (Video conferencing, Video On-Demand, etc.). This work presents an analytical model and a Vertical Handover decision method for Highways called VHH. It is based on position, velocity, jitter, and density as mandatory inputs which aim to both minimize Vertical handover frequency and avoid unnecessary handoffs and ping pong effect between different networks, in the goal of enhancing multimedia streaming services in highways. A simulation is provided to prove the performance of the algorithm.
... Information on geolocation could also be used to improve the process of decision-making for handover across heterogeneous networks. The study by Ylianttila et al. [17] established the first method of utilizing the GPS to manage the mobile device's present location. The proposal in this study took into consideration the scenario of the handover under the WiFi as well as the UMTS cells. ...
Seamless mobility is a challenging issue in the area of research of vehicular networks that are supportive of various applications dealing with the intelligent transportation system (ITS). The conventional mobility management plans for the Internet and the mobile ad hoc network (MANET) is unable to address the needs of the vehicular network and there is severe performance degradation because of the vehicular networks’ unique characters such as high mobility. Thus, vehicular networks require seamless mobility designs that especially developed for them. This research provides an intelligent algorithm in providing seamless mobility using the media independent handover, MIH (IEEE 802.21), over heterogeneous networks with different access technologies such as Worldwide Interoperability for Microwave Access (WiMAX), Wireless Fidelity (Wi-Fi), as well as the Universal Mobile Telecommunications System (UMTS) for improving the quality of service (QoS) of the mobile services in the vehicular networks. The proposed algorithm is a hybrid model which merges the biogeography-based optimization or BBO with the Markov chain. The findings of this research show that our method within the given scenario can meet the requirements of the application as well as the preferences of the users.
... The main objective of vertical handover is to preserve connectivity, maintain QoS, and limit the number of unnecessary vertical handovers. Several metrics used by researchers to trigger handover decisions are: Received Signal Strength (RSS) [220], Signal-to-Noise and Interference Ratio (SINR) [221], location [222] and QoS guarantees [223]. Whether the traditional approach can be applied in the vehicular network or not, and how to imple- ...
... Moreover location of mobile user play vital role in performing optimum handover among different networks. M. Ylianttila et.al [11] proposed a location aware architecture to support vertical roaming between WLAN hotspots and cellular networks. Power and dwell-timer based two handoff algorithms were used for moving-in and moving-out transitions between two networks. ...
Movement of mobile terminal in overlapping areas of different wireless communication networks require seamless handover for service continuation. Moreover quality of service (QoS) offered by wireless networks must match with the application requirements of user. Multiple attributes decision making (MADM) based handover algorithms are able to suggest optimum network among the available networks with requisite services. Context attributes of available networks varies dynamically with the movement of user and this necessitate the inclusion of location updates of user. In this paper movement aware handover algorithm has been designed with vector normalized preferred performance based VIKOR method (MV-VPP). Four simulation scenarios have been designed to analyze the performance of MV-VPP in four traffic classes. The simulation results show that proposed method is effective for application based network selection in heterogeneous environment.
... A number of network integration proposals are found in literature. These are classified according to the level of coupling between the networks [4,6,9,[11][12][13][14][15] ...
This paper presents a brief study on issues associated with network integration between wireless LAN (WLAN) and Universal Mobile Telecommunications System (UMTS) networks. Network integration of WLAN and UMTS networks is an area that requires continuous research attention. It gives service providers the opportunity to offer additional services such as " always on service " on their heterogeneous networks for the benefit of their subscribers and for overall Quality of service improvement of the networks. Since heterogeneous networks are involved, vertical handoff (VHO) has an important role to play in achieving seamless data mobility in the next generation networks. Issues and problems of VHO have to be adequately studied and addressed if both the service providers and their subscribers should get satisfactory results such integrations. In this paper therefore, we presented an overview study of handoff management in mobile communication networks, vertical handoff requirements and the different types of network integration. Our study shows that loosely-coupled architecture of network integration far outweighs that of the tightly-coupled architecture of network integration except under a critical and specified conditions. We therefore proposed that loosely-coupled architecture should always be considered first for network integrations where ever possible. It is hoped that critical issues of loosely-coupled architecture such as network Quality of service, security, and latency will be addressed in future works.
... The location-based HO-decision algorithm for different small cell networks is discussed in [22], [23], [31], [32], [34], [35]. As described earlier, [22] and [23] keep the mobilityhistory of users to predict the target cell in small cell networks. ...
... In Received Signal Strength Indicator (RSSI)-based prediction algorithms, RSSI of the current attachment point is compared to the RSSI of the other available networks for the prediction of handover. Becvar et al. [2] suggest a handover mechanism to maximize the handover prediction efficiency using the parameter of the (RSSI) [17,18]. The authors have described two thresholds for RSSI for optimal use. ...
This study aims to design a vertical handover prediction method to minimize unnecessary handovers for a mobile node (MN) during the vertical handover process. This relies on a novel method for the prediction of a received signal strength indicator (RSSI) referred to as IRBF-FFA, which is designed by utilizing the imperialist competition algorithm (ICA) to train the radial basis function (RBF), and by hybridizing with the firefly algorithm (FFA) to predict the optimal solution. The prediction accuracy of the proposed IRBF-FFA model was validated by comparing it to support vector machines (SVMs) and multilayer perceptron (MLP) models. In order to assess the model's performance, we measured the coefficient of determination (R2), correlation coefficient (r), root mean square error (RMSE) and mean absolute percentage error (MAPE). The achieved results indicate that the IRBF-FFA model provides more precise predictions compared to different ANNs, namely, support vector machines (SVMs) and multilayer perceptron (MLP). The performance of the proposed model is analyzed through simulated and real-time RSSI measurements. The results also suggest that the IRBF-FFA model can be applied as an efficient technique for the accurate prediction of vertical handover.
... In fact, Mobility Management in Cellular IP is based on the two states that the mobile host can take: idle or active; and for the idle state, the Location Management strategy used is a combination between the classical scheme (triggering updates when the borders of predetermined sets of cells are crossed) and the timer-based method. Regarding multi-access networks, reference [13] presents an analytical study of Mobility Management focusing on the importance of the dwell-timer parameter, whose optimal value is shown to depend on the particular scenario and parameters accounting for the user's mobility (e.g. velocity). ...
In this article, we examine the Location Management costs in mobile communication networks utilizing the timer-based method. From the study of the probabilities that a mobile terminal changes a number of Location Areas between two calls, we identify a threshold value of 0.7 for the Call-to-Mobility Ratio (CMR) below which the application of the timer-based method is most appropriate. We characterize the valley appearing in the evolution of the costs with the timeout period, showing that the time interval required to reach 90% of the stabilized costs grows with the mobility index, the paging cost per Location Area and the movement dimension, in opposition to the behavior presented by the time interval that achieves the minimum of the costs. The results obtained for CMRs below the suggested 0.7 threshold show that the valley appearing in the costs tends to disappear for CMRs within [0.001, 0.7] in onedimensional movements and within [0.2, 0.7] in two-dimensional ones, and when the normalized paging cost per Location Area is below 0.3.
... This model takes into consideration updated database maintained by the mobile agents. The network topology parameter plays major role in the analysis because it gives the mobility patterns of a MN. Figure 6 shows that MPS decreases handoff blocking rate in comparison to [20], classic scheme [22] and cost-based scheme [21]. In simulation it is assumed that 64 MNs are working simultaneously. ...
Growing consumer demands for access of communication services in a ubiquitous environment is a driving force behind the development of new technologies. The rapid development in communication technology permits the end users to access heterogeneous wireless networks to utilize the swerve range of data rate service “anywhere any time”. These forces to technology developers to integrate different wireless access technologies which is known as fourth generation (4G). It is become possible to reduce the size of mobile nodes (MNs) with manifold network interfaces and development in IP-based applications. 4G mobile/wireless computing and communication heterogeneous environment consist of various access technologies that differ in bandwidth, network conditions, service type, latency and cost. A major challenge of the 4G wireless network is seamless vertical handoff across the heterogeneous wireless access network as the users are roaming in the heterogeneous wireless network environment. Today communication devices are portable and equipped with manifold interfaces and are capable to roam seamlessly among the various access technology networks for maintaining the network connectivity, since no single-interface technology provides ubiquitous coverage and quality-of-service (QoS). This paper reports a mobile agent based heterogeneous wireless network management system. In this system agent’s decision focuses on multi parameter system (MPS). This system works on the parameters- network delay, received signal strength, network latency and study of the collected information about adjoining network cells viz., accessible channel. System is simulated and a comparative study is also made. From results it is observed that system improves the performance of wireless network.
... Although there are many existing VHO decision making processes have been proposed in the literature to reduce www.conference.thesai.org handover connection failure [37][38][39][40][41][42][43][44] and which have been surveyed in [36], the session rejection as handover connection failure factor has not been considered. ...
One challenge of wireless networks integration is to provide ubiquitous wireless access abilities and seamless handover for mobile communication devices between different types of technologies (3GPP and non-3GPP) such as Wireless Fidelity (Wi-Fi), Worldwide Interoperability for Microwave Access (WiMAX), Universal Mobile Telecommunications System (UMTS) and Long Term Evolution (LTE). This challenge is critical as Mobile Users (MUs) are becoming increasingly demanding for improved services regardless of the technological complexities associated with them. To fulfill these requirements for seamless Vertical Handover (VHO) two main interworking frameworks were proposed by IEEE Group and 3GPP for integration between the aforementioned technologies; namely, Media Independent Handover IEEE 802.21 (MIH) and IP Multimedia Subsystem (IMS), where each of them requires mobility management protocol to complement its work such as Mobile IP (MIP) and Session Initiation Protocol (SIP), respectively. In this paper, we overview these frameworks and show their components, benefits and drawbacks. Then we present our Imperative Alternative MIH for Vertical Handover (I AM 4 VHO) algorithm based on MIH framework and using fuzzy logic to provide low connection failure (probability of session rejection) and low signaling cost for enhancing VHO in heterogeneous wireless networks environment. Simulation based performance evaluation shows that the proposed algorithm reduces the probability of VHO connection failure by up to 75%.
... Geolocation information can also be applied to improve the decisionmaking process to hand over among heterogeneous networks. Ylianttila et al. [8] presented one of the first approaches, using GPS to manage the current location of the mobile device. Their proposal considered the handover scenario under Wi-Fi and UMTS cells. ...
End-users increasingly expect ubiquitous connec-tivity while on the move. With a variety of wireless access technologies available, we expect to always be connected to the technology that best matches our performance goals and price points. Meanwhile, sophisticated on-board units enable geolocation and complex computation in support of handover. In this paper, we present an overview of vertical handover techniques, and propose an algorithm empowered by the IEEE 802.21 standard, that considers the particularities of the vehicular networks, the surrounding context, the application requirements, the user preferences, and the different available wireless networks (i.e., Wi-Fi, WiMAX and UMTS) in order to improve users' quality of experience. Our results demonstrate that our approach, under the considered scenario, is able to meet application requirements while ensuring user preferences are also met.
... One such solution has been proposed by Ylianttila et al. [6]. The authors have defined a "transition region" as the area where the signal varies around a predefined threshold. ...
Users of next generation wireless devices will be likely to move across a heterogeneous network environment. Thiswill give them the possibility to always exploit the best connection to the global Internet. In order to keep a seamless connection, the handover between different access technologies, also known as vertical handover, must be as smooth as possible. The current evolution of network architectures toward an all-IP core favours the use of the Mobile IPv6 protocol to handle such handovers. However, this protocol still presents several drawbacks, mainly related to the assumption of static devices and wired connections. Hence we have designed and implemented a software module that exploits information from the lower layers (e.g. physical) to extend the capabilities of Mobile IPv6 to wireless environments. We have then evaluated both the plain Mobile IPv6 and our proposed implementation over an experimental testbed. The outcome of the assessment proves the effectiveness of our solution and reveals the possibility to perform a seamless vertical handover in heterogeneous wireless networks.
... There has been research on various aspects of mobile connectivity management. Vertical handoff, i.e., the act of roaming between heterogeneous radio networks, has been one subject of optimization in recent studies [1] [2]. Another important area of study is the optimal selection of the physical connectivity to use at a given time. ...
Selection of optimal network connectivity in mobile telecommunications is an important field of study. There are more parameters to consider than mere selection of physical connectivities. For optimal vertical connectivity selections, a cross-layer approach is needed. This paper presents a formulation for the Holistic Connectivity framework, which, when applied in a mobile middleware solution, enables seamless top-down connectivity management in mobile consumer products. The solution has emphasis on peer-to-peer networking. Connectivity policy management extends the context-aware connectivity management framework developed earlier at the University of Oulu, Finland. Technical and functional scenarios for the proposed framework are discussed, and preliminary experimental results with realtime traffic are provided for supporting further design and requirement specification.
... Recently, works considering GPS support for the decision-making process when performing VHO among multiple access technologies were presented. Ylianttila et al. [5] proposed using the GPS in order to manage the current location of the mobile device to hand over among Wi-Fi and UMTS cells, performing the decision-making based on the Received Signal Strength (RSS). ...
Nowadays automotive industry is taking advantage of the latest developments offering On-Board Units, which are powered by advanced processors, GPS devices, sensors, and multiple wireless access technologies such as Wi-Fi, WiMAX and UMTS. Users within vehicular networks will be able to access content from the Internet at high speeds while moving from one place to another, switching among multiple access points with heterogeneous coverage areas, as well as with different QoS levels offered. To maintain data connections alive in such dynamic conditions, Vertical Handover techniques are required. In this paper we present a Vertical Handover Decision Algorithm designed for dynamic environments. The decision making process is optimized by combining networking information, obtained by the services of the IEEE 802.21 standard, with geolocation, map information, surround context information and route calculation, thereby improving the handovers' performance.
... As for a potential integration architecture for WLAN and 3G WWAN, the authors of [5] describe a loosely coupled architecture in the form of an IEEE 802.11 gateway and a corresponding service access client software. Most recently, a global-positioning-system-(GPS) based location-aware vertical handover scheme is introduced in [6], while in [7], an architecture of a vertical handover scheme based on the paging channel (PCH) of cellular networks is proposed. ...
One of the most impending requirements to support a seamless communication environment in heterogeneous wireless networks comes from the limited power supply of small-size and low-cost mobile terminals as in stand-alone WLANs or cellular networks. Thus, it is a challenge to design new techniques so that mobile terminals are able to not only maintain their active connection as they move across different types of wireless networks, but also minimize their power consumption. There have been several efforts aimed at having mobile devices equipped with multiple interfaces connect optimally to the access network that minimizes their power consumption. However, a study of existing schemes for WLAN notes that in the idle state, a device with both a WLAN and a WWAN interface needs to keep both interfaces on in order to receive periodic beacon messages from the access point (AP: WLAN) and downlink control information from the base station (WWAN), resulting in significant power consumption. Therefore, in this paper, we propose a power-efficient communication protocol (PCP) that includes turning off the WLAN interface after it enters the idle state and using the paging channel of WWAN in order to wake up the WLAN interface when there is incoming long-lived multimedia data. This scheme is known to limit the power consumption, while at the same time, it makes use of the paging channel in cellular networks. Further, our proposed scheme is designed to avoid repeatedly turning on and off WLAN interfaces, that consumes a significant amount of power. We propose turning on the WLAN interface when the number of packets in the radio network controller (RNC)'s buffer reaches a certain threshold level. The tradeoffs between the power saving and the number of packets dropped at the buffer are investigated analytically through the study of an on/off traffic model. Simulation results for scenarios of interest are also provided.
Multi-access edge computing (MEC) technology is envisioned as a promising paradigm to achieve the user needs of low-latency applications. Complex computation tasks are offloading from resource-constrained devices to resource-rich devices to reduce task completion delays. However, given the high-speed mobility of vehicles, the traditional MEC network architecture is insufficient for the Internet of Vehicle (IoV) computing scenarios. Besides, considering that many resource-rich idle vehicles can be used as mobile servers to perform computing tasks, extending the choices for vehicle users. To better integrate MEC and IoV technologies, we introduce a Cellular-V2X-based MEC offloading scenario, enabling the MEC server and vehicle nodes in a 5G cellular network environment to perform offloading cooperatively. For a typical delay-sensitive task, taking the Augmented Reality (AR) application as an example, we divide the task into multiple subtasks with linear correlation. A mobility-aware dynamic offloading algorithm (MADO) is proposed to minimize the impact of vehicular mobility on offloading. The algorithm is used to find an optimal resource allocation, which reduces the overhead of the entire offloading process. It continuously updates the resource selection and the offloading strategy with the vehicular location changes. Simulation results corroborate that our proposed MADO algorithm can effectively reduce task completion time, improve task completion success rate and adapt to a dynamic environment.
Newer technological advancements in ubiquitous networking have boosted digital dependency of users, thereby facilitating human–computer interaction (HCI). Quality of Experience (QoE) is an important aspect to analyze network performance. However, achieving desired level of user satisfaction is quite challenging which has led to the proliferation of context-aware computing (CAC). The paper focused over various context-gathering mechanisms, system architecture and contemplated on how to improve the Quality of Content (QoC).
Vehicular communication enables a variety of safety, infotainment, mobility, and environmental applications. Vehicular communication is one of the leading research areas because of its specific applications and characteristics and has attracted great interest from academia, industries, and governments. Our paper is a comprehensive survey of vehicular communication that covers the state of the art and future research directions. The article is a new contribution in the similar category of tutorials/surveys of the vehicular communication domain with the latest details. State of the art presents the architecture, applications, emerging radio access technologies, standardization, and project activities. We review the protocol stacks of the intelligent transportation system (ITS) in the USA, Japan, and Europe with their latest standards. In this paper, we present the emerging radio access technologies such as visible light communication, mmWave, Cellular-V2X, and 5G for connected and autonomous vehicles and their associated challenges. The new research directions in the emerging areas of this domain, such as seamless connectivity, edge, fog, software-defined and named data network, and security are also present. We believe that our work will help the researchers, developers and government agencies to become familiar with the latest features of the domain.
The ever-growing interest in multimedia services and the need for appropriate approaches for the delivery of video streaming in Vehicular Ad-hoc Networks require the definition of favorable strategies that implies a guarantee of the perceived video quality. Considering the degradation of the perceived video quality during handover process, we suggest an intelligent handoff vehicle agent that provides a predictive handoff decision. The proposed handoff mechanism is based on a predicting method to forecast the link Quality between the RSU and the vehicle with a cross-layer QoE triggering in a downloading video streaming scenario. The Link Quality and QoE aware Predictive Vertical Handoff mechanism for Video streaming (LQPVH) is a cross-layer method proactively reducing the handover disruption time. The selection of the best network to handover to is based on a Handoff Weight function exploiting an elimination factor with RSSI, experienced QoS and QoE parameters. The benefit of predicting the handoff point is illustrated by a set of simulations employing a video streaming traffic, showing how the quality of experience perceived by end-users can be enhanced through a prediction of handoff process. Results demonstrate that our proposal guarantees video quality improvement compared with Speed-based Vertical HandOver solution (SVHO).
We introduce State-Informed Link-Layer Queuing (SILQ), a system that models, predicts, and avoids packet delivery failures caused by temporary wireless outages in everyday scenarios. By stabilizing connections in adverse link conditions, SILQ boosts throughput and reduces performance variation for network applications, for example by preventing unnecessary TCP timeouts due to dead zones, elevators, and subway tunnels. SILQ makes predictions in real-time by actively probing links, matching measurements to an overcomplete dictionary of patterns learned offline, and classifying the resulting sparse feature vectors to identify those that precede outages. We use a clustering method called sparse coding to build our data-driven link model, and show that it produces more variation-tolerant predictions than traditional loss-rate, location-based, or Markov chain techniques.
We present extensive data collection and field-validation of SILQ in airborne, indoor, and urban scenarios of practical interest. We show how offline unsupervised learning discovers link-state patterns that are stable across diverse networks and signal-propagation environments. Using these canonical primitives, we train outage predictors for 802.11 (Wi-Fi) and 3G cellular networks to demonstrate TCP throughput gains of 4x with off-the-shelf mobile devices. SILQ addresses delivery failures solely at the link layer, requires no new hardware, and upholds the end-to-end design principle, to enable easy integration across applications, devices, and networks.
Improving Quality of Service (QoS) in wireless networks is important and necessary for mobile users. We have previously proposed Comfort Route (CR) Navigation, which navigates users to their destinations using high QoS communication areas, such as Wi-Fi APs, rather than the geographical Shortest Route (SR). In this paper, we employ an analytical model to estimate the CR gain in a theoretical manner which assumes that available cellular and Wi-Fi throughputs are uniform within their coverage. The CR gain is computed by using basic parameters, including wireless network bandwidth and transmission time. To validate our model, we compare simulation results and real observation. These results conclude that the CR gain could estimate by using our analytical model.
To improve Quality of Service in wireless networks while mobile users travel, we introduce Comfort Route Navigation (CRN) which is a navigation system based on a user centric mobility management for next generation wireless networks. CRN provides an optimal route that satisfies user needs, such as obtaining maximum wireless resources. To achieve CRN, we construct an access point (AP) map of Shinjuku city. To reflect quality of APs in this map, we evaluate throughputs at seven public Wi-Fi spots. Based on these observations, we evaluate performance of our CRN via computer simulations and in a real environment. These evaluations conduct that a CRN user could obtain higher communication quality rather than a Shortest Route (SR) user. These evaluations also conclude that CRN gain depends heavily on the quality and location of the best broadband spot.
Over the last few decades, we have been witnessing a tremendous evolution in mobile computing, wireless networking and hand-held devices. In the future communication networks, users are anticipated to become even more mobile demanding for ubiquitous connectivity to different applications which will be preferably aware of their context. Admittedly, location information as part of their context is of paramount importance from both application and network perspectives. From application or user point of view, service provision can upgrade if adaptation to the user's context is enabled. From network point of view, functionalities such as routing, handoff management, resource allocation and others can also benefit if user's location can be tracked or even predicted. Within this context, we focus our attention on indoor localization and handoff prediction which are indispensable components towards the ultimate success of the envisioned pervasive communication era. While outdoor positioning systems have already proven their potential in a wide range of commercial applications, the path towards a successful indoor location system is recognized to be much more difficult, mainly due to the harsh indoor characteristics and requirement for higher accuracy. Similarly, handoff management in the future heterogeneous wireless networks is much more challenging than in traditional homogeneous networks. Handoff schemes must be seamless for meeting strict Quality of Service (QoS) requirements of the future applications and functional despite the diversity of operation features of the different technologies. In addition, handoff decisions should be flexible enough to accommodate user preferences from a wide range of criteria offered by all technologies. The main objective of this thesis is to devise accurate, time and power efficient location and handoff management systems in order to satisfy better context-aware and mobile applications. For indoor localization, the potential of Wireless Local Area Network (WLAN) and Radio Frequency Identification (RFID) technologies as standalone location sensing technologies are first studied by testing several algorithms and metrics in a real experimental testbed or by extensive simulations, while their shortcomings are also identified. Their integration in a common architecture is then proposed in order to combine their key benefits and overcome their limitations. The performance superiority of the synergetic system over the stand alone counterparts is validated via extensive analysis. Regarding the handoff management task, we pinpoint that context awareness can also enhance the network functionality. Consequently, two such schemes which utilize information obtained from localization systems are proposed. The first scheme relies on a RFID tag deployment, alike our RFID positioning architecture, and by following the WLAN scene analysis positioning concept, predicts the next network layer location, i.e. the next point of attachment to the network. The second scheme relies on an integrated RFID and Wireless Sensor/Actuator Network (WSAN) deployment for tracking the users' physical location and subsequently for predicting next their handoff point at both link and network layers. Being independent of the underlying principle wireless access technology, both schemes can be easily implemented in heterogeneous networks. Performance evaluation results demonstrate the advantages of the proposed schemes over the standard protocols regarding prediction accuracy, time latency and energy savings
A multicast session protocol in wireless networks reduces the session delay of multicast delivery caused by moving of mobile host. A hand-off scheme, called MSDR (multicast session delay reduction), in mobile networks is proposed. MSDR protocol that minimizes the delay of a session re-establishment uses the basic unicast routing function of the IETF mobile IP and the DFA (designated foreign agent) to provide multicast services for mobile hosts. Proposed MSDR protocol allows the mobile hosts to continuously receive packets when they move across the basic sets during hand-off. Discrete-event simulation carried out for performance evaluation of MSDR protocol, and simulation results indicated that our scheme can offer a better performance of multicast session delay reduction in terms of signalling cost than that of IETF.
IEEE 802.16 is protocol for fixed broadband wireless access that is currently trying to add mobility among the mobile users in the standard. However, mobility adds some technical barriers that should be solved first, this is the case of HO "Handoff" (change of connection between two base stations "BS" by a mobile user). In this paper, the problem of HO in IEEE 802.16 is approach trying to maintain the quality of service of mobile users. A mechanism for changing connection during HO is presented. A simulation model based on OPNET MODELER v11 was developed to evaluate the performance of the proposed HO mechanism. Finally, this paper demonstrates that it is reliable to implement a seamless HO mechanism over IEEE 802.16 even for users with demanding applications such as voice over IP.
Due to the increasing popularity of mobile devices and the growing development of wireless networks, nowadays automobiles are able to communicate among them and with the infrastructure using different wireless technologies, thus improving not only communications but also safety on the roads. In order to improve communications by maintaining the Quality of Service (QoS) required by applications (e.g. throughput, latency) while the car is moving, switching from one base station to another, Vertical Handover techniques are the most adequate solution. In this work we present a Vertical Handover Decision Algorithm powered by the IEEE 802.21 protocol which takes advantage of the current devices deployed in the vehicle's on-board unit by considering geolocation, car navigation and realistic propagation model of different underlying networks such as Wi-Fi, WiMAX, and UMTS. Results demonstrate that QoS can be guaranteed when location and networking parameters (such as packet delay and bandwidth offered) are jointly considered.
Integration of different wireless networks can provide a universal ubiquitous coverage and various transmission rates for Mobile Terminals (MTs). To achieve ubiquitous computing, an MT needs to switch or handoff its connection between different or similar types of wireless networks. Our previous work used NDMD (Network Discovery based on user Motion Detection) that triggers network discovery based on an MT's motion and Received Signal Strength (RSS) to assist handoff decision. However, due to multipath fading, a wireless signal is strongly affected by environment and hence the motion detection based on RSS in NDMD may not be accurate. Thus, in this paper, we exploit a cross layer approach called packet loss aware NDMD, or PLA-NDMD, that uses TCP CWND (Congestion Window Size) as a packet loss index in couple with NDMD to cope with the problem. Experiment results show that PLA-NDMD can trigger a MT to perform handoff at appropriate timings and improve the data transmission throughput between MT and a wired station.
Handoff management is one of the main research challenges for the realization of the envisioned mobile and wireless Internet. This is mainly due to the latency delay and energy consumption introduced during handoff, which are of major concern for real-time applications and battery-constrained mobile terminals. In this paper, we explore whether handoff management can benefit from the pervasiveness of future communication networks. The key idea is to follow the ambient intelligence paradigm for the purpose of context-aware handoff. More precisely, we focus on the Radio Frequency Identification (RFID) and Wireless Sensor and Actuator Networks (WSANs) pervasive technologies, and propose two schemes for handoff prediction at the network layer or at both link and network layers, respectively. Analytical models for their time response and energy consumption are firstly derived. Then simulation-based results show that both of our schemes can achieve 38% to 93% reduction in time response while the second scheme provides 88% energy savings, validating their superiority over the standard solutions.
m Abstract- The next generation of wireless networks will integrate the current co-existing wireless networks to allow the users to connect to the network that best suits their needs. The users will be enabled to roam among different networks by a process known as vertical handover. Vertical handover can be imperative or alternative depending upon the reason of handover initiation. In this paper, we have proposed algorithms to perform imperative and alternative handovers. Our proposed algorithms are efficient in terms of decrease in handover call drop rate and avoidance of ping-pong effect. To elongate the battery life of mobile station, we have proposed a power-based algorithm that will be triggered when the power of mobile station drops below a certain threshold. All of our proposed algorithms will increase user satisfaction in 4G networks in terms of received signal strength, QoS and conservation of battery life.
WDMB technology has merits of high bandwidth and high mobility. But WDMB also has uni-directional communication problem. This paper provides solution to supplements uni-directional communication problem of WDMB with embodying return channel using WWAN to offer high quality multimedia service to user. Also this paper proposes intelligent network interface selection algorithm using various network information and return channel type. As a result of simulation, our proposed scheme is better as compared with other handoff scheme in energy efficiency of 7{\sim}8% and about two time of handoff number of time decrease.
There are a few representative wireless network access technologies used widely. WWAN is celluar based telecommunication networks supporting high mobility, WLAN ensures high data rate within hotspot coverage, and WDMB support both data and broadcasting services correspondingly. However, these technologies include some limitations especially on the mobility, data rate, transmission direction, and so on. In order to overvome these limitations, there are various studies have been proposed in terms of 'Vortical Handoff' that offers seamless connectivity by switching active connection to the appropriate interface which installed in the mobile devices. In this paper, we propose the interface selection algorithm and network architecture to maximize the life time of entire system by minimizing the unnecessary energy consumption of another interfaces such as WLAN, WDMB that are taken in the user equipment. In addition, by using the results of analyzing multiple types of traffic and managing user buffer as a metric for vertical handoff, we show that the energy efficiency of our scheme is and than typical WLAN for WDMB and WLAN preferred schemes, correspondingly.
This paper presents efficient motion detection of mobile node (MN) based on weighted momentum of received signal strength (WMRSS) in support of better handoff management in wireless network. In this method, for making momentum of received signal strength (MRSS) more accurate in detecting motion of MN, weight is applied to the received signal strength (RSS) of MN according to the priority and weighted average determined in calculating exponential moving average (EMA). To make WMRSS more effective and sensitive to the motion of user, dynamic smooth factor is used hence the method is called dynamic WMRSS (DWMRSS). Numerical simulation results are presented for DWMRSS method and compared with DMRSS scheme. Obtained result shows that the proposed method detects the motion of MNs more effectively and helps to reduce unnecessary handoff and loss of power.
Communications among vehicles and their capability of accessing cloud services is about to become a reality due to the ongoing development of sophisticated On-Board Units, which are powered by advanced processors, GPS devices,sensors, and multiple wireless access technologies such as Wi-Fi, WiMAX and UMTS. Users within vehicular networks will be able to access content from the Internet at high speeds while moving from one place to another, switching among multiple access points with heterogeneous coverage areas, as well as with different Quality of Service (QoS) levels offered. To maintain data connections alive in such dynamic conditions, Vertical Handover techniques are required. In this paper we present a Vertical Handover Decision Algorithm designed for dynamic environments. The decision making process is optimized by combining networking information, obtained by the services of the IEEE 802.21 standard, with geolocation, map information, surround context information and route calculation, thereby improving the handovers' performance.
In this article, we examine the Location Management costs in mobile communication networks utilizing the timer-based method. From the study of the probabilities that a mobile terminal changes a number of Location Areas between two calls, we identify a threshold value of 0.7 for the Call-to-Mobility Ratio (CMR) below which the application of the timer-based method is most appropriate. We characterize the valley appearing in the evolution of the costs with the timeout period, showing that the time interval required to reach 90% of the stabilized costs grows with the mobility index, the paging cost per Location Area and the movement dimension, in opposition to the behavior presented by the time interval that achieves the minimum of the costs. The results obtained for CMRs below the suggested 0.7 threshold show that the valley appearing in the costs tends to disappear for CMRs within [0.001, 0.7] in one-dimensional movements and within [0.2, 0.7] in two-dimensional ones, and when the normalized paging cost per Location Area is below 0.3.
In Next-Generation (NG) hybrid wireless networks, Mobile-Controlled Handover (MCHO) is expected to be employed as the handover
control mechanism, in contrast to Network-Controlled Handover (NCHO) used in homogeneous wireless networks. As more independent
network operators get involved in providing Internet access, roaming mobile users would have to deal with complex trust relationships
between heterogeneous network domains. The state-of-the-art handover approaches just take into account Quality of Service
(QoS), but ignore the complexities arising from the coexistence of multiple network operators in the NG networks. The existence
of a complex trust relationship between networks may lead to unnecessary handover attempts in service roaming. In this regard,
this paper introduces a novel approach of dynamically retrieving network trust information, and using it in MCHO. We show
how network trust information can be utilised to obtain a 35% reduction in handover delay, meanwhile retain QoS in a handover.
The proposed scheme does not need bulk storage in mobile handsets, and can react to changes to network topology and trust
relationships dynamically. Analytical results are provided to demonstrate how roaming mobile users make more intelligent and
reliable handover if implementing the proposed handover approach in a multi-operator and multi-technology environment.
In next generation wireless networks mobility management is a severe problem that needs careful attention, in order to achieve inter-working of Internet with wireless networks, and to meet the requirement of seamless handoff for real-time and multimedia applications. Advanced mobility support is required to effectively deal with the challenges that mobility poses. Single layer-specific mobility management architectures can hardly provide advanced mobility support required in future all-IP wireless networks. Advanced mobility support calls for a coordination of layers through a well defined cross layer platform to achieve better performance. We propose a mobility scenario driven mobility management architecture that exploits cross layer design in wireless terminals to provide seamless terminal mobility in future all-IP wireless network. Each mobility scenario uses a specific cost function that incorporates parameters necessary to support handoff decision in that particular environment
The paper presents an experimental geographical testbed used to analyze the handover performance of the mobile IPv6 (MIPv6) protocol. The analysis carried out using a current implementation of MlPv6 protocol has allowed us to identify that a relevant contribution to handover latency can be associated to the handover decision. In the standard implementation, this procedure is triggered by the layer 3 neighbor unreachability detection algorithm. To overcome this problem, we have developed and tested a kernel module devoted to the dynamic management of the network interfaces of a mobile node. The developed interface management module (IMM) works in cooperation with the mobile IPv6 implementation, extending Its functionalities to better support interface selection and movement detection. The experimental performance analysis highlights the ability of the proposed IMM to reduce the vertical handover decision time
Next generation wireless networks are foreseen to be heterogeneous in nature.Wireless networks consisting of different access technologies with different bandwidth and coverage area will coexist to provide roaming users with their requirements. Handoff among heterogeneous networks, i.e. vertical handoff (VHO), has attracted enormous attention from researchers over the last couple of years. Absence of symmetry is the core distinction between homogeneous and heterogeneous networks, as one network has preference over the other network. Therefore a proficient handoff mechanism is crucial for making the experience seamless to the user, trim down the number of unnecessary handoffs, as well as to capitalize on the underlay network utilization. In this article, we propose an advanced filtering based VHO algorithm in 3G/WLAN and discuss its performance. Performance criteria are based on the number of handoffs.
We present extensions to a traditional cellular [Ses95] handoff system to handle the simultaneous operation of multiple wireless network interfaces. This new system allows mobile users to roam in a "Wireless Overlay Network" structure consisting of room-size, building-size, and wide-area data networks. In this structure, the user can connect to the wired network through multiple wireless subnets, and offers the best possible connectivity given the user's geographic location and local wireless connectivity. We present the basic handoff system and show that the handoff latency is bounded by the amount of time that the mobile host takes to discover that it has moved in or out of a new wireless overlay. To efficiently support applications that can not tolerate these disruptions, we present optimizations to this basic scheme that assume no knowledge about specific channel characteristics. For handoffs between room-size and building-size overlays, these optimizations lead to a handoff latenc...
Vertical handoff means mobility between heterogeneous wireless access network technologies. Hierarchical radio access networks with overlapping cells gives an opportunity to handoff between local area high bandwidth networks and wide coverage cellular data. Vertical mobility combines the capacity of local area networks and the coverage of wide area cellular networks. Resource allocation in this kind of environment has not been yet fully addressed in the current research work. Clearly, additional bandwidth offered by wide-band local area wireless networks opens a new area for network performance optimization. For that, it is needed to understand the processes that have an effect on the system performance. In particular, vertical mobility is usually characterized by handoffs between systems having different data rates. The most critical area for system performance is at the very edge of the cell, where the received signal strength (RSS) varies around the sensitivity threshold of the receiver. Simulation results show the estimates of the delay and general performance in a multiple radio network environment. Generalization of handoff performance between multiple radio networks with different data rates is given with analysis.
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
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
The design of hard handoff algorithms based on optimizing the
tradeoff between link quality and rate of handoffs is considered. For
handoff algorithms based on this criterion, adaptation is precisely
defined in terms of remaining on a locus of desirable operating points
as system parameters (such as mobile velocity) change. A rule based on a
linear cost criterion is used to select desirable operating points. For
this rule, it is shown that the optimal handoff algorithm, which is
impractical, is easily adapted by fixing a single tradeoff parameter at
an appropriate value. The same adaptation property is shown to hold for
an easily implementable approximation to the optimal algorithm, the
locally optimal (LO) handoff algorithm. This is in contrast to the poor
adaptation of hysteresis based approaches which require lookup tables
for adaptation. Practical estimators for all relevant system parameters
based on a short window of pilot signal strength measurements are also
discussed. It is shown that the LO algorithm adapts well when these
simple estimators are used. A hysteresis-threshold approximation to the
adaptive LO algorithm is also developed
E#cient hando# algorithms cost-e#ectively enhance the capacity and Qualityof Service (QoS) of cellular systems. This research presents novel approachesfor the design of high performance hando# algorithms that exploit attractivefeatures of several existing algorithms, provide adaptation to dynamic cellularenvironment, and allow systematic tradeo#s among di#erent system characteristics.
Narrowband measurements have been performed at 870 MHz in outdoor
urban microcells using low antenna heights. Typical path loss is shown,
and an empirical path loss model is proposed. The slow fading is
investigated, and a fading model for simulation purposes is suggested.
The main characteristic of the fast fading is described, and a
narrowband fast fading model is proposed
The landscape of today's telecommunications portrays an amazing patchwork of heterogeneous networks, with very few and complex bridges between them. In this context, IP technology has emerged as a natural means of initiating network convergence and the “All-IP” paradigm has become the implicit assumption for most studies on the next generation architecture design. However, the real added value of such networks from the user's point of view will lie in offering seamless and transparent services through any kind of network. This can only be achieved with a global solution for mobility management and some believe it to be Mobile IP. The purpose of this paper is to describe how the EURESCOM project P1013 FIT-MIP has evaluated the use of Mobile IP acting as a mobility management protocol federating various access network technologies such as PSTN, Wireless LAN or General Packet Radio System. The use of Mobile IP as the enabler for inter-access technology handoffs will be the first step towards providing always-on access to IP applications (e.g., VoIP, VPN, mobile Internet).
In this paper, we develop a vision for the future of wireless communications beyond the third generation, which consists of a combination of several optimized access systems on a common IP-based medium access and core network platform. Different access systems interwork via horizontal (intra-system) and vertical (inter-system) handover, service negotiation, and global roaming. These complementary access systems are optimized for different applications and environments. They are allocated to different cell layers in the sense of hierarchical cells with respect to cell size, coverage, and mobility to provide globally optimized seamless services for all users. New air interfaces can also be incorporated to satisfy demands for higher data rates, increased mobility, and reduced cost per bit. This vision requires international research and standardization activities to solve many technical challenges. Key issues include the global interworking of different access systems on a common platform, advanced antenna concepts, and the implementation of multi-mode and multi-band terminals as well as base stations via software-defined radio concepts.
Current trends show that 3G cellular network and WLAN will coexist and work together to support more users with higher data rate services over a wider area. In this hybrid mobile network, the WLAN provides high bandwidth data service over a small area while the 3G cellular network provides a higher mobility with lower bandwidth data service. To provide seamless data service to mobile users, vertical handoff between WLAN and 3G cellular network has to be implemented. We present the challenges in the vertical handoff. We propose a TCP scheme for a seamless vertical handoff, and present a performance evaluation. In the proposed scheme, the TCP sender and receiver use the Handoff (HO) option field in TCP header to recognize an impending handoff and a completing handoff. After a vertical handoff, the sender tries to readjust its data rate, since the new network has drastically different characteristics in contrast with horizontal handoff where keeping the same data rate improves performance. The proposed scheme can be implemented incrementally. It is not necessary to change all of the TCP senders for compatibility since it uses an optional field in TCP header.
This paper contributes to the issue of location-aided routing in ad-hoc wireless networks. It focuses on the location-aided routing (LAR) protocol and its way of building the forwarding zone. A modified-LAR algorithm is proposed and three variants of it are examined. All of them are based on the idea of enlarging the request zone, in case of failure of the route discovery phase, instead of restoring to flooding. Simulation results show that the proposed algorithm leads to an improvement in the control overhead.
This paper presents an adaptive soft handoff algorithm that dynamically calculates the threshold values for soft handoff based on mobile location, signal strength and RF propagation statistics. An analytical model has been previously developed to study the performance of an adaptive hard handoff method using mobile location information. We extend the adaptive hard handoff algorithm to study the performance of an adaptive soft handoff algorithm and also analyze the soft handoff considerations. Unlike conventional soft handoff algorithms, the threshold values for the adaptive soft handoff algorithm are chosen dynamically based on a set of quantitative descriptors for various propagation environments. Simulation results show that the adaptive soft handoff method reduces the unnecessary handoff probability and the number of base stations in the active set while still maintaining the call quality. This improvement is significant if the propagation signal varies rapidly in the cell or in the dense urban area.
The ongoing wireless LAN standardization and R&D activities worldwide, which target bit rates higher than 100 Mb/s, combined with the successful deployment of WLANs in numerous hotspots justify the fact that WLAN technology will play a key role in wireless data transmission. Cellular network operators have recognized this fact, and strive to exploit WLAN technology and integrate this technology into their cellular data networks. For this reason, there is currently a strong need for interworking mechanisms between WLANs and cellular data networks. We focus on these interworking mechanisms, which effectively combine WLANs and cellular data networks into integrated wireless data environments capable of ubiquitous data services and very high data rates in hotspot locations. We discuss the general aspects of integrated WLANs and cellular data networks, and we examine the generic interworking architectures that have been proposed in the technical literature. In addition, we review the current standardization activities in the area of WLAN-cellular data network integration. Moreover, we propose and explain two different interworking architectures, which feature different coupling mechanisms. Finally, we compare the proposed interworking architectures, and discuss their advantages and drawbacks.
A simple autocorrelation model for shadow fading in mobile radio channels is proposed. The model is fitted to both large cells and microcells. Results show that the model fit is good for large to moderate cell sizes. It is however shown that the model does not provide adequate results for microcells.
Analytical framework for handoff in non-homogeneous mobile data networks
- A Hatami
- P Krishnamurthy
- K Pahlavan
- M Ylianttila
- J Mäkelä
- R Pichna
A. Hatami, P. Krishnamurthy, K. Pahlavan, M. Ylianttila, J. Mäkelä, R. Pichna, Analytical framework for handoff in non-homogeneous mobile data networks, in: Proceedings of the 10th IEEE International Symposium on PIMRC, Osaka, Japan, September 1999, pp. 760–764.
Feasibility study on 3GPP system to Wireless Local Area Network (WLAN) interworking (Release 6)
- Gpp Tr
GPP TR 22.934, Feasibility study on 3GPP system to Wireless Local Area Network (WLAN) interworking (Release 6), Technical Specification V6.2.0, September 2003, p. 30.
GPRS over WLAN access, in: Nokia Mobile Internet Technical ArchitectureVisions and Imple-mentations
- J Ekberg
- F Yang
J. Ekberg, F. Yang, GPRS over WLAN access, in: Nokia Mobile Internet Technical ArchitectureVisions and Imple-mentations, vol. 3, Edita Publishing, 2002, pp. 289–296.
He is now working as a Senior Teaching Assistant in the Telecommunication Laboratory and a Research Scientist in the Center for Wireless Communications at the University of Oulu
- Juha-Pekka Mäkelä
Juha-Pekka Mäkelä received his M.Sc.
and Lic.Tech. degrees in electrical
engineering from the University of
Oulu, Finland, in 1997 and 2002,
respectively. He is now working as a
Senior Teaching Assistant in the Telecommunication Laboratory and a
Research Scientist in the Center for
Wireless Communications at the University of Oulu. His current research
interests are intelligent handoff techniques and mobility management
issues in wireless networks.
Vertical handoffs in wireless overlay networks, Mobile Networks and Applications (Special Issue: Mobile Networking in the Internet
- M Stemm
- R Katz
M. Stemm, R. Katz, Vertical handoffs in wireless overlay
networks, Mobile Networks and Applications (Special
Issue: Mobile Networking in the Internet) 3 (4) (1998) 335–
350.
GPRS over WLAN access
- Ekberg