A softer vertical handover algorithm for heterogeneous wireless access networks

State-of-the-art wireless communication networks that enable safety and emergency services are predominantly based on Terrestrial Trunked Radio (TETRA). TETRA guarantees four nines of average end-to-end connection availability, but offers low data rate. Originally low-data rate safety and emergency services evolve from basic as voice and messaging towards video and other applications that require high data rate. Emergency and safety-critical voice and messaging, however, fall under a category of ultra-reliable communications and require an average connection availability of five nines, i.e., an average outage time of 5.25 minutes per year. The challenge that we address in this paper is guaranteeing the average connection availability for the ultra-reliable communications as voice, while providing sufficient data rate for the complimentary services as video. We achieve this by using heterogeneous wireless access network, i.e., WLAN, LTE and TETRA, enhanced with automated switching between the wireless technologies through Dynamic Link Exchange Protocol (DLEP). Based on the testbed measurements and reliability analysis, we show that a heterogeneous access network can achieve the five nines availability, while increasing the available data rate in comparison with single technology access networks.

It is well known that mobile networks are facing a tsunami of data traffic and user devices. Traditionally, the capacity of radio access network is mainly increased by efficient, spectrum allocation, advance modulation schemes and frequency division techniques. However, new demands for network capacity and connectivity are completely unprecedented and they cannot be solved by these existing techniques only. Mobile Network Operators (MNO) have to add cost efficient resources/technologies to smoothly operationalize their networks. Fortunately, heterogeneous wireless access networks are able to provide speedy, cost efficient, customized and self-reliant solution in such a complicated communication scenario. In this paper, we present a brief survey of various heterogeneous access network architectures, the key challenges and future architectural trends.

Heterogeneous wireless access networks (HWAN) will create a market for the delivery of an extensive collection of novel and attractive services and contents. Accounting and pricing the ubiquitous services will play a key role from both service providers and users point of view. By one hand, wireless service providers (WSP) look for the maximum revenue and utilization rate and by other hand users will select service providers depending on the offered price and the Quality of Service (QoS) assurance. In such a market-based scenario, accounting will become an effective tool that satisfies the users' service demands and maximizes the revenue of the providers. For WSP is of vital importance to define a charging and accounting architecture that supports fast and easy the provision of existent and new services with the best quality. In this sense, a dynamical network selection mechanism has to be developed to decide an appropriate radio access cell or technology for a specific service. Additionally, service providers must consider alternative solutions to situations where the best quality for the requested service cannot be provided, allowing them maintaining a high user satisfaction level. In this paper we propose a simple QoS-based dynamic pricing approach for services provisioning into a heterogeneous wireless access networks environment which attempts to increase user's satisfaction level by firstly, maximizing the provided QoS level, and secondly, by applying dynamic pricing strategies according to the QoS. These strategies will allow service providers to maximize their profits. Simulations results demonstrate that the proposed dynamic pricing approach benefits both users and WSP. Results suggest that users have better overall satisfaction due to a better QoS level and fairer prices. The analysis shows that our proposed pricing approach helps increasing WSPs profits compared to the application of the flat-rate pricing model into a competitive market-model.

Future wireless Internet is expected to consist of various heterogeneous wireless access networks with different properties to support different type of services. In order to improve the accuracy of the vertical handover decision for such heterogeneous networks, this paper proposes an adaptive multi-criteria vertical handover framework. This framework focuses on several main aspects of a vertical handover. It is able to trigger a handover intelligently and make a handover decision effectively and adaptively.

This paper presents a predictive framework for mobility-aware prefetching to enhance the experience of a mobile Web user roaming between heterogeneous wireless access networks. We consider a heterogeneous two-tier wireless access network system, composed of smaller, but faster and cheaper wireless local area networks (WLAN) placed within a much larger, but slower and more expensive cellular wireless data network. An optimal prefetch threshold algorithm is proposed, which takes into consideration the user mobility pattern, the relative characteristics of the networks, and the user perceived value of time. Using current industry network parameters, we study the performance of the proposed prefetching algorithm. Our numerical results show how user mobility and the heterogeneous network configuration significantly alter the prefetching threshold. The performance of this algorithm is compared with that of a static prefetching algorithm, demonstrating that mobility-aware prefetching can significantly improve the performance of future-generation heterogeneous wireless networks.

Over the past decade or so, the wireless industry has undergone many significant changes. Radio systems have moved toward forming heterogeneous wireless networks: collaborations of multiple radio access networks, which in some cases operate different radio access technologies, such as second- and third-generation cellular RATs, IEEE 802.x wireless standards, and so on. On the other hand, multimode reconfigurable user devices with the ability to choose among various supported RATs have become a reality, and devices and networks with dynamic spectrum access capabilities, allowing real-time sharing of spectrum resource usage among different systems, are expected to be a part of the future radio eco-space. As a result of these changes, there is a need to develop a standard that addresses the requirements and leverages the opportunities posed by such a versatile radio environment. To this end, IEEE 1900.4 aims to standardize the overall system architecture and information exchange between the network and mobile devices, which will allow these elements to optimally choose from available radio resources. In other words, the standard facilitates the distributed dynamic optimization of the usage of spectrum offered by the heterogeneous wireless network, relying on a collaborative information exchange between networks and mobile devices, thereby acting as a common means to improve overall composite capacity and quality of service for the served networks. This article provides a snapshot of IEEE P1900.4 in its current form, covering the scope and purpose of the standard, reference use cases for which the standard is applicable, its system and functional architectures, and finally, the information model for its main interfaces.

This paper presents an ubiquitous connectivity solution for public transportation services and proposes a vertical handover (VHO) algorithm between cellular networks and WLANs, used to implement the ubiquitous connectivity in a heterogeneous wireless network. The system architecture, on which our solution relies, is also presented. The novelty of our approach is that the VHO algorithm takes the decision on the target network based on the background traffic and the link quality, besides the received signal level. Our algorithm exploits the fact that the communication device of the vehicle is equipped with several Wi-Fi interfaces which allow the measurement of the available WLAN's parameters. The performance of our algorithm is significantly better than those of a classical VHO algorithm which selects the target network based only on the level of the received signal and is similar to that of an optimal VHO algorithm which has complete knowledge of the network parameters.

This paper focuses on mobility management between heterogeneous Radio Access Networks (RANs). A fuzzy multi-criteria vertical handover algorithm that enhances the system performances is proposed. This algorithm is based on fuzzy logic control. The Fuzzy Logic Controller (FLC) takes into account multiple relevant criteria and a set of rules defined from prior knowledge. Neural network adapts automatically the FLC parameters to the environment fluctuations and the traffic variations. The performances of our handover algorithm are evaluated and compared to a conventional vertical handover algorithm by means of simulations. The proposed handover algorithm improves the user- perceived performances.

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.

Communication networks beyond 3G will see the interconnection of heterogeneous radio access networks in order to always provide the best quality of service in the most efficient way to users with multi-mode terminals. This scenario poses a number of critical issues, which have to be faced in order to get the best from the integrated network. In this paper we investigate the issue of parallel transmission over multiple radio access networks: in particular we propose simple but effective radio resource management algorithms, whose performance is investigated by means of a simulative approach in UMTS-IEEE802.11a and IEEE802.16e-IEEE802.11a heterogeneous networks (adopted as case studies). An insight on TCP level critical aspects, strictly related to the parallel transmission over multiple access networks, is also provided.

We propose a call flow for vertical handover procedure and a soft QoS scheme using dynamic programming (DP) approach for an efficient radio resource management in an environment where several different radio access networks (e.g., WLAN and WCDMA) coexists. We compare the soft QoS scheme with hard QoS scheme and propose a greedy and a DP approach for resource allocation scheme under a vertical handover situation. The proposed scheme is a promising approach for QoS support under the heterogeneous radio access networks. This work is supported by Korea Telecom.

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

Wireless networks are becoming a combination of more and more diverse and complicated networks. Handoff is a process to maintain data session continuity where mobile node changes from one base station coverage area to another base station area. Mobile maintains its existing connections via vertical handoff. In wireless environment single node mobility is known as host mobility and group of nodes moving together as single network is known as Network Mobility (NEMO). NEMO is extension of MIPv6, invented for reducing number of individual handoffs. To influence smooth mobility between these heterogeneous wireless access networks, expeditious and dependable vertical handoff (VHO) schemes are required. While taking VHO decision several parameters has to consider like received signal strength (RSS), addressable bandwidth, power intake, monetary cost, security, user predilection and etc. In this paper various handoff decision techniques based on different parameters for host mobility, and vertical handoff technique for Network mobility (NEMO) are discussed. Finally gave research issues and future research directions to NEMO.

Wireless technology is a revolutionary advancement providing users with ubiquitous data and telephony access anywhere and anytime with no physical (PHY) connection. The currently deployed wireless networks like Wi-Fi, Worldwide Interoperability for Microwave Access (WiMAX), Universal Mobile Telecommunications Systems (UMTS), and Long Term Evolution (LTE) systems have different characteristics that make them complementary in terms of performance, coverage, and cost. This network variety presents an opportunity to provide better services to end users, given the advances in mobile terminals (MTs). To reach this goal, an appropriate automatic network selection (ANS) mechanism, which is able to always select the best access network, is needed. This consists of constantly monitoring any type of available access network, i.e., automatically selecting and switching to the best one, as the network that maximizes the users quality of experience, taking into account their preferences and the terminal and network conditions. ANS is a multidimensional decision-making problem that can be solved by finding an appropriate complex tradeoff between possibly conflicting criteria. In this paper, we propose an analytical model to capture the preferences of end users. Based on this model, we design an ANS mechanism that takes into account all aspects of the tradeoff between the quality of the connections, the preferences of the end users, and the cost. To highlight the benefits of our approach from the perspectives of both end users and network operators, we have implemented and tested the solution in a multitechnology simulator. Results show that the proposed solution outperforms mainstream approaches.

In this paper we present a framework, called Futon, which provides a platform to integrate heterogeneous radio access networks. Futon is a hybrid fibre-radio network that replaces legacy base stations with simple remote antenna units, which are connected to a central unit. As a part of the Futon framework, a generic middleware architecture is discussed in detail, which provides interoperability, cooperative management and service provisioning to both underlying radio access networks (RANs) and IP layer for a heterogeneous network scenario. One of the middleware's functionality is to provide vertical handover between heterogeneous IP-based radio access technologies and to ensure seamless mobility and service continuity, which is implemented on top of an IPv4/IPv6 Mobile IP (MIP) core. In this paper, the Futon framework and a generic middleware architecture as a part of Futon framework for heterogeneous RANs is discussed. The main modules of the middleware, namely common radio resource management (CRRM), media independent handover, Service/Connection Manager and link selection are explained in detail. Radio over fibre (RoF) Manager is an important part of Central unit, which does performance, fault and security management of network elements. RoF manager helps middleware during handoff, by providing the status of fibre optic links. The implementation of Security management module as a part of RoF manager, and results of authentication with AAA protocol are explained. The CRRM as part of middleware is simulated and the results of experimental evaluation are presented.