An Overview of Vertical Handoff Decision Algorithms in NGWNs and a new Scheme for Providing Optimized Performance in Heterogeneous Wireless Networks

Because the increasingly development and use of wireless networks and mobile technologies, was implemented the idea that users of mobile terminals must have access in different wireless networks simultaneously. Therefore one of the main interest points of Next Generation Wireless Networks (NGWNs), refers to the ability to support wireless network access equipment to ensure a high rate of services between different wireless networks. To solve these problems it was necessary to have decision algorithms to decide for each user of mobile terminal, which is the best network at some point, for a service or a specific application that the user needs. Therefore to make these things, different algorithms use the vertical handoff technique. Below are presented a series of algorithms based on vertical handoff technique with a classification of the different existing vertical handoff decision strategies, which tries to solve these issues of wireless network selection at a given time for a specific application of an user. Based on our synthesis on vertical handoff decision strategies given below, we build our strategy based on solutions presented below, taking the most interesting aspect of each one.Vertical Handoff, Genetic Algorithms, Fuzzy Logic, Neural Networks, AHP

An Overview of Vertical Handoff Decision Algorithms in NGWNs and a new Scheme for Providing Optimized Performance in Heterogeneous Wireless Networks

Because the increasingly development and use of wireless networks and mobile technologies, was implemented the idea that users of mobile terminals must have access in different wireless networks simultaneously. Therefore one of the main interest points of Next Generation Wireless Networks (NGWNs), refers to the ability to support wireless network access equipment to ensure a high rate of services between different wireless networks. To solve these problems it was necessary to have decision algorithms to decide for each user of mobile terminal, which is the best network at some point, for a service or a specific application that the user needs. Therefore to make these things, different algorithms use the vertical handoff technique. Below are presented a series of algorithms based on vertical handoff technique with a classification of the different existing vertical handoff decision strategies, which tries to solve these issues of wireless network selection at a given time for a specific application of an user. Based on our synthesis on vertical handoff decision strategies given below, we build our strategy based on solutions presented below, taking the most interesting aspect of each one

A comparison study of two fuzzy-based handover systems for avoiding ping-pong effect in Wireless Cellular Networks

Wireless mobile networks and devices are becoming increasingly popular to provide users the access anytime and anywhere. The mobile systems are based on cellular approach and the area is covered by cells that overlap each other. Many handover algorithms are proposed in the literature. However, to make a better handover and keep the QoS in wireless networks is very difficult task. For this reason, new intelligent algorithms should be implemented to deal with this problem. In this paper, we carried out a comparison study of two handover systems based on fuzzy logic. We implement two fuzzy-based handover systems (FBHS). We call them FBHS1 and FBHS2. The performance evaluation via simulations shows that FBHS2 has better behavior than FBHS2 and can avoid ping-pong effect in all simulation cases.Peer ReviewedPostprint (published version

Modelo AHP-VIKOR para handoff espectral en redes de radio cognitiva

This paper proposed a hybrid algorithm for spectrum allocation in cognitive radio networks based on two algorithms, analytical hierarchical process (AHP) and multi-criteria optimization and compromise solution (VIKOR), for improving the performance of mobility spectrum of secondary users in cognitive radio networks.To evaluate the level of performance of the proposed algorithm, a comparative analysis between the proposed AHP-VIKOR, Grey Relational Analysis (GRA) and a random allocation of spectrum (Random) algorithm, is performed. The first two algorithms work with the same decision criteria: probability of channel availability, estimated time availability, signal-to-interference-plus-noise ratio and bandwidth. Unlike related work, benchmarking was validated through a trace of real spectral occupation data, captured in the GSM frequency band, which models the actual behavior of licensed users. For performance evaluation five metric were used, handoff failed average cumulative number, handoff average cumulative number, average bandwidth, delay and average cumulative throughput.The results of the comparative analysis with the other two algorithms show that the AHP-VIKOR algorithm proposed provides the best performance in spectral mobility. En este artículo se presenta la propuesta de un algoritmo híbrido para la asignación de espectro en redes de radio cognitiva basado en los algoritmos Analytical Hierarchical Process (AHP) y Multi-Criteria Optimization and Compromise Solution (VIKOR), con el objetivo de mejorar el desempeño de la movilidad espectral de los usuarios secundarios en redes de radio cognitiva.Para evaluar el nivel de desempeño del algoritmo propuesto se realiza un análisis comparativo entre  este, el Grey Relational Analysis (GRA) y una asignación de espectro aleatoria (Random). Los dos primeros trabajan con los mismos criterios de decisión: probabilidad de disponibilidad del canal, tiempo estimado de disponibilidad del canal, relación señal a ruido más interferencia y ancho de banda. A diferencia de los trabajos relacionados, la evaluación comparativa se validó a través de una traza de datos reales de ocupación espectral capturados en la banda de frecuencia GSM, que modela el comportamiento real de los usuarios licenciados. En la evaluación de desempeño se utilizaron cinco métricas de evaluación: número promedio acumulado de handoff fallidos, número promedio acumulado de handoff realizados, ancho de banda promedio, retardo promedio acumulado y throughput promedio acumulado.Los resultados del análisis comparativo con los otros dos algoritmos muestran que el algoritmo de handoff AHP-VIKOR propuesto provee el mejor desempeño en la movilidad espectral

Handoff Triggering and Network Selection Algorithms for Load-Balancing Handoff in CDMA-WLAN Integrated Networks

This paper proposes a novel vertical handoff algorithm between WLAN and CDMA networks to enable the integration of these networks. The proposed vertical handoff algorithm assumes a handoff decision process (handoff triggering and network selection). The handoff trigger is decided based on the received signal strength (RSS). To reduce the likelihood of unnecessary false handoffs, the distance criterion is also considered. As a network selection mechanism, based on the wireless channel assignment algorithm, this paper proposes a context-based network selection algorithm and the corresponding communication algorithms between WLAN and CDMA networks. This paper focuses on a handoff triggering criterion which uses both the RSS and distance information, and a network selection method which uses context information such as the dropping probability, blocking probability, GoS (grade of service), and number of handoff attempts. As a decision making criterion, the velocity threshold is determined to optimize the system performance. The optimal velocity threshold is adjusted to assign the available channels to the mobile stations. The optimal velocity threshold is adjusted to assign the available channels to the mobile stations using four handoff strategies. The four handoff strategies are evaluated and compared with each other in terms of GOS. Finally, the proposed scheme is validated by computer simulations

Access Network Selection in Heterogeneous Networks

The future Heterogeneous Wireless Network (HWN) is composed of multiple Radio Access Technologies (RATs), therefore new Radio Resource Management (RRM) schemes and mechanisms are necessary to benefit from the individual characteristics of each RAT and to exploit the gain resulting from jointly considering the whole set of the available radio resources in each RAT. These new RRM schemes have to support mobile users who can access more than one RAT alternatively or simultaneously using a multi-mode terminal. An important RRM consideration for overall HWN stability, resource utilization, user satisfaction, and Quality of Service (QoS) provisioning is the selection of the most optimal and promising Access Network (AN) for a new service request. The RRM mechanism that is responsible for selecting the most optimal and promising AN for a new service request in the HWN is called the initial Access Network Selection (ANS). This thesis explores the issue of ANS in the HWN. Several ANS solutions that attempt to increase the user satisfaction, the operator benefits, and the QoS are designed, implemented, and evaluated. The thesis first presents a comprehensive foundation for the initial ANS in the H\VN. Then, the thesis analyses and develops a generic framework for solving the ANS problem and any other similar optimized selection problem. The advantages and strengths of the developed framework are discussed. Combined Fuzzy Logic (FL), Multiple Criteria Decision Making (MCDM) and Genetic Algorithms (GA) are used to give the developed framework the required scalability, flexibility, and simplicity. The developed framework is used to present and design several novel ANS algorithms that consider the user, the operator, and the QoS view points. Different numbers of RATs, MCDM tools, and FL inference system types are used in each algorithm. A suitable simulation models over the HWN with a new set of performance evolution metrics for the ANS solution are designed and implemented. The simulation results show that the new algorithms have better and more robust performance over the random, the service type, and the terminal speed based selection algorithms that are used as reference algorithms. Our novel algorithms outperform the reference algorithms in- terms of the percentage of the satisfied users who are assigned to the network of their preferences and the percentage of the users who are assigned to networks with stronger signal strength. The new algorithms maximize the operator benefits by saving the high cost network resources and utilizing the usage of the low cost network resources. Usually better results are achieved by assigning the weights using the GA optional component in the implemented algorithms

Algoritmos para asignación de espectro en redes de radio cognitiva

Context: Spectrum allocation in cognitive radio networks is a key aspect to reduce latency, increase data rate, increase bandwidth, improve capacity and coverage, and optimize the use of the spectrum, guaranteeing the quality of service required applications and best-effort and real-time.Objective: This paper aims to present a review of the algorithms for spectrum allocation in cognitive radio networks, describing the relevant algorithms for spectrum allocation and its classification according to the current literature.Method: The development of this review was conducted based on the analysis of recent publications of mainstream with their respective appointments, trying to provide a complete reference framework of the current literature on the algorithms for spectrum allocation in cognitive radio networks.Results: The main results determine the importance of smart spectrum allocation, taking into account the traffic load, user behavior, interference levels, spectral characterization, the type of application and the need for multiple frequency channels.Conclusion: In conclusion it is important to design adaptive algorithms to make efficient use of the available portions of the licensed spectrum.Contexto: La asignación de espectro en las redes de radio cognitiva es un aspecto clave para reducir la latencia, incrementar la tasa de datos, aumentar el ancho de banda, mejorar la capacidad y cobertura, y optimizar el uso del espectro, garantizando la calidad de servicio necesaria para aplicaciones de tiempo-real y mejor-esfuerzo. Objetivo: Este artículo presenta una revisión sobre los algoritmos de asignación de espectro en redes de radio cognitiva, describiendo los algoritmos de asignación de espectro más relevantes y su clasificación de acuerdo con la literatura actual.Método: El desarrollo de esta revisión se realizó a partir del análisis de publicaciones recientes de corriente principal con sus respectivas citas, tratando de proveer un marco referencial de la literatura actual sobre los algoritmos de asignación de espectro en redes de radio cognitiva.Resultados: Los principales resultados determinan la importancia de una asignación de espectro inteligente, teniendo en cuenta la carga de tráfico, el comportamiento del usuario, los niveles de interferencia, la caracterización del espectro, el tipo de aplicación y la necesidad de múltiples canales de frecuencia.Conclusión: Como conclusión es importante diseñar algoritmos adaptativos que permitan hacer un uso eficiente de las porciones disponibles del espectro licenciado.