Handoff Mechanism Research Articles

Energy-Aware Group LBS Using D2D Offloading and M2M-Based Mobile Proxy Handoff Mechanisms Over the Mobile Converged Networks

Since smart phones are always equipped with both cellular and Wi-Fi interfaces, this paper exploits the feasibility of the Wi-Fi-based device-to-device offloading mechanism to reduce cellular traffic. In our group location-based service (LBS) scenario, a group of users travel outdoors together and utilize their smart phones to form a mobile converged network, which is composed of cellular and Wi-Fi networks, to download and share the neighboring LBS data. Due to the wide-range coverage of the cellular network and the keeping-moving characteristic of users, one of these smart phones is selected to play the role of mobile proxy to download the shared LBS data using its cellular interface and then disseminate to other members using multicast over the Wi-Fi network, in which one adaptive FEC mechanism is adopted to tackle the packet loss situation. Besides, a user-transparent machine-to-machine-based mobile proxy handoff mechanism is devised such that each smart phone can play the role of mobile proxy alternately to evenly consume each smart phone’s power and thus extend the service time of the group LBS scenario. That is, the proposed offloading mechanism not only offloads the cellular network traffic but also reduces the power consumption.

Symmetry Breaking in an Edgeless Epithelium by Fat2-Regulated Microtubule Polarity.

Planar cell polarity (PCP) information is a critical determinant of organ morphogenesis. While PCP in bounded epithelial sheets is increasingly well understood, how PCP is organized in tubular and acinar tissues is not. Drosophila egg chambers (follicles) are an acinus-like "edgeless epithelium" and exhibit a continuous, circumferential PCP that does not depend on pathways active in bounded epithelia; this follicle PCP directs formation of an ellipsoid rather than a spherical egg. Here, we apply an imaging algorithm to "unroll" the entire 3D tissue surfaceand comprehensively analyze PCP onset. This approach traces chiral symmetry breaking to plus-end polarity of microtubules in the germarium, well before follicles form and rotate. PCP germarial microtubules provide chiral information that predicts the direction of whole-tissue rotation as soon as independent follicles form. Concordant microtubule polarity, but not microtubule alignment, requires the atypical cadherin Fat2, which acts at an early stage to translate plus-end bias into coordinated actin-mediated collective cell migration. Because microtubules are not required for PCP or migration after follicle rotation initiates, while dynamic actin and extracellular matrix are, polarized microtubules lie at the beginning of a handoff mechanism that passes early chiral PCP of the cytoskeleton to a supracellular planar polarized extracellular matrix and elongates the organ.

Optimized Communication of Group Mobility in WPAN

ZigBee is a low cost, low-power consumption and long battery life network that is based on the IEEE 802.15.4 standard; which is most usually used to transfer low data rates information in the Wireless Personal Area Network (WPAN). In the Wireless Personal Area Network (WPAN) network, capability of sensor network and mobile network are combined that have energy limit and sensing range limits. Here a network is composed of a number of Sub-Network or groups with the selection of group leader. Group formation is defined under sensing range limit, density limit and type of nodes. The selection of group leader is defined under velocity analysis, energy and average distance after that inter group and intra group communication is performed and then Handoff mechanism is performed when nodes switch the group or group switch the base station. Index Terms—BS (base station), WPAN (wireless personal area network), LOS (Line of sight), NLOS (Non Line of Sight), APP (Application Layer), NWK (Network Layer), MAC ( Medium Access Control).

An Insight towards Trends and Effectiveness of Vertical Handoff Mechanism

An Insight towards Trends and Effectiveness of Vertical Handoff Mechanism

Integrated Multi-service Handoff Mechanism with QoS-Support Strategy in Mobile Cloud Computing

Mobile devices are becoming the primary platforms for many users who always roam around and access the cloud computing applications. Using cloud computing services extensively and offloading local applications to the cloud, facilitate mobile devices keep multiple services online at the same time. Since the mobile device may move fast and session handoff among access networks comes up frequently, multiple services initiate handoff procedure results in lots of redundant signaling. The current handoff mechanisms only make the handoff control for each service individually, which brings much unnecessary energy consumption and ignores the different Quality of Service (QoS) requirement during handoff execution. To solve these issues, we propose an improved multi-services handoff mechanism, which uses the list method of session initial protocol to make all active services execute handoff together. And considering to support the QoS for each active service during handoff procedure, the differentiate policy for multi-service media transfer is included based on the integrated handoff signaling. Analytic model and simulation are developed to investigate the new mechanism. The results demonstrate that the improved multi-service handoff mechanism can efficiently save energy consumption for mobile devices and realize seamless handoff.

Vertical Handover Decision Algorithm Using Ants’ Colonies for 4G Heterogeneous Wireless Networks

With the development of 4G mobile telecommunication systems, providing users with the convenience of a seamless continuous connection is not enough anymore. Users want to be connected through the best available network with the best quality of service. It is necessary to have a good decision-making algorithm which decides whether it is necessary to perform handoff to another network, the best network to vertically perform handoff to, and the right time to initiate the handover. This paper proposes a new approach in which mobile terminals (MTs) continuously analyze the network and keep a database of the best available networks. The concept is based on QoS aware ant colony built on the vertical handoff mechanism that uses an updated version of ants’ colony optimization decision algorithm (ACOR), the dynamic and static factors such as RSS, the cost of service, bandwidth, the velocity of MT, the power consumption and security, and the module for predicting the traveling distance within an IEEE 802.11 WLAN cell. Simulation results show that we can not only meet the individual needs of users in terms of QoS, but also improve the whole system performance by reducing the number of handover failures and unnecessary handover instances by up to 95%.

A Novel Reliability Enhanced Handoff Method in Future Wireless Heterogeneous Networks

As the demand increases, future networks will follow the trends of network variety and service flexibility, which requires heterogeneous type of network deployment and reliable communication method. In practice, most communication failure happens due to the bad radio link quality, i.e., high-speed users suffers a lot on the problem of radio link failure, which causes the problem of communication interrupt and radio link recovery. To make the communication more reliable, especially for the high mobility users, we propose a novel communication handoff mechanism to reduce the occurrence of service interrupt. Based on computer simulation, we find that the reliability on the service is greatly improved.

IEEE 802.11 환경에서 사전 AP 정보를 이용한 핸드오프 성능 개선

° ABSTRACT This paper proposes the improved handoff mechanism for IEEE 802.11 wireless LANs. When a wireless mobile node moves out of the coverage of its currently associated AP(Access Point) and needs to be re-associated with a new AP, a handoff procedure is initiated. Channel scanning process during a handoff procedure occupies over 90% of total handoff latency. Long latency leads to many packet losses and service discontinuity, which degrades wireless network performance. This paper describes about the new mechanism to improve handoff performance by skipping channel scanning during a handoff procedure. In oerder for that, acquires neighboring AP information such as its address, location, channel number in use, the number of associated nodes before handoff, and delivers the information to its associated mobile nodes. The mobile nodes can reduce handoff latency and perform more exact handoff using the delivered AP information. We have conducted simulations to analyze our proposal's performance and confirmed that handoff latency and the number of handoff occurrences are decreased.

IEEE 802.11 무선 랜에서 이웃 채널 정보에 기반한 점진적 채널 스캔 방법

IEEE 802.11 무선 랜에서 단말들은 자유롭게 이동할 수 있기 때문에 끊김 없는 서비스를 제공하기 위해 핸드오프가 중요하다. 무선 랜에서 핸드오프할 때 많은 채널에 대해 스캔을 수행하기 때문에 핸드오프 지연이 커져 실시간 서비스를 지원하는데 한계가 있다. 본 논문에서는 실시간 서비스를 위해 핸드오프 지연을 최소화하는 방법을 제안한다. 제안하는 방법에서, 무선 랜에 처음 접속하는 단말은 자신이 스캔한 채널 정보를 AP(Access Point)에게 전송한다. AP는 단말이 전송한 정보를 이용하여 서로 이웃하는 채널들의 정보를 테이블로 만들고 비콘 프레임을 통해 이 테이블을 단말들에게 전송한다. 단말들은 핸드오프를 진행할 때 전체 채널에 대해 스캔을 수행하지 않고 테이블에 있는 정보를 이용하여 일부 채널에 대해서만 스캔을 수행한다. 따라서 제안하는 방법은 핸드오프 지연을 줄일 수 있고 실시간 서비스를 지원할 수 있다. Handoff is a critical issue for seamless roaming in IEEE 802.11-based wireless networks. In order to provide real-time services, handoff mechanism must be provided. However, the IEEE 802.11 standard handoff is not appropriate to provide the services, because it is based on the full-scanning approach which spends too much time searching Access Point (AP). In this paper, we propose a new scheme, which can reduce the scanning latency. A station performs full-scanning operation for finding APs when it enters wireless networks for the first time. The station sends the scanned channel information to AP. AP maintains the neighbor channel table based on the information received from stations. A station performs the partial-scanning by using the table. Therefore, the proposed scheme can reduce the scanning latency.

System Architecture for Low-Power Ubiquitously Connected Remote Health Monitoring Applications With Smart Transmission Mechanism

We present a novel smart transmission technique with seamless handoff mechanism to achieve ubiquitous connectivity using multiple on-chip radios targeting remote health monitoring applications. For the first time to the best of our knowledge, a system architecture for low-power ubiquitously connected multiparametric remote health monitoring system is proposed in this paper. The architecture proposed uses a generic adaptive rule engine for classifying the collected multiparametric data from patient and smartly transmit the data when only needed. The on-chip seamless handoff mechanism proposed aids for the ubiquitous connectivity with a very good energy savings by intelligent controlling of the multiple on-chip radios. The performance analysis of the proposed on-chip seamless handoff mechanism along with adaptive rule engine-based smart transmission mechanism achieves on an average of 50.39% of energy saving and 51.01% reduction in duty cycle of transmitter taken over 20 users compared with the continuous transmission. From the hardware complexity analysis made on the proposed seamless handoff controller and adaptive rule engine concludes that they require only 2082 CMOS transistors for real-time implementation.

A dual mode self-adaption handoff for multimedia services in mobile cloud computing environment

Since mobile devices are becoming the primary platforms for many users who always roam around and access the cloud computing applications, the two concepts of mobile computing and cloud computing have emerged as a new widely accepted paradigm, mobile cloud computing. More and more users use cloud computing service and offload their local applications to the cloud. Unfortunately, developing mobile multimedia cloud services over heterogeneous wireless networks poses a challenge for service continuity. The degraded link quality and connection losses are likely to happen and these may affect service availability and service usage times in mobile cloud computing scenarios. To improve handoff quality and minimize utilized bandwidth, we propose a dual mode self-adaption handoff mechanism for multimedia services in mobile cloud computing environment. The new mechanism uses multipath transmission for media flows based on "make before break" technology, and consists of the duplicate mode and the effective mode, which are changed according to the network condition. Analytic model and simulation are developed to investigate our new mechanism. The results demonstrate that the self-adaption handoff mechanism can realize seamless handoff for multimedia services in cloud, reduce the packet loss rate, as well as obtain a more efficient use of the scarce wireless bandwidth and the power of mobile devices.

A Fast Handoff Scheme for Streaming Service in Wireless Sensor Networks

The IEEE 802.15.4 standard is a rapidly growing technology for short-range communications and low rate Wireless personal area networking. The standard has been widely accepted as the de facto standard for wireless sensor network (WSN) because of its low cost deployment and remarkable applications. The mobility management in the existing WSN has highly suffered from different issues like high packet loss and delay because the current mobility management in IEEE 802.15.4 lacks the support of handover management for real-time streaming applications. In this paper, we propose a new fast handoff mechanism which eradicates the scanning delay. The proposed scheme uses the information of link quality (LQ) of the neighboring coordinators (COs), and on the basis of this information it selects an appropriate CO for handoff. The proposed scheme is evaluated through extensive simulations which show its strength and accuracy in the context of switching of high streaming data from one CO to another.

QualityScan scheme for load balancing efficiency in vehicular ad hoc networks (VANETs)

The main terminal devices in vehicular ad-hoc networks (VANETs) are highly mobile moving cars that handoff much more frequently than handheld devices. Nevertheless, frequent handoff or high handoff latency can influence the quality of service (QoS) of real-time network services. Since conventional handoff mechanisms cannot fulfill the requirements of VANET, many fast handoff schemes have been proposed. However, the schemes based on the signal strength of APs (access points) ignore the loading states of different APs and thus cannot utilize the bandwidth effectively. Whenever some APs are very busy, the QoS will be degraded. In order to solve this problem, we can pre-establish the APs and regulate their number according to different traffic types. In this paper, we present a fast handoff scheme for VANET, QualityScan, which decreases the handoff latency and considers loading states of the regional APs simultaneously. By the pre-established AP controller (APC), our scheme gathers the loading states of the APs regularly and predicts network traffic of the next moment. Based on the parameters obtained by passive scanning, the mobile nodes (MNs) can choose the optimal AP for the optimal QoS. According to our simulation analysis, QualityScan not only achieves load balance of the APs, but also improves QoS and handoff efficiency in VANET.

IJARCCE - Computer and Communication Engineering

3 Abstract: With technological advances in the telecommunications sector, everyone around the world would like to be connected seamlessly anytime anywhere through the best network. Making a transition from one network to another and moving between heterogeneous networks is not the only problem that worried specialists, scientific and mobile operators; the concern of QoS is as important as the handoff, The requirements like capability of the network, network conditions, handoff latency, power consumption, network cost, and user preferences must be taken into consideration during vertical handoff. Importance of inter working between architecture requires adaptive approaches to implement the vertical handoff mechanism in 4G wireless networks and produce an effective service for the user by considering handover parameters. In this paper, we analyzed the main approaches for vertical handoff to offer a systematic comparison for new researchers. The survey revealed the need for new approach which satisfy the most important requirements and reduce the HO failure probability and the number of unnecessary handover.

A Survey on Spectral Handoff Mechanisms for the Cognitive Radio Network

In a cognitive radio network, the cognitive radio (CR) devices also called as secondary users (SU's) need to change their operating frequency due to the inclusion of primary user (PU) in that frequency band. Thus when a PU arrives in a frequency band and asks for a channel in that band, it gets that band and occupies the channel which may be occupied by a SU. In this situation, the SU needs to find another channel in a different frequency band which leads to the spectral handoff. Thus in addition to the location based handoff's for the SU, spectral handoff also occur. This spectral handoff may be done several times for the SU. Thus this situation leads to the study of handoff mechanism. This paper carries out a survey of the handoff types and their mechanisms which have been already conceptualized. KeywordsCognitive Radio, handoff, spectral handoff, spectrum sensing, proactive, reactive. __________________________________________________*****_________________________________________________

Message Authentication Mechanism and Privacy Protection in the Context of Vehicular Ad Hoc Networks

Vehicular ad hoc networks (VANETs) have been widely researched in recent years. VANETs are used mostly for road safety and traffic efficiency; therefore, it is imperative that the communication between vehicles is rapid and secure in a VANET environment. In the present study, bilinear pairings were used to construct a complete message authentication scheme. This scheme provided the following features: (1) vehicle or roadside unit (RSU) parameters were determined via a hierarchical protocol, which prevented potentially a large computational overhead for a single node; (2) message broadcasts and private communications between vehicles in the transmission range of the same RSU were enabled; (3) message broadcasts and private communications between vehicles in the transmission ranges of different RSUs were enabled; (4) a fast handoff mechanism was established for vehicles in the transmission ranges of different RSUs; and (5) mechanisms for message broadcasts and private communication were established for vehicles in areas where RSUs were sparsely located. Based on the experimental results, our scheme was confirmed to be superior to previous schemes. In terms of security, our scheme offered the following features: confidentiality, message integrity, nonrepudiation, conditional anonymity, and conditional untraceability.

VECOS: A Vehicular Connection Steering Protocol

Due to their worldwide deployment, 3GPP mobile networks, particularly Long-Term Evolution (LTE), are gaining a lot of momentum, as are LTE-connected vehicles. While one may envision an LTE-connected vehicle as a nicely designed vehicle with sophisticated equipment, a conventional vehicle with a person using an LTE-enabled smartphone or tablet on board can be logically qualified for an LTE-connected vehicle. Maintaining an acceptable quality of service (QoS)/quality of experience (QoE) of LTE services for a user on board a moving vehicle is a challenging problem. One approach for that is to anticipate QoS/QoE degradation and to exploit the different radio access technologies, such as WiFi, that may be available at an LTE-connected vehicle or, in general, at an LTE-enabled user equipment (UE) on board the vehicle. For this purpose, this paper introduces a complete framework that proactively defines QoS/QoE-aware policies for LTE-connected vehicles (UE devices) to select the most adequate radio access out of the available access technologies (e.g., WiFi and LTE) that maximizes QoE throughout the mobility path. The policies are communicated to the users following 3GPP standards and are enforced by the UE devices. They take into account the service type, the mobility feature, and the traffic dynamics over the backhauls of the different available accesses. Two different models were proposed to model the network selection process. The first model is based on multiple-attribute decision making (MADM) techniques, whereas the second model is based on the Markov decision process (MDP). Moreover, the network selection process is modeled using a time-continuous Markov chain, and the performance of the proposed framework (VECOS) is extensively evaluated through NS2-based simulations considering the case of two wireless access technologies, namely, WiFi and cellular networks. The obtained results illustrate that in comparison with conventional vertical handoff mechanisms whereby WiFi is always selected whenever it becomes available, the proposed framework ensures better QoS and achieves better QoE throughout the time of the received service and the mobility path of the user, even in the case of errors in the prediction of the user's mobility.

Seamless Service Handoff Based on Delaunay Triangulation for Mobile Cloud Computing

Mobile cloud computing is a promising technique that shifts the data and computing service modules from individual devices to a cloud architecture. When the service is executed in the cloud clone, the data transfer between the mobile terminal (MT) and its clone requires low end-to-end communication delay. However, it is very difficult to predict the speed and direction of an MT in a timely fashion. Thus, the service handoff between different access points (APs) may cause long handoff delay. To address this issue, we propose a proactive service handoff mechanism using the Delaunay triangulation (called as DTSHM mechanism). The DTSHM constructs all the APs into a Delaunay triangulation topology. For an MT located in a Delaunay triangle, its next handoff procedure only happens between the three vertices (i.e. APs) of this triangle no matter how it moves. It is because the circumcircle of each Delaunay triangle does not contain any other APs in its interior. Thus, a Delaunay triangle is characterized as the master-standby service model which is composed of a master AP and two standby APs. In the DTSHM, The cloud clone in advance authenticates and buffers the required data packets of an MT in the standby APs. Thus, the clone can quickly handoff the cloud service from the source AP to the target AP when the handoff process is triggered. The simulation results and the performance analysis show that the DTSHM works very well.

MRPL: Boosting mobility in the Internet of Things

The 6loWPAN (the light version of IPv6) and RPL (routing protocol for low-power and lossy links) protocols have become de facto standards for the Internet of Things (IoT). In this paper, we show that the two native algorithms that handle changes in network topology – the Trickle and Neighbor Discovery algorithms – behave in a reactive fashion and thus are not prepared for the dynamics inherent to nodes mobility. Many emerging and upcoming IoT application scenarios are expected to impose real-time and reliable mobile data collection, which are not compatible with the long message latency, high packet loss and high overhead exhibited by the native RPL/6loWPAN protocols. To solve this problem, we integrate a proactive hand-off mechanism (dubbed smart-HOP) within RPL, which is very simple, effective and backward compatible with the standard protocol. We show that this add-on halves the packet loss and reduces the hand-off delay dramatically to one tenth of a second, upon nodes’ mobility, with a sub-percent overhead. The smart-HOP algorithm has been implemented and integrated in the Contiki 6LoWPAN/RPL stack (source-code available on-line mrpl: smart-hop within rpl, 2014) and validated through extensive simulation and experimentation.

Distributed multi-agent scheme support for service continuity in IMS-4G-Cloud networks

In this study, the Quality of Service (QoS) needed to support service continuity in heterogeneous networks is achieved by a Distributed Multi-Agent Scheme (DMAS) based on cooperation concepts and an awareness algorithm. A set of problem solving agents autonomously process local tasks and cooperatively interoperate via an in-cloud blackboard system to provide QoS and mobility information. A Q-Learning awareness algorithm calculates the exceptive rewards of a handoff to all access networks. These rewards are then used by problem solving agents to determine what actions must be performed. Agents located in the integrated IMS-4G-Cloud networks handle service continuity by using a handoff mechanism. Through operations and cooperation among active agents, these phases select a policy for predictive and anticipated IP Multimedia Subsystem (IMS) handoff management. Compared with conventional IMS handoff management, the proposed DMAS scheme achieves shorter handoff delay and better QoS for real-time service applications.