Handover Management - an overview (2022)

Mobile and Wireless Networks

Dong-Wan Tcha, in Encyclopedia of Information Systems, 2003

IV.D.2. Handoff Management

Hand-off (or handover) management for maintaining connection with mobile terminals is a three-stage process. The first stage involves initiation of identifying the need for hand-off, and at the second stage new resources for the hand-off connection must be found and any additional routing operations must be performed. Under the network-controlled hand-off (NCHO), or mobile-assisted hand off (MAHO), the network takes control of the procedure while the mobile terminal does the job for the mobile-controlled hand-off (MCHO). The final stage is data-flow control, where the delivery of the data from the old connection path to the new connection path is maintained according to agreed-upon service guarantees. The hand-off management operations are presented in Fig. 9.

Handover Management - an overview (1)

Figure 9. Handoff management operations. (Note: Akyildiz, “Mobility management in next generation wireless system.”)

Hand offs are of two kinds depending upon the condition under which they take place: intracell hand off and intercell hand off. Intracell hand off occurs when the user's call has to be transferred to a new radio channel of appropriate strength at the same BTS due to the deterioration of the present channel's signal strength. Intercell handoff occurs when the user moves into an adjacent cell and all of the terminal's connections must be transferred to a new BTS.

Handoffs can be distinguished between the soft and hard based on the signaling diversity kept throughout the operation. During the soft hand off, a terminal is connected to multiple BTS simultaneously and uses some form of signaling diversity to combine the multiple signals. In the hard hand off, on the other hand, a terminal stays connected to only one BTS at a time, clearing the connection with the former BTS immediately before or after establishing a connection with the target BTS.

Research issues on systems management for hand off are minimizing the signaling load on the network, optimizing the route for each connection, and efficient bandwidth reassignment. These issues including the ones on the air interface are listed in Figure 9.

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Introduction to Mobile Broadband Wireless Access

Sassan Ahmadi, in Mobile WiMAX, 2011

1.2.1 Evolution of the IEEE 802.16 Standards

The amendments and revisions of the IEEE 802.16 standard have preserved the essence of their base standards. Various physical layers were combined with the original IEEE 802.16 standard medium access control protocols (i.e., single carrier, OFDM 256, and OFDMA physical layers); however, depending on the capabilities of the physical layer, some changes in the data link layer protocols were made (e.g., handover and power management schemes were added to support mobility in IEEE 802.16e). The principles of IEEE 802.16 data link layer protocols were inherited from DOCSISvii standard. While this philosophy might have worked well for the fixed versions of the IEEE 802.16 standard, it has caused some inefficiency in support of mobility in the later amendments/revisions of the standard. The evolved IEEE 802.16 standards have not necessarily maintained backward compatibility and interoperability with their legacy base standards (e.g., IEEE 802.16e-2005 was not backward compatible with IEEE 802.16-2004).

Table 1-4 provides some useful information on the evolution of the IEEE 802.16 standards (already released or under development by the IEEE 802.16 Working Group as of September 2010) with hyperlinks to additional information sources. The IEEE 802.16-2009 standard is the second revision of the IEEE 802.16 standard (the first revision was released as IEEE Std. 802.16-2004) that encompasses the previous amendments and corrigenda released by this working group. This revision serves as the base standard for IEEE 802.16m, the advanced air interface, which is currently under development in the IEEE 802.16 Working Group whose release is expected in March 2011.

The IEEE 802.16-2009 standard [8] contains some feature enhancements relative to the IEEE 802.16e-2005, including Frequency Division Duplex (FDD) mode enablement and bug fixes, Half-Duplex FDD terminal operation, persistent scheduling, support of 20 MHz bandwidth, improved multi-antenna transmission and processing schemes, and enhancement of multicast and broadcast services, multi-radio coexistence, location-based services, as well as load balancing. The use of complementary grouping of the mobile stations and use of two resource allocation medium access protocols per radio frame resulted in higher VoIP capacity and lower airlink transmission latency.

Relaying and cooperative communication have emerged as important research topics in wireless communication in the past few years to improve performance and coverage of wireless links. In May 2006, the IEEE 802.16 Working Group assigned a task group to incorporate relay capabilities in the IEEE 802.16e-2005 air interface standard. The IEEE 802.16j task group finalized the multi-hop relay specification in 2009. Although this amendment is fully compatible with 802.16e-2005 mobile stations over the access link (i.e., the link between the relay and mobile stations), an IEEE 802.16j compliant base station is required for relays to operate over the relay links (i.e., the link between relay and base stations). Furthermore, due to the incorporation of various inconsistent optional features and functionalities, a relay system profile (i.e., a set of consistent functional components to form a working system) needs to be developed outside the IEEE to enable industry-wide implementation and deployment.

Since January 2007, the IEEE 802.16 Working Group has embarked on the development of a new amendment of the IEEE 802.16 standard (i.e., IEEE 802.16m) as an advanced air interface to meet the requirements of ITU-R/IMT-Advanced for 4G systems, as well as the next generation mobile network operators. Depending on the available bandwidth and multi-antenna mode, IEEE 802.16m systems will be capable of over-the-air data transfer rates in excess of 1 Gbit/sec and support of a wide range of high-quality and high-capacity IP-based services and applications while maintaining full backward compatibility with the existing mobile WiMAX systems (to preserve investments and continuing support for the first generation products). The IEEE 802.16m will be suitable for both green-field and mixed deployments with legacy mobile stations and base stations. The backward compatibility feature would allow upgrades and evolution paths for existing deployments. It will enable roaming and seamless connectivity across IMT-Advanced and IMT-2000 systems through the use of appropriate interworking functions. The IEEE 802.16m systems further utilize multi-hop relay architectures for improved coverage and performance.

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LTE and 5G systems

E. Kammoun, ... M.S. Obaidat, in Smart Cities and Homes, 2016

1 Introduction

Mobile communications systems revolutionized the way people communicate, and cooperate. During the past few decades, the telecommunications field has witnessed a marvelous evolution that impacted all aspects of our life. Since the appearance of the first generation (1G)—Analog Cellular Telephony— during the 1980s, mobile industry has witnessed a continuous evolution almost each decade. Each generation introduced new technologies and new architectures. These systems perform ubiquitously and conventionally and are spread worldwide. Thus, this work summarizes the recent cellular network evolution as shown in Fig.6.1 and specifies the handover management in detail.

Handover Management - an overview (2)

Figure 6.1. Cellular Network Evolutions

The formation of Third-Generation Partnership Project (3GPP) [1] happened in 1998, with an intention to support the development and maintenance of the radio access technologies starting from the Global System for Mobile Communications (GSM) and GSM evolved technologies such as General Packet Radio Service (GPRS) and Enhanced Data Rates for GSM Evolution (EDGE). Moreover, the 3GPP Long-Term Evolution-Advanced (LTE-A) recently emerged. There are promises to offer significant improvements over previous technologies such as Universal Mobile Telecommunications System (UMTS) and High-Speed Packet Access (HSPA) by introducing a novel physical (PHY) layer and reforming the core network (CN) [2].

Lately, the telecommunications field went beyond the existing mainstream radio access technologies cited earlier in order to introduce a new system based on the UMTS evolution entitled LTE-A that is going to promote modern concepts such as Smart Cities and the Internet of things (IoT) during the next few years. The IoT is essentially based on connecting Smart objects and aims to vigorously interconnect devices and consequently cities in the physical world alongside with the digital one. Thus this emerging concept enables a huge number of diverse and diversified end systems to exchange data using All-IP–based networking mobility.

Mobile devices such as PCs and smartphones are evolving largely since they are the most useful and suitable means of communication that are not limited by place and time. So, having a continuously connected environment and being surrounded by actively smart and intelligent devices is definitely going to revolutionize human beings’ daily life in the next years with the evolution of Mobile Cloud Computing (MCC), Device-to-Device (D2D) communications, Multi–Radio Access Technologies (Multi-RATs) Heterogeneous Networks (HetNet), RFID applications, and Wireless Sensor Networks (WSN), among others. For example, WSNs enable the collection, processing, analysis, and dissemination of valuable information, gathered in a variety of environments [3]. For all the reasons cited earlier, researchers have been recently focusing mainly on the Next-Generation Networks (NGNs) that are the fourth generation (4G) and also known as LTE-A, which are capable of overcoming the bandwidth limitation because they can significantly increase bandwidth capacity for subscribers. The 4G network is capable of providing up to 100Mbits/s (for “LTE-A” standard) and 128Mbits/s (for “WirelessMAN-Advanced” standard) for mobile users, whereas the current third-generation (3G) network supports a maximum of 14.4Mbits/s [4]. It is indisputable that they can operate independently from the used heterogeneous technology as well as from the time and place limitations. It is undeniable that both LTE and the Worldwide Interoperability for Microwave Access (WiMAX) are promising technologies that offer minor latency and superior transfer rates in order to bring the customers’ needs to completion. In this manner, one of the major and necessary requirements is providing the most adequate and satisfactory Quality of Service (QoS) especially for real-time applications. LTE is an all-IP packet system where guaranteeing QoS is a real challenge [5]. It promises to increase the transmission capacity, able to offer the same bandwidth for further users, and provide higher data rates to the same number of users. In addition, the reduction of the interval of data transmission, known also as latency, would significantly improve the responsiveness of the network. Finally, LTE is expected to consume less energy than UMTS, especially at the terminal; its autonomy is thereby extended, despite the connection to a broadband data service.

The first phase of the LTE standardization work is to define the requirements that must be satisfied. In summary, the major goal of LTE is to improve the data services support through increased capacity, upgraded data rates, and reduced latency. In addition to these performance requirements, 3GPP also defined functional prerequisites such as the spectral flexibility and mobility with other 3GPP technologies. It is doubtless that monitoring the QoS is critical for the operator to ensure a satisfactory user experience. That is why the main purpose of LTE technology is to provide diverse servants with various QoS requirements. Thus, LTE network offers differentiated QoS mechanisms to facilitate the consideration of the various service constraints. Mobile services can be distinguished according to two main criteria, often interrelated. These service features involve a differentiated network support. Understandably, processing a voice call will not impose the same constraints as downloading a file. In general, the real-time services (eg, voice or streaming video calls) require short transmission times, but can tolerate transmission errors. In contrast, non–real-time services (eg, a download of electronic mail or file) can tolerate speed constraints but do not tolerate transmission errors.

The next section of this chapter outlines a general overview of the cellular network evolution and specifies in particular the wireless 4G networks. Moreover, the horizon of implication of the upcoming and universal fifth-generation (5G) mobile technology is detailed. Because of the gradually growing demand for a richer communication environment that is characterized by higher data rates and mobility enabling people and things to be connected at anytime and anywhere, our main focus will be devoted on studying the 5G systems.

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An overview of vertical handover decision strategies in heterogeneous wireless networks

Meriem Kassar, ... Guy Pujolle, in Computer Communications, 2008

Handover management issues include mobility scenarios, metrics, decision algorithms and procedures. Mobility scenarios can be classified into horizontal (between different cells of the same network) and vertical (between different types of networks). In homogeneous networks, horizontal handovers are typically required when the serving access router becomes unavailable due to MT’s movement. In heterogeneous networks, the need for vertical handovers can be initiated for convenience rather than connectivity reasons (e.g., according to user choice for a particular service). Two of the major challenges in vertical handover management are seamlessness and automation aspects in network switching. These particular requirements can refer to the Always Best Connected concept, of being connected in the best possible way in an environment of multiple access technologies, according to policies (expressed by rules based on parameters such as network conditions or user preferences) [3]. For that, a handover management technique must choose the appropriate time to initiate the handover and the most suitable access network for a specific service among those available, and must maintain service continuity.

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A survey of handover management in LTE-based multi-tier femtocell networks: Requirements, challenges and solutions

Győző Gódor, ... Sándor Imre, in Computer Networks, 2015

6 Conclusion

Efficient handover management is crucial in cellular networks extended with small cells enabling multiple coverage and thus increased capacity in certain geographical areas. In this article, we surveyed the requirements, challenges and solutions related to handover management in LTE-based Multi-tier Femtocell Networks. The presented various results and solutions shore up the expectations that current standardized solutions can be improved. These new methods, however, attacks certain phases of the handover process to enhance QoS and QoE by controlling and decreasing packet loss and delay. The most challenging actual question in this context is how to combine these results partly or entirely to build a complete and more efficient solution.

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Collaborative Computing and Applications

Ibrahim Al-Surmi, ... Borhanuddin Mohd Ali, in Journal of Network and Computer Applications, 2012

3.2 Handover management

Handover management concerns about allowing the network entities to maintain the MNs communications while moving and changing their points of attachment over the network. In addition, handover management provides uninterrupted access to the information by monitoring and controlling the overall MN's handover process. The handover management process can be divided into three main steps (Liu et al., 2008):

1.

When and why steps” refer to the situation when the MN must switch to a new network. This step corresponds to the process events when the MN receives an event notification (e.g., signal strength power, signal-to-interference ratio, channel quality, bit error rates, etc.) from underlying technology (e.g., IEEE 802.11, 1997; IEEE 802.16e, 2004; IEEE 802.21, 2008; etc.), which indicates that the MN must operate on another network access.

2.

Where step” refers to which network the MN must make for its next transition. In this step, the MN should decide on which network it will operate, depending on some available parameters (e.g., network load, available bandwidth, quality of service, user preferences, etc.).

3.

How step” refers to how the MN moves between network domains. It defines the handover execution and how the MN performs the handover movements, either horizontal handover or vertical handover, as described in Table 2.

Table2. Vertical vs horizontal handover characteristics.

CriteriaVertical handoverHorizontal handover
OccurrencesMN roaming across heterogeneous access technologyMN roaming within homogenous access network
Mobility regionGlobal mobilityLocal mobility
IP addressThe IP address change, since the network interface changeThe IP address does not change, since the network interface is the same
ExampleUMTS-WLAN or WLAN-WiMAXGSM-GSM or WLAN-WLAN

In addition, some related aspects for the handover management such as handover strategies, situations and handover categories are presented in the following section.

3.2.1 Handover strategies

Handover strategies play an important role in the handover management. This is done by maintaining continuous communication with the MN while it moves from one access link to another in the network. The handover strategies are classified into two cases: hard handover and soft handover. Hard handover is considered to happen when the MN loses its connection with the current access link and then establishes a new connection with a new access link in the network. This type of handover causes an interruption to the MN's communication session due to the high handover latency and packet loss. A soft handover is considered to happen when the MN set up a connection with a new access link while still keeping the connection to the old access link in the network. This handover type preserves the MN's communication session continually and reduces handover latency and packet loss. A summary comparison for the handover strategies and their advantages and drawbacks are shown in Table 3.

Table3. Hard handover vs Soft handover strategies characteristics.

CriteriaHard handoverSoft handover
OccurrencesAn MN loss its current AP's connection and then begins to search for a new access linkAn MN has simultaneous connections to both old and new access links

Technology used“Break-Before-Make” which breaks the current connection before setting up the new one“Make-Before-Break” which makes a new connection before breaking the old one

Session continuityNot supportedSupported

Mobility regionGlobal/localGlobal/local

Handover typeVertical/horizontalVertical/horizontal

Handover latencyHighLess

Packet lossHighLess

Additional entityNot requiredRequired


ComplexityLessHigh

Resource utilizationLess utilizationMore utilization

In order to fulfil the requirements for both real-time and non-real-time sensitive services, the handover management strategies depend on the underlying technology support and on different characteristics and purposes for performing handover mechanisms, such as fast, smooth and seamless handovers. In the case of a fast handover, the reduction of handover latency during the MN's movements is the main design concern, with small packet loss. In the smooth handover case, the main concern is to reduce packet loss by avoiding longer forwarding time for the data packets. In the seamless handover case, the main interest is to fulfil the handover to satisfy and support the quality of service and user preferences.

In order to perform a typical handover there are three main operation phases (Akyildiz et al., 1999), as follows:

1.

Handover initiation phase: in order to search for the new access link for MN, the network entity has to identify the needs for the handover. This is done by discovering an available access link, selecting an appropriate link, finally, making handover negotiation with the new access link.

2.

Handover preparation phase: concern the link layer connectivity setup and IP connectivity. The key role in the handover preparation is the handover decision (i.e., the process of deciding when the handover must be performed). It uses a general metric (i.e., signal strength power, signal-to-interference ratio, channel quality, bit error rates, etc.) to assist the decision algorithm. The handover decision is executed according to the demand of the handover mechanisms (i.e., fast, smooth and seamless handovers).

3.

Transfer connection phase: once the network identifies the need for the handover and makes its preparations, it starts the handover execution phase by transferring a handover signalling, context transfer and data packets from the previous point of the attachment path of the MN to the new path in order to continue the MN's data sessions.

3.2.2 Handover situation

The scenario of the handover situation takes place in the two layers of the OSI reference model (Zimmermann, 1980, i.e., link layer and the network layer). In addition, the link layer (L2) handover occurs when the MN's access link connection changes from one access point (AP) to another access point (i.e., changing the beacon signal not the MN's subnet routing address). This layer includes all IEEE 802 family technologies (e.g., IEEE 802.11, IEEE 802.16e, etc.).

However, the network layer (L3) handover occurs when the MN moves out from current subnet range and re-configures its IP address through exchanges of the Router Solicitation (RtrSol) and Router Advertisement (RtrAdv) messages towards the new access router (AR) that is advertising the new subnet address or based on other methods (i.e., changing the MN's routing reachability address). This layer includes all the IP protocol family (e.g., IPv4, IPv6, etc.). Table 4 shows a summary comparison between the two handover situations along with their own technology aspects.

Table4. Comparison between L2 and L3 handovers situations.

CriteriaL2 handoverL3 handover
OccurrencesWhenever a MN's link layer connection changes from one access point to anotherWhenever a MN moves outside current subnet range and changes its access router
OSI layerLink layerNetwork layer
Access entityAccess point (AP)Access router (AR)
Technology802 familyIP family
DiscoveryScanningRtrSol/RtrAdv messages
Handover initiatedWhen MN receives strong signal strengths (beacons)When MN receives new RtrAdv to configure a new IP address
ConfigurationExtended service set (ESSID)Auto-configuration
Media routingInter access point protocol (IAPP)Encapsulation tunnelling

3.2.3 Handover categories

The handover management can be categorized into two types of method: reactive method and proactive/predictive method. In the former reactive method, the handover procedure is initiated after the MN attaches to the new location (Han et al., 2006). Accordingly, the network layer (L3) handover (as explained in Section 3.2.2) starts after the completion of the link layer (L2) handover. Therefore, this reactive method is considered as a hard handover strategy (as explained in Section 3.2.1), which is simple in the signalling and does not require an underlying technology support in order to execute the handover situation. However, it causes connection disruption and packet loss during the MN's handover.

(Video) Project Handover Process [OVER TO YOU!]

In contrast, the latter proactive method utilizes predictive information about the new location to establish a data forwarding path between the current and new access routers before the MN's movement (Mishra et al., 2004). Accordingly, the network layer (L3) handover procedure takes place before the occurrence of the link layer (L2) handover of the new access link. Therefore, this proactive method is considered as a soft handover strategy, which provides a continued connection with less disruption time and packet loss than the reactive method. However, some drawbacks are associated with this method, such as signalling overhead and erroneous movement; more details can be found in Schmidt and Wahlisch (2005). Table 5 provides a brief comparison between the reactive and proactive methods to support a seamless handover.

Table5. Reactive vs proactive handover categories.

CriteriaReactive handoverProactive handover
OccurrencesStart L3 handover procedure after L2 handover has completedStart L3 handover procedure before the L2 handover complete
Handover initiatedAfter MN being switched to the new wireless linkBefore MN switches to the new wireless link
Access entityNew ARPrevious AR
DrawbacksLong connection disruption and high packet lossErroneous movement and signalling overhead
Structure supportSequentialSimultaneous
Technology dependentNoneRelies on L2 trigger event

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A review on interworking and mobility techniques for seamless connectivity in mobile cloud computing

Abdullah Gani, ... Suleman Khan, in Journal of Network and Computer Applications, 2014

3.3.2.2 Handover management

Handover management enables the wireless communication network to maintain communication with mobile node and lower the service disruption while moving and changing its PoA. Handover occurs in two scenarios: (a) whenever mobile node moves from one location to another location either homogeneous or heterogeneous wireless networks and (b) whenever, current network PoA is changed as current serving network is not capable to satisfy the desired QoS/QoE (Zekri et al., 2012). Handover management includes monitoring and controlling of handover process considering the random nature of wireless networks to provide uninterrupted service continuity to the user. A handover process involves three steps: initiation which is initiated either by network or by the mobile node, new connection generation, and data flow control. There are mainly four types of handover strategies: network-controlled handover (NCHO), network-assisted handover (NAHO), mobile-controlled handover (MACO) and mobile-assisted handover (MAHO) (Akyildiz et al., 1999). In NCHO and MAHO, the new connection is established by the network.

In all-IP mobile network, handover occurs in different levels of OSI reference model: network layer and link layer (Zimmermann, 1980). Network layer handover occurs whenever a mobile node moves from one subnet to another subnet, whereas data link layer handover occurs whenever mobile node moves from one access point to another access point. The handover techniques are categorized as a proactive and reactive. In proactive method the mobile or network predict the new location to establish data forwarding path before initiating the handover process in order to provide a smooth communication environment between nodes (Al-Surmi et al., 2012). Whereas, in reactive method, the handover procedure starts after mobile node is attached with new location which introduce handover delay. Hard handover is initiated whenever mobile node lose communication with current point of attachment which is undesirable for network intensive application like distributed application processing, collaborative processing. In soft handover mobile node establish a connection with new location before releasing the current point of attachment to provide service continuity (Zekri et al., 2012). Based on diversity in networks in terms of technology, handover is categorized as a horizontal handover and vertical handover. Horizontal handover occurs whenever a mobile node roams within same networks or same domain and vertical handover occurs whenever mobile node roams within heterogeneous network or between different domains (Al-Surmi et al., 2012). The main consideration criteria for VHO decision is shown in Fig. 4 (Zekri et al., 2012).

Handover Management - an overview (3)

Fig. 4. Handover decision criteria.

In heterogeneous wireless networks, vertical handover (VHO) is an important issue for providing a seamless mobility between diverse network environments. It is considered as a fundamental feature of all next generation all-IP mobile network endeavors. Vertical handover procedure consists of three main functions: system discovery, handover decision and handover execution. Vertical handover decision is important for providing a low cost, highly available network environment for achieving the desired QoS or QoE.

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A mobile internal vertical handover mechanism for distributed mobility management in VANETs

Livinus Tuyisenge, ... Lissan-Eddine Afilal, in Vehicular Communications, 2020

7 Conclusion and perspectives

Vertical handover is one of the key technologies that will enable the connected and autonomous vehicles deployment. In this paper, we have proposed a vertical handover management approach, which reduces the Binding Update time by eliminating the setup time. Our proposed approach improves the handover performances thanks to the anticipation of the next handover by connecting simultaneously to different available networks using the PMIP-HD architecture. Our approach also takes benefit from a proposed logical interface in order to maintain the connectivity session. We have proposed and described the implementation of the proposed PMIP-MIVH vertical handover management in VANETs context. Numerical analysis shows that our proposed approach outperforms the existing mobility management schemes. We also highly focus our attention on the implementation and simulation of the proposed solution using the well-known and most used Network Simulator version 3 (NS3). We have described and conducted thoroughly the performance metrics in terms of packet delivery ratio (PDR), packet error rate (PER), delay, jitter and throughput. We have varied the number of UEs in order to test the scalability of our approach in a highway scenario. The simulation results confirmed the analytical ones. They show that our proposed PMIP-MIVH outperforms the existing solutions.

Furthermore, we extended our simulations by considering an urban mobility scenario using the SUMO traffic modeling tool. We exported the mobility of the Reims city in France from OpenStreetMap in order to deepen the performance test of our proposed model. The results of the urban mobility consolidate the results of the highway mobility simulations. Moreover, both of these simulations results validate the analytical results. They all show that our approach outperforms the existing solutions in terms of handover management in VANETs field.

As perspectives, our future works will focus on designing a testbed in order to evaluate this solution in more realistic scenario and consider more real-time parameters and requirements. We also intend to design a more efficient handover decision algorithm to enhance the performances of this logical interface-based approach.

Furthermore, we will design and implement the flow mobility mechanism in order to efficiently use the resources when the dual (or multiple) connections are available for long time. Due to the number of collisions that occur in dense simulations, we will also direct our future works to look for an inclusion of a collision avoidance algorithm in order to increase the reception ratio in high density environment.

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Progression on spectrum sensing for cognitive radio networks: A survey, classification, challenges and future research issues

Mani Shekhar Gupta, Krishan Kumar, in Journal of Network and Computer Applications, 2019

2.3.4 Spectrum mobility

Unlike existing wireless networks, the handover does not only execute due to movement of SUs but also due to the presence of PUs. Mostly, the SUs are considers as visitors to an available spectrum bands in different networks. Thus, the SUs require to switch between available vacant channels seamlessly. It is termed as spectrum mobility. Two key operations are spectrum handover and connection management (Akyildiz et al., 2008; Kumar et al., 2017b). The operation of spectrum handover performed with handover parameters collection, handover initiation and handover execution (Han et al., 2010). An appropriate spectrum handover technique is selected in this stage. In (Hou et al., 2013; Kumar et al., 2016), various handover techniques are discussed for spectrum mobility. A break-less connectivity is required for seamless handover. Due to the absence of centralized controlling entity in distributed CR networks, the handover and connection management becomes more complex (Nejatian et al., 2013).

Some other common aspects related to spectrum management framework includes mode of operation (hopping/non-hopping), spectrum (licensed/unlicensed), artificial intelligence, mobility, type of CR networks (centralized/distributed), the number of SU (single/multiple), and antennas may be single/multiple (i.e. Multiple Input Multiple Output (MIMO) systems).

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A survey on applications of IEEE 802.21 Media Independent Handover framework in next generation wireless networks

Behrouz Shahgholi Ghahfarokhi, Naser Movahhedinia, in Computer Communications, 2013

6 Comparative summary

In this section, a comparative summary of representative methods introduced in this paper is presented. This summary discusses the common trends and also differences in some of the methods represented in various aspects of MIH employment. This section begins with a summary on employment of MIH to improve the performance of mobility management methods. Table 2 shows the list of some representative methods already discussed in Section 3. A comparison on methods that are used to improve the performance of MIP family shows that eliminating the access router discovery is the common improvement in these methods (except PMIPv6 which does not need access router discovery). MIIS is used to obtain L3 information of candidate access network instead of discovery procedure. Also, Link Going Down (LGD) event is frequently used to indicate the handover procedure in these methods. Checking for availability of resources in candidate access network is another important note which only some of the works such as [14] have considered it.

Table 2. Summary of representative MIH-based mobility management methods.

MethodApplication areaEmployed MIH servicesAdvantages/improvementsDisadvantages/shortcomings
Kim and Jang’s method[12]MIPv4MIES (LGD)
MIIS

Omitting solicitation/advertisement procedure

Removing ping-pong effect in overlap areas

Missing details of how the HA obtains information about new access network

Missing the method of how to select between neighboring networks

Missing IS server

Kim et al.’s method[14]FMIPv4MIES (LGD)
MIIS

Check for availability of QoS requirements in candidate PoAs

Removing RtSolPr/PrRtAdv

A fast L2 handover for 802.11 by reducing scanning time

Missing details of target selection algorithm

Mussabbir et al.’s method [17]FMIPv6MIES
MIIS
MICS

Definition of a new IE container for L2 and L3 information about neighboring PoAs

Removing access router discovery

A local information cache to reduce information access time in MIIS

Definition of new MIES and MICS primitives to access QoS requirements of applications

Extension of some MICS primitives to obtain QoS parameters from PoAs

Lack of target selection method

Huang and Wu’s method [18]FMIPv6 over 802.16 networkMICS
MIES
MIIS

Removing router discovery procedure

Eliminating wrong handoff anticipation by applying 802.16e handover indication messages

Employing idea of PBF

The MICS and MIIS primitives used in their method are not determined clearly

Missing target selection algorithm

Magagula et al.’s method [23]PMIPv6MIES

MN triggers MAG with MIES (e.g. LGD) to accelerate the tunnel establishment

Chen et al.’s method [27]SCTPMIES

Employing LGD event to accelerate the change of primary path before link break

Employing Link Down and Handover Complete events to perform DEL IP and ADD IP commands

Lack of interface selection algorithm

Rouil et al.’s method [26]SCTPMIES
MICS

Fast movement detection based on LGD event to change the primary path

Employing SCTP to transfer MIH messages accurately and discriminately

An interface selection algorithm has been proposed

Al Mosawi et al.’s method [35]SIPMIIS
MIES
MICS

Employing LGD to antedate the target selection procedure

Exploiting MIIS to discover the neighboring access networks information

Check for availability of resources in candidate access networks using MICS

The IP mobility procedure has not been considered clearly

The method starts SIP register procedure after Link Up event without considering how the new IP is obtained

Jung et al.’s method [34]SIPMIES
MICS

LGD event has been exploited to trigger the handover decision and QoS renegotiation before link break

MICS primitives have been utilized to check for the availability of QoS resources in candidate access networks

Missing details on target selection which is important for QoS provisioning

Yee et al.’s method [37]SIPMIES
MIIS

LGD event has been employed to trigger the handover procedure before link break

MIIS is exploited to help the handover decision for target selection based on available bandwidth

a method to reserve bandwidth for SIP sessions in IS and to manage the utilized bandwidth of access networks

Details of modification on MIH_Get_Information primitive is not clear

Their enhanced IS assumes that MN selects the access network with maximum available bandwidth while other parameters may be effective in target selection

Comparing the methods that employ the MIH to improve the performance of SCTP shows that LGD is commonly used for fast movement detection and primary path change. Similarly, the proposed improvements on SIP have exploited LGD to antedate the handover procedure. Also, MIIS has been utilized in some of the SIP-based mobility management methods to obtain information about neighboring access networks which is used for target selection. A common shortage with most of the improvements in mobility management protocols is the lack of the target selection algorithm.

The next summary is on global methods that are employing MIH in handover decision and management. Table 3 shows a summary of the representative methods investigated in this paper and their pros and cons. Some of these methods are only focused on interface selection, meaning that they only exploit MIH services to select between different access technologies (e.g. [40] and [8]). Another shortage of some of the handover decision methods is that they have not utilized enough decision factors in their selection algorithms. MIES and MICS services provide facilities to obtain link information about the interfaces. However, standard MIIS service provides only static information about neighboring PoAs causing some of the selection algorithms to suffer from the lack of decision parameters. Some other works have employed MIIS to obtain dynamic information in addition to static information. However, those works have not stated any means for updating this dynamic information in their IS (e.g., [43,44]). Context awareness is a new paradigm in handover decision that emphasizes on using the greatest possible set of context parameters in decision procedure and it seems that extending MIH to get a larger set of effective parameters is necessary in improving handover decision methods.

Table 3. A summary of representative MIH-based handover management methods.

MethodApplication areaEmployed MIH servicesCharacteristics/improvementsDisadvantages/shortcomings
Mo et al.’s method[40]Interface selection (vertical)MIES
MICS
MIIS

Exploiting MIES and MIIS in interface selection and MICS for interface switching procedure

Missing a specific selection algorithm

Missing details of information used for interface selection

Cacace and Vollero’s method [8]Interface selection (vertical)MIES
MICS
MIIS

Content adaptation according to the information provided to applications through MIH services

(Video) What is Project Handover? Project Management in Under 5

Selection algorithm is only based on user provided priority of interfaces

Tawil et al.’s method [42]Distributed vertical handoverMIIS

Removes the necessity of information gathering by distributing the network selection between candidate access networks

Adds complexity to all access networks (they should support MIIS and participate in MADM-based decision method)

Signaling overhead of the method grows as the number of MNs increases compared to centralized decisions

Only cost and bandwidth are used in selection

Fu et al.’s method [43]GlobalMIIS
MIES

Handoff initiation triggers are not only from link changes (LGD), but also from applications

Their improved MADM-based target selection algorithm selects the PoA with enough QoS guarantee than best PoA to improve the utilization

MIIS is employed to provide information for target selection

Most of the information obtained through MIIS is dynamic, but the paper is missing the update procedure

Yang et al.’s method [44]GlobalMIES
MIIS

MIES and MICS are used to obtain QoS parameters of candidate PoAs

A combination of AHP and SAW methods are used for target selection based on QoS parameters of networks and importance of them

Missing details of MIES and MIIS primitives employed in their method

Missing details on how to gather and manage the information

The final discussion is on papers that have proposed amendments and extensions on MIH standard. Some of them such as [45] have proposed new structure for MIH communication model and their offer is too different from standard MIH architecture. Some others such as [17], [47–49] have proposed extensions to MIH services to improve the performance of these services in handover management. These extensions consider adding new primitives to MIES and MICS, adding new IEs in MIIS, extending Information Server capabilities, and modification of traditional primitives to improve their abilities. Amongst those extensions, providing dynamic information of access networks is a new point of interest and some of the works (e.g. [58,59,61]) have considered this requirement in MIH. The difference of those methods is in the algorithms used for retrieving dynamic information and those algorithms suffer from the trade-off between novelty of information and signaling overhead. The final set of methods are the ones proposing extensions to facilitate the MIH for special cases of handover such as simultaneous handover (e.g. [51]) and cooperative multi-hop handover management (e.g. [52]). Table 4 shows a summary of extensions proposed in representative efforts and their disadvantages.

Table 4. A summary of representative extensions on IEEE 802.21 standard.

MethodEnhancements/extensions on servicesDisadvantages/shortcomings
EMIH [45]

Making full use of client side and network side triggers and information including user context, application information and network information

New modules defined to collect triggers and information

New modules defined to decide and control the handover procedure

More different from standard MIH

The method has not introduced the details of service primitives

Missing details on how to collect and manage the information and triggers

High complexity

Lack of protocol details and communication model

Mateus and Marinheiro’s method [47]MIIS

A distributed model for automatic discovery of neighboring graphs and information about PoAs

MNs collect such information and send it to Is to update it

They have proposed a two step MIIS query/response instead of one step traditional MIH_Get_Information

All PoAs must support MIIS

Signaling overhead is imposed on MNs

Only static information is updated by this method

Missing details of new/modified MIH messages

eMIHF [49]MICS

The MICS resource querying primitives have been integrated with a timer-based resource reservation for future activations

Missing detail on evaluation of timer value

Mussabbir et al.’s method [17]MIES

MIH_APP_Parameter primitive has been defined for applications to report their required QoS parameters

Missing details of MIH_APP_Parameter and MIH_APP_Req primitives and requirements of applications to support them

Imposed signaling overhead to serving PoA per each MN’s request

Delay of querying each candidate PoA and the probability of QoS parameters’ change during this delay

MICS

MIH_APP_Req primitive has been defined to request applications for their requirements

MIH_MN_HO_Candidate_Query and MIH_N2N_HO_Query_Resources are extended to include the list of QoS requirements in querying procedure

Neves et al.’s method [58]

A new algorithm is presented for PoAs to report dynamic resource changes to context-aware IS

Small variations of the resources (e.g. due to unsteady nature of variable bit rate traffic) results in huge number of update packets when the PoAs’ resources are near the saturation

MIIS

MIH_Context_Information message is defined to transfer resource changes to context-aware IS

HANCG method [59]

The idea of handoff awareness has been proposed to update PoAs’ dynamic information in IS

The accuracy of context parameters is not guaranteed in decision time if there is no reservation mechanism for resources of PoAs

MIIS

NPoAs_Request and NPoAs_Response TLVs defined to access both static and dynamic information of neighboring PoAs from IS

MIES

Information_Update remote event is defined to be occurred in IS whenever an information update is sent by a PoA (when a new connection/ disconnection occurs through PoA)

Chiang and Lee [51]Extensions for MIH to support simultaneous handover
MICS

A new primitive to inform the IP address of MN’s PoS to the corresponding mobile node

A new primitive to inform the IP changes of MN to the PoS of the corresponding mobile node

MIIS

Two new TLVs for querying about latest IP address of the corresponding mobile node

Javaid and Rasheed’s method [52]

A multi-hop transport possibility has been proposed for MIH messages

A new reference point has been defined in MIH communication mode which represents events and commands that are issued from one MN to another MN in multi-hop deployments

A local IS in each MN that represents information to facilitate multi-hop access to infrastructure

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(Video) L11: Handoffs in Mobile Computing | Types - Inter, Intra Cell, Hard and Soft Handoff | MC Lectures

FAQs

How do you write a good handover note? ›

What to include in your handover notes
  1. A description of all your daily tasks and processes.
  2. A list of key day-to-day activities.
  3. Access to all relevant spreadsheets, documents, and files (ensure you share copies of these with existing team members so they aren't deleted or lost when your account is removed)
Nov 29, 2017

What is handover management? ›

Hand-off (or handover) management for maintaining connection with mobile terminals is a three-stage process. The first stage involves initiation of identifying the need for hand-off, and at the second stage new resources for the hand-off connection must be found and any additional routing operations must be performed.

What are the importance of handing over? ›

Why is handover important? The goal of handover is the accurate reliable communication of task-relevant information across shift changes or between teams thereby ensuring continuity of safe and effective working.

What makes a successful handover? ›

Handovers give staff the opportunity to discuss the treatment they're giving, communicate problems and concerns and ensure everyone knows exactly what's going on. By doing this, the team can prevent jobs from being missed or repeated.

How do you write a formal handover note? ›

This document should include:
  1. Detailed information on your day-to-day activities, tasks and priorities.
  2. An outline of the key points of the role.
  3. A clear outline of what is expected of your successor.
  4. A list of any essential files that will be handed over. This might include a particular contract, or work programme.

How do you write a handover letter for duties and responsibilities? ›

Dear Sir/Madam, As per your guidelines, I have handed over all my duties to Mr/Ms _____________ who is replacing me due to my resignation. And please find the acknowledgment mail received from Mr/Ms____________ and please let me know if I need to fulfill any further tasks. Thanking you.

What is handover process explain? ›

A handover is a process in telecommunications and mobile communications in which a connected cellular call or a data session is transferred from one cell site (base station) to another without disconnecting the session.

What is the handover process? ›

A 'handover' comes at the end of the project to install, construct, or modify an asset. It usually involves the client formally accepting the asset, the work area, and relevant information from the contractor.

What is handover example? ›

to give somebody else your position of power or the responsibility for something. She resigned and handed over to one of her younger colleagues. He handed over his responsibility for the firm last year. formally handing over power to the new government related noun handover.

What problems can occur during handover? ›

We have identified five core problems for the overall handover process. These are (1) insufficient system knowledge, (2) lack of domain knowledge, (3) insufficient communication, (4) inadequate documentation, and (5) difficulties in tracking changes.

What is the primary focus of the hand over report? ›

It helps the on signer to have a track of problematic machineries and machineries which requires extra care or attention.

What are the steps to follow during handover? ›

6 Steps to A Successful Handover
  1. 1)Processes over individual pieces. ...
  2. 2) Demos as documentation. ...
  3. 3) Design for admins, not just end-users. ...
  4. 4) Question assumptions and document limitations. ...
  5. 5) Build the partner's confidence. ...
  6. 6) Set expectations before the handover.
Jun 21, 2018

What is a handover checklist? ›

The Project Handover Checklist

Identifying and managing key stakeholders including the group who will receive the handover. A clear date for handover of the project. A communication plan that starts early in the life of the project and includes the target group. Change management issues and how they will be handled.

What is the purpose of a handover document? ›

Handover documents detail the essential information someone would need in order to take over key responsibilities for completing a project.

How do you respond to a handover email? ›

I have handed over all my major works to Mr _________ (colleague). He will take care of all the activities while I am on the leave. You can contact him on his mobile number ______________ & email id _________________. In case of any urgent work please feel free to send an email to me, I will soon respond to it.

How do you write a shift handover report? ›

Here are three key elements to keep in mind when creating a handover report:
  1. Production Summary. Including a brief explanation of what was done during a particular shift makes it easier for the incoming team to orient themselves and get to work faster. ...
  2. Ongoing Task Status. ...
  3. Key Roles and Responsibilities.
Sep 1, 2022

What is handover note? ›

What is a Handover Note? A handover note is a document written by an outgoing employee for the successor that details the daily tasks and responsibilities of their position. It should be used as a guide for the incoming person on how to perform the duties of the job.

What is the handover process? ›

A 'handover' comes at the end of the project to install, construct, or modify an asset. It usually involves the client formally accepting the asset, the work area, and relevant information from the contractor.

Videos

1. Buildr - Project handover done right.
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2. j5 Shift Handover Overview
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3. Handover Process .. .. Management Insights (Season 2 .. Episode 18)
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4. Effective Shift Handover
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5. Improving project handover
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6. Handover management in cellular network
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