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Generations of mobile communication

Introduction

Looking at the ecological process that mankind has passed through; it is quite evident that communication is one of the basic requirements. It is predicted that humans came into existence on earth they did not know how to communicate with each other. They couldn't speak any language, they had no idea of the use of body language and it was even more difficult to communicate with people who were at some distance. Because of the fact that they couldn't communicate they had to face all the hardships individually.

But gradually as they started to learn techniques of communicating with each other their life started to improve and they started to discover new methods of communicating with distant members of the community. But it wasn't an easy task at all. Because they had no knowledge of any mean of communication, but something had to be done so the they started using different techniques such as lighting the fire, animal's skin, use of different stone for different messages. That laid the basic ideas for the development in communication technology. Resulting in various communication environments these days. One of such environments is the Mobile communication.

Mobile communication means communicating while on move. Mobile communication itself has seen various developmental stages such as first generation (1G), second generation (2G), third generation (3G) and fourth generation (4G). The brief description of the generations of mobile communication is given in the following section.

1G:

first generation of network came into use for the first time in July 1978 in USA.1G consisted of distributed transceivers that helped in communicating with mobile phone. The structure of the mobile phone was analogue and it could only be used for voice traffic. For the transmission of signals frequency modulation was in use. There was one 25MHZ frequency band allocation from cell base station to the mobile phone and another 25MHZ frequency band allocation for the signal from phone to the base station. In order to accommodate more users to the network each channel was separated from the other by a spacing of 30KHZ, but it was not effective enough in terms of the available spectrum. 1G would use frequency division multiple access (FDMA) techniques where the user had to wait for the first user to hang up. The network capacity in 1G was increased by implementing the frequency reuse [1] [2].

2G:

As the mobile communication gained publicity and more people started using the technology, the existing technology couldn't fulfil the needs of the overwhelming majority of people. Therefore new techniques were applied to the existing system to make it more beneficial and accommodative. The new system that was developed into the second generation of mobile communication (2G). The characteristics of 2G were quiet evident that it would accommodate more users and provide them good communication services with higher security. 2G was needed because of the interference and attenuation problems in 1G.

The first 2G system was introduced in Finland in 1991, by Radiolinja (now part of Elisa Oyj) [1]. In 2G the shift was made to fully digital encrypted communication rather than analogue in 1G. 2G solved the problem of higher number of active customers in the network. Now more users could use the service simultaneously. 2G also introduced the additional data transfer through mobile rather than only voice data as in 1G. For example SMS text messages.

As an example of successful 2G system we can study GSM, it was developed in 1980s and is currently under control of ETSI. In Europe GSM started working in June 1991. It can utilize any one of the three frequency bands, either 900, 1800 and 1900 MHZ. Many of its cellular phones can operate as dual and tri band handsets. The question is that how GSM can accommodate more users. The answer is elaborated in the example. Two frequency bands of 25 MHZ are used in GSM 900, one is 890-915 used for uplink while 935-960 is used for downlink communication. Each band is further divided into 124 carrier frequencies separated by 200 KHZ. Each of the 124 frequencies is further divided into eight 577 US slots by using TDMA techniques [1]. Each one of these slots represents one communication channel. So by calculating {124*8=992} we get 992 simultaneous communication channels available for users. It increases the network capacity quiet considerably.

2.5G:

2.5G is the in-between technology in 2G and 3G. Two and a half generation represent a 2G system that implements packet switched domain adding to circuit switched domain [3]. It should not be misunderstood for as a fast technology. Certain benefits of 3G such as IP packer switch networks can be found in 2.5G. 2.5G also reveals the characteristics of 2G such as use of GSM and CDMA networks [3].

3G:

To provide the higher data rates at higher speed the need for advanced generation was felt, and third generation was introduced that could fulfil the growing needs of the mobile users. 3G uses higher frequency band of 2.5 GHZ and above with larger amount of bandwidth than 2G. 3G can provider higher data rates both in mobile and in fixed environments. It gives up to 2MBPS in stationary and about 384 KBPS in mobile environments. [4]. 3G has encouraged the video streaming and IP telephony to develop further and provide cost effective services to mobile users.

3G is the ITU standard to represent third generation mobile telephone system under the scope international mobile telecommunication program (IMT-2000). 3G can implement various network technologies such as UMTS, GSM, CDMA, WCDMA, CDMA200, TDMA and EDGE [5]. The first 3G was launched commercially in DoCoMo in Japan in October 2001. Japan along with South Korea implemented 3G rapidly with the generous support from the government authorities and elsewhere it was slow because of the expensive equipments of 3G. In Europe Manx Telecom in Isle of Man launched the first 3G network, but the first commercial 3G in Europe was launched by Telenor in December 2001. Till December 2007, there were 190 3G networks operating in 40 countries around the world. Though this figure looks high but its only 7% of 3 billion mobile phone subscriptions worldwide [5]

It is quite evident from the data shown in the chart that 3G has not yet achieved its total success or popularity, but with the new advents and developments has made it more attractive for the mobile subscribers. According to statistics from IDA telecom Singapore till December 2009 the number of subscribers to 3G post-paid was 3,013,800 which is low as compared to the number of subscriptions to 2G i.e. 3, 240, 700 [7]. But we can observe from the stats that the gap has narrowed vigorously and it will shift the direction in favour of 3G.

4G:

The mobile users demand for more and more sophisticated and compact devices, therefore the manufacturers are emphasizing on smaller devices with increased processing and high level security [8]. Although current 3G devices are good but still there exists room for improving image processing and speed of processor so that they can be used for high demanding 4G applications. The applications like 3D games, high-definition camcorders and larger mega pixels cameras need efficient application processors [8]. Fourth generation (4G) also called Next Generation Network (NGN) offers one platform for different wireless networks. These networks are connected through one IP core. 4G integrates the existing heterogeneous wireless technologies avoiding the need of new uniform standard for different wireless systems like World Wide Interoperability for Microwave Access (WiMAX), Universal Mobile Telecommunications System (UMTS), wireless local area network (WLAN) and General Packet Radio Service (GPRS).

4G networks will increase the data rates incredibly, by providing 100Mbps to 1Gbps in stationary and mobile environment respectively. In 4G the latency will be decreased considerably, because of all IP environment. 4G is can be considered as a global network where users can find voice, data and video streaming at anytime and anywhere around the globe. In 4G the integration of network and its applications is seamless therefore there is no risk of delay. While implementing 4G the cost issue needs to be taken into consideration so that users can benefit from this technological development fully.

Applications of 4G

With the increase in the data rates, the mobile phones are made to perform higher performance applications. In 4G the mobile phone is not only for calling but its something extraordinary device that can be used for variety of purposes. One such application in 4G is context awareness. For example if the mobile user is passing by an office where he/she is having an appointment to meet someone and they have forgotten the appointment. If the office location, address and geographical location matches the one user has already stored in the phone, he/she will receive information about the appointment and will be reminded that you need to perform this activity. Telemedicine is another application of 4G [8]. Using telemedicine a patient can send general reading like temperature, glucose level and blood pressure to the doctor online [8]. Or if someone needs to know about their family member's health continuously they can receive all the information through telemedicine by using 4G technology.

LTE

Long Term Evolution is an emerging technology for higher data rates. It is also referred as 3.9 G or super 3G technology. LTE is developed as an improvement to Universal Mobile Telecommunication System by 3rd Generation Partnership Project (3GPP) [9]. LTE uses Orthogonal Frequency Division Multiple Access (OFDMA). The download rate in LTE is 150 Mbps and it utilizes the available spectrum in a very sophisticated way [8]. In LTE the IP packet delay is less than 5 mille seconds which provides the experience of wired broadband internet access in wireless environment. The mobile TV broadcast is facilitated by LTE over LTE network. [8].

4G implementation

TeliaSonera Sweden is the first Telecommunication Company to implement 4G technology developed by Ericson Sweden. Initially TeliaSonera will provide the coverage in “25 largest municipalities in Sweden” [10]. The service will also be provided in four largest towns in Norway [10]. According to the tradition of Nordic region its always the leader in Telecommunication development so the 4G is just a spark of that tradition which will provide the customers with real time internet access, online gaming and many more high speed and efficient applications [10].

Security in 4G

Humans have been striving for security right from the beginning of the universe or the human life. It has changed its nature through different phases humans have witnessed but in none of the phase its utmost importance cannot be denied. Either it is security for life, wealth, land or any other type; it is always one of the priorities humans have. Security is applicable to all the areas of human life, its scope cannot be modified to some particular area. No matter how much humans work on improving security but the threat is always there and there always exists room for improvement.

Security in digital world means to protect the digital systems from criminal and unauthorized usage. In terms of computers and mobile communications the need for security has increased overwhelmingly with the improvement in technology. Some decades ago when first generation of mobile networks were in use the concept of security was not so much in practice or we can say that awareness was not that much highlighted. But as technology kept on improving and new advents were introduced the need of security kept on creeping. These days no one likes to be insecure digitally. Because of the heavy dependence on digital media for the use of private, sensitive, financial and important communication. There can be many attacks on digital data some of them are eavesdropping, man in the middle attack, denial of service (DOS) attack, spoofing and lot more.

Traditionally network security is considered to secure network edges from external attacks. Unfortunately this is not sufficient as attackers look for breaches in network protocols, operating systems and applications. [11]. Therefore we need a comprehensive security mechanism that can protect the whole network. We can design security architecture on the basis of following objectives:

Availability:

keeping the network and its components secure from malicious attacks so that there is no break during service flow.

Interoperability:

using security solutions that are applicable to most of the 4G applications. They should avoid interoperability issues.

Usability:

end user shall use the security mechanism easily.

QoS:

security solutions should follow QoS metrics. Cryptographic algorithms used for voice and multimedia shall meet QoS constraints.

Cost-effectiveness:

security mechanism should cost as less as possible.

Third generation of networks provide voice and paging service to facilitate interactive multimedia. The applications include teleconferencing, internet access, video streaming, multimedia messaging and so many others. In fact 3G provide a launching pad for applications such as wireless web, email (SMS, MMS), multimedia services like video streaming etc.

Fourth generation is to address the future uses of the customers in terms of higher data rates and increased bandwidth utilization. 4G is built on the concept of IP core accommodating various heterogeneous networks. In fact 4G acts as a platform for heterogeneous networks. A service subscriber uses one of the access networks providing service from the one plateform.This openness and flexibility increase the probability of security breach in one of the main components of the system. Therefore the need for security has become more dominant because of the nature of the participating networks.

Security threats to 4G

Potential threats to 4G are:

IP spoofing

User ID theft

Theft of Service (ToS)

Denial of Service (DoS)

Intrusion attacks

X.805 categorizes security threats to 4G as:

Information or other resources destruction

Changing or corrupting information

Loss of information

Leakage of information

Service interruption

It is impossible to make a 100% secure system because with advancement in technology new threats will continue to take place. As 4G is a heterogeneous network combination therefore every network provider has his own security requirements and together they can some time contradict each other. Therefore 4G security mechanism should be flexible enough to cope with new threats and challenges.

Security architecture

IP Multimedia Subsystem (IMS) is independent of the access technologies, therefore 4G security can be observed under lights of IMS security. Like IMS 4G security is based on access view security where the first hop is secured to access the network, 4G core view security and interconnecting view security. As 4G is mixture of heterogeneous networks therefore it supports many business roles that range from regional network operators to service providers. The interoperateors interfaces that can be prone to security attacks. In order to provide protection against this aspect of attack 4G introduces security gateways (SEGs) which facilitates security between domains.

ITU-T X.805

International Telecommunication Union developed X.805 model based on Bell Lab Security Model [bell lab refrence]. X.805 works on modular approach and provides security against all possible threats for end system network security. There are eight security dimensions that further increase the resistance to vulnerabilities.

X.805 consists of three security layers, three security planes and eight security dimensions. The first security layer is Infrastructure layer; provide the creation and maintenance of the network between individual communication and network elements. Secondly service layer, provides service accessibility. Last layer is application layer that facilitates users to access the hardware or software applications of the network remotely, for example VPN, Email etc. security planes (Management, Control and User security) reveals the functions performed over the network. As can be seen from the figure that there are eight security dimensions (vertical) that shows the aspects of the network to be considered for security against potential threats. The dimensions are defined briefly as under:

Access control:

controls the unauthorized usage of the network resources.

Authentication:

Confirmation of identities of the users, so that only authentic users can access.

Non repudiation:

Proves the origin of the data that it is from an authentic origin.

Data confidentiality:

Security of data flowing through the network, no unauthorized access to the data.

Communication security:

Only authorized users are allowed to send or receive communication.

Data integrity:

Protects data from unauthorized use so that no outsider can use, modify or delete any component of the data. It also provides log records of unauthorized attempts on the data.

Availability:

Network facilities are available for authorized users only.

Privacy:

protection of information.

Three planes of the X.805 define nine modules; to each of these nine modules eight security dimensions are applied. Each module has different security dimensions and they comprise of different sets of security analysis. As it's shown in figure 3 we apply security dimensions to module 3 which make the end user functions secure. Similarly these dimensions can be applied to other modules as well where the security parameters are different for each one.

Denial of Service and Cognitive Intelligence

Cognitive Intelligence is based on the legacy security techniques of Genetic algorithm and Ant systems. The basic concept is the pheromone distribution on the way that gives direction for following traffic and provides the basis for security. The amount of pheromone ensures that the same path is adopted by the following traffic. At the end of each tour the pheromone status is updated. Cognitive Intelligence makes use of the Tabu-list. It contains the nodes that an agent has visited along its way in the network. The agents visit the nodes in the network for the purpose of avoiding any chances of energy decrementation and to list nodes in the table.

The denial of service attack can occur differently with many different devices in 4G, for example with zigbee it can be in the form that it works on the battery so energy the energy is important aspect here, while for WPA the something-of-death attack is fatal. That is why we need a cognitive framework to combat the attacks with greater sophistication. 4G networks work on the assumption that the BS can never be attacked for DoS while the participating nodes are very much prone to the attacks and when the network is initialized the algorithm uses the local information for performing cell dimensioning.

We can observe in figure 5 the mobility management achieved through cognitive intelligence. The communication between the BS at the region of interest is denoted by two way communication arrows. While the mobile node movement from source to destination or from one region to another region is showed by the dotted line. Both the regions have different modulation and error correction schemes. The two regions are separated by the thick dark line. When the mobile node moves into the coverage area of another network the agent in the new network takes information about all the neighbours from the base station in order to provide security and high QoS on the resource availability to MN. Based on the performance parameters such as bit error rate (BER), packet delivery rate (PDR), signal strength (SS), call dropping probability (CDP),distance (D), number of hops (H) the optimal settings for the QoS and security are formed. A threshold value for each parameter is set, which provides the basis for the decision that whether the call is successful or not. The agent selects the optimized value for the call to reach its destination.

Because of the fact that the scenario is mobile therefore the swarm agents monitore the area of interest continuously. The wide spread agents communicate through pheromone with each other, therefore the route that is abandoned with pheromone is considered to be optimized path for higher QoS and resources. To calculate the pheromone deposition we use following equation [15]

ζij =ρ(Ϛij (t-1))+ QDt.Et.BERt.RTt.CPDt

In the above equation i means transition from MN to destination j. ρ means memory while Qis an arbitrary parameter belonging to agent. As the parameters used in pheromone deposition are dependent on performance parameters stated above therefore shift in any one of those parameters can directly change the transition probability of the agent. As given in equation [15]

η ij =(ѱij)α.(ξij)β

Combine the pheromone deposition with performance parameter gives the agent's movement between MN,IN or BS [15].

Equation

The parameters from both physical and MAC layers provide the trails formed by the ant agents therefore effectively eliminating DoS on these layers.

QoS in 4G

QoS

In telecommunication the term QoS (Quality of Service) stands for the resource reservation control mechanism, instead of the translation of term as achieved service quality. Communication occurs when the data flows from source to destination and QoS guarantees a specified level of bit rate, jitter, delay and packet drop probability to the flow. QoS assurance is important for real time services like Voice over IP (VoIP), online gaming, IP TV and video streaming etc. QoS enables network administrators to avoid network congestion and manage the network resources efficiently.

The goal of the 4G is to provide the users the facility of Always Best Connected (ABC concept). Fourth generation of networks is a combination of different networks. It gives a platform for various technologies to be accessed. To provide QoS in 4G is not simple and easy job as one has to deal with different parameters in different technologies. Like if a user is moving and changing his coverage network, so to provide service under QoS framework is challenging. While a mobile user is moving from one network to another network his communication session needs to be maintained seamlessly irrelevant of the coverage network. Similar is the case with video conferencing and video streaming, the users like to receive the services seamlessly.

There are some protocols designed to maintain the seamless communication of the users while moving or in other words to minimize the latency and packet loss of the ongoing communication session. The mobility protocols are Mobile IPv6, Hierarchical MIPv6, Fast MIPv6 and some more (details of all these protocols are given in chapter Handovers). These protocols can help in improving the mobility management of mobile users. In order to provide QoS to the mobile users we propose a combination of mobility protocol Seamless Mobile IPv6 (SMIPv6) and Session Imitation Protocol (SIP).

There are two types of loses when a mobile user switches network, one is called segment packet loss and the other is called edge packet loss. Segment packet loss is because of the undeterministic nature of the handoff [14]. While the edge packet loss is between the Mobility Anchor Point (MAP) and the MN. To minimize these losses different approaches are used, to minimize edge packet loss the MN is moved as close to the MAP as possible, while for the segmented packet loss two approaches are used one is synchronized-packet-simulcast (SPS) and hybrid simulcast mechanism are used. In SPS the packets are sent to both the current network as well the potential network the MN is approaching. While hybrid simulcast mean that the mobile node informs the network about the handoff to be taken into effect but it is decided by the network to which AR the MN shall attach. This way the packet loss is minimized (the detailed mechanism is given in chapter of handover).

Session Initiation Protocol (SIP) is used to manage mobility of different entities such as session, terminal, service and personal mobility. It facilitates mobility and maintains the real time multimedia sessions. SIP is an application layer protocol therefore it can work both in IPv4 and IPv6. SIP work along with other protocols such as Real Time Transport Protocol (RTP).

There are some strategies proposed to achieve QoS, some of them are discussed in this chapter.

Combining Intserv and Diffserv

Integrated services and differentiated services are combined to obtain the QoS assurance in 4G networks. Intserv make use of the Resource Reservation Protocol (RSVP) for obtaining the resources. It works on the basis of priorities. The higher the priority the first is its turn and the similar priority applications are assigned to a queue. Intserv function well for small scale network, which can be one of its drawbacks that its not scalable for larger networks.The diffserv on the other hand is much scalable for larger networks. The combination of these two QoS models can be obtained by placing the intserv near to the ends where the data is received or sent from, means the sender and receiver. While the diffserv is placed at the core network. The combination of these two can help in avoiding traffic congestion and loss of packets which simultaneously improve QoS [12].

QoS Manager

As 4G is combination of heterogeneous networks therefore managing network's resources is necessary in order to provide QoS for different flows. To manage the resources we need an entity called QoS Manager [13]. This entity can control the allocation of various resources such as bandwidth under the framework of QoS. It can support various types of handovers as well [12]. While the mobile user is moving from one network domain to another he needs to have seamless handover with QoS assurance and it requires the resoururce allocation in advance. In each network domain there exist QoS manager, called Domain QoS (DQoS) manager. There is also QoS manager at the IP core network. To ensure end to end QoS and resource allocation the DQoS managers of each domain and QoS manager of the core network shares communication [12]. To provide security during handovers a security entity is included in QoS manager. This can help in authentication of the users and data protection.

To be consistent with network policies the QoS manager needs to be in contact with the Authintication, Authorization and Accounting (AAA) server. QoS manager make use of the two protocols to interact with AAA server, they are Common Open Policy Service (COPS) and Diameter protocols. The interaction between Policy Enforcement Points (PEPs) and QoS manager is facilitated by COPS, helping in control of policy in IP networks [12]. COPS transport information of the network usres to transport layer to ensure optimum resource allocation. The Diameter protocol works parallel to the AAA server in 4G networks. The communication between network access server and AAA server is carried by Diameter protocol by transporting AAA information [12].

Our approach of combining SMIP and SIP

CHAPTER 3

Handovers

Handovers in fourth generation of networks face lot of challenges to support all the existing aspects of in hand communication systems and standards. Traditionally handoff management stands for maintaining smooth and seamless communication while the mobile node (MN) moves inside or outside of the current network. MN can move inside one network from one access point (AP) to another AP, while MN can also change its current coverage network. During both these case MN undergoes handover process. The handover inside MN's coverage network is named as horizontal handover while the handover in which the MN changes network for example MN moves from GSM to UMTS, is called vertical handover. These handovers are also known as intera and intersystem handovers respectively.

Mobility is one of the emphasised requirements of communication in significantly advanced technological era. Mobile communication requires to be mobile in its real sence, i.e to support multi hetrogenous networks while on move. That is only possible if there exists some sort of correlation among these hetrogenous networks.

Fourth generation of networks offer this privilege by accommodating all the hetrogenous networks like WiMAX (World Wide Interoperability for Microwave Access),

Universal Mobile Telecommunications System (UMTS), WLAN

and General Packet Radio Service (GPRS) on one single platform, Where they perform interoperable. For example if an a mobile user is talking on the phone while he is moving and he changes his operational network from GPRS to for example WLAN then at this particular time the mobile user undergoes handover and there is a potential risk of communication disturbance. The amount of connection establishment time the change requires will disturb communication of the mobile user.

Therefore mobile users require more efficiently smooth and seamless communication while moving across networks. Recently much of the research is going on to maintain the unbroken communication of MN or to minimize the packet loss and improve seamless communication.

4G offers that facility for mobile users to communicate seamlessly or in more technical words 4G offers facility for seamless handovers across hetrogenous networks. For that purpose many protocols are used to achieve seamless communication. Mobile internet protocol version 6 (MIPv6) is the back bone for mobility management in 4G. further protocols are developed to improve the communication. Following we discuss various protocols that are use to undergo seamless handover in 4G.

1. Mobile IPv6

With the use of voice over IP (VOIP), it is impossible to talk continuously on a mobile device because with mobility the IP changes and hence communication is broken. This problem is solved with the help of Mobile IP. Mobile IP detects the new wireless connection after it loses the previous one. And the ongoing communication state is not disturbed. Using MIP enables the Mobile node (MN) to communicate with corresponding node (CN) without any break. When MN is inside its network it uses home address for communication, when it moves to another network it uses a care of address (COA). COA is a temporary address and it is binded to the MN home address. This scheme hides the changed IP from the upper layers.

When MN moves from one network to other network COA is assigned to it by foreign agent (FA). When packets intending the MN arrives HA will forward these packets to MN's COA. If MN changes it COA, it sends a binding update (BU) message to HA and HA replies with BU acknowledgment message. BU updates MN's binding information, home address and CoA. When CN sends packets for MN they come to HA which forwards these packets to MN's CoA, while on the other hand MN sends packets to CN directly which makes a triangle routing. This way packets take longer root and network bandwith can be wasted. To solove this problem MIPv6 was introduced.The structure of MIPv6 is simpler and has got better security, whereas MIPv6 solves the growing requirement of IP. Figure 2 explains triangle routing problem

MIPv6 can keep track of MN's CoA by timely BU between MN and its HA, but the problem arises with the packets intended for MN before BU. Discovering a new subnet, establishing a new CoA and information exchange between MN and HA, all the processes take time and lot of signalling traffic. Hence causing latency and packet loss. The worst case is when MN is roaming between two access routers ARs several times creating a ping pong effects. In this case too many handovers and location updates are experienced and causes interruption in MN's communication with its CN. The packets that were intended for the old CoA are dropped. Because of these reasons MIPv6 is not good scheme to perform in 4G high speed data transfers.

Hierarchical Mobile IPv6 (HMIPv6)

Developed to reduce the required signalling traffic that affects handover latency of MN. In MIPv6 there was no concept of local and global mobility separation, but HMIPv6 gives the opportunity to deal both of these mobility scenarios separately.. HMIPv6 fullfills this by the introducation of a new entity called mobility anchor point (MAP). The global internet is divided into regions, each region is connected to the internet via MAP. It acts as an anchor point to hold the segments together. Figure 3 explains structure of HMIPv6.

In HMIPv6 each MN has two care of addresses, one is called regional care of address (RCoA) and the other is called global care of address (GCoA). RCoA belongs to the region covered by the MAP. A mobile node communicated with its corresponding node through it RCoA. Figure 3 explains function of HMIPv6.

When an MN moves from one network to another network or to a new region, it first take its RCoA through MAP advertisement information. MN then informs its HA and CN about its point of location. In MIPv6 there was a drawback of repeated connectivity to the same AR. In HMIPv6 when MN repeatedly connects to the same AR covered by the same MAP, MN takes new CoA from MAP called local CoA. This process is kept hidden from HA and CN. This mobility is handled locally inside the region and it reduces the latency factor. As MN's CoA is changed so the information intended to MN from CN can not follow the old CoA. So HA sends these information to MAP and MAP then tunnels the information to MN's local care of address. This way MN's communication with CN is not disturbed.

IDMP based fast handover

IDMP stands for Intera-Domain Mobility Management Protocol. IDMP is a modified version of MIPv6. In IDMP the MN can get multiple CoA's and has the domain wide entity called mobile agent (MA) that controls the specific domain. MN can get two CoA's one local CoA and oother Global CoA. LCoA shows the current subnet that MN is connected to while GCoA shows MN's domain location. The scenario in IDMP is that MN sends certain messages to access router (AR) and AR predicts an upcoming L3 handover. With the help of IDMP based fast handover we can reduce the intradomain update delay.

When mobile node moves between APs from same subnet this is L2 handover and when MN moves among APs from different networks then that is L3 handover. L 2 trigger is used to notify the L3 handover of MN. Trigger from MN of base station BS is used to notify MA about a handover process. This way the chances of interruption are decreased. All the incoming packets are multicasted to the subnet agents (SAs), they buffer these packets intended for the MN and when the handover process is completed they start sending these packets. In this way the loss of packets is minimized. Using IDMP based handover scheme can save bandwith on link and, because only one SA or BS multicasts packets rather than many SAs or BSs doing it.

Fast Mobile IPv6 (FMIPv6)

FMIPv6 is of two types, one is called predictive and other is called reactive FMIPv6. When there is ample amount of time available to process the handoff then predictive FMIPv6 is used, while the reactive FMIPv6 Is used if there is not sufficient time to process the handovers.

A node (base station-BS) is modeled as a queuing system including three queuing components as shown in Fig. 1. Input Queue, Downlink Queue, and Inter-BS Queue. The numbers of Input Queues and Inter-BS Queues are equal to the number of input and outputlinks, respectively. For simplicity, assume that there is only one Downlink Queue for the radio downlink. Packets arriving at BS are classified and stored either in Downlink Queue if the packets are for users connecting with the node or in appropriate buffers of an Input Queue if the packets are for delivering to other nodes.

Mobile nodes have access point identifier (AP-ID), when an MN moves into a network it detects the signal coming from the APs through its AP-ID. MN sends router solicitation for proxy advertisement (RtSolPr) message to previous access router (PAR), then PAR replies with proxy router dsadvertisement (PrRtAdv) messege including new access router's (nAR's) prefix value and IP address. MN can obtain its CoA from information of PrRtAdv. In order to connect to a nAR, MN sends an FBU message to its PAR. pAR sends a handover initiation (HI) message along with MN's nCoA to nAR. Once nCoA is accepted nAR starts a buffer. nAR sends packets to nCoA. nAR also sends handover acknowledgment (HAcK) back to PAR. Then pAR sends a FBAck message to MN and nAR. pAR starts forwarding packets to nAR. During the time MN is engaged in handovers the packets arriving are saved in the buffer of nAR which are forwarded to MN once the handover is completed.

Seamless Mobile IP (SMIP)

SMIP uses hierarchical scheme as its parental architecture, with the introduction an intelligent handover mechanis. SMIP addresses following issues

* Maximum minimization of handover latency

* Decreased handover signalling overhead

* Scalability

SMIP ensures packet lossless handover latency delay. Handover latency is same as L2 handover delay that equals tens of milliseconds. While the signalling overhead is not more than the HMIP or FMIP. SMIP can be scaled on very large area with graceful failure tolerance. The failures are kept hidden from the end devices so that their communication is not interrupted. SMIP facilitate load balancing by distributing control entities.

There are two types of losses in SMIP

1. Segment packet loss: packet loss between MAP and access router. It happens because of the uncertain nature of handoffs and the shifting of data at MAP after receiving MAP binding updates

2. Edge packet loss: packet loss between the AR and MN. Cause of edge packet loss is movement of MN and errors in data.

Solution to segment packet loss can be achived by using synchronized-packet-simulcast (SPS) scheme along with hybrid handover mechanism. SPS simulcast packets to both the current network of MN aswell the potential network of MN. although hybrid handover mechanism is initiated by MN but its controlled by the network. The MN is the best to know about its current location but the connection to another network is decided by the network. While the edge packet loss is can be minimized by decreasing the distance between the AR and MN. figure 6 defines SMIP architecture.

As mentioned earlier that SMIP builds on combination of HMIP and FMIP. SMIP adds another entity to the scheme called the decision engine (DE), the function of DE is that it manage the handover process and contributes to load balancing among access routers. It ensures that mobile node is connected to an AR with lesser load. Another addition of SMIP is SPS with intelligent hubrid handover protocol. The function of MAP is to divide the mobility into micro and macro mobility. The messages are explained as below.

Mobile node sends current tracking status (CTS) message to DE. CTS contains MN's location tracking information. ARs send carrying load status message to DE containing information about the MNs the specific AR is having. DE sends handover decision (HD) message to ARs. HD informs the ARs about the handover decision like allocation of MN to a specific AR. oAR sends handover notification (HN) message to MN. HN message informs MN that which AR it should connect to. oAR sends simulcast (Scast) message to MAP which starts the SPS process. Once the new connection is established nAR sends simulcast off (Soff) message to MAP that stops SPS process. Figure 6 shows messege transferring scheme.

Access router continuously send beacon advertisement messges. When a MN receives these messages it sends an RtSolPr message to its oAR. This is an indication that MN has found nARs and it want to undergo a seamless handoff. RtSolPr message contains information about all the newly discovered access routers. Then the oAR sends HI message to all of these ARs.HI consists of MN's oCoA and the requested nCoA. In reply to HI message all the newly discovered ARs will reply with HAck. Incase the nAR accepts the request for nCoA the oAR creates a temporary tunnel to the new CoA. In the reverse case if it doesn't accept the nCoA then oAR forwards packets destined for MN to nAR which are ultimately delivered to the MN.

When ARs receive modified router advertisement messages CLS messages are sent periodically by ARs to DE. MN generates CTS messages when MN receives beacon advertisement from ARs. CTS is the combination of signal strength of the vicinity ARs and their ids, which perform as MN location information.CTS messeges stops when ARs receives HD message from DE. Duplicated CTS messages arrive at DE if the connection to the current AR is weak resulting in MN's exchange of location information with other ARs. DE simply will discard the duplicated messages arriving. When MN seeks handover the DE sends HD message to all the ARs, as a result oAR sends HN message to MN along with PrRtAdv message indicating which AR to connect to.

As mentioned earlier there can be three types of movements an MN can make. Namely stochastical, stationary or linear. If the MN is in stochastic mode then HD message keep all the ARs to be in the anticipation mode. In anticipation mode ARs keep the MN binding for the purpose if MN connects again so this will save unnecessary reconnections and will save time. When the connection to current AR decreases a certain threshold value. DE send more HD messages to participating nodes to inform them that they are no more required to be in anticipation mode. Next is the stationary position of MN between coverage areas of two ARs. In this case mobile node has two care of addresses one from each AR, and HD message from DE will enforce multiple binding between MN and ARs. Last is linear moment, HD will facilitate MN to which AR to get connected to while other ARs are informed by DE through HD message that connection is established and they are no more part of this handover process.

After MN receives HN message it will send an FBU message to its oAR. FBU binds MN's current link address to the nCoA. Upon the reception of FBU by oAR, an Scast message is generated to MAP starting simulcast of packets. Any packet arriving at MAP after the Scast messeg will be duplicated, and sent to both oAR aswell nAR. These packets are marked with S bits. oAR will send F-BAck message as a reply to FBU.

There are two types of buffers at nAR, one is called f-buffer and other as s-buffer. F- buffer contains packets forwarded from oAR while s-buffer contains packets that are marked with s-bit. Once the mobile node arrives at new network it sends F-NA messege to nAR. After receiving this message nAR starts sending the buffered packets to MN. nAR tries to empty the f-buffer first before starting transmission of s-packets. At the same time oAR will only forward the packets whom s-bit is not marked to nAR. MN continues receiving packets from oAR until it switches netork immediately. When f-buffer is emptied the MAP is informed through Soff message which ultimately stops packets simulcast. MAP binds the new on-link address of MN with its regional CoA. An Soff message is forwarded to DE aswell which stops MN to undergo another seamless handover unless the current one is completed.

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