Chapter I 4G NETWORKS HANDOFF AND ISSUES

1 Chapter I 4G NETWORKS HANDOFF AND ISSUES 1.1 Introduction The era of wireless communication is dated since the period of Marconi and Tesla. However the period of invention circumscribed with countless limitations in the technology of wireless communication. The geographical coverage happened through the radio telephone network comprised of inadequate base stations. The response produced by BS during the time of simultaneous call receiving station was limited to the less coverage boundaries due to the number of channels exist in the BS and which did not allow for speed and parallel communication. The tenure of digitized sphere from 1970 made a tremendous growth for the adaption of information technologies especially with respect to cellular telephone system. Thus from the dating of 1970 s to till an unimaginable growth phase took place in the field of information technology specifically in wireless communication. The present stage of wireless technology has become a part and parcel of social life and thus made indispensable impact in every sphere of human activity. The growth curve of cellular technology in recent past is phenomenal and it has become inevitable machine as a part of human interaction 1.2 Generation of networks Mobile phone technology is an ideal illustration for diffusion of innovation and rate of adaption. The comprehensive relook of 1G to 4G, shows an impeccable technological innovation and new usage pattern with covering both delighted and potential features. The growth and enrichment of cellular technology can be viewed under different generations 1.3 First generation (1G) network The first generation of wireless communication familiarly termed as 1G was introduced in the period of early 1980 s. It was referred as Brick Phones under analog and bag phones

2 since the introduction for mobile technology. 1G networks (NMT, C-Nets, AMPS, TACS) were treated as first analog Cellular system and they acted as radio telephone system before the term as 1G. The purpose of designing 1G was focused for voice call without covering data services. The role of 1G under cellular system signifies as first generation analog technology standard. The analog transmission used in the first generation mobile network technology (figure.1.1) did not encrypt for voice signals during a telephone call. Figure. 1.1 Analog cellular architecture 1.4 Second Generation (2G) network 2G is abbreviated as second generation wireless technology. It was commonly launched under GSM standard in Finland in the year 1991 [1]. 2G systems proved its efficiency for mobile phone penetration levels on the spectrum and permitted data services for mobile. It started with SMS, picture and multimedia messaging services.

3 1.4.1 Technologies in 2G The technology covered in 2G cell phones in India for the purpose of transforming the information are categorized as given below. [2-3] Frequency division multiple access (FDMA) Code division multiple access (CDMA) and Time division multiple access (TDMA) 1.4.2 Capacity of 2G 2G resembles analog architecture when its digital cellular architecture is viewed. Figure 1.2 depicts a Base Transceiver Station (BTS) which services each cell. The transceiver comprised more cells in order to address the increasing capacity. Hence, it requires Base Station Controller (BSC) which is an intermediate device, to maintain and control a group of base station transceivers. The base station controllers feed into the mobile switching centre (MSC) which interfaces into the group of databases in order to enable the roaming, billing and interconnection as well as interfacing to a gate way mobile switching centre that passes the suitable billing information. The invoices are produced effectively for home service provider. The processes of roaming with suitable database are explained below. Home Location Register The information related to subscribers in a located area is provided by home location register and that is controlled by a particular mobile switching centre (MSC).

4 Figure 1.2 Digital cellular architecture Visitor Location Register The calls that are made by roaming subscriber is stored in this register. The information about the calls is frequently forwarded to the subscriber s home service provider for billing and related purposes. Visitor location register is maintained for each mobile service switching centre. Authentication center The authentication centre helps to protect the subscriber. The carrier provides security by preventing from unauthorized access through the process of customer identification and encryption. This center works in association with the home location register. Equipment Identity Register This database records the different types of mobile equipments and maintains a database of all the equipments that are blacklisted or stolen for some reason.

5 1.4.3 Global System for Mobile Communications (GSM) GSM is the technology paves the source for the world's mobile phone networks. GSM uses FDD and TDMA. It is independent of analog systems. GSM can be implemented in any frequency band. GSM favours Group III fax and it provides a subscriber identity module (SIM) card, which is a smart card that analyses personal details, accounting and phone number of an individual's service. To activate and avail service, the SIM card has to be used in any of the GSM handsets. Thus it helps a user to roam globally and maintains the service. GSM supports effective utilization of the spectrum which is much better compared to analog environment. It also provides the ability to improve security by applying encryption to the digital bit streams, fraud prevention and authentication via SIM cards. 1.5 2.5G Wireless network 2.5G (second and a half generation) wireless network is used to describe 2G-systems that employs a packet-switched domain along with circuit-switched domain. PDC, GSM and other TDMA-based mobile system providers and carriers have developed packet based 2G+ technology thereby increasing the data communication speed as high as 384kbps. The 2G+ systems use the following technologies. General Packet Radio Service (GPRS) High Speed Circuit-Switched Data (HSCSD) and Enhanced Data Rates for Global Evolution (EDGE) The enhanced data rate for GSM evolution is also referred as enhanced GPRS. Basically twocoremodules such as Serving GPRS support node (SGSN) and gateway GPRS support node (GGSN) are required. The SGSN provides packet routing to and from the SGSN service area for all users in that service area. It provides the packet-switched link to mobilestations. The GGSN serves as a gateway between the public data network such as an IP network or an X.25 network and GPRS network. The GGSN also connects to other GPRS networks to facilitate GPRS

6 roaming There is a requirement for mobility management in order to locate a new air interface for packet traffic and the GPRS mobile station. Additional security features also need to be implemented, including firewalls and encryption. Finally, GPRS specific signaling is also required. 1.6 Enhanced Data Rates for Global Evolution (EDGE) - 2.75G EDGE builds on enhancements provided by GPRS and HSCSD technologies. EDGE basically enables a reasonable data transmission speed in good conditions, especially near the base stations. For EDGE to be effective, it should be installed along with the packet-switching upgrades used for GPRS. In addition, an EDGE transceiver unit must be added to each cell and the Base Stations (BS) should receive remote software upgrades. EDGE can coexist with GSM traffic, switching to EDGE mode automatically. EDGE ultimately allows the combination of digital TDMA and GSM and provides an enhanced version of GPRS. It supports 48Kbps to 69.2Kbps per time slot, and by aggregating time slots, it can support up to 384Kbps. GSM's 200KHz channel spacing is also maintained in EDGE, allowing the use of existing spectrum bands. EDGE is also sometimes referred to as a 2.75G system. 1.7 Third generation Network (3G) 3G is the third generation of mobile telecommunications technology. 3G is defined by the ITU under the International Mobile Telecommunications 2000 (IMT-2000) global framework [4]. 3G is exclusively designed for high-speed multimedia data and voice. Its constitution and goals includehigh-qualityaudio and video and advanced global roaming. It enables to goanywhereand automatically be handed off to any wireless system available. The architecture of 3G network is shown in Figure 1.3.

7 1.7.1 Evolution of 3G The seamless, compatible evolutionary path of enhancements to the existing GSM technology family is described by 3G evolution. These enhancements will enact GSM operators to strengthen their ability to provide mobile broadband multimedia services by supporting higher data transfer speeds and greater system capacity. Figure 1.3 Architecture of 3G network The 3G evolutionary path consists of a series of well-defined technology enhancements including High-Speed Downlink Packet Access (HSDPA), High-Speed Uplink Packet Access (HSUPA), and High-Speed OFDM Packet Access (HSOPA).

8 1.7.2 High-Speed Downlink Packet Access (HSDPA) HSDPA is a packet-based data service in the W-CDMA downlink channel. It was designed to support IP and packet-based multimedia services. The theoretical peak rate is 14.4Mbps but in actual the practical rate is around 1.8Mbps up to 3.6Mbps. The high download speeds offered by HSDPA will profoundly enhance a wide range of mobile services, from web browsing to video downloads. Another key feature of HSDPA is the use of MIMO, which results in high improvements in capacity. MIMO antenna systems are the work item in the 3GPP Release 6 specifications, which support high data transmission rates (up to 20Mbps). Another important enhancement to HSDPA is that error control. It is greatly improved through the use of Hybrid Automatic Repeat Request (HARQ). HARQ is a variation of the ARQ error control method that gives better performance than ordinary ARQ, especially over wireless channels. HARQ includes fast cell search and advanced receiver design as the other mentioned features. 1.7.3 High-Speed OFDM Packet AccessHSOPA) HSOPA is also known as Super 3G. HSOPA is a new air interface system incompatible with W-CDMA unlike HSDPA or HSUPA. HSOPA applies multiple-input multiple-output (MIMO), Orthogonal Frequency Division Multiplexing (OFDM) and antenna technology to hold up to 10 times as many users as W-CDMA based systems. It is still in expansion and its experimental concert is 37 Mbps over a 5 MHz channel in the downlink, which is close to the theoretical maximum limit of 40 Mbps.

9 1.7.4 High-Speed Uplink Packet Access (HSUPA) High-Speed Uplink Packet Access (HSUPA) is a mobile telephony protocol that is based on HSPA (high speed packet access) set of technologies. HSUPA is mainly designed for extending support for high uplink speeds. Current HSUPA devices support uplink speeds as high as 5.7 Mbps. There are actually two protocols under HSPA, one is HSDPA (where D stands for Downlink) and the other one is HSUPA. Their main focus is to provide higher downlink speeds. As downloads are mostly preferred than uploads by HSPA users, HSUPA speed becomes slower. The advantage of HSUPA is that it helps for uploading a large email attachment through the mobile device. Generally, this is the reason due to which HSUPA is preferred over HSDPA. 1.8 Fourth generation Networks (4G) Next to 3G, the fourth generation of mobile telecommunications technology (4G) has been evolved. A 4G system offers mobile ultra-broadband internet access, in addition to the usual voice and other services of 3G like smart phones, laptops with USB wireless modems and to other mobile devices. Conceivable applications contain IP telephony, amended mobile web access, gaming services, video conferencing, high-definition mobile TV, 3D television and cloud computing. Two 4G systems are commercially deployed, one is Mobile WiMAX standard (first used in South Korea in 2007) and the other one is first release Long Term Evolution (LTE) standard (in Oslo, Stockholm, Norway and Sweden since 2009). Fourth generation (4G) wireless networks stand for new infrastructure solutions to provide new services. 4G networks provide high data rate services to have room for multimedia applications such as video conference. 4G networks support global mobility. 4G networks present end-users with high-speed, large volume, good quality and global coverage. Everyone in this world would like to have a seamless connection anytime and anywhere through the best possible network. The 4G wireless system must have the competence to provide high data transfer rates, quality of services and seamless mobility. In 4G, there is a large distribution of heterogeneous networks. The users would like to utilize heterogeneous networks for variety of

10 applications on the basis of their preferences such as high availability, real time and elevated bandwidth. When connections have to switch between heterogeneous networks for high availability reasons and performance, seamless vertical handoff becomes highly essential. [5-8] WiMAX (802.16e) is an emerging wireless networking standard that is designed to provide high speed Internet access to the end user. This provides fixed Internet access and highspeed mobile to the end user. WiMAX is an all-ip solution to provide services for video, data, and voice [9] In a typical 4G network scenario, mobile terminals or handsets with multiple interfaces can choose among the appropriate access link between IEEE 802.11 Wireless Local Area Network (WLAN), IEEE 802.16 Worldwide Interoperability for Microwave Access (WiMAX), Bluetooth and satellite systems in addition to cellular telephony networks and these are reachable globally today. [10] 1.8.1 Key Features of 4G Network The key features of 4G network communication are given below. Anytime and anywhere communications based on IPv6 technology Full packet switched network Integrated services Custom-made service Superior data transmission with speed up to 100Mbps Shore up interactive multimedia, voice, video, wireless internet and other broadband services. Seamless switching (soft handover of the MT from one network to another or from one kind of service to other), variety of services based on Quality of Service (QoS) requirements Global mobility, service portability, scalable mobile networks Support for multimedia services at low per-bit transmission cost Better scheduling and call admission control techniques [11]

11 1.8.2 Comparison between 3G and 4G networks The following table 1.1 gives the comparison between various important parameters of 3G and 4G systems. Table 1.1 Comparison between 3G and 4G networks Parameter 3G 4G Data Throughput Up to 3.1Mbps with an average speed range between 0.5 to 1.5 Mbps Practically speaking 2 to 12 Mbps but potential estimated at a range of 100 to 300 Mbps Peak Upload Rate 5 Mbps 500 Mbps Peak Download Rate 100 Mbps 1 Gbps Switching Technique Packet switching Packet Switching, message Switching Network Architecture Wide area Cell Based Integration of wireless LAN and wide area Service and Applications CDMA 2000, UMTS, Wimax2 and LTE-Advance EDGE etc Forward error correction (FEC) 3G uses turbo code for error correction Concentrated code used for error corrections in 4G Frequency Band 1.8 to 2.5 GHz 2-8 GHz 1.8.3 Physical and MAC Layer specifications One important technology to perform the divisiveness is multi-carrier modulation, which follows frequency division multiplexing. MCM was earlier used in digital audio-video broadcasts and DSL modems. It is a baseband process that uses parallel equal bandwidth channels to transmit information. When implemented with Fast Fourier transform (FFT) techniques, MCM's advantages include evasion of single frequency interferers and improved

12 performance in the inter symbol interference (ISI) environment. However, MCM increases the peak-to-average ratio (PAVR) of the signal and to surmount ISI a guard band is added to the data. In 4G networks, there are two different types of MCM available. They are orthogonal FDM using TDMA and the multi-carrier CDMA. In line with single carrier CDMA systems, the users are multiplexed with orthogonal codes to identify the users distinctly in MC-CDMA. However, in MC-CDMA, several codes are allocated to each user, where the data is spread in time or frequency. Multiple users can access the system simultaneously. In OFDM with TDMA, time intervals are allocated to the users for transmitting and receiving data. The differences between OFDM with MC-CDMA and TDMA can be observed in the types of modulation used in each subcarrier. MC-CDMA uses quadrature phase-shift keying (QPSK), while OFDM with TDMA uses more high-level modulations (HLM), like multilevel quadrature amplitude modulation (M-QAM) (where M = 4 to 256). However, to optimize overall performance of the system, adaptive modulation technique is used where the level of QAM for all subcarriers is selected based on various measured parameters.[12] 1.8.4 Higher Layer Issues in 4G 4G network is a packet-based network. Since it carries voice as well as internet traffic, it provides different level of QoS. Other network level issues include Congestion control, Mobility Management and QoS Guarantees. These issues are discussed below. Congestion Control Congestion control will be a significant issue in the high performance 4G networks. Two basic approaches towards the congestion control that exists are (i) Prevention or avoidance of the congestion and (ii) detection and recovery after congestion. The avoidance scheme requires the network to suitably implement the admission control and scheduling techniques. The detection and retrieval requires feedback traffic management and flow control. A traditional approach is suggested for 4G systems because of a large variety of QoS requirements.

13 Mobility Management Mobility Management includes location registration, handover and paging. The MT should be able to access the services at any place possible. Global roaming can be achieved by with the help of multi-hop networks that comprises the WLANs or the satellite coverage in remote areas. A seamless service is also imperative. The handover techniques should be designed in such a way to make efficient use of the network (routing) and to make sure that handovers are not done frequently. Each MT need not register the location every time. New techniques in location management can also be implemented. Quality of Service (QoS) 4G systems provide real-time and internet-like services. The real-time services can be classified into two kinds. Better-than-best effort Controlled delay : Service should allow dynamically variable delay. Predictive : Service needs upper bound on end-to-end delay. Controlled load : Service needs resources (bandwidth and packet processing) Guaranteed A pre-computed delay bound is required for the service. (eg. Voice) Guaranteed and Controlled Load services will appear in 4G networks. 1.8.5 Need in 4G Networks Seamless Mobility: In order to eliminate connection interruptions and the QoS degradation during intersystem or intra-system roaming, the architecture should support seamless mobility or roaming. Economical: To ensure economical and quick deployment, the architecture should use the existing infrastructures as much as possible and decrease the usage of new infrastructures.

14 Scalable: Assimilation of any number of wireless systems of both existing and future service providers should be supported by the architecture and be able to provide fault tolerance. Security: The architecture should provide a level of security and privacy, which is equivalent or better than the existing wired and wireless networks. [13] 1.8.6 New challenges in 4G Some of the new challenges in 4G network are recognized and listed below. They include Higher frequency reuse leads to smaller cells that may cause intra-cell interference or higher noise figures due to reduced power levels. Multi-access interface, timing and recovery. The Digital to analog conversions at high data rates, multiuser detection and estimation (at base stations), complex error control techniques, smart antennas and dynamic routing will need sophisticated signal processing. Voice over multi-hop networks is likely to be an interesting problem because of the strict delay requirements of voice. Issues in the interface with the ad hoc networks has to be sorted out. 4G systems are expected to interact with other networks like hyperlan, Bluetooth, IEEE802.11b, etc Security will be an imperative issue. Networking protocols that adapt dynamically to the changing channel conditions. A new IP protocol might be needed because of the variable QoS services and the network should do "better than best" effort Seamless roaming and seamless transfer of services. A suitable model has to be proposed to sort out all these challenges in order to achieve seamless and effective mobility.

15 1.9 Handoff in 4G Network In the 4G wireless environment, a mobile user is able to persist in using the mobile device when he moves from one point of attachment to another. This process is called handover. By using this process, the mobile terminal keeps its connection active, when the migration of mobile terminal from the coverage area of one network access point to another access point takes place. Handoff occurs when a Mobile Node (MN) moves from one wireless base station to another. It is the process of maintaining the active session of the user when a mobile terminal changes its connection point to the access network [10]. 1.9.1 Requirements for Handoff Mechanism below. Some of the important and essential requirements for handoff mechanism are listed Handoff Latency Bandwidth Network Cost Network Security Power Consumption Network Throughput User Preferences Received Signal Strength and Velocity [6]

16 1.9.2 Types of Handoff in 4G Network The handoffs are classified into two main types depending upon the access network of each point of attachment. They are listed as below. Horizontal handoff and Vertical handoff Vertical Handoff (VHO) is an important feature of the next wireless communication era [9]. Horizontal handoff takes place when MN moves among similar kind of wireless networks. Vertical handoff occurs when the movement of MN is between heterogeneous wireless networks. 1.9.3 Horizontal Handoff (HHO) Horizontal handoff is the handoff that takes place between two base stations (BSs) of the same system. Horizontal handoff involves a terminal device to change cells within the same type of network (e.g., within a CDMA network) in order to maintain continuity in the service. It is further classified into two types. They are Intra-system handoff and Link-layer handoff Intra-system handoff It is the Horizontal handoff that takes place between two BSs that fit in to two different FAs and both FAs belong to the similar system and hence to the same Gateway Foreign Agent (GFA).

17 Link-layer handoff It is the Horizontal handoff that takes place between two BSs, under the same Foreign Agent (FA). [6] 1.9.4 Vertical Handoff (VHO) Vertical handoff (Inter-System Handoff) is defined as the Handoff that occurs between two Base Stations (BS) belonging to two different systems and two different Gateway Foreign Agents (GFAS) [14-15]. Vertical handoff refers to a network node that changes the type of connectivity it uses to access a supporting infrastructure in order to support node mobility. For example, a suitably equipped laptop might be able to use both technology for Internet access and a high speed wireless LAN. Wireless LAN connections usually provide higher speeds, while cellular technologies provide more ubiquitous coverage. While the wireless LAN is unavailable, the laptop user might want to use a wireless LAN connection whenever one is available, and to fall over to a cellular connection. Vertical handover represents the automatic fall over from one technology to another to maintain communication. The vertical handoff mechanism allows a terminal device to change networks between different types of networks like 3G and 4G networks, in a way that is entirely transparent to end user applications. The vertical handoff process involves three main phases, namely system discovery, vertical handoff decision, and VHO execution. During the system discovery phase, the mobile terminal determines which networks can be used. These networks may also advertise the supported data rates and Quality of Service (QoS) parameters. The mobile terminal determines whether the connections should continue using the current network or be switched to different networks during the VHO decision phase. The decision may depend on various parameters or metrics including the type of the application (e.g., streaming, conversational), access cost, minimum bandwidth and delay as required by the application, user preferences and the transmit power. [6]

18 The ability of MTs to seamlessly transfer to the best access link among all available candidates with no perceivable intermission to an ongoing conversation (which could be a video or voice session) i.e., between heterogeneous networks are referred to as seamless vertical handovers. The emerging IEEE 802.21 standard creates a framework to support protocols for enabling seamless vertical handovers [16]. But providing seamless mobility and service continuity (i.e., minimal service disruption during roaming) support based on intelligent and efficient techniques is a critical issue because the seamless handoff schemes should have lower packet loss, minimum handoff latency, lower signaling overhead and limited handoff failure or blocking. [17]. In many situations unnecessary handoffs and handover failures are triggered causing reduction in throughput, degradation of services and increase the packet loss and blocking probability.[18] 1.9.5 Vertical handoff and its issues Vertical handoff decision algorithms assist mobile terminals to choose the best network to connect among all the available candidates and need to be designed to provide the required Quality of Service (QoS) to a variety of applications while allowing seamless roaming among variety of access network technologies. In VHD algorithms, criteria such as power consumption, cost of services and the velocity of the mobile terminal may be taken into consideration to improve user satisfaction [2]. Wireless networks can integrate various heterogeneous radio access technologies as UMTS, GSM, Wimax, WLAN etc. The main purpose of interconnecting these heterogeneous networks is to provide efficient performance in achieving a high data rate and support real time applications.[19] Received Signal Strength (RSS) is the most widely used criterion because it is easy to measure and is directly related to the service quality. It has to deal with issues like Network connection time, Signal strength, Power consumption, Available bandwidth, Security, monetary cost and User preferences. VHD algorithms can be quantitatively compared under various usage scenarios by measuring the number of handovers, the mean and maximum handover delays,

19 overall throughput of a session maintained over a typical mobility pattern and the number of failed handovers due to incorrect decisions [20]. It is the need of the hour to develop algorithms for connection management and optimal resource allocation for seamless mobility in vertical handoff performance [21]. It is vital to provide service continuity and seamless mobility (i.e., minimal service disruption during roaming) support based on efficient and intelligent techniques. This means that seamless handoff schemes should have following features like low packet loss, minimum handoff latency, lower signaling overhead and limited handoff failure or blocking [22]. The seamless and efficient handoff between different access technologies (vertical handoff) is a challenging problem. The heterogeneous co-existence of access technologies with largely different characteristics creates a decision problem of determining the best available network at the best time to reduce the unnecessary handoffs [23]. The most imperative and challenging issue is seamless handoff management in NGWS, which is used to ensure the QoS [24]. If QoS inconsistency prevails, the multimedia session will have different QoS levels in these network domains and hence seamless continuity will not be viable [25]. A challenging issue in providing seamless roaming is to select an appropriate interface to ensure that a MN remains connected to the network. Also, mobility management as well as the interworking and integration of the existing wireless systems become very difficult due to their specific characteristics [26]. False handoff initiation problem becomes increasingly severe on decreasing the size of the cell. The data rate capacity increases when the cell size of wireless system decreases [27]. Next-Generation Wireless Networks (NGWN) are expected to exhibit heterogeneity in terms of personalized and user-oriented services, wireless access technologies, high usability, increased capacity and application requirements. With NGWN, users will have greater demands for QoS guarantees, seamless roaming across different wireless networks and support of various

20 services like multimedia applications. The handoff latency is the time interval during which an MN cannot send or receive any data traffic during handoffs that is composed of L2 (link switching) and L3 (IP layer) handoff latencies. The overall handoff latency may be sufficiently long which results in packet loss that is not suitable for real-time applications like Voice over IP (VoIP). Activating air interface every time consumes more bandwidth and battery power even if the device unit is not sending or receiving any packets. The handoff decision refers to the process of selecting the appropriate moment to perform the handoff. So it is critical to avoid keeping idle air interfaces perpetually on [28-29]. 1.9.6 Motivation of the study There are large varieties of heterogeneous networks in 4G. The users for variety of applications would like to employ heterogeneous networks on the basis of their preferences such as real time, high availability and high bandwidth. When connections have to switch between heterogeneous networks for performance and high availability reasons, seamless vertical handoff is necessary [5-8]. The existing techniques on vertical handoff decision for heterogeneous networks as reported in the literature concentrate on any one or some of the parameters like signal strength, network coverage area, data rate, battery efficiency, velocity of MT and network latency. But for effective handoff decision and network selection, all these parameters have to be considered. To perform the vertical handoff between pairs of different types of networks in the incidence of 2G, 3G, WLAN, WMAN, satellite, etc along with the fulfillment of quality of service (QoS) requirements is the main challenge in 4G networks. The lack of QoS can cause break in network during handoff or loss of network at remote condition. All these drawbacks arising from the various existing models have motivated to identify a fresh and novel proposal of providing a QoS aware vertical handover decision (QAVHD) in 4G

21 networks. These drawbacks have also motivated to provide a better method to guarantee QoS in the network by providing efficient bandwidth utilization method and to provide a mapping method that helps in improving the transmission quality. 1.10 Objectives of the study To provide Quality of Service (QoS) based handoff management for 4G networks to a wide range of applications among a multitude of access network technologies. To determine various network parameters like Received Signal Strength (RSS), Network coverage area (NCA), Available Bandwidth (AB), Data Rate (DR), Velocity of Mobile Terminal (v) and Network Latency (NL) for the interfering networks. To compare and identify a better network from the estimated network parameters in order to provide better QoS. To estimate and analyse the Mobile Terminal (MT) information like battery Depletion Rate (R b ), Transmission Power (P tx ) and Bandwidth Capability (C bw ). To develop an algorithm for connection management for seamless mobility which handles the handoff latency and failure for providing better resource allocation to the mobile users in order to avoid any kind of overhead in the network. To simulate and analyse the proposed QAVHD model using NS-2 tools. To evaluate the performance of the proposed model by comparing with existing Inter- RAT model in terms of the metrics like Throughput, Delay based on Data Rate (DR) and Time. To provide a model for an Efficient Service time Prediction and effective Bandwidth Reservation Technique (ESPBR) for Vertical Handoff in 4G Networks.

22 To compare the proposed model ESPBR having Minimal bandwidth Guarantee Best Effort (MBGE) with Efficient Bandwidth Borrowing Management Module EBBM Technique. To calculate Time Threshold by estimating Distance, Time and Data Rate using mathematical modeling and probability calculation for minimizing handover failures. To estimate travelling time prediction for minimizing unnecessary handovers along with the Bandwidth reservation in order to provide efficient connection management for seamless mobility. To simulate the proposed Efficient Service Time Prediction and Bandwidth Reservation (ESPBR) scheme using NS-2 tools. To evaluate and analyse the performance of ESPBR model by comparing with EBBM model using the metrics like Throughput, Delay, Drop and Delivery Ratio (based on Rate and Time). 1.11 Problem Identification and proposed methodology User Equipment (UE) creates certain measurements by searching the network range, bandwidth and quality of the service at a particular interval of time for determining link quality in a radio network. By the acquired measurement a report is created in MT that is used during handover for determining the operator and range of bandwidth to be allotted in new network. During handoff process the report created is analyzed to check whether any new attachment is found or the old network strength is reduced. In the present study, two different problems related to hand off mechanism in 4G networks are identified and a suitable proposal for each problem is defined and executed. They are explained as below.

23 To overcome the issues on the handoff mechanism in 4G network, a proposal on QoS based handoff management (QAVHD) model for 4G network is proposed in this study. In this method, initially, when MT on movement finds a new network, it collects the QoS information of the respective network that includes signal strength, network coverage area, and data rate, and available bandwidth, velocity of MT and network latency. Then MT compares the estimated measurements with its old network and current network, which provides the better QoS, which is selected as the current network. The old network then performs the data transmission to the new network. In the system design, UMTS and WiMAX networks are considered in which the vertical handoff is performed. To provide a good solution on the problem of inefficient handoff latency, failure, and load balancing at time of vertical handoff, a new proposal Efficient Service time Prediction and Bandwidth Reservation Technique (ESPBR) is also suggested in the present study. An algorithm is also developed for connection management for seamless mobility that handles the handoff latency, failure and provides better resource allocation for mobile user in order to avoid any kind of overhead in the network. The proposed method (ESPBR) is divided into two phases. In the first phase, an attempt is made to solve the latency and failure and the second phase of the proposed method is able to solve the problem of load balancing. 1.12 Organisation of the Thesis First chapter narrates Introduction about generation of networks, a basic idea about 4G network and its various features. It also explains the types of handoffs in 4G network like horizontal and vertical handoffs and also their issues and various requirements. Second chapter covers literature survey which has helped to learn the various available technologies involved in providing QoS in 4G networks and also to learn about various methodologies used for resource allocation for mobile users. This helped to learn the merits and demerits of the various models and has paved way to identify a suitable research problem.

24 Third chapter briefs a model regarding QoS based handover management in 4G networks. In this method, QoS Aware Vertical Handoff Decision (QAVHD) is compared with the existing Inter-RAT model. The performance of the suggested new model is analysed and discussed in terms of metrics like throughput, handoff Latency and delay with respect to Rate and Time. Fourth chapter deals a model for Efficient Service time Prediction and Bandwidth Reservation Technique (ESPBR) for Vertical Handoff in 4G Networks. In this model, an algorithm is developed for connection management for seamless mobility that handles the handoff latency, failure and provides better resource allocation for mobile user in order to avoid any kind of overhead in the network. The proposed Efficient Service time Prediction and Bandwidth Reservation (ESPBR) is compared with EBBM Technique. The results are computed and interpreted in terms of performance using the metrics like throughput, delay, drop and delivery ratio with respect to Rate and Time. Fifth Chapter presents summary and conclusion of the work done which clearly states that the proposed approach enhances the network throughput and reduces latency. It is also concluded that the method taken for research provides seamless handoff and an efficient bandwidth estimation technique. Various challenges of the study and scope for further research are also given in this chapter.