Handover in Mobile Wireless Communication Network - A Review <s> International Journal of Advanced Engineering, Management and Science (IJAEMS) <s> In the next generation heterogeneous wireless networks, a user with a multi-interface terminal may have a network access from different service providers using various technologies. It is believed that handover decision is based on multiple criteria as well as user preference. Various approaches have been proposed to solve the handover decision problem, but the choice of decision method appears to be arbitrary and some of the methods even give disputable results. In this paper, a new handover criteria is introduced along with a new handover decision strategy. In addition, handover decision is identified us a fuzzy multiple attribute decision making (MADM) problem, and fuzzy logic is applied to deal with the imprecise information of some criteria and user preference. After a systematic analysis of various fuzzy MADM methods, a feasible approach is presented. In the end, examples are provided illustrating the proposed methods and the sensitivity of the methods is also analysed. <s> BIB001 </s> Handover in Mobile Wireless Communication Network - A Review <s> International Journal of Advanced Engineering, Management and Science (IJAEMS) <s> This paper describes the handover mechanism in the standard 802.16e, which has implemented three handover methods — Hard Handover (HHO), Fast Base Station Switching (FBSS) and Macro Diversity Handover (MDHO) at this moment. Moreover, the handoff scheme is presented based on fuzzy logic. The mechanism takes under consideration three criteria: geographical data, received power level and used bandwidth of each base station. Fuzzy logic has been used to come with the decision about the target BS to be chosen such that the switching between BSs is more efficient. <s> BIB002 </s> Handover in Mobile Wireless Communication Network - A Review <s> International Journal of Advanced Engineering, Management and Science (IJAEMS) <s> Intersystem mobility having no awkward transitions or indications of disparity, roaming across wireless access networks is one of the main features of Mobile WiMAX. In this paper, we propose a mobility prediction method based on fuzzy logic control and an algorithm similar to the fuzzy c- mean partitioning to predict the movement patterns and handover times by measuring mobile users’ velocity and monitoring the received signal strength of the serving base stations and target base stations simultaneously. With the help of the prediction, reserving the required amount of resources for the upcoming handover event at the target base station can occur before handover initiation and execution. This would grant mobile users of high priority connections (e.g., UGS based VoIP connection) accessibility to the target base station with no connection termination at various loading situations. The viability and efficiency of the method is demonstrated through experiments conducted with system parameters and propagation model defined by WiMAX Forum. This is to show that the prediction of the future handover times based on predicted received signal strength trend is accurate to maintain the promised QoS level and to reduce the total handover delays caused by layer-3 handover initiation. This allows Layer-3 handover initiation to occur before Layer-2 initiation. <s> BIB003 </s> Handover in Mobile Wireless Communication Network - A Review <s> International Journal of Advanced Engineering, Management and Science (IJAEMS) <s> This paper presents a mobility improvement handover algorithm with less scan time implementation for Mobile WiMAX. Mobile WiMAX is a wireless technology based on IEEE802.16e for broadband wireless access. Mobile WiMAX introduces the most significant new feature, mobility to support for handovers, which can be considered as a basic requirement for mobile communication system. The mandatory handoff method is Hard Handoff for Mobile WiMAX and other two optional soft handoff methods are Macro Diversity Handoff and Fast Base Station Switching Handoff method. Handover delay generates during data transmission but handover delay should be less than 50milli second for real time applications such as VoIP. The existing draft standard considers only the received signal strength (RSS) when deciding handover. The mobility improvement handover scheme that depends upon the velocity factor has been taken into consideration in this paper. The proposed scheme skips some unnecessary handover stages, reduces handover delay by adjusting the handover parameters viz. handover RSS trigger and threshold handover RSS trigger value to improve the velocity of the mobile station. The proposed scenario has been implemented using QualNet network simulator which has lead to less handover time. <s> BIB004 </s> Handover in Mobile Wireless Communication Network - A Review <s> International Journal of Advanced Engineering, Management and Science (IJAEMS) <s> Summary This article analyzes the performance of vertical handover between UMTS and WiMAX networks by defining development architecture for supporting mobility between these two technologies. First, architectures and principles of operation of networks UMTS and WiMAX are detailed and compared. Then the main protocols of mobility are considered as support of handover between UMTS and WiMAX (802.16). Finally, simulation architecture is presented followed by performance analysis modelled by the simulator NS2 in the context of connection-oriented communication. <s> BIB005 </s> Handover in Mobile Wireless Communication Network - A Review <s> International Journal of Advanced Engineering, Management and Science (IJAEMS) <s> Acquiring seamless handover in IP multimedia subsystem (IMS)-based heterogeneous internetworking environment still remains an unsolved issue. It is highly difficult to achieve seamless handover with the conventional session initiation protocol (SIP) due to its poor performance during vertical handover. In this paper, a novel SIP-based scheme called SIP Prior Handover with a cross-layer design utilizing Media Independent Handover Services is modeled to reduce the IMS session re-setup delay in a Worldwide Interoperability for Microwave Access (WiMAX)/Long Term Evolution (LTE) heterogeneous environment. The proposed scheme further reduces the IMS session re-setup delay by reducing the number of SIP messages exchanged during vertical handover. We have developed a simulating environment using NS2 for a WiMAX/LTE interworking architecture and evaluated its performance. We have also developed a mathematical model for the IMS session re-setup delay based on queuing theory. The simulation results are compared for handover delay, packet loss, SINR and throughput. The proposed design shows an improvement of 18 % when compared with previous approaches during vertical handover from WiMAX to LTE and vice versa and suits well for supporting real-time applications to mobile users. <s> BIB006
There is need to develop functions which relate received signal strength (RSS) with velocity in order to utilize it with other factors effective handover. In  ,AratiRana et al proposed a vertical handover method which reduced the network latency. The access router periodically send router advertisement which is analysed when a mobile moves from one BS place to another BS, a care-of address is generated through communication with the subnet of that particular network which is then configured in the eNB. Verification of duplicate address is carried out by the UE to check for duplicate address in the same radio range. A reconfiguration of the new care-of address is carried out if there is any duplicate address. The algorithm is time consuming therefore, the latency is affected. According to BIB001 , to switch from one network to another without disconnection the latency should be as minimum as possible.  Sanjay et al proposed a requirement of vertical handover mechanism. Vertical handover is a critical component of forth generation (4G) networks. This is because of the switching amongst HetNets. This poses serious HO challenges as a result of its multiple requirements for VHO. Above proposed parameters are not sufficient for taking efficient decision of vertical handover. Actually, it needs to consider lot many statics and the dynamics parameters of the network too. In  ,Tokekar et al proposed handover technique which depends on static and dynamic parameters. The static signal strength is not always sufficient to initiate the handover process and therefore network load, type of application, speed of the mobile node (MN) may be considered along with it. In  ,kolipaka et al combined wireless mesh network architecture and joint admission control with VHO algorithm with a case study of WAN and WiMax. QoS is guaranteed by handing over to another network to support the traffic flows in WLAN. The E2E delay and throughput is improved with this algorithm. It is noteworthy that the algorithm focuses on QoS, but there is also need to reduce the number of handover (network latency) and which type of parameters should considered for proper vertical handover decision. In  , Phemina and Sendhilnathan, proposed a Mobility management in 4G wireless network using FL (fuzzy logic). The Algorithm used five input parameters which are "Received Signal Strength (RSS), BW, Monetary Cost, User Preference (UP) and UE Velocity (V)" while the output is the HO decision. The author noted that the higher the number of rules the better the convergence of the handover decision which means the more the input to the fuzzy inference to the system the better the handover decision. In vertical handover decision, many issues have to be optimized for performance improvement. Such problems are: overlay scenario with multi-criterion, which can easily be handled by soft computing techniques. In  , Nasser proposed A HO scheme between a cellular mobile system and a WiMAX mobile system in physical layer mode for high data rates, high mobility and traffic congestion reduction. The algorithm considered traffic load, signal quality and mobile terminal (MT) with an assumption that there is perfect synchronization between the Cellular mobile system and WiMax system.  Proposed an inter-WiMax handover with initial ranging and periodic ranging. The initial ranging is to determine the transmit power of the MT to BS terminal and at the second ranging. A time alignment message is sent from eNB to UE as it moves around the radio coverage area. The HO between WiMAX and UMTS system is given in BIB005 . The algorithm focused on the moving mobiles and performance evaluation is based on the packet lost rate of the intersystem HO between the two wireless networks UMTS and WiMAX. The performance as shown by the simulation results is satisfactory, but decreases with the increase in the mobile speed. In BIB006 , Edward proposed a WiMAX /LTE HetNet HO algorithm. The author modeled a scheme called Session initiation protocol prior handover with cross-layer design using MIH service to reduce the session re-setup delay in a WiMAX/Long Term Evolution (LTE) HetNet. The work also reduced IP multimedia subsystem session re-setup by minimizing the number of SIP message exchange during vertical handover. THE proposed method was simulated on NS2 environment and the simulation result shows 18% improvement in comparison with former approaches during VHO between WiMAX and LTE. In [30] , the author proposed a vertical handover between the Wi-Max and WIFI Networks by changing the parametric In  ,the author proposed an Adaptive Handover Scheme which is based on velocity for Mobile WiMAX. It should be noted that the mobility of the mobile users is a critical and important factor as far as wireless communication is concerned. The threshold changes as the velocity increases to avoid unnecessary handover, delay and thereby optimising the resource utilization.In  , a soft-handover was proposed. The algorithm selects a potential base station while relating handover latency with UE velocity. The algorithm performance was evaluated with metrics BER and transmission time of mobile WiMAX using BPSK, QPSK & 16QAM modulation techniques. The author noted that, seamless handover in mobile WiMAX is achievable with the algorithm when the mobile station travels at the speed of 20 m/s with dramatically low latency. However, achieving the mobility of up to 120 km/h while the latency is less than 50ms with an associated packet loss that is less than 1percenit is still a challenging issue. In  ,the author proposed a Fuzzy Logic Based SelfAdaptive Handover Algorithm for Mobile WiMAX (FuzSAHO). The fuzzy logic deals with either the Handover should be initiated or not. The criteria used include the RSSI and MS velocity. The algorithm simulation results show that Ping-Pong and delay is reduced. "In comparison with RSSI based and mobility improved algorithms, FuSAHO reduces the number of handover by 12.5 and 7.5 %, respectively when the MS velocity is <17 m/s. In term of handover delay, the proposed algorithm shows an improvement of 27.8 and 8 % as compared to both conventional and MIHO algorithms, respectively" as a result the proposed FuzSAHO is better. Nevertheless, there is need to check the implication of high UE velocity on the algorithm performance. There are many strategies for optimising handover in order to achieve a minimal handover delay. The authors in [34 -38] focused on one of the strategies where small message is involved in handover execution in order to achieve faster handover. Another strategy is to make the scanning threshold adaptive as regards cell reselection phase, therefore, cell information of the neighbouring cell is necessary BIB003 . Authors in BIB003 used a technique that makes the UE to carry out pre-scanning before actual HO using fuzzy logic based movement prediction. Therefore, there is a resource reservation for potential HO at the TBS before the HO is initiated and execution. The third strategy has to do with efficient selection of HO decision. In BIB004 , the author present logarithm function assisted for the mobility improved handover (MIHO) algorithm which is velocity based. The results confirmed the importance of UE velocity on HO algorithm efficiency. However, velocity alone is not sufficient to achieve a seamless HO. The author in BIB002 has suggested a fuzzy logic approach to enhance the eNB selection. No result was reported by the author  . Fuzzy logic has been used in the cellular network handover systems extensively, and it has proved efficient as it introduces a better handover performance than the conventional handover  .