Handoff delay Optimization in IEEE e (Mobile WiMAX) using Fuzzy Expert System

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1 Handoff delay Optimization in IEEE e (Mobile WiMAX) using Fuzzy Expert System Pallavi Sharma Department of Electronics and Harsukhpreet Singh Department of Electronics and Anurag Sharma Department Of Electronics and Abstract Mobile WiMAX is the technology that guarantee broadband wireless access over long distance. In order to maintain mobility and constant network connectivity in mobile WiMAX, it is necessary to provide handoff. Handoff is an crucial process in wireless networks to promise continuous and effective services. But in Handoff there occurs a problem called Handoff delay. In order to optimize handoff delay in Horizontal handoff of Mobile WiMAX we use fuzzy logic in this paper. Mobile WiMAX is facing problem related to handoff delay which should be less than 50 milliseconds so in this paper we proposed a fuzzy based model which reduces the delay and gives better result. As handover delay reduces packet loss also reduces and system efficiency increases. At the end Simulation Results shows that in our proposed algorithm handoff delay reduces more than half of that valid handoff delay. Index Terms IEEE e, Fuzzy logic, Layer 2 handoff, Layer 3 handoff. I INTRODUCTION WiMAX is the technology that is able to provide triple (voice, video and data) services. Mobility in Mobile WiMAX is still the issue that is to be resolved. Handoff or Handover delay is the parameter that effect mobility [14]. Handover delay should be less than 50millisec if it exceeds 50 milli sec it may result in the packet loss and handoff failure[21].mobile WiMAX attracting huge amount of users due to its faster speed and more coverage area. Mobility management is one of the important issues in Mobile WiMAX that is to be resolved in order to achieve better services. Mobility management depends upon the two important parameters that is the location management and the handoff management. Location management is used to locate the location of the user and make efficient connections. Handover management involves the relocation of user s applications from one base station (BS) to another base station. In this paper, we concentrate on the study of handover management; more especially on handoff delay in case of horizontal handoff [15].Handoff is basically used to connect one base station to another base station in order to remain the continuity of the call. Handoff is executed in three steps that are handoff initiation, handoff decision and handoff execution. The conventional handover decision in mobile WiMAX is based on a single approach which is usually based on the quality of signal or the received signal strength indicator (RSSI) with other handover parameters being fixed. Mobile WiMAX supports smaller cell size and high mobility among the base station (BS) coverage area in which MS will practices regular handoff between BSs. Handoff criteria and handoff decisions are main important factors that determine a handoff system Efficiency. Sometimes unnecessary handoffs occur at base station which is referred to as ping pong effect. This effect also causes handoff delay [15]. Handoff in mobile WiMAX is broadly classified into two types that are horizontal handoff and vertical handoff. Figure 1depicts the Horizontal handoff which is performed between same networks. Figure 2 depicts Vertical Handoff which is performed in between different types of networks. Horizontal handoff is also called as layer 2 handoff of mobile WiMAX whereas vertical handoff is called as layer 3 handoff of mobile WiMAX. Layer 2 Handoff of mobile WiMAX consist of hard and soft handoff. Hard handoff is based on the principle of break before make mechanism means before connecting to the new base station the connections with the current base station should be broken. Hard handoff is also occurs at a lower mobile speed. Soft Handoff is based on the principle of make before break mechanism. In this connections remain until we get new connection. Soft handoff is basically used when the mobile speed is high. Layer 3 Protocols consist of Mobile IP, Proxy Mobile IP [12]. Figure 1: Horizontal Handoff [12] 5

2 Figure 2: Vertical Handoff [12] Traditionally, a fuzzy logic based expert system consists of three main categories; fuzzifier, fuzzy inference engine and rule base, defuzzification as shown in Figure 3 In the fuzzifier stage, the input parameters of the fuzzy logic system will be converted into fuzzy set. The fuzzy set contains different level of membership in a set as low, medium, high. In fuzzy inference engine rules are evaluated by using if-else rules conditions. In the last defuzzification stage we further get the crisp outputs from fuzzy outputs. In our algorithm we use centroid method fordefuzzification. FUZZIFIER Figure 3:Basic fuzzy logic [15] RULES INFERENCE ENGINE II RELATED WORK WIFI DEFUZZIFIER In this part, we shall discuss some work related to the Handoff in mobile WiMAX and the handoff delay in mobile WiMAX. Kozlowska E. [2007] presented the handover mechanism in mobile WiMAX which has considered three handover methods - Hard Handover (HHO), Fast Base Station Switching (FBSS) and Macro Diversity Handover (MDHO) using Fuzzy Logic. The handoff mechanism presented in this paper result in more efficient switching between BSs [7]. Damhuis J. [2008] presented handover within WiMAX and between and WLAN. In this Author discussed basically Layer2 and Layer3 Protocols of WiMAX [13].Mohammed A. et al [2013] proposed a fuzzy based algorithm which is used to overcome the handoff delay and ping pong effect. Traditionally only receiver signal strength is used to calculate handoff. In this author presented more parameters to introduce the concept of handoff delay [15]. III System Model Fuzzy Logic based algorithm is proposed in this paper in order to improve handover delay in mobile WiMAX. In the current paper we are using Fuzzy toolbox in Matlab for our simulation purpose. Handoff delay can be reduced by using certain input parameters by varying them we can conclude the results. The handoff type we discussed in this is layer 2 or horizontal handoff. Horizontal handoff occurs in between the same cells as in case of wimax and wimax or wlan and wlan.in our proposed model we consider two cells of WiMAX. The input parameters and output parameters used in this proposed algorithm are explained below:- A. Input Parameters In this proposed fuzzy model certain input parameters are chosen that are used to decide whether handoff is needed in the network or not. These parameters are also used to check whether handoff delay occurs in the network or not.by varying these parameters we can conclude the details related to handoff delay factor. Best Receiver signal strength (RSS) is used as the first and foremost input parameter. It is defined as the best receiver power level detected by mobile station. Its value is always taken as negative. In this case we can take distance of the cell in accordance to the need of the network. By varying RSS handoff decision varies as a result of which handoff delay factor varies [3]. Base station load data is used as a input parameter to examine the load of the base station with the traffic in the form of data exchanged between mobile station and its correspondent [12]. Base station load video is used to calculate the load of the base station with the traffic in the form of video exchanged between mobile station and its correspondent. If the load of the base station varies continuously it will change the handoff process frequently as a result of which handoff and handoff delay varies.[12] Base station load VoIP defines the load of the base station with the traffic in the form of VoIP exchanged between mobile station and its correspondent [21]. Timer is used to set a certain time for the mobile station to still check the load of the current base station so that if there is vacancy so that handoff should not happen so this overall increases the chances of no handoff increase [12]. Mobile speed is used as a main input parameter to define the actual speed of Mobile station with which it is moving. In order to find the mobility of the network this parameter is used foremost [15]. Fading is used to find the amount of signal degradation due to multipath propagation [22]. Hand off Delay is used to define the delay occurs in the handoff procedure to happen. Generally Handoff delay in Mobile WiMAX should be less than 50 milli seconds [21]. B. Output Parameters In order to model and simulate fuzzy expert system for handoff delay measurement certain output parameters should be judge for examination. This paper concentrates on handoff delay factor so the handoff decision should be taken as output parameters. As we are dealing with layer 2 handoff of mobile WiMAX so the protocols of layer 2 WiMAX is used as a output parameter. Hard Handoff is used as a output parameter when we need Break before make mechanism. In this the connection with the current base station will break in 6

3 order to make new connection. This is also used when the speed of the moving vehicle is slow [12]. Soft Handoff is used as a output parameter When we need Make Before Make Mechanism. In this the connections with the current base station will remain connected until we get another strong connection [15]. In order to design fuzzy expert system model for handoff delay we have to define Membership functions for both input and output parameters. Some of the Membership functions are defined as follows:- Figure 4: Membership Plot for fading Figure 5: Membership Plot for Receiver signal strength Figure 4 shows the membership plot for Fading. It consists of three linguistic variables low, medium and high. In this we use trapezoidal membership function for linguistic variables. For Low linguistic variable the range occurs from 0% to near about 35 %.For Medium the range is from 25% to near about 67%.For high the range is from 62% to 100%.Figure 5 shows the membership plot for Receiver signal strength(rss). RSS is measured in dbm. Its value lies in between -160dbm to - 137dbm for low linguistic variable. For medium its range is from -147dbm to -114dbm. For high its range lies between - 132dbm to -90dbm.After defining Membership function for both inputs and outputs the next step is to write rules. Rules evaluation takes place in rule viewer window of fuzzy logic tool box.for Writing rules the if-else conditions are used in Fuzzy logic.some of the rules are defined in Table 1.1. Table1.1 depicts some of the rules that are used to design the model for handoff delay in mobile WiMAX. In the above table R10 defines the receiver signal strength for a distance of10km.bsvi defines the base station load for video.bsd defines the base station data load.bsvo defines the base station load for voice over ip or we can say that for real time applications. Timer is used for final check that whether handoff is needed or not. Speed depicts the mobile speed or with which speed the mobile station is moving. F depicts the fading. Fading may be defined as the signal fluctuation due to multipath propagation. HD defines the handoff dealy.at last there is the output condition that which handoff is needed. Based on the rules the handoff decision takes place whether it should soft or hard handoff. IV RESULTS In Fuzzy based system model after designing the model we can analyze the result using rule viewer and surface plots. Firstly we describe the result using rule viewer than surface plot. There is a bar in rule viewer that is shown in red colour in the centre of the rules by moving this bar the values of the parameters goes on changing. In case of hard handover handoff delay becomes longer. Next part of the results is the surface plots which are described as in the next section.figure 7 shows the surface plot of handoff delay between fading and hard handoff. And the hard handoff value comes in this part is 50%.Means in case when half of the handoff is hard handoff then also handoff delay is very much less. Fading is also introduced so that we can check the results of handoff delay in all situations. Figure 8 shows the surface plot between mobile speed and hard handoff. When Mobile station is moving then we can say that mobility is introduced in the network. Mobility should be high in order to develop a network of higher efficiency. Figure 8 shows that the value of handoff delay comes between 5 to 30 milliseconds. Handoff delay keeps on changing in this case as there speed occurs and mobile station is moving continuously. In this case also hard handoff value comes to be 50%.Figure 9 shows the handoff delay between receiver signal strength and soft handoff. The value of handoff delay is 30milliseconds in this case. Soft handoff comes under this condition is 70%.Soft handoff is optional on case of Mobile WiMAX but by introducing soft handoff we can improve the WiMAX network efficiency thus improves the quality of service. Figure 10 shows the surface plot of handoff delay between soft handoff and timer. Its maximum value lies at 32 milliseconds and minimum peak lies at near about 15 milliseconds. In this case value of soft handoff comes to be 70%. Figure 6:Rule viewer window results 7

4 Figure 7: Surface plot of handoff delay between Fading and Hard handoff V Conclusion In Mobile WiMAX network mobility management is the main issue.as mobile station is moving continuously so handoff should be continuously done in order to maintain the services. As a result handoff delay should be as minimum as possible. As handoff delay reduces packet loss ratio also reduces. Handoff latency and ping pong effect also decreases by handoff delay reduction. So overall network quality of service enhances by reducing handoff delay. Simulation results show that by using fuzzy logic handoff delay reduces.for future prospective we can work on handoff latency and ping pong effect using fuzzy expert system. Figure 8:Surface plot of handoff delay between Mobile Speed and Hard handoff Figure 9:Surface plot of handoff delay between Receiver signal strength and soft handoff Figure 10:Surface plot of handoff delay between Timer and Soft handoff REFERENCES [1] Seyedzadegan M., Mohamed O., IEEE : WiMAX Overview, WiMAX Architecture, International Journal of Computer Theory and Engineering, Vol.5, [2] Prakash G., Pal S., Wimax Technology And Its Applications, International Journal of Engineering Research and Applications (IJERA), Vol. 1, pp , [3] He Q., Chen G., Zhang L., A Vertical Handoff Decision Algorithm Based on Fuzzy Control in WiMAX and TD-SCDMA Heterogeneous Wireless Networks, Proc. of IEEE, Wireless s Networking and Mobile Computing (WiCoM), [4] Khan A., Anwer W., Munir E., Handover Techniques in Mobile WiMAX Networks Analysis and Comparison, Middle-East Journal of Scientific Research, [5] Suganya C., Sumithra A., Karthik A., Handovers in WiMAX Technology, Proc. of IEEE, Information and Embedded Systems (ICICES),2014. [6] Dadhich R., Narang G., Yadav D., Analysis and Literature Review of IEEE e (Mobile WiMAX) Security, International Journal of Engineering and Advanced Technology (IJEAT), ISSN: , Vol.1, [7] Kozlowska E., Optimization of Handover Mechanism in e using Fuzzy Logic, IFIP International Federation for Information Processing, Vol 245,2007. [8] Angoma B., Erradi M., Benkaouz Y., HaVe-2W3G: A Vertical Handoff Solution between WLAN, WiMAX and 3G Networks, IEEE [9] Ansari A., Saxena P., Gupta K., Fuzzy Rule based Channel Allocation for Efficient Spectrum Management in WiMAX Networks, Proc. of Elsvier, Advances in, Network, and Computing(CNC),2014. [10] Semenova O., Semenov A., Voznyak O., Mostoviy D., Dudatyev I., The fuzzy-controller for WiMAX networks, Proc of IEEE, International Siberian Conference on Control and s (SIBCON),2015. [11] Choudhary S.,Dubey S.,Gupta R., Wimax Technology: A Secure Broadband Connectivity for Governments, Military Services in Rural/Strategic Isolated Locations, International Journal of Advanced Research in Computer Science and Software Engineering,ISSN: X,Vol- 3, [12] Bchini T., Tabbane N., Tabbane S., Chaput E., Beylot A., Fuzzy logic based layers 2 and 3 handovers in IEEE e network, Proc. of science direct, Computer s 33, pp , [13] Damhuis J., Seamless handover within WiMAX and between WiMAX and WLAN, Twente Student Conference on IT, [14] Khateeb M., Hashim A., A Fuzzy-based Mobility Prediction in the IEEE e, International Journal of Networks and Information Security (IJCNIS) Vol. 1,2009. [15] Mohammed A.,Ben M., Mohd. B., Noordin I., Chee N., Fuzzy Logic Based Self-Adaptive Handover Algorithm for Mobile WiMAX, Proc. Of Springer, Wireless Pers Commun,pp ,

5 [16] Kim M., Kim J., Kim H., A Proxy Mobile IP based Layer-3 Handover Scheme for Mobile WiMAX based Wireless Mesh Networks, Proceeding of IEEE,2010. [17] Grine M., Najid A., Messoussi R., Performance Optimization of WiMAX Mobile Networks with a Predictive Handover Process, International Journal of Distributed and Parallel Systems (IJDPS) Vol.3, [18] Soni H., Sood V., Sheetal A., Modeling of Fuzzy Based Handoff Decision Controller, International Journal of Advanced Research in Computer and Engineering Vol. 4, [19] Khan S., Lee J.,Khan G., Evaluation Of Parameters For Improving Handoff Performance In Mobile Wimax networks, International Journal of Distributed and Parallel Systems (IJDPS) Vol.3,2012. [20] Khan A., Anwer W.,Munir E., Handover Techniques in Mobile WiMAX Networks: Analysis and Comparison, Middle-East Journal of Scientific Research, DOI: ,2013. [21] Anwar M., Khosla A., Sood N., A Mobility Improvement Handover scheme for Mobile WiMAX, International Journal of Computer Applications, Vol. 11, [22] Rege K., Nanda S., Weaver C., Peng W., Fade margins for soft and hard handoffs, J.C. Baltzer AG, Science Publishers,vol.227,1996. S.N o (If )R10 BSVi IF)BSd IF)BSVo IF)Timer IF )speed F HD (Then Handoff Decision 1 Med Med - - High low High high Hard handoff 2 Med - Med - High low high high Hard handoff 3 Med - - Med High low high high Hard handoff 4 Med Med - - High high Low Low Soft handoff 5 Med - Med - High High Low Low Soft handoff 6 Med - - Med High High Low low Soft handoff Table 1.1 Rules Evaluation 9