Published on

  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide


  1. 1. Ganesh S. Deshmukh, Santosh S. Sambare / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1355-1359QoS oriented vertical handoff scheme for interworking of WLAN and WiMAX Ganesh S. Deshmukh*, Santosh S. Sambare** *(Department of Computer Engineering, Pune University, INDIA) ** (Department of Computer Engineering, Pune University, INDIA)ABSTRACT A Mobile Node (MN) continuously in each network. During handoff decision phase MNmoves in heterogeneous networks. When determines which network it should connect to.connections need to migrate between Handoff decision may depend on various parametersheterogeneous networks for performance and such as bandwidth, delay, access cost, andhigh-availability reasons, seamless vertical transmission power, current battery status of mobilehandoff is necessary first step. Everyone around node and user preferences. During handoffthe world would like to be connected seamlessly execution phase connections are transferred fromanytime anywhere through the best network. existing network to new network in seamlessWhen MN changes its point of access technology manner. This involves authentication, authorizationhandoff occurs. In this paper, a vertical handover as well as transfer of user’s context information.scheme is proposed for interworking of WLAN The main aim of this paper is to design effectiveand WiMAX to improve QoS in terms of QoS oriented VHO scheme for wireless networkthroughput. Available bandwidth and average consisting of WLAN and WiMAX The paper isend to end delay will be taken in to account for organized as follows. Section 2 presents the WLANmaking handoff decisions. Vertical handoff and WiMAX architecture. Section 3 analyzes thebetween WLAN and WiMAX occurs by different existing strategies and compares each onesatisfying QoS parameters. with others. Section 4 proposes our VHO scheme. Finally, section 5 concludes the proposed work.Keywords- MN, QoS, vertical handoff, WLAN,WiMAX. 2. WLAN AND WiMAX Wireless communication is, by any measure, the fastest growing segment of the1. INTRODUCTION communication industry. It is based on radio QoS, mobility and security are mostimportant issues to be covered by mechanism and technology. GSM (Global System for Mobilearchitecture for integrating different types of communications), GPRS (General Packet Radio Service), UMTS, WLAN and WiMAX are somewireless networks. Many new architectures or examples of different technologies, each with theirschemes have been proposed for seamless own characteristics. As already discussed, this paperintegration of various wireless networks. Thesenetworks allow mobile users to stay connected as will focus on WiMAX and WLAN. This section will contain a brief overview of WiMAX and WLAN.they move through different networks. The IEEE802.11 wireless local area network(WLAN) havebeen deployed widely and 802.11 access point can 2.1 WLANcover area of few hundred meters ,making them WLAN is a very popular wirelesssuitable for enterprise networks and public hotspot communication technology for short/mediumnetworks. Recently 802.16 standards (WiMAX) can distances nowadays, mostly because it isprovide high data rate and wide area of coverage. convenient, easy to deploy, easy to manage andIntegration of these two technologies raises several because of its low infrastructure costs. The Wireless Local Area Networkchallenges. (WLAN) is an unlicensed band of 802.11 ISM When MN changes its current point of frequency band. 802.11 is one of the recentaccess technology handoff occurs. There can be twodifferent types of handoff: horizontal handoff and communication technologies of IEEE standard. Avertical handoff. Horizontal handoff refers to typical WLAN network consists of Access Points (APs) and several wireless clients, called Stationsswitching between point of attachment or base (STAs).station that belongs to same network. Verticalhandoff refers to switching between stations that Today, the standard 802.11g, generally referred tobelong to different networks. Process of vertical as Wi-Fi, has been implemented all over the world.handoff can be divided into three steps, namely Physical layer specifies the modulation scheme usedsystem discovery, handoff decision and handoff and signaling characteristics for the transmission through the radio frequencies, whereas the MACexecution. During system discovery phase MN layer defines a way accessing the physical layer.search networks and what are the available services 1355 | P a g e
  2. 2. Ganesh S. Deshmukh, Santosh S. Sambare / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1355-13592.1.1 Architecture Lightweight WAP may be Self-healing because to As stated before, a typical WLAN network pay compensation for unsuccessful counterpart,consists of two entities: APs and STAs. APs are the controller commands the neighbouring WAP toBase Stations for a wireless network. APs regulate their power level, where as in autonomouscommunicate with STAs by radio waves. STAs are there is no concept of the visibility of its WAPwireless clients which connect to the APs in order to neighbouring and in this case to perform self healinggain access to the network, e.g. the Internet. it cannot adjust the power level. If single WAP is Lightweight and Autonomous are two busy or overloaded then in this situation wirelessdiscrete architectures used in WLAN environment. controller can relieve the wireless client toEach of the architectures has wide impact on wired neighbouring WAP. In critical applications such asLAN architecture. The selection of WLAN VoIP, self-healing and load balancing are importantarchitecture is based on the consideration of issues.building, integrated wired and Wireless network toachieve a high return on investment. Both 2.1.3 Autonomous modelarchitectures are popular but Lightweight In Autonomous Model WAP is notarchitecture has an advantage over the WLAN mandatory as shown in Figure 2. Autonomousmarket. Wireless Access Point sustains the switching and strong security as well as networking function that2.1.2 Lightweight model are indispensable to route the wireless traffic. As in Lightweight is the part of WLAN autonomous system there is no concept of thearchitecture. With most of wireless intelligence visibility of WAP so it cannot make the loadwhich residing at central controlling device, balancing.lightweight Wireless Access Point architecture have Autonomous model cannot differentiatenarrow functionality. whether nearest WAP is part of WLAN infrastructure or illegal rouge WAP. The difference between the autonomous and lightweight is negligible. The difference is only that lightweight have one extra component (WLAN controller).Fig 1: lightweight architecture model Lightweight model is simple. The devices Fig 2: Autonomous architecture modelthat provide the communication to the end user asAccess Layer are identified by lightweight. 2.2 WiMAXDistribution layer provide the inter communication The fiber optic transport services providingand the top layer (Core Layer) of Lightweight model the high bandwidth and data rates is replaced byis responsible fast and consistent data between WiMAX wireless technology all across the world.networks. WiMAX is emerging technology to fulfill the high Wireless Access Point (WAP) resides at data rate and QoS requirements of the customers,the interface of access layer and provides the also it is the cheap deployment of voice servicescommunication interface to end user. In lightweight with no need of line of sight wireless channel.architecture model, the management of operation is WiMAX signals have the property to adopteasy because it give the permission to WAP from the atmospheric conditions everywhere. WiMAXsingle device, because the lightweight WAP have electromagnetic waves also offer the support ofthe knowledge of visibility and attentiveness of the adoptive coding and different operation modes, soneighbours WAPs. They can observe and if any one voice and data services can easily be transported byof their neighbours becomes the victim of fault, it WIMAX network platform.notifies the wireless controller. 1356 | P a g e
  3. 3. Ganesh S. Deshmukh, Santosh S. Sambare / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1355-1359WiMAX is a wireless telecommunication handover decision which is based on varioustechnology based on the IEEE 802.16 standard parameters.[IEEE2]. It uses licensed spectrum to provide high The parameters which are evaluated tospeed wireless data transmissions over long make effective handoff decision are described in [3].distances in many different ways. Different authors have considered different parameters or combinations of these to make2.2.1 Architecture handoff decision. Dynamic decision module [4] The WiMAX Network Architecture defines a select best network at best time by considering staticframework consisting of several functional entities and dynamic factors. Static factors include usageand interconnections. Figure 3 shows this expense, link capacity and power consumptionframework in simplified manner, followed by a while dynamic factors include RSS (Received signaldescription of each entity. strength) and velocity of mobile node. This model  NAP: Network Access Provider A business was developed to reduce unnecessary handoffs. entity that provides WiMAX radio Dynamic decision process involves three phases: 1) infrastructure. Network discovery 2) Network analysis and 3)  NSP: Network Service Provider Just like Network selection and execution. In Network the NAP, the NSP is a business entity. It discovery (priority phase) candidates networks provides IP connectivity and WiMAX (networks whose RSS is greater than threshold and services. The level of services is legally velocity of mobile node is less than threshold value binded through contractual agreements set for that network) are chosen and priority is with one or more NAPs. assigned based on difference between RSS and its threshold value. Now process continues with second phase in which system status is collected and weight is assigned to each factor. Based on this static score is calculated. In third phase dynamic score is calculated by multiplying priority of each network with static score. Best network to handoff is selected which have highest value of dynamic score. Evaluating these many factors for making handoff decisions may incurs more handoff delay. In [5] author proposed handoff decision making algorithms which takes wifi RSS and estimated end to end TCP handover latency. Main aim of this paper is that handover must be initiated well before it is required. As wifi RSS is measured Fig 3: WiMAX network architecture every time both the interfaces are always on which  SS/MS: Subscriber Station/Mobile Station consumes more power. In both these papers author Entity which wants to make a connection to have not given mathematical model to obtain these the network. parameters.  ASN: Access Service Network In [6] only available bandwidth is taken This is the point of entry for the SS/MS into account for making handoff decision to provide into the WiMAX network. This entity must QoS. Author proposed two bandwidth estimation support a complete set of functions algorithms to estimate available bandwidth of required to connect a client to the network: WLAN and WiMAX. authorization, authentication, session In this paper QoS oriented vertical handoff management, network discovery, IP- scheme is proposed for interworking of WLAN and address allocation, QoS etc. WiMAX. Best network can be chosen at best time  CSN: Connectivity Service Network by taking handoff decision based on available The CSN is the part of the network which bandwidth and average end to end delay. provides IP connectivity services. It consists typically of routers, servers, 4. PROPOSED MODEL proxies, and gateways etc. providing To provide QoS oriented vertical handoff functions like Internet access and peer- to- between WLAN and WiMAX VHO (vertical peer services. handoff) scheme is proposed as shown in Fig. 4 Traffic measurement module measures traffic at3. LITERATURE SURVEY station i.e. throughout of network and gives input to In order to understand scope and HDM(handoff decision module).NCDM detectslimitations of various vertical handover approaches, available network and estimate values of parameterswe need to study existing approaches. Various and provide this to HDM. Based on informationapproaches have been proposed for vertical provided by NCDM and handoff policy, it decides 1357 | P a g e
  4. 4. Ganesh S. Deshmukh, Santosh S. Sambare / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1355-1359 need to launch handoff.CTM transfer all TSIFS and TDIFS are time duration of SIFS and DIFS. connections of station to new network. Tbackoff (t) Denote random back off time and c(t) is data rate at time t. Available bandwidth can be 4.1. Bandwidth Estimation calculated as : Available bandwidth is calculated as BWavailable (t )  ( (t )  u (t  , t ))c(t ) difference between total capacity and aggregated (4) utilized bandwidth. 4.1.2. Bandwidth estimation in WiMAX In IEEE802.16 bandwidth resource is allocated in the form of number of physical slots used. In IEEEVHO Manager Traffic measurement module 802.16 transmission occurs in the form of uplink sub (TMM) frame and downlink sub frame. BS determines (VHOM) bandwidth station can obtain for receiving downlink Uplink traffic measurement and uplink data.Control Number of frames during τ can be expressed as: Downlink traffic measurement Context n  T frame (5) Number of unused physical slots of this period is Handoff equal to: Network availability detection Decision n Module SUL  free (t  , t )  nSUL total   SUL used (HDM) Available bandwidth estimation i 1 (6) n S DL  free (t  , t )  nS DL total   S DL used Average end to end delay estimation Connection i 1 (7) Transition SUL used (i ) S DL used (i ) And denote utilized PSs in its Network condition detection Module uplink and downlink sub frame. Available (CTM) bandwidth based on above results can be expressed Module (NCDM) as: 1 BWDL available (t )  S DL  free (t  , t )cDL slot (t )  (8) Fig. 4 overview of vhom. 1 BWULavailable (t )  SUL free (t  , t )cUL slot (t ) 4.1.1. Bandwidth estimation in WLAN  (9) In IEEE 802.11 medium is shared in contention manner by stations [6]. It is assumed 4.1.3. End to End delay estimation estimation period τ. During this period data End-to-end delay indicates the length of time transmission can be expressed as: taken for a packet to travel from the source to the t t destination. It represents the average data delay an Tdata (t  , t )   Tdata _ NAV   Tdata _ trans application or a user experiences when transmitting t  t  (1) data. The delay is usually measured in seconds. Where Tdata_NAV denote data transmission time in When available bandwidth of target network NAV interval. NAV is network allocation vector satisfies quality of service, end to end delay with which is set when station listens RTS/CTS message respect to that network can be calculated as: from other stations. Tdata_trans is data transmission Let, time in transmission opportunity obtained by desired η=Average end to end delay, station. Then average utilization of medium can be δ=Total transmission delay of all received packets, expressed as: Ω=Number of packets received. (10) Tdata (t  , t ) u (t  , t )   (2) If Average end to end delay is less than threshold Proportion of reserved resource that can be used value then handoff to that network takes place. purely for data transmission is: data 5. CONCLUSION (t )  data   R / C / A  (3TSIFS  TDIFS  Tbackoff (t ))c(t ) / 8 When connections need to migrate between (3) heterogeneous networks for performance and high- Where µdata is mean data packet size in bytes of availability reasons, seamless vertical handoff is desired station, µR/C is sum of RTS/CTS frame size, necessary. Handoff occurs when mobile node 1358 | P a g e
  5. 5. Ganesh S. Deshmukh, Santosh S. Sambare / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1355-1359changes its point of access technology. In this papervarious vertical handover schemes between WLANand WiMAX are described. Vertical handoverdecision is based on various parameters to providealways best connected service to mobile users. In this paper the VHO scheme is proposedfor inter- working of WLAN and WiMAX toimprove QoS in terms of throughput. When mobilenode moves out of coverage area of one network,the proposed scheme provides always bestconnected service and QoS can be improved.Available bandwidth and average end to end delayare taken into account for handoff decision.REFERENCES [1] R. O’Hara and T.L.Cole, Local and metropolitan area networks specific requirements, IEEE Std 802.11-2007. [2] R.B. Marks and J.Puthenkulam, Local and metropolitan area networks-part 16: Air interface for broadband wireless access systems, IEEE Computer Society .IEEE Std 802.16-2009. [3] Mandeep Kaur Gondaral and Dr.Sanjay kadam, Requirements of vertical handoff mechanism in 4G Wireless networks, international journal of wireless and mobile networks (IJWMN) vol. 3,no.2,April 2011. [4] Pramod Goyal and S.K.Saxena,”a Dynamic decision model for vertical handoff across heterogeneous wireless networks, 677? 2008 WASET.ORG, World academy of science, engineering and technology, issue 41, pp 676-682. [5] Bushra Naeem, Able Nyampfene, Seamless vertical handover in wifi and WiMAX networks using RSS and motion detection, Pacific journal of science and technology vol 12 May 2011. [6] D Ma and M Ma, A QoS based vertical handoff scheme for interworking of WLAN and WiMAX, Proc.IEEE global telecomm. Conf,PP.2260-2265,Nov./Dec.,2009. [7] R.Prasad,C.Dovrolis,M.Murray,And K.Claffy, Bandwidth estimation metrics ,measurement techniques and tools, IEEE network vol.17,No.6,PP.27-35,Nov- Dec.2003. [8] Rajendra Kumar and Brahmjit Singh, Comparison of vertical handover mechanisms using generic QoS trigger for next generation network, International journal of next generation networks (IJNGN) Vol.2, No.3, Sept.2010. 1359 | P a g e