Vertical Handover Between Wifi Wimax Information Technology Essay

Abstraction: Many advanced informations services are driving up radio engineering, which is further boosted by growing in advanced market sections. Supplying end-to-end communicating in heterogenous internetworking environments is a challenge. Handover hold is one of the debatable issues that users are face in the heterogenous webs. However, in the instance of both WiMAX and WiFi engineerings located at the same base station ( BS ) ; the perpendicular handover ( VHO ) hold will be less compared with two conventional WiMAX/WiFi heterogonous webs with two different wireless Internet service suppliers ( WISP ) . In this paper, In order to cut down the hold in protocol transition, a new proposed design for WiWi ( WiMAX and WiFi ) version bed is studied. The realisation of the internetworking between these two criterions is discussed and evaluated. This paper focuses on constructs of WI-MAX engineering, which employs microwave for the transportation of informations wirelessly and focuses on heterogenous seamless handover between WiFi and WiMAX.

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Data service refers to a telecommunications service that transmits high-speed informations instead than voice. Internet entree is the most common information service, which may be provided by the telephone and overseas telegram companies every bit good as cellular bearers. Text messaging is a cellular information service. The radio industry is germinating from a web of independent webs into a individual incorporate web with multiple criterions. Wireless engineering describes telecommunications in which electromagnetic moving ridges, carry the signal over portion or the full communicating way without overseas telegrams. Wireless broadband refers to repair wireless connectivity that can be utilized by endeavors, concerns, families and telecommuters who travel from one fixed location to another fixed location. Wireless broadband is an extension of the point-to-point, wireless-LAN bridging construct to present high-speed and high capacity pipe that can be used for voice, multi-media and Internet entree services. Though there are many engineerings available for supplying broadband wireless entree to the Internet such as Blue tooth, WiFi and WiMAX, but here the chief focal point is on WiMAX and WiFi/WiMAX seamless handover.

II. WiFi

WiFi stands for wireless fidelity and by and large refer to any type of 802.11 webs, whether 802.11b, 802.11a, 802.11g. WiFi is a wireless engineering that uses wireless frequence to convey informations through the air. WLAN entree point or hub or sender sends out a wireless signal that allows Wireless devices to entree within a circle of approximately 100 metres. Zone around the sender is known as hot topographic point. Computers connected to WiFi receiving systems near a hot topographic point can link to Internet at high velocities without overseas telegram. WiFi refers to three types of radio protocols that can work with each other: IEEE 802.11b ( “ Wireless B ” ) , IEEE 802.11a ( “ Wireless A ” ) , and the newer IEEE 802.11g ( “ Wireless G ” ) . They can link computing machines really fastly: 11 Mbps for Wireless B, 54Mbps for Wireless A, and 54 Mbps for Wireless G, which are described in subsequent subdivisions.


* It is the longest, well-supported, stable, and cost effectual criterion, runs in the 2.4 GHz scope that makes it prone to interference from other devices ( microwave ovens, cordless phones, etc ) and besides has security disadvantages

* Limits to the figure of entree points to three.

* It has 11 channels, with 3 non-overlapping, and supports rates from 1 to 11 Mbps.


* It is an extension of 802.11b, with the same disadvantages ( Security and intervention )

* It has a shorter scope than 802.11b.

* It is backwards compatible with 802.11b so it allows a

* It runs at 54 Mbps.

802. 11a

* It is wholly different from 11b and 11g.

* It is flexible because multiple channels can be combined for faster throughput and more entree points can be collocated.

* It runs in the 5 GHz scope, so holding less intervention from other devices.

* It has 12 channels, 8 non-overlapping, and supports rates from 6 to 54 Mbps.

A. WiFi edifice block

Block diagram shows function of the IEEE 802.11 demands into a functional WiFi edifice block. The WiFi edifice blocks are:

a ) Antenna B ) Access Point ( AP )

degree Celsius ) Router vitamin D ) Internet entree

Figure 1. Wi-Fi Block Diagram


WiMAX ( Worldwide Interoperability for Microwave Access ) is a telecommunications protocol that provides fixed and to the full nomadic Internet entree. The current WiMAX alteration provides up to 100A Mbit/s with the IEEE 802.16m update expected to offer up to 1 Gbit/s fixed velocities. The name “ WiMAX ” was created by the WiMAX Forum, which was formed in June 2001 to advance conformance and interoperability of the criterion. The forum describes WiMAX as “ a standards-based engineering enabling the bringing of last mile radio broadband entree as an option to overseas telegram and DSL ” .

Figure 2: WiMAX delivers 72 Mbps over 30 stat mis point to indicate and 4 stat mis NLOS.

WiMAX engineering frequently misinterpreted by the people by the names of nomadic WiMAX, 802.16d, fixed WiMAX and 802.16e. Actually 802.16-2004 or 802.16d is developed by the 3rd party as a criterion and it is besides referred to called as Fixed WiMAX because this criterion is missing behind merely because of the non-mobility characteristic that ‘s why it ‘s frequently called as Fixed WiMAX. During the adulthood period of WiMAX engineering some of the amendments were made to the above mentioned 802.16d and they referred this amending criterion as 802.16e. 802.16e introduced mobility and some other characteristics amongst other criterions and is besides known as Mobile WiMAX. WiMAX provide velocity of 72 Mbps over 30 stat mis point to indicate web and 4 stat mis point to multipoint non line of sight web. Figure2 illustrates these exciting capablenesss.

A. WiMax architectureA

The WiMAX Forum has proposed an architecture that defines how a WiMAX web can be connected with an IP based nucleus web, which is typically chosen by operators that serve as Internet Service Providers ( ISP ) ; Nevertheless the WiMAX BS supply seamless integrating capablenesss with other types of architectures as with package switched Mobile Networks.

Figure 3: WiMAX architecture

The WiMAX forum proposal defines a figure of constituents, plus some of the interconnectednesss ( or cite points ) between these, labeled R1 to R5:

SS/MS: the Subscriber Station/Mobile Station

ASN: the Access Service Network

Bachelor of science: Base station, portion of the ASN

ASN-GW: the ASN Gateway, portion of the ASN

CSN: the Connectivity Service Network

Hour angle: Home Agent, portion of the CSN

Abdominal aortic aneurysm: Authentication, Authorization and Accounting Server, portion of the CSN

Sleep: a Network Access Supplier

NSP: a Network Service Provider.

It is of import to observe that the functional architecture can be designed into assorted hardware constellations instead than fixed constellations. For illustration, the architecture is flexible plenty to let remote/mobile Stationss of changing graduated table and functionality and Base Stations of changing size – e.g. femto, pico, and mini BS every bit good as macros.


Table.1 Wireless Technology Comparison

WiFi ( a )

WiFi ( B )

WiFi ( g )







Frequency ( GHz )




2 – 66

Speed ( Mbps )












Low Cost


Speed, Range




Cost, Range



Handovers are an of import portion of a web engineering. When traveling between different BSs, the connexion besides has to travel. Seamlessness in this study is defined as follows: the current session, QoS must be maintained during and after handover. In other words, a seamless handover is a handover that is seamless to the user. Obviously this besides depends on the sort of service the user is necessitating. With real-time applications like videoconferencing or streaming media, the user will likely detect a lessening of them connexion. On the other manus, while shoping a web site or reassigning a file, the user does non hold to detect anything of the handover procedure. The latency and package loss are the two important factors for seamless handover. These two factors have to be every bit little as possible to do the handover seamless. Before discoursing several handover issues, the following portion will travel into item about handovers in general foremost. There can be several grounds why and when a handover should be initiated:

aˆ? MS current place and speed

High speed can ensue in different handover determinations.

aˆ? Link quality

Another BS can present a higher quality nexus ( e.g. higher velocity, stronger signal, better QoS ) .

aˆ? Load at a BS

When a BS in a subnet is presently overloaded ; the web can make up one’s mind to relocate some MSs.

aˆ? Conserving battery power

In order to salvage battery power, a MS can take to exchange to a closer station to be more energy efficient.


Together, WiMAX and WiFi are ideal spouses for service suppliers to present convenient, low-cost nomadic broadband Internet services in more topographic points. Both are unfastened IEEE radio criterions built from the land up for Internet Protocol ( IP ) – based applications and services. IEEE 802.11 has accelerated the web deployment for supplying high transmittal rate in limited geographical coverage, while IEEE 802.16 offers more flexibleness in while keeping the engineering ‘s information rate and transmittal scope. The limited coverage scope of WiFi makes it hard to run into the hereafter omnipresent webs need while IEEE 802.16 can supply high velocity Internet entree in broad country. A natural tendency is the combination of IEEE 802.16 and IEEE 802.11 to make a complete radio solution for presenting high velocity Internet entree to concerns, places and hot spots.

Fig. 4. The interaction of WiWi protocol Stack with the WiMAX BS and WiFi device.

However, both techniques have their ain sets of advantages and disadvantages. On the one manus, WiFi may offer a high information rate ( up to 500Mb/s is envisaged ) , but it is power limited due to the usage of unaccredited set and are hence much more confined in coverage, while on the other manus, even though WiMAX is data rate limited ( up to 70Mb/s fixed ) , it can supply extended coverage much like the cellular systems. Because of that it is informative to use both engineerings in the laptop/mobile for omnipresent connexion with high informations rates. In this study we introduce a new combination of WiMAX and WiFi ( called WiWi ) . The WiWi faculty comprised of WiMAX and WiFi OSI located at the nomadic WiMAX will work as a relay nodes ( a.k.a mobile relay node ) .

Figure 4 shows the protocol stack of the proposed WiWi faculty. The range of WiWi faculty is to increase the laptop scope when the user moves out of the WiFi coverage by fall ining WiMAX web utilizing WiWi faculty installed in the WiMAX Mobile, see Figure 5. The range of this paper is to discuses the handover determination for the WiFi device to either articulation WiFi or WiMAX web.


From Figure 5 we can see that there are two possible scenarios ; ( a ) the Laptop within WiWi and WiFi webs coverage and ( B ) the Laptop out of WiFi web coverage. Scenario ( B ) is straightforward in which the laptop will see merely one web connexion, that provided by WiWi faculty.

Fig. 5.WiMAX and WiFi coverage in indoor and outdoor ( a ) the laptop in the WiFi coverage ( B ) laptop is out of WiFi coverage.

Directly the device will get down web entry procedure to fall in WiMAX web utilizing WiWi faculty installed at the WiMAX Mobile. There are two manners for WiWi operation: unfastened entree manner, which the user opens the entree for everybody to entree his WiMAX Mobile ( WiWi faculty ) , while in the close manner the user allows merely his WiFi device to entree his WiMAX Mobile to acquire the Internet entree.

On the other manus, in scenario Figure 5 ( a ) there are two webs available WiMAX ( utilizing WiWi faculty ) and WiFi web, the device should choose merely one of them to entree the Internet based on the standard signal strength index ( RSSI ) message received from the AP/BS. In this scenario utilizing the conventional handover for web choice based on RSSI message is debatable. This is because WiFi device will feel two WiFi signals coming from WiWi Module and WiFi entree point ( AP ) .


Figure 6 shows the handover determination based on RSSI and throughput. The entire throughput for WiWi web is calculated based on WiMAX throughput and the consequence of perpendicular handover within the WiWi faculty. This is done as follows:

Fig. 6. Network choice strategy in the WiFi to WiMAX handoff scenario

where is the debasement of throughput due to multihop relay. is the WiMAX capacity and N is the figure of hops ( i.e. in WiWi, n=2 ) . is the entire throughput loss due to protocol convertor and intervention between WiFi and WiMAX.

Fig. 7. Signing procedure in the WiFi to WiMAX handover scenario

Figure 7 shows the flow of the messages for linking WiFi devices the WiWi web. Here we assume the WiWi in the closed manner so that there are no other nodes sharing the channel with the WiFi device. The throughput depends on the WiMAX channel bandwidth ( i.e. 1.25-20MHz ) and entire figure of tones ( 256 for fixed and 1024 for Mobile ) and channel quality.

IX. Decision

This paper focused on one of the intelligent informations services Bluetooth, WiFi and WiMax and besides issues of wireless air engineerings ; seamless handover. As radio engineerings are emerging, the demand for changeless connectivity is turning. This can non be done without the possibility to roll between different webs and different air engineerings. The procedure which facilitates this is called a handover. Seamless handover is the sort of handover the user does non detect, and therefore the preferable 1. Unfortunately, it is non ever that easy to back up seamless handover. There is a period of clip in which a user can non have or direct any informations because it has to exchange between entree points or even alter its IP-address. This period of clip is called handover latency and is one of the most important factors in the success of a handover protocol. Furthermore, there are more issues to see when reexamining handover solutions: package loss, complexness and inefficient usage of resources can do serious jobs. As the most promising new wireless entree engineering, the research foremost focused on WiMAX. In this paper a new perpendicular handover algorithm for WiWi web is studied. The perpendicular handover is performed at the logical version bed above the MAC bed.