In this undertaking I will specify handover Hells. I will explicate basic intent of handover anticipations. I will briefly depict handover anticipations in heterogenous webs. I will discourse how handover can keep the seamless transmittal in radio webs. I will besides discourse the chief jobs with handover in heterogenous webs.
In radio web every Mobile node or nomadic device is connected to its Base Station ( BS ) or Access Point. Every base station is has its ain coverage country or scope called Cell. When nomadic node or nomadic device moves from one base station to another the signal strength of its original base station becomes weak. So when nomadic node enters to another base station its control is transferred to new base station. This procedure is called handover.
The nomadic radio webs should be able to supply a full mobility ( nomadic node can travel easy ) to users with a good Quality of Service ( QoS ) . Quality of Service is portion of mobility of users. When nomadic node moves the base station to which it is connected has to be updated. During the motion of nomadic node the Mobile Station ( MS ) scans its neighbour ‘s base Stationss and proctors communicating parametric quantities for illustration Signal Strength ( SS ) or package holds of all available base Stationss. When some of signal parametric quantities of the base station to which the Mobile Station is connected beads below the certain degree the Mobile Station performs a handover. So Mobile Station interruption all connexions from old base station and set up a new connexion to the new base station called mark base station. During this procedure the QoS may diminish but it should be least.
Handover anticipation or anticipation of handover is a procedure in which mark base station is predicted. Handover anticipation helps to cognize mark base station in progress. So it enables to execute a fast handover and it minimizes the intervention. [ 3 ]
Introduction to heterogenous web:
A heterogenous web is a web that consist different runing systems and protocols to link nomadic nodes or computing machine with other nomadic nodes or devices. The heterogenous web has a scope of different entree webs so user or subscriber can entree the cyberspace. Heterogeneous web is a aggregation of assorted radio techniques including WLAN, GSM, UMTS, orbiter webs and BLUETOOTH etc. In 3rd coevals ( 3G ) the WLAN provides a low mobility and low communicating cost over a geographically little country and with higher information rates to mobile nodes. UMTS cellular webs provide a broad coverage country with a low bandwidth and high communicating cost to Mobile node with high mobility. So integrating of these webs has formed a heterogenous web that provides service at any where or any clip mobility connectivity and the chief benefit is really low cost to those Mobile nodes who want a high velocity wireless entree. [ 4 ]
Available at: hypertext transfer protocol: //www.comp.nus.edu.sg/~chenbinb/heterogeneous/index.htm
Handover anticipations for heterogenous webs
radio engineerings for illustration 2G, 3G, WLAN, WMAN etc has been developed in combination with the development of Mobile Terminals ( MTs ) with multiple web interfaces and the IP-based applications has allowed the user to hold entree to IP services anyplace at anytime from any web. Fourth coevals ( 4G ) a heterogenous radio web has brought up a great alteration in wireless communicating. Heterogeneous webs offer a better quality of services, high velocity and low cost as compared to 2G and 3G. In heterogenous webs handover direction has a critical function in order to execute a successful handover.
Handover Management in heterogenous webs:
In handover direction different maps are performed such as prosodies, mobility scenarios, algorithms and processs. Mobility scenarios are by and large divided as horizontal and perpendicular handover. In homogenous webs, horizontal handovers are take topographic point when functioning base station can non carry through user ‘s demand or signal strength becomes weak. Handover direction is a critical constituent of radio communicating because it maintains the connexion active during the traveling motion of nomadic node or device.
Handover direction Procedure:
Handover direction procedure has three stages.
It is used to roll up all the information which is required for handover and can originate it. It is besides called handover induction stage or system find.
It determines when and how to execute the handover by choosing the most suited entree web and it gives instructions to the executing stage. It is besides known as web or system choice.
It connects the nomadic node with new base station and frontward informations to the old base station.
The handover Procedure:
The handover process can be categorized into many types. Some common types are given below.
The handover is difficult when the nomadic node is connected to merely one base station at a clip.
The handover is soft when the nomadic node is connected to two or more basal station for a piece.
For seamless communicating the handover has to be seamless. In fast handover the handover latency should be minimal. In smooth handover there should be a minimal package loss.
Handover determination mechanism:
The handover determination is based on some sort of mathematical computations and information about when and where to execute a handover.
Network Controlled Handover ( NCHO )
The handover which is controlled by web is called Network Controlled.
Client Controlled Hanover ( CCHO ) .
The handover which is controlled by client or user is called Client Controlled.
Handover determination standards:
Handover standards are the qualities that are considered to give and indicant of whether or non a handover is needed.
Link quality ( Received Signal Strength )
Carrier to Interventions Ratio ( CIR ) .
Signal to Interventions Ratio ( SIR ) .
Bit Error Rate ( BER ) .
Monetary cost and security degree.
Quality of service
Handover direction solution:
For handover direction there is a 1 most popular solution is Mobile IP. It is an IP bed mobility direction protocol. This protocol manages the airting packages sent by a Correspondent Node ( CN ) to the Mobile node to its recent location. Its introduce mobility agents such Home Agent and Foreign Agent. The Mobile IP works as follows:
Agent find: Mobile node detects whether it has moved to a new web by directing or having messages from or to mobility agents.
Registration: Mobile node gets a new impermanent reference that is called Care of Address when it enters a new entree web. Mobile node registries this new CoA with its Home Agent. Home Agent sets up a new tunnel up to the terminal point of the new CoA and removes the tunnel to the old CoA.
Routing and tunneling: When the new tunnel is set up the Home Agent tunnels packages destined to the Mobile node utilizing the Mobile node ‘s new CoA.
Vertical handover determination schemes:
There are so many schemes that are used in perpendicular handover some of them given below.
Decision map based schemes.
Fuzzy logic and nervous webs based schemes.
Multiple attribute determination schemes.
User centric schemes.
Context cognizant schemes. [ 5 ]
Vertical handover in heterogenous webs:
Heterogeneous radio webs are the combination of different engineerings for illustration 2G, 3G, UMTS, Satellite webs and WiFI etc. In heterogenous webs handover could be horizontal within same web but most of clip it would be perpendicular because heterogenous web is a aggregation of several different webs.
Vertical handover can be categorized as web controlled and client controlled.
Before heterogenous webs, web controlled handover was usually used so Base station maintains up to day of the month context information for the nomadic node. It besides make up one’s mind where and when should execute a handover.
Network controlled handover is non really sufficient in heterogenous webs because in heterogenous webs nomadic node is connected with many base Stationss and with besides different service suppliers.
Client controlled handover could be more efficient in heterogenous web environment. In client controlled the nomadic node can pull off the handover determinations. In client controlled Mobile node is straight connected with web so nomadic node will make up one’s mind where and when a perpendicular handover should execute.
In heterogenous webs it is really of import to analyse and choose best web channel to set up a connexion. It is really helpful to minimise package loss and latency due to handover mechanisms.
For illustration and nomadic node is cognizant that it may free WLAN coverage in following minute it will avoid download a picture watercourse. So it will take the best following available web. In other illustration a user may pick up the coverage of a WLAN for a piece when he walks near a hot spot but nomadic node would non execute a handover if it is cognizant it would free connexion in following few proceedingss. [ 6 ]
Problems and challenges with handover in heterogenous webs:
In a heterogenous web handover determination is a really of import stage. In handover determination decides whether it should execute a handover or non? And it besides decides which could be the most suited mark web. Horizontal handover takes topographic point within the same web when Signal Strength of the functioning Base Station ( BS ) goes down below a certain threshold value and perpendicular handover takes topographic point between different webs.
In heterogenous web environment, users can travel between different webs. They will acquire advantage from different web features such coverage, bandwidth, latency, power ingestion and cost etc. The handover procedure is more complex in heterogenous webs. So there are more ambitious jobs in handover determination and deciding it. It besides affects handover public presentation. In perpendicular handover determination the determination standard is different than horizontal handover.
To choose most suited entree web.
To avoid unneeded handovers.
Correct handover anticipations.
To supply best Quality of Service.
Must satisfy web and user demands by make up one’s minding over which entree web to link when many entree webs are available for a specific service.
Uniting determination standards.
Seamless informations transmittal
User satisfaction job
A context cognizant job
Incorrect handover anticipations.
Slow velocity [ 5 ]
In this undertaking I have described the handover. I have analyzed the basic handover operation. I defined heterogenous webs and handover in heterogenous webs. Handover is a procedure that switches the control from one base station to another during the motion of nomadic node. There are several possible grounds that cause a handover for illustration signal strength of functioning base station and user ‘s demands. In heterogenous webs there are besides two types of handovers, horizontal and perpendicular. But in heterogenous webs most of handovers are perpendicular because heterogenous web is a combination of different webs. Vertical handovers are complicated in heterogenous webs because it is hard to find the most suited mark web among several entree webs.