GTU PG SCHOOL BISAG Gandhinagar

Handoff Scheme for High-speed Mobile Internet

Services

-Vrajesh ParikhWIMC 1st SEM

Issues in Mobility with High Speed Internet

● Reliable user authentication and mobility● Network security at speed● Device flexibility● Delay time in hand off

Types of Handoff

● Vertical Handoff :- Changing the technology to access internet

● Horizontal Handoff:-changing access point for connectivity

What we want during mobility?

• We want our applications not to be disturbed from mobility

• We want to continue to talk with our cell-phone when we change base-stations

• We want to continue to run telnet when we change access points in a Wireless LAN.

Problems With Hetrogenous Networks

-Problems with various protocols in heterogeneous networks:-

• MIP network layer, SCTP at transport layer, SIP in application layer.

• MIP is the best solution to sort the matter but still it suffers long handoff latency.

Changes needed for Heterogeneous Networks

rate adaptation, congestion control, mobility support, and coding, In particular, they present adaptiveness in layers 2 (link), 4 (transport), and 7(application) to satisfy the demand of heterogeneity and high speed multimedia applications in 4G wireless data networks

Fast handoff scheme in public WLAN systems

• Reduce the handoff latency caused by authentication procedures

• MH performs authentication procedures not only for the current AP but also for neighboring APs.(Problem is to select neighboring nodes and authentication).

• The simplest method is to select all of the APs adjacent to the current AP.

• And this is done based on the centralized AP configuration.

Approach 1 -Proposed Handoff Scheme

• The objective of the proposed handoff scheme is to reduce the handoff latency caused by authentication procedures at the new AP.

• MH performs authentication procedures not only for the current AP but also for neighbouring APs, when initial registration is performed. The key issue in this scheme is how to select the neighbouring APs to be authenticated in advance.

Prediction Based Proposal

• Network specific prediction scheme

– handoff prediction algorithms

– Previous mobility patterns using pervious patterns

– Most MHs in public WLAN systems are visiting or temporary hosts without any regular mobility patterns.

• Mobile-specific prediction scheme, we utilised a network-specific prediction scheme. In our prediction scheme, the handoff probability between APs is estimated using the previous handoff ratio and residence time collected and calculated by the central system.

FHR(Frequency handoff region)

• Record events in event log data base

•Calculate Hand off ratio •H(i, j) and N(i, j) denote the unit handoff ratio andthe number of handoff events from AP(i) to AP(j).Let Rk(i, j) be the residence time in the kthhandoff event from AP(i) to AP(j)

FHR(Frequency handoff region) cont…

•where Tout(k) and Tin(k) are in-time and out-time of kth handoff event.•For the FHR selection algorithm, we should draw a weighted bi-directional graph on AP placements. The weight values between APs are determined by the handoff ratio.

•the weight value is reversely proportional to the handoff ratio.In addition, if two APs are not adjacent, the weight value is infinite.

Approach 2-Creating HMSMN

Operation of HMSMN

• Network Detection

• Handoff Decision

• Handoff Initiation

• Handoff Execution

Detailed Description

• Network Detection -

– Detect multiple network technologies

– Obtain information about neighboring wireless technologies

– currently serving technology

• Handoff Decision-

-when the MN should handoff

-handoff decision metrics such as RSS, end-user preference, QoS requirement, service type, communication cost,

• Handoff Initiation-

• -Estimates the right time to start the MIP handoff operation

Detailed Description

-The measured RSS of the currently serving BS (AP) drops below a predefined threshold, the handoff trigger function gives a handoff trigger with network information.

• Handoff Execution-

• -When the MN starts the MIP handoff operation, there are two different approaches, basic and tight integration approaches, to integrate HMSMN and MIP on whether HMSMN closely cooperates with MIP or not.

HMSMN Integration with MIP

• Basic integration approach- – HMSMN to be transparent to the MIP operation

– In this case, HMSMN initiates a vertical handoff by simply switching the network access technology (via. network switching function) between multiple network interfaces.

• Tight integration approach-– In this approach, HMSMN interworks with MIP to maintain seamless

connectivity during the vertical handoff by triggering the MIP handoff operation for the new network while maintaining the connection to the previous network.

HMSMN coupled architectures

HOW the HMSMN Works?

References

1. A Client-based Vertical Handoff Approach for Seamless Mobility in Next Generation Wireless Networks.

-Yong-Sung Kim, Dong-Hee Kwon, Young-Joo Suh

• Fast handoff scheme based on mobility prediction in

public wireless LAN systems

- S. Pack and Y. Choi

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