KAIS T On the problem of placing Mobility Anchor Points in Wireless Mesh Networks Lei Wu & Bjorn Lanfeldt, Wireless Mesh Community Networks Workshop, 2006 므리나 September 18, 2007

2 CS 712 Outline Introduction Problem description Related work Analysis of the problem in mathematical mode Identification of the most important factors Proposed approach Simulation validation Future work & conclusion

Introduction Wireless mesh networks (WMN) Multi-hop wireless networks Consist of wireless routers and mesh clients Mobility of mesh clients in WMN Low mobility as compared to mobile ad-hoc networks WMN Vs current fixed mobile networks Unplanned topology Wireless connection between mesh routers Two geographically neighboring nodes can be very far from each other 3 CS 712

A Quick Overview Mobile IP MN moves from a network coverage cell to another cell Gets a CoA from the visited network Registers the association between the CoA and the HA by sending a binding message Hierarchical Mobile IP Localized mobility management style to red uce the signaling overhead Manages local and global mobility separately To deal with local movement management MAP is introduced Entity that deals with the MIP handoffs Local and global binding updates 4 CS 712

Problem Description Mobility management techniques for seamless connectivity Mobile IP – MIP Inefficient in the cases of frequent migrations Hierarchical mobility model schemes- Hierarchical mobile IP (HMIP) Provides faster handover for frequent migrations Use of mobile anchor points (MAP) to group access points into different subnets 5 CS 712 *Traditional Hierarchical Networks Topology is structured like a tree Placement of MAPs are predetermined to be at the root nodes Wired and stable links

Problem Description Hard to use hierarchical mobility management schemes in WMN 6 CS 712 Where to place the MAPs ? 6 and 13  6 hops away 13 and 5  4 hops away Might be good for MAP But.... High delay due to 5 neighbors MAPs placement is a challenging problem in WMN

Related Work Not much research regarding the placement of MAPs Fairly easy problem – place at the root node Two different MAP placements of MAPs [13] Difference in handover delay Research on other issues similar to the MAP placement problem Placing different servers at different locations for better performances [14][15] Focus is on maximizing the network capacity In WMN, focus  minimize the latency Centrality type of problem [16][17][18] Based on central indices, the centrals of the networks can be determined First used in social network analysis Ex- co-citation networks  most important and famous scientists 7 CS 712

Mathematical Modeling (1/4) Mathematical definition of anchor point placement WMN as a simple undirected graph G= (V,E) Edge delay  Shortest path from source to destination  Problem of selecting a set of nodes from V and a set of sub-graphs from G so that each acts as a root of to give minimum possible average delay 8 CS 712 Selection in 2 parts *Formation of sub-graphs *Selection of the root nodes

Mathematical Modeling (2/4) Mathematical Approach Handover delay calculation broken down into four parts Movement detection delay Router advertisement delay Address configuration delay Binding update delay Local binding update delay Global binding update delay Total Handover Delay 9 CS 712 Local delays - not affected by the placement of MAPs Assumed to be constant 

Mathematical Modeling (3/4) Case 1 : only one MAP in the graph Case 2 : If each AR is a MAP Case 3 : Selecting g MAPs from graph topology 10 CS 712 Analysis Major part of the formula depends upon the average round trip time (RTT) Can be as small as 50% for the MAP in the centre of a graph rather than at the edge (a) shows the registration delay and the transmission delay between MN and AR (b) depends upon the transmissi- on delay between AR and MAP (c) is affected by the transmission delay between any MAP and any HA Avg. delay using 6MAPs is 12.2 and using MIP is 15 -> 18% reduction Good selection of MAP can greatly reduce the delay

Mathematical Modeling (4/4) Most important factors for the placement of MAPs 11 CS 712 Some Facts a good MAP selection can reduce the delay upto 50% in a simple graph HMIP with well selected MAP can reduce the handover delay as compared to MIP Local handover possibility m is the most important factor

Proposed Idea Approach Steps: Gather user mobility information Based on this information, group mesh nodes into subnets Size of the subnet > the max. one hop degree and < than max.two hop degree Estimate the average local movement possibility m and record the number of subnets g Calculate the combine closeness centrality value Select the node with largest combined closeness centrality in each subnet as the MAP Forming benchmark for the provided solution- Select the MAPs randomly Once the subnet is determined, a mesh node can be randomly selected as the MAP Has only possibilities to find the best combination of MAPS 12 CS 712

Simulation Validation Simulation Parameters OMNeT ++ with INET framework Comparisons with random selection approach Randomly positioned 15 mesh nodes Possibility of a node to move to a different subnet is 30% 13 CS 712

Future Work & Conclusion Future Work Distributed scheme to dynamically orm subnets Not always possible to group meseh nodes together based on the mobility pattern Dynamic MAP registration scheme Traffic thru MAPs High delay when the # of visiting nodes becomes high Conclusion MAP problem  forming a tree structure in a random unplanned graph to minimize the handover delay Hierarchical tree structures are easy to organize Chose the important nodes as root nodes Transform the graph into a hierarchical tree structure 14 CS 712

QUESTIONS?? 15 CS 712