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Maximal covering with network survivability requirements in wireless mesh networksAdviser: Frank,Yeong-Sung LinPresent by Limin Zheng

Gunhak Lee , Alan T. Murray

Seoul National University Arizona State University

PAPERMaximal covering with network survivability requirements in wireless mesh networks

1Agenda Introduction Backgroud Problem description Mathematical formulation Application details Results & Discussion ConclusionsPAPERPAPER()(PAPER)

2IntorductionPAPER3IntroductionMany US cities and Countries are attempting to build wireless broadband networks for communication and service in their communities as basic infrastructure to facilitate local economic development and enable much wider service provision to more people.

wireless networks in municipalities have been widely utilized fora range of public applications, such as public hotspots, publicsafety and general communication

Wireless broadband networks would play an important role in improving the quality of our life, giving people the freedom and capability to communicate with the world anytime, anywhere

Advanced wireless broadband technologies, such as Wi-Fi, WiMax and cellular systems, relying on mesh or multi-hop networking.

Wireless broadband is attractive to municipalities willing to construct their own communication network given limited budgets.(5) 1. 2. 3.wi-fi wi-max 4.4IntroductionWhat is the primary concern in providing wireless broadband services ?

When local governments attempt to provide wireless broadband services to their communities, the primary concern is where to place relevant facilities and how to connect them.

What is the purpose of this paper ?

In this paper, we address location modeling approaches for integrating maximal covering and survivable network design in planning citywide wireless broadband services. More specifically, we propose a mathematical formulation of the maximal covering problem with survivability constraints based on wireless mesh network topology.

?1.2.PAPER PAPERModel

5Backgroud()6BackgroundSurvivable network design

What is survivable network ?What is disjoint path?

2.1(): : :traffic surviving

survivable network (:Router,)

Disjoint path PAPERdisjoint path, stdisjoint pathstNODEst2disjoint pathst

PAPERMODELdisjoint path12(12)7Background Wi-Fi based mesh networksWhat is mesh networks

2.2 AP serverwireless routersgateway wi-fi router

gatewaywi-fi router gatewaywi-fi router(Application Detail)

Number of node disjoint paths for any pair of nodes8Problem Description9Problem DescriptionFor the purpose of this paper, we specifically address two issues:how to locate Wi-Fi equipment to maximally cover demand given a specified number of units.how to connect Wi-Fi equipment to ensure survivable networking.

Solution:For(1)Maximal Covering Location Problem (MCLP) For(2) Number of node disjoint paths for any pair of nodes

PAPER, 1. wi-fi() 2. wi-fi()

1PAPERMCLP 2disjoint path

10Problem DescriptionRegarding the architecture of a mesh wireless network, some of nodes (gateways) must be connected to hard, land based infrastructure and thus reliable performance of network is dependent on the existence of duplicated paths between a general node and gateway node.

(DSL)gateway11Mathematical Formulationwi-fiwi-fi12Mathematical FormulationModel:Maximal Covering problem with Survivability Constraints (MCSC)

Assumed based on equipment capabilities :Maximum distance of wireless access form the Wi-Fi router.Maximum distance for wired access from the exiting backbone infrastructure.Maximum distance for interconnection between the Wi-Fi routers. MODELMaximal Covering problem with Survivability Constraints (MCSC)

MODEL

13Mathematical FormulationSomething need to predefined or given when using this model :Potentially eligible sites to provide wireless broadband services constitute a discrete set of locations.Set of points is predefined to represent aggregate population to be covered by the Wi-Fi router.A number of facilities, p, is given exogenously.a number of Wi-Fi routers, q, providing wired connection to the existing backbone infrastructure, is also specified in advance.

MODEL 1.wi-fi router 2.14Mathematical FormulationBased on the hierarchy of a wireless broadband network,parameters and sets are defined as follows:

Iset of demand nodesJset of potential sites for Wi-Fi routerMset of existing DSL central officesaipopulation at demand node Iprequired number of Wi-Fi routers to be deployedqrequired number of Wi-Fi routers for wired connections toexisting central officesKrequired number of disjoint pathsdijshortest distance from demand node i to Wi-Fi router at jdjcshortest distance from Wi-Fi router at j to DSL central office at cdjlshortest distance between Wi-Fi routers at j and l demand nodes wi-fi() 47515Mathematical FormulationNi{j J|dij R}{j J|dcj L , c M}j{l J|djl W , j l}Rcoverage standard for Wi-Fi;Lcoverage standard for DSL central officeWmaximum distance for Wi-Fi router point to pointinterconnection

NiI nodeJgateway wi-fi routerjjwi-fi router()l wi-fi router16Mathematical FormulationDecision variables are defined as follows:

NODE(S,t)jl10

NODE(s,t)()1,0

Logic path: stgateway wi-fi router, 17Mathematical Formulation

1.,(yi,yiai,()

2.routeryi(yi1)

3.wi-fi router

4.5 ,wi-fi routergateway-wi-fi router

6-8wi-fi router()18Mathematical Formulation

9. 10. disjoint path 19Mathematical Formulation

11gateway wi-fi router 12-1420Application Details21Application DetailsIt is assumed that wireless routers must be within 12,000 feet (L) from a central office.The coverage standard of a Wi-Fi router (R) is specified as 3465 feet, so 6930 feet is used for the maximum distance for Wi-Fi point to point interconnection (W)The required number of Wi-Fi routers (p) is specified to be in the range of 829.It is assumed that 20% of Wi-Fi routers satisfy the required number of wired connections to existing central offices (q).Two cases of disjoint paths, K = 1 and K = 2, are examined for survivable network design. 2WAironet 1300/22

The MCSC is applied to construct a wireless broadband network in an urban area. Specifically, the city of Dublin, Ohio is evaluated for wireless service because Dublin has an existing citywide Wi-Fi network.

Potential sites for a Wi-Fi router are represented as a discrete set of locations, 36 regularly spaced (4000 feet) grid points are considered for a Wi-Fi router (e.g., 3465 feet for Cisco Aironet 1300 series outdoor access point/bridge). 475 census block group centroids are used to represent the locations of residential areas in Dublin and the population of each block group is used to represent potential wireless broadband demand (Fig. 3).23Application DetailsThe MCSC was solved exactly using a commercial optimization solver, named CPLEX 10.0 (ILOG) on an Intel Xeon 3 GHz CPU with 3 GB memory. ArcGIS 9.1 was used to manage needed input information (Ni, W, xj) through spatial analysis functionality. Also, Visual Basic Application (VBA) with ArcObjects was used to create the necessary text file of the MCSC that is read into CPLEX. Further, GIS provides capabilities for visualizing and evaluating solutions. 24Results & Discussion25

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P>26,pk=1or230DiscussionIn this paper, we focus on system reliability for comparison between two different network configurations.

For each network configuration, there are specific source and destination nodes. Accordingly, sets are defined as follows:

31Evaluating system reliabilityReliability of a node can be defined as the probability that it functionsduring a specified time period. Given node reliability, the probability of a disjoint path for a pair of source and destination nodes can be derived by the joint probability of nodes along the disjoint path, based upon the assumption of independence.

Since there could be a number of disjoint paths between source and destination nodes, system reliability is the sum of the probabilities of all possible disjoint paths between source and destination nodes. 32Evaluating system reliabilityThe standard mathematical formulation of system reliability canbe found in Shier (1991), and stated as follows:

33Evaluating system reliabilityAverage system reliability for entire network, Raverage, is computedby averaging the reliabilities for all pairs of source and destinationnodes as follows:

where Q is the number of all pairs of source and destination nodes.

34Evaluating system reliabilityNode reliability probabilities are assumed (0.8 in our case)Kp(s)q(t)S-t pairs(Q)Disjoint pathRaverage111660710.69211440800.41For examining these two configurations in cases of a specificnode failure, we calculate reliability after simulating any singlenode failure. K=1 , average reliability = 0.5 K=2, average reliability = 0.61 35Conclusions36ConclusionsAdequately positioning wireless access points is crucial in order to extend service coverage with a given budget limit. Another significant consideration for building wireless broadband networks is the provision of reliable broadband service. However, it is difficult to cover a large area reliably because a more reliable broadband network ecessarily requires a more interconnected network topology to ensure redundancy in routing. ,,AP

,,, ,

37ConclusionsTo deal with these considerations simultaneously, we introduced the maximal covering problem with survivability requirements (MCSC). This approach extends classical facility location and network design problems by explicitly integrating covering and network survivability. For more practical use of this approach, several related technical issues, such as radio coverage planning, traffic and routing controls and channel assignment, must be taken into account. This paper, however, focuses on general methodological issues concerning maximal covering and survivable network design. Thus, this paper is expected to help decision makers and network planners understand coverage and design issues through the use of a method for obtaining solutions and presenting expected network configurations.MCSCPAPER 38ConclusionsThe application found that a wireless network can be designed to provide citywide wireless broadband services to an urban area, ensuring network survivability to a high degree. Comparatively, we also highlighted two types of tradeoffs. One tradeoff exits between coverage and the level of survivability. Another one exits between coverage and total cost. PAPER 1 2 39Thanks for your listening.40