Ad Hoc Mobility Management with Uniform Quorum Systems

UQSUQSDistributed mobility-management schemeFor ad hocSize of quorum intersection is a design parameter that can be tuned to adapt to the traffic and mobility patterns of the network nodesTradeoff system reliability and cost of location update (more intersectionmore quorum sizethen increase traffic of location update)One possible solution partitioning of the network

Conventional HLRConventional scheme HLR fixed association (node-HLR)For specific nodeit has specific HLRUQSdynamic association (node-HLR)

Virtual backboneLocation databases which form a virtual backboneRouting does not necessarily go through the databasesThe node location provided by the databases can provide vital information to the routing protocolDefine the location of a mobile host as the ID number of its nearest location database

Virtual backboneNeed to maintain connectivityDue to backbone nodes are few compared with the whole networkthe extra overhead causes by routing is less

node-DB associationNodes containing the location databases can dynamically detach and reattach to the network at any time due to mobiles movements or changes in the communication environment

node-DB associationFailwhenever the node containing the database detaches from the network for a long timeFixed association between nodes and databases (node-DB association)

node-DB associationAvoid fail problemmultiple HLRs (but still has fixed association problem)Solutionvirtual HLR or adaptive HLR (Randomly choose a node as a new HLRand the database name of this HLR is still the same)

Dynamics of UQSUQS dynamic association (node-HLR) between any particular quorum to any mobile hostMay choose the quorum contains the nearest databaseand this kind of quorum may be several ones and randomly choose one of them as HLR

Dynamics of UQSDifference with multiple HLRIf all multiple HLRs of the node are failthen fail to the nodeAs long as at least one complete quorum is survivalthen the system is not failEach quorum may (can) be the HLR of the node

Dynamics of UQSBecause the intersection property of quorumUQS is dynamic (no fixed association between any particular quorum to any mobile host) (node-HLR)

Others of quorumQuorum is more flexible than adaptive HLRfor examplefixed node-HLR associationothers need to know your HLRQuorum has high reliabilitybecause at least one quorum survivesOther advantagelocation and service provider independent numberingload balancing

Others of quorumBIB (Balanced Incomplete Block) design problem is the same as UQS constructionCostcost to accessing databasescall loss due to database failureBut large intersection size require larger size of quorums, which increase the cost of location updates and location queries

Fail & InaccessibleWhen a backbone node detached from the networka nearby non-backbone node is recruited to take its place in the virtual backboneWhen detach exceeds the threshold (time) then replacementBut the original database in the node is lostwe call this database failInaccessibledetach doesnt not exceed the threshold

Fail & InaccessibleNeed a mechanism to check accessibility of nodesand the frequency of checking is much higher than that of location update and query (and because the number of virtual nodes is fewthe cost is low)Number of intersections will affect backup and reliabilityFail and inaccessible should be solved

Update locationSituation of update location(1) When using the quorum (read)update the quorum(2) change of quorum (due to change of location or other reasons)(3) periodic

Call lossCall loss(1)database fail (may have erroneous information)(2)database inaccessible (low probabilitydue to the time of inaccessible is low)The probability of call loss depends on the stability of networkthe frequency of update (but more overhead)

Construction of UQSFive parameters for UQS constructionNnumber of databaseQnumber of quorumKsize of quorumMinumber of quorum contain database iRnumber of intersectionRepresented by a N*Q matrixentry will be 0 or 1On purpose of uniformeach (database or quorum) RKM is the same

Construction of UQSSome properties of UQSParameter is dependentFor a given set of parametersits UQS may not existUQS is the same as BIBso solution to BIB is solution to UQS

Construction of UQSDue to no sufficient condition of BIBthere is no way to decide whether UQS exists or notAnd there is no formula can represent the relation among N KRso it can only be studied some UQS parameter sets under certain situation

Construction of UQSFive series(skip now)Given Nshow the allowable variation of r in Fig3 (the five series)But the five series cant contain all situationsIn factthe choice of N will be affected by routing and loadEven given Rthe relation of N-K is not one-to-one

Construction of UQS

Mobilitydatabase failuretrafficreliabilityreliabilityneed to know the requested nodes HLR (UQS)multipleadaptiveMultiple (node-DB association) adaptive (non node-DB association)

Virtual backbonereadwrite (queryupdate)virtual backbonerouting protocoldatabase(?)Uniform?cost of call loss(?)quorum size1()quorum sizeOthers?Adaptive HLR(1) (2)handover()(handoverbackup)How to backup? How to restore?FailmobilityInaccessible (1)Inaccessible time is short (2)complete quorumInaccessiblecomplete quoruminaccessibledetectFailcomplete quorumdata lostupdate intersection backup-restore

updatequorumdatabasesquorumsizeoverheadquorum sizequorum sizeintersection sizecall lossupdatequorum sizetradeofffailupdate ratequorum sizefailintersectiondatabasesupdate ratecall rateupdate ratequorum constructioncall ratetrafficburst trafficintersection sizeupdate ratetrafficintersection size