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Design and Performance Study for a Mobility Management Mechanism (WMM) Using Location Cache for Wireless Mesh Networks

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... Using Location Cache for Wireless Mesh Networks. Di ... (or Mesh Nodes, MNs) provide wireless network access service to ... User data is relayed hop by hop ... – PowerPoint PPT presentation

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Title: Design and Performance Study for a Mobility Management Mechanism (WMM) Using Location Cache for Wireless Mesh Networks


1
Design and Performance Study for a Mobility
Management Mechanism (WMM) Using Location Cache
for Wireless Mesh Networks
  • Di-Wei Huang, Phone Lin, Senior Member, IEEE, and
    Chai-Hien Gan, Member, IEEE
  • Presented By Mahmoud ElGammal

2
Wireless Mesh Networks Architecture
  • Wireless Mesh Networks (WMNs) have emerged as one
    of the major technologies for 4G high speed
    mobile networks.
  • WMN Components
  • A mesh backhaul connects the WMN with the
    internet.
  • Stationary Mesh access points (MAPs) (or Mesh
    Nodes, MNs) provide wireless network access
    service to mobile stations (MSs).

3
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4
Mobility Management is Required!
  • Proposed solution WMN Mobility Management
    Mechanism (WMM)
  • The WMM adopts the location cache approach.
  • MS location information is cached while routing
    the data for the MS.
  • The goal is to minimize signaling and routing
    costs.

5
Existing Mobile Management Protocol Categories
  • 1. The ad hoc routing protocol
  • Adopted by mobile ad hoc networks (MANETs).
  • A routing path from the source to the destination
    is established.
  • User data is relayed hop by hop by MSs.
  • Unlike MANETs, WMNs have a fixed infrastructure.
  • Ad hoc routing schemes are not efficient for WMNs.

6
Existing Mobile Management Protocol Categories
  • 2. The centralized-database MM protocol
  • A centralized database is maintained to store MS
    location information.
  • Usually adopted in cellular networks.
  • Whenever an MS moves from one LA to another, the
    database is accessed to update the MS location
    information.
  • When the size of an LA is small, high signaling
    cost is expected.
  • Due to the diversity of WMNs (varying from
    several kilometers to at most hundreds meters),
    it may not be so efficient to directly apply the
    centralized database scheme for the MM protocol
    in WMNs.

7
Existing Mobile Management Protocol Categories
  • 3. The mobile IP protocol
  • The service area of an IP network is partitioned
    into a home network and foreign networks.
  • Two network entities, home agent (HA) in the home
    network and foreign agent (FA) in the foreign
    network, are responsible to tunnel user data to
    MSs.
  • Introduces signaling overhead to inform the HA of
    the MSs movement.
  • Tunneling lengthens the routing path (the
    triangle routing problem).

8
WMN Mobility Management
  • Association
  • Delivering Data
  • Location Management / Handoff Management

9
WMM Association
  • When an MS enters the coverage are of a MAP, it
    performs the association procedure to establish a
    wireless access link to the MAP.
  • This MAP is known as the Serving MAP (SMAP) of
    the MS.
  • The wireless link between the MS and the MAP can
    be a direct link or a relay link via other MSs.

10
WMM Delivering Data
  • Before delivering the user data to an MS, the
    SMAP of this MS must be identified.
  • The user data is then sent to this SMAP through
    one or more MNs via the wireless mesh links.
  • These MNs are known as the relaying MAPs (RMAPs).
  • Since an MS may change the SMAP from time to
    time, MM is required for packet delivery to the
    moving MSs.
  • Existing standards (such as IEEE 802.11 and IEEE
    802.16) for WMNs do not address the MM issue.

11
WMM Location Management / Handoff Management
  • Location Management When an MS changes its SMAP,
    location management updates the SMAP information
    for the MS.
  • Handoff Management During data transmission, if
    the MS changes from old SMAP to new SMAP, handoff
    management enables the old SMAP to forward user
    data to the new SMAP.

12
The WMM Mechanism
  • MNs are assigned fixed IPs.
  • MSs are assigned IPs manually or via DHCP, and
    are not required to change their IP addresses.
  • An MN maintains two cache tables
  • The routing table maintains the routing paths
    between the MN and other MNs.
  • The proxy table maintains the MS location
    information.
  • The MS location information is carried in the
    packet headers.

13
The WMM Mechanism
  • When MNs route packets for an MS, the location
    information of the MS in proxy tables in the MNs
    are updated.
  • MNs can correctly route the packets for MSs by
    referencing the proxy table and routing table.
  • If the mesh backhaul does not cache MS location
    information when processing packet routing, a
    query procedure is executed to obtain the MS
    location information.

14
The WMM Mechanism
  • The options field in the IP header is utilized to
    store the MS location information.
  • The options field is filled or modified by MNs
    when they route the packets for an MS.
  • The options field is divided into four subfields
  • The ISS field (to store the IP address of the
    senders SMAP)
  • The SST field (to store the senders serving time
    stamp)
  • The IRS field (to store the IP address of the
    receivers SMAP)
  • The RST field (to store the receivers serving
    time stamp)

15
WMM Procedures
  1. Registration To register an MS to its SMAP.
  2. Routing executed by MNs to route the packets for
    an MS.
  3. Query executed by the mesh backhaul to obtain
    the IP address of the receiver's SMAP when it's
    unknown.

16
WMM The Registration Procedure
  • Suppose that MS1 moves from its SMAP MAP1 to
    another MAP, MAP2
  • Step 1 MS1 sends a registration request message,
    REREQ(MS1s IP Address, Previous SMAPs IP
    Address, Selected SMAPs IP Address) to MAP2.
  • Step 2a Upon receipt of REREQ at t1, MAP2
    updates/creates MS1's entry in the proxy cache
    (Im MS1s IP Address, Is MAP2s IP Address,
    Ts t1).
  • Step 2b MAP2 sends an update request message,
    UREQ(MS1s IP Address, Selected SMAPs IP
    Address, t1), to MAP1.
  • Step 2c Upon receipt of UREQ, MAP1 updates the
    entry for MS1 in its proxy table (Im MS1s IP
    Address, Is MAP2s IP Address, Ts to t1).
  • Step 3a MAP1 responds to MAP2 by an update
    response message, URSP.
  • Step 3b MAP2 sends a registration response
    message, RERSP, to MS1, indicating the completion
    of the registration request.

17
WMM The Registration Procedure
  • MS1s location information is kept in the proxy
    tables of both MAP1 and MAP2.
  • The location management for MS1 is done at MAP1
    and MAP2.
  • MNs with obsolete MS1s location information
    (that is, Is field for MS1 stores MAP1s IP
    address), the packets are first routed to MAP1,
    and then MAP1 retrieves its proxy table to
    forward the packets to MAP2.
  • This mechanism is loop free.

18
WMM The Routing Procedure
  • Consists of two parts Location Information
    Synchronization, and Packet Routing.
  • 1. Location Information Synchronization
  • the MS location information in the proxy table of
    the MN and that carried in the IP header of the
    packets are updated to the latest MS location
    information.
  • Suppose that MS1 (sender) is sending IP packets
    to MS2 (receiver), where MAP3 is one of the MNs
    along the routing path

19
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20
WMM The Routing Procedure
  • 2. Packet Routing

21
WMM The Query Procedure
  • Step 1 The mesh backhaul broadcasts a route
    request message, RREQ(MS2s IP Address), to all
    MAPs, then expects to receive a route response
    message, RRES, before a timer Tq expires.
  • Step 2 Upon receipt of the RREQ message, MS2s
    SMAP replies by a route response message, RRES(IP
    Address of MS2s SMAP, MS2s Serving time stamp),
    to the mesh backhaul.
  • Step 3 If the RRES message is received before Tq
    expires, the mesh backhaul updates MS2s location
    information carried in the IP header and that in
    the proxy table. After the query procedure, MAP3
    can route the packet. Otherwise (that is, Tq
    expires), the mesh backhaul discards the packet.
  • The query procedure requires flooding signaling
    messages to all MNs in the WMN, which is a
    high-cost operation.

22
WMM Analytical Model
  • WMN traffic is classified into Internet and
    intranet sessions.
  • Suppose that MS0 enters the WMN at time t0.
  • Let x be the time period between t0 and the time
    when MS0 initiates the first Internet session.
  • Suppose that when MS0 enters the WMN, there are
    another N identical MSs.
  • Each MS initiates intranet sessions towards MS0
    with probability ?.
  • Let N' (0 lt N' lt N) be the number of MSs (that
    initiate intranet sessions toward MS0). Without
    loss of generality, we assume that the N' MSs are
    MS1, MS2, ..., MSN.
  • Let yk be the time period between t0 and the time
    when MSk (1 lt k lt N') initiates the first
    intranet session toward MS0.

23
WMM Analytical Model
  • MS0 initiates the first Internet session at to
    x, where the mesh backhaul creates an entry to
    store MS0s location information. After to x,
    if there are packets to be routed to MS0, these
    packets can be correctly routed to MS0 without
    invoking the query procedure.
  • At least one MSi (1 lt i lt N') initiates the
    first intranet session towards MS0 at t0 yi
    before MS0 initiates the first Internet session
    at t0 x. At t0 yi, if any of the MNs along
    the routing path between MSis SMAP, and the mesh
    backhaul stores MS0s location information, then
    the query procedure is not invoked during the
    packet transmission for the intranet session from
    MSi to MS0.

24
WMM Analytical Model
  • A probability that case (a) occurs.
  • B probability that case (b) occurs.
  • The analysis of B is too complicated, so we will
    calculate an upper bound for Pq.
  • x follows a Poisson distribution with rate ?.
  • yi follows a Poisson distribution with rate ?.

25
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26
WMM Analytical Model
With yk being exponentially distributed with mean
1/?
27
WMM Experiments
  • The WMN is modeled as a regular hexagonal
    topology.
  • Each hexagon represents the coverage area of a
    MAP.
  • The WMN consists of 61 MNs (1 mesh backhaul and
    60 MAPs) and 1,000 MSs (N 1,000).
  • The mesh backhaul is located at the center of the
    WMN.
  • The movement of an MS follows a 2D random walk
    model, where an MS resides in a MAPs coverage
    area for a period of time and then moves to one
    of its neighboring MAPs with the a probability of
    1/6.

28
WMM Experiments
29
WMM Comparisons
  • Cu Location Update cost (the average number of
    MNs and MSs that exchange signaling messages for
    location update operation -- executed when an MS
    changes its SMAP.)
  • Ct Location Tracking cost (the average number of
    MNs and MSs that exchange signaling messages for
    location tracking operation -- executed when a
    session is initiated toward an MS.)
  • Cr Routing cost (the average number of MNs or
    MSs that route a packet to a destination MS.)
  • M The number of MNs in the WMN.
  • N The number of MSs in the WMN.
  • R The average number of MNs in the routing path
    between two MSs or between an MS and a
    centralized node (for example, a centralized
    database or an HA.)
  • r The average number of sessions initiated
    toward an MS in the WMN.
  • ns The average number of sessions between any
    two MSs, MS0 and MS1, within a time period where
    MS0 and MS1 do not change their SMAP.

30
WMM Comparisons
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