QoS-aware routing in emerging heterogeneous wireless networks

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QoS-aware routing in emerging heterogeneous
wireless networks

• Communications Magazine, IEEEVolume 45,  Issue
  2,  Feb. 2007 Page(s)74 - 80 Digital Object
  Identifier 10.1109/MCOM.2007.313398
• ?????

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Outline

• ??Introduction
• ??Physical characteristics of an HWN system
• and its implication on QoS-aware
  routing
• ??Policy-based methodology for QoS routing
• in HWNs
• ??Main components for QoS-aware routing in
• HWNs
• ??A QoS-aware routing algorithm for HWNs
• ??Evaluation results

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??Introduction

• Recent years have seen a significant increase in
  research and development of mobile and wireless
  networks.
• The integration of different kinds of wireless
  mobile networks, or heterogeneous wireless
  networks (HWNs), is also emerging.
• QoS routing mechanisms, either for unicast or
  multicast, are proposed for wireless networks.
• However, there is not a great deal of
  availability with regard to QoS routing for HWNs.

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• While inheriting most of the features of MANETs,
  HWNs also present their unique challenges for QoS
  routing mainly due to its heterogeneity.
• This article presents an analysis of the basic
  architecture of an emerging heterogeneous
  wireless network and its new requirements for
  QoS-aware routing.

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??Physical characteristics of an HWN system
and its implication on QoS-aware
routing

• Two air interfaces are utilized for the
  communication between nodes the C interface that
  operates at a cellular network frequency, and the
  A interface that operates at an ad hoc network
  frequency.
• A base station uses its C-interface to
  communicate with mobile handsets in a wireless
  mode.

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• The communication between base stations can be in
  wired mode or using microwave, and controlled by
  a Central Control (CC) System.
• Traffic Diversion Station (TDS) is introduced to
  divert the traffic in hotspot areas. In a TDS, a
  C-interface is used for communicating with a BS
  or a MH (mobile handset) with a C-interface
  whereas A-interface is equipped for communicating
  between TDSs or with MHs with an A-interface.

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• A request from a MH (like MH3) is blocked due to
  the limited bandwidth of the home BS (like BS1),
  a TDS (e.g., TDS2) near the MH can divert this
  request to another BS (like BS2) through a
  relaying route (such as MH3-TDS2-TDS1-BS2).

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• QoS routing in HWNs has its unique issues. In
  HWNs, a call or data can be finally diverted to
  any suitable destination if the latter has free
  bandwidth to accommodate the request.
• As such a destination selection procedure is a
  necessity in HWNs. Destination selection is a
  procedure to select a suitable BS that is able to
  accommodate the diverted traffic.

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• In special cases, if a MH (e.g., MH1) which is
  making a call during busy time is uncovered by
  any TDS, a pseudo source (e.g., MH2) is selected
  by the home BS to release its occupied bandwidth
  to the original source (namely, MH1), and the
  ongoing call from the pseudo source is diverted
  to another BS through a relaying route (like
  MH2-TDS2-TDS1-BS2).

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??Policy-based methodology for QoS routing
in HWNs

• To provide QoS in an HWN, many issues related to
  the heterogeneity and mobility need to be
  addressed.
• This article proposes to use the Policy-Based
  Management (PBM) method to assist the QoS routing
  process aiming to give the flexibility of
  defining different constraints.
• In this article a policy is employed to define a
  choice in the decision making of the QoS routing
  process.

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• The policy-based system architecture for
  supporting dynamic QoS routing is a collection of
  the following four types of entities
• Policies
• A policy decision engine that reasons over these
  policies to make QoS management or routing
  decision
• An action execution engine that provides the real
  implementation of these actions or policies
• A series of components that implement the
  QoS-aware routing functions such as service
  differentiation, QoS parameter mapping, and so on

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• In order to make a comprehensive decision, a QoS
  routing algorithm will need to consider the
  various factors service types, user
  requirements, user device characteristics, and
  network features.
• When there is a significantly enough change in
  certain factors defined by policies, this change
  is reported to the PDP through an event, and then
  the PDP makes a proper decision by reasoning over
  the policies.

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??Main components for QoS-aware routing in
HWNs

• QoS Parameter Mapping
• QoS parameter mappings between cellular networks
  and ad hoc networks are needed, that is, C-to-A
  mapping and A-to-C mapping, or more specifically
  from IEEE 802.11e to UMTS and vice versa
  respectively.

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• Monitoring
• QoS-aware routing is dependent on the accurate
  reading of the network status.
• The network states maintained on a node called
  local state. The totality of local states for
  each node constitutes the global state of the
  network.
• In order to achieve a picture of the whole
  network state, exchange of these local states
  among nodes are needed.
• Limited broadcasting is another mechanism aiming
  to bring the communication overhead further down.

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??A QoS-aware routing algorithm for HWNs

• This article proposes a QoS-aware routing
  algorithm called QRA.
• It starts from the point where a MH initiates a
  request, but no sufficient bandwidth in its home
  base station is available to accommodate this
  request. Here the request initiating MH (also
  called source MH) is denoted as MHs.
• If there is a TDS of sufficient bandwidth within
  the transmission range of MHs, MHs uses it
  directly as the next hop for relaying data.
  Otherwise, a Source Selection Procedure (SSP) is
  triggered to find a proper MHp within the same
  cell so that MHp can release its channel to MHs.

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• In any case, an MHs data need to be transmitted
  via relay, as such a relaying route needs to be
  discovered.
• However, prior to route discovery a destination
  needs to be decided via the Destination Selection
  Procedure (DSP).
• Once a destination is selected, a Route Discovery
  Procedure (RDP) is activated to find all routes
  satisfying the destination and QoS requirements.
• If multiple routes are found, then a Route
  Selection Procedure (RSP) is applied to select
  the most proper route to relay the MHss data.

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• QOS-AWARE DESTINATION AND SOURCE SELECTION
• The destinations are decided before the route
  discovery process. The purpose is to make best
  use of the CC because the CC knows which cells
  are noncongested cells and have available
  bandwidth.
• Furthermore, as the CC can decide destinations
  for the source MH, limited broadcasting can be
  applied to the route discovery process.

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• QRREQ for QoS RREQ, is broadcast within one of
  these circles (namely the limited broadcast
  area).

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• In order to broadcast QRREQs within the
  pre-decided circle, the CC has to give a full
  list of cells in which QRREQs can be broadcast.
  This also means that when an intermediate node
  receives a QRREQ, it needs first to check whether
  it is within the cells listed in the QRREQ.
• In the evaluation of theQRA algorithm, an
  intuitive and simple criterion is adopted (i.e.,
  first come first used), namely, the BS whose
  response comes back to the requester first is
  selected as the destination.

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• The source selection algorithm implemented in QRA
  tries to select a pseudo source that satisfies
  the following criteria as much as possible
• Having more TDSs around it as a further
  possibility to find a relaying route
• The neighboring TDSs possessing more bandwidth
• The selected source being more likely to move
  outside of the current home cell as such
  automatically releasing its bandwidth

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• QOS-AWARE ROUTE DISCOVERY
• Within this QRREQ there is another parameter
  called TTL (time-to-live) which is greater than
  0.
• Intermediate nodes rebroadcast QRREQ if their
  resources can satisfy the QoS requirements in the
  QRREQ until the packet arrives at a destination
  or TTL times out.
• A destination node, upon receipt of a QRREQ,
  sends a QRREP (QoS Route Reply) packet which
  travels back to the source following the reverse
  route.

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??Evaluation results
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