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A Scheme to achieve load balancing for multihop WLAN between multiple Access Points Huazhi Gong and

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ETX only consider loss rates on the links and not their bandwidths. ETX is fit for relatively stable scenario, not for highly dynamic topology ... – PowerPoint PPT presentation

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Title: A Scheme to achieve load balancing for multihop WLAN between multiple Access Points Huazhi Gong and


1
A Scheme to achieve load balancing for multi-hop
WLAN between multiple Access PointsHuazhi Gong
and JongWon Kim
Huazhi, GongNetworked Media LabDepartment of
Information and Communicationhankgong_at_gist.ac.kr
2005/10/20
Gwangju Institute of Science and Technology,
Gwangju, Korea (www.gist.ac.kr)
2
Introduction
Wired Line
WLAN
Multi-hop WLAN
AP1
AP2
AP
  • WLAN
  • One hop
  • Infrastructure mode
  • Multi-hop WLAN
  • Proposed by S. Lee in Infocom 2004
  • Extend the coverage of AP

3
Relative Research
AP
M2WLAN
M-C over S-NIC routing for Ad hoc
MultiNet
4
Problem of Current Routing Metric for MANET
  • Most of the routing protocol based on hop count
  • Without consideration of channel condition
  • Sometimes, more hop count path perform better
    than less hop count path

5
ETX (Expected transmission count)
  • Shortest path routing not suitable
  • Multi rate issue
  • ETX
  • P 1 - (1 - pf) (1 pr)
  • p probability that the packet transmission is
    not successful
  • ETX 1 / (1-p)
  • Good in homogeneous single-radio environments
    than shortest path routing
  • Disadvantages
  • ETX only consider loss rates on the links and not
    their bandwidths.
  • ETX is fit for relatively stable scenario, not
    for highly dynamic topology

6
The way to use multi-channel in multi-hop WLAN
AP1
AP2
CH1
CH2
  • Assign channel to nodes
  • Node need to switch channel per packet
  • Deafness problem
  • Need buffer at switching node
  • Assign channel to flow
  • Easier to control

7
Load balancing (APs load calculation)
AP1
  • Assumption
  • Most of the load is downlink (from AP to MN)
  • Different AP running in different channel
  • AP is the root of the tree
  • MN is the leaf of the tree
  • Load of AP is the sum of MNs bandwidth
    multiplied with hop count from AP

8
Load of AP calculation
Load of routing path
Weighted load of AP
9
Load Balancing-How to?
AP1
AP2
  • If one node of the AP1s tree and its leaf can
    reduce the whole load of AP2, it moves to AP2.
    And switch its channel to AP2s channel.

10
Routing procedure
  • Proactive
  • Hop count number is small
  • Use the AODV-style beacon messages
  • Decide the path according to
  • 1. Weighted load of AP to find a light load AP
  • 2. Load of routing path to decide a path
  • Route maintenance

11
Simulation result
  • Choosing distributed path make
  • Faster time to reach the load balancing between
    different stream
  • Total throughput for distributed is higher, while
    for single new stream is lower

12
Simulation result (cont.)
  • Another simulation scenario
  • Kind of grid topology
  • Some area with channel loss

13
Simulation result (cont.)
14
Reference
  • 1 I. Akyildiz, X. Wang and W. Wang, "Wireless
    mesh networks A survey," Computer Networks, Dec.
    2004.
  • 2 R. Chandra, Pa. Baul, and Pr. Bahl,
    "MultiNet Connecting to multiple IEEE 802.11
    networks using a single wireless card," in
    Proceedings of IEEE INFORCOM 2004, vol. 2, pp.
    882-893, Mar. 2004.
  • 3 J. Chen, S.-H. G. Chan, J. He and S. Liew,
    "Mixed-Mode WLAN The integration of ad hoc mode
    with wireless LAN infrastructure," in Proceedings
    of IEEE GLOBECOM 2003, vol. 1, pp. 231-235, Dec.
    2003.
  • 4 S. Lee, S. Banerjee and B. Bhattacharjee,
    "The case for a multi-hop wireless local area
    network," in Proceedings of IEEE INFOCOM 2004,
    vol. 2, pp. 894-905, Mar. 2004.
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