Dynamic Load Balancing and Channel Allocation in Indoor WLAN

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Dynamic Load Balancing and Channel Allocation in
Indoor WLAN
Mohamad Haidar Committee Dr. Hussain
Al-Rizzo Dr. Robert Akl Dr. Haydar
Al-Shukri Dr. Yupo Chan Dr. Hassan
Elsalloukh Dr. Seshadri Mohan
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Proposal Outline

• Background
• Problem Statement
• Review of Literature
• Research Objectives
• Project Plan
• Conclusion
• References
• Questions

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Background

• What is WLAN?
• Flexible data communications system
• Consists of one or more wireless devices
• WLAN uses IEEE 802.11 standard
• Two types of WLAN
• Ad-Hoc Two or more PCs equipped with wireless
  adapter cards, NO connection to a wired network.
• Client/Server Multiple wireless devices linked
  to a central hub (AP) which act as a bridge to
  the network resources.

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Background(continued)

• Family of WLAN
• 802.11 1-2 Mbps in the 2.4 GHz band (FHSS or
  DSSS)
• 802.11a Extension to 802.11 provides up to 54
  Mbps in the 5 GHz band (OFDM)
• 802.11b (Wi-Fi) extension of 802.11 provides 11
  Mbps with a fall back to 5.5, 2, and 1 Mbps in
  the 2.4 GHz. (DSSS)
• 802.11g offers transmission of 20-54 Mbps over
  relatively short distances in the 2.4 GHz.(OFDM)
• 802.11n build on MIMO offers high throughput of
  100-200 Mbps

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Problem Statement

• Dynamically balance traffic load on APs and
  minimize channel interferences by assigning
  optimal channels (non-overlapping) to the APs on
  an indoor WLAN.
• Interferences

Co-channel
Adjacent
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Literature Review

• Cellular networks review
• ILP optimization was used on selecting optimal
  position of BSs in a cellular network 1.
• Divide and conquer is another optimization
  technique was used to position BSs 2.
• Dynamic load balancing (channels) was applied in
  cellular networks to reduce call blocking
  probability 3.
• WLAN review
• Static
• AP placement and channel assignment was proposed
  in 4 and 5 using an optimal ILP.
• Provides best set of AP locations for load
  balancing
• Constant BW is provided by a channel at an AP
  regardless of the number of users

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Literature Review (continued)

• WLAN review
• Dynamic
• Dynamic load balancing was ONLY considered by
  8. But did NOT provide reconfiguration of
  channels.
• Only proposed an approach to minimize traffic
  disruption caused by association or dissociation
  of new nodes to and from their respective APs.
• Other related work
• Moving objects, such as people affect the
  performance of the system by introducing large
  variations in the received signal strength 9.

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Literature Review (continued)

• Other Related work
• Without proper consideration of cell locations
  and cell sizes, deployment of high-density WLANS
  might carry significant risk of poor performance.

WHY?
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Research Objectives

• Optimize AP selection and traffic allocation
• Formulate AP placement according to initial
  traffic
• Optimize dynamic channel allocation
• Formulate a dynamic optimal channel assignment by
  min. interference between adjacent and co-channel
  APs.

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Research Objectives (continued)

• Interference by adjacent and co-channel cells
  should be minimized.
• A node is considered to be covered by an AP if
  power received from its corresponding AP exceeds
  a certain threshold value.
• User distribution traffic load will be treated as
  a statistical Poisson distribution (varying
  traffic with time).
• Propagation mechanisms will be taken into
  consideration
• For optimal performance of the whole network, a
  centralized decision-making algorithm will be
  implemented.

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Research Objective (continued)

• Formulation
• Objective
• Minimize congestion at bottleneck APs
• maxC1, C2, , CM, (1)
• Where i is the number of APs, j is the number of
  candidate APs and Ci is the congestion factor at
  AP i.
• The objective function is subject to the
  following constraints
• (2)
• Where xij is a binary variable takes the value of
  1 when demand cluster i is assigned to AP j and 0
  otherwise.
• for j1,,M (3)
• Where Bj is the maximum bandwidth of AP j, Ti is
  the average traffic load at demand cluster i.
• Dynamic feature will add the time constraint on
  these equations!

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Project Plan

• Phase I
• Has been started and in progress
• Some simulations have been conducted using
  available software packages
• Optimization and Network flow class with Dr. Yupo
  Chan
• Realistic indoor environments will aid in
  formulating optimization problem

Indoor floor plan using different wall materials,
door way and Tx.
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Project Plan (continued)

• Phase II
• Formulating the optimization problem
• Apply the formulated problem to realistic
  environments
• Phase III
• Dynamic optimization feature will be added.
• Mobility model will be presented in terms of
  Poisson distribution
• Several simulations will be carried out under
  different scenarios and constraints.
• Results will be presented and compared to models
  reported in 4 and 5.

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Conclusion

• It is expected that the proposed dynamic traffic
  load-balancing scheme will lead to an effective
  utilization of the channel and an improvement in
  capacity and coverage area of WLAN.
• Unlike other schemes this dynamic feature will
  strive to give the optimal performance as time
  progresses.

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References

1. C. Glaber, S. Reith, and H. Vollmer. The
   Complexity of Base Station positioning in
   Cellular Networks. Workshop on Approximation and
   Randomized Algorithm in Communications Networks,
   March 2000.
2. E. Yammaz and O. K. Tonguz. Dynamic Load
   Balancing Performance in Cellular Networks with
   Multiple Traffic Types. IEEE Vehicular
   Technology Conference, pages 3491-3495, September
   2004
3. S. Gordon and A. Dadej. Design of High Capacity
   Wireless LANs based on 802.11b Technology. 6th
   International Symposium on Communications
   Interworking, pages 133-144, October 13-16, 2002.
4. R. Akl and S. Park. Optimal Access Point
   selection and Traffic Allocation in IEEE 802.11
   Networks, Proceedings of 9th World
   Multiconference on Systemics, Cybernetics and
   Informatics (WMSCI 2005) Communication and
   Network Systems, Technologies and Applications,
   paper no. S464ID, July 2005
5. Y. Lee, K. Kim, and Y. Choi. Optimization of AP
   placement and channel assignment in wireless
   LANs. LCN 2002. 27th Annual IEEE Conference on
   Local Computer Networks, pages 831-836, November
   2002.
6. M. Klepal, R. Mathur, A. McGibney, and D. Pesch.
   Influence of People Shadowing on Optimal
   Deployment of WLAN Access Points. IEEE Vehicular
   Technology Conference, pages 4516-4520, 2004.
7. S. Gordon and A. Dadej. Design of High Capacity
   Wireless LANs based on 802.11b Technology. 6th
   International Symposium on Communications
   Interworking, pages 133-144, October 13-16, 2002.

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Questions?