load balance based access point association in wireless mesh networks ma tianze computer network and...
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![Page 1: Load Balance Based Access Point Association in Wireless Mesh Networks Ma Tianze Computer Network and Protocol Testing Laboratory, Dept. of Computer Science](https://reader034.vdocuments.us/reader034/viewer/2022051515/55148f06550346ea6e8b50c2/html5/thumbnails/1.jpg)
Load Balance Based Access Point Association
in Wireless Mesh Networks
Ma Tianze
Computer Network and Protocol Testing Laboratory,
Dept. of Computer Science & Technology, Tsinghua Univ.
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Monday, April 10, 2023
Outline
Problem challenge
Related works
AP association algorithm
Indirect users balancing extension
Experiment
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Monday, April 10, 2023
Problem challenge
WMN Characteristics
– Wireless Mesh Network is a multi-hop wireless network
– The data sent by a user will be transferred among the multi-hop path of the backbone to the mesh-router which has a back hole to the internet
– A new AP association mechanism is needed because conventional association method using signal strength as the only metric may be not quite suitable for WMN
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Monday, April 10, 2023
WMN Characteristics
Internet
Mesh Router with Back Hole Mesh Router with Back Hole
Mesh Router Mesh Router
y
y
y
y
y
y
y
Mesh Routerwith AP
Mesh Routerwith AP
Which AP should the user be associated with?The left AP: Stronger signal, but heavy load and far from back holeThe right AP: Weaker signal, but light load and near to back hole
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Monday, April 10, 2023
Problem challenge
Factors Considered in AP Association
– Signal strength: users would like to select an AP with good signal quality
– Quantity of AP’s users: If an AP serves too many users, the channel access delay of each user will be too large because of channel access competition.
– Multi-hop characteristic of WMN: Delay and congestion of the data path between AP and back holes
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Monday, April 10, 2023
Related works
Dynamic Cross-Layer Association in 802.11-based Mesh Networks
– George Athanasiou, Thanasis Korakis, Ozgur Ercetin, Leandros Tassiulas
– IEEE INFOCOM 2007
– Defines an Airtime cost and make it the AP selection metric instead of 802.11 RSSRI
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Monday, April 10, 2023
Related works
Joint Optimal Access Point Selection and Channel Assignment in Wireless Networks
– Koutsopoulos.I, Tassiulas.L
– Networking, IEEE/ACM Transactions
– Proposed a SCLB algorithm to assign users who stays in the overlap area of APs
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Monday, April 10, 2023
AP association algorithm
Some Definitions
– A set of APs
– A set of users
– association coefficient
– The coefficient increases when the AP is appropriate for the user, which embodies the preference of users in AP association
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1 2{ , ,..., }NU u u u
( , )i j ij ijw u a P e
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Monday, April 10, 2023
AP association algorithm
Network Model
– Each AP has an coverage
– The coverage of two or more APs is divided into several overlap areas
– The algorithm has several passes
– During a pass, all the overlap areas are traveled in turn
45
3
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AP1 AP2
AP3
AP4
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Monday, April 10, 2023
AP association algorithm
Algorithm Steps
– 1. All the overlap areas are traveled in turn
– 2. When it goes to a overlap area For each AP who forms this area, work out how many
users should be assigned to it Using a best-bipartite-matching algorithm to satisfy
above assignment and make the summation of association coefficient maximum
– 3. After all the areas have been traveled, if the association of users an APs is the same with last pass, the algorithm halts. Else go to step 1
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Monday, April 10, 2023
AP association algorithm
work out how many users should be assigned to each AP
Purpose: After the assignment, the number of users of each AP can be balanced to the best of our abilities
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Monday, April 10, 2023
AP association algorithm
Using a best-bipartite-matching algorithm to satisfy above assignment
– We have already worked out how many users should be assigned to each AP in a overlap area
– The question is which user should be assigned to which AP
Purpose: make the summation of association coefficient maximum
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Monday, April 10, 2023
AP association algorithm
best-bipartite-matching
– Nodes in left side are users
– Nodes in right side are APs split by number of users to be assigned to it in the area
– Weight of edges is association coefficientIf a best-bipartite-matching is found, the
summation of association coefficient maximum
u1
u2
u4
u3
a1
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w11
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Monday, April 10, 2023
Indirect users balancing extension
Indirect Users
– An AP in WMN not only has direct users connected to it, but also has indirect users which would take it as a relay node of data transfer
– Indirect users can also be seen as load of AP
– If indirect users load of APs are not balanced, congestion may occurred on the data path
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Monday, April 10, 2023
Indirect users balancing extension
As an extension to the above algorithm
– we define a load degree which summarizes the direct and indirect users to scale the load of APs
– The balancing of direct users will be replaced by the balancing of load degree.
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Experiment
Tools
– C++ codes to implement the algorithmPerformance Metrics
– The overall throughput
– End-to-end delay
– Fairness of usersCompared with
– Pure IEEE 802.11
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Monday, April 10, 2023
Thank you!