Minimal cost deployment of mesh
networks with QoS requirements
for indoor environment
Xiaohua Jia
Dept of Computer Science
City University of Hong Kong
2016/5/29
City Univ of Hong Kong
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Mesh Network Architecture

Multihop
WLAN (single hop)
Internet

Gateway connection
MANET (no gateway)
Portal
MP MPP
MP
AP MAP
MP
MP
AP MAP
MP
AP MAP
Client
Client
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Client
2
Mesh Network Planning
Problem
Problem: Given a set of users,
each with QoS requirements
(bandwidth and delay), find
the optimal placement of AP,
MP, and gateway nodes in the
area such that the users QoS
requirements are met and the
total cost of the AP, MP, and
gateway nodes is minimized.
Output: 1) locations of nodes;
2) transmission power of nodes;
3) number of radios per AP.
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Internet
Portal
MP
MP
MP
AP
MP
AP
Client
City Univ of Hong Kong
Client
Client
3
Related Work
AP Placement in WLAN
[BCC07] S. Bosio, A. Capone, and M. Cesana, “Radio Planning of Wireless Local Area
Networks,” IEEE/ACM Trans on Networking, vol. 15, no. 6, pp.1414 –1427, Dec 2007.
1) Min-set cover: place Min # of APs in CSs, such each client is covered by at least one AP;
2) Min overlap problem (MoP) / Max efficiency (total throughput) plan (MeP): given N of
APs (or budget), place them such MoP or MeP is optimized.
[EGS07] A. Eisenblatter, H-F Geerdes and I Siomina, “Integrated Access Point Placement and
Channel Assignment for Wireless LANs in an Indoor Office Environment”, IEEE Symp.
on World of Wireless, Mobile and Multimedia Networks (WoWMoM), 2007.
1) Max avg throughput of all users for placing N APs. Each user’s throughput is f(dv,AP) under
fixed power of APs;
2) Min overlap APs (in terms of number of clients) using the same channel;
3) LP formulation and computed by using CPLEX.
No multi-radio and rate adaption & power control.
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Related Work (cont’d)
AP&MP Placement in Mesh Networks
[SL06] A. So and B. Liang, “Optimal Placement of Relay Infrastructure in Heterogeneous
Wireless Mesh Networks by Bender’s Decomposition,” QShine’06.
1) place min # of relays in N users positions (served & connected);
2) Mathematical Programming formulation.
[WXC07] J. Wang, B. Xie, K. Cai, and D. Agrawal,
“Efficient Mesh Router Placement in Wireless
Mesh Networks”, IEEE MASS’07.
1) place min # MR among N candidate sites,
cover service area and interconnect relay nodes.
2) two steps: a) coverage; b) connectivity
No interference was considered.
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Related Work (cont’d)
QoS Gateway Placement
[B04] Y. Bejerano, “Efficient Integration of Multihop Wireless and Wired Networks with QoS
Constraints”, IEEE/ACM Trans on Networking, Vol. 12, No. 6, Dec 2004.
1) Transformed to: clustering of graph into min number of clusters; 2) QoS: cluster size and radius;
3) TDMA for intra-cluster and use of orthogonal channels for neighbor clusters.
[ABI06] B. Aoun, R. Boutaba, Y. Iraqi, and G. Kenward, “Gateway placement optimization in
wireless mesh networks with QoS constraints,” IEEE Journal on Selected Areas in
Communications, vol. 24, no. 11, pp. 2127 – 2136, Nov. 2006.
1) Graph partitioning based on k-hop Dominating-Set
No consideration of interference
for link capacity / throughput
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Unique challenges



Placement of different types of mesh nodes
(AP, MP and gateway) and aiming at
minimizing the total cost.
APs can be equipped with different number of
access radios.
Each node (AP or MP) can adjust its
transmission power and data rate is adaptive
to transmission power.
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Decomposition of the problem
Subproblem 1: Optimal placement of APs to
serve all clients.
Subproblem 2: Configure minimal number
of Gateway nodes for a large cluster
under QoS constraint.
Subproblem 3: Merge small clusters by
adding minimal number of MPs
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AP Placement with multiradios and power control
Problem: given a set of clients in an area, each client has
bandwidth requirement γ. Place a set of APs W,
determine number of radios for each node, and adjust
power to meet γ, and the total cost is minimized:
cos t (W )  pB | W |  pR  |  ( w) |
wW
RI
u
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AP placement in indoor
environment



Divide the region into
grids;
Traffic demands
(Clients) originate
from grids;
APs are placed at
the center of grids.
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Transmission power, data rate
and interference




AM×M: signal attenuation array
Node v can receive data from w if:
A(w,v)Pw ≥ α
Node v can be interfered by w if:
A(w,v)Pw ≥ β
Data rate from v to w is (similarly for R(w,v)):
R(v,w) = f(A(v,w)Pv)
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A table of transmission range,
data rate and interference range
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Interference model
RI
Node interference
I(w) = {v| A(w,v)Pw ≥ β}
u
Link interference
link l’ is interfered by l if one of
the end-node of l’ is in the
interference range of l.
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u
v
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Interference and Bandwidth
Constraint
Network G(V, E): V set of clients and APs. A link l in E
is between a client and an AP.
I(l): Interference set of link l is a set of links that either
interfere with l or are interfered by l, including l itself.
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Bandwidth constraint under
interference


 vup ,  vdn: up link and down link traffics of v
Channel bandwidth is shared by all links in the
collision set I(l). That is:
TI (l ) 
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
( v , w )I ( l )
(

up
v
R(v, w)


dn
v
R( w, v)
City Univ of Hong Kong
) 1
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A performance metric for
greedy algorithms

S(w): clients served by AP w
Max collision load:

Client to Interference Ratio CIR(w):

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Top-down method
Initialization. Each client is placed with an AP.
Choose two neighboring APs to merge to a new AP w,
such that:
1)
2)
AP w can serve all clients of two old APs (w’s power is set to
cover all clients), and meet the bandwidth constraint;
CIR(w) is maximal (locate w’s new location);
Determine the number of radios w and do channel
assignment.
a)
b)
c)
3)
Repeat step (2) until no more merge can be done (i.e.,
CIR(w) cannot be increased by merging any two APs).
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Merging with neighboring APs


The merge of APs should be between
neighboring APs
We use Delaunay graph of APs to ensure the
merge between neighboring APs
B
C
A
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Number of Radios of an AP
and Channel Assignment
Input: G(V, E), V: a set of APs and clients
Output: k(w) and channels for radios in w, w in W
 Initialization: |k(w)| = 1 for all w;
 Sort all links l = (v, w) in descending order by |I(l)|;
 For each link l = (v, w), assign the least used channel among
links in I(l) to it. If the bandwidth constraint cannot be met (i.e.,
TI(l) > 1) and |k(w)| doesn’t exceed the upper bound,
 Add a new radio to w;
 Assign a channel to the new radio in w;
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Bottom-up method
1)
2)
3)
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Initially all clients are not served.
Place an AP at a grid and adjust it power such that
the bandwidth constraint is met and:
CIR(w) is the maximal.
Repeat the above step until all clients are served.
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Simulation results

100m×100m region divided into 20×20 grids

pR: pB (price of radio / box) = 0.4 : 1 and γup : γdn = 1 : 9
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Simulation results (Cont’d)
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On-going research problems…



QoS AP placement and topology control by using
physical interference model (SINR model).
Capacity analysis of using multiple access radios
against use of single radio. What is the performance
gain compared with the cost?
k-coverage (k = 2) AP placement. Given per client’s
bandwidth requirement γ1 if served by its primary AP,
and γ2 if its primary AP failed, place minimal
number of APs (and adjust power) such that each
client is covered by at least k APs and γ1 and γ2 are
met for fault tolerance.
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Thanks!
Q&A
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