2015-9-19City Univ of Hong Kong1 Minimal cost deployment of mesh networks with QoS requirements for indoor environment Xiaohua Jia Dept of Computer Science

23/4/19 City Univ of Hong Kong 1

Minimal cost deployment of mesh networks with QoS requirements

for indoor environment

Xiaohua JiaDept of Computer ScienceCity University of Hong Kong


Mesh Network Architecture Multihop

WLAN (single hop)

Gateway connection

MANET (no gateway)MPP

Internet

PortalMP

MPAP

MP

MPAP

MPAP MAPMAP

MAP

ClientClientClient


Mesh Network Planning ProblemProblem: 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.

Internet

PortalMP

MPAP

MP

MPAP

ClientClientClient


Related WorkAP 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.


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.


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


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.


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


AP Placement with multi-radios 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:

u

RI

Ww

RB wpWpWt |)(|||)(cos


AP placement in indoor environment

Divide the region into grids;

Traffic demands (Clients) originate from grids;

APs are placed at the center of grids.


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)


A table of transmission range, data rate and interference range


Interference model

Node interference

I(w) = {v| A(w,v)Pw ≥ β}

Link interferencelink l’ is interfered by l if one of

the end-node of l’ is in the interference range of l.

u

RI

u v


Interference and Bandwidth ConstraintNetwork 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.


Bandwidth constraint under interference

: up link and down link traffics of v

Channel bandwidth is shared by all links in the collision set I(l). That is:

,upv dn

v

1)),(),(

()(),(

)( vwRwvR

Tdnv

lIwv

upv

lI


A performance metric for greedy algorithms

S(w): clients served by AP w Max collision load:

Client to Interference Ratio CIR(w):


Top-down method

1) Initialization. Each client is placed with an AP.

2) Choose two neighboring APs to merge to a new AP w, such that:

a) AP w can serve all clients of two old APs (w’s power is set to cover all clients), and meet the bandwidth constraint;

b) CIR(w) is maximal (locate w’s new location);

c) Determine the number of radios w and do channel assignment.

3) Repeat step (2) until no more merge can be done (i.e., CIR(w) cannot be increased by merging any two APs).


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

A

BC

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 WInitialization: |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;



Bottom-up method

1) Initially all clients are not served.

2) Place an AP at a grid and adjust it power such that the bandwidth constraint is met and:

CIR(w) is the maximal.

3) Repeat the above step until all clients are served.


Simulation results 100m×100m region divided into 20×20 grids

pR: pB (price of radio / box) = 0.4 : 1 and γup : γdn = 1 : 9


Simulation results (Cont’d)


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.


Thanks!

Q & A

Documents

2015-9-19City Univ of Hong Kong1 Minimal cost deployment of mesh networks with QoS requirements for indoor environment Xiaohua Jia Dept of Computer Science