Throughput Enhancement in WiMax Mesh Network Using Concurrent Transmission

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Throughput Enhancement in Throughput Enhancement in WiMax Mesh Network Using WiMax Mesh Network Using

Concurrent TransmissionConcurrent Transmission

Advisor: Dr. Kai-Wei Ke

Speaker: Jaw-Woei Ma

Date:03/28/2006

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OutlineOutline

Introduction

1.WiMAX

2.Mesh NetworkSchedulingConcurrent TransmissionSimulation and AnalysisConclusionsReferences

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WiMAXWiMAX

Worldwide Interoperability for Microwave Access(全球微波存取互通性 )

A wireless broadband network connection

technique. the last mile.Cost saving.Easy to employ

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WiMAX versus WiFiWiMAX versus WiFi

WiFi Bandwidth:11Mbps (802.11b) , 54Mbps (802.11g)

Range:100m

WiMAX Bandwidth:134Mbps, 300kbps~2Mbps (末端用戶 )

Range:48kmWiMAX,WiFi和有線網路屬於”互補關係”

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Mesh NetworkMesh Network

PMP ( point to multipoint ) The downlink, from the BS to the user,operates on a PM

P basis

Mesh Traffic can be routed through other SSs and can be occu

r directly between SSs

Subscriber station share uplink to the BS on a demand basis all above

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Distributed Scheduling

Superiority of the Mesh BS, which effectively result in Centralized Scheduling

On a combination of both

Mesh Network (cont.)Mesh Network (cont.)

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Scheduling in Mesh ModeScheduling in Mesh Mode

Distributed Scheduling

No clearly defined BS

a distributed manner like an ad-hoc network

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Centralized Scheduling

BS determines slot allocation for all SSs

a centralize manner like PMP mode

traffics can be relayed by other SSs through a multi-hop route which is defferent from PMP mode

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Combination

a hybrid of both can be adopted in Mesh mode

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Two Control Message

MSH-CSCF(Mesh Centralized Scheduling Configuration)

deliver the information of channel configuration and routing tree

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MSH-CSCH

(Mesh Centralized Scheduling)

deliver the information of bandwidth request and grant and updating of routing tree

Grant/Request Flag: 0 = Grant (downlink )

1 = Request ( uplink )

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Each entry of Scheduling TreeEach entry of Scheduling Tree

NodeID

NumberOfChildren

ChildIndex (table)

Uplink/Downlink Burst Profile

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The BS generates MSH-CSCF and broadcasts it to all its neighbors

BS -> SS (MSH-CSCF)

According to the routing tree in MSH-CSCF message, all the SSs maintain a routing tree whose root is BS and children are SSs

SS -> BS ( MSH-CSCH: Request )

BS can gather bandwidth requests from all the SSs, and assign spatial resource for SSs (put in MSH-CSCH: Grant message)

rebroadcast until all the SSs receive MSH-CSCH:Grant

SchedulingScheduling

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After receiving a MSH-CSCH:Grant message, the SSs determine its actual uplink and downlink transmission time from MSH-CSCH:Grant by a common algorithm which divides the frame proportionally

Scheduling (cont.)Scheduling (cont.)

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TDMATDMA

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Concurrent TransmissionConcurrent Transmission

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solid lines : directional links in the routing tree

dashed lines : connect the neighboring nodes in one-hop

the curves : the interference by an active link

Link InterferenceLink Interference

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L(x,y) represent the link from x to y

the interfered links by L(4,6) are L(6,4), L(2,4), L(5,2), L(4,2),L(BS,2),L(BS,1),L(3,1)

i.e. when node 4 is transmitting data to node 6,The number of interfered links by L(x,y) is given by I(x,y), so I(4,6)=7

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Py(x) = I(x,y) + I(y,x) + Pz(y).

for example, P4(6) = I(4,6) + I(6,4) + P2(4).

Constructing Routing TreeConstructing Routing Tree

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network begins with only one BS

all the SSs enter the network one by one

all its neighbor nodes are eligible to be the father node of the entering SS

entering SS should select a father node with minimal interference

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Father node is

where Neighbor(x) is a set of x’s neighbor nodes.

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After SS5 entered the network

P2(4)=46,P5(4)=30

so the father node of SS4 is adjusted from SS2 to SS5

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Concurrent Transmission Algorithm Concurrent Transmission Algorithm

The order of transmission time determination in uplink is the same as transmission order of MSH-CSCH: Request

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The ideaThe idea

The transmission time should be as early as possible on condition that no collision would happen

The transmission time of an SS should not be earlier than any of its children’s

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Algorithm (Uplink)Algorithm (Uplink)

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Algorithm (Downlink)Algorithm (Downlink)

the algorithm in downlink is similar to that in uplink

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SimulationSimulation

Simulation Scenario:

Random topology is generated in an L*L square.

( L = d √(n / 2) )

n is the number of SSs d is the maximal transmission range between tw

o nodes.

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single channel network with no bit errors

all the SSs are immobile and working in half duplex

highest available rate (set to 50Mbps here)

regardless of the channel state

Every SS request 0.5Mbps

bandwidth for both uplink and downlink

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ResultResult

show the overall end-to-end throughput

with different routing trees

The number of SSs increases from

20 to 120 with a step of 10

The throughput values are the average of simulations in 500 times

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Results (Uplink)Results (Uplink)

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Results (Downlink)Results (Downlink)

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AnalysisAnalysis

Throughput:

(1). interference-based routing tree >

random routing tree

(2). adjusted interference based routing tree > non-adjusted interference-based routing tree

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Analysis (cont.)Analysis (cont.)

This concurrency algorithm performs best when using an adjusted and interference-base routing tree.

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ConclusionsConclusions

promote spatial resource reuse, which increases the overall end-to-end throughput

Simulation results indicate that different constructions of routing tree impact the performance of the concurrent

algorithm

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Future WorkFuture Work

With rapid demands of mobility wireless access we need

Consider the scenario that SSs are mobile to improve our algorithm

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ReferenceReference[1] Jian Tao, Fuqiang Liu, Zhihui Zeng, and Zhan

gxi Lin, “Throughput enhancement in WiMax mesh networks using concurrent transmission,” Proceedings of 2005 International Conference on Wireless Communications, Networking and Mobile Computing.

[2] Hung-yu Wei, Samrat Ganguly, Rauf Izmailov, and Zygmunt Haas,"Interference-Aware IEEE 802.16 WiMax Mesh Networks," The 61st

IEEE Vehicular Technology Conference (VTC Spring'05), May 2005.

[3] IEEE 802.16 standard