Routing and Admission Control in IEEE 802.16 Distributed Mesh Networks

1

Routing and Admission Control in IEEE 802.16 Distributed Mesh

NetworksTzu-Chieh Tsai

Dept. of Computer ScienceNational Chengchi University

Taipei, Taiwan

2

Outline

Introduction

Problems

Related Work

Our Routing and CAC Algorithm

Simulations

Conclusion

3

Outline

IntroductionWireless Mesh Networks

IEEE 802.16 Mesh Mode

Problems

Related Work


Simulations

Conclusion

4

Introduction—Wireless Mesh Networks

5

Introduction—Wireless Mesh Networks

Ad-hoc network basisSelf organization

Fault tolerance

Scalability

Lower infrastructure cost

Wider coverage

Standard activities802.11s (in progress)

802.15.5 (in progress, mainly in PHY)

802.16Mesh mode is already included in standards.

6

IEEE 802.16 mesh mode

Internet

BS

BSSS

SS

7

IEEE 802.16 mesh mode

TerminologyMesh Base Station (MBS or BS)Mesh Subscriber Station (MSS or SS)Extended neighborhood (2-hop neighbors)

Defers from PMP mode (Point to Multi-Point)Traffic can occur directly between SSsOnly TDD is supported in MeshFrame format

Not compatible

A frame is composed withControl subframe

Network control subframeSchedule control subframe

Data subframe

8

IEEE 802.16 Mesh Mode Frame Formats

Frame n-1 Frame n Frame n+1

NENT NCFG NCFG … NCFG

Network Control subframe

CSCH CSCF CSCF … DSCH

Schedule Control subframe




CSCH CSCF CSCF … DSCHCSCH CSCF CSCF … DSCH


Data subframe

slot slot slot … slot slot

Data subframe












Data subframe


Data subframe


9


Scheduling mechanism:

CentralizedUsing MSH-CSCH, MSH-CSCF msgs.

DistributedCoordinated

Uncoordinated– Both using MSH-DSCH msgs.– Mesh Distributed Scheduling messages

10


In distributed coordinated mesh mode, each node periodically broadcasts :

MSH-NCFGMesh-Network Config

Exchanges the basic parameters between SSs

– ID of BS, hop count to BS, number of neighbors, …

MSH-DSCH msgs.Mesh-Distributed Scheduling

Both using Mesh election algorithm to determined next transmission time.

11


The information elements (IEs) of MSH-DSCH msgs.

Scheduling IE:Determines the next transmission time of MSH-DSCH msgs.

To avoid collision of MSH-DSCH msgs.

Request IE:Convey the resources over a link

Availability IE:Carry the information of the available resources

Grant IE:Convey the confirm information of the resources

12

IEEE 802.16 Mesh Mode—3-way Handshake

MSH-DSCH: Request

Src. sends to dest. along with MSH-DSCH: Availibilities

Indicate the empty timeslots of src. Node

MSH-DSCH: Grant

Dest. Chooses a range of empty timeslots according to MSH-DSCH:request, and,

Dest. replies with this msg.

MSH-DSCH: Grant

Src. Copies the received grant and sends it back to destination node

Requester Granter

MSH-DSCH:RequestAnd

MSH-DSCH:availbility

MSH-DSCH:Grant

MSH-DSCH:Grant

Requester Granter

MSH-DSCH:RequestAnd


MSH-DSCH:Grant

MSH-DSCH:Grant

13

IEEE 802.16 QoS Classes

Four QoS classesUnsolicited Grant Service (UGS)

Real-time Polling Service (rtPS)

Non-real-time Polling Service (nrtPS)

Best Effort (BE)

Class name Traffic type Application

UGS Real-time Constant Bit Rate (CBR) Voice over IP (VoIP)

rtPS Real-time Various Bit Rate (VBR) Real-time video

nrtPS Non-real-time Bandwidth-sensitive FTP

BE Non-real-time HTTP, Telnet

14

IEEE 802.16 Mesh Mode –QoS

Mesh mode uses CID (Connection ID) to define the service parameters

ReliabilityTo re-transmit or not

PriorityThe priority of the connection

Drop PrecedenceWhen congestion occurs, the likelihood of dropping the packets

15

Outline

Introduction

Problems

Related Work


Simulations

Conclusion

16

Problems

QoS provisioning for each class, we need:A Routing Method suitable in 802.16 distributed mesh mode

A way to do admission control

The above 2 things are not specified in the standard

Our solutions:SWEB (Shortest-Widest Efficient Bandwidth) metrics for routing

TAC (Token-bucket based Admission Control)

17

Outline

Introduction

Problems

Related Work


Simulations

Conclusion

18

Related Work

In [3], a token-based call admission control and a math model is proposed under IEEE 802.16 PMP mode

The bandwidth of a flow is estimated as

2fd and f

dm where,

1-m

bfr i

ii

i

ii

19

Related Work -Token Bucket Mechanism

Token bucket parametersToken rate r

Bucket size b

In time duration t, the output volume of data would be:

, at most.

Token rate r

Packet Queue

Bucket size b

Output

Token rate r

Packet Queue

Bucket size b

Output

btr *

20

Related Work

In [7], routing metrics “ETX” is proposedExpected Transmission Count

Under 802.11 ad-hoc networks

Forwarding delivery ratio: ,reverse delivery ratio:

Determined by sending probe packets

ETX is calculated as:

fd rd

rf ddETX

*

1

21

Outline

Introduction

Problems

Related Work

Our Routing and CAC AlgorithmRouting

Modified 3-way handshake

TAC algorithm

Simulations

Conclusion

22

Routing and CAC algorithms

Static Routing is suitable in IEEE 802.16 mesh networks:

Stations do not move or have the minimum mobility

Topology and channel conditions do not change severely

IEEE 802.16d standard does not support mobility

Providing QoS of one flow over multiple routes can be in-efficient and difficult

23

Routing

To minimize delay and achieve good throughputPi,j: packet error rate of link (i,j)

Ci,j: Capacity of link (i,j)

A bandwidth of a link is

Node 1 Node 2 Node 3 Node 4

2,1p 3,2p 4,3p

2,1C 3,2C 4,3C

)1( ,, jiji pC

24

Routing

Capacity of all links = C

Effective bandwidthPath1

=C*min((1-0.1),(1-0.2),(1-0.1))/2

=0.4*C

Path2=0.25C

Path3=0.4C

Path 3 is preferable.divided by hopCount

Path1=0.4C/3

Path3=0.4C/2

S D

0.1

0.2

0.1

0.5 0.5

0.2 0.2

Path1

Path2

Path3

25

SWEB Routing

Routing is done off-line.

Path metric=

h: hop countSWEB (Shortest-Widest Efficient Bandwidth) Metrics

Node 1 Node 2 Node 3 Node 4

2,1p 3,2p 4,3p

2,1C 3,2C 4,3C

h

pCpCpC hhhh 1

2

))1(),...,1(),1(min( 1,1,3,23,22,12,1

26

Outline

Introduction

Problems

Related Work



TAC algorithm

Simulations

Conclusion

27


To shorten the call setup time, we modified the 3-way handshake

Original 3-way handshake:

Requester Granter

MSH-DSCH:RequestAnd


MSH-DSCH:Grant

MSH-DSCH:Grant

Requester Granter

MSH-DSCH:RequestAnd


MSH-DSCH:Grant

MSH-DSCH:Grant

28


Original 3-way handshake in a multi-hop environment

29


30

Outline

Introduction

Problems

Related Work



TAC algorithm

Simulations

Conclusion

31

Bandwidth Estimation

Assume that each flow is controlled by the token bucket mechanism.Each flow reports the parameters when it is initiated:

r: token rateb: bucket sized :Delay requirement (for real-time traffics)

Using token bucket, the required bandwidth is:

Over-estimated.

f

bfr

32


t t+7f

ri*f ri*f ri*f

t+4ft t+7f

ri*f ri*f ri*f

t+4f

S

D

33


t+6f

ri*f ri*f ri*f ri*f

t+12ft+5f

bi

ri*f ri*f ri*f ri*f ri*f

t+9ft+6f

ri*f ri*f ri*f ri*f

t+12ft+5f

bi


t+9f

S

D

34


t+6f

ri*f ri*f ri*f ri*f

t+12ft+5f


t+9f

bi/

mi-1bi/

mi-1

t+6f

ri*f ri*f ri*f ri*f

t+12ft+5f


t+9f

S

D

35


We estimate the Max. volume transmitted by a real-time flow in a frame as:

,where

ii

i hf

dm

i

ii m

bfr

36

TAC (Token-bucket Based Admission Control) algorithm

Goal:Guarantee delay requirements for real-time flows

Avoid starvation

To guarantee delayUse the above-mentioned bandwidth estimation.

To avoid starvationsSet minimum usage of each class:

CBR_min, VBR_min, and BE_min.

37

TAC algorithm

Concept:

38

TAC algorithm

Fields in CID (connection ID) are used to identify QoS levels

Priority

(3 bits)

Reliability

(1 bit)

Drop Precedence

(2 bits)

CBR 7 0 0

CBR_DG 4 0 1

VBR 6 0 0

VBR_DG 3 0 2

BE 5 1 0

BE_DG 2 1 3

39

Outline

Introduction

Problems

Related Work


SimulationsRouting

TAC

Conclusion

40

SimulationsParameters

ParametersFrame length = 8 ms

Slot capacity = 144 bytes

Data timeslots =165

QPSK coding rate =3/4

676 OFDM symbols per frameFor CTRL subframe=16

For DATA subframe=660

4 OFDM symbols per slot

41

SimulationsRouting

Topology16 nodes

4 km * 4km

Radio range = 1.5 km

Node 16 is the MBS.

42

SimulationsRouting

98.316.1106.491.1198.382.004.2

25456.102501.481.1132.55

86.02559.082.02525.656.177.225.6432.6581.1152.58

55.1266.1132.1191.102598.3

56.60156.109.485.60156.104.7256.177.259.04

82418.6023.182.0456.5554.5904.211.1118.1304.211.1023.1

4421.1156.12504.22523.1

04.204.204.24054.57

56.156.125.682.023.101.1

77.289.397.2411.477.242522.1102.0

77.225.677.225.604.277.267.1104.2249.6

56.5254.5977.223.11.22525.6998.0

08.1267.1177.2425.652.5871.13

4425.62577.211.1104.2098.24

125.6125.682.0252525404.204.2

23.101.423.169.0

Packet error rate over links: ( in 1/100 )

43

SimulationsRouting

ETX

44

SimulationsRouting

Shortest Path

45

SimulationsRouting

Proposed Routing metrics

46

SimulationsRouting

Since we primarily focus on VBR traffics, VBR traffics are compared across 3 routing trees.

Throughput

Delay

Jitter

The number of each class traffic flow is ranging from 5 to 25.

47

SimulationsRouting

Throughput

0

1000

2000

3000

4000

5000

6000

7000

8000

5 10 15 20 25

number of flows

bps

ETX

Shortest

SWEB

48

SimulationsRouting

Avg. Delay

0

10

20

30

40

50

60

70

5 10 15 20 25

number of flows

ms

ETX

Shortest

SWEB

49

SimulationsRouting

J itter

0

5

10

15

20

25

30

35

5 10 15 20 25

Number of flows

tim

e (m

s)

ETX

shortest

SWEB

50

Outline

Introduction

Problems

Related Work


SimulationsRouting

TAC

Conclusion

51

Simulationsparameters

Minimum usage:CBR 10 timeslots

VBR 40 timeslots

BE 75 timeslots

Token rate

(bps)

Bucket size

(bits)

Delay requirement

CBR 960 64 40 ms

VBR 2000k 4000 80 ms

BE 750k 2000 --

52

SimulationsCAC

(wimax) throughput

01000

20003000

40005000

60007000

8000

5 10 15 20 25

number of flows

bps

CBR

VBR

BE

total

(TAC) throughput

010002000300040005000600070008000

5 10 15 20 25

number of flows

bps

CBR

VBR

BE

total

53

SimulationsCAC

avg. delay

0

10

20

30

40

50

60

70

5 10 15 20 25

number of flows

dela

y tim

e (m

s)

CBR

VBR

BE

avg. delay

0

20

40

60

80

100

120

140

5 10 15 20 25

number of flows

dela

y tim

e (m

s)

CBR

VBR

BE

CBRDG

VBRDG

BEDG

WiMax TAC is added

54

SimulationsCAC

exceeds delay requirement

02468

101214

5 10 15 20 25

number of flows

perc

entag

e (%

)

CBR

VBR

exceeds delay requirement

01234567

5 10 15 20 25

number of flows

perc

entag

e (%

)

CBR_DG

VBR_DG

WiMax TAC is added

55

Outline

Introduction

Problems

Related Work


Simulations

Conclusion

56

Conclusion

We proposes a CAC (called TAC) mechanism thatguarantee the delay requirements of real-time traffic flows, and

Avoid starvations

A simple routing metric SWEB that is suitable for IEEE 802.16 mesh networks

A modified 3-way handshake thatReduces call setup time

57

Reference[1] IEEE, “IEEE Standard for Local and metropolitan area networks Pa

rt 16: Air Interface for Fixed Broadband Wireless Access Systems”, IEEE standard, October 2004.

[2] Harish Shetiya and Vinod Sharma, "Algorithms for routing andcentralized scheduling to provide QoS in IEEE 802.16 mesh networks",Proceedings of the 1st ACM workshop on Wireless multimedianetworking and performance modeling ,WMuNeP '05. Pages: 140-149.[3] Tzu-Chieh Tsai, Chi-Hong Jiang, and Chuang-Yin Wang, "CAC andPacket Scheduling Using Token Bucket for IEEE 802.16 Networks", inJournal of Communications (JCM, ISSN 1796-2021), Volume : 1 Issue :

2, 2006. Page(s):30-37. Academy Publisher.

58

Reference[4] Fuqiang LIU, Zhihui ZENG, Jian TAO, Qing LI, and Zhangxi LIN,"Achieving QoS for IEEE 802.16 in Mesh Mode",8th InternationalConference on Computer Science and Informatics, Salt Lake City, USA[5] Hung-Yu Wei, Samrat Ganguly, Rauf Izmailov, and Zygmunt J. Haa

s, "Interference-Aware IEEE 802.16 WiMax Mesh Networks", inProceedings of 61st IEEE Vehicular Technology Conference (VTC 200

5 Spring).[6] Min Cao, Qian Zhang, Xiaodong Wang, and Wenwu Zhu, "Modelling

and Performance Analysis of the Distributed Scheduler in IEEE 802.16 Mesh Mode", Proceedings of the 6th ACM international symposium on Mobile ad hoc networking and computing

59

Reference[7] Douglas S. J. De Couto, Daniel Aguayo, John Bicket , and Robert M

orris, “A High-Throughput Path Metric for Multi-Hop Wireless Routing”, ACM MobiCom ’03.

Date post:	15-Jan-2016
Category:	Documents
Upload:	yardan
View:	32 times
Download:	0 times

Routing and Admission Control in IEEE 802.16 Distributed Mesh Networks

Documents