802.11 WLAN MAC Layer Modeling Lisa Driskell Yejun Gong Xueying Hu - - PowerPoint PPT Presentation

▶
802 11 wlan mac layer modeling
SMART_READER_LITE
LIVE PREVIEW

802.11 WLAN MAC Layer Modeling Lisa Driskell Yejun Gong Xueying Hu - - PowerPoint PPT Presentation

Mar 18, 2023 24 likes •277 views

TE AM 2 : 802.11 WLAN MAC layer modeling August 17, 2007 802.11 WLAN MAC Layer Modeling Lisa Driskell Yejun Gong Xueying Hu Purdue University Michigan Technological University of Michigan University Rashi Jain Mechie Nkengla New Jersey

slide-1
SLIDE 1

TE AM 2: 802.11 WLAN MAC layer modeling

Mentor: Radu V. Balan

802.11 WLAN MAC Layer Modeling

Lisa Driskell Yejun Gong Xueying Hu

Purdue University Michigan Technological University University of Michigan

Rashi Jain Mechie Nkengla

New Jersey Institute of Technology University of Illinois-Chicago

August 17, 2007

slide-2
SLIDE 2

TE AM 2: 802.11 WLAN MAC layer modeling

Outline

Objective Overview ns-2 Results (.nam) Results (.tr) Conclusions Future Objectives

slide-3
SLIDE 3

TE AM 2: 802.11 WLAN MAC layer modeling

Project Objective: Analyze the relationships

  • f the parameters for a modified EO

Markov model and validate the model under certain assumptions with (ns2) network simulations.

Objective

slide-4
SLIDE 4

TE AM 2: 802.11 WLAN MAC layer modeling

Overview

MAC MAC

Packets Generated

IFQ Agent/UDP

Transmission

Agent/Null

Final Destination

System Layout

slide-5
SLIDE 5

TE AM 2: 802.11 WLAN MAC layer modeling

p

Overview

slide-6
SLIDE 6

TE AM 2: 802.11 WLAN MAC layer modeling

Prob (packet dropped due to collision) = Avg # of retries =

) p 1 ( p 1 p

L

− −

1 L

p +

pL(1-p) + pLp

…

pb(1-p)

…

p2(1-p) p(1-p) 1-p Probability L … b … 2 1 Exact # retries

Previous Analysis of Markov Model

Overview

slide-7
SLIDE 7

TE AM 2: 802.11 WLAN MAC layer modeling

  • Analyzed Markov model
  • Compared analytical results with computed

results to verify the analysis.

  • Use analytical results compared with network

simulations to determine whether the system can indeed be modeled with a Markov chain.

Outline

Overview

slide-8
SLIDE 8

TE AM 2: 802.11 WLAN MAC layer modeling

Ns-2

Ns-2 simulator

Ns-2 Simulator

Input .tcl file .tr file Output Trace File .nam file

slide-9
SLIDE 9

TE AM 2: 802.11 WLAN MAC layer modeling

Ns-2

Ns-2 simulator

  • Closely relates to real world.
  • A packet-based event-driven simulation.
  • Can incorporate the wireless mechanism
  • Allows for mobile stations
  • Provides animations
slide-10
SLIDE 10

TE AM 2: 802.11 WLAN MAC layer modeling

Ns-2

Example of a ns2 simulation

slide-11
SLIDE 11

TE AM 2: 802.11 WLAN MAC layer modeling

Nam Trace

Nam Trace Format <type> -t <time> -s <source id> -d <destination id> -p <pkt-type> -e <extent> -c <conv> -a <packet attribute> -i <id> -k <trace level> 0~ #pkts i AGT, MAC k cbr, ACK 0~ NSTA 0~ simTime h, r, d, +, - p s t type

slide-12
SLIDE 12

TE AM 2: 802.11 WLAN MAC layer modeling

Nam Trace : Medium Busy Time

The packet is on the air from t, if at t type= ‘h’ AND k= ‘MAC‘ (Hop) The medium is busy in [ t, t+ pktTransTime] The medium is busy in collision case.

TxFrame 1 TxFrame 2 Busy Collision

slide-13
SLIDE 13

TE AM 2: 802.11 WLAN MAC layer modeling

Nam Trace : Medium Busy Time Medium Busy Time ? , if NSTA ? < critical number Medium Busy Time ? , if NSTA ? > critical number

slide-14
SLIDE 14

TE AM 2: 802.11 WLAN MAC layer modeling

1

  • Hop

# cket) Retries(pa # with ThisNode pktsSendTo # packet this

  • f

Retries # (node) AvgRetries

hisNode pktSendToT

= =

∑

Numerical: Theoretical: But how to find p?

retries. # max the is L and y probabilit collision the is p where ) p 1 ( * p

  • 1

p (node) AvgRetries

L

− =

slide-15
SLIDE 15

TE AM 2: 802.11 WLAN MAC layer modeling

1 L

c pktTransSu Col pktDropDue Col pktDropDue p

+

+ =

pktSend= pktDropDueCol+ pktDropDueQueue+ pktDropDueEnd+ pktTransSuc Type=‘h’ AND k=‘AGT’ AND p=‘cbr’ Type=‘d’ AND k=‘IFQ’ AND p=‘cbr’ LastHopTime+pktTransTime>sucTime Type=‘r’ AND k=‘AGT’ AND p=‘ACK’

slide-16
SLIDE 16

TE AM 2: 802.11 WLAN MAC layer modeling

Results (.nam)

Average number of retries

slide-17
SLIDE 17

TE AM 2: 802.11 WLAN MAC layer modeling

Results (.nam)

Average number of retries

slide-18
SLIDE 18

TE AM 2: 802.11 WLAN MAC layer modeling

Example of a .tr output

slide-19
SLIDE 19

TE AM 2: 802.11 WLAN MAC layer modeling

Results (.tr)

Average number of retries

From simulation From calculation

slide-20
SLIDE 20

TE AM 2: 802.11 WLAN MAC layer modeling

Results (.tr)

Average number of retries for AP with varying packet period and offset

slide-21
SLIDE 21

TE AM 2: 802.11 WLAN MAC layer modeling

Average number of retries with varying packet period and offset

5 Stations

slide-22
SLIDE 22

TE AM 2: 802.11 WLAN MAC layer modeling

Results (.tr)

Comparison between of the average number of retries from calculation and simulation

slide-23
SLIDE 23

TE AM 2: 802.11 WLAN MAC layer modeling

Conclusions

Conclusions

  • Estimated parameter ‘p’
  • Determined the saturation value
  • Established validity of the Markov model
  • Established importance of assumption of

synchronicity

slide-24
SLIDE 24

TE AM 2: 802.11 WLAN MAC layer modeling

Future Objectives

  • Use the .nam and .tr files to extract information about

– Average service time – Average wait time

  • Use the above times to find relationships between

parameters

  • Compare computed results and simulated results for

different packet arrival configurations

  • Compute the throughput/delay
  • Create a deterministic model

(Someone Else’s) Future Objectives

slide-25
SLIDE 25

TE AM 2: 802.11 WLAN MAC layer modeling

Questions

Questions?