Simulation of VoIP traffic Simulation of VoIP traffic in 802.11n networksin 802.11n networks

Aya MireAya Mire

Niv TokmanNiv Tokman

Oren Gur-ArieOren Gur-Arie

ContentsContents

802.11n802.11n

Packet aggregationPacket aggregation

Project goalsProject goals

Project assumptionsProject assumptions

ImplementationImplementation

Simulation flowSimulation flow

Milestones Milestones

802.11n802.11n

Based on IEEE 802.11 – Standard for Based on IEEE 802.11 – Standard for wireless computer networkswireless computer networksProviding ability of working in a rate of at Providing ability of working in a rate of at least 100Mbps.least 100Mbps.Support work with MIMO – several Support work with MIMO – several transmitters and receivers for each stationtransmitters and receivers for each stationReverse direction communicationReverse direction communicationPacket AggregationPacket AggregationStill under development - TGn Still under development - TGn

Packet aggregationPacket aggregation

Reduces the overhead of control packets and Reduces the overhead of control packets and timeouts related to the 802.11 protocoltimeouts related to the 802.11 protocol

May be destined to single or multiple receiversMay be destined to single or multiple receivers

MPD

UH

eade

r

Leng

th

CR

C

MPD

UPa

yloa

d

FCS

MPD

UH

eade

r

Leng

th

CR

C

MPD

UPa

yloa

d

FCS

MPD

UH

eade

r

Leng

th

CR

C

MPD

UPa

yloa

d

FCS

MPD

UD

elim

iter

MPD

U

PSDU

Project goalsProject goals

Examine the influence of aggregated Examine the influence of aggregated communication on periodic information – communication on periodic information – with focus on VoIPwith focus on VoIP

Examine the influence of aggregation size Examine the influence of aggregation size (number of packets per aggregation) on (number of packets per aggregation) on network’s behavior network’s behavior

Project assumptionsProject assumptions

Centralized network environment (star Centralized network environment (star topology)topology)

VoIP data only (of two types: 10ms, 60 VoIP data only (of two types: 10ms, 60 bytes and 20ms, 80 bytes)bytes and 20ms, 80 bytes)

Aggregation is done only by APAggregation is done only by AP

No ACKsNo ACKs

ImplementationImplementation

NetworkSTA

Simulation manager

Statistics manager

Conversation Generator

STA

STA

AP

Simulation managerSimulation manager

Handles the main loop of the simulation – Handles the main loop of the simulation – the time counter (in step of 1us)the time counter (in step of 1us)

Gathers the statistics from the different Gathers the statistics from the different units of the systemunits of the system

Manages the conversation generatorsManages the conversation generators

Regular station (STA)Regular station (STA)

Represents a wireless client.Represents a wireless client.

Each STA contains Tx and Rx FIFOs for Each STA contains Tx and Rx FIFOs for both sending and receiving messages.both sending and receiving messages.

Data traffic between STAs goes through Data traffic between STAs goes through the AP.the AP.

STA generate and handles the different STA generate and handles the different control messages defined by 802.11n control messages defined by 802.11n protocolprotocol

APAP

Similar implementation and behavior to Similar implementation and behavior to STA.STA.

Buffers data from different STA until Buffers data from different STA until aggregation threshold is reached, or time aggregation threshold is reached, or time limit has expired.limit has expired.

Network unitNetwork unit

Simulates the traffic “on the air”Simulates the traffic “on the air”

Serves as a “pipe” between STAs and AP Serves as a “pipe” between STAs and AP (and vise-versa)(and vise-versa)

Inserts error into transmitted messagesInserts error into transmitted messages

Detects collisions of packets (and flags Detects collisions of packets (and flags them as erroneous)them as erroneous)

VoIP data generatorsVoIP data generators

Generate VoIP data packets and inserts Generate VoIP data packets and inserts them to the STA’s Tx FIFOsthem to the STA’s Tx FIFOs

Generation of data is periodic every 10ms Generation of data is periodic every 10ms or 20ms, and done simultaneously to two or 20ms, and done simultaneously to two STAs engaging in conversationsSTAs engaging in conversations

Several VoIP generators can work in Several VoIP generators can work in parallelparallel

StatisticStatistic

for each VoIP type:for each VoIP type:Total number of messages during simulation time.Total number of messages during simulation time.Number of messages successfully sent.Number of messages successfully sent.Average time of message transmission (from source to Average time of message transmission (from source to destination, via AP).destination, via AP).Average waiting time in AP buffer.Average waiting time in AP buffer.Average time from entering Tx FIFO to actual transmission Average time from entering Tx FIFO to actual transmission time.time.

Statistics without explicit reference to VoIP Statistics without explicit reference to VoIP type:type:

Number of aggregations less than max aggregation size.Number of aggregations less than max aggregation size.Average number of receivers in aggregationAverage number of receivers in aggregationNumber of collisions.Number of collisions.Number of control messages.Number of control messages.

Simulation flowSimulation flow

ST

A A

ctiv

ityP

HY

Tx

MA

C T

xA

P A

ctiv

ityP

HY

Tx

MA

C T

x

Bas

ic r

ate

non-

agg

IAC

MP

DU

(RT

S)

Bas

ic ra

te

non-

agg

RA

C M

PD

U

(CT

S)

ST

A A

ctiv

ityP

HY

Tx

MA

C T

xS

TA

Act

ivity

PH

Y R

xM

AC

Rx

Agg

P

PD

UD

ata

MP

DU

Dat

a M

PD

U

Bas

ic r

ate

non-

agg

Dat

a M

PD

U

Bas

ic r

ate

non-

agg

IAC

MP

DU

(RT

S)

Bas

ic r

ate

non-

agg

Dat

a M

PD

U

Bas

ic ra

te

non-

agg

IAC

MP

DU

(R

TS

)

Bas

ic r

ate

non-

agg

Rec

eive

d da

ta

NAV

NAVNAV

NAV

Bas

ic ra

te

non-

agg

RA

C M

PD

U

(CT

S)

NAV

NAV

DIFS

SIFS

1. Data arrives at Tx FIFO of STA A from VoIP data generator. IAC is sent.

2. AP receives IAC, wait SIFS and respond with RAC.

3. RAC received. STA A sends non-aggregated VoIP data

4. After DIFS, the operation is repeated by STA B5. Aggregation size is reached. AP send IAC followed by the aggregated data

6. Data is received by STA C

Project time tableProject time table

Week 1-2: Headers + Classes (data and Week 1-2: Headers + Classes (data and methods), Statistics unitmethods), Statistics unit

Week 3-5: STA, AP and Network unitWeek 3-5: STA, AP and Network unit

Week 6: Simulation manager, data Week 6: Simulation manager, data generatorsgenerators

Week 7: Integration and testing, analyze Week 7: Integration and testing, analyze simulation’s resultssimulation’s results