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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
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MPD
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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