Implementa)onandValida)onofanIEEE802.11ahModuleforns-3LeTian,Sébas)enDeronney,StevenLatré,JeroenFamaey

UniversityofAntwerpeniMinds,Belgium

https://www.uantwerpen.be/en/rg/mosaic/software/ieee-802-11ah/

Tableofcontent

1. 802.11ah overview

2. Implementation in ns-3

3. Evaluation

1. 802.11ah overview

2. Implementation in ns-3

3. Evaluation

Comparing802.11ahtoWPANandLPWAN

Distance (m)

Rate (kbps)

10 100 1000

10

100

1000

1 LoRa

Sigfox

Dash7

802.11ah

ZigBee BLE

10x 10x

802.11ahinnumbers

ZigBee (802.15.4)

Bluetooth Smart

(802.15.1) HaLow

(802.11ah)

Frequency band

Sub-1Ghz, 2.4Ghz 2.4Ghz Sub-1Ghz

Channel bandwidth 0.3 – 2Mhz 2Mhz

1 – 2 Mhz (4, 8, 16 optional)

Data rate 20 – 250 kbps up to 1Mbps 0.15 –78 Mbps

Range 10 – 100m 300m 100 – 1000m

New802.11ahMACfeatures

High scalability

Fast association

Restricted Access

Window (RAW)

Low power consumption

TIM segmentation

Target Wake Time (TWT)

Subchannel selective

transmission

Fastassocia)on

Send association

request Association processing

Stations AP

Normal association

Fastassocia)on

generate value V

generate random number R

R <=V?

Yes

Send association

request

Waiting next beacon

No Add V to

beacon frame

Association processing

Stations AP

Fast association

AP set a threshold T

QL > T?

Yes AP decrease threshold T

AP increase threshold T

No

AP Check its queue length QL

Example of changing value v

“11-12-0112-04-00ah-supporting-of-the-authentication-association-for-large-number-of-stations.pptx”

RestrictedAccessWindow(RAW)beacon beacon

Without RAW, any stations can access

Time T Time T+1

RestrictedAccessWindow(RAW)

RAW 1 RAW 2

slot 0 slot 1 … slot N

Equal size RAW slots

beacon beacon

Any stations can access Any stations can access

Only be accessed by stations belong it

50%

Without RAW 32 RAW slots

Beacon !carrying RPS!

Beacon!carrying RPS!

1st back !off function!

Doze state!

1st back !off function!

1st back !off function!

1st back !off function!

slot 0! Slot 1! … …! Slot NRAW-1!

Doze state! 2nd back! off function! Doze state!

RAW!

Station 1, assigned to RAW slot 1!

Station 2, not belongs to current RAW group !

Two stage backoff of RAW!

AP!

Tableofcontent

1. 802.11ah overview

2. Implementation in ns-3

3. Evaluation

1. 802.11ah overview

2. Implementation in ns-3

3. Evaluation

PHYandMACimplementa)oninns-3

•  Physical layer •  MCS0~10 modulation/coding schemes for bandwidths 1—

16Mhz

•  MAC layer •  Association ID (AID) assignment •  Fast association mechanism •  Restricted access window (RAW)

Source code: https://github.com/MOSAIC-UA/802.11ah-ns3

ns-3wifimodel

DcaTxop/EdcaTxopN

MacHigh (ApWifiMAC/StaWifiMac)

MacLow

star transmission

enqueue packets

MacRxMiddle DcfManager

WifiPhy/YansWifiPhy

send packets receive packets

RTS/CTS /DATA/ACK transaction

receive

packet queue fragmentation retransmission

receive packets DCF function

access granted

request access

listener

listener

WifiChannel PropagationDelayModel

PropagationLoss Model

get delay get signal strength

send packets

InterferenceHelper/ErrorRateModel

get PER

PHY

MAC

RAWrelatedmodulesinAPside

Set RAW attributes

Create RPS element

SendOneBeacon ( )

Assign AID to stations SendAssocResp ( )

Create AuthenCtrl element

Add these element into Beacon

Adjust Authencation Threshold

Extract RPS element

Get its own RAW slot

Control two stage back-off

StaWifiMac:: startRAW ( )

Get AID

Read association response packets

Extract AuthenCtrl element

Get association threshold

Send association request or not

StaWifiMac::received ( )

Start/stop second back-off

Store/restore back-off value

Read received beacon

RAWrelatedmodulesinsta)onside

DcaTxop/EdcaTxopN module DcfManager module

StaWifiMac:: startRAW ( )

Fastassocia)onrelatedmodulesinAPside

Add RAW attributes

Create RPS element

SendOneBeacon ( )

Assign AID to stations SendAssocResp ( )

Create AuthenCtrl element

Add these element into Beacon

Adjust Authencation Threshold

DcaTxop/EdcaTxopN class DcfManager class

Extract RPS element

Get its own RAW slot

Control two stage back-off

StaWifiMac:: startRAW ( )

Get AID

Read association response packets

StaWifiMac:: SendAssociationRequest ( )

Extract AuthenCtrl element

Get association threshold

Send association Request or not

StaWifiMac::received ( )

Start/stop second back-off

Store/restore back-off value

Read received beacon

Fastassocia)onrelatedmodulesinsta)onside

Tableofcontent

1. 802.11ah overview

2. Implementation in ns-3

3. Evaluation

1. 802.11ah overview

2. Implementation in ns-3

3. Evaluation

Simula)onsetup

•  STAs randomly placed around the AP •  Log Distance Propagation Loss Model •  Constant rate model •  Variables

•  Number of STA •  Traffic load •  Number of RAW groups(slots)

•  Metrics •  Throughput •  Latency

Pathlosswithdifferentrange

NistErrorRate Model YansErrorRate Model

Date rate model MCS10, 1 MHz need to be implemented

Fastassocia)onVSnormalassocia)on

Fast association scales better as number of stations increase.

PerformanceofvariousRAWslotsnumbers(oneRAWgroup)

For large scale/traffic network, larger number of RAW slots performs better in terms of throughput and latency.

Queue of 10 packets

PerformanceofvariousRAWgroups

L. Tian, J. Famaey, and S. Latre. Evaluation of the ieee 802.11ah restricted access window mechanism for dense iot networks. WoWMoM, June 2016.

RAW results in bigger gain at higher traffic loads.

Many RAW groups is catastrophic for latency.

Simula)onresultssummary

•  Fast association scales better as number of stations increase.

•  RAW achieves better performance for large scale/traffic load.

•  Optimal RAW groups determined by •  metric (throughput, latency) •  traffic load，station number

•  RAW optimization algorithm needed !