ns-3 for WiFiwifi-ks.org/archives/files/ns3-for-wifi.pdf · 2018-01-17 · ns-3 for WiFi Author *1cm Venkatesh RamaiyanDepartment of Electrical EngineeringIIT Madras, Chennai Created

ns-3 for WiFi

Venkatesh RamaiyanDepartment of Electrical Engineering

IIT Madras, Chennai

Venkatesh RamaiyanDepartment of Electrical EngineeringIIT Madras, Chennai (IIT Madras, Chennai)ns-3 for WiFi 27 August 2016 1 / 21

Outline

Simulators for WiFi

ns-3 for WiFi

An example program

ns-3 for WiFi research

References


WiFi Networks


WiFi Networks


WiFi Networks


Network Design, Operation and Management

Does your WiFi work?

coverage (AP placement, transmit power, etc)dynamic interference (co-channel interference, hidden nodes, non-WiFiinterference, etc)unfair channel access (random access, asymmetric traffic, etc)client/AP software and hardware (user association, processor, etc)

Good practices

planned deployment of access points (user density, coverage, etc)adaptive RRM (channel selection, transmit power control, userassociation, etc)bandwidth manager (based on traffic, client, QoS, fairness, etc)robust and learning algorithms



Does your WiFi work?

coverage (AP placement, transmit power, etc)dynamic interference (co-channel interference, hidden nodes, non-WiFiinterference, etc)unfair channel access (random access, asymmetric traffic, etc)client/AP software and hardware (user association, processor, etc)

Good practices

planned deployment of access points (user density, coverage, etc)adaptive RRM (channel selection, transmit power control, userassociation, etc)bandwidth manager (based on traffic, client, QoS, fairness, etc)robust and learning algorithms



Design parameters

number and location of APschannel of operationtransmit powertraffic and client load balancingscheduler and QoS provisioning

Challenges

interference from other networksheterogeneous support for standardsdynamic client and traffic profileheterogeneous algorithmsminimise cost of deployment, operation and maintenance



Design parameters

number and location of APschannel of operationtransmit powertraffic and client load balancingscheduler and QoS provisioning

Challenges

interference from other networksheterogeneous support for standardsdynamic client and traffic profileheterogeneous algorithmsminimise cost of deployment, operation and maintenance


Experiments, Analysis and Simulations

Experiments

specific viewcostlydifficult to replicateeasy to interpret

Analysis

generic viewcosts lesseasy to replicatedifficult to interpretation

Simulations

intermediate viewcosts lesseasy to replicateeasy to interpret



Experiments


Analysis


Simulations




Experiments


Analysis


Simulations



What simulators can do?

Validate network deployment

coverage and capacity in various zones

Performance evaluation for real-life scenarios

with thousands of devicessupport for heterogeneous standards and algorithmsfor dynamic traffic and mobility conditions

Test bed for new standards, applications and algorithms

Replicate deployment scenarios

an effective tool to debug errors and monitor network conditions


Network Simulator ns-3

ns-31 is a discrete event network simulator

C++ libraries with Python bindings

ns-3 is an open, extensible network simulation platform

free software licensed under the GNU GPLv2 licenseavailable for research, development and use

Supports WiFi among other protocols

application, transport, network, MAC/PHYpopular modules are FTP, TCP/UDP, IP, WiFi, LTE, LR-WPAN etcsupport for mobility, channel, real-time scheduling, etc

ns-3 supported by a large community of users and developers

1https://www.nsnam.orgVenkatesh RamaiyanDepartment of Electrical EngineeringIIT Madras, Chennai (IIT Madras, Chennai)ns-3 for WiFi 27 August 2016 8 / 21

WiFi in ns-3

Basic DCF with infrastructure and ad hoc modes

Support for 802.11a, 802.11b, 802.11g, 802.11n and 802.11ac

both 2.4GHz and 5GHz

MSDU and MPDU aggregation

QoS based EDCA and queueing extensions of 802.11e

Support for different channel models

Rate control algorithms such as Aarf, Arf, Minstrel, etc

Support for mesh and WAVE


WiFi Network Device Architecture in ns-3


An example program - a-simple-infrastructure-wlan.cc (1)

Include librariesinclude ”ns3/core-module.h”include ”ns3/network-module.h”include ”ns3/olsr-helper.h”include ”ns3/wifi-module.h”include ”ns3/applications-module.h”include ”ns3/mobility-module.h”



Configuration: Server —–(p2p link)—– AP —–(11n link)—– Wifi Clients//Create nodesNodeContainer ServerNode;ServerNode.Create(1);NodeContainer wifiApNode;wifiApNode.Create(1);

//Create p2p linksNodeContainer n0n1 = NodeContainer (ServerNode.Get(0),wifiApNode.Get(0));PointToPointHelper p2p;p2p.SetDeviceAttribute (”DataRate”, StringValue (”1Gbps”));p2p.SetChannelAttribute (”Delay”, StringValue (”1ms”));NetDeviceContainer d0d1 = p2p.Install (n0n1);



Configuration: Server —–(p2p link)—– AP —–(11n link)—– Wifi Clients//Create nodesNodeContainer ServerNode;ServerNode.Create(1);NodeContainer wifiApNode;wifiApNode.Create(1);

//Create p2p linksNodeContainer n0n1 = NodeContainer (ServerNode.Get(0),wifiApNode.Get(0));PointToPointHelper p2p;p2p.SetDeviceAttribute (”DataRate”, StringValue (”1Gbps”));p2p.SetChannelAttribute (”Delay”, StringValue (”1ms”));NetDeviceContainer d0d1 = p2p.Install (n0n1);



To set the standard as 80211nwifi.SetStandard (WIFI PHY STANDARD 80211n 5GHZ);

YansWifiChannelHelper channel;channel.SetPropagationDelay(”ns3::ConstantSpeedPropagationDelayModel”);channel.AddPropagationLoss (”ns3::FriisPropagationLossModel”);

phy.Set(”CcaMode1Threshold”,DoubleValue(-82));phy.Set(”TxPowerEnd”,DoubleValue(18));phy.Set(”TxPowerStart”,DoubleValue(18));



//Install net device containers in the AP and station wifi nodesmac.SetType (”ns3::StaWifiMac”, ”ActiveProbing”, BooleanValue (false),”QosSupported”, BooleanValue(true));NetDeviceContainer staDevice;staDevice = wifi.Install (phy, mac, wifiStaNode);

mac.SetType (”ns3::ApWifiMac”, ”BeaconInterval”, TimeValue(MicroSeconds(102400)), ”BeaconGeneration”, BooleanValue (true),”QosSupported”, BooleanValue(true));NetDeviceContainer apDevice;apDevice = wifi.Install (phy, mac, wifiApNode);



ON-OFF applicationonoff.SetAttribute (”OnTime”, StringValue(”ns3::ConstantRandomVariable[Constant=1]”));

onoff.SetAttribute (”OffTime”, StringValue(”ns3::ConstantRandomVariable[Constant=0]”));

onoff.SetConstantRate (ns3::DataRate (”33Mb/s”));onoff.SetAttribute (”PacketSize”, UintegerValue (payloadSize));source.Add(onoff.Install(ServerNode.Get(0)));


Scenario 1: Local and Internet Traffic

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Internet Server's client 1Internet Server's client 2

Local Server's client 1Local Server's client 2

TCP downlinks from local and Internet servertraffic from the Internet starvesWi-Fi is the bottleneck and MAC buffer overflowsTCP with better access dominates


Scenario 1: Local and Internet Traffic

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TCP downlinks from local and Internet server

WFQ with equal weight shares bandwidth equally


Scenario 2: Asymmetry with Direction of Flow

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Downlink client 1Downlink client 2

Uplink client 1Uplink client 2

TCP downlinks and uplinks (identical large file transfers)aggregate throughput of downlink flows is almost zeroWi-Fi is the bottleneck and MAC buffer overflowsthroughput is unfair due to asymmetric response of TCP


Scenario 2: Asymmetry with Direction of Flow

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TCP downlinks and uplinks (identical large file transfers)

WFQ with adjusted weights provide equal share of bandwidth!


Scenario 3: Device Limitations

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TCP Max Advertised Window Size=8000BytesTCP Max Advertised Window Size=8000Bytes


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TCP downlinks (identical large file transfers)

average throughput is limited by the TCP max advertised windowWFQ with equal weights ensures fair channel access


Opportunities

Performance evaluation for network scenarios of interest

Contribute latest standards and algorithms to ns-3

Develop novel algorithms (or) identify critical scenarios

Develop new use cases

Prakash Agrawal and Mythili Vutukuru, “Trace based application layermodelling in ns-3”, NCC 2016, available from ns-3.26LTE/WiFi networks


Documents

ns-3 for WiFiwifi-ks.org/archives/files/ns3-for-wifi.pdf · 2018-01-17 · ns-3 for WiFi Author *1cm Venkatesh RamaiyanDepartment of Electrical EngineeringIIT Madras, Chennai Created