Wireless Sensor Networks
Content
AbstractThis project presents the performance
analysis of Wireless Sensor Network (WSN) used in the
high-end applications such as weapons sensor ship,
biomedical applications, habitat sensing and seismic
monitoring. Recently WSN also focuses on national
security applications and consumer applications. This
project shall demonstrate the performance of WSN
models, which are created and simulated using QualNet
Developer software simulator. Several sensor nodes were
uniformly deployed in the networks to create sensing
phenomena. The simulation results recorded were the
amount of data packets sent and received by each node,
the throughput and the delay. All these graphical
simulation results from several WSN models will be
compared and analyzed separately. Therefore, the
important factors and issues pertaining to the WSN
performance will also be determined and describe briefly .
CHAPTER 1
INTRODUCTION
Wireless Sensor Network (WSN) are a trend of the last few
years due to the advances made in wireless communication,
information technologies and electronics filed. The
development of low-cost, low-power, a multifunctional sensor
has received increasing attention from various industries [1].
WSN is a wireless network composed of autonomous and
compact devices called sensor nodes or motes. A sensor
network is designed to detect phenomena, collect and process
data and transmit sensed information to users. Sensor nodes or
motes in WSNs, are small sized and are capable of sensing,
gathering and processing data while communicating with other
connected nodes in the network, via radio frequency (RF)
channel.
CHAPTER 2
ARCHITECTURE OF SENSOR NODE
The system architecture of a sensor node is as shown below.A sensor node
consists of a radio transceiver or optical as the communication unit, sensor as
the sensing unit, a microcontroller for the processing unit and battery as the
power unit.The hardware device in the sensing unit may consist up to several
sensors. This device produces measurable response to change which acts as
an interface between motes to the environment. Measurable changes are,
vibration, temperature,sound, motion, pollutants or pressure in environmental
conditions.
The processing unit is responsible for the collecting and
processing of the captured signal from the sensor unit. These
signals are then transmitted to the network. It determines both
energy consumption as well as computational capabilities of
the sensor node.
The power unit consisting of battery supplies power to the
sensor node. It is important to choose the battery type since
durability will affect the design of sensor node.
The Wireless Sensor Networks are being used in many
ways. Traditionally, it has been used in the high-end
application such as radiation and nuclear-threat detection
systems, weapons sensors for ships, biomedical applications,
habitat sensing and seismic monitoring. Recently, Wireless
Sensor Networks are focusing on national security
applications and consumer applications such as [3]:
1. Military applications
Monitoring, tracking and surveillance of borders
Nuclear, biological and chemical attack detection
Battle damage assessment
2. Environmental applications
Flood and oceans detection
Forest fire detection
3. Health applications
Drug administration
Remote monitoring of physiological data
Tracking and monitoring doctors and patients inside a
hospital
4. Home applications
Automated meter reading
Home automation
Instrumented environment
5. Commercial applications
Monitoring vibration that could damage the buildings
structures
Monitoring traffic flow and road condition
Vehicle tracking and detection
CHAPTER 3
PROTOCOLS USED FOR WIRELESS SENSOR NETWORKS
This necessity for energy efficient operation
of a WSN has prompted the development of new protocols in
all layers of the communication stack.
protocols like
Bellman-Ford, Ad-Hoc on-Demand Routing (AODV),
Dynamic Source Routing (DSR), Dynamic MANET
On-demand Protocol (DYMO)
Taxonomy of Protocols and detailed
description is given below:
In uniform protocols there is no hierarchy in network, all
nodes send and respond to routing control messages at the
same manner.
In non-uniform protocols there is an effort to reduce the
control traffic burden by separating nodes in dealing with
routing information. Non-uniform protocols fall into two
categories: protocols in which each node focuses routing
activity on a subset of its neighbors and protocols in which the
network is topologically partitioned [8].
Topology-based protocols use the principle that every node
in a network maintains large-scale topology information. This
principle is just the same as in link-state protocols.
Destination-based protocols do not maintain large-scale
topology information. They only may maintain topology
information needed to know the nearest neighbors.
Proactive protocols, which are also known as table-driven
protocols, maintain all the time routing information for all
known destinations at every source [9].
In on-demand i.e. in reactive protocols the route is only
calculated on demand basis. That means that there is no
unnecessary routing information maintained.
Type of Cast
Another type of classification can be done via, type caste
property. i.e, whether they use
· Unicast
· Geo-cast
· Multicast
· Unicast: Unicast forwarding means one to one
communication. i.e, one source transmits data packets to
a single destination.
· Geo-cast: The main aim of Geo-cast is to deliver the data
to a group of nodes situated inside a specified
geographical area [10].
· Multicast: Multicast means one to many i.e, when a node
needs to send same data to multiple destinations.
Bellman-Ford Routing Protocol
Bellman-Ford Routing Algorithm, also known as
Ford-Fulkerson Algorithm, is used as a distance vector
routing protocol. Routers that use this algorithm have to
maintain the distance tables, which tell the distances and
shortest path to sending packets to each node in the network.
The information in the distance table is always updated by
exchanging information with the neighbouring nodes.
Destination Based Routing:
Ad-Hoc on-Demand Routing
AODV is a modification of the DSDV algorithm. When a
source node desires to establish a communication session, it
initiates a path-discovery process to locate the other node.
The source node broadcasts a RREQ packet with its IP
address, Broadcast ID (BrID), and the sequence number of
the source and destination [11]. While, the BrID and the IP
address is used to uniquely identify each request, the sequence
numbers are used to determine the timeliness of each packet .
CHAPTER 4
Sensor Networks
ZigBee is a specification for a suite of high level communication protocols
using small, low-power digital radios based on the IEEE 802.15.4 standard
for Wireless Personal Area Networks (WPANs). ZigBee is targeted at RF
applications that require a low data rate, long battery life, and secure
networking. These networks are aimed at automation, remote control, and
Wireless Sensor Network (WSN) applications. The IEEE 802.15.4 standard
defines the physical layer (PHY) and Medium Access Control sublayer
(MAC) specifications as the wireless communication standard for low-power
consumption, Low-Rate WPAN (LR-WPANs).
Layers in Sensor Networks
1.Physical Layer
2.MAC Layer
3.Application Layer
ZigBee PHY
The QualNet ZigBee PHY is based on the IEEE 802.15.4-2006 standard
The PHY layer provides an interface between the MAC layer and the
physical radio channel. It provides two services, accessed through two
service access points (SAPs). These are the PHY data service and the PHY
management service. The PHY layer is responsible for the following tasks:
•Activation and deactivation of the radio transceiver
Turn the radio transceiver into one of the three states,(i.e., transmitting,
receiving, or off (sleeping)) according to the request from MAC sublayer.
The turnaround time from transmitting to receiving, or vice versa, should
be not more than 12 symbol periods.
•Energy Detection (ED) within the current channel
It is an estimate of the received signal power within the bandwidth of an
IEEE 802.15.4 channel. No attempt is made to identify or decode signals
on the channel in this procedure. The energy detection time shall be equal
to 8 symbol periods. The result from energy detection can be used by a
network layer as part of a channel selection algorithm, or for the purpose of
clear channel assessment (CCA) (alone or combined with carrier sense).
•Link Quality Indication (LQI) for received packets
Link quality indication measurement is performed for each received
packet. The PHY layer uses receiver energy detection (ED), a signal-tonoise ratio, or a combination of these to measure the strength and the
quality of a link from which a packet is received. However, the use of LQI
result by the network or application layers is not specified in the standard.
• Clear Channel Assessment (CCA) for Carrier Sense Multiple Access
with Collision Avoidance (CSMA-CA)
The PHY layer is required to perform CCA using energy detection,
carrier sense, or a combination of these two. In energy detection mode, the
medium is considered busy if any energy above a predefined energy
threshold is detected. In carrier sense mode, the medium is considered busy
if a signal with the modulation and spreading characteristics of IEEE
802.15.4 is detected. And in the combined mode, both conditions
aforementioned need to be met in order to conclude that the medium is
busy.
•Channel frequency selection
Wireless links under 802.15.4 can operate in 27 different channels (but a
specific network can choose to support part of the channels). Hence the
PHY layer should be able to tune its transceiver into a certain channel upon
receiving the request from MAC sublayer.
•Data transmission and reception
This is the essential task of the PHY layer. Modulation and spreading
techniques are used in this part. The 2.4 GHz PHY employs a 16-ary quasiorthogonal modulation technique, in which each four information bits are
mapped into a 32-chip pseudo-random noise (PN) sequence. The PN
sequences for successive data symbols are concatenated and modulated onto
the carrier using offset quadrature phase shift 3 keying (O-QPSK). The
868/915 MHz PHY employs direct sequence spread spectrum (DSSS) with
binary phase shift keying (BPSK) used for chip modulation and differential
encoding used for data symbol encoding. Each data symbol is mapped into a
15-chip PN sequence and the concatenated PN sequences are then modulated
onto the carrier using BPSK with raised cosine pulse shaping.
Features and Assumptions
Implemented Features
•800, 900, and 2400 MHz multiple frequency bands support.
•Multiple combinations of modulation schemes and spread spectrum
support.
•BER based reception quality estimation.
•Energy detection.
•Link quality indication.
•Clear channel assessment
Omitted Features
•Multiple interface support
Assumptions and Limitations
•PHY layer supports only a single channel
Supplemental Information
None.
ZigBee MAC
The QualNet ZigBee MAC is based on the IEEE 802.15.4-2006 standard
The MAC sublayer of 802.15.4 defines how the medium should be accessed
by devices participating in a WPAN. It provides two types of services: MAC
data service through MAC Common Part Sublayer (MCPS) and MAC
management service through MAC sub-Layer Management Entity (MLME).
The main features of a MAC sublayer are beacon management, channel
access, Guaranteed Time Slot (GTS) management, frame validation,
acknowledged frame delivery, association and disassociation, and device
security. The MAC layer provides an interface between the Service Specific
Convergence Sublayer (SSCS) and the PHY layer. Like the PHY layer, the
MAC layer also provides two services, namely, the MAC data service and
the MAC management service
Generating network beacons if the device is a coordinator
A coordinator can determine whether to work in a beacon enabled mode,
in which a superframe structure is used. The superframe is bounded by
network beacons and divided into slots of equal size. By default, the
number of slots is 16. A coordinator sends out beacons periodically to
synchronize the attached devices and for other purposes. A Full Function
Device (FFD), that is not the PAN coordinator should begin transmitting
beacon frames only when it has successfully associated with a PAN.
The Superframe is divided into active and inactive periods. Active period
is further divided into Contention Access Period (CAP) and Contention
Free Period (CFP). Any device must use CSMA/CA to communicate
during CAP. Guaranteed Time Slot (GTS) mechanism is used for CFP.
During the inactive period, the coordinator does not interact with the
network and goes to power saving mode.
•Synchronizing to the beacons
A device attached to a coordinator, operating in a beacon enabled mode,
can track the beacons to synchronize with the coordinator. This
synchronization is important for data polling, energy saving, and detection
of orphans.
Upper layer may direct MAC to keep a track of the beacons for which the
device will have to listen to every beacon sent by the coordinator to
maintain synchronization.
•Supporting Personal Area Network (PAN) association and
disassociation
To support self configuration, 802.15.4 embeds association and
disassociation functions in its MAC layer. This not only enables a star to be
setup automatically, but also allows for the creation of a self-configuring,
peer-to-peer network.
A coordinator may indicate presence of a PAN by sending periodic
beacons. The devices wishing to attach to the PAN listen to these beacons
to extract necessary information to connect to the PAN. The device can
associate to a PAN after performing a scan which gives the list of available
PAN ids to upper layer (SSCS).
An unassociated device sends an association request to the selected
PAN's coordinator. The PAN coordinator sends back a response depending
on availability of resources, using indirect transmission.
Disassociation can be initiated either by the PAN coordinator or the device
itself. Disassociation is always considered successful
Features and Assumptions
Implemented Features
•Generating network beacons if the device is a coordinator
•Synchronizing to network beacons
•Supporting PAN association and disassociation
•Employing the CSMA-CA mechanism for channel access
•Direct and indirect data transmission
•Handling and maintaining the Guranteed Time Slot (GTS) mechanism
•Providing a reliable link between two peer MAC entities
•SSCS features, i.e., starting/stopping devices
•Data acknowledgement
Omitted Features
•Security
•Multiple interface support
•Starting and stopping beacon
•Disassociation mechanism
Assumptions and Limitations
•AODV must be used as the routing protocol
•The GTS mechanism works only if ZigBee Application is used as the
Application Layer model.
ZigBee Application
The ZigBee Application generates traffic at a constant rate by transmitting
packets (also called “items”) of a fixed size at a fixed rate. It is generally
used to provide background traffic in a sensor network where devises use the
Guaranteed Time Slot (GTS) mechanism for data transmission.
Features and Assumptions
This section describes the implemented features, omitted features,
assumptions and limitations of the ZigBee Application model.
Implemented Features
•Transmission of packets of a fixed size with a constant inter-packet time.
Omitted Features
None.
Assumptions and Limitations
•For the GTS feature to work, the value of PRECEDENCE should be higher
than the value configured for the MAC parameter MAC-802.15.4-GTSTRIGGER-PRECEDENCE The ZigBee Application can be used to simulate
applications for which the end-systems require predictable response time and
a static amount of bandwidth is continuously available for the life-time of the
connection.
CHAPTER 5
ARCHITECTURE OF THE QUALNET
QualNet is a network simulator that mimics the behavior of a real network. A
network simulation is a costeffective method for developing the early stages
of network centric systems. Users can evaluate the basic behavior of a
network and test combinations of network features that are likely to work.
QualNet provides a comprehensive environment for designing protocols,
creating and animating network scenarios, and analyzing their performance.
II. METHODOLOGY
Fig.2 represents the processes carried out in produce a
performance output before the WSN model can analyze. Three
major process involved in analyzing the performance of
WSN are, creating a scenario model, simulating and analysis,
as shown in Fig.3. All these processes were done by the
QualNet Developer Graphical User Interface (GUI). The
QualNet Developer GUI consists of Scenario Designer,
Animator and Analyzer.
A Scenario Designer is a network design tool to create the
WSN model on the canvas which allows the creation of a
scenario model using components such as devices, links,
applications and network components. All elements in the
scenario such as mobility, radio type, energy model, battery
model parameters, and network, transport and application
layer protocols can be configured.
An Animator offers an in-depth visualization and analysis
of the scenario designed in the Scenario Designer. While
simulation is running, we can see packets being animated at
various layers, flow through the network. We can also speed
up or slow down the speed of the simulation to clearly observe
and analyze the network scenario.
Once the simulation has been done, the graphical metrics
results collected during simulation of a network scenario and
the results can be view in term of bar chart or histogram using
the Analyzer
QualNet is composed of the following tools:
QualNet Architect — A graphical experiment design and visualization
tool. Architect has two modes: Design mode, for designing experiments, and
Visualize mode, for running and visualizing experiments.
QualNet Analyzer — A graphical statistics analyzing tool
QualNet Packet Tracer — A graphical tool to display and analyze packet
traces.
QualNet File Editor — A text editing tool
QualNet
Command Line Interface — Command line access to the simulator.
QualNet Features and Benefits
QualNet is a comprehensive suite of tools for modeling large wired and
wireless networks. It uses simulation to predict the behavior and performance
of networks to improve their design, operation and management.
QualNet enables users to:
•Design new protocol models.
•Optimize new and existing models.
•Design large wired and wireless networks using pre-configured or userdesigned models.
•Analyze the performance of networks and perform what-if analysis to
optimize them.
The key features of QualNet that enable creating a virtual network
environment are:
•Speed
QualNet can support real-time speed to enable software-in-the-loop,
network emulation, and hardware-in-the-loop modeling. Faster speed
enables model developers and network designers to run multiple “what-if”
analyses by varying model, network, and traffic parameters in a short time.
•Scalability
QualNet can model thousands of nodes by taking advantage of the latest
hardware and parallel computing techniques. QualNet can run on cluster,
multi-core, and multi-processor systems to model large networks with high
fidelity.
•Model Fidelity
QualNet uses highly detailed standards-based implementation of protocol
models. It also includes advanced models for the wireless environment to
enable more accurate modeling of real-world networks.
•Portability
QualNet and its library of models run on a vast array of platforms,
including Windows and Linux operating systems, distributed and cluster
parallel architectures, and both 32- and 64-bit computing platforms. Users
can now develop a protocol model or design a network in QualNet on their
desktop or laptop Windows computer and then transfer it to a powerful
multi-processor Linux server to run capacity, performance, and scalability
analyses.
•Extensibility
QualNet can connect to other hardware and software applications, such as
OTB, real networks, and third party visualization software, to greatly
enhancing the value of the network model.
QualNet Graphical User Interface (GUI)
QualNet GUI consists of Architect, Analyzer, Packet Tracer, and File Editor.
•Architect is a network design and visualization tool. It has two modes:
Design mode and Visualize mode.
In Design mode, you can set up terrain, network connections, subnets,
mobility patterns of wireless users, and other functional parameters of
network nodes. You can create network models by using intuitive, click and
drag operations. You can also customize the protocol stack of any of the
nodes. You can also specify the application layer traffic and services that
run on the network. Design mode of Architect is described in Chapter 3.
In Visualize mode, you can perform in-depth visualization and analysis of
a network scenario designed in Design mode. As simulations are running,
users can watch packets at various layers flow through the network and
view dynamic graphs of critical performance metrics. Real-time statistics
are also an option, where you can view dynamic graphs while a network
scenario simulation is running. Visualize mode of Architect is described in
Chapter 5.
You can also assign jobs to run in batch mode on a faster server and view
the animated data later. You can perform “what-if” analysis by setting a
range of values for a particular protocol parameter and comparing the
network performance results for each of them.
•Analyzer is a statistical graphing tool that displays hundreds of metrics
collected during simulation of a network scenario. You can choose to see
pre-designed reports or customize graphs with their own statistics. Multiexperiment reports are also available. All statistics are exportable to
spreadsheets in CSV format. Analyzer is described in Chapter 6.
•Packet Tracer provides a visual representation of packet trace files
generated during the simulation of a network scenario. Trace files are text
files in XML format that contain information about packets as they move
up and down the protocol stack. Packet Tracer is described in Chapter 7.
•File Editor is a text editing tool that displays the contents of the selected file
in text format and allows the user to edit files. File Editor is described in
CHAPTER 6
STUDIED SCENARIO
The above figure depicts the scenario of Zigbee network and
CHAPTER 7
RESULTS OBSERVED
analysis of Wireless Sensor Network (WSN) used in the
high-end applications such as weapons sensor ship,
biomedical applications, habitat sensing and seismic
monitoring. Recently WSN also focuses on national
security applications and consumer applications. This
project shall demonstrate the performance of WSN
models, which are created and simulated using QualNet
Developer software simulator. Several sensor nodes were
uniformly deployed in the networks to create sensing
phenomena. The simulation results recorded were the
amount of data packets sent and received by each node,
the throughput and the delay. All these graphical
simulation results from several WSN models will be
compared and analyzed separately. Therefore, the
important factors and issues pertaining to the WSN
performance will also be determined and describe briefly .
CHAPTER 1
INTRODUCTION
Wireless Sensor Network (WSN) are a trend of the last few
years due to the advances made in wireless communication,
information technologies and electronics filed. The
development of low-cost, low-power, a multifunctional sensor
has received increasing attention from various industries [1].
WSN is a wireless network composed of autonomous and
compact devices called sensor nodes or motes. A sensor
network is designed to detect phenomena, collect and process
data and transmit sensed information to users. Sensor nodes or
motes in WSNs, are small sized and are capable of sensing,
gathering and processing data while communicating with other
connected nodes in the network, via radio frequency (RF)
channel.
CHAPTER 2
ARCHITECTURE OF SENSOR NODE
The system architecture of a sensor node is as shown below.A sensor node
consists of a radio transceiver or optical as the communication unit, sensor as
the sensing unit, a microcontroller for the processing unit and battery as the
power unit.The hardware device in the sensing unit may consist up to several
sensors. This device produces measurable response to change which acts as
an interface between motes to the environment. Measurable changes are,
vibration, temperature,sound, motion, pollutants or pressure in environmental
conditions.
The processing unit is responsible for the collecting and
processing of the captured signal from the sensor unit. These
signals are then transmitted to the network. It determines both
energy consumption as well as computational capabilities of
the sensor node.
The power unit consisting of battery supplies power to the
sensor node. It is important to choose the battery type since
durability will affect the design of sensor node.
The Wireless Sensor Networks are being used in many
ways. Traditionally, it has been used in the high-end
application such as radiation and nuclear-threat detection
systems, weapons sensors for ships, biomedical applications,
habitat sensing and seismic monitoring. Recently, Wireless
Sensor Networks are focusing on national security
applications and consumer applications such as [3]:
1. Military applications
Monitoring, tracking and surveillance of borders
Nuclear, biological and chemical attack detection
Battle damage assessment
2. Environmental applications
Flood and oceans detection
Forest fire detection
3. Health applications
Drug administration
Remote monitoring of physiological data
Tracking and monitoring doctors and patients inside a
hospital
4. Home applications
Automated meter reading
Home automation
Instrumented environment
5. Commercial applications
Monitoring vibration that could damage the buildings
structures
Monitoring traffic flow and road condition
Vehicle tracking and detection
CHAPTER 3
PROTOCOLS USED FOR WIRELESS SENSOR NETWORKS
This necessity for energy efficient operation
of a WSN has prompted the development of new protocols in
all layers of the communication stack.
protocols like
Bellman-Ford, Ad-Hoc on-Demand Routing (AODV),
Dynamic Source Routing (DSR), Dynamic MANET
On-demand Protocol (DYMO)
Taxonomy of Protocols and detailed
description is given below:
In uniform protocols there is no hierarchy in network, all
nodes send and respond to routing control messages at the
same manner.
In non-uniform protocols there is an effort to reduce the
control traffic burden by separating nodes in dealing with
routing information. Non-uniform protocols fall into two
categories: protocols in which each node focuses routing
activity on a subset of its neighbors and protocols in which the
network is topologically partitioned [8].
Topology-based protocols use the principle that every node
in a network maintains large-scale topology information. This
principle is just the same as in link-state protocols.
Destination-based protocols do not maintain large-scale
topology information. They only may maintain topology
information needed to know the nearest neighbors.
Proactive protocols, which are also known as table-driven
protocols, maintain all the time routing information for all
known destinations at every source [9].
In on-demand i.e. in reactive protocols the route is only
calculated on demand basis. That means that there is no
unnecessary routing information maintained.
Type of Cast
Another type of classification can be done via, type caste
property. i.e, whether they use
· Unicast
· Geo-cast
· Multicast
· Unicast: Unicast forwarding means one to one
communication. i.e, one source transmits data packets to
a single destination.
· Geo-cast: The main aim of Geo-cast is to deliver the data
to a group of nodes situated inside a specified
geographical area [10].
· Multicast: Multicast means one to many i.e, when a node
needs to send same data to multiple destinations.
Bellman-Ford Routing Protocol
Bellman-Ford Routing Algorithm, also known as
Ford-Fulkerson Algorithm, is used as a distance vector
routing protocol. Routers that use this algorithm have to
maintain the distance tables, which tell the distances and
shortest path to sending packets to each node in the network.
The information in the distance table is always updated by
exchanging information with the neighbouring nodes.
Destination Based Routing:
Ad-Hoc on-Demand Routing
AODV is a modification of the DSDV algorithm. When a
source node desires to establish a communication session, it
initiates a path-discovery process to locate the other node.
The source node broadcasts a RREQ packet with its IP
address, Broadcast ID (BrID), and the sequence number of
the source and destination [11]. While, the BrID and the IP
address is used to uniquely identify each request, the sequence
numbers are used to determine the timeliness of each packet .
CHAPTER 4
Sensor Networks
ZigBee is a specification for a suite of high level communication protocols
using small, low-power digital radios based on the IEEE 802.15.4 standard
for Wireless Personal Area Networks (WPANs). ZigBee is targeted at RF
applications that require a low data rate, long battery life, and secure
networking. These networks are aimed at automation, remote control, and
Wireless Sensor Network (WSN) applications. The IEEE 802.15.4 standard
defines the physical layer (PHY) and Medium Access Control sublayer
(MAC) specifications as the wireless communication standard for low-power
consumption, Low-Rate WPAN (LR-WPANs).
Layers in Sensor Networks
1.Physical Layer
2.MAC Layer
3.Application Layer
ZigBee PHY
The QualNet ZigBee PHY is based on the IEEE 802.15.4-2006 standard
The PHY layer provides an interface between the MAC layer and the
physical radio channel. It provides two services, accessed through two
service access points (SAPs). These are the PHY data service and the PHY
management service. The PHY layer is responsible for the following tasks:
•Activation and deactivation of the radio transceiver
Turn the radio transceiver into one of the three states,(i.e., transmitting,
receiving, or off (sleeping)) according to the request from MAC sublayer.
The turnaround time from transmitting to receiving, or vice versa, should
be not more than 12 symbol periods.
•Energy Detection (ED) within the current channel
It is an estimate of the received signal power within the bandwidth of an
IEEE 802.15.4 channel. No attempt is made to identify or decode signals
on the channel in this procedure. The energy detection time shall be equal
to 8 symbol periods. The result from energy detection can be used by a
network layer as part of a channel selection algorithm, or for the purpose of
clear channel assessment (CCA) (alone or combined with carrier sense).
•Link Quality Indication (LQI) for received packets
Link quality indication measurement is performed for each received
packet. The PHY layer uses receiver energy detection (ED), a signal-tonoise ratio, or a combination of these to measure the strength and the
quality of a link from which a packet is received. However, the use of LQI
result by the network or application layers is not specified in the standard.
• Clear Channel Assessment (CCA) for Carrier Sense Multiple Access
with Collision Avoidance (CSMA-CA)
The PHY layer is required to perform CCA using energy detection,
carrier sense, or a combination of these two. In energy detection mode, the
medium is considered busy if any energy above a predefined energy
threshold is detected. In carrier sense mode, the medium is considered busy
if a signal with the modulation and spreading characteristics of IEEE
802.15.4 is detected. And in the combined mode, both conditions
aforementioned need to be met in order to conclude that the medium is
busy.
•Channel frequency selection
Wireless links under 802.15.4 can operate in 27 different channels (but a
specific network can choose to support part of the channels). Hence the
PHY layer should be able to tune its transceiver into a certain channel upon
receiving the request from MAC sublayer.
•Data transmission and reception
This is the essential task of the PHY layer. Modulation and spreading
techniques are used in this part. The 2.4 GHz PHY employs a 16-ary quasiorthogonal modulation technique, in which each four information bits are
mapped into a 32-chip pseudo-random noise (PN) sequence. The PN
sequences for successive data symbols are concatenated and modulated onto
the carrier using offset quadrature phase shift 3 keying (O-QPSK). The
868/915 MHz PHY employs direct sequence spread spectrum (DSSS) with
binary phase shift keying (BPSK) used for chip modulation and differential
encoding used for data symbol encoding. Each data symbol is mapped into a
15-chip PN sequence and the concatenated PN sequences are then modulated
onto the carrier using BPSK with raised cosine pulse shaping.
Features and Assumptions
Implemented Features
•800, 900, and 2400 MHz multiple frequency bands support.
•Multiple combinations of modulation schemes and spread spectrum
support.
•BER based reception quality estimation.
•Energy detection.
•Link quality indication.
•Clear channel assessment
Omitted Features
•Multiple interface support
Assumptions and Limitations
•PHY layer supports only a single channel
Supplemental Information
None.
ZigBee MAC
The QualNet ZigBee MAC is based on the IEEE 802.15.4-2006 standard
The MAC sublayer of 802.15.4 defines how the medium should be accessed
by devices participating in a WPAN. It provides two types of services: MAC
data service through MAC Common Part Sublayer (MCPS) and MAC
management service through MAC sub-Layer Management Entity (MLME).
The main features of a MAC sublayer are beacon management, channel
access, Guaranteed Time Slot (GTS) management, frame validation,
acknowledged frame delivery, association and disassociation, and device
security. The MAC layer provides an interface between the Service Specific
Convergence Sublayer (SSCS) and the PHY layer. Like the PHY layer, the
MAC layer also provides two services, namely, the MAC data service and
the MAC management service
Generating network beacons if the device is a coordinator
A coordinator can determine whether to work in a beacon enabled mode,
in which a superframe structure is used. The superframe is bounded by
network beacons and divided into slots of equal size. By default, the
number of slots is 16. A coordinator sends out beacons periodically to
synchronize the attached devices and for other purposes. A Full Function
Device (FFD), that is not the PAN coordinator should begin transmitting
beacon frames only when it has successfully associated with a PAN.
The Superframe is divided into active and inactive periods. Active period
is further divided into Contention Access Period (CAP) and Contention
Free Period (CFP). Any device must use CSMA/CA to communicate
during CAP. Guaranteed Time Slot (GTS) mechanism is used for CFP.
During the inactive period, the coordinator does not interact with the
network and goes to power saving mode.
•Synchronizing to the beacons
A device attached to a coordinator, operating in a beacon enabled mode,
can track the beacons to synchronize with the coordinator. This
synchronization is important for data polling, energy saving, and detection
of orphans.
Upper layer may direct MAC to keep a track of the beacons for which the
device will have to listen to every beacon sent by the coordinator to
maintain synchronization.
•Supporting Personal Area Network (PAN) association and
disassociation
To support self configuration, 802.15.4 embeds association and
disassociation functions in its MAC layer. This not only enables a star to be
setup automatically, but also allows for the creation of a self-configuring,
peer-to-peer network.
A coordinator may indicate presence of a PAN by sending periodic
beacons. The devices wishing to attach to the PAN listen to these beacons
to extract necessary information to connect to the PAN. The device can
associate to a PAN after performing a scan which gives the list of available
PAN ids to upper layer (SSCS).
An unassociated device sends an association request to the selected
PAN's coordinator. The PAN coordinator sends back a response depending
on availability of resources, using indirect transmission.
Disassociation can be initiated either by the PAN coordinator or the device
itself. Disassociation is always considered successful
Features and Assumptions
Implemented Features
•Generating network beacons if the device is a coordinator
•Synchronizing to network beacons
•Supporting PAN association and disassociation
•Employing the CSMA-CA mechanism for channel access
•Direct and indirect data transmission
•Handling and maintaining the Guranteed Time Slot (GTS) mechanism
•Providing a reliable link between two peer MAC entities
•SSCS features, i.e., starting/stopping devices
•Data acknowledgement
Omitted Features
•Security
•Multiple interface support
•Starting and stopping beacon
•Disassociation mechanism
Assumptions and Limitations
•AODV must be used as the routing protocol
•The GTS mechanism works only if ZigBee Application is used as the
Application Layer model.
ZigBee Application
The ZigBee Application generates traffic at a constant rate by transmitting
packets (also called “items”) of a fixed size at a fixed rate. It is generally
used to provide background traffic in a sensor network where devises use the
Guaranteed Time Slot (GTS) mechanism for data transmission.
Features and Assumptions
This section describes the implemented features, omitted features,
assumptions and limitations of the ZigBee Application model.
Implemented Features
•Transmission of packets of a fixed size with a constant inter-packet time.
Omitted Features
None.
Assumptions and Limitations
•For the GTS feature to work, the value of PRECEDENCE should be higher
than the value configured for the MAC parameter MAC-802.15.4-GTSTRIGGER-PRECEDENCE The ZigBee Application can be used to simulate
applications for which the end-systems require predictable response time and
a static amount of bandwidth is continuously available for the life-time of the
connection.
CHAPTER 5
ARCHITECTURE OF THE QUALNET
QualNet is a network simulator that mimics the behavior of a real network. A
network simulation is a costeffective method for developing the early stages
of network centric systems. Users can evaluate the basic behavior of a
network and test combinations of network features that are likely to work.
QualNet provides a comprehensive environment for designing protocols,
creating and animating network scenarios, and analyzing their performance.
II. METHODOLOGY
Fig.2 represents the processes carried out in produce a
performance output before the WSN model can analyze. Three
major process involved in analyzing the performance of
WSN are, creating a scenario model, simulating and analysis,
as shown in Fig.3. All these processes were done by the
QualNet Developer Graphical User Interface (GUI). The
QualNet Developer GUI consists of Scenario Designer,
Animator and Analyzer.
A Scenario Designer is a network design tool to create the
WSN model on the canvas which allows the creation of a
scenario model using components such as devices, links,
applications and network components. All elements in the
scenario such as mobility, radio type, energy model, battery
model parameters, and network, transport and application
layer protocols can be configured.
An Animator offers an in-depth visualization and analysis
of the scenario designed in the Scenario Designer. While
simulation is running, we can see packets being animated at
various layers, flow through the network. We can also speed
up or slow down the speed of the simulation to clearly observe
and analyze the network scenario.
Once the simulation has been done, the graphical metrics
results collected during simulation of a network scenario and
the results can be view in term of bar chart or histogram using
the Analyzer
QualNet is composed of the following tools:
QualNet Architect — A graphical experiment design and visualization
tool. Architect has two modes: Design mode, for designing experiments, and
Visualize mode, for running and visualizing experiments.
QualNet Analyzer — A graphical statistics analyzing tool
QualNet Packet Tracer — A graphical tool to display and analyze packet
traces.
QualNet File Editor — A text editing tool
QualNet
Command Line Interface — Command line access to the simulator.
QualNet Features and Benefits
QualNet is a comprehensive suite of tools for modeling large wired and
wireless networks. It uses simulation to predict the behavior and performance
of networks to improve their design, operation and management.
QualNet enables users to:
•Design new protocol models.
•Optimize new and existing models.
•Design large wired and wireless networks using pre-configured or userdesigned models.
•Analyze the performance of networks and perform what-if analysis to
optimize them.
The key features of QualNet that enable creating a virtual network
environment are:
•Speed
QualNet can support real-time speed to enable software-in-the-loop,
network emulation, and hardware-in-the-loop modeling. Faster speed
enables model developers and network designers to run multiple “what-if”
analyses by varying model, network, and traffic parameters in a short time.
•Scalability
QualNet can model thousands of nodes by taking advantage of the latest
hardware and parallel computing techniques. QualNet can run on cluster,
multi-core, and multi-processor systems to model large networks with high
fidelity.
•Model Fidelity
QualNet uses highly detailed standards-based implementation of protocol
models. It also includes advanced models for the wireless environment to
enable more accurate modeling of real-world networks.
•Portability
QualNet and its library of models run on a vast array of platforms,
including Windows and Linux operating systems, distributed and cluster
parallel architectures, and both 32- and 64-bit computing platforms. Users
can now develop a protocol model or design a network in QualNet on their
desktop or laptop Windows computer and then transfer it to a powerful
multi-processor Linux server to run capacity, performance, and scalability
analyses.
•Extensibility
QualNet can connect to other hardware and software applications, such as
OTB, real networks, and third party visualization software, to greatly
enhancing the value of the network model.
QualNet Graphical User Interface (GUI)
QualNet GUI consists of Architect, Analyzer, Packet Tracer, and File Editor.
•Architect is a network design and visualization tool. It has two modes:
Design mode and Visualize mode.
In Design mode, you can set up terrain, network connections, subnets,
mobility patterns of wireless users, and other functional parameters of
network nodes. You can create network models by using intuitive, click and
drag operations. You can also customize the protocol stack of any of the
nodes. You can also specify the application layer traffic and services that
run on the network. Design mode of Architect is described in Chapter 3.
In Visualize mode, you can perform in-depth visualization and analysis of
a network scenario designed in Design mode. As simulations are running,
users can watch packets at various layers flow through the network and
view dynamic graphs of critical performance metrics. Real-time statistics
are also an option, where you can view dynamic graphs while a network
scenario simulation is running. Visualize mode of Architect is described in
Chapter 5.
You can also assign jobs to run in batch mode on a faster server and view
the animated data later. You can perform “what-if” analysis by setting a
range of values for a particular protocol parameter and comparing the
network performance results for each of them.
•Analyzer is a statistical graphing tool that displays hundreds of metrics
collected during simulation of a network scenario. You can choose to see
pre-designed reports or customize graphs with their own statistics. Multiexperiment reports are also available. All statistics are exportable to
spreadsheets in CSV format. Analyzer is described in Chapter 6.
•Packet Tracer provides a visual representation of packet trace files
generated during the simulation of a network scenario. Trace files are text
files in XML format that contain information about packets as they move
up and down the protocol stack. Packet Tracer is described in Chapter 7.
•File Editor is a text editing tool that displays the contents of the selected file
in text format and allows the user to edit files. File Editor is described in
CHAPTER 6
STUDIED SCENARIO
The above figure depicts the scenario of Zigbee network and
CHAPTER 7
RESULTS OBSERVED
