OPNET Technologies
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© 2001 OPNET Technologies
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Rochester Institute of Technology, Lab for Applied Computing:
Sponsoring Professors:
Dr. Nirmala Shenoy - Department ofInformation Technology
Prof. Bruce Hartpence - Department ofInformation Technology
Students:
Nithya Ganesh
Dinika Joshi
Punita Misra
Neha Shidore
Viswanath Prasad
John Sheftic
Yukte Oberoi
Project 1 Seamless Handoff and Roaming in
Next Generation Wireless Networks
This project will conduct initial
research and study the requirements for roaming strategies and propose
a hierarchical control architecture for seamless roaming and handoff in
next generation wireless networks. It should be scalable, secure and provide
for support of quality of service. For the solution to be easily acceptable
and deployable its effect on the infrastructure, mobility mechanisms and
protocols of the already deployed wireless networks should be minimal.
The architecture preferably should harness their capabilities. The ongoing
work among researchers and standards bodies in this area, and the preference
of vendors should be a major consideration for the solutions. The architecture
should be open-ended and adaptable to any wireless technology or core
network. The work is restricted to wireless local area networks (WLAN)
and third generation (3G) cellular networks like 3G Universal Mobile Telephone
Systems (UMTS).
Project 2 Framework for Seamless Roaming,
Handoff and Qos Mapping in Next Generation Networks
Various
attempts are being made to integrate the widely deployed disparate terrestrial
wireless networks in order to provide global roaming and seamless handoff
with continued and acceptable Quality of Service (QoS) guarantees. Though
challenging, our proposed framework targets an easily deployable solution
with minimal changes to existing mobility mechanisms within the wireless
networks.
The investigators have proposed an open-ended framework, which will harness
existing mobility mechanisms and protocols in current wireless networks
and can be adapted to new and emerging wireless technologies. IPv6 has
been chosen as the core network technology, though the framework can be
overlaid over other core networks with minimal changes. The mobility features
proposed by MobileIP will be used within the core network. Mechanisms
for graceful QoS transitions while crossing different wireless networks
are supported.
The framework, which is distributed and hierarchical, comprises of Interface
Control Nodes (ICNs) distributed across the core and the wireless networks.
The ICN functions can be collocated with some existing control nodes within
the core network and the wireless network to ease deployment. The ICNs
will have the protocols and functions to effect seamless roaming and handoff
and provide Quality of Service (QoS) negotiation and mapping to facilitate
a graceful QoS transitions during inter-network movement. The component
protocols residing at the ICNs in the framework will communicate vertically
with each other and horizontally with the corresponding mobility protocols
of the wireless networks to effect a seamless handoff. The Opnet simulation
tool and test-beds will be used for conducting investigative studies on
this framework.
Nithya Ganesh
Phase I
Cellular
to cellular roaming scenario
The aim
of the project is to provide seamless connectivity to the future mobile
user traversing across heterogeneous cellular networks by designing a
framework that facilitates a handoff between any two cellular networks.
This project involves relieving some challenges that mobile users face
when traveling across cellular networks that employ different technologies.
One of the main goals of this project was to develop a working base model
on which the Global Mobility Management
Framework can be implemented and tested. This project focuses on the
simulation approach to testing the framework. The work began with a basic
GPRS model, as the initial focus is in data connections, obtained from
the “contributed models” section of the OPNET web site. This base model
was changed considerably to meet the needs of our research on user mobility
and mobility management. At this point, the data portion of two 3G cellular
networks (data part) has been modeled. One of the main goals when traversing
between the networks, as a mobile user, is to ensure that loss of data
or loss of connectivity does not occur as a result of the handoff. For
this reason, along with the handoff mechanism, a data redirection process
for the active session has also been modeled. As part of the handoff process,
context information of the mobile user is also passed on to the new network.
Currently, the model is being enhanced to include delays which will be
more representative of a realistic environment.
Phase II
A mobile station moving from a cellular
network to another cellular network during an active data session.
As of now a base model has been completed. The base model
consists of two cellular networks with GPRS overlay network with an actively
roaming mobile user. As mentioned before, a handoff mechanism as well
as a redirection process has been designed for successful transfer of
the mobile user to the new cellular network. Once these mechanisms were
implemented, delays were incorporated into the model. Specifically, the
delays implemented were processing, database, store/retrieve, and channel
allocation delays. These delays were placed at pertinent nodes in the
model to achieve a more realistic scenario. Once the delays were implemented,
validation of the model was performed. Following the validation, the model
was tested for several scenarios. The scenarios were based on varying
the processing and database job arrival rates at the various nodes in
the networks. The effect of the varying arrival rates was observed on
the two overall delays that were being studied. The two overall delays
of interest are the delays encountered by the mobile user as a result
of handoff and redirection of packets process. The base model is intended
as a stepping stone to further research on more efficient handoff and
redirection mechanisms between the cellular networks. With that in mind,
the base model has been modified to create two other models namely, early
queue release and bicasting models. The early queue release model is a
variation specifically at the redirection process allowing packets destined
for the new network to be transferred with lesser delays than the base
model. The bicasting model is a variation that uses an IP tethering point
to act as a crossover point and transmit identical packets to both cellular
networks during the handoff process enabling the mobile user to receive
data packets as soon as a handoff has been accomplished. These models
will be validated and tested to obtain results.
Dinika Joshi
Phase I
Cellular to WLAN and
WLAN to Cellular Roaming
The focus of this part of the project was to study seamless
mobility issues and protocols while the mobile node is moving from a cellular
network into a wireless LAN hotspot from WLAN to WLAN and from WLAN to
Cellular networks
The
cellular to cellular mobility model in Opnet was extended by adding a
WLAN module to it. The mobile station was made to move along a predefined
trajectory from the cellular network into the WLAN during an active data
session ( initial studies are restricted to data connections). The main
goal was to see that the mobile station does not lose any packets when
switching between the two heterogeneous networks.
In
order to make this possible, the mobile station was provided with two
profiles. One of the profiles is specific to the cellular network with
the Quality of Service (QoS) and the Packet Data Protocol (PDP) information.
The other profile, specific to the WLAN, has a list of AP IDs and WEP
keys of the access points that the mobile station can communicate with.
The profile also consists of the home network ID for the mobile station.
The HLR in the home network maintains a profile for the mobile station
and updates it as the mobile station connects to various networks for
information about its current network. The HLR also does the profile transfers
to the new network that the mobile station is connecting to. The HLR/VLR
will perform the context transfer. This information is provided so that
the new network is aware of the privileges that the mobile station is
entitled to have.
Basically when
the mobile station moves from the cellular network into the WLAN, it will
start receiving redirected data packets from the previous cellular network
only after it associates with the access point (AP) in the WLAN. After
all the redirected packets are received from the AP by the mobile station,
it will start receiving data packets from the Internet directly via its
gateway. With such a handoff mechanism, it can be insured that the mobile
station has not lost any data packets in spite of his transition from
a cellular network into a WLAN hotspot.
Phase II
Roaming from Cellular
to WLAN
The packet sequencing in a cellular
network is very different from that in the WLAN. In a cellular network,
the mobile station (MS) will first attach to the network, then activate,
and once activated the MS will start the data session. At the end of a
data session or when the MS wants to end the data session, the MS first
deactivates with the network and then detaches from the network. In the
WLAN, the MS first authenticates with the Access Point (AP) and then associates
with the AP. Once the MS is associated with the AP, it starts its data
session with the WLAN at any time. However, this authentication of the
MS with the AP is a layer 2 authentication. When we are considering the
roaming of the MS from the cellular network into the WLAN, it is important
to consider user authentication of the MS with the home network of the
MS. So the concept of HLR/VLR was introduced in the WLAN. A node acting
as a VLR was used in the WLAN into which the mobile node roamed. So, before
the MS is allowed to start a data session with the WLAN, the VLR in the
WLAN authenticates the MS with the home network of the MS. Also, it was
important to develop a multi-mode MS that can communicate with a cellular
network and a WLAN by switching frequencies.
Once the handoff and redirection
mechanisms were implemented, delays at the various nodes were introduced.
The delays implemented were:
- Process Delay – The time taken by node to decide what to do next
with the incoming packet. This delay is introduced in all the nodes
in the model.
- Database Delay – The time taken by the HLR to retrieve information
about a Mobile Station from its database. This delay is only introduced
in the HLR/VLR before sending the authentication reply for the MS.
This gives the effect of checking for information on the MS in the
database before sending the authentication reply.
- Total Delay (= Store Delay + Retrieve Delay) – To handle packet
redirection a set of queues were introduced at the various nodes which
handle the packet retransmission. The time taken by the nodes to store
and retrieve data packets from the queues during data redirection
process constitutes the total delay.
- Encapsulation Delay – The time taken by GGSN to encapsulate data
packets traveling from the cellular network into the WLAN through
the tunnel.
- Decapsulation Delay – The time taken by Gateway to retrieve the
original data packet from the encapsulated data packets received from
the GPRS network. through the tunnel
The M/G/1 queue formula was used to calculate the process, database
and the total delay.
The Encapsulation and Decapsulation delays were assumed
to have fixed values.
The two delays of interest for the mobility management studies are the:
- Handoff Delay – It is calculated from the time BTS sends Handoff
Request to SGSN to the time BTS gets Handoff Complete from MS.
- Redirection Delay – It is calculated from the time BTS queues first
data packet to the time MS receives first redirected packet.
The handoff delay and the data
redirection delay were calculated manually as well as through the simulation
results for validation purposes. For the validation, the actual simulation
time at every event in the handoff and redirection process was taken and
was compared to the manually estimated time according to the delays that
were incorporated in the model.
A number of scenarios with varying seed values were used to test the model.
In these scenarios, the loads at the various nodes were changed to give
the effect of the network being populated with multiple BTSs and MSs.
Neha Shidore
Phase III
Extend
the Opnet model – Cellular to Cellular roaming to study the handling of
voice calls during roaming and study new handoff
and redirection mechanism
- Extend the model developed by Nithya Ganesh to study the data redirection
and handoff performance using the Early Queue clearance and Bi casting
models for data connection
- Research papers and investigate novel handoff and redirection mechanism
for data and voice connections. This will be an ongoing activity.
To come up with new ideas based on this research study.
- Extend the base model to accommodate for voice calls.
- Implement new handoff mechanisms/protocols for voice calls
- To extract the specification for an efficient and transparent handoff
from the modeled schemes, which can be applicable to both voice and
data calls
- Interact with Punita to learn the QoS mapping and negotiations
and help Punita implement them in the models
Punita Misra
Phase III
Quality of service
mapping and negotiation mechanisms at the control points of the framework
- To study the Quality of service support in the Internet and IPv6
- To study QoS support in WLAN – to be done with John Sheftic
- To research papers in the area of Qos mapping and negotiation across
wireless networks and across core networks (Ipv6) and wireless networks.
This will be an ongoing activity. To come up with new ideas based
on this research study.
- Adopt the base-model developed by Nithya Ganesh and Dinika Joshi
and implement the Qos mapping and negotiations in the control points
which were used for handoff. To get the help from Neha Shidore and
Viswanath Prasad to clarify any model problems.
- Study the QoS performance and implement improvements based on research
paper study.
f. Extend the Qos mechanisms to the other models to be developed by
Neha Shidore and Viswanath Prasad i.e
i. Voice calls for the two models - cell-cell and cell-WLAN
ii. Other handoff mechanisms for the two models –do-
iii. WLAN-WLAN roaming cases
iv. WLAN to cellular roaming cases
- Extract the specification so that they can be transparently applied
over any roaming conditions
Viswanatha Prasad
Extend
the Opnet model – Cellular to WLAN roaming to study the handling of voice
calls during roaming, to study
WLAN to WLAN and WLAN to Cellular roaming
- Extend the model developed by Dinika Joshi, to accommodate for
voice calls
- Extend Dinika’s base model to accommodate for WLAN – WLAN roaming
and WLAN to cellular roaming
- Research papers and investigate novel handoff and redirection mechanism
for data and voice connections. This will be an ongoing activity.
To come up with new ideas based on this research study.
- Implement new handoff and redirection mechanisms based on research
study in the three roaming scenarios, cell-WLAN, WLAN -WLAN and WLAN-Cell.
Study the performance of handoff and redirection in each case
- In the scenarios involving WLAN, there is a necessity to develop
a new entity that can provide mobility services. A mobility server
has to be introduced in the model. To investigate this via research
and implement in the modeling
- Extract the specification so that they can be transparently applied
over any roaming conditions
- Handover the completed models to Punita to implement the QoS mechanisms.
Give her any assistance in this regard.
John Shefic
QoS mapping and negotiation
for WLAN to cellular (UMTS) roaming with IPv4 and IPv6 as the core network
On the MobileIPv4 test bed
- Study QoS offered by Cisco APs within one subnet, measure the QoS
in terms of user perceived Qos and in terms of delay, jitter, packet
loss and data rate.
a. For voice – conversational in UMTS
b. Video – streaming in UMTS
c. Data - ftp - interactive
d. Background – emails
The scenario of test should have all services accessing the AP at
the same time. The load offered by the different services should be
varied to see their effect on the Qos of the other services.
- Change the setup so that APs communicate across the core network
different IP subnets, with the routers set to handle Diffserv. Repeat
the experiments above
- Identify the Qos as specified for the classes in UMTS – ie. determine
the delays, bit rates jitter etc for each type of UMTS traffic. Check
the Qos as offered over the AP and IP networks.
- Read research papers related to determine how mapping an negotiations
can be carried out efficiently. Ongoing activity.
- Model the study in Opnet and determine the best mapping and acceptable
negotiations incase a particular Qos is not available.
- The Opnet models developed by Dinika and Viswanath can be used.
Viswanath can coordinate in this.
- Work with Punita Misra as she will be implementing the Qos in the
framework
Yukte Oberoi
Mobile IPv4 and MobileIPv6
in Opnet
- Study the operation of Mobile
IP and implement it in OPNET as close as possible to the testbed in
the LAC lab.
- Study the Process Models in
OPNET to implement Mobile IP.
- Create different scenarios
to study the global statistics like data dropped, delay, throughput
etc as we change the FTP Download Start Time.
- Create different scenarios
to study the global statistics like data dropped, delay, throughput
etc as we change the speed in which the Mobile Node travels across the
Home Network to the Foreign Network.
- Study the different mechanisms
in OPNET for QoS.
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