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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


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:

  1. 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.
  2. 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.
  3. 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.
  4. Encapsulation Delay – The time taken by GGSN to encapsulate data packets traveling from the cellular network into the WLAN through the tunnel.
  5. 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:

  1. Handoff Delay – It is calculated from the time BTS sends Handoff Request to SGSN to the time BTS gets Handoff Complete from MS.
  2. 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

  1. 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
  2. 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.
  3. Extend the base model to accommodate for voice calls.
  4. Implement new handoff mechanisms/protocols for voice calls
  5. To extract the specification for an efficient and transparent handoff from the modeled schemes, which can be applicable to both voice and data calls
  6. 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


  1. To study the Quality of service support in the Internet and IPv6
  2. To study QoS support in WLAN – to be done with John Sheftic
  3. 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.
  4. 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.
  5. 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
  6. 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


  1. Extend the model developed by Dinika Joshi, to accommodate for voice calls
  2. Extend Dinika’s base model to accommodate for WLAN – WLAN roaming and WLAN to cellular roaming
  3. 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.
  4. 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
  5. 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
  6. Extract the specification so that they can be transparently applied over any roaming conditions
  7. 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

  1. 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.
  2. 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
  3. 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.
  4. Read research papers related to determine how mapping an negotiations can be carried out efficiently. Ongoing activity.
  5. Model the study in Opnet and determine the best mapping and acceptable negotiations incase a particular Qos is not available.
  6. The Opnet models developed by Dinika and Viswanath can be used. Viswanath can coordinate in this.
  7. Work with Punita Misra as she will be implementing the Qos in the framework

Yukte Oberoi

Mobile IPv4 and MobileIPv6 in Opnet

  1. Study the operation of Mobile IP and implement it in OPNET as close as possible to the testbed in the LAC lab.
  2. Study the Process Models in OPNET to implement Mobile IP.
  3. Create different scenarios to study the global statistics like data dropped, delay, throughput etc as we change the FTP Download Start Time.
  4. 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.
  5. Study the different mechanisms in OPNET for QoS.