Project Title:
Wireless Internet Post Office

Project Overall Status & Project Page

The work on project commenced on March 25 th, 2003. With the start of the work, immediately a website for the project was put in place. The project website is located at: http://genie.iitd.ernet.in/wipo/

The project page at the above location provides an overview of the project. The detailed design has been completed and key design decisions have been validated by testing/implementing a pilot version of the project in the lab environment. A technical report detailing the design and key concepts relevant to the project is enclosed and is also available on the page. The report also serves as a ”how-to” guide, on setting up the necessary infrastructure and software modules. This report is updated periodically, to re ect the developments in the project. A list of references and other project related documentation are also available from the site.

Project Design

The initial technical design for the project consists of the following four components

• Design issues for the Internet Gateway Station,
• Design of Wireless Network Architecture,
• Design/Selection of Wireless Communication Protocols to be used and
• Design of Application Modules for
  • Handheld devices
  • Internet Gateway Station
  • Wireless relay stations

Key Design Decisions

The design for the above components has been largely completed. A detailed document specifying the design as well as the current test setup is enclosed.

Some of the more important design decisions taken during the design phases of the four components are

• Use Ad-Hoc On Demand Vector Routing (AODV) for routing amongst the wireless relay stations. This protocol has been borrowed from Mobile Ad-Hoc Wireless Networks model and was modified to suit the requirements of this project.
• Provide IP based network connectivity to all the nodes in the mesh network formed by the wireless relay stations.
• Use standard email as a base platform for text messaging. Email distribution will be done using the domain name allocation. A Domain Name Server for this purpose needs to be setup on the Internet Gateway Station. Simple Mail Transfer Protocol (SMTP) is used for email exchange. This ensures that the system is operable with the existing email services on the Internet. Internet Gateway Station will also serve as the mail server for receiving the mails.
• Make the system independent of any specific PDA device. Since the PDA technology is evolving rapidly, we should not lock into a particular PDA hardware and operating system. The proposed solution will work on different hardware platforms (iPAQ, Palm, Zaurus) and operating systems (WinCE/Linux/PalmOS) alike. The main choices to make it operating system platform independent are as follows:
• Use POP3 (supported by almost all operating system platforms) on PDA for email retrieval from the mail server(s).
• All the platforms normally support an email client capable of email retrieval using POP3. The other option is to provide a web based email access from the mail servers. This can be done using Squirrelmail software provided with the RedHat distribution being used for the mail server(s).

To make the system hardware independent we chose to use

• Communication on Infrared (IrDA) interface with the wireless relay stations. Optionally, we also plan to support communication between the PDA and the wireless relay stations over USB ports as a part of the ongoing work in the project.

Pilot Implementation

An initial pilot implementation of the basic WIPO system (v 1.0) has been done and tested in the laboratory environment. The current implementation is based upon Linux platform has been used for the

• relay stations
• mail server(s)
• Internet Gateway Station

The implementation of AODV available from National Institute of Standards and Technol-ogy (NIST) has been used. This implementation has been modified for the purpose of this application. The patches for this implementation are soon going to be made available on the project website.

• Infrared (IrDA) has been used for communication between a PDA and the wireless relay stations.
• HP iPAQ WinCE based PDA’s have been used for development and testing purposes.

For the wireless relay stations, 802.11b wireless network adapters available from Cisco (Cisco Aironet 350 Series) have been used.

• Yagi Antenna’s have been used for increasing the transmission range of the off-the-shelf 802.11b hardware.
• Since there are constraints on local availability of 802.11b antenna we experimented with building our own antennas for increasing transmission range of the 802.11b wireless network interfaces. Towards this end a micro-strip antenna has been designed and is under construction and further testing.
• As a part of the experimentation with different PDA devices, an attempt was also made to use Simputer. However the support available for the Simputer hardware was not satisfactory and so we have deferred this effort.

Open Issues

Some of the main issues faced so far in the implementation of the project are

• In our design, some of the wireless relay stations need to be able to communicate via multiple network interfaces to different nodes in their vicinity (typically 2 to 3). For optimum operation, it is desirable that these communication not interfere with each other. However, simultaneous communication along multiple links amongst these relay stations would interfere with each other if same frequency is used for all such links. This interference reduces the effective
  available bandwidth though the system is still functional and sufficient bandwidth would still be available given the limited requirements of text messaging.
• To overcome the interference issue, we tried to configure the Cisco Aironet cards to function on different frequency channels available in the 802.11b framework. However, in the AdHoc mode of communication, the Cisco Aironet 350 Series cards use Channel 6 by default. We did experiments to alter the frequency channel being used for transmission. However, using the available Cisco utilities/driver we could not accomplish the above task. We are in communication
  with Cisco on this. It could be a firmware or manufacturer specific issue since the 802.11 standard does not impose any such constraint. We also plan to investigate Orinoco equipment as an alternative.
• During the experimentation with the available Yagi Antenna we faced some problems involving system setup. Currently we have tested them to work over a range of approximately 500 mts. We plan further experiments to see the limits of their range. Alternatively, using parabolic antennas, other researchers working at IIT Kanpur have achieved ranges of 10’s of kilometers using 802.11b equipment, so their does not seem to be any fundamental limitation.
• The antennae & corresponding cables for 802.11b are still not easily available in India. Currently these need to be imported though if volumes are there they can be locally produced.
• Cost of PDA devices may also be an issue. We were not able to procure low cost PDA’s locally. However, since PDA’s are evolving rapidly and prices are dropping very quickly this may not be a problem by the time this system is deployed in any scale. We would like to experiment with Palm/other devices but the availability of authorized suppliers of many of these devices is not there as of now in India.

Plan going forward

For the next phase of the project, we plan to take up the following tasks

1. We plan to resolve the interference issues with multiple communication ows on a same node.

Two of the possible schemes that we plan to take up are:

• Try to use non-overlapping and different 802.11b channels
• Using MAC layer filters

2. Integrate the various modules of the project. This will involve integrating the application module and the communication protocols with the designed network architecture.

3. After integration of all the modules, another important activity would be to complete a stable test-bed within the IIT campus. This will help us evaluate the technology much more easily in real life scenarios.

4. We also would like to test our setup in the presence of long power outrages/failures since our design of the messaging system is designed to handle it. 5. As a concluding step, we would take up testing and performance analysis of the entire setup.

Read the Abstract of Project
Read the Project Proposal
Read the Technical Report (PDF, 400 kb)