Exploiting Infrastructure Resources to Support Mobile
630 Distributed Mobile Systems project proposal
Srividya , Ramkishore , Prakash and Kartik .
Mobile elements are resource
poor relative to stat
ic elements with respect to
power, weight and size and also with regard to computational abilities like
processor speed, memory size, disk capacity and also limited I/O capabilities.
The project attempts to explore as to how fixed network resources such as
display and I/O devices can be used efficiently to interoperate with existing
handheld devices like PDAs, specifically a Compaq IPAQ.
With the coming wireless technologies, such as BlueTooth and IEEE 802.11,
held computers a
nd conventional computers together will no
longer be an occasional event for synchronization. Instead, the devices
will frequently be in close, interactive communication. Many environments, such
as offices, meeting rooms and classrooms, already
contain computers, and the
smart homes of the future will have ubiquitous embedded computation. When the
user enters one of these environments carrying a hand
held or wearable
computer, how will that computer interact with the environment?
Typically, PDAs come with cables or docking stations to connect them to your
desktop or notebook computer. Using wireless technology to interconnect PDAs
and desktops is imminent. Once achieved there is unlimited scope for
development of applic
ations that can work on both the environments.
Transportation of the PDA display on to a desktop would be one such
application. Some PDAs have monochrome or gray
scale displays, while others
can display anywhere from 256 to 64,000 colors. Screen size wi
ll vary among
PDAs and a larger screen means more readable space. Likewise entering
information into the handheld device using a normal keyboard would also prove
to be very effective rather than struggling with a miniature model of one such
The proposal goes on to describe the background information, which forms the
motivation of the project, methodology and tasks involved, the hardware and
software resources required.
Similar Protocol Method: VNC
The VNC protocol is
a simple protocol for remote access to graphical user
interfaces. The protocol simply allows a server to update the framebuffer
displayed on a viewer. Because it works at the framebuffer level it is potentially
applicable to all operating systems, windowi
ng systems and applications. This
includes X/Unix, Windows 3.1/95/NT and Macintosh, but might also include
PDAs, and indeed any device with some form of communications link. The
protocol will operate over any reliable transport such as TCP/IP.
re exists a VNC protocol for Palm OS called as PalmVNC and also for
the WindowsCE environment. Our protocol also attempts to provide remote
control of the application apart from just teleporting the display of the device.
over a desktop machine running on WinNT and to transport the display of
the PDA on to the display of a desktop as well as to control the applications of
the PDA from the desktop.
In order to achieve the proposed objective the methodology has b
een split into
Simple Advertisement Protocol:
The aim of the protocol is to help the PDA discover a Windows NT machine on a
wired local area network, which runs the server program. The protocol is
relatively simple compared to the
computationally more intensive service
discovery protocols existing on wired networks. The design principles are
The access point will always keep track of all the static wired systems around the
access point through advertisement file
. This file can be initially created on the
gateway that links the access point to the wired system. The file will have the
following fields describing the machine.
<Machine name, IP address, status>
Machine name has the name of the machine, IP address
field its corresponding
IP address and status represents the server program running on that particular
machine. The fields in the file and the status of a particular Windows NT machine
will be changed whenever the Server program successfully runs and waits
incoming client request at a particular port. The status of the machine changes
again when the server program successfully exits.
In this way, the advertisement file will keep track of all the machines that are
running the server program. Now, whe
n the PDA wants to find a Windows NT
machine running the server program, advertisement file will provide all the
necessary information. Since each access point will have an advertisement file,
wherever the PDA goes it can get the information about the serv
ers on desktop
windows NT machines around it.
The PDA user will then select one of the machines around him and the IP
address of that particular machine will be given to the client program as the first
step for the remote PDA device control.
Transport of Display:
The display device of the PDA is present as a Device Dependent Bitmap(DDB)
file in the framebuffer of the PDA system. This is converted into a Device
Independent Bitmap(DIB) file by the graphics device driver provided by the
s API. The DDB is essentially specific to a particular device driver while
the DIB can be used by any graphics display device driver.
The DIB is then encoded using one of the encoding algorithms like run
encoding or Huffman coding algorithm. This i
s done to reduce the data being
transmitted over the network thereby improving the efficiency of the protocol. The
encoded DIB is then transferred through the access point to the desktop machine
on the wired network using Winsockets.
The desktop machine r
eceives the encoded DIB file through a socket that is kept
open once the connection has been established. The DIB file is then decoded to
get the original DIB file. The display device driver then displays this file onto the
specific application process tha
t runs on the desktop.
Transport of Control:
Input events are simply sent to the client by the server whenever the user
presses a key or mouse button, or whenever the pointing device is moved. When
the mouse movement or keyboard event is execu
ted, the event is sent to the
Event and Message Handler queue. This information is sent back to the PDA via
the open sockets to a similar queue at the PDA device. The events in the queue
are then executed and the subsequent changes in the display are trans
described by Phase 2 in the previous section.
The following block diagram presents an overview of the project.
Event and message
Handler For windows
NT Test Machine)
Event and Message
Future work and Applications:
ject described above by itself is one of many applications that can be
developed using similar concepts. Some of the other applications are
Make presentations at conferences.
Control the applications of a desktop remotely.
Caching Management scheme of the display at the viewers end.
For Developing Application on palms we use
Microsoft eMbedded Visual Tools 3.0
Microsoft eMbedded Visual Tools 3.0 includes embedded versions of Visual
sic® and Visual C++®. With it, developers can create applications and
components for Windows CE
powered devices such as Handheld PC Pro,
size PC, and Pocket PC, or custom embedded systems. Windows CE
3.0 is a real
time operating system that support
bit appliances and
For developing application in WIN
NT Environment we use
Microsoft Visual C++ and Windows
Compaq IPAQ with Windows
CE operating system
NT LAN Environment.
Wavelan card for wireless
Established Wireless Network with an Access point.
Tristan Richardson, Kenneth R Wood ORL, Cambridge version
3.3 Jan 1998 revised July 1998.
Borland C++ 4.0 programming for Windows”
h Usage Analysis of Service Location protocol”
School of Computer Science, Carleton University, Ottawa, Canada.
Fundamental Challenges in Mo
PDOC’96, Philadelphia, USA. 1996.
Talk: "Using Handheld Computers and PCs Together" (an overview of the
“Differential X Protocol Compressor”