With advances in wireless networking technology and portable
information appliances, a new paradigm of computing, called mobile or nomadic computing,
has generated much attention in recent years. This new platform will make it
possible for users who carry portable devices to browse WWW information
regardless of their physical location or movement behavior. Such a new
environment, however, faces many technical challenges such as limited wireless
bandwidth and high error rate. In addition, mobile devices widely differ with
respect to display size, color depth, processing power, battery life, and the
ability to handle different data formats. Since images usually present the
highest rate of WWW traffic, image transcoding could greatly reduce web page
retrieval latency and match both the device and channel capabilities. This
thesis presents a proxy transcoding process that enhances image transmission to
a variety of mobile hosts. The central idea in our work is to place a
transcoding proxy between the generic WWW servers and the diversity of client
devices in order to adapt to a greatly changing bandwidth on the proxy-client
link and to manage the heterogeneity of small-screened mobile devices. The
proxy utilizes transcoding functions based on the available bandwidth and the
device characteristics to achieve the smallest file size and acceptable
quality.