Back to index
Wit: Infrastructure for Wireless Palmtop Computing
Terri Watson, UW
Proxy-like system based on ParcTab IRnet, where Tcl is the programming
language and Tcl-DP-like IPC the transport. Emphasis on application
partitioning between mobile and fixed world, but no uniform
architecture/methodology for doing so, and no notion of BW management
for high-bw apps.
Interesting conclusions (from her quals talk):
- HP-95LX palmtops connect to Parc IRnet. A "half wit" proxy
running in wired network is the liaison to the wired part of the
- Reliable and unreliable transport, proxy communication, UI, and
simple cooperative threading package
available to Tcl on palmtop. App-level handlers talk to each
other, but Tcl's talk to each other on separate logical channels.
- Handoff: as mobile moves, its outgoing packets are routed to a
new BS. Application uses RPC to query which BS is the current
one, but application is not normally notified of handoff.
- Multiple logical streams to same palmtop are separate TCP (or
- Current apps: tty, textual WWW, talk, wireless video. Uses
nv to get frames and send them to the palmtop. No
compression, so we're talking seconds/frame.
- Tcl is a good infrastructure choice for app
development, but there was no BW management and as a result
applications suffered (like video viewer).
- Info browsing most popular app
- Local (mobility) info rarely used, even though it was available!
Contrast to tab and badge systems. Is this a chicken-and-egg
- Perhaps exploit UI to give user hints about relative costs
Implemented instance of proxy concept: application partitioning using a
simple scripting language.
- Lack of BW management really bit them on the butt. The position
paper talks about adapting to connectivity changes, but doesn't
- No "tight integration" between palmtop and fixed apps (eg
consistent calendar or email,etc ); orthogonal to project
- UI/SDK tightly integrated with network -- maybe too tightly?
- No uniform architecture or methodology for partitioning apps.
See Rover for interesting approach to
this. Wit 2 has a data-driven partitioning architecture.
- Design is extremely broad: covers everything from IP
encapsulation in IR drivers all the way up to "UI color and
Back to index