This is a drop-in replacement for TOSSIM's radio stack that operates atthe packet, rather than the bit, level. In preliminary testing itperforms about 100 times faster than the default bit-level radio stack.Obviously it does not capture the subtleties and behavior of thebit-level simulation, but, it is useful for testing and simulating largenetworks. To use this code, all you need to do is add the line  PFLAGS = -I$(BASEDIR)/tos/platform/pc/packetto your application Makefile, then rebuild your application with 'make pc'.This packet-level simulation is compatible with TOSSIM's lossy radiomodels, so if you are using "-r lossy" or setting link-level lossprobabilities with TinyViz, it will work.Currently, the component does not model packet collisions (e.g., thehidden terminal problem), MAC contention, or variable transmissiontime due to these effects or packet length. Packet transmission takes1/40th of a second, based on the empirical observation that the micaradio stack can handle about 40 packets/s. Some rough tests indicatethat packet loss rates due to bit errors from the packet-level modelare roughly equal to those in the bit-level model.Please note, while using this component will tremendously increase therate of simulation, its ignorance of the hidden terminal problemreally makes it of little use for anything approaching evaluation inany meaningful context.Matt Welsh - mdw@eecs.harvard.eduPhilip Levis - pal@cs.berkeley.edu