hi, there,
u can try many projects, including.
1- simulation of Wimax physican layer.
2- simulation of soft radio
3- simulation of different modulation schemes like QAM, QPSK,etc
4- simulation of automaic modulation detector
5- implementation of various filters.
6- MIMO system simulation
for communiacation u can also try lmicrowave link planing but it requires various other softwares.
and there r many other projects, u can search on net
but try to meet ur professors.. they can guide u better.