  In this letter, we propose a new pulse position modulation (PPM) scheme,
called expurgated PPM (EPPM), for application in peak power limited
communication systems, such as impulse radio (IR) ultra wide band (UWB) systems
and free space optical (FSO) communications. Using the proposed scheme, the
constellation size and the bit-rate can be increased significantly in these
systems. The symbols are obtained using symmetric balanced incomplete block
designs (BIBD), forming a set of pair-wise equidistance symbols. The
performance of Q-ary EPPM is better than any Q-ary pulse position-based
modulation scheme with the same symbol length. Since the code is cyclic, the
receiver for EPPM is simpler compared to multipulse PPM (MPPM).
