Opportunistic orthogonal writing on dirty paper

A simple scheme that achieves the capacity and the reliability function of the wideband Costa dirty-paper channel is proposed. The scheme can be interpreted as an opportunistic version of pulse position modulation (PPM). This interpretation suggests a natural generalization of the scheme which we show to achieve the capacity per unit cost of Gel'fand-Pinsker channels with a zero-cost input letter. Index Terms--Capacity per unit cost, dirty-paper channel, Gel'fand-Pinsker channel, opportunistic communication, orthogonal signaling, pulse position modulation, pulse position quantization, Wyner-Ziv source coding.