An opportunistic transmission method is proposed. This transmission method is realized just when the fading is above a threshold value. In this opportunistic system the transmitter and receiver are in communication through a feedback link, and the receiver indicates when the transmitter should transmit. We analyze this proposal. Firstable, consider a fading channel then, under co-channel interference. The performance analysis of the proposed system is based on the mean bit error probability, for which analytical expressions are established. These expressions are verified using Monte-Carlo simulations with excellent agree- ment between both results. The opportunistic transmission can combat the fading efficiently. For this technique the mean bit error probability curves under fading are similar to the mean bit error probability curves of ordinary transmission in an AWGN channel. Furthermore, the opportunistic transmission is less sensitive to co-channel interference. © 2013 IEEE. Altamirano, C.D., Avaliaç ão de desempenho de esquemas de modulaç ão e codificaç ão na presença de interfer̂encia de Co-Canal (2011) Master Dissertation, UNICAMPXiao, H., Shao, H., Yang, F., Huang, W., Peng, Q., An optimal transmission policy for opportunistic spectrum access in fading channels (2011) International Conference on Computational Problem-Solving (ICCP)Derakhshani, M., Le-Ngoc, T., Learning-based opportunistic spec-trum access with hopping transmission strategy (2012) IEEE Wireless Communications and Networking Conference (WCNC)Ikki, S., Ahmed, M., Performance analysis of incremental relaying cooperative diversity networks over rayleigh fading channels (2008) IEEE Wireless Communications and Networking Conference (WCNC)Ikki, S., Suhail Al-Dharrab, I., Uysal, M., Exact closed-form error probability expression for cooperative diversity networks with chan-nel estimation errors in time selective rayleigh fading channels (2010) IEEE International Conference on Communications (ICC)Roelofs, H., Srinivasan, R., Van Etten, W., Performance estimation of M-ary PSK in cochannel interference using fast simulation (2003) IEEE Proc. Comm., 150 (5), pp. 335-340Tralli, V., Verdone, R., Performance characterization of digital transmission systems with co-channel interference (1999) IEEE Trans. Vehic. Technol., 48, p. 733745Altamirano, D., De Almeida, C., Evaluation of the co-channel interference effects on the performance of coded networks (2011) IEEE Latin-American Conference on Communications (LATINCOM)Lee, W.C.Y., (2006) Wireless and Cellular Communications, , 3rd edition, McGraw-HillIkki, S., Issa, S., Effects of co-channel interference on the error probability performance of multi-hop relaying networks (2011) Global Telecommunications Conference (GLOBECOM)Bentez, E., Moya, D., Almeida De, C.E., Quelal, G., Avaliaç ão dos efeitos da interfer̂encia de Co-Canal e da diversidade de antenas na probabilidade de erro de bit para modulacões M-QAM em canais com desvanecimento rayleigh (2011) Proceedings of Brazilian Telecommunica-tions SymposiumRappaport, T., (1996) Wireless Communications Principles Practice, , 1st ed., Prentice Hall Communications Engineering and Emerging Technologies Series