Abstarct: Adaptive transmission is a promising technique to enhance spectral efficiency of wireless transmissions over fading channels. In adaptive systems, certain transmission parameters such as constellation size, transmitted power, and code rate are dynamically adjusted according to the channel quality, which increases the average spectral efficiency without wasting power or sacrificing error probability performance. On the other hand, Cooperative communication systems using various relay strategies can enhance coverage and potentially increase capacity by creating a virtual multi-input multi-output system, and thus,exploiting the spatial diversity. This thesis examines the benefits of using adaptive modulation in terms of outage probability and average spectral efficiency in cooperative communication networks. Specifically, we focuse on the performance of amplify-forward (AF), Decode–forward (DF), and Hybrid-Decode-Amplify-Forward (HDAF) relaying scheme in conjunction with adaptive modulation over flat fading Rayleigh channels.A close form of Outage analyse as well as average spectral efficiency analyse are drived for each cooperative networks. Finally, numerical results are presented which are showing the comparison for the performance of mentioented networks.