In this project, we propose a novel method of cooperative spectrum sharing which is based on the dimension of modulation, instead of the three basic dimensions: time, frequency, spatial. Then, we create a concept of modulation-based spectrum access. Our method allows for creating spectrum whitespace for simultaneous spectrum sharing for the co-existing system with low-cost and low-complexity or with high-cost/high-complexity. As a result, this overcomes the drawbacks of current cooperartive spectrum sharing methods and including the advantage of the current cooperative spectrum sharing.