This paper presents a new cooperation scheme, i.e. partial cooperation, in MB-OFDM UWB systems for performance enhancement with high throughput and power efficiency. We first take advantage of the available subbands and design an efficient scheme in the time-frequency plane to deliver information bits to the relay node. Then, based on Game Theory, we propose to use hierarchical modulation, which is capable to offer adaptability and flexibilities to attract even a busy relay node that keeps its own communication link participating in cooperation. We also obtain the optimal power allocation coefficients for the proposed partial cooperation scheme. In addition, the optimal constellation priority parameter of hierarchical modulation is also evaluated. Both analytic and simulation results show that the proposed partial cooperation scheme not only achieves performance enhancement but also can upgrade system utilities of both links to get a win-win solution.