In this paper, we propose the opportunistic cooperation based on delayed retransmissions (OC-DR) for a multi-user uplink system. There are N users and one destination (Base station). At a given timeslot, a user who has the best channel condition to the destination is selected to transmit its data. Adaptively dividing the allocated timeslot into the sub-timeslots for its own data and other users' data, the user sequentially transmits its data and previously received other users' data during each sub-timeslot, respectively. Using this cooperation protocol, we can achieve maximally N 2  diversity order, the second power of number of users. Additionally, the OC-DR can improve resource fairness in asymmetric multi-user systems.
['Jinsu Kim', 'Jae Hong Lee']
Opportunistic Cooperation Based on Delayed Retransmissions for a Multi-User Uplink System