Achieving Multi-user Diversity Gain using User-Identity Feedback

A user-identity feedback method is proposed to achieve multi-user diversity in broadcast channels. This method associates the feedback slots with pre-determined thresholds that diminish with time, and allows feedback from those users whose channel states exceed the threshold assigned to the current slot. Since the threshold can approximate the channel state, this method requires only user-identity feedback. In Rayleigh fading channels, this method is mathematically shown to achieve the sum-rate capacity asymptotically with a large number of users, while requiring only a few feedback slots and little transmission power.