Joint power control and signature design for time-reversal uplinks

In the time reversal division multiple access (TRDMA) system, the signal-to-noise ratio (SNR) is boosted and the inter-user interference (IUI) is suppressed due to the temporal and spatial focusing effects of the time-reversal (TR) technique. However, since the focusing effects highly depend on the location-specific multipath profile, there exists a strong-weak focusing effect in the TRDMA uplink system where different users at different locations enjoy different level of focusing effects. In this paper, we formulate the strong-weak focusing effect in the multiuser TRDMA uplink system as a max-min signal-to-interference-noise ratio (SINR) balancing problem by means of joint power control and signature filter design. A novel two-stage adaptive algorithm that can guarantee the convergence is proposed. Numerical results show that our algorithm converges quickly, achieves a high energy-efficiency gain, and provides a performance guarantee to all users.