Space-Division Multiple Access Based on Time-Modulated Array

A novel space-division multiple-access (SDMA) method is proposed by the multibeam characteristic of the time-modulated array (TMA). The TMA generates the fundamental and harmonic components pointing to different directions. For the uplink, the users in different directions transmit the signals with the same carrier frequency to the base station with the TMA. Then, the base station distinguishes the users by the generated harmonic components. For the downlink, signals of different users are modulated to different carrier frequencies beforehand. Because of the modulation of the TMA, the downlink signals are transmitted to different directions with the same carrier frequency. Compared to the traditional SDMA systems implemented by the Butler matrix beamforming or the digital beamforming, the proposed method implements the SDMA with a single RF channel, which has advantage in the hardware complexity and cost. The uplink and downlink schemes are analyzed, and their drawbacks are discussed. A simple TMA is constructed to verify its effectiveness.