Partial overlapped time-shifted pilots for massive MIMO systems

This letter proposes a partial-time-shifted pilot scheme to find a better tradeoff between the user accommodation and orthogonality of pilots for the massive multiple-input multiple-output system. To this end, the pilot symbols rather than the pilot sequences are applied. In addition, the neighboring cells are allowed to transmit the pilot signals using the overlapped symbol periods. Despite the stronger interference, the larger user accommodation as well as the near-far effect incurred by using the pilot symbols can contribute to the higher sum transmission rates for both the uplink and downlink cases.