Vector perturbation for single-carrier MU-MIMO downlink

In this paper, we propose two vector perturbation (VP) schemes for single-carrier (SC) multi-user (MU) multiple-input multiple-output (MIMO) downlink block transmission. The first VP scheme (called SC-VP-1) adds a perturbation vector to each user´s signal block in time-domain and then, multiplies a precoding matrix to perturbation vector-added signal blocks in time-domain. The precoding matrix used in this paper takes into account delay waves unlike the conventional VP. In order to reduce the computational complexity of perturbation vector search, a combination of QR decomposition and M algorithm is applied. On the other hand, in the second VP scheme (called SC-VP-2), each user´s perturbation vector-added time-domain signal block is transformed into the frequency-domain signal block before multiplying a precoding matrix. In SC-VP-2, unlike conventional VP and SC-VP-1, an equivalent time-domain expression for the frequency-domain precoding matrix multiplication is used for QR decomposition and M algorithm based perturbation vector search. The uncoded bit error rate (BER) performance achievable by SC-VP-1 and SC-VP-2 is evaluated by computer simulation. It is shown that SC-VP-1 and SC-VP-2 provide the same BER performance. It is also shown that SC-VP achieves better BER performance than both SC-MU-MIMO using channel inversion (CI) and orthogonal frequency division multiplexing (OFDM) MU-MIMO using VP (OFDM-VP). Computational complexity is compared among SC-VP-1, SC-VP-2, and OFDM-VP.