Implementation of complex enumeration for multiuser MIMO vector precoding

In recent years the interest in developing efficient algorithms for the multiple-input multiple-output (MIMO) broadcast channel has arisen. Vector precoding (VP) techniques have shown very promising performance results, but the perturbation process inherent in these type of non-linear systems hinders their efficient implementation. The key to achieving a high-throughput VP implementation is to operate directly on the complex-valued constellations. Nevertheless, the complex-plane Schnorr-Euchner enumerators present in the literature follow a sequential scheme, which derives in an increased system delay and high resource demand in fully-pipelined architectures. This paper presents the first non-sequential complex Schnorr-Euchner enumerator for the precoding scenario. The proposed complex enumerator has been implemented and analyzed along with other state-of-the-art enumeration algorithms. Provided hardware occupation and latency results show that the proposed enumeration algorithm is superior to other existing schemes in terms of hardware resource usage and throughput.