This paper investigates block-level interference exploitation (IE) precoding for multi-user multiple-input single-output (MU-MISO) downlink systems. To overcome the need for symbol-level IE precoding to frequently update the precoding matrix, we propose to jointly optimize all the precoders or transmit signals within a transmission block. The resultant precoders only need to be updated once per block, and while not necessarily constant over all the symbol slots, we refer to the technique as block-level slot-variant IE precoding. Through a careful examination of the optimal structure and the explicit duality inherent in block-level power minimization (PM) and signal-to-interference-plus-noise ratio (SINR) balancing (SB) problems, we discover that the joint optimization can be decomposed into subproblems with smaller variable sizes. As a step further, we propose block-level slot-invariant IE precoding by adding a structural constraint on the slot-variant IE precoding to maintain a constant precoder throughout the block. A novel linear precoder for IE is further presented, and we prove that the proposed slot-variant and slot-invariant IE precoding share an identical solution when the number of symbol slots does not exceed the number of users. Numerical simulations demonstrate that the proposed precoders achieve a significant complexity reduction compared against benchmark schemes, without sacrificing performance.

翻译：本文研究了多用户多输入单输出（MU-MISO）下行链路系统中的块级干扰利用（IE）预编码。为了克服符号级IE预编码需要频繁更新预编码矩阵的问题，我们提出联合优化传输块内的所有预编码器或发射信号。所得预编码器仅需每个块更新一次，且不一定在所有符号时隙上保持恒定，我们将该技术称为块级时变IE预编码。通过仔细研究块级功率最小化（PM）与信干噪比（SINR）均衡（SB）问题中的最优结构及显式对偶特性，我们发现联合优化可分解为变量维度更小的子问题。更进一步，我们通过在时变IE预编码上添加结构约束，提出块级时不变IE预编码，以在整个块内保持预编码器恒定。进一步提出了一种面向IE的新型线性预编码器，并证明当符号时隙数不超过用户数时，所提时变与时常IE预编码具有相同解。数值仿真表明，与基准方案相比，所提预编码器在无需牺牲性能的情况下显著降低了计算复杂度。