Dynamic metasurface antennas (DMAs) promise to relieve massive multiple-input multiple-output architectures from their high energy consumption and hardware costs. This paper proposes a two-timescale design for downlink multiuser transmission via DMAs, a design that balances pilot overhead, complexity, and spectral efficiency. At the onset of each frame, the DMA coefficients are configured based only on statistical channel-state information (CSI), a process for which the paper introduces an optimization framework that is shown to outperform the widely used stochastic successive convex approximation method. Then, within each frame, the digital precoder is updated at each slot, based on the optimized DMA coefficients and the effective lower-dimensional instantaneous CSI. The weighted minimum mean-squared error method is applied for this short-term optimization and, for the special case of single-user transmission, a closed-form solution for the digital precoder is provided. Performance evaluations demonstrate that the proposed two-timescale design can be an attractive ingredient for future wireless networks.

翻译：动态超表面天线有望缓解大规模多输入多输出架构的高能耗与硬件成本问题。本文提出一种用于下行多用户传输的双时间尺度设计方法，该设计在导频开销、计算复杂度与频谱效率之间取得平衡。在每个帧起始时刻，仅基于统计信道状态信息配置动态超表面天线系数，为此提出一种优化框架，其性能优于广泛使用的随机逐次凸逼近方法。随后在每个帧内，根据优化后的动态超表面天线系数与有效低维瞬时信道状态信息，在每个时隙更新数字预编码器。针对此短期优化问题采用加权最小均方误差方法，并在单用户传输的特殊情形下给出数字预编码器的闭式解。性能评估表明，所提双时间尺度设计可成为未来无线网络中的有效技术方案。