Base stations in 5G and beyond use advanced antenna systems (AASs), where multiple passive antenna elements and radio units are integrated into a single box. A critical bottleneck of such a system is the digital fronthaul between the AAS and baseband unit (BBU), which has limited capacity. In this paper, we study an AAS used for precoded downlink transmission over a multi-user multiple-input multiple-output (MU-MIMO) channel. First, we present the baseline quantization-unaware precoding scheme created when a precoder is computed at the BBU and then quantized to be sent over the fronthaul. We propose a new precoding design that is aware of the fronthaul quantization. We formulate an optimization problem to minimize the mean squared error at the receiver side. We rewrite the problem to utilize mixed-integer programming to solve it. The numerical results manifest that our proposed precoding greatly outperforms quantization-unaware precoding in terms of sum rate.
翻译:位于5G和5G以上的基地台使用先进的天线系统(AASs),其中多个被动天线元件和无线电装置被纳入一个单一的盒子。这种系统的一个关键瓶颈是AAS和容量有限的基带单元(BBU)之间的数字前方孔径。在本文中,我们研究了用于在多用户多输入多输出多输出(MU-MIMO)通道上预先编码下行传输的AAS系统。首先,我们介绍了在BBU计算预编码器并随后在前门上进行量化时创建的基线孔径软件预编码计划。我们提出了一个新的预编码设计,以了解前方孔的孔径。我们提出一个优化问题,以尽量减少接收器侧的平均平方错误。我们重写问题,以使用混合内输入程序来解决它。数字结果显示,我们提议的预编码大大超出在总和率方面进行二次转换前软件前的元编码。