For the multiple-input multiple-output (MIMO) uplink employing high-order quadrature amplitude modulation (QAM) signaling and with nonlinear high power amplifiers (HPAs) at mobile users’ transmitters, the existing multiuser detection methods can no longer be applied. We propose a novel nonlinear multiuser detection scheme for the nonlinear MIMO uplink. Specifically, we adopt an effective B-spline parameterization of the nonlinear transmit HPAs and derive an efficient and accurate algorithm to identify the nonlinear MIMO uplink channel, including the nonlinear B-spline model of the nonlinear transmit HPAs and the estimate of the linear MIMO channel matrix. Moreover, as the direct result of this nonlinear MIMO channel identification, the B-spline inverse model of nonlinear transmit HPAs can readily be identified. The nonlinear multiuser detection can be effectively implemented by the zero-forcing linear detection based on the estimated linear MIMO channel and followed by compensating the nonlinear distortion of the nonlinear transmit HPAs based on the estimated B-spline inverse model. An extensive simulation investigation is performed to demonstrate the effectiveness of our proposed nonlinear multiuser detection scheme for nonlinear MIMO uplink with high-order QAM signaling.

中文翻译：

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非线性 MIMO 上行链路的多用户检测

对于在移动用户发射端采用高阶正交幅度调制（QAM）信令和非线性高功率放大器（HPA）的多输入多输出（MIMO）上行链路，现有的多用户检测方法不再适用。我们为非线性 MIMO 上行链路提出了一种新的非线性多用户检测方案。具体而言，我们采用非线性发射HPA的有效B-spline参数化并推导出一种高效准确的算法来识别非线性MIMO上行信道，包括非线性发射HPA的非线性B-spline模型和线性MIMO信道的估计矩阵。此外，作为这种非线性 MIMO 信道识别的直接结果，可以很容易地识别非线性发射 HPA 的 B 样条逆模型。非线性多用户检测可以通过基于估计线性MIMO信道的迫零线性检测有效实现，然后基于估计的B样条逆模型补偿非线性发射HPA的非线性失真。进行了广泛的仿真研究，以证明我们提出的非线性多用户检测方案对具有高阶 QAM 信令的非线性 MIMO 上行链路的有效性。