A Flexible FPGA-Based Channel Emulator for Non-Stationary MIMO Fading Channels

Abstract

In this paper, a discrete non-stationary multiple-input multiple-output (MIMO) channel model suitable for the fixed-point realization on the field-programmable gate array (FPGA) hardware platform is proposed. On this basis, we develop a flexible hardware architecture with configurable channel parameters and implement it on a non-stationary MIMO channel emulator in a single FPGA chip. In addition, an improved non-stationary channel emulation method is employed to guarantee accurate channel fading and phase, and the schemes of other key modules are also illustrated and implemented in a single FPGA chip. Hardware tests demonstrate that the output statistical properties of proposed channel emulator, i.e., the probability density function (PDF), cross-correlation function (CCF), Doppler power spectrum density (DPSD), and the power delay profile (PDP) agree well with the corresponding theoretical ones.

A Scalable Spatial–Temporal Correlated Non-Stationary Channel Fading Generation Method

“…The discrete Doppler frequency fn,m can be characterized by the DPSD Ŝσ n σ n ( f ). We first divide the DPSD into M parts and determine fn,m with the MEA method [24], which can be expressed as…”

“…The sum-of-sinusoids (SoS) method proposed in [20][21][22] was suitable for the implementation of FPGA hardware platforms, but it suffered from a problem of phase discontinuity. In [23,24], the authors proposed the sum of frequency modulation (SoFM), which solved the problem of Doppler frequency inaccuracy and phase discontinuity but did not account for the spatial-temporal correlation function (ST-CF) of channel fading. In [25,26], the authors introduced a MIMO generation method that incorporated a spatial-temporal correlation function (ST-CF) based on the Kronecker model.…”

A Method of Implementing a 4 × 4 Correlation Matrix for Evaluating the Uplink Channel Properties of MIMO Over-the-Air Apparatus

“…In OTA testing, investigations primarily focus on evaluating the performance of mobile terminals in downlink channels [9][10][11][12][13][14][15][16][17]. For the uplink channel, OTA testing of a massive MIMO BS has been conducted; however, MIMO terminal OTA testing has not yet been reported [18,19].…”

“…In the two-stage method , the measurement is divided into two stages: first, measurements of the MIMO antenna patterns that contain all the necessary information to evaluate the antenna’s performance, such as radiation power, efficiency, and correlation, are made; then, the measured antenna patterns are incorporated with the chosen MIMO OTA channel models for real-time emulation [ 11 , 12 ]. The advantage of this method is the reduced number of instruments required, compared with the multiple probe antenna based method introduced next.…”

“…The characteristics of the three OTA measurement methods are summarized as follows. Using a universal software radio peripheral [9] 2 × 2 MIMO, NLOS, 28 GHz [10] Two-stage method Mobile terminal 3D channel model, active antenna array [11] Non-Stationary channel model [12] Multiple probe antenna based method…”