SDR Prototype for Clipped and Fast-Convolution Filtered OFDM for 5G New Radio Uplink

Abstract

In wireless communications, higher transmission power enables higher coverage or higher data rate. However, due to hardware limitations, achieving high power efficiency becomes challenging. The main issue is that at high power region close to power amplifier (PA) saturation point the highly non-linear response of the PA leads to significant spectral regrowth. In such a case, waveforms with inherently good spectral containment allow for more spectral degradation and can be seen as the most effective solution for the problem. In this study, a fifth-generation new radio (5G NR) user equipment (UE) transmit power is improved by utilizing fast-convolution filtered orthogonal-frequency-division-multiplexing (FC-F-OFDM) waveform, which has an excellent spectral containment performance. A novel method is proposed for improving the peak-to-average-power ratio (PAPR) of FC-F-OFDM waveform, based on applying clipping before FC processing and allocating the clipping noise that stems from the applied clipping, over not only on active band, but a wider band consisting of both the in-band and guard-band regions. An accurate transmitter chain simulator including a measured memory-polynomial model of a practical PA is used to evaluate a wide set of different subcarrier spacings and channel bandwidths. Then, to validate the numerical results, a software-defined radio (SDR) based testbed is created and the modeled PA is used in this testbed. Weighted overlap-and-add (WOLA) based OFDM, also with clipping, is used as a reference in both the numerical evaluations and in measurements. For both waveforms, the transmitted signal quality, out-of-band emissions, and maximum PA output powers are measured under 5G NR specifications and results for different subcarrier spacings and channel bandwidths are provided to prove the benefits and robustness of the presented FC-F-OFDM approach. INDEX TERMS Fifth-generation new radio (5G-NR), fast convolution (FC), filtered OFDM, physical layer, prototype, software-defined radio (SDR), power amplifier (PA), weighted overlap-and-add (WOLA), peakto-average-power ratio (PAPR).

Bit Error Rate Analysis of NOMA-OFDM in 5G Systems With Non-Linear HPA With Memory

“…whereâ 1,k represents the estimated symbol and A 1 represents the alphabet of the user 1 constellation. In accordance with the theoretical analysis presented in [16], the probability of error of user 1 can be calculated using (30) where…”

“…Thus, studies that analyze the effect of HPA in OFDM are very important. In the literature, several works that explore the impact of HPA without memory can be found, for instance, the performance analysis in terms of SER, BER, and power spectral density [22][23][24], analysis of techniques for reducing the PAPR and linearization of HPA [25][26][27], implementation of PAPR reduction techniques [28][29][30] among others. However, although for wideband systems, memory effects should not be disregarded, very few papers analyzing this scenario can be found in the literature [31].…”

Novel Iterative Clipping and Error Filtering Methods for Efficient PAPR Reduction in 5G and Beyond

“…where is TX-side WOLA processing and it consists of submatrices realizing symbol length extension and windowing, as described in [23]. Next, "DPD processing" in Fig.…”

A Local Oscillator Phase Compensation Technique for Ultra-Wideband Stepped-Frequency Continuous Wave Radar Based on a Low-Cost Software-Defined Radio

“…Software-defined radio (SDR) is a tool that is primarily intended to be used to test and prototype various communication applications such as wireless communications and the Global Navigation Satellite System (GNSS). For example, these include mobile telecommunication [ 1 , 2 ], multi-static multiple-input and multiple-output (MIMO) communication [ 3 , 4 , 5 ], Wi-Fi [ 6 ], characterizing radio-frequency identification (RFID) tags [ 7 , 8 ], prototyping a global positioning systems (GPS) receiver [ 9 , 10 ], locating satellites [ 11 ], and indoor positioning [ 12 ]. The use of SDR is becoming popular because of the fully digital in-phase and quadrature (I/Q) interface, which provides flexibility in signal generation and postprocessing of received signals.…”