Analysis and Mitigation of ICI Due to Gain Adjustment in OFDM Systems

Automatic gain control (AGC) is widely adopted in orthogonal frequency division multiplexing (OFDM) systems to compensate the significant variation of the received signal. In OFDM systems, the duration of the cyclic prefix (CP) is usually equal to the delay spread of the channel to minimize the system overhead. The inter-symbol interference (ISI) between consecutive OFDM symbols spreads over a large portion of the CP. The CP contaminated by the ISI should not be used to estimate the received power. If the duration of the remaining CP is shorter than the settling time of the AGC, then the gain adjustment will be carried out within the useful portion of the OFDM symbol. The subcarrier orthogonality is lost and the system performance is degraded by the resulting inter-carrier interference (ICI). In this paper, we propose a simple and efficient scheme to mitigate the ICI. The proposed scheme can be easily implemented in actual systems because of its low computational complexity. The simulation results show that the proposed scheme can increase the signal-to-interference-plus-noise ratio significantly compared to the traditional scheme.

[1]  Philip Schniter,et al.  Low-complexity equalization of OFDM in doubly selective channels , 2004, IEEE Transactions on Signal Processing.

[2]  Geert Leus,et al.  Simple equalization of time-varying channels for OFDM , 2005, IEEE Communications Letters.

[3]  Behrouz Farhang-Boroujeny,et al.  OFDM Without CP in Massive MIMO , 2017, IEEE Transactions on Wireless Communications.

[4]  Hsiao-Hwa Chen,et al.  Time Domain Precoding for OFDM/OFDMA Systems Without Cyclic Prefix , 2018, IEEE Transactions on Vehicular Technology.

[5]  Santiago Celma,et al.  A High-Performance CMOS Feedforward AGC Circuit for a WLAN Receiver , 2010, IEEE Transactions on Industrial Electronics.

[6]  Guoyu Wang,et al.  Analysis and implementation of digital automatic gain control for DAB baseband decoder , 2011, IEEE Transactions on Consumer Electronics.

[7]  Mohammed Ismail,et al.  A CMOS Norton amplifier-based digitally controlled VGA for low-power wireless applications , 2001 .

[8]  Jie Wang,et al.  A novel feed-forward segmented digital automatic gain control algorithm for long-term evolution digital radio-over-fibre systems , 2017, IET Commun..

[9]  Dong Ku Kim,et al.  Methods for mitigating inter-carrier interference caused by power amplifier transient in LTE modem , 2015, IEICE Electron. Express.

[10]  Rui Dinis,et al.  Performance Evaluation of Quantization Effects on Multicarrier Modulated Signals , 2007, IEEE Transactions on Vehicular Technology.

[11]  Keang-Po Ho.  Maximum-Likelihood Power Estimation for Clipped Signals , 2009, IEEE Signal Processing Letters.

[12]  Yue Yin,et al.  A stable and two-step settling digital controlled AGC loop for GNSS receiver , 2014, IEICE Electron. Express.

[13]  Davide Dardari,et al.  A theoretical characterization of nonlinear distortion effects in OFDM systems , 2000, IEEE Trans. Commun..

[14]  Santiago Celma Pueyo,et al.  Automatic Gain Control: Techniques and Architectures for RF Receivers , 2011 .

[15]  Davide Dardari,et al.  Joint clip and quantization effects characterization in OFDM receivers , 2006, IEEE Transactions on Circuits and Systems I: Regular Papers.

[16]  Donald C. Cox,et al.  Mathematical analysis of the impact of timing synchronization errors on the performance of an OFDM system , 2006, IEEE Transactions on Communications.

[17]  Baoyong Chi,et al.  A Low-Power NB-IoT Transceiver With Digital-Polar Transmitter in 180-nm CMOS , 2017, IEEE Transactions on Circuits and Systems I: Regular Papers.

[18]  Zhang Zhang,et al.  Fast-Settling Feedforward Automatic Gain Control Based on a New Gain Control Approach , 2014, IEEE Transactions on Circuits and Systems II: Express Briefs.

[19]  David Tse,et al.  Fundamentals of Wireless Communication , 2005 .

[20]  Gilberto Berardinelli,et al.  Generalized DFT-s-OFDM Waveforms Without Cyclic Prefix , 2018, IEEE Access.

[21]  Jun Li,et al.  Analysis of the Impact of AGC on Cyclic Prefix Length for OFDM Systems , 2018, IEEE Transactions on Communications.

[22]  Hyung-Jin Choi,et al.  A Fast Automatic Gain Control Scheme for 3GPP LTE TDD System , 2010, 2010 IEEE 72nd Vehicular Technology Conference - Fall.

[23]  Naofal Al-Dhahir,et al.  Sparse Equalizers for OFDM Signals With Insufficient Cyclic Prefix , 2018, IEEE Access.

[24]  Yuping Zhao,et al.  Joint Estimation of Power and DC Offset for OFDM Systems Based on Distribution Function , 2011, Wirel. Pers. Commun..

[25]  Yong-Zhong Xiong,et al.  A 5-Gb/s Automatic Gain Control Amplifier With Temperature Compensation , 2012, IEEE Journal of Solid-State Circuits.

[26]  Bernard H. Fleury,et al.  OFDM Receiver for Fast Time-Varying Channels Using Block-Sparse Bayesian Learning , 2016, IEEE Transactions on Vehicular Technology.

[27]  Jong-Bu Lim,et al.  MIMO-OFDM with insufficient cyclic prefix , 2006, IEEE Communications Letters.

[28]  Wei-Ho Chung,et al.  ICI Self-Cancellation With Cosine Windowing in OFDM Transmitters Over Fast Time-Varying Channels , 2015, IEEE Transactions on Wireless Communications.