56 (5): 2517-2528. 13 Tang, Z., Cannizzaro, R.C., Leus, G., and Banelli, P. (2007). Pilot-assisted time-varying channel estimation for OFDM systems. IEEE Transactions on Signal Processing 55 (5): 2226-2238. 14 Huang, J., Zhou, S., Huang, J. et al. (2011). Progressive inter-carrier interference equal- ization for OFDM transmission over time-varying underwater acoustic channels. IEEE Journal of Selected Topics in Signal Processing 5 (8): 1524-1536. 1 ICI Cancellation Techniques Based on Data Repetition for OFDM Systems 15 Cheng, X., Wen, M., Cheng, X., and Yang, L. (2015). Effective mirror-mapping-based intercarrier interference cancellation for OFDM underwater acoustic communications. Ad Hoc Networks (Elsevier) 34: 5-16. 16 Li, B., Zhou, S., Stojanovic, M. et al. (2008). Multicarrier communication over under- water acoustic channels with nonuniform Doppler shifts. IEEE Journal of Oceanic Engineering 33 (2): 198-209. 17 Beaulieu, N.C. and Tan, P. (2007). On the use of correlative coding for OFDM. 2007 IEEE International Conference on Communications, Glasgow, UK, June 2007, pp. 756-761. Filtered OFDM: An Insight into Intrinsic In-Band Interference Juquan Mao Lei Zhang2 2 and Pei Xiao1 1 Institute for Communication Systems (ICS), Home of 5G Innovation Centre, University of Surrey, UK 2James Watt School of Engineering, University of Glasgow, UK 2.1 Introduction Orthogonal frequency division multiplexing (OFDM) has strengths such as robustness against multipath fading, a simple implementation based on fast Fourier transform (FFT) algorithms, and perfect compatibility with multiple-input multiple-output (MIMO) tech- nique. With these advantages, OFDM is extensively adopted in modern communication systems. However, due to limited spectrum localization, OFDM has significant limitations in challenging new spectrum use scenarios, such as asynchronous multiple access, as well as mixed numerology cases aiming to use adjustable numerologies, such as subcarrier spacing (SCS), symbol length, and cyclic prefix (CP) length, in sup