Effective schemes for OFDM sidelobe control in fragmented spectrum use

Abstract

OFDM as multicarrier scheme provides adaptive functionality that is required to implement waveform processing for cognitive radio, dynamic spectrum use and fragmented coexistence scenarios. However, OFDM faces some difficulties due to the relatively strong sidelobes around the active sub carriers, which introduces interference effects between adjacent frequency slots intended to be used independently in non-synchronized way. In this paper we consider edge windowing and cancellation carrier approaches for controlling the spectrum leakage in a practicadl 5 MHz 3GPP LTE scenario. The focus is on minimizing the OFDM signal leakage to narrow unused gaps in the used frequency band, using low-complexity algorithms and minimized overheads in terms of power and spectral efficiency. We develop a simplified version of the cancellation carrier scheme which is suitable for non-contiguous sub carrier allocation in OFDM. It is shown that with relatively narrow unused gaps in the spectrum, it is possible to reach good level of sidelobe suppression with significantly reduced computational complexity.

On massive MIMO and its applications to machine type communications and FBMC-based networks

“…Improved sidelobe suppression for dynamic spectrum access and fragmented spectrum use is claimed achievable using noncontiguous waveforms, such as Cancellation Carriers (CC) or Edge Windowing (EW). In [55], CC-OFDM with a single cancellation carrier is shown better than both its variant with multiple (weighted) cancellation carriers and EW-OFDM, but suppression performance degrades as the subcarrier index runs away from the gap edge.…”

Investigation of Techniques for Reducing Mobile Communication Systems Harmful Out-Of-Band Emission

“…The developers of 3GPP standard are searching for effective way how to reduce the out-of-band emission levels in the OFDM based services. OFDM faces some difficulties due to the relatively strong side-lobes around the active subcarriers, which introduce interference effects between adjacent frequency bands intended to be used independently in nonsynchronized way (Loulou & Renfors 2013;Sadeghi et al 2014;Rajabzadeh Oghaz et al 2014;Selim & Doyle 2013).…”

“…Orthogonal frequency-division multiplexing) sistemose. Pagrindinė aukštos šalutinės spinduliuotės priežastis OFDM sistemose susijusi su naudojamų skaitmeninių filtrų ypatybėmis, kurie neužtikrina didelio slopinimo už pagrindinio ponešlio kanalo, tai sukelia nepriklausomus ir nesinchronizuotus žalingus radijo trukdžius kaimyninėms radijo sistemoms (Loulou & Renfors 2013;Sadeghi et al 2014;Rajabzadeh Oghaz et al 2014;Selim & Doyle 2013).…”

Massive MIMO and Waveform Design for 5th Generation Wireless Communication Systems

“…Improved sidelobe suppression for dynamic spectrum access and fragmented spectrum use is claimed achievable using noncontiguous waveforms, such as Cancellation Carriers (CC) or Edge Windowing (EW). In [38], CC-OFDM with a single cancellation carrier is shown better [3], [8], [41] [43], [44] [2], [3] [45] than both its variant with multiple (weighted) cancellation carriers and EW-OFDM, but suppression performance degrades as the subcarrier index runs away from the gap edge. Another option consists of manipulating OFDM to mimic SCM [2][4] to reduce PAPR and provide robustness against frequency offsets.…”