Abstract
In this paper, a novel modulation and multiplexing technology for reducing out-of-band leakage is proposed for multicarrier schemes based on CP-OFDM. The proposed method is to spread data of N layers with N selected spreading codes, then multiplex them into a data sequence and transmit it on 2K subcarriers. The N spreading codes, which can suppress out-of-band leakage, are selected out from a complete set of mutual orthogonal spreading codes. The simulation results show that the data modulation and multiplexing technology effectively reduces interference with neighboring frequency bands or adjacent sub-bands for different numerologies and so significantly improves spectrum efficiency
Highlights
This Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation technology subdividing the available bandwidth into a multitude of mutual orthogonal narrowband subcarriers
Combined with cyclic prefix (CP), OFDM is robust against the inter-symbol interference (ISI) and the inter-carrier interference (ICI) of multipath interference [1], [2]
The performance of CP-OFDM system is sensitive to timing offset and frequency offset between the adjacent frequency bands [4]. This is because CP-OFDM suffers from a relative high level of out-of-band (OOB) leakage due to the large sidelobes of the OFDM subcarriers which may result a strong interference into the neighboring frequency bands[5]
Summary
This Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation technology subdividing the available bandwidth into a multitude of mutual orthogonal narrowband subcarriers. New Radio (NR) technology being developed as a 5G technology solution supports different subcarrier spacing values between the adjacent sub-bands within the whole transmission bandwidth [6], [7]. GFDM needs the interference cancellation processing due to the orthogonality conditions relaxation [21] which leads to a more complicated receiver In a word, these new waveform candidates reduce OOB leakage but at a price. Windowing will decrease the effective length of CP which means the resistance to multipath delay is degraded, and the reduction of OOB leakage is not enough which means some guard subcarriers are still needed between the adjacent sub-bands. The spreading codes are utilized to the CP-OFDM scheme to reduce OOB leakage and not to bring up the aforementioned problems.
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