165 research outputs found
Time-Domain N-continuous GFDM
Generalized frequency division multiplexing (GFDM) has been a candidate
multicarrier scheme in the 5th generation cellular networks for its flexibility
of transmitter filter in time and frequency. However, for the circularly shaped
transmitter filter, GFDM provides limited performance gain of sidelobe
suppression. In this paper, we propose a scheme, called time-domain
N-continuous GFDM (TD-NC-GFDM), to reduce the discontinuities caused by the
GFDM transmitter filter and achieve promising sidelobe suppression gain. Based
on time-domain N-continuous orthogonal frequency devision multiplexing
(TD-NC-OFDM), TD-NC-GFDM signal can be obtained by superposing a smooth signal
in the time domain. The smooth signal is linearly combined by basis signals in
a new basis set related to GFDM transmitter waveform. To eliminate the
interference caused by the smooth signal, two solutions are proposed. Firstly,
a signal recovery algorithm for reception is adopted at the cost of high
complexity. Thus, secondly, to simplify the TD-NC-GFDM receiver, a
low-interference TD-NC-GFDM is proposed by redesigning the basis signals. A
soft truncation of the basis signals in TD-NC-GFDM is given to design the basis
signals in the low-interference TD-NC-GFDM. Then, the smooth signal is aligned
with the beginning of the GFDM symbol and is added in the front part of the
GFDM symbol. Moreover, for a big number of GFDM subsymbols, theoretical
analysis proves that the signal-to-interference ratio (SIR) in TD-NC-GFDM is
much higher than that in TD-NC-OFDM. Simulation results shows that TD-NC-GFDM
can obtain significant sidelobe suppression performance as well as the
low-interference TD-NC-GFDM, which can achieve the same BER performance as the
original GFDM.Comment: single column, 19 pages, 10 figure
Performance Analysis of a Low-Interference N-Continuous OFDM Scheme
This paper investigates two issues of power spectrum density (PSD) and bit
error rate (BER) of an N-continuous orthogonal frequency division multiplexing
(NC-OFDM) aided low-interference time-domain scheme, when the smooth signal is
designed by the linear combination of basis signals truncated by a window.
Based on the relationship between the continuity and sidelobe decaying, the PSD
performance is first analyzed and compared, in terms of the highest derivative
order (HDO) N and the length of the smooth signal L. Since the high-order
derivative of the truncation window has the finite continuity, the N-continuous
signal has two finite continuities, which may have different continuous
derivative orders. In this case, we develop a close PSD expression by
introducing another smooth signal, which is also linearly combined by other
basis signals, to explain the sidelobe decaying related to N and L. Then, in
the context of BER, considering the multipath Rayleigh fading channel, based on
the effect of the delayed tail of the smooth signal to the received signal, we
provide a procedure for calculating the BER expressed in the form of an
asymptotic summation.Comment: 7 pages, 6 figure
Power spectrum characterization of systematic coded UW-OFDM systems
Unique word (UW)-OFDM is a newly proposed multicarrier technique that has shown to outperform cyclic prefix (CP)-OFDM in fading channels. Until now, the spectrum of UW-OFDM is not thoroughly investigated. In this paper, we derive an analytical expression for the spectrum taking into account the DFT based implementation of the system. Simulations show that the proposed analytical results are very accurate. Compared to CP-OFDM, we show that UW-OFDM has much lower out-of-band (OOB) radiation, which makes it suitable for systems with strict spectral masks, as e. g. cognitive radios. Further, in this paper, we evaluate the effect of the redundant carrier placement on the spectrum
Time-Frequency Warped Waveforms
The forthcoming communication systems are advancing towards improved
flexibility in various aspects. Improved flexibility is crucial to cater
diverse service requirements. This letter proposes a novel waveform design
scheme that exploits axis warping to enable peaceful coexistence of different
pulse shapes. A warping transform manipulates the lattice samples non-uniformly
and provides flexibility to handle the time-frequency occupancy of a signal.
The proposed approach enables the utilization of flexible pulse shapes in a
quasi-orthogonal manner and increases the spectral efficiency. In addition, the
rectangular resource block structure, which assists an efficient resource
allocation, is preserved with the warped waveform design as well.Comment: 4 pages, 5 figures; accepted version (The URL for the final version:
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8540914&isnumber=8605392
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