IEEE TRANSACTIONS ON BROADCASTING, VOL. 61, NO. 4, DECEMBER 2015 717
A Novel Multi-Block Tone Reservation Scheme for
PAPR Reduction in OQAM-OFDM Systems
Tao Jiang, Chunxing Ni, Chen Ye, Yiting Wu, and Kai Luo
Abstract— Due to the overlapping structure of the offset quadrature
amplitude modulation-based orthogonal frequency-division multiplex-
ing (OQAM-OFDM) signals, the peak-to-average power ratio (PAPR)
in OQAM-OFDM systems cannot be efficiently reduced by existing
PAPR reduction methods, which independently consider the PAPR
reduction in each data block. In this paper, a novel multiblock tone
reservation (MB-TR) scheme is proposed for the PAPR reduction in
OQAM-OFDM systems. The key idea of the MB-TR scheme is to exploit
the overlapping structure of the OQAM-OFDM signals and jointly con-
sider the adjacent data blocks to obtain the clipping noise. To effectively
eliminate the peaks of the OQAM-OFDM signals, the MB-TR scheme
generates the peak-canceling signal by employing the weighted least
square algorithm to fit the waveform of the peak-canceling signal to the
waveform of clipping noise. Simulation results and analysis show that
the MB-TR scheme could offer better PAPR reduction with lower com-
putational complexity than the clipping control tone reservation scheme
directly employed in OQAM-OFDM systems.
Index Terms—
Offset quadrature amplitude modulation-based
orthogonal frequency-division multiplexing (OQAM-OFDM),
peak-to-average power ratio, multi-block tone reservation,
weighted least square.
I. I
NTRODUCTION
O
RTHOGONAL frequency-division multiplexing (OFDM) offers
considerable high spectrum efficiency, multipath delay spread
tolerance, immunity to the frequency selective fading channels, high
power efficiency [1]. As a result, it has been chosen for high data
rate communications and has been widely used in many digital
broadcasting standards such as digital audio broadcasting (DAB),
digital video broadcasting (DVB), Long-Term Evolution (LTE) and
European Telecommunication Standards Institute (ETSI) Broadcast
Radio Access Network (BRAN) committees [2]. However, OFDM
systems have large spectral sidelobe due to the use of rectangular
window, which leads to the degradation of the spectral efficiency.
Moreover, the data transmission rate of OFDM systems is reduced
by the insertion of the cyclic prefix (CP) [3].
Manuscript received June 19, 2015; revised July 12, 2015; accepted July
21, 2015. Date of publication September 17, 2015; date of current ver-
sion December 5, 2015. This work was supported in part by the National
Science Foundation of China under Grant 61172052 and Grant 61271228, in
part by the National High Technology Development 863 Program of China
under Grant 2015AA01A710, and in part by the Key Program Research
Plan of the National Natural Science Foundation of Hubei, China, under
Grant 2013CFA055.
T. Jiang, C. Ni, and K. Luo are with the School of Electronic Information
and Communications, Huazhong University of Science and Technology,
Wuhan 430074, China (e-mail: tao.jiang@ieee.org).
C. Ye was with the School of Electronic Information and Communications,
Huazhong University of Science and Technology, Wuhan 430074, China.
She is now with Wuhan Zhongyuan Electronic Information Corporation,
Wuhan 430074, China.
Y. Wu is with the School of Physics and Technology, Wuhan University,
Wuhan 430072, China.
Color versions of one or more of the figures in this paper are available
online at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TBC.2015.2465146
As a potential alternative to OFDM systems, offset quadrature
amplitude modulation based orthogonal frequency-division multiplex-
ing (OQAM-OFDM) has drawn significant interests, which utilizes
a prototype filter with low spectral sidelobe and is less sensitive to
the frequency offset than OFDM systems [3]–[5]. The conventional
OQAM-OFDM systems offer extremely low spectral sidelobe, which
leads to significant increase of the spectral efficiency. Moreover,
OQAM-OFDM systems can efficiently overcome the multi-path fad-
ing channel without the help of CP, resulting in the significant
improvement of the data rate [6]. As discussed in [7], in the terres-
trial digital video broadcasting (DVB-T) standard, the OQAM-OFDM
technique can improve the data rate by 13% compared with OFDM.
Therefore, the OQAM-OFDM technique has been accepted as a
potential technique in many digital broadcasting systems, and it has
been considered as one of the key technologies in future wireless
communications [8].
Similar to OFDM systems, one of the main drawbacks for OQAM-
OFDM systems is the high peak-to-average power ratio (PAPR) of
the transmitted OQAM-OFDM signals. Since the high power ampli-
fier (HPA) used in OQAM-OFDM systems has limited linear range,
the OQAM-OFDM signals with high PAPR will be seriously clipped
and nonlinear distortion will be introduced, resulting in serious degra-
dation of the bit error rate (BER) performance [2]. Moreover, the high
PAPR leads to the out-of-band radiation, which causes serious adja-
cent channel interferences [9]. In OFDM systems, various methods
have been proposed to reduce the PAPR in the literature, such as
clipping [10], partial transmit sequence (PTS) [11], active constel-
lation extension (ACE) [12], and tone reservation (TR) [13]–[15].
Nevertheless, it is not very effective to directly employ these meth-
ods in OQAM-OFDM systems, because the OQAM-OFDM signals
are overlapped with multiple adjacent data blocks and these methods
independently consider the PAPR reduction in each data block.
Recently, several schemes have been proposed specifically for the
PAPR reduction in OQAM-OFDM systems [7], [16]. In [16], an alter-
native signals (AS) scheme has been proposed to reduce the PAPR
of OQAM-OFDM signals, which jointly considers the current data
block and the previous data blocks to obtain the optimal phase rota-
tion sequence. However, the AS method needs extra spectral band
to transmit the optimal phase rotation sequence as side informa-
tion. Besides, a segmental PTS (S-PTS) technique has been proposed
in [7], which divides the overlapped OQAM-OFDM signals into a
number of segments and independently reduces the PAPR in each seg-
ment. However, the S-PTS method increases the bit error rate (BER)
since it destroys the orthogonality of OQAM-OFDM systems.
In this paper, we propose a novel multi-block tone reserva-
tion (MB-TR) scheme to reduce the PAPR in OQAM-OFDM
systems, which exploits the overlapping structure of the OQAM-
OFDM signals and jointly considers the adjacent data blocks for
PAPR reduction. For the MB-TR scheme, the clipping noise signal of
all the adjacent data blocks are firstly obtained by a certain clipping
threshold. To effectively eliminate the peaks of the OQAM-OFDM
signals, the MB-TR scheme generates the peak-canceling signal by
employing the weighted least square (WLS) algorithm to fit the
0018-9316
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