US 9,960,942 B2Granted

Low complexity method for reducing PAPR in FRFT-OFDM systems

AssigneeBeijing Institute of Technology

InventorsHao Huan, Ran Tao, Yue Zhao, Teng Wang

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Abstract

The invention relates to a method for reducing the PAPR in FRFT-OFDM systems, which belongs to the field of broadband wireless digital communications technology. The method is based on fractional random phase sequence and fractional circular convolution theorem, which can effectively reduce the PAPR of the system. The method of the invention has the advantages of simple system implementation and low computational complexity. In this method, the PAPR of the system can be effectively reduced while maintaining the reliability of the system. When the number of candidate signals is the same, the PAPR performance of the present method was found to be almost the same as that of SLM and better than that of PTS. More importantly, the present method has lower computational complexity than that of SLM and PTS methods.

A method for reducing peak-to-average power ratio (PAPR) in a fractional Fourier transform-orthogonal frequency division multiplexing (FRFT-OFDM) communication system, comprising the steps of:

1) at a transmitting end of the FRFT-OFDM communication system, performing an N-point inverse discrete fractional Fourier transform (IDFRFT) of digitalized complex input data X of length N and converting it into time domain to obtain FRFT-OFDM subcarrier signal x(n), wherein n is 1, 2, . . . , N;
2) performing a p-order chirp periodic extension of the FRFT-OFDM subcarrier signal x(n) to obtain an extended chirp sequence, x((n))P,N, wherein chirp refers to a linear frequency modulation and p is the order of Fractional Fourier Transform, and wherein conversion equation for the p-order chirp periodic extension is:
x
⁡
(
n
-
N
)
⁢
e
j
⁢
1
2
⁢
cot
⁢
α
⁢
•
⁡
(
n
-
N
)
2
⁢
Δ
⁢
t
2
=
x
⁡
(
n
)
⁢
e
-
j
⁢
1
2
⁢
cot
⁢
α
⁢
•
⁢
n
2
⁢
Δ
⁢
t
2
wherein α=pπ/2, Δt is sampling interval;
3) shifting x((n))P,N to right by iM (i is 1, 2, . . . , L) points to get x((n−iM))P,N, which further multiplies by RN(n) to obtain chirp circular displacement of FRFT-OFDM signal, x((n−iM))P,NRN(n), wherein L is the length of a random phase sequence;
M=N/L,
R
N
⁡
(
n
)
=
{
1
1
≤
n
≤
N
-
1
0
other
;
4) multiplying x((n−iM))P,NRN(n) by
η
⁡
(
n
,
i
)
=
e
j
⁢
1
2
⁢
cot
⁢
α
⁢
•
⁡
[
-
2
⁢
•
⁢
iM
⁢
•
⁢
n
+
(
i
⁢
M
)
2
]
⁢
Δ
⁢
t
2
point-by-point to obtain φ(n,i) as the following:
φ(n,i)=x((n−iM))P,NRN (n)□η(n,i), i=0,1 . . . L−1, n=0,1, . . . ,N−1
5) multiplying φ(n,i) by weighting factors, r(l)(i), and using a combiner to obtain candidate signals {tilde over (x)}(l)(n) of FRFT-OFDM in time domain as the following:
x
~
(
l
)
⁡
(
n
)
=
∑
i
=
0
L
-
1
⁢
⁢
r
(
l
)
⁡
(
i
)
⁢
•
⁢
φ
(
n
,
i
)
,
n=0, 1 . . . N−1, l=1, 2, . . . S
wherein r(l)(i) is a weighting factor with L-length, and S is the number of alternative Fractional random phase sequence;
6) transmitting a weighting factor r(i)opt that makes PAPR of candidate signals minimum as sideband information of FRFT-OFDM signals, wherein
r
⁡
(
i
)
opt
=
argmin
⁢
⁢
PARP
{
r
(
l
)
⁡
(
i
)
,
…
⁢
,
r
(
s
)
}
⁢
{
x
~
(
l
)
⁡
(
n
)
}
8) using a Digital-to-Analog Converter to convert the transmitting FRFT-OFDM signals with minimum PAPR to analog signals which are further amplified by a High-Power Amplifier after modulated by carrier;
and
9) submitting the amplified analog signals to a transmitting antenna.

211 more elements

Facts

Application

15/402,116Filed 9 Jan 2017 · continuation in part

Priority

CN 2013 1 014218522 Apr 2013

Published

US 2017/0126454 A14 May 2017

Granted

1 May 2018

Term ends

Not estimatedThe source records don’t support an estimate.

Classification4 codes

H04L 27/2614
Multicarrier modulation systems: peak power aspects
H04L 27/263
Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators:…
H04L 27/2651
Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators: modification of fast Fourier…
H04L
Digital communication

Family

PCT/CN2013/082060Parent of this continuation · filed 22 Aug 2013

Application14/886,056Parent of this continuation-in-part · filed 18 Oct 2015

US 2017/0126454 A1Pre-grant publication · published 4 May 2017

Application14/886,056Parent of this continuation

US 2016/0043888 A1Published application

US 9,960,942 B2This patent

From the US filing history. Foreign family members aren’t listed.

Abstract

Claims1