Method to provide increased robustness against noise and interference in wireless communications, a transmitter and computer program products thereof

Patent metadata

Field	Value
Publication number	US-10778499-B2
Application number	US-201816052835-A
Country	US
Kind code	B2
Filing date	Aug 2, 2018
Priority date	Aug 4, 2017
Publication date	Sep 15, 2020
Grant date	Sep 15, 2020

Abstract

A method to provide robustness against noise and interference in wireless communications, a transmitter and computer program products, involving sending to a receiver ( 13 ), through a wireless channel ( 12 ), information using a constant-envelope waveform with complex baseband representation of the form s[n]=A c exp{jϕ[n]}. The phase ϕ[n] following the expression
( ϕ ⁡ [ n ] - ϕ ⁡ [ n - 1 ] ) = 2 ⁢ π ⁢ ⁢ m · ∑ k = k 0 + 1 k 0 + N a , F ⁢ ⁢ M + - 1 ⁢ x ⁡ [ k ] ⁢ exp ⁡ ( j ⁢ ⁢ 2 ⁢ π ⁢ ⁢ kn N ) ,
and the wireless channel has an Additive White Gaussian Noise component and flat-fading conditions, wherein the transmitter ( 110 ) calculates a FFT length, N, and a number of active positive subcarriers, N a,FM + , needed in order to have a given improvement in the signal to noise ratio at the active positive subcarriers of the instantaneous frequency spectrum containing the information; calculates a cutoff subcarrier k 0 needed to overcome Doppler, phase noise and carrier frequency offset impairments at the receiver side, and generates a complex baseband signal waveform of the form s[n]=A c exp{jϕ[n]} carrying information with the FFT length, number of active positive subcarriers and cutoff subcarrier.

First claim

The invention claimed is:

1. A method to provide increased robustness against noise and interference in wireless communications, comprising sending, by a transmitter, to a receiver, through a wireless channel, information using a constant-envelope waveform with complex baseband representation of the form s[n]=A c exp{jϕ[n]}, denoted as FM-OFDM waveform, said phase ϕ[n] following the expression

(

ϕ
⁡

[
n
]

-

ϕ
⁡

[

n
-
1

]

)

=

2
⁢
π
⁢

⁢

m
·

∑

k
=

k
0

+
1

k
0

+

N

a
,
FM

+

-
1

⁢

⁢

x
⁡

[
k
]

⁢

exp
⁡

(

j
⁢

2
⁢
π
⁢

⁢
kn

N

)

,

where N is the FFT length, k 0 is a cutoff subcarrier above which the information x[k] is mapped, N a,FM + is the number of active positive subcarriers, and A c and m are real constants, aimed at protecting the information against noise, Doppler, phase noise and carrier frequency offset impairments, wherein said wireless channel has an Additive White Gaussian Noise component and flat-fading conditions,
wherein the method comprises:
calculating, by the transmitter, the FFT length, N, and the number of active positive subcarriers, N a,FM + , that are needed in order to have a given improvement in the signal to noise ratio at the active positive subcarriers of the instantaneous frequency spectrum containing the information;
calculating, by the transmitter, the cutoff subcarrier k 0 that is needed to overcome Doppler, phase noise and carrier frequency offset impairments at the receiver side; and
generating, by the transmitter, a complex baseband signal waveform of the form s[n]=A c exp{jϕ[n]} carrying the desired information with the chosen FFT length, number of active positive subcarriers and cutoff subcarrier.

2. The method of claim 1 , wherein said signal to noise ratio at the active positive subcarriers of the instantaneous frequency spectrum, when taking into account phase unwrap errors, SNR sc,freq,FM unwrap , follows the expression:

(

SNR

sc
,
freq
,
FM

unwrap

)

-
1

=

(

SNR

sc
,
freq
,
FM

)

-
1

+

P
⁡

[
unwrap
]

m
norm
2

⁢

E
⁡

[

1



x
⁡

[
n
]



max
2

]

,

where the

Assignees

• Telefonica Sa

Inventors

• Lorca Hernando Javier
• González Sánchez Carlos

Classifications

• H04L27/366 Primary

  Arrangements for compensating undesirable properties of the transmission path between the modulator and the demodulator · CPC title

• H04L27/26362 Primary

  Subcarrier weighting equivalent to time domain filtering, e.g. weighting per subcarrier multiplication (arrangements for removing intersymbol interference at the transmitter end H04L25/03343) · CPC title

• H04L27/2003

  for continuous phase modulation (frequency shift keying H04L27/10) · CPC title

• H04L27/2634

  Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation · CPC title