Method and device for synchronizing a telecommunications receiver device receiving an impulse radio ultra-wideband signal
View Patent ↗A method for synchronizing in a receiver an IR-UWB signal including data packets having a first preamble portion of at least two sequences of N pulses spaced by period T and each equal to a reference pulse weighted by a complex coefficient c n , n=0 to N−1 indicating the rank of the pulse in the first sequence, and a second preamble portion of at least two sequences equal to the complex conjugate of the first sequence, includes: considering NP successive samples s n , for n=0 to NP−1, of a slice, of duration NT, of the first and respectively second preamble portion of a received packet, determining the sequence of values x n = c ⌊ n P ⌋ * s n , and respectively the sequence of values y n = c ⌊ n P ⌋ z n , with T s the sampling period T=P×T s ; determining the frequency f d and f g of the sequence x n and y n , respectively; and computing shift Δf applied to synchronize to the received signal.
1 . A method for synchronizing a telecommunications receiver device, the telecommunications receiver device receiving an impulse radio ultrawide-band (IR-UWB) signal, the IR-UWB signal comprising data packets, a data packet of the data packets comprising a preamble, the preamble comprising a first preamble portion of at least two occurrences of a first preamble sequence of N pulses spaced apart by a period T and that are each equal to a reference pulse weighted by a complex coefficient c n , n=0 to N−1 indicating a rank of a pulse in a first sequence, and the preamble further comprising a second preamble portion of at least two occurrences of a second preamble sequence equal to a complex conjugate of the first sequence, the method comprising synchronizing the telecommunications receiver device to the received IR-UWB signal according the preamble,
and the method further comprising:
i/ sampling by the telecommunications receiver device, the preamble with a sampling period T s , T=P×T s with P an integer greater than or equal to 1;
ii/ considering NP successive samples s n , for n=0 to NP−1, of a slice, of duration NT, of the first preamble portion of a received signal packet, and determining, by the telecommunications receiver device, the sequence of values,
x
n
=
c
⌊
n
P
⌋
*
s
n
,
where c* is the complex conjugate;
iii/ considering the NP successive samples z n , for n=0 to NP−1, of a slice, of duration NT, of the second preamble portion of a received signal packet, and determining, by the telecommunications receiver device, the sequence of values
y
n
=
c
⌊
n
P
⌋
z
n
;
iv/ determining, by the telecommunications receiver device, frequency f d of the sequence x n and frequency f g of the sequence y n with n=0 to NP−1;
v/ computing, by the telecommunications receiver device, at least one shift to be applied to synchronize to the received IR-UWB signal among a frequency shift Δf and a time shift t 0m according to the following equations:
f
d
=
1
N
P
T
s
(
⌊
t
0
m
T
⌋
+
ϵ
)
+
Δ
f
f
g
=
-
1
N
P
T
s
(
⌊
t
0
m
T
⌋
+
ϵ
)
+
Δf
,
and
vi/ synchronizing, by the telecommunications receiver device, the received IR-UWB signal according to the computed shift.
2 . The method according to claim 1 , the method further comprising:
performing, by the telecommunications receiver device, for n=0 to NP−1, a discrete Fourier transform (DFT) of the x n determined for an indexed slice k d , then determining
n
d
=
arg
max
n
0
(
max
m
❘
"\[LeftBracketingBar]"
X
m
k
d
,
n
0
❘
"\[RightBracketingBar]"
)
,
where
X
m
k
d
,
n
0
=
D
F
T
(
x
n
P
+
n
0
k
d
)
,
n
0
∈
〚
0
;
P
-
1
〛
and then determining index
m
d
∈
〚
0
;
N
-
1
〛
of the maximum of the modulus of
X
m
k
d
,
n
d
,
where
m
d
=
arg
max
m
❘
"\[LeftBracketingBar]"
X
m
k
d
,
n
d
❘
"\[RightBracketingBar]"
;
determining, by the telecommunications receiver device, an estimate, {circumflex over (f)} d , of the value of the frequency f d with
f
^
d
=
{
m
d
NT
if
m
d
<
N
2
m
d
NT
-
1
T
s
if
m
d
≥
N
2
;
performing, by the telecommunications receiver device, for n=0 to NP−1, a DFT, of the
y
n
P
+
n
d
k
g
determined for an indexed slice k g , then being given
Y
m
k
g
,
n
d
=
DFT
(
y
nP
+
n
d
k
g
)
,
n
0
∈
〚
0
;
P
-
1
〛
and determining the index m g ∈[[0; N−1]] of the maximum of the modulus of
Y
m
k
g
,
n
d
,
i.e.
m
g
=
arg
max
m
❘
"\[LeftBracketingBar]"
Y
m
k
d
,
n
d
❘
"\[RightBracketingBar]"
;
and
determining, by the telecommunications receiver device, an estimate, {circumflex over (f)} g , of the value of the frequency f g with
f
^
g
=
{
m
g
NT
if
m
g
<
N
2
m
g
NT
-
1
T
s
if
m
g
≥
N
2
.
3 . The method according to claim 2 , wherein the telecommunications receiver device determines an estimate Δ{circumflex over (f)} of the frequency shift Δf utilizing the following formula:
=
f
^
d
+
f
^
g
2
.
4 . The method according to claim 2 , wherein when m d and m g do not have the same parity, the value of that of m d and m g whose second largest Fourier-transform value is closest to the maximum is then modified, the value of the modified index being set equal to the index of this second value.
5 . The method according to claim 2 , wherein the telecommunications receiver device implements the following steps:
computing
Δφ
0
=
arg
(
X
m
d
k
d
+
1
,
n
d
conj
(
X
m
d
k
d
,
n
d
)
)
;
letting m d2 be the index neighbouring m d in a manner that
❘
"\[LeftBracketingBar]"
X
m
d
k
d
,
n
d
❘
"\[RightBracketingBar]"
and
❘
"\[LeftBracketingBar]"
X
m
d
2
k
d
,
n
d
❘
"\[RightBracketingBar]"
are spaced apart by less than a predefined value, the value of Δφ is determined by applying:
if
Δ
φ
0
<
0
and
m
d
-
m
d
2
<
0
then
Δ
φ
=
Δ
φ
0
+
2
π
,
if
Δ
φ
0
>
0
and
m
d
-
m
d
2
>
0
then
Δ
φ
=
Δ
φ
0
+
2
π
,
otherwise
Δ
φ
=
Δ
φ
0
;
and
determining an estimate Δ{circumflex over (f)} of the frequency shift Δf using the following formula:
=
f
^
d
+
f
^
g
2
+
Δφ
2
π
NT
.
6 . A non-transitory computer readable storage medium having stored thereon a computer program with code stored on said storage medium, the code, when executed by a microcomputer, causes the microcomputer to implement the steps i, ii, iii and iv of the method according to claim 1 .
7 . A device comprising:
a memory;
a processor; and
a telecommunications receiver device coupled to the memory and processor, the telecommunications receiver device configured to:
receive an impulse radio ultrawide-band (IR-UWB) signal, the IR-UWB signal comprising data packets, a data packet of the data packets comprising a preamble, the preamble comprising a first preamble portion of at least two occurrences of a first preamble sequence of N pulses spaced apart by a period T and that are each equal to a reference pulse weighted by a complex coefficient c n , n=0 to N−1 indicating a rank of the pulse in the first sequence, and the preamble further comprising a second preamble portion of at least two occurrences of a second preamble sequence equal to the complex conjugate of the first sequence;
perform an operation of synchronizing to the received IR-UWB signal according to the preamble;
sample the preamble with a sampling period T s , T=P×T s with P an integer greater than or equal to 1;
consider NP successive samples s n , for n=0 to NP−1, of a slice, of duration NT, of the first preamble portion of a received signal packet, and determine the sequence of values,
x
n
=
c
⌊
n
P
⌋
*
s
n
;
consider NP successive samples z n , for n=0 to NP−1, of a slice, of duration NT, of the second preamble portion of a received signal packet, determine the sequence of values
y
n
=
c
⌊
n
P
⌋
z
n
;
determine frequency f d of the sequence x n and frequency f g of the sequence y n with n=0 to NP−1;
compute at least one shift to be applied to synchronize to the received IR-UWB signal among a frequency shift Δf and a time shift t 0m according to the following equations:
f
d
=
1
N
P
T
s
(
⌊
t
0
m
T
⌋
+
ϵ
)
+
Δ
f
f
g
=
-
1
N
P
T
s
(
⌊
t
0
m
T
⌋
+
ϵ
)
+
Δ
f
;
and
perform a synchronization depending at least on said computed shift.
8 . The device according to claim 7 , wherein the telecommunications receiver device is configured to perform, for n=0 to NP−1, a discrete Fourier transform (DFT) of the x n determined for an indexed slice k d , then to determine
n
d
=
arg
max
n
0
(
max
m
❘
"\[LeftBracketingBar]"
X
m
k
d
,
n
0
❘
"\[RightBracketingBar]"
)
,
where
X
m
k
d
,
n
0
=
DFT
(
x
nP
+
n
0
k
d
)
,
n
0
∈
〚
0
;
P
-
1
〛
and then to determine index m d ∈[[0; N−1]] of the maximum of the modulus of
X
m
k
g
,
n
d
,
where
m
d
=
arg
max
m
❘
"\[LeftBracketingBar]"
X
m
k
d
,
n
d
❘
"\[RightBracketingBar]"
;
and
determine an estimate, {circumflex over (f)} d , of the value of the frequency f d with
f
^
d
=
{
m
d
NT
if
m
d
<
N
2
m
d
NT
-
1
T
s
if
m
d
≥
N
2
;
and said telecommunications receiver device being configured to perform, for n=0 to NP−1, a discrete Fourier transform (DFT), of the
y
n
P
+
n
d
k
g
determined for an indexed slice k g , then being given
Y
m
k
g
,
n
d
=
D
F
T
(
y
n
P
+
n
d
k
g
)
,
n 0 ∈[[0; P−1]] and then determining the index m g ∈[[0; N−1]] of the maximum of the modulus of
Y
m
k
g
n
d
,
i.e.
m
d
=
arg
max
m
❘
"\[LeftBracketingBar]"
X
m
k
d
,
n
d
❘
"\[RightBracketingBar]"
;
and
determine an estimate, {circumflex over (f)} g , of the value of the frequency f g with
f
^
g
=
{
m
g
NT
if
m
g
<
N
2
m
g
NT
-
1
T
s
if
m
g
≥
N
2
.
9 . The device according to claim 8 , configured to determine an estimate Δ{circumflex over (f)} of the frequency shift Δf utilizing the following formula:
=
f
^
d
+
f
^
g
2
.
10 . The device according to claim 8 , configured to, when m d and m g do not have the same parity, modify the value of that of m d and m g whose second largest Fourier-transform value is closest to the maximum, the value of the modified index being set equal to the index of this second value.