US 11,075,669 B2 · M-ary differential chaos shift keying method based on chaotic shape-forming filter

Abstract

The present disclosure discloses an M-ary DCSK method based on chaotic shape-forming filtering. The method includes the following steps: at S1, parameters of a communication system are set; at S2, HP information and LP information to be sent in each time slot are prepared; at S3, the information to be sent is modulated; at S4, a chaotic carrier is generated through a chaotic shape-forming filter; at S5, a transmitted signal is prepared; at S6, down-carrier frequency and matched filter is performed to a received signal; at S7, the sampling of a maximum SNR point is performed to an output signal of a matched filter; at S8, the decision of high priority information bits is resumed; and at S9, the decision of low priority information bits is resumed.

An M-ary Differential Chaos Shift Keying (DCSK) method based on chaotic shape-forming filter, comprising:

Step 1, setting parameters of a communication system;
when a signal base frequency of a chaotic shape-forming filter is f, an order of a Walsh code matrix is D, a spreading gain is L, sending High Priority (HP) information bits and Low Priority (LP) information bits in each transmission time slot, wherein the number of the HP information bits is l=log2 D, and the number of the LP information bits Ns=L/D;
Step 2, preparing bit information to be sent;
Step 3, modulating the bit information to be sent;
Step 4, generating a chaotic carrier through a chaotic shape-forming filter;
Step 5, preparing a transmitted signal;
Step 6, performing down-carrier and matched filter to a received signal;
wherein after a signal of a transmitting end is transmitted through a wireless channel, a received signal r(t) of a receiving end is equal to T(t)+w(t), T(t) is the signal of the transmitting end, w(t) is channel noise, a down-carrier signal v(t) is obtained by performing digital down-carrier processing to the received signal r(t), and an expression of the v(t) is:
v(t)=r(t)·sin(2πfct)=(T(t)+w(t))·sin(2πfct);
wherein the down-carrier signal v(t) is sent to a matched filter to obtain an output signal ξ(t) of the matched filter, and the expression of the ξ(t) is:
ξ
⁡
(
t
)
=
∑
m
=
⌈
t
⌉
-
n
s
·
N
p
⌈
t
⌉
⁢
v
⁡
(
t
)
·
g
⁡
(
t
-
m
)
;
wherein t is a system time, v(t) is an input signal of the matched filter, which is also called a digital down-carrier signal, ┌t┐ is the smallest integer greater than and equal to the system time t, g(t)=p(−t) is a time inverse function of a chaotic basis function p(t), g(t−m) is an input value of the function g(t) at the moment t−m, and ns is an oversampling ratio of a chaotic symbol;
Step 7, performing down-sampling to the output signal of the matched filter;
wherein the output signal ξ(t) of the matched filter is sent to a down-sampling component, the maximum Signal-to-Noise Ratio (SNR) point sampling is performed to the output signal ξ(t) of the matched filter according to an interval t=n/f;
and an expression of a maximum SNR sampling point q(n) is:
q
⁡
(
n
)
=
ξ
⁡
(
(
n
-
1
)
f
+
1
2
⁢
f
)
⁢
⁢
1
≤
n
≤
D
·
N
s
;
wherein 1≤n≤D·Ns is the nth maximum SNR sampling point, and D·Ns maximum SNR sampling points form a maximum SNR sampling sequence, which is expressed as q=[q(1), q(2), . . . , q(D·Ns)];
Step 8, performing recovery decision to high priority information bits;
wherein elements in the maximum SNR sampling point sequence q are respectively multiplied by and added to each row of the Walsh code matrix, and a summing output result of the element j(1≤j≤Ns) in a row α (1≤α≤D) is:
A
α
⁡
(
j
)
=
∑
k
=
1
D
⁢
(
q
⁡
(
(
k
-
1
)
·
N
s
+
j
)
·
w
α
,
k
)
;
wherein an output result of a signal summation component 10 in the row α is:
Aα=[Aα(1),Aα(2), . . . ,Aα(Ns)];
wherein the output result of the signal summation component is sent to an energy summation component to calculate an energy sum of the row α, and the expression is:
E
α
=
∑
j
=
1
N
s
⁢
A
α
2
⁡
(
j
)
;
wherein the output results of D energy summation components are sent to a maximum likelihood decision component, by comparing the summation results of the D energy summation components, the group with the largest sum of Eα is selected according to a maximum likelihood decision rule, a recovered high priority decimal number is set as {circumflex over (d)}=α, and the decimal number is recovered to the high priority information bits {circumflex over (B)}lHP=({circumflex over (b)}1HP, {circumflex over (b)}2HP, . . . , blHP) according to inverse mapping;
Step 9, performing the recovery decision to low priority information bits;
wherein the recovered high priority {circumflex over (d)} is sent to a selector, a corresponding output result of the signal summation component in the row α={circumflex over (d)} is selected and sent to a symbol decision component, and a low priority bipolar symbol is recovered according to the following formula:
y
^
j
=
{
+
1
,
A
d
^
⁡
(
j
)
>
0
-
1
,
A
d
^
⁡
(
j
)
≤
0
,
1
≤
j
≤
N
s
;
wherein a bipolar decision symbol is recovered to unipolar low priority information bits {circumflex over (B)}NsLP=({circumflex over (b)}1LP, {circumflex over (b)}2LP, . . . , {circumflex over (b)}NsLP) through an S/B transform:
b
^
j
LP
=
{
1
,
y
^
j
=
+
1
0
,
y
^
j
=
-
1
,
1
≤
j
≤
N
s
;
Ending.

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M-ary differential chaos shift keying method based on chaotic shape-forming filter

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M-ary differential chaos shift keying method based on chaotic shape-forming filter

Life of this patent

Abstract

Claims5