Carrier frequency estimation for probabilistic shaped signal
View Patent ↗In part, the disclosure relates to a method of carrier frequency estimation. The method includes selecting a first group of symbols from a constellation of a carrier signal, wherein the first group includes one or more subgroups of symbols from the constellation; estimating a carrier frequency or carrier frequency offset of the carrier signal by approximating the carrier frequency offset as Δf, wherein Δ f = 1 4 arg max ❘ "\[LeftBracketingBar]" D F T ( cos ( θ ) + j sin ( θ ) ) ❘ "\[RightBracketingBar]" ; and determining cos(θ) and sin(θ) using a coordinate rotation digital computer (CORDIC) algorithm, wherein the CORDIC algorithm calculates rotation of a two-dimensional vector by θ using add and/or shift operations.
1. A method of carrier frequency estimation comprising:
selecting a first group of symbols from a constellation of a carrier signal;
estimating a carrier frequency or carrier frequency offset of the carrier signal by approximating the carrier frequency offset as Δf; and
determining cos(θ) and sin(θ) using an algorithm, wherein the algorithm calculates rotation of a two-dimensional vector by θ, wherein Δf is determined using one or both of cos(θ) and sin(θ).
2. The method of claim 1 further comprising selecting symbols of the first group of symbols by a magnitude of a complex representation of each symbol.
3. The method of claim 1 further comprising selecting symbols of the first group of symbols by a sign of real part of fourth power of the symbol of each symbol, wherein one or more symbols are a complex number.
4. The method of claim 1 , wherein all steps of claim 1 are performed by a DSP that is in electrical communication with a symbol rate receiver.
5. The method of claim 4 , wherein e jθ is evaluated as a step in the algorithm.
6. The method of claim 5 , wherein values for e jθ are obtained by a DSP from a look up table stored in memory, wherein the memory is in electrical communication with the DSP and a receiver.
7. The method of claim 1 , wherein
Δ
f
=
1
4
arg
max
❘
"\[LeftBracketingBar]"
DFT
(
cos
(
θ
)
+
j
sin
(
θ
)
)
❘
"\[RightBracketingBar]"
.
8. The method of claim 1 , wherein
Δ
f
=
1
4
arg
max
❘
"\[LeftBracketingBar]"
DFT
(
e
j
θ
)
❘
"\[RightBracketingBar]"
.
9. The method of claim 1 wherein the first group includes one or more subgroups of symbols from the constellation.
10. The method of claim 9 wherein the one or more subgroups includes a plurality of corner symbols, wherein the estimating and determining step are performed in real time.
11. The method of claim 10 further comprising selecting symbols of the first group of symbols from first radius of the constellation.
12. The method of claim 1 wherein the algorithm is a coordinate rotation digital computer (CORDIC) algorithm.
13. The method of claim 12 further comprising estimating phase angle θ of first group of symbols wherein θ=angle(y 4 ) using CORDIC algorithm to generate cos(θ) and sin(θ) using a DSP in electrical communication with a receiver, wherein |y| 2 is in a first region of constellation.
14. The method of claim 12 further comprising estimating phase angle θ of first group of symbols wherein θ=(angle(y 4 )+π) using CORDIC algorithm to generate cos(θ)and sin(θ) using a DSP in electrical communication with a receiver, wherein |y| 2 is in a second region of constellation.
15. The method of claim 12 , wherein the CORDIC algorithm is performed using a DSP.
16. The method of claim 15 , wherein the DSP is a coherent DSP.
17. The method of claim 15 , wherein the DSP is in electrical communication with a receiver.
18. The method of claim 15 , wherein the DSP is a symbol rate DSP.
19. The method of claim 12 , wherein CORDIC algorithm is configured not to perform division or multiplication operations to maintain real time operation.
20. A method of carrier frequency estimation comprising:
selecting a first group of symbols from a constellation of a carrier signal, wherein the first group includes one or more subgroups of symbols from the constellation;
estimating a carrier frequency or carrier frequency offset of the carrier signal by approximating the carrier frequency offset as Δf, wherein Δf is a function of θ; and
determining cos(θ) and sin(θ).
21. The method of claim 20 wherein cos(θ) and sin(θ) are determined using an algorithm, wherein the algorithm is a CORDIC algorithm, wherein the CORDIC algorithm calculates rotation of a two-dimensional vector by θ.
22. A method of carrier frequency estimation comprising:
selecting a first group of symbols from a constellation of a carrier signal;
determining a rotation of a two-dimensional vector by θ; and
estimating a carrier frequency or carrier frequency offset of the carrier signal by approximating the carrier frequency offset as Δf, wherein Δf is a function of θ.