US2013142057A1PendingUtilityA1
Control Channel Acquisition
Est. expiryDec 1, 2031(~5.4 yrs left)· nominal 20-yr term from priority
Inventors:Arkady Molev-Shteiman
H04W 36/18H04W 56/002H03M 13/3723H03M 13/3905H03M 13/3972H04L 1/005
52
PatentIndex Score
0
Cited by
0
References
0
Claims
Abstract
Disclosed are various embodiments of control channel acquisition systems and methods. A baseband processor in communication with the RF transceiver performs an initial detection of a carrier frequency based on GMSK symbols in the FCCH. The initial detection is refined and verified by passing a signal through a mathematical filter and comparing an energy of the filtered signal to a threshold.
Claims
exact text as granted — not AI-modifiedTherefore, having thus described the invention, at least the following is claimed:
1 . A mobile device comprising:
a radio frequency (RF) transceiver; a baseband processor in communication with the RF transceiver, the baseband processor executing a frequency correction channel (FCCH) acquisition module, the FCCH acquisition module comprising:
logic that performs an initial detection of a carrier frequency based on a plurality of GMSK symbols in the FCCH;
logic that refines the initial detection of the carrier frequency, wherein the refined initial detection downsamples the GMSK symbols by at least a factor of four; and
logic that verifies the refined initial detection of the carrier frequency by passing a signal through a mathematical filter and comparing an energy of the filtered signal to a threshold.
2 . The mobile device of claim 1 , wherein a set of samples is selected from the GMSK symbols.
3 . The mobile device of claim 2 , wherein the logic that performs an initial detection of the FCCH transmission frequency further comprises:
logic that performs a fast Fourier transform on the set of samples; logic that calculates a total signal energy associated with a plurality of frequency bins resulting from the fast Fourier transform, wherein each of the frequency bins is associated with a frequency; logic that selects a subset of the frequency bins; and logic that calculates an energy of each of the selected subset of frequency bins and selects one of the selected subset of frequency bins associated with an energy value above a threshold as an initial frequency estimate.
4 . The mobile device of claim 3 , wherein the logic that selects one of the frequency bins further comprises logic that determines whether a pair of consecutive frequency bins is associated with an energy value above the threshold and designating a frequency range associated with the pair of consecutive frequency bins.
5 . The mobile device of claim 3 , wherein the plurality of frequency bins comprises thirty-two frequency bins, and the logic selects a subset of the frequency bins further comprises logic that selects a fourth through the twelfth frequency bins.
6 . The mobile device of claim 1 , wherein the logic that refines the initial detection of the carrier frequency further comprises:
logic that derotates the initial detection; and logic that downsamples the initial detection by summing a plurality of four consecutive GMSK symbols to produce a set of samples of the GMSK symbols.
7 . The mobile device of claim 6 , wherein the logic that downsamples the initial detection downsamples the initial detection by a factor of four.
8 . The mobile device of claim 6 , further comprising logic that performs an autocorrelation of the downsampled initial detection.
9 . The mobile device of claim 8 , further comprising logic that generates a first frequency estimation of the autocorrelated downsampled initial detection by executing a frequency estimation function:
F
EST
=
F
SYM
2
·
π
·
M
·
arctan
[
1
N
·
∑
n
=
0
N
-
1
Y
(
n
)
·
Y
*
(
n
+
M
)
]
where F EST is the first frequency estimation, F SYM =270.8333 KHz, Y is a first vector representing the autocorrected downsampled initial detection, and M and N are frequency estimation parameters.
10 . The mobile device of claim 9 , wherein M=4 and N=26.
11 . The mobile device of claim 10 , further comprising:
logic that performs a derotation of the first frequency estimates; logic executes the frequency estimation function to generate a second frequency estimate, wherein M=10 and N=20; and logic that performs a derotation of the second frequency estimate to generate the refined initial estimate.
12 . The mobile device of claim 11 , wherein the mathematical filter comprises a mathematical filter function:
1
N
∑
n
=
0
N
-
1
X
(
n
)
·
exp
(
-
2
j
·
π
·
FrEstim
·
n
)
2
1
N
∑
n
=
0
N
-
1
X
(
n
)
2
>
Thr
where X(n) is the downsampled initial detection, N is a number of samples in the downsampled initial detection, FrEstim is the refined initial estimate, and Thr is the threshold.
13 . A method executed in a mobile device for acquiring a carrier frequency from a frequency correction channel (FCCH), comprising:
performing an initial detection of the carrier frequency based on a plurality GMSK symbols in the FCCH; refining the initial detection of the carrier frequency, wherein the refined initial detection downsamples the GMSK symbols by at least a factor of four; and verifying the refined initial detection of the carrier frequency by passing a signal through a mathematical filter and comparing an energy of the filtered signal to a threshold. Attorney Docket: 50228 - 7220
14 . The method of claim 13 , wherein a set of samples is selected from the GMSK symbols and the step of performing an initial detection of the carrier frequency further comprises:
performing a fast Fourier transform on the set of samples; calculating a total signal energy associated with a plurality of frequency bins resulting from the fast Fourier transform, wherein each of the frequency bins is associated with a frequency; selecting a subset of the frequency bins; and calculating an energy of each of the selected subset of frequency bins and selects one of the selected subset of frequency bins associated with an energy value above a threshold as an initial frequency estimate.
15 . The method of claim 14 , wherein the step of selecting one of the frequency bins further comprises the step of determining whether a pair of consecutive frequency bins is associated with an energy value above the threshold and designating a frequency range associated with the pair of consecutive frequency bins.
16 . The method of claim 14 , wherein the plurality of frequency bins comprises thirty-two frequency bins, and the step of selecting a subset of the frequency bins further comprises logic that selects a fourth through the twelfth frequency bins.
17 . The method of claim 13 , wherein the step of refining the initial detection of the carrier frequency further comprises:
derotating the initial detection; and downsampling the initial detection by a factor of four.
18 . The method of claim 17 , further comprising:
performing an autocorrelation of the downsampled initial detection; generating a first frequency estimation of the autocorrelated downsampled initial detection by executing a frequency estimation function; performing a derotation of the first frequency estimation; generating a second frequency estimation by executing the frequency estimation function; and performing a derotation of the second frequency estimation to generate the refined initial estimate.
19 . The method of claim 13 , wherein the mathematical filter comprises a mathematical filter function:
1
N
∑
n
=
0
N
-
1
X
(
n
)
·
exp
(
-
2
j
·
π
·
FrEstim
·
n
)
2
1
N
∑
n
=
0
N
-
1
X
(
n
)
2
>
Thr
where X(n) is the downsampled initial detection, N is a number of samples in the downsampled initial detection, FrEstim is the refined initial estimate, and Thr is the threshold.
20 . A system, comprising:
means performing an initial detection of the carrier frequency based on a plurality GMSK symbols in a frequency correction channel (FCCH); means for refining the initial detection of the carrier frequency, wherein the refined initial detection downsamples the GMSK symbols by at least a factor of four; and means for verifying the refined initial detection of the carrier frequency by passing a signal through a mathematical filter and comparing an energy of the filtered signal to a threshold.Join the waitlist — get patent alerts
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