Multiple receivers in an OFDM/OFDMA communication system
View Patent ↗A signal receiver is configured to receive multiple time-domain input signals. A plurality of the input signals among the multiple time-domain input signals is selected and transformed into frequency-domain signals. The frequency-domain signals is shifted in phase by a negative value of a respective reference phase, and the phase-shifted signals is combined into one signal. The combined signal is then multiplied with a stored signal to generate a signal product and transformed into a time-domain signal.
1. A signal detection method by a wireless device comprising multiple receivers, each receiver coupled to an antenna and configured to receive a signal from a same transmitting device via a propagation channel, the method comprising:
selecting a plurality of the received signals from said multiple receivers;
transforming the selected signals into frequency-domain signals;
shifting each of the frequency-domain signals in phase by a negative value of a respective reference phase;
combining the phase-shifted signals into one signal, wherein the combined signal is represented by {S(n l )} l=1 L ;
circularly shifting the combined signal by m subcarrier spacings in accordance with
S
m
(
n
l
)
=
{
S
(
n
l
+
m
)
if
n
l
≤
L
2
-
m
S
(
L
2
-
n
l
-
m
)
if
n
l
>
L
2
-
m
,
wherein m is an integer;
multiplying the circularly shifted signal with a signal stored in a storage in the device to generate a signal product;
transforming the signal product into a time-domain signal; and
performing peak detection on the time-domain signal.
2. The method of claim 1 , wherein the respective reference phase is represented by φ and is set to a phase value at an n 0 -th frequency subcarrier φ(n 0 ) of the signal to be phase-shifted.
3. The method of claim 1 , wherein the respective reference phase is represented by φ and is set to the value of a first-order phase approximation at an n 0 -th frequency subcarrier φ (n 0 ) of the signal to be phase-shifted, wherein the first-order phase approximation is given by φ (n l )=a+bn l , where n l represents the subcarrier index and coefficients a and b are determined by solving normal equations
aL
+
b
∑
l
=
1
L
n
l
=
∑
l
=
1
L
ϕ
(
n
l
)
a
∑
l
=
1
L
n
l
+
b
∑
l
=
1
L
n
l
2
=
∑
l
=
1
L
n
l
ϕ
(
n
l
)
where φ(n l ) represents the phase at the n l -th frequency subcarrier of the signal to be phase-shifted and L is the length of the signal to be phase-shifted.
4. The method of claim 1 , wherein each of the frequency-domain signals is weighted with a corresponding weight before being phase-shifted.
5. The method of claim 4 , wherein the corresponding weight is associated with a measure of the signal to be weighted, wherein the measure is
a received signal strength indication (RSSI);
a signal to noise ratio (SNR);
an average power level;
a temporal correlation coefficient;
a spatial correlation coefficient;
or a combination thereof.
6. A signal detector in a wireless device comprising multiple receivers, each receiver coupled to an antenna and configured to receive a signal from a same transmitting device via a propagation channel, the detector comprising:
means for selecting a plurality of received signals from said multiple receivers;
means for transforming the selected signals into frequency-domain signals;
means for shifting each of the frequency-domain signals in phase by a negative value of a respective reference phase;
means for combining the phase-shifted signals into one signal, wherein the combined signal is represented by {S(n l )} l=1 L ;
means for circularly shifting the combined signal by m subcarrier spacings in accordance with
S
m
(
n
l
)
=
{
S
(
n
l
+
m
)
if
n
l
≤
L
2
-
m
S
(
L
2
-
n
l
-
m
)
if
n
l
>
L
2
-
m
,
wherein m is an integer;
means for multiplying the circularly shifted signal with a signal stored in a storage in the device;
means for transforming the signal product into a time-domain signal; and
means for performing a peak detection on the time-domain signal.
7. A non-transitory computer readable storage medium storing thereon computer executable instructions for signal detection by a wireless device comprising multiple receivers, each receiver coupled to an antenna and configured to receive a signal from a same transmitting device via a propagation channel, the computer readable storage medium comprising:
instructions for selecting a plurality of received signals from said multiple receivers;
instructions for transforming the selected signals into frequency-domain signals;
instructions for shifting each of the frequency-domain signals in phase by a negative value of a respective reference phase;
instructions for combining the phase-shifted signals into one signal, wherein the combined signal is represented by {S(n l )} l=1 L ;
instructions for circularly shifting the combined signal by m subcarrier spacings in accordance with
S
m
(
n
l
)
=
{
S
(
n
l
+
m
)
if
n
l
≤
L
2
-
m
S
(
L
2
-
n
l
-
m
)
if
n
l
>
L
2
-
m
,
wherein m is an integer;
instructions for multiplying the circularly shifted signal with a signal stored in a storage in the device;
instructions for transforming the signal product into a time-domain signal; and
instructions for performing a peak detection on the time-domain signal.
8. A mobile device comprising multiple receivers, each receiver coupled to an antenna and configured to receive a signal from a same transmitting device via a propagation channel, the mobile device configured to:
select a plurality of the received signals from said multiple receivers;
transform the selected signals into frequency-domain signals;
shift each of the frequency-domain signals in phase by a negative value of a respective reference phase;
combine the phase-shifted signals into one signal, wherein the combined signal is represented by {S(n l )} l=1 L ;
circularly shift the combined signal by m subcarrier spacings in accordance with
S
m
(
n
l
)
=
{
S
(
n
l
+
m
)
if
n
l
≤
L
2
-
m
S
(
L
2
-
n
l
-
m
)
if
n
l
>
L
2
-
m
,
wherein m is an integer;
multiply the circularly shifted signal with a signal stored in a storage in the device to generate a signal product;
transform the signal product into a time-domain signal; and
perform peak detection on the time-domain signal.
9. The mobile device of claim 8 , wherein the respective reference phase is represented by φ and is set to a phase value at an n 0 -th frequency subcarrier φ(n 0 ) of the signal to be phase-shifted.
10. The mobile device of claim 8 , wherein the respective reference phase is represented by φ and is set to the value of a first-order phase approximation at an n 0 -th frequency subcarrier φ (n 0 ) of the signal to be phase-shifted, wherein the first-order phase approximation is given by φ (n l )=a+bn l , where n l represents the subcarrier index and coefficients a and b are determined by solving normal equations
aL
+
b
∑
l
=
1
L
n
l
=
∑
l
=
1
L
ϕ
(
n
l
)
a
∑
l
=
1
L
n
l
+
b
∑
l
=
1
L
n
l
2
=
∑
l
=
1
L
n
l
ϕ
(
n
l
)
where φ(n l ) represents the phase at the n l -th frequency subcarrier of the signal to be phase-shifted and L is the length of the signal to be phase-shifted.
11. The mobile device of claim 8 , wherein each of the frequency-domain signals is weighted with a corresponding weight before being phase-shifted.
12. The mobile device of claim 11 , wherein the corresponding weight is associated with a measure of the signal to be weighted, wherein the measure is
a received signal strength indication (RSSI);
a signal to noise ratio (SNR);
an average power level;
a temporal correlation coefficient;
a spatial correlation coefficient;
or a combination thereof.
13. A signal processing method by a signal receiver configured to receive multiple time-domain input signals, the method comprising:
receiving multiple time-domain input signals by said signal receiver;
selecting a plurality of the input signals among the multiple time-domain input signals;
transforming the selected signals into frequency-domain signals;
shifting each of the frequency-domain signals in phase by a negative value of a respective reference phase;
combining the phase-shifted signals into one signal;
multiplying the combined signal with a reference signal to generate a signal product, wherein the reference signal is represented by {c(n l )} l=1 L and circularly shifted by one or more subcarrier spacings in accordance with
c
m
(
n
l
)
=
{
c
(
n
l
+
m
)
if
n
l
≤
L
2
-
m
c
(
L
2
-
n
l
-
m
)
if
n
l
>
L
2
-
m
,
wherein m is an integer; and
transforming the signal product into a time-domain signal.
14. The method of claim 13 , wherein each of the frequency-domain signals is weighted with a corresponding weight before being phase-shifted.
15. The method of claim 14 , wherein the corresponding weight is associated with a measure of the signal to be weighted, wherein the measure is
a received signal strength indication (RSSI);
a signal to noise ratio (SNR);
an average power level;
a temporal correlation coefficient;
a spatial correlation coefficient;
or a combination thereof.
16. A mobile device comprising a signal receiver configured to receive multiple time-domain input signals, the mobile device configured to:
receiving multiple time-domain input signals by said signal receiver;
select a plurality of the input signals among the multiple time-domain input signals;
transform the selected signals into frequency-domain signals;
shift each of the frequency-domain signals in phase by a negative value of a respective reference phase;
combine the phase-shifted signals into one signal;
multiply the combined signal with a reference signal to generate a signal product wherein the reference signal is represented by {c(n l )} l=1 L and circularly shifted by one or more subcarrier spacings in accordance with
c
m
(
n
l
)
=
{
c
(
n
l
+
m
)
if
n
l
≤
L
2
-
m
c
(
L
2
-
n
l
-
m
)
if
n
l
>
L
2
-
m
,
wherein m is an integer; and
transform the signal product into a time-domain signal.