Calculating an EVM of an antenna port
Apparatuses, methods, and systems are disclosed for calculating an EVM of a transmitter. One apparatus includes a processor and a receiver that receives a signal via a propagation channel from an antenna port at a transmitter, the antenna port comprising multiple antennas and with an antenna connector for each antenna. The processor measures the received signal using an unbiased linear MMSE equalizer and calculates an EVM of the antenna port, where the EVM is calculated as 100 times the square root of the mean square error of the symbol estimate at the output of the unbiased linear MMSE equalizer.
1. An evaluation apparatus comprising:
at least one memory; and
at least one processor coupled with the at least one memory and configured to cause the evaluation apparatus to:
receive a signal via a propagation channel from an antenna port at a transmitter, the antenna port comprising a plurality of antennas, wherein each antenna of the plurality of antennas has a respective antenna connector from a plurality of antenna connectors;
measure the received signal using an unbiased linear minimum mean square error (“MMSE”) equalizer; and
calculate an error vector magnitude (“EVM”) of the antenna port based at least in part on the received signal and an output of the unbiased linear MMSE equalizer, wherein the EVM is calculated as
EVM=100·√{square root over (( w H Σ −1 w ) −1 )},
where w denotes a vector of gains measured at a plurality of antenna connectors and Σ denotes a noise covariance vector as measured at the plurality of antenna connectors.
2. The evaluation apparatus of claim 1 , wherein an EVM definition used to calculate the EVM of the antenna port is independent of the propagation channel when a channel matrix H of the propagation channel is invertible.
3. The evaluation apparatus of claim 2 , wherein the EVM definition used to calculate the EVM of the antenna port is a function of a precoding matrix associated with the received signal.
4. The evaluation apparatus of claim 1 , wherein the received signal is received using a same number of antennas as comprises the antenna port at the transmitter.
5. The evaluation apparatus of claim 1 , wherein the EVM of the antenna port is calculated as
E
V
M
=
(
EVM
1
)
2
(
EVM
2
)
2
(
EVM
1
)
2
+
(
EVM
2
)
2
,
if the noise between antenna connectors is uncorrelated, where EVM 1 is a respective EVM measured at a first antenna connector and where EVM 2 is a respective EVM measured at a second antenna connector.
6. The evaluation apparatus of claim 1 , wherein the transmitter comprises a user equipment (“UE”) for transmitting uplink signals to a base station, wherein the at least one processor is configured to cause the evaluation apparatus to define a noise floor of the base station due to transmitter noise using the calculated EVM.
7. A method performed by an evaluation device, the method comprising:
receiving a signal via a propagation channel from an antenna port at a transmitter, the antenna port comprising a plurality of antennas, wherein each antenna of the plurality of antennas has a respective antenna connector from a plurality of antenna connectors;
measuring the received signal using an unbiased linear minimum mean square error (“MMSE”) equalizer; and
calculating an error vector magnitude (“EVM”) of the antenna port based at least in part on the received signal and an output of the unbiased linear MMSE equalizer, wherein the EVM is calculated as
EVM=100·√{square root over (( w H Σ −1 w ) −1 )},
where w denotes a vector of gains measured at a plurality of antenna connectors and Σ denotes a noise covariance vector as measured at the plurality of antenna connectors.
8. The method of claim 7 , wherein an EVM definition used to calculate the EVM of the antenna port is independent of the propagation channel when a channel matrix H of the propagation channel is invertible.
9. The method of claim 8 , wherein the EVM definition used to calculate the EVM of the antenna port is a function of a precoding matrix associated with the received signal.
10. The method of claim 7 , wherein the received signal is received at the unbiased linear MMSE equalizer using a same number of antennas as comprises the antenna port at the transmitter.
11. The method of claim 7 , wherein the EVM of the antenna port is calculated as
E
V
M
=
(
EVM
1
)
2
(
EVM
2
)
2
(
EVM
1
)
2
+
(
EVM
2
)
2
,
if the noise between antenna connectors is uncorrelated, where EVM 1 is a respective EVM measured at a first antenna connector and where EVM 2 is a respective EVM measured at a second antenna connector.
12. The method of claim 7 , wherein the transmitter comprises a user equipment (“UE”) for transmitting uplink signals to a base station, the method further comprising defining a noise floor of the base station due to transmitter noise using the calculated EVM.
13. A system comprising:
a transmitting device that:
generates a single-layer Multiple-Input, Multiple-Output (“MIMO”) signal; and
transmits the single-layer MIMO signal via a propagation channel using a transmitter;
an evaluation device that:
receives the single-layer MIMO signal using an unbiased linear minimum mean square error (“MMSE”) equalizer; and
calculates an error vector magnitude (“EVM”) of the transmitter based at least in part on the single-layer MIMO signal and an output of the unbiased linear MMSE equalizer, wherein the EVM is calculated as
EVM=100·√{square root over (( w H Σ −1 w ) −1 )},
where w denotes a vector of gains measured at a plurality of antenna connectors and Σ denotes a noise covariance vector as measured at the plurality of antenna connectors.
14. The system of claim 13 , wherein an EVM definition used to calculate the EVM is independent of the propagation channel when a channel matrix H of the propagation channel is invertible.
15. The system of claim 14 , wherein the EVM definition used to calculate the EVM of the transmitter is a function of a precoding matrix used to generate the single-layer MIMO signal.
16. The system of claim 13 , wherein the single-layer MIMO signal is received at the unbiased linear MMSE equalizer using a same number of antennas as comprises an antenna port of the transmitter.
17. The system of claim 13 , wherein the EVM is calculated as
E
V
M
=
(
EVM
1
)
2
(
EVM
2
)
2
(
EVM
1
)
2
+
(
EVM
2
)
2
,
if the noise between a plurality of antenna connectors is uncorrelated, where EVM 1 is a first respective EVM measured at a first antenna connector and where EVM 2 is a second respective EVM measured at a second antenna connector.