Calculating an EVM of a transmitter
Apparatuses, methods, and systems are disclosed for calculating an EVM of a transmitter. One apparatus includes a processor and a receiver that receives a multiple-layer MIMO signal from a transmitter via a propagation channel. The processor measures the received multiple-layer MIMO signal using an unbiased linear MMSE MIMO equalizer and calculates an EVM of the transmitter, where the EVM for each transmission layer is calculated as 100 times the square root of the mean square error of the layer estimate at the output of the unbiased linear MMSE MIMO 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 multiple-layer Multiple-Input, Multiple-Output (“MIMO”) signal from a transmitter via a propagation channel;
measure the multiple-layer MIMO signal using an unbiased linear minimum mean square error (“MMSE”) MIMO equalizer; and
calculate an error vector magnitude (“EVM”) of the transmitter based on a noise covariance matrix for the unbiased linear MMSE MIMO equalizer and further based on a plurality of per-layer EVM values corresponding to the multiple-layer MIMO signal, wherein the per-layer EVM value for each transmission layer is calculated as 100 times a square root of a mean square error of a layer estimate at an output of the unbiased linear MMSE MIMO equalizer.
2 . The evaluation apparatus of claim 1 , wherein an EVM definition used to calculate the plurality of per-layer EVM values of the transmitter 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 plurality of per-layer EVM values of the transmitter is a function of a precoding matrix associated with the multiple-layer MIMO signal.
4 . The evaluation apparatus of claim 1 , wherein the multiple-layer MIMO signal corresponds to a two-layer MIMO transmission, wherein the mean square error for each transmission layer is a function of the covariance of transmitter noise of the transmitter.
5 . The evaluation apparatus of claim 4 , wherein the per-layer EVM value of a first transmission layer is calculated as
EVM
1
=
100
·
1
❘
"\[LeftBracketingBar]"
Q
1.1
❘
"\[RightBracketingBar]"
2
(
❘
"\[LeftBracketingBar]"
Q
1
,
2
❘
"\[RightBracketingBar]"
2
+
P
1
,
1
)
,
wherein the per-layer EVM value of a second transmission layer is calculated as
EVM
2
=
100
·
1
❘
"\[LeftBracketingBar]"
Q
2
,
2
❘
"\[RightBracketingBar]"
2
(
❘
"\[LeftBracketingBar]"
Q
2
,
1
❘
"\[RightBracketingBar]"
2
+
P
2
,
2
)
,
wherein the values Q 1,1 , Q 1,2 , Q 2,1 , Q 2,2 , form a matrix Q which denotes the unbiased linear MMSE MIMO equalizer, and wherein the values P 1,1 , P 2,2 , are values from a matrix P which denotes the noise covariance matrix.
6 . The evaluation apparatus of claim 1 , wherein the transmitter comprises a User Equipment (“UE”) for transmitting uplink MIMO 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 based at least in part on the calculated EVM.
7 . The evaluation apparatus of claim 1 , wherein the multiple-layer MIMO signal comprises per-layer reference symbols or per-antenna reference symbols.
8 . A method for calculating an error vector magnitude (“EVM”) of a transmitter, the method comprising:
receiving a multiple-layer Multiple-Input, Multiple-Output (“MIMO”) signal from a transmitter via a propagation channel;
measuring the multiple-layer MIMO signal using an unbiased linear minimum mean square error (“MMSE”) MIMO equalizer; and
calculating an error vector magnitude (“EVM”) of the transmitter based on a noise covariance matrix for the unbiased linear MMSE MIMO equalizer and further based on a plurality of per-layer EVM values corresponding to the multiple-layer MIMO signal, wherein the per-layer EVM value for each transmission layer is calculated as 100 times a square root of a mean square error of a layer estimate at an output of the unbiased linear MMSE MIMO equalizer.
9 . The method of claim 8 , wherein an EVM definition used to calculate the plurality of per-layer EVM values of the transmitter is independent of the propagation channel when a channel matrix H of the propagation channel is invertible.
10 . The method of claim 9 , wherein the EVM definition used to calculate the plurality of per-layer EVM values of the transmitter is a function of a precoding matrix associated with the multiple-layer MIMO signal.
11 . The method of claim 8 , wherein the multiple-layer MIMO signal corresponds to a two-layer MIMO transmission, wherein the mean square error for each transmission layer is a function of the covariance of transmitter noise of the transmitter.
12 . The method of claim 11 , wherein the plurality of per-layer EVM values of a first transmission layer is calculated as
EVM
1
=
100
·
1
❘
"\[LeftBracketingBar]"
Q
1.1
❘
"\[RightBracketingBar]"
2
(
❘
"\[LeftBracketingBar]"
Q
1
,
2
❘
"\[RightBracketingBar]"
2
+
P
1
,
1
)
,
wherein the plurality of per-layer EVM values of a second transmission layer is calculated as
EVM
2
=
100
·
1
❘
"\[LeftBracketingBar]"
Q
2
,
2
❘
"\[RightBracketingBar]"
2
(
❘
"\[LeftBracketingBar]"
Q
2
,
1
❘
"\[RightBracketingBar]"
2
+
P
2
,
2
)
,
wherein the values Q 1,1 , Q 1,2 , Q 2,1 , Q 2,2 , form a matrix Q which denotes the unbiased linear MMSE MIMO equalizer, and wherein the values P 1,1 , P 2,2 , are values from a matrix P which denotes the noise covariance matrix.
13 . The method of claim 8 , wherein the transmitter comprises a User Equipment (“UE”) for transmitting uplink MIMO signals to a base station, the method further comprising defining a noise floor of the base station due to transmitter noise based at least in part on the calculated EVM.
14 . The method of claim 8 , wherein the generated multiple-layer MIMO signal comprises per-layer reference symbols or per-antenna reference symbols.
15 . A system comprising:
a transmitting device that:
generates a multiple-layer transmission signal for Multiple-Input, Multiple-Output (“MIMO”); and
transmits the generated multiple-layer transmission signal via a propagation channel using a transmitter; and
an evaluation device that:
measures the transmitted multiple-layer transmission signal using an unbiased linear minimum mean square error (“MMSE”) MIMO equalizer; and
calculates an error vector magnitude (“EVM”) of the transmitter based on a noise covariance matrix for the unbiased linear MMSE MIMO equalizer and further based on a plurality of per-layer EVM values corresponding to the multiple-layer MIMO signal, wherein the per-layer EVM value for each transmission layer is calculated as 100 times a square root of a mean square error of a layer estimate at an output of the unbiased linear MMSE MIMO equalizer.
16 . The system of claim 15 , wherein an EVM definition used to calculate the plurality of per-layer EVM values of the transmitter is independent of the propagation channel when a channel matrix H of the propagation channel is invertible.
17 . The system of claim 16 , wherein the EVM definition used to calculate the plurality of per-layer EVM values of the transmitter is a function of a precoding matrix used to generate the multiple-layer transmission signal.
18 . The system of claim 15 , wherein the multiple-layer transmission comprises a two-layer MIMO transmission, wherein the mean square error for each transmission layer is a function of the covariance of transmitter noise of the transmitter.
19 . The system of claim 18 , wherein the plurality of per-layer EVM values of a first transmission layer is calculated as
EVM
1
=
100
·
1
❘
"\[LeftBracketingBar]"
Q
1.1
❘
"\[RightBracketingBar]"
2
(
❘
"\[LeftBracketingBar]"
Q
1
,
2
❘
"\[RightBracketingBar]"
2
+
P
1
,
1
)
,
wherein the plurality of per-layer EVM values of a second transmission layer is calculated as
EVM
2
=
100
·
1
❘
"\[LeftBracketingBar]"
Q
2
,
2
❘
"\[RightBracketingBar]"
2
(
❘
"\[LeftBracketingBar]"
Q
2
,
1
❘
"\[RightBracketingBar]"
2
+
P
2
,
2
)
,
wherein the values Q 1,1 , Q 1,2 , Q 2,1 , Q 2,2 , form a matrix Q which denotes the unbiased linear MMSE MIMO equalizer, and wherein the values P 1,1 , P 2,2 , are values from a matrix P which denotes the noise covariance matrix.
20 . The system of claim 15 , wherein the generated multiple-layer transmission signal comprises per-layer reference symbols or per-antenna reference symbols.