Method and apparatus including definition and testing of error vector magnitude

Abstract

A method and apparatus are provided in which a data sequence for transmission is identified (1002) as part of evaluating transmitter performance involving a plurality of physical antennas. The data sequence is mapped (1004) to the plurality of physical antennas involved in the transmission. The data sequence is then transmitted (1006) using the plurality of physical antennas, from which a signal quality metric of the transmitter can be determined corresponding to a difference between a received signal associated with transmission of each respective data symbol of the data sequence and a respective ideal location of a predefined constellation point associated with the data symbol being transmitted, wherein an error vector magnitude involving an aggregate difference associated with the data sequence transmitted via the plurality of physical antennas is determined.

Description

TECHNICAL FIELD

[0001] The present disclosure is directed to the definition and testing of error vector magnitude for antenna ports and multi-layer transmissions involving multiple physical antennas. BACKGROUND

[0002] Currently, user equipment such as wireless communication devices use wireless signals to communicate with other communication devices in network environments that can include one or more cells that can support various communication connections with networks and other devices operating within the networks. Network environments often involve one or more sets of standards that each define various aspects of any communication connections made when using the corresponding standard in the network environment. Examples of standards being developed and / or existing standards include New Radio Access Technology (NR), Long Term Evolution (LTE), Universal Mobile Telecommunications Service (UMTS), Global System for Mobile Communications (GSM), and / or Enhanced Data GSM Environment (EDGE).

[0003] In environments where multiple devices each having their own transmitter that share the same or nearby channel space can be operating, the performance of any one of the transmitters of any one of the devices can emit electromagnetic energy beyond the designated channel and potentially negatively impact the ability of another device to communicate in the same or nearby channel. Correspondingly, devices can be tested before they are allowed to use in a network to help better ensure that they operate in a manner that meets certain predefined operational parameters, thereby helping to better manage the overall performance of the network and thereby better avoid the potential for negatively impacting other nearby devices.

[0004] At least one metric that can be used to quantify transmitter performance is referred to as error vector magnitude (EVM). Error vector magnitude is intended to quantify the degree to which a signal can deviate from its intended perfect performance. In many forms of communication, information is encoded into a signal being transmitted that corresponds to one of a plurality of predefined constellation points. Within the signal, various constellation points can be used to define the value of the information being conveyed for that portion of the signal. Error vector magnitude relates to the degree to which a received constellation point differs from an expected constellation point that was intended to be transmitted. At least some standards define acceptable limits for EVM within which a transmitter is required to operate and provide for testing of the acceptable limits.

[0005] Historically, EVM has only been defined for single antenna transmissions. However, increasingly, communication standards are being defined in which multiple physical antennas are being used to support certain transmissions such as via certain defined communication ports that can each be mapped to multiple physical antennas and in cases where multiple-input multiple-output (MIMO) transmission layers are being defined and used.

[0006] The present inventor has recognized that it would be beneficial to develop a definition of an error vector magnitude that can be used to quantify transmitter performance and that can be tested with respect to transmissions involving multiple physical antennas, where in at least some cases an aggregate difference associated with a data sequence involving transmission via multiple physical antennas can be determined. SUMMARY

[0007] The present application provides a method in a user equipment. The method comprises identifying a data sequence for transmission. The data sequence is mapped to a plurality of physical antennas to be involved in the transmission. The data sequence is then transmitted using the plurality of physical antennas, from which a signal quality metric of a transmitter can be determined, which corresponds to a difference between a received signal associated with transmission of each respective data symbol of the data sequence and a respective ideal position of a predefined constellation point associated with the data symbol being transmitted, wherein an error vector magnitude involving an aggregate difference associated with a data sequence involving transmission via the plurality of physical antennas is determined.

[0008] According to another possible embodiment, a user equipment comprising a plurality of physical antennas is provided. The user equipment comprises a controller identifying a data sequence for transmission, wherein the data sequence is mapped by the controller to the plurality of physical antennas to be involved in the transmission. The user equipment further comprises a transmitter transmitting the data sequence using the plurality of physical antennas, from which a signal quality metric of a transmitter can be determined, which corresponds to a difference between a received signal associated with transmission of each respective data symbol of the data sequence and a respective ideal position of a predefined constellation point associated with the data symbol being transmitted, wherein an error vector magnitude involving an aggregate difference associated with a data sequence involving transmission via the plurality of physical antennas is determined.

[0009] According to a further possible embodiment, a method in a network entity is provided. The method comprises receiving a data sequence transmitted from a user equipment at one or more physical antennas of the network entity, wherein the data sequence has been mapped to a plurality of physical antennas of the user equipment to be involved in the transmission. A signal quality metric of a transmitter of the user equipment is determined, which corresponds to a difference between a received signal associated with transmission of each respective data symbol and a respective ideal position of a predefined constellation point associated with the data symbol being transmitted, wherein an error vector magnitude involving an aggregate difference associated with a data sequence involved in transmission via the plurality of physical antennas is determined.

[0010] According to yet another further possible embodiment, a network entity for communicating with a user equipment is provided. The network entity comprises a receiver to receive a data sequence transmitted from a user equipment at one or more physical antennas of the network entity, wherein the data sequence has been mapped to a plurality of physical antennas of the user equipment involved in the transmission. The network entity further comprises a controller to determine a signal quality measure of a transmitter of the user equipment, which corresponds to a difference between a received signal associated with the transmission of each respective data symbol and a respective ideal position of a predefined constellation point associated with the data symbol transmitted, wherein an error vector magnitude is determined which involves an aggregated difference associated with the data sequence involved in the transmission via the plurality of physical antennas.

[0011] These and other features and advantages of the present application will become apparent from the following description of one or more preferred embodiments, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a block diagram of an exemplary network environment in which the present application is applicable to operate;

[0013] Figure 2 is a table of minimum requirements for meeting the requirements of error vector magnitude (EVM) as provided in existing 3GPP Technical Specification 36.101 defined for single antenna transmission for various modulation forms;

[0014] Figure 3 is a table of minimum requirements for meeting the requirements of error vector magnitude as provided in existing 3GPP Technical Specification 38.101-1 defined for single antenna transmission for various modulation forms;

[0015] Figure 4 is a table of minimum requirements for meeting the requirements of error vector magnitude as provided in existing 3GPP Technical Specification 38.101-2 defined for single antenna transmission for various modulation forms;

[0016] Figure 5 is a block diagram identifying error vector magnitude measurement points with respect to a device with a transmitter being tested for an exemplary test equipment transmitting on a single physical antenna;

[0017] Figure 6 is a block diagram of a user equipment implementation for antenna ports or single layer MIMO corresponding to two physical antennas;

[0018] Figure 7 is a block diagram of a test equipment for determining EVM for an implementation corresponding to antenna ports or single layer MIMO corresponding to two physical antennas;

[0019] Figure 8 is a block diagram of a user equipment implementation for two-layer MIMO corresponding to two physical antennas;

[0020] Figure 9 is a block diagram of a test equipment for determining EVM for an implementation corresponding to two-layer MIMO corresponding to two physical antennas;

[0021] Figure 10 is a flowchart in a user equipment for supporting determination of transmitter EVM of the user equipment for transmissions involving multiple physical antennas;

[0022] Figure 11 is a flowchart in a network entity, such as a test equipment for determining transmitter EVM of a user equipment corresponding to transmissions involving multiple physical antennas; and

[0023] Figure 12 is a block diagram of an exemplary apparatus according to possible embodiments. DETAILED DESCRIPTION

[0024] While the disclosure can take form in various embodiments, a specific embodiment is shown in the drawings and will be described further below, and it is understood that the disclosure should be considered as an example of the application and not as limiting the application to the specific embodiment shown.

[0025] Embodiments provide error vector magnitude definitions and testing for antenna ports and multi-layer transmissions.

[0026] Figure 1 is an example block diagram of a system 100 according to possible embodiments. The system 100 can include a wireless communication device 110, such as a user equipment (UE), a base station 120, such as an enhanced Node B (eNB) or a next generation Node B (gNB), and a network 130. The wireless communication device 110 can be a wireless terminal, a portable wireless communication device, a smart phone, a cellular telephone, a flip phone, a personal digital assistant, a personal computer, a selective call receiver, a tablet computer, a laptop computer, or any other device capable of sending and receiving communication signals over a wireless network.

[0027] The network 130 can include any type of network capable of sending and receiving wireless communication signals. For example, the network 130 can include a wireless communication network, a cellular telephone network, a time division multiple access (TDMA) based network, a code division multiple access (CDMA) based network, an orthogonal frequency division multiple access (OFDMA) based network, a long term evolution (LTE) network, a fifth generation (5G) network, a third generation partnership project (3GPP) based network, a satellite communication network, a high altitude platform network, the Internet, and / or other communication network.

[0028] A basic quality measure of signal transmission is the error vector magnitude (EVM). EVM is defined as the normalized root mean square of the difference between the ideal modulated signal and the output signal of the transmitter, expressed as a percentage. EVM is a fundamental limit on the signal-to-noise ratio for transmission. The channel error rate is a function of both the signal-to-noise ratio, for which the lower limit is determined by the EVM, and the modulation constellation. For a given signal-to-noise ratio, the channel error rate increases with the increase in the modulation constellation size. Therefore, to achieve a given lower limit on the channel error rate, the EVM must decrease with the increase in the constellation size, and this is reflected in the Third Generation Partnership Project (3GPP) Technical Specifications (TSs) including TS 36.101, TS 38.101-1, and TS 38.101-2. In each of these cases, the requirements provided by the specifications are provided in a corresponding table.

[0029] More specifically, Figure 2 A minimum requirements table 200 is illustrated for meeting the requirements of the error vector magnitude (EVM) defined in the existing 3GPP Technical Specification 36.101 for single antenna transmission for various modulation forms.

[0030] Figure 3 A minimum requirements table 300 is illustrated for meeting the requirements of the error vector magnitude defined in the existing 3GPP Technical Specification 38.101-1 for single antenna transmission for various modulation forms.

[0031] Figure 4 A minimum requirements table 400 is illustrated for meeting the requirements of the error vector magnitude defined in the existing 3GPP Technical Specification 38.101-2 for single antenna transmission for various modulation forms.

[0032] Currently, EVM is defined only for single antenna transmission. Correspondingly, the technical specifications outline a method of determining EVM in the case where only a single antenna is defined for transmission. The corresponding means can be found in Appendix F of each of TS 36.101, TS 38.101-1, and TS 38.101-2. It is interesting that the method outlined in the existing technical specifications addresses the fact that only a single antenna is defined in the case, because 3GPP defines transmissions from antenna ports, not from antennas, where an antenna port can consist of multiple physical antennas. Therefore, there is a gap in the technical specifications, i.e., there is no basic transmission signal quality measure for transmissions from multiple physical antennas. Figure 5 A block diagram 500 is illustrated identifying error vector magnitude measurement points for a device with a transmitter being tested relative to an exemplary test equipment for transmission on a single physical antenna. The block diagram 500 is Figure F.1-1 taken from Appendix F of TS 38.101-1.

[0033] Currently, there is a discussion in RAN4 whether EVM can be measured independently for two transmit antenna connectors (not ports) in a conducted test. RAN4 is a part of the working group engaged in standards that engage in the development of standards for the radio frequency aspects of performance including transmission and reception parameters, radio resource management (RRM), and minimum requirements for channel demodulation and channel state information (CSI) reporting. One company has suggested that each antenna connector should be tested independently with the transmit chain of the other antenna connector turned off. Another company has insisted that both transmit chains must be turned on when measuring EVM on one antenna connector. The first company has argued that there is no need to turn on the second transmit chain because any leakage from the second transmit chain to the first transmit chain is essentially similar to a combination of layers that occurs in a channel and, therefore, the leakage can be cancelled by a MIMO receiver. However, this argument is essentially qualitative and does not provide any evidence that the leakage will not introduce a noise floor or, equivalently, a performance ceiling. The second company has argued that the second transmitter must be turned on during the test because there can be a nonlinear mixing of the signals on the two transmit chains that produces interference that cannot be suppressed by a MIMO receiver even if the MIMO receiver can cancel the leakage from the second transmit chain to the first transmit chain.

[0034] Since there is no evidence that the nonlinear mixing between the two transmit chains will not introduce a noise floor that cannot be cancelled by a MIMO receiver, it appears that EVM should be tested with both transmit chains turned on. However, since the linear coupling between the two antennas can be significant, it is generally not possible to measure EVM independently for the two transmit chains because the linear coupling from the second transmit chain to the first transmit chain can cause the first transmit chain to fail (incorrectly) for EVM.

[0035] Therefore, it would be beneficial to have:

[0036] i) an EVM test that is performed with both transmit chains turned on,

[0037] ii) an EVM test that is defined generally for antenna ports, and

[0038] iii) an EVM test that is applicable to multi-layer transmissions.

[0039] The conventional approach is noted in Annex F of TS 36.101-1, TS 38.101-1, and TS 38.101-2. In Figures 2 to 4 the EVM requirement is noted as a function of the modulation type. For example, Figure 5 a test point for the method for evaluating EVM is shown.

[0040] Conventional approaches typically define EVM only for the transmit antennas, not for the antenna ports. Furthermore, conventional approaches typically do not define EVM for UEs with multiple active transmit chains.

[0041] Embodiment 1 :

[0042] As mentioned above, the first exemplary embodiment of the present application focuses more on items (i) and (ii).

[0043] With this approach, it is possible to transmit data using a single-layer precoder from any codebook. However, it can be necessary to exclude precoding vectors with 0 values, such as [0 1] and [1 0] (for two transmit antennas), although the EVM definition should be able to handle this case.

[0044] The method for measuring EVM is then to have the test equipment apply a zero-forcing MIMO receiver (as opposed to a MMSE receiver) to the demodulated signal (i.e. the output of the Fast Fourier Transform (FFT)). Since the transmitter can have a frequency dependence across the channels due to the filter, the zero-forcing MIMO receiver should be computed separately for each subcarrier. For Orthogonal Frequency Division Multiplexing (OFDM) modulation, the mean square error is then computed as the square of the absolute value of the difference between the output of the zero-forcing Multiple Input Multiple Output (MIMO) receiver at each subcarrier and the corresponding known modulation symbol for the given subcarrier, averaged over all subcarriers of all allocated Resource Blocks (RBs). The normalized mean square error is the mean square error divided by the mean square value of the modulation symbol for the subcarriers of all allocated RBs. The EVM is computed as the square root of the normalized mean square error multiplied by 100 in percent.

[0045] It should be noted that the Local Oscillator (LO) leakage should be removed from each transmit chain before the FFT used for demodulation.

[0046] As additional detail, the zero-forcing MIMO receiver (which is equivalent to a matched filter for a single layer) is given by the expression

[0047]

[0048] where, is the estimate of the modulation symbol x for the subcarrier, and y is the 2x1 vector output of the FFT demodulator for the first and second transmit chains for the subcarrier. The vector h is the 2x1 vector of channel estimates for the demodulators of the first and second receive chains for the given subcarrier (which of course is a function of the applied precoder).

[0049] For direct Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM), the method given above can need to be slightly modified. As above, a zero-forcing MIMO receiver is used to obtain a symbol estimate for each subcarrier. However, after applying the zero-forcing MIMO receiver, an inverse discrete Fourier transform (IDFT) is applied to the symbol estimates of the subcarriers of the allocated RBs in order to form an estimate of the modulated data symbols. Then, the EVM is calculated based on the normalized mean square error of the difference between the IDFT output and the known data symbols.

[0050] It can be noted that method 1 provides an EVM definition per port, not per antenna. It can also be noted that this method can be extended to an arbitrary number of transmit antennas by increasing the length of the channel vector h according to the number of antennas.

[0051] In case of missing precoder dependent coupling, the measured EVM should in principle be independent of the precoder used to measure the EVM. However, if this is not the case, it can be beneficial to consider the EVM measurement averaged over multiple precoders.

[0052] Embodiment 2:

[0053] The second exemplary embodiment is similar to the above method except that it addresses (iii) in addition to (i) and (ii), i.e. it addresses the EVM for multi-layer transmission.

[0054] The method is similar to the method of the first embodiment except that multi-layer precoders from any codebook can be used to transmit the data. For multi-layer transmission, the output of the zero-forcing MIMO receiver is given by

[0055]

[0056] where the vector is the estimate of the modulation vector of the modulated symbols x of the two layers of subcarriers, and y is the 2x1 vector output of the FFT demodulators of the first and second transmit chains of subcarriers. The vector H is the 2x2 vector of channel estimates of the demodulators of the first and second receiver chains of a given subcarrier (of course, it is a function of the applied precoder). Thus, H ij is the output of the FFT demodulator of the jth transmit chain.

[0057] It should be noted that the LO leakage should be removed from each transmit chain before using the FFT demodulation.

[0058] For cyclic prefix - orthogonal frequency division multiplexing (CP-OFDM) modulation, the EVM for each layer can be calculated in a similar way as for single layer transmission. The EVM requirement can then be applied separately for each layer, or it can be applied after averaging between layers.

[0059] For multi-layer transmission, DFT-s-OFDM modulation can not need to be considered, as it is typically not allowed.

[0060] Depending on the amount of (linear and other) coupling between the transmit chains, the EVM can be dependent on the precoder, and it can therefore be necessary to consider whether the EVM requirement should be evaluated for multiple multi-layer precoders, and whether the average or maximum EVM should be used when setting the requirement.

[0061] It can be noted that this approach for defining EVM can be applied for any number of antennas and any number of layers, typically less than or equal to the number of antennas.

[0062] Embodiment 3:

[0063] The third exemplary embodiment uses the conventional method for measuring EVM in combination with embodiment 1 or 2. In a first step, the conventional EVM evaluation method is used independently on each transmit chain, but both transmit chains are on. If both transmit chains pass this method, the device passes and stops the test, and the device passes EVM. If transmit chain 1 or transmit chain 2 fails the conventional EVM evaluation, embodiment 1 or embodiment 2 is used as appropriate. If the UE passes EVM for the second test, the device passes. If not, the device fails.

[0064] There is currently no agreed method to evaluate the EVM of a UE transmitter with multiple transmit chains operating simultaneously. In this disclosure, multiple methods are proposed to solve this problem.

[0065] Furthermore, there is currently no 3GPP definition of EVM for antenna ports that are typically linear combinations of multiple antennas.

[0066] This disclosure proposes methods for defining and measuring the EVM of antenna ports. Furthermore, this disclosure proposes methods for defining and measuring the EVM for multi-layer MIMO transmission.

[0067] Spectrum flatness requirement

[0068] It has already been proposed to use a linear zero-forcing MIMO receiver to define EVM for generic antenna ports as well as for single-layer and multi-layer MIMO transmissions. When defining EVM for physical antennas, it is possible to use an equalizer to compensate for gain variations across frequency before measuring the EVM. However, in general, the spectral flatness requirement applies to the frequency domain equalizer used before the EVM measurement. The reason for this requirement is that if the eNB / gNB receiver needs to apply a large gain at the channel edges to equalize the signal, this can lead to a significant noise enhancement. In essence, the spectral flatness requirement corresponds to a limitation on the gain roll-off at the edges of the duplex filter of the UE.

[0069] For the same reasons as in the case of EVM measurement for physical antennas, it can be desirable to enforce the spectral flatness criterion on the linear zero-forcing MIMO receiver. One way to do this is to first sum the squares of the amplitudes of the two coefficients for each subcarrier to combine the FFTs corresponding to the two receive antennas and apply the existing spectral flatness criterion to the resulting value. The square root of the sum of squares can further be used to evaluate the spectral flatness. For multi-layer MIMO, the spectral flatness criterion can be applied separately to each layer, or the flatness requirement can be applied to the average of the values for each subcarrier.

[0070] A further possibility is to enforce the spectral flatness constraint only when transmitting on antenna ports that map to a single physical antenna and to do this for each physical antenna. Checking only these cases can be sufficient to better ensure that the duplexers of each transmit antenna do not roll off too much at the edges.

[0071] Applicability for more antennas

[0072] For all of the above examples, the UE has typically used only two physical antennas. Thus, in these examples, the antenna ports typically map to only two physical antennas. However, in general, an antenna port can map to any number of physical antennas. Thus, the EVM definition for a port and the EVM definition for a MIMO layer can be extended to include the mapping of any number of physical antennas.

[0073] Historically, the current definition of EVM has only applied to physical antennas, as discussed in at least some previous proposals, where a physical antenna corresponds to an antenna connector for the purposes of frequency range 1 (FR1). Thus, there currently does not exist an EVM definition for transmissions on an antenna port that is not limited to a single physical antenna, and similarly, there does not exist an EVM definition for transmissions on a MIMO layer that is not limited to a single physical antenna. Thus, there is a gap in the existing technical specifications, as there does not exist a basic transmission signal quality metric for a transmission from an antenna port or for a MIMO layer that maps to multiple physical antennas. In this document, we consider how such EVM requirements can be defined.

[0074] EVM definition for antenna ports or single MIMO layer

[0075] As mentioned above, Figure 5 Figure F.1-1 from Appendix F of TS 38.101-1 shows the UE transmitter and EVM measurement points transmitted over a single physical antenna. In contrast, Figure 6 A block diagram 600 illustrates a UE implementation for an antenna port or MIMO layer corresponding to two physical antennas. This implementation allows the same complex-valued antenna weights to be applied to all subcarriers, or alternatively, different complex-valued antenna weights to be applied to each subcarrier or each RB. Antenna weighting can also be performed after the IFFT, but in this case, the same complex weights are applied to all subcarriers.

[0076] Methods for evaluating EVM at antenna ports or MIMO layers, such as Figure 7 As shown, Figure 7 This corresponds to the minimum EVM that can be observed by a gNB receiver with two receiving antennas. More specifically, Figure 7 A block diagram 700 illustrates a test setup for determining the EVM for implementations corresponding to antenna ports with two physical antennas or a single-layer MIMO. Note that this EVM definition is not applicable to gNBs with a single receive antenna. The output of the FFT is provided to both the channel estimator and the linear zero-forcing MIMO receiver. For each subcarrier output of each FFT, the channel estimator correlates with the corresponding data symbols of the CP-OFDM and the corresponding output of the DFT of the DFT-s-OFDM to form a channel estimate.

[0077]

[0078] With this channel estimation, a linear unbiased estimate of the modulation symbol x is obtained. Given by the following formula

[0079]

[0080] Where y = [y1y2] are the outputs of the first and second FFTs for a given subcarrier. For CP-OFDM, the error for a given symbol is then calculated as... Furthermore, the square root of the sum of the squares of these errors at different frequencies is normalized and used to calculate the EVM of a layer or port. For DFT-s-OFDM, the error is measured as... in,

[0081] exist Figure 7In this method, the channel estimator uses known data to estimate the channel. Therefore, the test equipment does not need to know the weighting vector *w* used by the UE to implement port or layer mapping. The only requirement is that the port is implemented in a way that makes the weighting vector *w* constant during measurement. Thus, the test equipment does not need to know the weighting vector *w* used by the UE to implement port or layer mapping in order to measure the EVM of the port. Therefore, even if the test equipment does not know how the UE implements transparent transmit diversity, the EVM can be measured for transmission modes such as transparent transmit diversity (if *w* is constant during measurement). This leads to some recommendations supported by this document that can be implemented in current communication standards.

[0082] Recommendation 1: For transmissions on a single antenna port or a single MIMO layer, the EVM definition should assume the use of a linear zero-forcing MIMO receiver to estimate the modulation symbols.

[0083] Recommendation 2: For transparent transmit diversity, the EVM definition should assume the use of a linear zero-forcing MIMO receiver to estimate the modulation symbols.

[0084] EVM definition for multi-layer MIMO

[0085] Figure 8 A block diagram 800 illustrates a UE implementation of a two-layer MIMO transmission.

[0086] Methods for evaluating the EVM of two-layer MIMO transmission, such as Figure 8 As shown. The output of the FFT is provided to both the channel estimator and the linear zero-forcing MIMO receiver. For each subcarrier output of each FFT, the channel estimator correlates it with the corresponding data symbols to form a channel estimate.

[0087]

[0088] The first column corresponds to the channel estimation of the first layer, and the second column corresponds to the channel estimation of the second layer.

[0089] Using this channel estimation, the vector of the first and second layer vector data symbols x The linear unbiased estimate is given as

[0090]

[0091] Among them, y T =[y1y2] represents the outputs of the first and second FFTs for a given subcarrier. The error of the symbols on the first and second layers is calculated as follows: and Furthermore, the square root of the sum of the squares of these errors at the frequency was normalized and used to calculate the EVM of the first and second layers.

[0092] Figure 9 Figure illustrates a block diagram 900 of a test equipment for determining EVM for an implementation corresponding to two-layer MIMO corresponding to two physical antennas. As can be seen in Figure 9 As can be seen in, EVM measurements can typically be layer dependent. Thus, there is a question about whether the requirement should be based on the average of EVM measurements or on the maximum of EVM measurements. Furthermore, depending on the size of the codebook used, there is a question about whether EVM should be measured for all precoders in the codebook or only for a subset, and whether these EVM measurements should be averaged or whether the maximum of EVM measurements should be used. This leads to some proposals that can be supported by the present document, which can be implemented in current communication standards.

[0093] Proposal 3: For multi-layer MIMO transmission, the EVM definition should assume that linear zero-forcing MIMO receiver is used to estimate the modulation symbols of each layer.

[0094] Proposal 4: When setting the EVM requirement for multi-layer MIMO transmission, the EVM measurements should be averaged over the MIMO layers and the precoder set for which the EVM is measured.

[0095] Further and / or alternatively, for the EVM requirement can be set to include a per-layer EVM requirement that would need to be satisfied individually for each of the multiple layers.

[0096] In summary, historically, the current definition of EVM as discussed in at least some previous proposals and existing technical standards typically only applies to a physical antenna, where for FR1, a physical antenna corresponds to an antenna connector. Thus, there is currently no EVM definition for transmissions on an antenna port that is not limited to a single physical antenna, and similarly, no EVM definition for transmissions on a MIMO layer that is not limited to a single physical antenna. Thus, there is a gap in the technical specifications, i.e., there is no basic transmission signal quality metric for transmissions from an antenna port or for MIMO layers that are mapped to multiple physical antennas.

[0097] Thus, in the present document, we propose a method for defining and measuring EVM for transmissions from an antenna port or for MIMO layers that are mapped to multiple physical antennas, and for multi-layer MIMO transmissions.

[0098] Figure 10A flowchart 1000 illustrating a method in a user equipment for supporting determining a transmitter EVM of the user equipment for a transmission involving a plurality of physical antennas is shown. The method includes identifying a data sequence for the transmission (1002). The data sequence is mapped to a plurality of physical antennas involved in the transmission (1004). The data sequence is then transmitted using the plurality of physical antennas, from which a signal quality metric of the transmitter can be determined, which corresponds to a difference between a received signal associated with transmission of each respective data symbol of the data sequence and a respective ideal location of a predefined constellation point associated with the data symbol being transmitted, wherein an error vector magnitude involving an aggregate difference associated with the data sequence involving transmission via the plurality of physical antennas is determined (1006).

[0099] In some instances, the mapping of the data sequence to the plurality of physical antennas can be associated with one or more antenna ports, wherein each of the antenna ports is associated with one or more of the plurality of physical antennas. In some of these instances, each of the antenna ports can be defined as a respective linear combination of one or more of the plurality of physical antennas. Further, the error vector magnitude can be associated with an output of a zero-forcing multiple-input multiple-output (MIMO) receiver respectively applied to the plurality of physical antennas.

[0100] In some instances, a fast Fourier transform can be computed for an output of a receiver associated with a corresponding one of the plurality of physical antennas. Based on a channel estimate for each carrier of each of the plurality of physical antennas, a separate zero-forcing MIMO receiver can be computed for each subcarrier of each allocated resource block. The separate zero-forcing MIMO receiver computed for each subcarrier can be applied to an output of the fast Fourier transform. The error vector magnitude can be measured by comparing data symbols of the data sequence to the corresponding output of the zero-forcing MIMO receiver.

[0101] In some instances, the mapping of the data sequence to the plurality of physical antennas can be associated with a plurality of transmission layers, wherein each of the plurality of transmission layers is associated with one or more of the plurality of physical antennas. In some of these instances, the error vector magnitude can be associated with an output of a zero-forcing multiple-input multiple-output (MIMO) receiver respectively applied to the plurality of physical antennas.

[0102] In some instances, a fast Fourier transform can be computed for an output of a receiver associated with a corresponding one of the plurality of physical antennas. Based on the channel estimate for each carrier of each of the plurality of physical antennas, a separate zero-forcing MIMO receiver can be computed for each subcarrier of each allocated resource block. The separate zero-forcing MIMO receiver computed for each subcarrier can be applied to the output of the fast Fourier transform. Each output of the zero-forcing MIMO receiver can correspond to a different one of the plurality of transmission layers. An error vector magnitude can be measured for each of the plurality of transmission layers by comparing data symbols of the data sequence to the corresponding output of the zero-forcing MIMO receiver.

[0103] In some instances, the signal quality metric of the transmitter can be an average of the error vector magnitudes measured for each of the plurality of transmission layers. In some of these or other instances, a figure of merit of the transmitter can be determined, the figure of merit corresponding to a determined largest one of the error vector magnitudes measured for each of the plurality of transmission layers.

[0104] Figure 11 A flowchart 1100 illustrating a method in a network entity, such as a test device for determining a transmitter EVM of a user equipment corresponding to transmissions involving a plurality of physical antennas, is shown. The method includes receiving a data sequence transmitted from a user equipment at one or more physical antennas of the network entity, where the data sequence has been mapped to a plurality of physical antennas of the user equipment involved in the transmission (1102). A signal quality metric of a transmitter of the user equipment is determined, the signal quality metric corresponding to a difference between a received signal associated with transmission of each respective data symbol and a respective ideal location of a predefined constellation point associated with the data symbol transmitted, where an error vector magnitude is determined involving an aggregate difference associated with the data sequence involved in the transmission via the plurality of physical antennas (1104).

[0105] It should be understood that although a certain sequence of steps is shown in the figures, various additional or different steps can be performed depending on the embodiment, and one or more of the particular steps can be rearranged, repeated, or eliminated depending on the embodiment. Further, some of the steps performed can be repeated on a ongoing or continuous basis while other steps are performed. Further, different steps can be performed by different elements or in a single element of the disclosed embodiments.

[0106] Figure 12This is a block diagram 1200 of an exemplary device such as wireless communication device 110 according to a possible embodiment. Device 1200 may include a housing 1210, a controller 1220 within the housing 1210, audio input and output circuitry 1230 coupled to the controller 1220, a display 1240 coupled to the controller 1220, a transceiver 1250 coupled to the controller 1220, an antenna 1255 coupled to the transceiver 1250, a user interface 1260 coupled to the controller 1220, a memory 1270 coupled to the controller 1220, and a network interface 1280 coupled to the controller 1220. Device 1200 is capable of performing the methods described in all embodiments.

[0107] Display 1240 can be a viewfinder, liquid crystal display (LCD), light-emitting diode (LED) display, plasma display, projection display, touchscreen, or any other device that displays information. Transceiver 1250 can include a transmitter and / or receiver. Audio input and output circuitry 1230 can include a microphone, speaker, transducer, or any other audio input and output circuitry. User interface 1260 can include a keypad, keyboard, buttons, touchpad, joystick, touchscreen display, another additional display, or any other device that can be used to provide an interface between the user and the electronic device. Network interface 1280 can be a Universal Serial Bus (USB) port, Ethernet port, infrared transmitter / receiver, IEEE 1394 port, WLAN transceiver, or any other interface that can connect the device to a network, device, or computer and can send and receive data communication signals. Memory 1270 can include random access memory, read-only memory, optical memory, solid-state memory, flash memory, removable memory, hard disk drive, cache, or any other memory that can be coupled to the device.

[0108] Device 1200 or controller 1220 can implement any operating system, such as Microsoft. Android TM Or any other operating system. The device operating software can be written in any programming language such as C, C++, Java, or Visual Basic. The device software can also run on application frameworks, such as, for example, frame, The software and / or the operating system can be stored in the memory 1270 or elsewhere on the apparatus 1200. The apparatus 1200 or controller 1220 can also use hardware to implement the disclosed operations. For example, the controller 1220 can be any programmable processor. The disclosed embodiments can also be implemented on a general-purpose or a special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an integrated circuit, a hardware / electronic logic circuit such as a discrete element circuit, a programmable logic device, or the like. In general, the controller 1220 can be any controller or processor device or devices capable of operating an apparatus and implementing the disclosed embodiments. Some or all of the additional elements of the apparatus 1200 can also be capable of performing some or all of the operations of the disclosed embodiments.

[0109] The methods of the present disclosure can be implemented on a programmed processor. However, the controller, flow charts, and modules can also be implemented on a general purpose or a special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an integrated circuit, a hardware / electronic logic circuit such as a discrete element circuit, a programmable logic device, or the like. In general, any device on which resides a finite state machine capable of implementing the flow charts shown in the figures can be used to implement the processor function of the present disclosure.

[0110] While this disclosure has been described with respect to its specific implementations, it is apparent that many alternates, modifications and variations will be suggested to those skilled in the art in light of this disclosure. For example, in other embodiments, various components of the embodiments can be interchanged, added, or removed. Also, not all elements of each figure are necessary for operation of the disclosed embodiments. For example, one of ordinary skill in the art having the benefit of the teachings of this disclosure will be able to make and use the present disclosure without those elements. Accordingly, the embodiments of the present disclosure as described herein are intended to be illustrative and not limiting. Various changes can be made without departing from the spirit and scope of the present disclosure.

[0111] In this document, relational terms such as“first,”“second,” and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The phrase“and / or” where following two or more recited elements, such as“a, b, and / or c,” is intended to mean one, some, or all of the elements in the group of a, b, and c. The terms“comprises,”“comprising,”“includes,”“including,” and the like are defined to be open and non-limiting terms. The use of the terms“comprises,”“comprising,”“includes,”“including,” and the like in this document does not limit the number or possible constituents of any processes, methods, articles, or apparatuses described herein to those listed in the respective clause. The use of the term“comprises” does not exclude the presence of additional elements or steps. The use of the term“comprises” does not exclude the presence of additional elements or steps. Where an indefinite or definite article is used, such as“a” or“an,” it is intended to refer to one or more than one (i.e., to“at least one”). The use of the terms“one,”“a,” or“an” does not exclude the presence of additional elements or steps. The use of the terms“another” and“a further” are defined as at least a second or more. The terms“comprise,”“comprising,”“comprises,” and the like can be used synonymously with“include,”“including,”“includes,”“contain,”“containing,” or“contains.” The term“include” and variations thereof, are used synonymously with“comprise” and variations thereof.

Claims

1. A method in a user equipment, comprising: Identify the data sequence used for transmission; The data sequence is mapped to multiple physical antennas to be involved in the transmission; as well as The data sequence is transmitted using the plurality of physical antennas, from which a transmitter signal quality metric can be determined. This transmitter signal quality metric corresponds to the difference between the received signal associated with the transmission of each corresponding data symbol of the data sequence and the corresponding ideal position of a predefined constellation point associated with the transmitted data symbol, wherein an error vector magnitude relating to the aggregated difference associated with the data sequence transmitted via the plurality of physical antennas is determined. The mapping of the data sequence to the plurality of physical antennas is associated with a plurality of transmission layers, wherein each of the plurality of transmission layers is associated with one or more of the plurality of physical antennas. The magnitude of the error vector is associated with the outputs of the zero-forcing multiple-input multiple-output (MIMO) receivers applied to the plurality of physical antennas. Specifically, the error vector magnitude is measured for each of the plurality of transport layers by comparing the data symbols of the data sequence with the corresponding output of the zero-forcing MIMO receiver. The quality factor of the transmitter is determined, and the quality factor corresponds to the largest of the determined error vector magnitudes measured for each of the plurality of transmission layers.

2. The method according to claim 1, wherein, The mapping of the data sequence to the plurality of physical antennas is associated with one or more antenna ports, wherein each of the antenna ports is associated with one or more of the plurality of physical antennas.

3. The method according to claim 2, wherein, Each of the antenna ports is defined as a corresponding linear combination of one or more of the plurality of physical antennas.

4. The method according to claim 2, wherein, The magnitude of the error vector is associated with the output of the zero-forcing multiple-input multiple-output (MIMO) receivers that are respectively applied to the plurality of physical antennas.

5. The method according to claim 4, wherein, Calculate the Fast Fourier Transform for the output of the receiver associated with a corresponding one of the plurality of physical antennas.

6. The method according to claim 5, wherein, Based on the channel estimation for each carrier of each of the plurality of physical antennas, a separate zero-forcing MIMO receiver is calculated for each subcarrier of each allocated resource block.

7. The method according to claim 6, wherein, The individual zero-forcing MIMO receiver, calculated for each subcarrier, is applied to the output of the Fast Fourier Transform.

8. The method according to claim 7, wherein, The magnitude of the error vector is measured by comparing the data symbols of the data sequence with the corresponding output of the zero-forcing MIMO receiver.

9. The method according to claim 1, wherein, A Fast Fourier Transform is calculated for the output of the receiver associated with a corresponding one of the plurality of physical antennas.

10. The method according to claim 9, wherein, Based on the channel estimation for each carrier of each of the plurality of physical antennas, a separate zero-forcing MIMO receiver is calculated for each subcarrier of each allocated resource block.

11. The method according to claim 10, wherein, The individual zero-forcing MIMO receiver, calculated for each subcarrier, is applied to the output of the Fast Fourier Transform.

12. The method according to claim 11, wherein, Each output of the zero-forcing MIMO receiver corresponds to a different one of the plurality of transport layers.

13. The method according to claim 1, wherein, The signal quality metric of the transmitter is the average of the error vector magnitudes measured for each of the plurality of transmission layers.

14. A user equipment comprising a plurality of physical antennas, the user equipment comprising: A controller that identifies a data sequence for transmission, wherein the data sequence is mapped by the controller to the plurality of physical antennas involved in the transmission; and A transmitter, which uses the plurality of physical antennas to transmit the data sequence, from which a signal quality metric of the transmitter can be determined. This signal quality metric corresponds to the difference between the received signal associated with the transmission of each corresponding data symbol of the data sequence and the corresponding ideal position of a predefined constellation point associated with the transmitted data symbol, wherein an error vector magnitude relating to the aggregated difference associated with the data sequence transmitted via the plurality of physical antennas is determined. The mapping of the data sequence to the plurality of physical antennas is associated with a plurality of transmission layers, wherein each of the plurality of transmission layers is associated with one or more of the plurality of physical antennas. The magnitude of the error vector is associated with the outputs of the zero-forcing multiple-input multiple-output (MIMO) receivers applied to the plurality of physical antennas. Specifically, the error vector magnitude is measured for each of the plurality of transport layers by comparing the data symbols of the data sequence with the corresponding output of the zero-forcing MIMO receiver. The quality factor of the transmitter is determined, and the quality factor corresponds to the largest of the determined error vector magnitudes measured for each of the plurality of transmission layers.

15. The user equipment according to claim 14, wherein, The controller associates the mapping of the data sequence to the plurality of physical antennas with one or more antenna ports, wherein each of the antenna ports is associated with one or more of the plurality of physical antennas.

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