WO2023014272A1

WO2023014272A1 - Wireless device coherence transmission testing

Info

Publication number: WO2023014272A1
Application number: PCT/SE2022/050739
Authority: WO
Inventors: Chunhui Zhang; Johan AXNÄS; Robert Mark Harrison; Zhipeng LIN; Anqi HE
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2021-08-06
Filing date: 2022-08-05
Publication date: 2023-02-09

Abstract

A method, system and apparatus are disclosed. A testing device is provided. The testing device includes processing circuitry configured to: receive, from a wireless device, at least one transmission over a plurality of slots, perform at least one measurement after a Fast Fourier Transform, FFT, stage of the testing device of the at least one transmission, compensate for carrier frequency offset, CFO, phase drift in the at least one transmission based on the at least one measurement, determine a magnitude of phase distortion variation of the at least one transmission after the compensation of CFO phase drift, and report the magnitude of phase distortion variation.

Description

WIRELESS DEVICE COHERENCE TRANSMISSION TESTING

TECHNICAL FIELD

The present disclosure relates to wireless communications, and in particular, to RF transmitter coherence measurement and/or determination based at least on compensating for carrier frequency offset (CFO) in a radio frequency (RF) transmitter.

BACKGROUND

The Third Generation Partnership Project (3GPP) has developed and is developing standards for Fourth Generation (4G) (also referred to as Long Term Evolution (LTE)) and Fifth Generation (5G) (also referred to as New Radio (NR)) wireless communication systems. Such systems provide, among other features, broadband communication between network nodes, such as base stations, and mobile wireless devices (WD), as well as communication between network nodes and between WDs.

Physical uplink shared channel (PUSCH) repetition and TBoMS (e.g., TB processing over multi-slot)

Slot aggregation for PUSCH is supported in 3GPP Release 15 (Rel-15) and was renamed to PUSCH Repetition Type A in 3GPP Release 16 (Rel-16). The name PUSCH repetition Type A is used even if there is only a single repetition, i.e., no slot aggregation. In 3GPP Rel-15, a PUSCH transmission that would overlap with DL symbols is not transmitted.

For downlink control information (DCI) granted multi-slot transmission (physical downlink shared channel (PDSCH)/PUSCH) vs. semi-static downlink (DL)/uplink (UL) assignment.

If semi-static DL/UL assignment configuration of a slot has no direct conflict with scheduled PDSCH/PUSCH assigned symbols, the PDSCH/PUSCH in that slot is received/transmitted.

If semi-static DL/UL assignment configuration of a slot has direction conflict with scheduled PDSCH/PUSCH assigned symbols, the PDSCH/PUSCH transmission in that slot is not received/transmitted, i.e., the effective number of repetitions reduces. In 3GPP Rel-15, the number of repetitions is semi-statically configured by radio resource control (RRC) parameter pusch-AggregationFactor. At most 8 repetitions are supported in Rel-15. pusch-AggregationFactor ENUMERATED { n2, n4, n8 }

A new repetition format of PUSCH repetition Type B is supported in 3GPP Rel-16, which allows back-to-back repetition of PUSCH transmissions. One difference of Type B from Type A is that repetition Type A only allows a single repetition in each slot, with each repetition occupying the same symbols. Using this format with a PUSCH length shorter than 14 introduces gaps between repetitions, increasing the overall latency. The other change compared to 3GPP Rel-15 is how the number of repetitions is signaled. In 3GPP Rel-15, the number of repetitions is semi- statically configured, while in Rel. 16 the number of repetitions can be indicated dynamically in DCI. This applies both to dynamic grants and configured grants type 2.

PUSCH repetition and TBoMS

Slot aggregation for PUSCH is supported in 3GPP Rel-15 and was renamed to PUSCH Repetition Type A in 3GPP Rel-16. The name PUSCH repetition Type A is used even if there is only a single repetition, i.e., no slot aggregation. In 3GPP Rel-15, a PUSCH transmission that would overlap with DL symbols is not transmitted.

For DCI granted multi-slot transmission (PDSCH/PUSCH) vs. semi-static DL/UL assignment

If semi-static DL/UL assignment configuration of a slot has no direction conflict with scheduled PDSCH/PUSCH assigned symbols, the PDSCH/PUSCH in that slot is received/transmitted.

If semi-static DL/UL assignment configuration of a slot has direction conflict with scheduled PDSCH/PUSCH assigned symbols, the PDSCH/PUSCH transmission in that slot is not received/transmitted, i.e. the effective number of repetitions reduces.

In 3GPP Rel-15, the number of repetitions is semi-statically configured by RRC parameter pusch-AggregationFactor. At most 8 repetitions are supported. pusch-AggregationFactor ENUMERATED { n2, n4, n8 }

A new repetition format PUSCH repetition Type B is supported in 3GPP Rel- 16, which allows back-to-back repetition of PUSCH transmissions. The biggest difference of Type B from Type A is that repetition Type A only allows a single repetition in each slot, with each repetition occupying the same symbols. Using this format with a PUSCH length shorter than 14 introduces gaps between repetitions, increasing the overall latency. The other change compared to 3GPP Rel-15 is how the number of repetitions is signaled. In 3GPP Rel-15, the number of repetitions is semi- statically configured, while in 3 GPP Rel. 16 the number of repetitions can be indicated dynamically in DCI. This applies both to dynamic grants and configured grants type 2.

In NR Rel-15/16, one UL transport block (TB) is confined to the UL symbols in a slot. To support high data rate, multiple physical resource blocks (PRBs) in a slot can be used for the transmission of a large TB and the multiple PRBs share wireless device transmission power. Transport block (TB) processing over multiple slots (TBoMS) was proposed as a candidate solution of coverage enhancement of PUSCH in NR 3GPP Rel-17. Multi-slot TB extends the time domain resource for the transmission of a TB across a slot border to increase a total power for transmission of a TB compared to TB transmission in a single slot. Multi-slot TB also reduces cyclic redundancy check (CRC) overhead by reducing the number of CRCs in a given number of slots compared to the PUSCH transmissions at the same data rate with separate TBs.

Phase-related UE capabilities

In NR 3 GPP Rel- 16, requirements of phase and power error difference between antenna ports are defined with the following and also in 3GPP Technical Specification (TS) 38.101-1 v 16.3.0:

- Requirements for coherent UL Multiple Input Multiple Output (MIMO) o For coherent UL MIMO, Table 6.4D.4-1 in 3GPP TS 38.101-1 V16.3.0: lists the maximum allowable difference between the measured relative power and phase errors between different antenna ports in any slot within the specified time window from the last transmitted SRS on the same antenna ports, for the purpose of uplink transmission (codebook or non-codebook usage) and those measured at that last SRS. The requirements in Table 6.4D.4-1 apply when the UL transmission power at each antenna port is larger than 0 dBm for SRS transmission and for the duration of time window.

Table 6.4D.4-1 in 3GPP TS 38.101-1 vl6.3.0: Maximum allowable difference of relative phase and power errors in a given slot compared to those measured at last SRS transmitted

Joint channel estimation for NR coverage enhancement

For the NR coverage enhancements work item (WI) for 3 GPP Rel-17, it has been discussed to investigate standardization of PUSCH cross-slot channel estimation, often referred to as joint channel estimation for PUSCH. In an NR network node (e.g., gNB), the reception of a PUSCH on a high level typically consists of two steps: (i) estimation of the physical channel based on measurements of reference symbols (e.g., DMRS) and (ii) equalize, demodulate, and decode the signal based on the estimated channel.

In existing releases of NR 3GPP (Rel-15/16), the network node performs the channel estimation (or at least the channel filtering part of it) on each slot individually, since different slots may have different random phase offsets, timing differences, and/or other differences that may make cross-slot channel filtering impossible.

3GPP Rel-17 enhancements In the NR coverage enhancements work item (WI) for 3 GPP Rel-17, it has been discussed to support PUSCH cross-slot channel estimation, or joint channel estimation as it is referred to in 3GPP where the two terms may be treated as synonyms herein. The idea is to impose some constraints on the wireless device regarding phase changes, etc., between slots in order to allow the network node to estimate the channel jointly for multiple slots. Such joint processing over multiple slots can improve the channel estimation quality, and thereby improve overall link and system performance. The NR coverage enhancements work item description (WID, 3 GPP RP- 202928) states:

Specification of PUSCH enhancements [RANI, RAN4] o Specify mechanism(s) to enable joint channel estimation [Radio Access Network 1 (RANI), RAN4]

■ Mechanism(s) to enable joint channel estimation over multiple PUSCH transmissions, based on the conditions to keep power consistency and phase continuity to be investigated and specified if necessary by RAN4 [RANI, RAN4]

• Potential optimization of demodulation reference signal (DMRS) location/granularity in time domain is not precluded

■ Inter-slot frequency hopping with inter-slot bundling to enable joint channel estimation [RANI]

Pre FFT minimization process

Pre FFT minimization process is specified in Annex E.3.1 of 3GPP TS 38.521-2 V16.8.0:

Before applying the pre-FFT minimization process, z(v) and i(v) are portioned into n pieces, comprising one slot each, where n is as defined in Annex E.2.2....

Each slot is processed separately. Sample timing, Carrier frequency and carrier leakage in z(v) are jointly varied in order to minimize the difference between z(v) and i(v). Best fit (minimum difference) is achieved when the RMS difference value between z(v) and i(v) is an absolute minimum.

The carrier frequency variation and the IQ variation are the measurement results: Carrier Frequency Error and Carrier leakage.

From the acquired samples 10 carrier frequencies can be derived by averaging frequency errors for every 4 or 8 slots for 60 and 120 kHz SCS.

From the acquired samples n carrier frequencies and n carrier leakages can be derived.

NOTE 1 : The minimization process, to derive carrier leakage and RF error can be supported by Post FFT operations. However, the minimization process defined in the pre FFT domain includes all acquired samples (i.e., it does not exclude the samples in between the FFT widths and it does not exclude the bandwidth outside the transmission bandwidth configuration

NOTE 2: The algorithm would allow deriving Carrier Frequency error and Sample Frequency error of the TX under test separately. However, there are no requirements for Sample Frequency error. Hence the algorithm models the RF and the sample frequency commonly (not independently). It returns one error and does not distinguish between both.

After this process the samples z(v) are called z°(v).

In the 3GPP Rel-17 NR coverage enhancement work item, one technique to improve the coverage is time domain-based solution which increases the number of actual repetitions for PUSCH transmission. One further enhancement on the repetition technique is the DM-RS bundling or joint channel estimation (JCE) for both PUSCH and PUCCH. The condition that JCE has positive gain over the non DM-RS bunding is that the phase and amplitude variation in the frequency response of wireless device RF chain is kept sufficiently small or below to predefined threshold and thus wireless device can transmit the repetition signal coherently and the DM-RS symbol in different repetition slot could be combined and channel estimation accuracy can be improved at the low SNR condition.

The limit for phase and amplitude variation in the frequency response of wireless device RF chain for different repetition time slot may be specified for wireless device RF requirement and a method to test may be needed, but existing NR test specifications do not provide any such method to test the ability of a wireless device to maintain constant phase across slots. One problem in developing such tests of inter-slot coherence is that carrier frequency offset (CFO) may be present, which may cause additional phase rotation.

SUMMARY

Some embodiments advantageously provide methods, systems, and apparatuses for RF transmitter coherence measurement and/or determination based at least on compensating for carrier frequency offset (CFO) in a radio frequency (RF) transmitter. A test method to measure the transmitter (TX) coherence in terms of the phase and amplitude variation in the frequency response of the wireless device RF transmitter is described herein. The equations used to derive the magnitude of phase/amplitude distortion variation by the wireless device transmitter in cross time slots is listed with the CFO compensation before and after the FFT processing. In one or more alternative embodiments, the EVM procedure is used to test the TX coherence, in that case, equalization coefficients derived in the first time slot is used to equalize the other repetition slot data and thus the error vector measure reflects the added amplitude and phase variation due to the RF hardware impairments.

According to one aspect of the present disclosure, a testing device is provided. The testing device includes processing circuitry configured to: receive, from a wireless device, at least one transmission over a plurality of slots, perform at least one measurement after a Fast Fourier Transform, FFT, stage of the testing device of the at least one transmission, compensate for carrier frequency offset, CFO, phase drift in the at least one transmission based on the at least one measurement, determine a magnitude of phase distortion variation of the at least one transmission after the compensation of CFO phase drift, and report the magnitude of phase distortion variation.

According to one or more embodiments of the present disclosure, the at least one measurement includes data captured after the FFT stage. According to one or more embodiments of the present disclosure, the at least one measurement is configured to measure a change of channel impulse response in different time slots of the plurality of time slots. According to one or more embodiments of the present disclosure, the processing circuitry is further configured to estimate a CFO within each slot of the plurality of slots, and determine a combined CFO by averaging the CFOs for the plurality of slots, the compensating for CFO phase drift uses the combined CFO.

According to one or more embodiments of the present disclosure, the processing circuitry is further configured to: concatenate a plurality of time slots, and determine a combined CFO based on the concatenated time slots over the plurality of slots, the compensating for CFO phase drift uses the combined CFO. According to one or more embodiments of the present disclosure, the compensating for CFO phase drift is performed on measurement data from a beginning symbol in a beginning time slot of the plurality of time slots to a last symbol in a last time slots over the plurality of slots. According to one or more embodiments of the present disclosure, the compensating for CFO phase drift is performed before an FFT stage.

According to one or more embodiments of the present disclosure, compensating the CFO phase drift is performed, after the FFT stage, on measurement data by deducting the CFO phase drift. According to one or more embodiments of the present disclosure, the processing circuitry is further configured to determine a phase distortion variation using the following equation:

AO = arg

tl), 2K), where A0 is a phase distortion variation, A is an estimated carrier frequency offset, and mod (27tAf(t2-tl), 2K) is the CFO phase drift, and the magnitude of the phase distortion variation being based on the phase distortion variation.

According to one or more embodiments of the present disclosure, the determining of the magnitude of phase distortion variation includes: determining a channel impulse response for a first time slot and a second time slot where the first time slot and second time slot is one of consecutive and non-consecutive time slots, and determining a phase distortion variation of the channel impulse response of a wireless device between the first time slot and second time slot using the following equation:

AO = arg

Where A0 is a phase distortion variation, tl is the first time slot, and t2 is the second time slot, and the magnitude of the phase distortion variation is based on the phase distortion variation.

According to one or more embodiments of the present disclosure, the compensating for CFO phase drift includes: acquiring a set of samples of a signal associated with the at least one transmission over the plurality of slots, and varying at least one of a sample timing, carrier frequency and carrier leakage of the set of samples to produce an adjusted signal having a minimal difference from a reference signal. According to one or more embodiments of the present disclosure, the compensating for CFO phase drift includes determining discrete Fourier transforms, DFTs, of each of a first portion and second portion of the adjusted signal where the first portion is in a different slot than the second portion, and the magnitude of phase distortion variation is based on the determined DFTs of each of the first portion and second portion of the adjusted signal. According to one or more embodiments of the present disclosure, the determining of the magnitude of phase distortion variation of the at least one transmission after the compensation of CFO phase drift is based on the testing device assuming that hardware of the wireless device keeps CFO phase drift constant where the hardware of the wireless device includes the RF transmitter of the wireless device. According to one or more embodiments of the present disclosure, the determining of RF transmitter coherence of the wireless device is performed with respect to an amplitude variation of the frequency response of the RF transmitter over the plurality of slots.

According to another aspect of the present disclosure, a method implemented by a testing device is provided. At least one transmission is received from a wireless device over a plurality of slots. At least one measurement is performed after a Fast Fourier Transform, FFT, stage of the testing device of the at least one transmission. Compensation is performed for carrier frequency offset, CFO, phase drift in the at least one transmission based on the at least one measurement. A magnitude of phase distortion variation of the at least one transmission after the compensation of CFO phase drift is determined. The magnitude of phase distortion variation is reported.

According to one or more embodiments of the present disclosure, the at least one measurement includes data captured after the FFT stage. According to one or more embodiments of the present disclosure, the at least one measurement is configured to measure a change of channel impulse response in different time slots of the plurality of time slots. According to one or more embodiments of the present disclosure, a CFO within each slot of the plurality of slots is estimated, and a combined CFO is determined by averaging the CFOs for the plurality of slots where the compensating for CFO phase drift uses the combined CFO.

According to one or more embodiments of the present disclosure, concatenate a plurality of time slots are concatenated, and a combined CFO is determined based on the concatenated time slots over the plurality of slots, the compensating for CFO phase drift uses the combined CFO. According to one or more embodiments of the present disclosure, the compensating for CFO phase drift is performed on measurement data from a beginning symbol in a beginning time slot of the plurality of time slots to a last symbol in a last time slots over the plurality of slots. According to one or more embodiments of the present disclosure, the compensating for CFO phase drift is performed before an FFT stage.

According to one or more embodiments of the present disclosure, compensating the CFO phase drift is performed, after the FFT stage, on measurement data by deducting the CFO phase drift. According to one or more embodiments of the present disclosure, a phase distortion variation is determined using the following equation:

AO = arg

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. l is a schematic diagram of an example network architecture illustrating a communication system according to principles disclosed herein;

FIG. 2 is a block diagram of some entities in the communication system according to some embodiments of the present disclosure;

FIG. 3 is a flowchart of an example process in a testing device according to some embodiments of the present disclosure;

FIG. 4 is a flowchart of another example process in a testing device according to some embodiments of the present disclosure

FIG. 5 is a diagram of an example of phase distortion modelling on the baseband signal;

FIG. 6 is a diagram of an example of a measurement point definition for the UE coherence transmission; and

FIG. 7 is a diagram of an example of EVM testing.

DETAILED DESCRIPTION As discussed above, one problem in developing such tests of inter-slot coherence is that carrier frequency offset (CFO) may be present. In such cases, the amount of phase distortion introduced by the wireless device in addition to the phase rotation caused by CFO may be of interest because CFO relates to the wireless device mobility, frequency tracking side conditions (SNR, SSB periodicity), such that the tests should compensate for CFO while measuring this additional phase distortion. The test may focus on testing the magnitude of phase/amplitude distortion variation by RF transmitter hardware in cross time slots.

Before describing in detail exemplary embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to RF transmitter coherence measurement and/or determination based at least on compensating for carrier frequency offset (CFO) in a radio frequency (RF) transmitter.

Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication.

In some embodiments described herein, the term “coupled,” “connected,” and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and/or wireless connections.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The term “network node” used herein can be any kind of network node comprised in a radio network which may further comprise any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi -standard radio (MSR) radio node such as MSR BS, multi-cell/multicast coordination entity (MCE), relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also comprise test equipment. The term “radio node” used herein may be used to also denote a wireless device (WD) such as a wireless device (WD) or a radio network node. In some embodiments, the non-limiting terms wireless device (WD) or a user equipment (UE) are used interchangeably. The WD herein can be any type of wireless device capable of communicating with a network node or another WD over radio signals, such as wireless device (WD). The WD may also be a radio communication device, target device, device to device (D2D) WD, machine type WD or WD capable of machine to machine communication (M2M), low-cost and/or low-complexity WD, a sensor equipped with WD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), an Internet of Things (loT) device, or a Narrowband loT (NB-IOT) device etc.

Also, in some embodiments the generic term “radio network node” is used. It can be any kind of a radio network node which may comprise any of base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, Multi-cell/multicast Coordination Entity (MCE), relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH).

Transmitting in downlink may pertain to transmission from the network or network node to the wireless device. Transmitting in uplink may pertain to transmission from the wireless device to the network or network node. Transmitting in sidelink may pertain to (direct) transmission from one wireless device to another. Uplink, downlink and sidelink (e.g., sidelink transmission and reception) may be considered communication directions. In some variants, uplink and downlink may also be used to described wireless communication between network nodes, e.g. for wireless backhaul and/or relay communication and/or (wireless) network communication for example between base stations or similar network nodes, in particular communication terminating at such. It may be considered that backhaul and/or relay communication and/or network communication is implemented as a form of sidelink or uplink communication or similar thereto.

In some embodiments, the general description elements in the form of “one of A and B” corresponds to A or B. In some embodiments, at least one of A and B corresponds to A, B or AB, or to one or more of A and B. In some embodiments, at least one of A, B and C corresponds to one or more of A, B and C, and/or A, B, C or a combination thereof.

Note that although terminology from one particular wireless system, such as, for example, 3GPP LTE and/or New Radio (NR), may be used in this disclosure, this should not be seen as limiting the scope of the disclosure to only the aforementioned system. Other wireless systems, including without limitation Wide Band Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB) and Global System for Mobile Communications (GSM), may also benefit from exploiting the ideas covered within this disclosure.

Note further, that functions described herein as being performed by a wireless device or a network node may be distributed over a plurality of wireless devices and/or network nodes. In other words, it is contemplated that the functions of the network node and wireless device described herein are not limited to performance by a single physical device and, in fact, can be distributed among several physical devices.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Some embodiments are directed to RF transmitter coherence measurement and/or determination based at least on compensating for carrier frequency offset (CFO) in a radio frequency (RF) transmitter.

Referring to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in FIG. 1 a schematic diagram of a communication system 10, according to an embodiment, such as a 3 GPP -type cellular network that may support standards such as LTE and/or NR (5G), which comprises an access network 12, such as a radio access network, and a core network 14. The access network 12 comprises a plurality of network nodes 16a, 16b, 16c (referred to collectively as network nodes 16), such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (referred to collectively as coverage areas 18). Each network node 16a, 16b, 16c is connectable to the core network 14 over a wired or wireless connection 20. System 10 may include one or more testing devices 21 for RF transmitter coherence measurement and/or determination based at least on compensating for carrier frequency offset (CFO) in a radio frequency (RF) transmitter. In one or more embodiments, testing device 21 may be configured to detect/measure/receive communications between wireless device 22 and network node 16, and/or may be configured to perform communications with wireless device 22.

A first wireless device (WD) 22a located in coverage area 18a is configured to wirelessly connect to, or be paged by, the corresponding network node 16a. A second WD 22b in coverage area 18b is wirelessly connectable to the corresponding network node 16b. While a plurality of WDs 22a, 22b (collectively referred to as wireless devices 22) are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole WD is in the coverage area or where a sole WD is connecting to the corresponding network node 16. Note that although only two WDs 22 and three network nodes 16 are shown for convenience, the communication system may include many more WDs 22 and network nodes 16.

Also, it is contemplated that a WD 22 can be in simultaneous communication and/or configured to separately communicate with more than one network node 16 and more than one type of network node 16. For example, a WD 22 can have dual connectivity with a network node 16 that supports LTE and the same or a different network node 16 that supports NR. As an example, WD 22 can be in communication with an eNB for LTE/E-UTRAN and a gNB for NR/NG-RAN.

A testing device 21 is configured to include a compensation unit 24 which is configured to perform one or more testing device 21 functions as described herein such as with respect to RF transmitter coherence measurement and/or determination based at least on compensating for carrier frequency offset (CFO) in a radio frequency (RF) transmitter, as described herein.

Example implementations, in accordance with an embodiment, of the WD 22 and testing device 21 discussed in the preceding paragraphs will now be described with reference to FIG. 2. While not shown in FIG. 2, network node 16 may include similar hardware and/or software as wireless device 22, but with the hardware and/or software configured to perform network node 16 functions.

The communication system 10 includes a testing device 21 provided in a communication system 10 and including hardware 28 enabling it to communicate and/or receive transmissions from one or more WDs 22. The hardware 28 may include a radio interface 30 for receiving wireless communications from WD 22. The radio interface 30 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and/or one or more RF transceivers. The radio interface 30 may include an array of antennas to receive signal(s) carrying electromagnetic waves.

In the embodiment shown, the hardware 28 of the testing device 21 further includes processing circuitry 36. The processing circuitry 36 may include a processor 38 and a memory 40. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 36 may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 38 may be configured to access (e.g., write to and/or read from) the memory 40, which may comprise any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read-Only Memory).

Thus, the testing device 21 further has software 42 stored internally in, for example, memory 40, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the testing device 21 via an external connection. The software 42 may be executable by the processing circuitry 36. The processing circuitry 36 may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by testing device 21. Processor 38 corresponds to one or more processors 38 for performing testing device 21 functions described herein. The memory 40 is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software 42 may include instructions that, when executed by the processor 38 and/or processing circuitry 36, causes the processor 38 and/or processing circuitry 36 to perform the processes described herein with respect to testing device 21. For example, processing circuitry 36 of the testing device 21 may include compensation unit 24 which is configured to perform one or more testing device 21 functions as described herein. In particular, hardware 28 and/or software 42 may be configured to provide the functional blocks of testing device 21 illustrated in FIG. 6 such as DC, RF impairment compensation, FFT, channel estimation, equalization, demodulation, etc. and may be configured to perform one or more testing device 21 functions as described herein such as, for example, measurements at one or more reference points, as described herein.

The communication system 10 further includes the WD 22 already referred to. The WD 22 may have hardware 44 that may include a radio interface 45 configured to set up and maintain a wireless connection with a network node 16 serving a coverage area 18 in which the WD 22 is currently located. The radio interface 45 may be formed as or may include, for example, one or more RF transmitters 46, one or more RF receivers, and/or one or more RF transceivers.

The hardware 44 of the WD 22 further includes processing circuitry 48. The processing circuitry 48 may include a processor 50 and memory 52. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 48 may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 50 may be configured to access (e.g., write to and/or read from) memory 52, which may comprise any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read-Only Memory).

Thus, the WD 22 may further comprise software 54, which is stored in, for example, memory 52 at the WD 22, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the WD 22. The software 54 may be executable by the processing circuitry 48. The software 54 may include a client application 56. The client application 56 may be operable to provide a service to a human or non-human user via the WD 22. The client application 56 may interact with the user to generate the user data that it provides.

The processing circuitry 48 may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by WD 22. The processor 50 corresponds to one or more processors 50 for performing WD 22 functions described herein. The WD 22 includes memory 52 that is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software 54 and/or the client application 56 may include instructions that, when executed by the processor 50 and/or processing circuitry 48, causes the processor 50 and/or processing circuitry 48 to perform the processes described herein with respect to WD 22. For example, wireless device may cause transmission of one or more signals to a network node 16 where the one or more signals may be received by the network node 16 and/or testing device 21.

In some embodiments, the functions of testing device 21 may be configured to be performed by network node 16 and/or another entity in system 10 that is able to receive wireless communications from wireless device 22.

Although FIGS. 1 and 2 show a “unit” such as compensation unit 24 as being within a respective processor, it is contemplated that these units may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuitry. In other words, the units may be implemented in hardware or in a combination of hardware and software within the processing circuitry.

FIG. 3 is a flowchart of an example process in a testing device 21 according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of testing device 21 such as by one or more of processing circuitry 36 (including the compensation unit 24), processor 38, and/or radio interface 30. Testing device 21 is configured to determine (Block S100) a radio frequency, RF, transmitter coherence with respect to phase and amplitude variation in a frequency response of a RF transmitter 46 over a plurality of slots where the determination includes compensating for carrier frequency offset, CFO, phase drift one of before a Fast Fourier Transform, FFT, stage and after the FFT stage of the RF transmitter 46 based at least on measurement performed one of after the FFT stage and after an equalization stage of the RF transmitter 46, as described herein. Testing device 21 is further configured to report (Block SI 02) the determined RF transmitter coherence, as described herein. In one or more embodiments, the reported RF transmitted coherence may be used to adjust at least one communication parameter at the wireless device 22 and/or network node 16.

According to one or more embodiments, the measurement is configured to measure a change of channel impulse in different time slots of the plurality of time slots. According to one or more embodiments, the compensation for CFO phase drift before the FFT stage includes one of: determining, e.g., calculating, the CFO phase drift for each slot of the plurality of slots and averaging the CFOs for the plurality of slots; and determining the CFO phase drift over at least two slots of the plurality of slots. According to one or more embodiments, the compensation for CFO phase drift includes using an error vector magnitude, EVM, process to determine equalizer coefficients to equalize at least one time slot data symbol and reference signal.

FIG. 4 is a flowchart of an example process in a testing device 21 according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of testing device 21 such as by one or more of processing circuitry 36 (including the compensation unit 24), processor 38, and/or radio interface 30. Testing device 21 is configured to receive (Block S106), from a wireless device 22, at least one transmission over a plurality of slots, as described herein. Testing device 21 is configured to perform (Block S108) at least one measurement after a Fast Fourier Transform, FFT, stage of the testing device of the at least one transmission, as described herein. Testing device 21 is configured to compensate (Block SI 10) for carrier frequency offset, CFO, phase drift in the at least one transmission based on the at least one measurement, as described herein. Testing device 21 is configured to determine (Block SI 12) a magnitude of phase distortion variation of the at least one transmission after the compensation of CFO phase drift, as described herein. Testing device 21 is configured to report (Block SI 14) the magnitude of phase distortion variation, as described herein.

According to one or more embodiments, the at least one measurement includes data captured after the FFT stage. According to one or more embodiments, the at least one measurement is configured to measure a change of channel impulse response in different time slots of the plurality of time slots. According to one or more embodiments, the processing circuitry 36 is further configured to estimate a CFO within each slot of the plurality of slots, and determine a combined CFO by averaging the CFOs for the plurality of slots, the compensating for CFO phase drift uses the combined CFO.

According to one or more embodiments, the processing circuitry 36 is further configured to: concatenate a plurality of time slots, and determine a combined CFO based on the concatenated time slots over the plurality of slots, the compensating for CFO phase drift uses the combined CFO. According to one or more embodiments, the compensating for CFO phase drift is performed on measurement data from a beginning symbol in a beginning time slot of the plurality of time slots to a last symbol in a last time slots over the plurality of slots. According to one or more embodiments, the compensating for CFO phase drift is performed before an FFT stage.

According to one or more embodiments, compensating the CFO phase drift is performed, after the FFT stage, on measurement data by deducting the CFO phase drift. According to one or more embodiments, the processing circuitry is further configured to determine a phase distortion variation using the following equation:

AO = arg

mod (27tAf(t2-tl), 2K), where A0 is a phase distortion variation, A is an estimated carrier frequency offset, and mod (27tAf(t2-tl), 2K) is the CFO phase drift, and the magnitude of the phase distortion variation being based on the phase distortion variation.

According to one or more embodiments, the determining of the magnitude of phase distortion variation includes: determining a channel impulse response for a first time slot and a second time slot where the first time slot and second time slot is one of consecutive and non-consecutive time slots, and determining a phase distortion variation of the channel impulse response of a wireless device between the first time slot and second time slot using the following equation:

A0 = arg

Where A0 is a phase distortion variation, tl is the first time slot, and t2 is the second time slot, and the magnitude of the phase distortion variation is based on the phase distortion variation. According to one or more embodiments, the compensating for CFO phase drift includes: acquiring a set of samples of a signal associated with the at least one transmission over the plurality of slots, and varying at least one of a sample timing, carrier frequency and carrier leakage of the set of samples to produce an adjusted signal having a minimal difference from a reference signal. According to one or more embodiments, the compensating for CFO phase drift includes determining discrete Fourier transforms, DFTs, of each of a first portion and second portion of the adjusted signal where the first portion is in a different slot than the second portion, and the magnitude of phase distortion variation is based on the determined DFTs of each of the first portion and second portion of the adjusted signal. According to one or more embodiments, the determining of the magnitude of phase distortion variation of the at least one transmission after the compensation of CFO phase drift is based on the testing device assuming that hardware of the wireless device keeps CFO phase drift constant where the hardware 44 of the wireless device includes the RF transmitter of the wireless device 22. According to one or more embodiments, the determining of RF transmitter coherence of the wireless device 22 is performed with respect to an amplitude variation of the frequency response of the RF transmitter over the plurality of slots.

Having generally described arrangements for RF transmitter coherence measurement and/or determination based at least on compensating for carrier frequency offset (CFO) in a radio frequency (RF) transmitter, details for these arrangements, functions and processes are provided as follows, and which may be implemented by the testing device 21.

One or more testing device 21 functions described below may be performed by one or more of processing circuitry 36, processor 38, compensation unit 24, radio interface 30, etc. One or more wireless device 22 functions described below may be performed by one or more of processing circuitry 48, processor 50, RF transmitter 46, radio interface 45, etc.

Some embodiments provide for RF transmitter coherence measurement and/or determination based at least on compensating for carrier frequency offset (CFO) in a radio frequency (RF) transmitter. One source of the phase distortion on the baseband signal comes from the up- conversion, power amplifier. FIG. 5 is a diagram that illustrates the modelling of the phase distortion when baseband signal is upconverted and transmitted from the wireless device 22 RF transmitter chain (i.e., part of RF transmitter 46). The RF transmitter 46 includes a digital baseband 58, mixer 60, local oscillator 62, power amplifier 64 (PA 64) and radio frequency (RF) tuning 66.

For the up-conversion, the phase distortion comes from the local oscillator when the baseband signal is mixing with frequency offset to generate the RF signal. The second source of the phase and amplitude distortion comes from the power amplifier. To save the wireless device 22 power, the PA is operated near its saturation points to improve the power efficiency, which leads to the non-linear distortion. This is characterized by the amplitude to amplitude and amplitude to phase modulation on the baseband signal.

FIG. 6 is a diagram of a measurement point definition of testing device 21 for the wireless device 22 coherence transmission according to one or more embodiments of the present disclosure.

To measure the frequency response of wireless device 22 RF chain (wireless device 22 baseband 58, mixer 60, UC 68 (e.g., upconverter 68)), a measurement reference point is defined. Testing device 21 may include the following functional blocks provided by hardware 28 and/or software 42: DC 70 (e.g., digital converter 70), RF impairment compensation 72, FFT 74, channel estimation 76, equalization 78 and decomodulation 80 (or demodulation 80). A reference point is used to indicate where the measured data is captured in a signal processing chain. A reference point 1 in FIG. 6 is defined after the FFT 74 but before the channel estimation. And A reference point 2 in FIG. 6 is defined after the equalization. RF impairment compensation 72 in FIG. 6 may compensate the frequency offset in wireless device 22 and also any time error when estimating the frame timing start.

In one or more embodiments, the UL transmissions in the slots to be tested may be a PUSCH/PUCCH transmission or a PUSCH/PUCCH repetition, or different parts of a TB transmission on PUSCH (transport block over multiple slots), or different UL transmissions with different contents scheduled by configured grant or dynamic grant (can be a single dynamic grant scheduling multi -PUSCH or be multiple dynamic grants).

One embodiment to measure the phase and amplitude coherence in the wireless device 22 RF transmitter 46 is to measure the change of channel impulse response in different time slot TS1 and TS2.

For example, channel impulse response for TS1 is

A(tl,f)e^ie(tl’^f)= M(tl,f)/I(tl,f) (E-l) and channel impulse response for TS2 is

A(t2,f)e’^e(t2,f)= M(t2,f)/I(t2,f) (E-2) where M(tl,f) is post-FFT measured at reference point 1. 1(tl,f) is ideal reference signal.

The phase variation of the channel impulse response of wireless device 22 RF transmitter between TS1 and TS2 is :

AO = arg

(_E-3)

The amplitude variation in dB of the channel impulse response of wireless device 22 RF transmitter 46 between TS1 and TS2 is:

AA = 201ogio(A(t2,f)/ A(tl,f))

In some embodiment, TS1, TS2 are 2 consecutive slots, while in some embodiment, TS1 and TS2 may have a gap (e.g., time gap) between each other.

While the wireless device 22 may control the phase between slots of a transmitted signal, it may be difficult for the wireless device 22 to transmit without frequency error. This frequency error does not preclude the benefits of joint channel estimation if it can be corrected for by the network node 16 receiver. Therefore, the testing methods performed by testing device 21 herein consider where the phase variation includes the frequency error caused phase change and where it may be corrected for in the test, and here it may be deducted from the calculation. The reason is that in FIG. 6, the RF impairment compensation 72 is performed on a per time slot basis and there is no phase drift compensation between the different time slots.

To consider the CFO (Af) impact, the additional phase drift of 27tAf(t2- tl) caused by frequency offset is deducted in (E-3) and the phase variation caused by wireless device 22 RF transmission can be measured with the below magnitude:

AO = arg (e>^(e(t2>f)' ^e(tl>f)))- mod (27tAf(t2-tl), 2-JI) (E-4) The Mod(a, b) is the modulo operation which means the remainder after division.

The above compensation provides better performance when the CFO is constant or close to constant between the two time slots TS1 and TS2 versus when the CFO is not close to constant.

The CFO compensation is performed by testing device 21 per slot individually in pre FFT in this embodiment.

Another embodiment relates to the combined CFO compensation in pre FFT processing. Such pre FFT processing may require knowledge or estimation of the CFO for each time slot. In some cases, it may be beneficial that CFO is kept constant between different repetition slots, such as where CFO estimates are calculated over multiple slots to improve estimation.

In some embodiment, the combined CFO is derived based on a combined slot, while in some embodiment, the combined CFO is an average CFO derived based on multiple CFOs with each estimated every single slot (at least 2 DMRS symbols in a slot in this case) or 2 consecutive slots or every 2 non-consecutive slots among all the slots combined.

For example, assuming there are three time slots for the repetition transmission in total, and there is no gap between these repetition time slots, the measured signal before the FFT can be processed as below:

1. The measurement data in different time slots data are concatenated,

2. The CFO is estimated in the individual single slots and averaged to get better accuracy, alternatively, the CFO is estimated in the concatenated time slot data.

3. The CFO compensation is performed on measurement data combining different time slots from the first symbol in the first time slot to the last symbol in the last time slots.

- In some cases, the CFO may be jointly estimated with other parameters such as the sample timing and/or carrier leakage to produce a jointly optimized set of parameters. This joint estimation may compare the received pre-FFT samples to a reference signal using an RMS difference between the reference signal and the received signal adjusted according to the estimated parameters. Such an optimization may be performed according to the pre FFT minimization process described in section E.3.1 of 3GPP TS 38.521.

A benefit of the CFO compensation in pre FFT processing is that there is no need to further compensate the CFO and, hence the phase variation caused by wireless device 22 RF transmission can be derived without the complexity of determining the CFO after the FFT, and equation (E-5) below can be used:

AO = arg

(E-5)

Therefore, in an embodiment, a testing device 21 measures phase differences between subsequent transmissions of a signal when the signal may be offset from a carrier frequency. The testing device 21 acquires a set of samples of the signal. It jointly varies the sample timing, carrier frequency, and carrier leakage of the set of samples to produce an adjusted signal, where the adjusted signal has a minimal difference from a reference signal. It further computes discrete Fourier transforms (DFTs) of each of at least a first and a second portion the adjusted signal, where each portion includes an OFDM symbol, and at least the first and second portions are in different slots, producing at least a first and a second DFT output.

The testing device 21 calculates a phase difference between the at least first and second DFT outputs and reports the phase difference. The carrier frequency of testing device 21 may need to be configured to different frequency range within a frequency band.

Another embodiment is to test the wireless device 22 hardware to keep the CFO constant over some predefined interval. For example, there is non-zero gap between the repetition transmission and wireless device 22 needs to keep the CFO constant between the two repetition transmissions including the non-zero gap period. In such a case, the pre FFT processing could be modified with below assuming such interval is At:

1. The measurement data in different time slots data are concatenated,

2. The CFO is estimated in the single time slot per slots.

3. The CFO (Af) compensation is performed individually for each time slot, additionally the phase drift between the non-zero gap with the magnitude 27tAfAt needs to be compensated. With the CFO compensation in the pre FFT process, there may be no need to compensate the CFO, and hence phase variation caused by wireless device 22 RF transmission can be derived with equation (E-5).

In another embodiment, the EVM (e.g., error vector magnitude) is used by testing device 21 to measure the phase and amplitude coherence in wireless device 22 RF transmitter 46. Assuming there are two transmission time slots for repetition transmission TS1 and TS2, the channel impulse response in different time slot, e.g., in TS1 will be

A(tl,f)e^ie(tl’^f)= M(tl,f)/I(tl,f) (E-6)

The equalizer coefficients could be derived from this

EC(t,f)= l/(A(tl,f)e’^e(tl,f)) (E-7)

In one example, the first slots equalization coefficients is used to equalize the second time slot data symbol and reference symbol and get the equalized data M’(t2,f).

M’(t2,f) = M(t2,f)* EC(t,f)

In such a case, the EVM measured will be according to FIG. 7.

The phase error contains three components, phase error component caused by RF impairment, phase error caused by CFO and phase error caused by the phase response difference between the two time slots. For the phase error caused by CFO, it can be compensated in the phase of complex number of EC coefficient as below: arg (EC(t,f))= arg(e^j(e(tl’^f)-^inod(2’^lAf(t2-^tl)’²’^l))) (E-8)

Alternatively, the CFO compensation can be performed in pre FFT processing with one or more of the above embodiments.

Some Examples

Example 1. Method to derive the capability performance for wireless device 22 TX coherence transmission in terms of the phase and magnitude variation with consideration of the CFO compensation before or after FFT processing, using one or more of the following alternatives:

- Before FFT/DFT, Preprocessing the concatenated data set to compensate the CFO phase drift between time slots Pre FFT;

After FFT/DFT, processing the concatenated data set to compensate the CFO phase drift between time slots; Preprocessing the concatenated data set to compensate the CFO in combined time slot at pre FFT and not compensate the CFO phase drift between time slots Post FFT. o In one case, all slots are assumed have the same CFO (e.g., same CFO phase drift) o In another case, the total number of slots are grouped into different subsets, each subsets of the slots are assumed to have same CFO.

Example 2. Use the EVM testing procedure to measure the TX RF coherence transmission with below modifications: derive the equalization coefficient from first transmission time slot and apply this equalization coefficients to the second repetition time slot.

Compensate the CFO in the pre FFT processing, or alternatively compensate the CFO in the equalization coefficient before applying it to the second transmission time slot.

In more detail, some embodiments herein can be further summarized:

Example 3. A method in a testing device 21 of measuring phase and amplitude differences between subsequent transmissions of signal when the signal may be offset from a carrier frequency, the method including:

Acquiring a set of samples of the signal

Jointly varying the sample timing, carrier frequency, and carrier leakage of the set of samples to produce an adjusted signal, where the adjusted signal has a minimal difference from a reference signal

Computing discrete Fourier transforms (DFTs) of each of at least a first and a second portion the adjusted signal, wherein each portion includes an OFDM symbol, and at least the first and second portions are in different slots, producing at least a first and a second DFT output

- Determining a phase and amplitude difference between the at least first and second DFT outputs; and

- Reporting the phase and amplitude difference.

Other Examples Example Al. A testing device 21 configured to receive transmissions from a wireless device 22, the testing device 21 configured to, and/or comprising a radio interface 30 and/or processing circuitry 36 configured to: determine a radio frequency, RF, transmitter coherence of the wireless device 22 with respect to phase and amplitude variation in a frequency response of a RF transmitter over a plurality of slots, the determination including compensating for carrier frequency offset, CFO, phase drift one of before a Fast Fourier Transform, FFT, stage and after the FFT stage of the RF transmitter based at least on measurement performed one of after the FFT stage and after an equalization stage of the RF transmitter 46; and report the determined RF transmitter coherence.

Example A2. The testing device 21 of Example Al, wherein the measurement is configured to measure a change of channel impulse in different time slots of the plurality of time slots.

Example A3. The testing device 21 of Example Al, wherein the compensation for CFO phase drift before the FFT stage includes one of determining the CFO phase drift for each slot of the plurality of slots and averaging the CFOs for the plurality of slots; and determining the CFO phase drift over at least two slots of the plurality of slots.

Example A4. The testing device 21 of Example Al, wherein the compensation for CFO phase drift includes using an error vector magnitude, EVM, process to determine equalizer coefficients to equalize at least one time slot data symbol and reference signal.

Example Bl. A method implemented in a testing device 21 that is configured to receive transmissions from a wireless device 22, the method comprising: determining a radio frequency, RF, transmitter coherence of the wireless device 22 with respect to phase and amplitude variation in a frequency response of a RF transmitter over a plurality of slots, the determination including compensating for carrier frequency offset, CFO, phase drift one of before a Fast Fourier Transform, FFT, stage and after the FFT stage of the RF transmitter based at least on measurement performed one of after the FFT stage and after an equalization stage of the RF transmitter 46. Example B2. The method of Example Bl, wherein the measurement is configured to measure a change of channel impulse in different time slots of the plurality of time slots.

Example B3. The method of Example Bl, wherein the compensation for CFO phase drift before the FFT stage includes one of: determining the CFO phase drift for each slot of the plurality of slots and averaging the CFOs for the plurality of slots; and determining the CFO phase drift over at least two slots of the plurality of slots.

Example B4. The method of Example Bl, wherein the compensation for CFO phase drift includes using an error vector magnitude, EVM, process to determine equalizer coefficients to equalize at least one time slot data symbol and reference signal.

As will be appreciated by one of skill in the art, the concepts described herein may be embodied as a method, data processing system, computer program product and/or computer storage media storing an executable computer program. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Any process, step, action and/or functionality described herein may be performed by, and/or associated to, a corresponding module, which may be implemented in software and/or firmware and/or hardware. Furthermore, the disclosure may take the form of a computer program product on a tangible computer usable storage medium having computer program code embodied in the medium that can be executed by a computer. Any suitable tangible computer readable medium may be utilized including hard disks, CD-ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.

Some embodiments are described herein with reference to flowchart illustrations and/or block diagrams of methods, systems and computer program products. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer (to thereby create a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer readable memory or storage medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

It is to be understood that the functions/acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

Computer program code for carrying out operations of the concepts described herein may be written in an object oriented programming language such as Python, Java® or C++. However, the computer program code for carrying out operations of the disclosure may also be written in conventional procedural programming languages, such as the "C" programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

Many different embodiments have been disclosed herein, in connection with the above description and the drawings. It will be understood that it would be unduly repetitious and obfuscating to literally describe and illustrate every combination and subcombination of these embodiments. Accordingly, all embodiments can be combined in any way and/or combination, and the present specification, including the drawings, shall be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination.

Abbreviations that may be used in the preceding description include:

Abbreviation Explanation

CFO Carrier Frequency Offset

DFT Discrete Fourier Transform

EVM Error Vector Magnitude

It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A testing device comprising:

I processing circuitry configured to: receive, from a wireless device, at least one transmission over a plurality of slots; perform at least one measurement after a Fast Fourier Transform, FFT, stage of the testing device of the at least one transmission; compensate for carrier frequency offset, CFO, phase drift in the at least one transmission based on the at least one measurement; determine a magnitude of phase distortion variation of the at least one transmission after the compensation of CFO phase drift; and report the magnitude of phase distortion variation.

2. The testing device of Claim 1, wherein the at least one measurement includes data captured after the FFT stage.

3. The testing device of any one of Claims 1-2, wherein the at least one measurement is configured to measure a change of channel impulse response in different time slots of the plurality of time slots.

4. The testing device of any one of Claims 1-3, wherein the processing circuitry is further configured to: estimate a CFO within each slot of the plurality of slots; determine a combined CFO by averaging the CFOs for the plurality of slots, the compensating for CFO phase drift uses the combined CFO.

5. The testing device of any one of Claims 1-3, wherein the processing circuitry is further configured to: concatenate a plurality of time slots; and determine a combined CFO based on the concatenated time slots over the plurality of slots, the compensating for CFO phase drift uses the combined CFO.

6. The testing device of any one of Claims 1-3, wherein the compensating for CFO phase drift is performed on measurement data from a beginning symbol in a beginning time slot of the plurality of time slots to a last symbol in a last time slots over the plurality of slots.

7. The testing device of any of claims 1-6, wherein the compensating for CFO phase drift is performed before an FFT stage.

8. The testing device of any one of Claims 1-7, wherein compensating the CFO phase drift is performed, after the FFT stage, on measurement data by deducting the CFO phase drift.

9. The testing device of any one of Claims 1-8, wherein the processing circuitry is further configured to determine a phase distortion variation using the following equation:

AO = arg

mod (27tAf(t2-tl), 2K), where:

A0 is a phase distortion variation;

A is an estimated carrier frequency offset; and mod (27tAf(t2-tl), 2K) is the CFO phase drift; and the magnitude of the phase distortion variation being based on the phase distortion variation.

10. The testing device of any one of Claims 1-9, wherein the determining of the magnitude of phase distortion variation includes: determining a channel impulse response for a first time slot and a second time slot, the first time slot and second time slot being one of consecutive and non- consecutive time slots; determining a phase distortion variation of the channel impulse response of a wireless device between the first time slot and second time slot using the following equation: AO = arg (ert⁰^- <«) where:

A0 is a phase distortion variation; tl is the first time slot; and t2 is the second time slot; and the magnitude of the phase distortion variation being based on the phase distortion variation.

11. The testing device of any one of Claims 1-9, wherein the compensating for CFO phase drift includes: acquiring a set of samples of a signal associated with the at least one transmission over the plurality of slots; and varying at least one of a sample timing, carrier frequency and carrier leakage of the set of samples to produce an adjusted signal having a minimal difference from a reference signal.

12. The testing device of Claim 11, wherein the compensating for CFO phase drift includes: determining discrete Fourier transforms, DFTs, of each of a first portion and second portion of the adjusted signal, the first portion being in a different slot than the second portion; and the magnitude of phase distortion variation being based on the determined DFTs of each of the first portion and second portion of the adjusted signal.

13. The testing device of any one of Claims 1-12, wherein the determining of the magnitude of phase distortion variation of the at least one transmission after the compensation of CFO phase drift is based on the testing device assuming that hardware of the wireless device keeps CFO phase drift constant, the hardware of the wireless device including the RF transmitter of the wireless device.

14. The testing device of any one of Claims 1-13, wherein the determining of RF transmitter coherence of the wireless device is performed with respect to an amplitude variation of the frequency response of the RF transmitter over the plurality of slots.

15. A method implemented by a testing device, the method comprising: receiving, from a wireless device, at least one transmission over a plurality of slots; performing at least one measurement after a Fast Fourier Transform, FFT, stage of the testing device of the at least one transmission; compensating for carrier frequency offset, CFO, phase drift in the at least one transmission based on the at least one measurement; determining a magnitude of phase distortion variation of the at least one transmission after the compensation of CFO phase drift; and reporting the magnitude of phase distortion variation.

16. The method of Claim 15, wherein the at least one measurement includes data captured after the FFT stage.

17. The method of any one of Claims 15-16, wherein the at least one measurement is configured to measure a change of channel impulse response in different time slots of the plurality of time slots.

18. The method of any one of Claims 15-17, further comprising: estimating a CFO within each slot of the plurality of slots; and determining a combined CFO by averaging the CFOs for the plurality of slots, the compensating for CFO phase drift uses the combined CFO.

19. The method of any one of Claims 15-17, further comprising: concatenating a plurality of time slots; and determining a combined CFO based on the concatenated time slots over the plurality of slots, the compensating for CFO phase drift uses the combined CFO.

20. The method of any one of Claims 15-17, wherein the compensating for CFO phase drift is performed on measurement data from a beginning symbol in a beginning time slot of the plurality of time slots to a last symbol in a last time slots over the plurality of slots.

21. The method of any of claims 15-20, wherein the compensating for CFO phase drift is performed before an FFT stage.

22. The method of any one of Claims 15-21, wherein compensating the CFO phase drift is performed, after the FFT stage, on measurement data by deducting the CFO phase drift.

23. The method of any one of Claims 15-22, further comprising determining a phase distortion variation using the following equation:

AO = arg

tl), 2K), where:

A0 is a phase distortion variation;

24. The method of any one of Claims 15-23, wherein the determining of the magnitude of phase distortion variation includes: determining a channel impulse response for a first time slot and a second time slot, the first time slot and second time slot being one of consecutive and non- consecutive time slots; determining a phase distortion variation of the channel impulse response of a wireless device between the first time slot and second time slot using the following equation:

A0 = arg

where:

25. The method of any one of Claims 15-23, wherein the compensating for CFO phase drift includes: acquiring a set of samples of a signal associated with the at least one transmission over the plurality of slots; and varying at least one of a sample timing, carrier frequency and carrier leakage of the set of samples to produce an adjusted signal having a minimal difference from a reference signal.

26. The method of Claim 25, wherein the compensating for CFO phase drift includes: determining discrete Fourier transforms, DFTs, of each of a first portion and second portion of the adjusted signal, the first portion being in a different slot than the second portion; and the magnitude of phase distortion variation being based on the determined DFTs of each of the first portion and second portion of the adjusted signal.

27. The method of any one of Claims 15-26, wherein the determining of the magnitude of phase distortion variation of the at least one transmission after the compensation of CFO phase drift is based on the testing device assuming that hardware of the wireless device keeps CFO phase drift constant, the hardware of the wireless device including the RF transmitter of the wireless device.

28. The method of any one of Claims 15-27, wherein the determining of RF transmitter coherence of the wireless device is performed with respect to an amplitude variation of the frequency response of the RF transmitter over the plurality of slots.