WO2015023297A1

WO2015023297A1 - Method and apparatus for mitigating relative-phase discontinuity

Info

Publication number: WO2015023297A1
Application number: PCT/US2013/055375
Authority: WO
Inventors: Jun Tan; Rapeepat Ratasuk; Weidong Yang
Original assignee: Nokia Siemens Networks Oy
Priority date: 2013-08-16
Filing date: 2013-08-16
Publication date: 2015-02-19

Abstract

Methods and apparatuses can be configured to determine a relative-phase-discontinuity profile of a user equipment. One method can also include performing a scheduling scheme based on the relative phase discontinuity of the user equipment.

Description

METHOD AND APPARATUS FOR MITIGATING RELATIVE-PHASE

DISCONTINUITY

BACKGROUND:

Field:

[0001] Embodiments of the invention relate to mitigating the effects of relative -phase discontinuity.

Description of the Related Art:

[0002] Long-term Evolution (LTE) is a standard for wireless communication that seeks to provide improved speed and capacity for wireless communications by using new modulation/signal processing techniques. The standard was proposed by the 3^rd Generation Partnership Project (3GPP), and is based upon previous network technologies. Since its inception, LTE has seen extensive deployment in a wide variety of contexts involving the communication of data.

SUMMARY:

[0003] According to a first embodiment, a method can include determining a relative -phase-discontinuity profile of a user equipment. The method can also include performing a scheduling scheme based on the relative phase discontinuity of the user equipment.

[0004] In the method of the first embodiment, the determining comprises determining a profile that comprises a set of user-equipment transmission- power amplifier stages and related ramping-up/down switching points.

[0005] In the method of the first embodiment, the determining comprises receiving, via signaling, the profile or estimating the profile using historical Random-Access-Channel/Sounding-Reference-Signal/Physical-Uplink- Shared-Channel transmissions for the user equipment.

[0006] In the method of the first embodiment, the performing comprises predicting whether there is a power-amplifier mode- switching event. [0007] According to a second embodiment, an apparatus can include at least one processor. The apparatus can also include at least one memory including computer program code. The at least one memory and the computer program code can be configured, with the at least one processor, to cause the apparatus at least to determine a relative -phase-discontinuity profile of a user equipment. The apparatus can also perform a scheduling scheme based on the relative phase discontinuity of the user equipment.

[0008] In the apparatus of the second embodiment, the determining comprises determining a profile that comprises a set of user-equipment transmission- power amplifier stages and related ramping-up/down switching points.

[0009] In the apparatus of the second embodiment, the determining comprises receiving, via signaling, the profile or estimating the profile using historical andom-Access-Channel/Sounding- eference-Signal/Physical-Uplink- Shared-Channel transmissions for the user equipment.

[0010] In the apparatus of the second embodiment, the performing comprises predicting whether there is a power-amplifier mode- switching event.

[0011] According to a third embodiment, a computer program product can be embodied on a non-transitory computer readable medium. The computer program product can be configured to control a processor to perform a process including determining a relative -phase-discontinuity profile of a user equipment. The process can also include performing a scheduling scheme based on the relative phase discontinuity of the user equipment.

[0012] According to a fourth embodiment, a method can include determining that a user equipment's transmitting will be impacted by relative -phase discontinuity. The method can also include adjusting the user equipment's transmitting to reduce the impact to the transmission.

[0013] In the method of the fourth embodiment, the determining comprises determining that a change in the user equipment's transmission power will cause the user equipment's transmitting to be impacted by the relative -phase discontinuity.

[0014] In the method of the fourth embodiment, the adjusting the user equipment's transmitting comprises adjusting the user equipment's transmission power.

[0015] In the method of the fourth embodiment, the adjusting the user equipment's transmitting comprises performing an override of a pre-coding matrix indicator.

[0016] In the method of the fourth embodiment, the adjusting the user equipment's transmitting comprises performing pre-distortion adjustment.

[0017] According to a fifth embodiment, an apparatus can include at least one processor. The apparatus can include at least one memory including computer program code. The at least one memory and the computer program code can be configured, with the at least one processor, to cause the apparatus at least to determine that the apparatus' transmitting will be impacted by relative -phase discontinuity. The apparatus can also adjust the apparatus' transmitting to reduce the impact to the transmission.

[0018] In apparatus of the fifth embodiment, the determining comprises determining that a change in the apparatus' transmission power will cause the apparatus' transmitting to be impacted by the relative -phase discontinuity.

[0019] In the apparatus of the fifth embodiment, the adjusting the apparatus' transmitting comprises adjusting the apparatus' transmission power.

[0020] In the apparatus of the fifth embodiment, the adjusting the apparatus' transmitting comprises performing an override of a pre-coding matrix indicator.

[0021] In the apparatus of the fifth embodiment, the adjusting the apparatus' transmitting comprises performing pre-distortion adjustment. [0022] According to a sixth embodiment, a computer program product can be embodied on a non-transitory computer readable medium. The computer program product can be configured to control a processor to perform a process. The process can comprise determining that a user equipment's transmitting will be impacted by relative-phase discontinuity. The process can also include adjusting the user equipment's transmitting to reduce the impact to the transmission.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0023] For proper understanding of the invention, reference should be made to the accompanying drawings, wherein:

[0024] Fig. 1 illustrates uplink performance degradation due to relative -phase discontinuity (RPD).

[0025] Fig. 2 illustrates an exemplary table of phase changes.

[0026] Fig. 3 illustrates a flowchart of a method in accordance with embodiments of the invention.

[0027] Fig. 4 illustrates a flowchart of a method in accordance with embodiments of the invention.

[0028] Fig. 5 illustrates an apparatus in accordance with embodiments of the invention.

[0029] Fig. 6 illustrates an apparatus in accordance with embodiments of the invention.

[0030] Fig. 7 illustrates an apparatus in accordance with embodiments of the invention.

DETAILED DESCRIPTION:

[0031] Embodiments of the present invention address the impact of relative- phase discontinuity (RPD) on transmissions, such as uplink (UL) single-user multiple-input-multiple-output (SU-MIMO) transmissions. As a user equipment (UE) transmits a transmission, if the transmission power of the UE changes, the signal phase of the transmission can shift in time. Phase changes among multiple transmitting antennas can impact close-loop MIMO performance, when the special-reference symbol (SRS) measurement does not provide accurate precoding matrix selection for physical-uplink-shared channel (PUSCH) transmission in long-term evolution (LTE). Performance degradation can be caused by precoding vector mismatch due to a relative phase difference when the SRS was transmitted as compared to when the PUSCH is transmitted. Example uplink performance degradation is described in R4-1 1 1946, and Fig. 1 illustrates uplink performance degradation.

[0032] In general, the resulting performance degradation is negligible at small relative -phase discontinuity (RPD) values, but the performance degradation can become significant in circumstances with large RPD values and with low signal-to-noise ratio (SNR) values. Fig. 1 illustrates that the performance degradation can be up to 48% of the uplink performance as a result of RPD.

[0033] Embodiments of the present invention provide solutions to mitigate the impact of RPD on transmissions, such as UL SU-MIMO transmissions.

[0034] Usually, the transmission (TX) phase will shift when there is change in transmission power due to a non-linearity of RF circuits. The TX phase changes of single TX antenna will generally have no impact on performance because a reference signal (RS) is used to estimate the channel that includes TX phase shifting. For UL SU-MIMO, the phase changes of each TX antenna will contribute different "relative phase" when there is a TX power change. This "relative phase" change is called relative phase discontinuity (RPD) in 3GPP.

[0035] UL SU-MIMO relies on sounding reference signal (SRS) measurement to select the precoding matrix in closed-loop MIMO schemes. The SRS measurement shall determine the precoding matrix that will be used in the subsequent PUSCH transmission. However, due to the RPD, the relative phase at SRS will be different from that at PUSCH. If the RPD is significant enough, the precoding matrix for PUSCH will not match an optimal matrix, as found from SRS, which will degrade UL SU-MIMO performance.

[0036] Even though the RPD problem was first identified in the UL MIMO transmissions, similar problems can also exist in peer-to-peer communications such as Device-To-Device (D2D) communications in LTE or other communication systems. If multiple power amplifier stages are used at a base station, a similar problem also occurs in the downlink transmission. The embodiments of the present invention are applicable to any of the above scenarios. Although some embodiments of the present invention are explained in the context of UL transmission, such explanation is not intended to limit the embodiments of the present invention to only UL transmission in a cellular network.

[0037] According to the previous approaches, in 3GPP RAN4, there were efforts to specify UE RPD requirements. The new UE RPD requirements were specified to minimize the RPD so that there would be minimum UL SU- MIMO performance impact. However, these efforts were not successful since legacy UEs would not be able to support the previous approaches.

[0038] One embodiment of the present invention for mitigating the impact of RPD can be eNB-based. Another embodiment for mitigating the impact of RPD can be UE-based. Embodiments of the present invention can be implemented either at the base station / eNB or at the UE.

With respect to embodiments of the present invention that are eNB-based, certain embodiments include two operations at the eNB. A first operation at the eNB can be a detection of an RPD profile of a UE, which is defined as a set of UE transmission power-amplifier (TX PA) stages and the related ramping-up/down switching points. The RPD profile can either be signaled by a UE to the eNB, or be estimated by the eNB using historical Random-Access- Channel/Sounding- eference-Signal/Physical-UplirLk-Shared-Ch

(RACH/SRS/PUSCH) transmissions for a specific UE. A second operation at the eNB can be the performing of an eNB-scheduling scheme that reduces and/or minimizes RPD impact on uplink multiple-input-multiple-output (UL- MIMO) transmissions. In applying the eNB-scheduling scheme, the eNB can predict whether there is a power-amplifier (PA) mode-switching event for a PUSCH transmission based on the detected RPD profile. When there is a prediction of a PA mode- switching event, the eNB may either avoid scheduling UE power for mode- switching, or can use a RPD model with mode-switching prediction to select a precoding matrix for UL-MIMO. The purpose in scheduling UE power or selecting a precoding matrix is to ensure good UL-MIMO performance for the UE.

[0039] With respect to embodiments of the present invention that are UE- based, a method based on UE adjustment is also possible. In this method, the UE determines that a change in its transmission power will generally lead to inaccuracies/performance-degradation to a transmission due to RPD, and the UE can adjust its transmission signal or power accordingly. Embodiments of the present invention can be transparent to the eNB and can be done via implementation by UE vendors.

[0040] With regard to the eNB-based solution, as described above, one embodiment can acquire an RPD profile of a UE. When detecting the RPD profile of the UE, the eNB can acquire knowledge of the RPD profile. The RPD profile can include the number of UE transmission power-amplifier (TX PA) stages, information relating to mode- switching points in dBm, and a phase discontinuity distribution when PA mode- switching happens. There are two approaches for RPD profile detection.

[0041] In a first approach for detecting the RPD profile, the UE can signal its RPD profile to the UE's serving cell (e.g., an eNB). As such, the eNB can receive the RPD profile from the UE. This step may require changes in signaling standards to accommodate the signaling scheme.

[0042] In a second approach for detecting the RPD profile, the eNB estimates the RPD profile for the UE through historical power measurements of RACH/SRS/PUSCH channels. Further, these two approaches can be combined. In other words, the UE may signal some RPD parameters, and the eNB can use these parameters to estimate other RPD parameters.

[0043] In LTE Release 10, an aperiodic SRS was introduced. According to Technical Specification 36.213, the eNB can trigger an aperiodic SRS at different power levels to probe the RPD profile. By triggering the aperiodic SRS at different power levels, a table of the phase changes can be built.

[0044] Specifically, the probing process can fill out the fields of a table of phase changes, similar to the exemplary table as shown in Fig. 2, by measuring phase changes for a certain UE.

[0045] A UE's power amplifier may have some built-in hysteresis to prevent frequent switching between power stages from taking place. Consequently, the probing can include some "zigzag" in the different power levels to reveal any hysteresis, which is subsequently used in the PUSCH schedule.

[0046] In one example, because it typically takes approximately 20 s for an output signal to settle to a desired level as a result of error-vector-magnitude (EVM) and adjacent channel leakage, if the transmission power level change (during the probing process) happens back-to-back (e.g., if the transmission power levels are as follows, in subframe n, TX at 5 dBm, in subframe n+1, TX at 15 dBm), the power stage is not changed to an optimal operational stage. In contrast, if the transmission power level changes after a longer time span (e.g., if the transmission power levels are as follows, in subframe n, TX at 5 dBm, in subframe n+4, TX at 15 dBm, and there is no uplink transmission in between), then a gain stage can be freely changed. In that case, it may be necessary to build two tables like the table illustrated in Fig. 2. One table can correspond to back-to-back TX power changes, and another table can correspond to TX power changes that occur well-separated in time.

[0047] Release 10 specification (TS 36.213, V10) addresses sounding reference signal (SRS) power control as follows:

"The setting of the UE Transmit power i¾_RS for the Sounding Reference Symbol transmitted on subframe i for serving cell c is defined by

¾S,c (0 = ^min { -PcMA ,c ( > -%S_OFFSET,c (^m) + ¹⁰ lo lO (^MSRS,c ) + ¾_PUSCH,c ^') + «c ^') ^"

[dBm]

where

• CMAX, ( is the configured UE transmit power defined in [6] in subframe i for serving cell c .

• ^PSRS OFFSET^ is ^a 4-bit parameter semi-statically configured by higher layers for m=0 and m=l for serving cell c . For SRS transmission given trigger type 0 then m=0 and for SRS transmission given trigger type 1 then m=l . For K_s = 1.25 , i¾_RS OFFSET,^) has ldB step size in the range [-3,

12] dB. Fori^ = o , ¾s 0FFSET,c (^?w) has 1.5 dB step size in the range [-10.5,

12] dB.

• ^MSRS, is the bandwidth of the SRS transmission in subframe i for serving cell c expressed in number of resource blocks.

• f_c i) is the current PUSCH power control adjustment state for serving cell c , see Section 5.1.1.1.

• ^po pusc_H,c(y) ^and ^ac (J) ^are parameters as defined in Section 5.1.1.1, where j = 1."

[0048] The SRS power can be adjusted by a number of physical resource blocks (PRBs) assigned for PUSCH transmission and/or the PUSCH power control. In embodiments of the present invention, either or both can be used to adjust the SRS TX power. As the phase change table(s) that were built (as shown in Fig. 2) are used for PUSCH pre-coding matrix indicator/modulation- and-coding-scheme (PMI/MCS) level selection, any error in the table can lead to degraded throughput. As such, it can be important for the eNB to know that the UE is actually transmitting SRS while the eNB is conducting SRS measurement.

[0049] The eNB may need: (1) the physical-downlink-control- channel/enhanced-physical-downlink-control-channel (PDCCH/ePDCCH) format for uplink grant to be chosen conservatively to ensure UE reception, and/or (2) a large margin that is left in the PUSCH transmission accompanying SRS. With this large margin, a successful reception at eNB is generally guaranteed, and a cyclic-redundancy check (CRC) on the PUSCH can generally assure the eNB that the UE receives the uplink grant successfully.

[0050] A CRC check can give the eNB the assurance that the UE receives the uplink grant successfully. As such, regular PUSCHs without much margin can also be used. The probe process can take more time. Also when a phase change table for the back-to-back case is being built, it can be important to ensure that two downlink-control-information (DCIs) for uplink grant are received by the UE.

[0051] With regard to the eNB-based solution, as described above, another embodiment can minimize RPD impact. During PUSCH scheduling, the requested UE transmit power level, MCS level, and PMI can be jointly selected.

[0052] There are several methods to account for RPD in the eNB scheduler, and proper pre-coding matrix indicators (PMI) and modulation-and-coding- scheme (MCS) levels are selected at a transmission power level.

[0053] In one method to account for RPD in the eNB scheduler, from the phase difference transition table, the phase change from SRS transmitted at one level to PUSCH transmission at another level can be projected, assuming that the phase change can be approximated in a piece-wise way. A fixed phase change can be assumed from one power level to multiple power levels. With the channel response between the eNB and the UE obtained from SRS measurement, the channel response between eNB and UE at a projected PUSCH (at a certain TX power level) can be deduced, which can result in a scheme where multiple PMI and MCS level selections can be conducted at multiple projected transmission power hypotheses. As such, instead of determining one set {PMI, MCS level} at one power level, multiple sets of {PMI, MCS level} can be calculated after SRS measurement.

[0054] Otherwise, if multiple sets are not calculated, then a need may exist to somehow track the channel response over a long period of time, which may be undesirable in eNB implementation. In contrast, in embodiments of the present invention, the right set of {PMI, MCS level} can generally be used at the desired power level.

[0055] In a second method to account for RPD in the eNB scheduler, with the knowledge of a RPD profile, the eNB can schedule the UE to minimize RPD impact for UL-MIMO. Usually, an eNB will schedule a precoding matrix for UL-MIMO transmission based on SRS measurement. With the knowledge of the RPD profile, the eNB can predict the probability of UE PA mode- switching with a given power change, when UE is scheduling the UL-MIMO transmission precoding matrix. When the mode-switching probability is low (or zero), the scheduling will not be affected by the RPD profile. When the mode-switching probability is high, the eNB may select an alternative precoding matrix or power to minimize the impact to UL-MIMO performance.

[0056] In a third method to account for RPD in the eNB scheduler, the eNB may adjust the assigned MCS level for the PUSCH transmission to prevent the subframe from being received in error. In an unloaded system, the eNB may attempt to assign a transport block size (TBS) but at a lower MCS level using more resource blocks (RBs). This effectively maintains the same throughput by the UE at the cost of higher total transmission power by the UE.

[0057] In a fourth method to account for RPD in the eNB scheduler, the method does not require knowledge of the RPD profile but uses a power difference between SRS and PUSCH transmission to estimate a severity of the RPD and to accordingly compensate for this difference.

[0058] From RAN4 analysis, it can be shown that relative phase difference is generally most severe between PA switching points. If the switching points are known (for example, via constructing the profile as in the first aforementioned method), then compensation can be made when the SRS and PUSCH power crosses the switching point. If the switching points are not known, however, then the probability of PA-mode switching can be approximated by the power difference between SRS and PUSCH, and the minimum of the two power levels. The minimum power level can matter because PA mode switching is generally done at moderate to high power levels (e.g., at 0 or 15 dBm) and thus generally does not affect transmission in the lower power range.

[0059] A step of the fourth method (to account for RPD in the eNB scheduler) can include the estimation of a PA switching point probability using P_Tx_;Srs, PTx,_Pusch, and MrN(P-rx,srs, PTx,_Pusch)- The mapping function between these parameters can be determined from, e.g., RAN4 RPD models, manufacturer specifications, statistical models, or historical profiles.

[0060] Based on the PA switching point probability, the eNB may select an alternative precoding matrix or power to minimize the impact to UL-MIMO performance. Alternatively, the eNB may adjust the assigned MCS level for the PUSCH transmission to prevent the subframe from being received in error. In a low-loaded system, the eNB may attempt to assign the same TBS, but at a lower MCS level using more RBs. This effectively maintains the same throughput by the UE at the cost of higher total transmission power by the UE.

[0061] Next, in contrast with the above-described eNB-based solution for mitigating RPD impact, certain embodiments of the present invention can be directed to UE-based solutions for mitigating RPD impact. In one embodiment of a UE-based solution for mitigating RPD impact, it can be assumed that the UE knows the PA switching points, as this information can be available as part of the UE's design. The UE can then make adjustments to the transmission signal if the S S and PUSCH power crosses a switching point. If the UE can also determine the magnitude of the RPD in degrees, the UE can also use that information to determine whether an adjustment is needed (e.g., the UE can make adjustment only if the RPD is greater than a threshold).

[0062] One type of adjustment to the transmission signal is power adjustment. Although the UE may observe the power control setting as dictated by the eNB, the UE has some tolerance in its transmission power as specified by RAN4. This tolerance, for example, may be ±2.5 dB of the requested power, with an additional ±2.0 dB relaxation possible in extreme conditions. Thus, if the UE is still within the tolerance limit, it may adjust its transmission power to remain within the same PA switching point between SRS and PUSCH transmission. For example, if the PA switching point is 5.5 dB, the SRS transmission power is 4 dB, and the PUSCH transmission power is 6 dB, the UE may lower its PUSCH transmission power to 5 dB in order to not introduce RPD in the PUSCH transmission.

[0063] Another type of adjustment to the transmission signal is performing PMI override (i.e., selecting a PMI that may be different from the PMI selected by the eNB). The UE may keep recent statistics of assigned PMIs and can use a fallback mode when faced with a large RPD. Thus, when the UE expects that a large RPD will make PMI estimation by the eNB inaccurate, the UE can select a preferred PMI based on historical PMI assignment. In another embodiment, the UE may also keep statistics of assigned PMIs for different PA stages, and can select the preferred PMI based on the PA stage for PUSCH.

[0064] Another type of adjustment to the transmission signal is pre-distortion adjustment. If the RPD is known (e.g., through profiling by the UE manufacturer) or can be characterized, then a simple pre-distortion adjustment can be built. In this case, the transmission signal is pre-distorted by the expected RPD. This will correct the phase discontinuity so that the problem of PMI mismatched on the transmission signal is minimized.

[0065] Fig. 3 illustrates a flowchart of a method in accordance with an embodiment of the invention. The method illustrated in Fig. 3 includes, at 300, determining a relative-phase-discontinuity profile of a user equipment. The method also includes, at 310, performing a scheduling scheme based on the relative phase discontinuity of the user equipment.

[0066] Fig. 4 illustrates a flowchart of a method in accordance with an embodiment of the invention. The method illustrated in Fig. 4 includes, at 400, determining that a user equipment's transmitting will be impacted by relative -phase discontinuity. The method also includes, at 410, adjusting the user equipment's transmitting to reduce the impact to the transmission.

[0067] Fig. 5 illustrates an apparatus in accordance with an embodiment of the invention. In one embodiment, apparatus 10 can be a user equipment. In another embodiment, apparatus 10 can be a base station and/or an eNB. Apparatus 10 can include a processor 22 for processing information and executing instructions or operations. Processor 22 can be any type of general or specific purpose processor. While a single processor 22 is shown in Fig. 5, multiple processors can be utilized according to other embodiments. Processor 22 can also include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples.

[0068] Apparatus 10 can further include a memory 14, coupled to processor 22, for storing information and instructions that can be executed by processor 22. Memory 14 can be one or more memories and of any type suitable to the local application environment, and can be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and removable memory. For example, memory 14 include any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, or any other type of non-transitory machine or computer readable media. The instructions stored in memory 14 can include program instructions or computer program code that, when executed by processor 22, enable the apparatus 10 to perform tasks as described herein.

[0069] Apparatus 10 can also include one or more antennas (not shown) for transmitting and receiving signals and/or data to and from apparatus 10. Apparatus 10 can further include a transceiver 28 that modulates information on to a carrier waveform for transmission by the antenna(s) and demodulates information received via the antenna(s) for further processing by other elements of apparatus 10. In other embodiments, transceiver 28 can be capable of transmitting and receiving signals or data directly.

[0070] Processor 22 can perform functions associated with the operation of apparatus 10 including, without limitation, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus 10, including processes related to management of communication resources.

[0071] In an embodiment, memory 14 can store software modules that provide functionality when executed by processor 22. The modules can include an operating system 15 that provides operating system functionality for apparatus 10. The memory can also store one or more functional modules 18, such as an application or program, to provide additional functionality for apparatus 10. The components of apparatus 10 can be implemented in hardware, or as any suitable combination of hardware and software. [0072] Fig. 6 illustrates an apparatus in accordance with another embodiment. Apparatus 600 can be a base station and/or an evolved Node B (eNB), for example. Apparatus 600 can include a determining unit 601 that determines a relative -phase-discontinuity profile of a user equipment. Apparatus 600 can also include a performing unit 602 that performs a scheduling scheme based on the relative phase discontinuity of the user equipment.

[0073] Fig. 7 illustrates an apparatus in accordance with another embodiment. Apparatus 700 can be a user equipment, for example. Apparatus 700 can include a determining unit 701 that determines that a user equipment's transmitting will be impacted by relative -phase discontinuity. Apparatus 700 can also include an adjusting unit 702 that adjusts the user equipment's transmitting to reduce the impact to the transmission.

[0074] The described features, advantages, and characteristics of the invention can be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the invention can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages can be recognized in certain embodiments that may not be present in all embodiments of the invention. One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although the invention has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention.

Claims

WE CLAIM:

1. A method, comprising:

determining a relative -phase-discontinuity profile of a user equipment; and

performing a scheduling scheme based on the relative phase discontinuity of the user equipment.

2. The method according to claim 1, wherein the determining comprises determining a profile that comprises a set of user-equipment transmission-power amplifier stages and related ramping-up/down switching points.

3. The method according to claim 1 or 2, wherein the determining comprises receiving, via signaling, the profile or estimating the profile using historical Random- Access-Channel/Sounding-Reference-Signal/Physical- Uplink- Shared-Channel transmissions for the user equipment.

4. The method according to any of claims 1-3, wherein the performing comprises predicting whether there is a power-amplifier mode-switching event.

5. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured, with the at least one processor, to cause the apparatus at least to

determine a relative-phase-discontinuity profile of a user equipment; and

perform a scheduling scheme based on the relative phase discontinuity of the user equipment.

6. The apparatus according to claim 5, wherein the determining comprises determining a profile that comprises a set of user-equipment transmission-power amplifier stages and related ramping-up/down switching points.

7. The apparatus according to claim 5 or 6, wherein the determining comprises receiving, via signaling, the profile or estimating the profile using historical Random- Access-Channel/Sounding-Reference-Signal/Physical- Uplink- Shared-Channel transmissions for the user equipment.

8. The apparatus according to any of claims 5-7, wherein the performing comprises predicting whether there is a power-amplifier mode- switching event.

9. A computer program product, embodied on a non-transitory computer readable medium, the computer program product configured to control a processor to perform a process, comprising:

determining a relative -phase-discontinuity profile of a user equipment; and

10. A method, comprising:

determining that a user equipment's transmitting will be impacted by relative -phase discontinuity; and

adjusting the user equipment's transmitting to reduce the impact to the transmission.

1 1. The method according to claim 10, wherein the determining comprises determining that a change in the user equipment's transmission power will cause the user equipment's transmitting to be impacted by the relative -phase discontinuity.

12. The method according to claim 10 or 11, wherein the adjusting the user equipment's transmitting comprises adjusting the user equipment's transmission power.

13. The method according to any of claims 10-12, wherein the adjusting the user equipment's transmitting comprises performing an override of a pre-coding matrix indicator.

14. The method according to any of claims 10-13, wherein the adjusting the user equipment's transmitting comprises performing pre- distortion adjustment.

15. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

determine that the apparatus' transmitting will be impacted by relative- phase discontinuity; and

adjust the apparatus' transmitting to reduce the impact to the transmission.

16. The apparatus according to claim 15, wherein the determining comprises determining that a change in the apparatus' transmission power will cause the apparatus' transmitting to be impacted by the relative -phase discontinuity.

17. The apparatus according to claim 15 or 16, wherein the adjusting the apparatus' transmitting comprises adjusting the apparatus' transmission power.

18. The apparatus according to any of claims 15-17, wherein the adjusting the apparatus' transmitting comprises performing an override of a pre-coding matrix indicator.

19. The apparatus according to any of claims 15-18, wherein the adjusting the apparatus' transmitting comprises performing pre-distortion adjustment.

20. A computer program product, embodied on a non-transitory computer readable medium, the computer program product configured to control a processor to perform a process, comprising: