Technical Field

The present disclosure relates to a wireless network such as, e.g., a cellular network and more specifically relates to concurrent digital post-distortion of multiple signals received in multiple frequency channels, respectively, at a network node of a wireless network.

Background

Radio frequency Power Amplifiers (PAs) are inherently nonlinear, especially when they are operating with high efficiency. Therefore, a PA that to some degree is efficient must be linearized to meet typical linearity requirements in cellular communications systems. The PA non-linearity may otherwise ruin the quality of the transmitted signal, i.e., result in an Error Vector Magnitude (EVM) that is above an acceptable level, and/or disturb communication in neighbor frequency channels, i.e., produce unacceptably high Adjacent Channel Leakage Ratio (ACLR). Typically, linearization of the PA is done using digital predistortion (DPD), which can compensate for both Amplitude Modulation to Amplitude Modulation (AM-AM) variation and Amplitude Modulation to Phase Modulation (AM-PM) variation.

However, DPD adds complexity and cost in both analog and digital hardware. DPD also consumes substantial power, thereby reducing the overall efficiency improvement achieved. If the output power of the PA is too low, it may even be beneficial not to use DPD at all because the overall efficiency may be better using a more linear but less efficient PA without DPD.

A so called "in-band DPD" operates only on the same frequency bandwidth, or channel, as that of the transmitted signal. An in-band DPD typically improves in- channel distortion (i.e., improves EVM), but has little effect on frequencies outside the channel (i.e., has little effect on ACLR). To significantly reduce ACLR, the DPD must operate with at least three times the bandwidth of the channel. The linearization band then covers the transmitted channel and the two adjacent channels. This higher linearization bandwidth needed for such DPD needs to be handled by the analog transmitter, which is power consuming and adds complexity in the analog domain. In addition, the DPD also adds gain expansion to counteract gain compression of the PA, increasing the dynamic range of the PA input signal, which also adds complexity and power consumption.

Thus, there is a need for systems and methods that mitigate the need for the use of DPD for linearization.

Systems and methods related to concurrent Digital Post-Distortion (DPoD) of multiple signals are disclosed. In one embodiment, a method performed by a network node of a wireless network comprises receiving, within a timeslot, a multi-channel signal that comprises a plurality of signals from a respective plurality of User Equipments (UEs) on a respective plurality of frequency channels within a system bandwidth of the network node. The method further comprises separating the multi-channel signal into the plurality of signals from the respective plurality of UEs on the respective plurality of frequency channels within the system bandwidth of the network node. The method further comprises, for each signal of the plurality of signals, obtaining a DPoD characteristic to be applied to the signal, the DPoD characteristic to be applied to the signal being a compensation for both in-band distortion and adjacent band distortion and applying the DPoD characteristic to the signal to provide a post-distorted signal for a respective channel of the plurality of frequency channels. The method further comprises combining the post-distorted signals for the plurality of frequency channels to provide a compensated multi-channel signal. The DPoD of multiple signals in the same timeslot enables the UEs to transmit highly distorted signals, which in turn enable the complexity, cost, and power consumption of the UEs to be minimized.

In one embodiment, the adjacent band distortion compensated for by the DPoD characteristic comprises nonlinear inter-modulation distortion (IMD) products from the signal where the IMD products comprise at least a 3 ^rd order IMD (IM3) product.

In one embodiment, for each signal of the plurality of signals, obtaining the DPoD characteristic to be applied to the signal comprises, detecting a pilot signal within the signal for the respective channel, determining a non-linear characteristic of the signal based on a comparison of the detected pilot signal and a known pilot signal, and determining the DPoD characteristic to be applied to the signal based on the non-linear characteristic of the signal. In one embodiment, determining the DPoD characteristic to be applied to the signal based on the non-linear characteristic of the signal comprises determining the DPoD characteristic to be applied to the signal such that the DPoD characteristic compensates for the non-linear characteristic of the signal.

In one embodiment, the DPoD characteristic to be applied to the signal is a known DPoD characteristic to be applied to the signal, and obtaining the DPoD characteristic to be applied to the signal comprises obtaining the known DPoD characteristic to be applied to the signal from either the respective UE, another network node, or an associated storage device.

In one embodiment, the method further comprises, for each signal of the plurality of signals, applying automatic gain control for the signal received for the respective channel prior to applying the DPoD characteristic to the signal. In one embodiment, the method further comprises, for each signal of the plurality of signals, applying inverse automatic gain control for the signal received for the respective channel after applying the DPoD characteristic to the signal and before combining the post-distorted signals for the plurality of frequency channels.

In one embodiment, the timeslot is a slot or mini-slot or a defined number of Orthogonal Frequency Division Multiplexing (OFDM) symbols. In one embodiment, each channel of the plurality of frequency channels is a narrowband channel. In one embodiment, the narrowband channel has a bandwidth equal to or less than 200 kilohertz.

In one embodiment, the timeslot is a Third Generation Partnership Project (3GPP) Narrowband Internet of Things (NB-IoT) slot, and each of the plurality of signals is a NB-IoT signal.

Corresponding embodiments of a network node are also disclosed. In one embodiment, a network node of a wireless network is adapted to receive, within a timeslot, a multi-channel signal that comprises a plurality of signals from a respective plurality of UEs on a respective plurality of frequency channels within a system bandwidth of the network node and separate the multi-channel signal into the plurality of signals from the respective plurality of UEs on the respective plurality of frequency channels within the system bandwidth of the network node. The network node is further adapted to, for each signal of the plurality of signals, obtain a DPoD characteristic to be applied to the signal, the DPoD characteristic to be applied to the signal being a compensation for both in-band distortion and adjacent band distortion, apply the DPoD characteristic to the signal to provide a post-distorted signal for a respective channel of the plurality of frequency channels. The network node is further adapted to combine the post-distorted signals for the plurality of frequency channels to provide a compensated multi-channel signal.

In another embodiment, a network node of a wireless network comprises first circuitry configured to receive, within a timeslot, a multi-channel signal that comprises a plurality of signals from a respective plurality of UEs on a respective plurality of frequency channels within a system bandwidth of the network node and second circuitry configured to separate the multi-channel signal into the plurality of signals from the respective plurality of UEs on the respective plurality of frequency channels within the system bandwidth of the network node. The network node further comprises third circuitry configured to, for each signal of the plurality of signals, obtain a DPoD characteristic to be applied to the signal, the DPoD characteristic to be applied to the signal being a compensation for both in-band distortion and adjacent band distortion, and apply the DPoD characteristic to the signal to provide a post-distorted signal for a respective channel of the plurality of frequency channels. The network node further comprises fourth circuitry configured to combine the post-distorted signals for the plurality of frequency channels to provide a compensated multi-channel signal.

Brief of the

The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

Figure 1 illustrates a wireless network in which multiple User Equipments (UEs) are scheduled for simultaneous transmissions in respective (e.g., adjacent) frequency channels within a timeslot in accordance with one embodiment of the present disclosure;

Figure 2A illustrates a network node that performs Digital Post-Distortion (DPoD) on multiple receive signals received from the multiple UEs on the respective frequency channels during a timeslot in accordance with one embodiment of the present disclosure;

Figure 2B illustrates a network node that performs DPoD on multiple receive signals received from the multiple UEs on the respective frequency channels during a timeslot in accordance with one embodiment of the present disclosure; Figure 3 is a flow chart that illustrates the operation of the network node of Figure 2A in accordance with one embodiment of the present disclosure;

Figure 4 illustrate details of step 304-i of Figure 3 in more detail in accordance with one embodiment of the present disclosure;

Figure 5 illustrate details of step 304-i of Figure 3 in more detail in accordance with another embodiment of the present disclosure; and

Figure 6 illustrates the operation of the network node and the UEs in accordance with one embodiment of the present disclosure in which the network node activates the extreme power savings mode.

Detailed Description

The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure.

Radio Node: As used herein, a "radio node" is either a radio access node or a wireless communication device.

Network Node: As used herein, a "network node" can be any node of a network. One example of a network node is a "radio access node" or "radio network node" or "radio access network node", which can be any node in a Radio Access Network (RAN) of a cellular communications network that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high-power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), a relay node, a network node that implements part of the functionality of a base station or a network node that implements a gNB Distributed Unit (gNB-DU)) or a network node that implements part of the functionality of some other type of radio access node. Communication Device: As used herein, a "communication device" is any type of device that has access to an access network. Some examples of a communication device include, but are not limited to: mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or Personal Computer (PC). The communication device may be a portable, hand-held, computer-comprised, or vehiclemounted mobile device, enabled to communicate voice and/or data via a wireless or wireline connection.

Wireless Communication Device or User Equipment (UE): One type of communication device is a wireless communication device, which may be any type of wireless device that has access to (i.e., is served by) a wireless network (e.g., a cellular network). Some examples of a wireless communication device include, but are not limited to: a User Equipment device (UE) in a 3GPP network, a Machine Type Communication (MTC) device, an Internet of Things (loT) device, and a Narrowband Internet of Things (NB-IoT) device. Such wireless communication devices may be, or may be integrated into, a mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or PC. The wireless communication device may be a portable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data via a wireless connection.

Systems and methods are disclosed herein that eliminate or mitigate the need for linearization schemes, such as Digital Pre-Distortion (DPD), in User Equipments (UEs) in a wireless network such as, e.g., Narrowband Internet of Things (NB-IoT) UEs in a Third Generation Partnership (3GPP) network. Distortion is a deterministic process. This means that the original signal can be retrieved from a distorted signal if the nonlinearities of the transmitter are known to the receiver. In one embodiment, multiple UEs are scheduled for uplink transmission in respective (e.g., adjacent) frequency channels during a timeslot (e.g., slot, mini-slot, or number of Orthogonal Frequency Division Multiplexing (OFDM) symbols) and allowed to transmit highly distorted signals, which makes it possible for their respective Power Amplifiers (PAs) to operate with high efficiency without the need for a linearization scheme such as, e.g., DPD. In one embodiment, these highly distorted signals, or nonlinear transmissions, take place during a special scheduled timeslot, for instance a narrowband Internet of Things (NB loT) slot. During this slot, many devices can then transmit narrowband signals whose nonlinear IM3 and possibly IM5 products still fall within the scheduled frequency slot.

During the timeslot, a network node (e.g., a RAN node such as, e.g., a base station) receives a multi-channel signal that includes the scheduled uplink transmissions from the multiple UEs. The network node separates the multi-channel signal, e.g., via filtering, into multiple received signals for the respective frequency channels. For each received signal, the network node obtains a Digital Post-Distortion (DPoD) to be applied to the received signal for the respective frequency channel and applies the DPoD to the received signal for the respective channel to provide a post-distorted signal for the respective channel. The DPoD compensates for a non-linear characteristic of the received signal for the respective channel, where the non-linear characteristic includes Inter-Modulation Distortion (IMD) products including at least a 3 ^rd Order IMD (IM3) product of the received signal for the respective channel. It should be noted that the post-distorted signal contains signal energy in adjacent channels such that, when the post-distorted signals for the multiple channels are combined, the combined effect of all of the signals is such that effects on adjacent channels are cancelled. Note that while the post-distortion reduces the distortion in-channel in the filtered signal, it increases distortion in adjacent channels. It is not until the signals for the multiple channels are combined that this distortion becomes useful, then providing cancellation. In one embodiment, for each received signal, DPoD to be applied to the received signal is obtained by determining the non-linear characteristic of the received signal (e.g., based on a pilot or reference signal). In another embodiment, either the DPoD or the nonlinear characteristic of the received signal is obtained, e.g., from the respective UE, from another network node, or from an associated storage device (e.g., memory).

By allowing the UEs to transmit highly distorted signals, the complexity, cost, and power consumption of the UEs can be minimized. One way to achieve this is to remove the DPDs in the UEs. In addition, a relatively simple PA design, for instance implemented in a Complementary Metal Oxide Semiconductor (CMOS) process rather than in Gallium Arsenide (GaAs) process, may be used, where the PA operates more efficiently by being not backed off as far in its linear region. Such as PA design will reduce cost, complexity, and power consumption.

Relaxed Adjacent Channel Leakage Ratio (ACLR) requirements for some UEs will make new use cases possible that otherwise would be discarded due to cost and/or power consumption, effectively enabling a fast roll-out of the Internet of Things (loT) by moving cost, complexity, and power consumption from the UEs into the network node. The UEs can then have lower power consumption, thereby making batteries last longer or even enabling operation based solely on harvested energy.

The total occupied frequency spectrum is not significantly increased by the nonlinear transmissions since the distortion products (e.g., IM3) of the transmitter of one UE will fall on the frequency channel used by another UE, and that frequency can still be used for reception by the network node cleaning it up using DPoD.

Figure 1 illustrates a wireless network 100 (e.g., a cellular network such as, e.g., a 3GPP network such as, e.g., a 3GPP New Radio (NR) network) in which multiple UEs 102-1 to 102-N are scheduled for simultaneous transmissions in respective (e.g., adjacent) frequency channels within a timeslot in accordance with one embodiment of the present disclosure. A single arbitrary UE is denoted herein as "UE 102-i". The respective frequency channel is denoted herein as the i-th frequency channel or channel i. The UE 102-1 includes a combiner 104-i, filtering circuitry 106-i, a Digital to Analog Converter (DAC) 108-i, a PA 110-i, and an antenna 112-i, connected as shown. In operation, the combiner 104-i that combines a baseband signal to be transmitted and a pilot signal to provide a transmit signal to be transmitted by the UE 102-i. In one embodiment, the pilot signal contains symbols with all different amplitudes, which is beneficial to accurately estimate AM-AM and AM-PM distortion. To minimize the effect of channel filters, each symbol may be repeated a few consecutive times to provide more accurate results. The transmit signal is upconverted (not shown), filtered by the filtering circuitry 106-i, converted from analog to digital by the DAC 108-i, amplified by the PA 110-i, and then transmitted via the antenna 112-i. Note that the elements shown in Figure 1 for each of the UEs 102-1 through 102-N are only an example. As will be appreciated by one of skill in the art, additional and/or alternative elements may be included. For instance, one example alternative is that the transmit chain includes the combiner 104-i, followed by the DAC 108-i, followed by the low-pass filter 106-i, followed by an upconversion mixer (not shown), followed by the PA 110-i, followed by an RF filter (not shown), and then the antenna 112-i.

The UEs 102-1 through 102-N transmit their transmit signals in the same timeslot in respective frequency channels. Each UE 102-i transmits in a respective frequency channel (i.e., channel i). In one embodiment, the frequency channels are narrowband channels within a system bandwidth of the network node or cell on which the signals are transmitted. For example, the system bandwidth may be any of the possible 3GPP NR cell bandwidth. The narrowband channels may each have a bandwidth of, e.g., 200 kilohertz or less, in one embodiment. In one example embodiment, the narrowband channels may be, e.g., NB-IoT channels. The timeslot may be, e.g., a slot, a mini-slot, or a defined number of OFDM symbols. The UEs 102-1 through 102-N preferably do not use a linearization scheme such as, e.g., DPD when transmitting the transmit signals, and the PAs 110-1 through 110-N are preferably operated in a highly efficient mode (e.g., reduced backoff from linear mode) or have a highly efficient design, or are implemented in a low cost technology (e.g., CMOS rather than GaAs design). This results in the transmitted signals being highly distorted signals. While the highly distorted transmit signals are not ideal, the distortion is cancelled or mitigated at the receiver side (as described below), which in turn enables the use low cost transmitters at the UE-side, which is advantageous.

Figure 2A illustrates a network node 200 that performs DPoD on multiple receive signals received from the multiple UEs 102-1 through 102-N on the respective frequency channels during a timeslot in accordance with one embodiment of the present disclosure. As illustrated, the network node 200 includes an antenna 202, a Low-Noise Amplifier 204, downconversion circuitry 205 (e.g., frequency domain mixer(s)), filtering circuitry 206, and an Analog to Digital Converter (ADC) 207, connected as shown. The network node 200 also includes separate receiver chains for the N frequency channels, which are denoted as Channel 1 to Channel N, over which the network node 200 receives signals from the UEs 102-1 through 102-N in the timeslot. An arbitrary channel is referred to as "Channel i". In this embodiment, the receiver chain for each Channel i, the network node 200 includes a filtering circuitry 208-i, Automatic Gain Control (AGC) circuitry 209-i, a DPoD actuator 210-i, inverse AGC circuitry 211-i, Digital Downconversion (DDC) circuitry 212-i, a pilot detector 214-i, and a non-linear (NL) characteristic estimator 216-i (also referred to herein simply as a NL estimator 216-i), connected as shown. The network node 200 also includes a combiner 218 that combines post-distorted receive signals for the N frequency channels to provide a postdistorted multi-channel signal that may, e.g., be further processed (e.g., decoded) to recover data transmitted by the UEs 102-1 through 102-N. Note that, as will be appreciated by one of ordinary skill in the art, the network node 200 may include additional and/or alternative circuitry.

In operation, the signals transmitted by the UEs 102-1 through 102-N over the radio channel are received, at the antenna 202 of the network node 200, as a multichannel signal. The received multi-channel signal is amplified by the LNA 204 and converted from analog to digital by the ADC 207. The amplified, digitized multi-channel signal is then provided to the receiver chains for the N frequency channels. For each Channel i, the multi-channel signal is filtered by the respective filtering circuitry 208-i to provide a received signal for Channel i. The bandwidth of the filtering circuitry 208-i is preferably equal to than the bandwidth of the transmitted signal from the respective UE 102-i.

The filtered, received signal is processed by the AGC circuitry 209-i and then passed to the DDC circuitry 212-i to downconvert the filtered, received signal to baseband. When the DPoD has been tuned to a signal in Channel i, if then that signal level changes for instance due to the corresponding UE 102-i making a movement, the DPoD circuitry 210-i would, without the ACG circuitry 209-i, start to produce a larger or smaller amount of relative distortion. For instance, if the distortion level of the DPoD was first at -25 dB compared to the desired signal, after the movement it could be at - 20 dB or -30 dB. But the UE 102-i will still produce the same distortion at -25 dB. Then, there would be a mismatch between the actual distortion and the compensating DPoD, which would mitigate the effectiveness of the DPoD. To combat this, the changes in received signal level could be minimized by the AGC circuitry 209-i at each channel. Separate AGC circuitry 209-i at each channel is preferred since the UEs 102-1 through 102-N normally can move independently and also since fading is frequency dependent. Thus, in operation, the AGC circuitry 209-i operates to adjust the gain, or level, of the signal for Channel i such that the resulting received signal output by the AGC 209-i is at a power level that is consistent with the power level of the received signal at the time at which the DPoD applied by the DPoD circuitry 210-i was determined. The pilot detector 214-i processes the resulting baseband signal to detect the respective pilot signal. The NL estimator 216-i determines, or estimates, a non-linear characteristic of the received signal for Channel i based on the detected pilot signal as compared to the known pilot signal (e.g., based on a comparison of a portion of the baseband received signal that corresponds to the detected pilot signal and a known, baseband representation of the known pilot signal). In one embodiment, the NL estimator 216-i determines coefficients for a 3 ^rd order or higher complex polynomial that represents the non-linear characteristic (e.g., represents a NL characteristic that when applied to the known pilot signal results in the received/detected pilot signal). In another embodiment, the NL estimator 216-i populates an amplitude based Look Up Table (LUT) that maps amplitude and phase shift values for the received/detected pilot signal to the known pilot signal amplitude. Both amplitude and phase shift values can be stored in the LUT, to correct for both AM-AM and AM-PM distortion. The DPoD actuator 210-i then applies a DPoD characteristic to the received signal for Channel i to provide the post-distorted signal for Channel i. In one embodiment, the DPoD characteristic applied by the DPoD actuator 210-i is a function of the determined non-linear characteristic. For example, in one embodiment, the DPoD characteristic applied by the DPoD actuator 210-i is an inverse of the determined non-linear characteristic. It should be noted that the NL estimator 216-i may alternatively directly determine the DPoD characteristic to be applied by the DPoD actuator 210-i. For example, the NL estimator 216-i may alternatively determine coefficients of a 3 ^rd order or higher complex polynomial that represents the DPoD characteristic (e.g., represents a DPoD characteristic that when applied to the detected/ received pilot signal results in the known pilot signal). The inverse AGC circuitry 211-i applies an inverse of the automatic gain control applied by the AGC circuitry 209-i for Channel i to restore the original signal level. The resulting signals output for Channels 1 to N are combined by the combiner circuitry 218.

Figure 2B illustrates another embodiment of the network node 200. In this embodiment, rather than determining the DPoD characteristic to be applied for each channel, the DPoD characteristic (or alternatively the non-linear characteristic) for each channel is known. For each channel, the network node 200 obtains the DPoD characteristic for the channel (or alternatively the non-linear characteristic for the channel) from the respective UEs 102-1 through 102-N, from another network node, or from a storage device (e.g., memory). For example, the UEs 102-1 through 102-N may determine or otherwise known the non-linear characteristics of their respective PAs 110- 1 through 110-N and provide the known non-linear characteristics to the network node 200, where the DPoD actuators 210-1 through 210-N apply DPoD characteristics that are based on (e.g., an inverse of) of the respective non-linear characteristics.

Figure 3 is a flow chart that illustrates the operation of the network node 200 of Figure 2A in accordance with one embodiment of the present disclosure. Optional steps are represented by dashed lines/boxes. As illustrated, the network node 200 receives, within a single timeslot, a multi-channel signal that comprises signals from the respective UEs 102-1 through 102-N on the respective frequency channels within a system bandwidth of the network node 200 (step 300). In one embodiment, the timeslot is a slot or mini-slot or a defined number of OFDM symbols. In one embodiment, each of the frequency channels is a narrowband channel. In one embodiment, each narrowband channel has a bandwidth that is equal to or less than 200 kHz. In one embodiment, the timeslot is a NB-IoT timeslot, and each of the signals received from the UEs 102-1 through 102-N is a NB-IoT signal.

The network node 200 separates the multi-channel signal into signals for the N frequency channels, which are representative of the N signals received from the respective UEs 102-1 through 102-N on the respective frequency channels (step 302). For each Channel i, the network node 200 performs automatic gain control to the signal received for Channel i (step 303-i) and obtains a DPoD characteristic to be applied to the signal received in Channel i (step 304-i). The DPoD characteristic to be applied to the signal is a compensation both in-band distortion and adjacent channel distortion. In other words, the DPoD characteristic compensates for both in-band distortion and for nonlinear IMD products that fall within adjacent frequency channels (e.g., at least an IM3 product). The network node 200 applies the DPoD characteristic to the signal received in Channel i to provide a post-distorted signal for Channel i (step 306-i). The network node 200 applies an inverse gain control (i.e., the inverse of the automatic gain control applied to the signal in step 303-i) (step 306-i). This restores the signal to the original level, prior to combination in step 308. The network node 202 combines the post-distorted signals for the N adjacent frequency channels to provide a compensated (post-distorted) multi-channel signal (step 308). The network node 200 then performs multi-channel signal reception, e.g., to recover data transmitted by the UEs 102-1 through 102-N (step 310).

As illustrated in Figure 4, in one embodiment, in order to obtain the DPoD characteristic for the signal received in Channel i in step 304-i of Figure 3, the network node 200 detects a pilot signal within the signal received for Channel i (step 400-i), determines a non-linear characteristic of the signal based on a comparison of the detected pilot signal and a known pilot signal (step 402-i), and determines the DPoD characteristic to be applied to the signal received in Channel i based on the non-linear characteristic of the signal (step 404-i). The pilot signal could be located at different time locations within the timeslot, e.g., at the beginning of the timeslot or some other time in the timeslot. Note that, if the pilot signal is not at the beginning of the timeslot, the DPoD could then be performed by postprocessing data samples stored in memory. In one embodiment, the DPoD characteristic to be applied to the signal is determined such that the DPoD characteristic compensates for the non-linear characteristic of the signal. For instance, for the signal received on Channel i (and thus for UE 102-i), a nonlinear DPoD polynomial is fitted to minimize the distortion of the pilot signal. The polynomial is then used to find the distortion not only in-band but also in adjacent channels. Thus DPoD polynomial is applied such that the estimated distortion is subtracted from the received signal. For the signal from the UE 102-i, both its own distortion in-channel and the distortion from adjunct frequency channels (once the combination in step 308 has been performed) are reduced by DPoD.

As illustrated in Figure 5, in another embodiment, the DPoD characteristic to be applied to the signal for Channel i is a known DPoD characteristic to be applied to the signal for Channel i, and the network node 200 obtains the DPoD characteristic to be applied to the signal for Channel i from either the respective UE 102-i, another network node, or an associated storage device (step 500-i).

In one embodiment, operation of the UEs 102-1 through 102-N to transmit the non-linearized signals may be a mode of operation (referred to herein as an "extreme power savings mode") that is activated (e.g., dynamically) by the network (e.g., by the network node 200). Figure 6 illustrates the operation of the network node 200 and the UEs 102-1 through 102-N in accordance with one embodiment of the present disclosure in which the network node 200 activates the extreme power savings mode. Optional steps are represented by dashed lines/boxes. As illustrated, the UEs 102-1 through 102-N may, in some embodiments, send capability information to the network node 200 that indicates that they are capable of operating in the extreme power savings mode (step 600). The network node 200 may signal, to the UEs 102-1 through 102-N, that they are to use the extreme power savings mode of operation (step 602). In addition, the network node 200 may signal, to the UEs 102-1 through 102-N, parameters or configurations related to the extreme power savings mode of operation (step 604). For example, the network node 200 may signal a configuration for one or more reference signals to be used in the extreme power savings mode of operation. For instance, the network node 200 may estimate modulation order and select reference signals appropriate for the estimated modulation order and configure the UEs 102-1 through 102-N accordingly. Alternatively, some or all of the configurations needed for the extreme power savings mode may be read from memory or determined based on known information, e.g., defined in a standard (e.g., a 3GPP technical specification(s)). In response, the UEs 102-1 through 102-N operate to transmit the non-linearized signals, as described above (step 606). The network node 200 receives a multi-channel signal including the signals from multiple UEs 102-1 through 102-N in the same timeslot and performs DPoD as described above, e.g., with respect to Figures 3 through 5 (step 608).

Alternatively, the UEs 102-1 through 102-N may request to use the extreme power savings mode of operation, either explicitly or implicitly (e.g., via use of a specific Random Access Channel (RACH) preamble or one of a defined set of RACH preambles that implicitly indicate that the UEs 102-1 through 102-N desire to use this mode of operation. In response to such as request, the network node 200 may provide an indication (e.g., in downlink control information (DCI) scheduling the uplink transmissions by the UEs 102-1 through 102-N) that the UEs 102-1 through 102-N are to use this mode of operation.

In another embodiment, the network node 200 may use an estimate of the Signal to Interference plus Noise Ratio (SINR) for the UE 102-i to, e.g., determine whether to instruct the UE 102-i to use the extreme power savings mode.

Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processors (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure.

While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.).

Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.