CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to the U.S. Prov. Pat. App. No. 62/234,636, filed September 29, 2016, which is hereby incorporated by reference as if fully set forth herein.

5 FIELD OF DISCLOSURE

The present disclosure relates generally to the field of wireless communications, and in particular to performing narrowband modulation.

BACKGROUND

In wireless communication systems, limiting the peak-to-average power ratio (PAPR) in 0 a wireless device during an uplink transmission is desirable since the power efficiency of a

power amplifier in a transmitter of the wireless device decreases with increasing PAPR.

Further, since a typical wireless device is battery operated, any increase in the power efficiency of the power amplifier results in longer battery life.

The Long Term Evolution (LTE) wireless communication system uses a Single Carrier, 5 Frequency Division Multiple Access (SC-FDMA) uplink scheme, which typically has a lower PAPR than other types of multiple access digital modulation schemes such as Orthogonal Frequency Division Multiple Access (OFDMA). The lower PAPR of SC-FDMA is inherently due to its single carrier structure. However, LTE transmitters tend to increase PAPR due to the use of pulse shaping filters in the LTE transmitter. The pulse shaping filters are used to reduce out- 0 of-band emissions at the expense of causing an increase in PAPR.

Accordingly, there is a need for improved techniques for improving a PAPR of a transmitter in a communication system. In addition, other desirable features and characteristics of the present disclosure will become apparent from the subsequent detailed description and embodiments, taken in conjunction with the accompanying figures and the foregoing technical 5 field and background.

The Background section of this document is provided to place embodiments of the present disclosure in technological and operational context, to assist those of skill in the art in understanding their scope and utility. Unless explicitly identified as such, no statement herein is admitted to be prior art merely by its inclusion in the Background section.

0 SUMMARY

The following presents a simplified summary of the disclosure in order to provide a basic understanding to those of skill in the art. This summary is not an extensive overview of the disclosure and is not intended to identify key/critical elements of embodiments of the disclosure or to delineate the scope of the disclosure. The sole purpose of this summary is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

Briefly described, embodiment of the present disclosure relate to performing narrowband modulation. According to one aspect, a method is performed by a wireless device for controlling a peak-to-average power ratio (PAPR) of a signal in a communication system. The method may include modulating a plurality of symbols using one of π/2-BPSK modulation and π/4-QPSK modulation to obtain modulated signals. Further, the method may include windowing and overlapping the modulated signals to obtain windowed and overlapped signals. Also, the method may include filtering the windowed and overlapped signals using a pulse shaping filter to obtain filtered signals.

According to another aspect, a wireless device for controlling a PAPR of a signal in a communication system may include a modulator, a window and overlap circuit, and a filter. The modulator may be configured to modulate a plurality of symbols using one of π/2-BPSK modulation and π/4-QPSK modulation to obtain modulated signals. The window and overlap circuit may be configured to window and overlap the modulated signals to obtain windowed and overlapped signals. The filter may be configured to filter the windowed and overlapped signals using a pulse shaping filter to obtain filtered signals.

According to another aspect, the PAPR of the filtered signals may be no more than about 0.5 dB.

According to another aspect, the PAPR of the filtered signals may be no more than about 0.1 dB.

According to another aspect, the PAPR of the filtered signals may be no more than about 0.04 dB.

According to another aspect, about ninety-five percent (95%) of the energy of the pulse shaping filter is in less than half of a length in time of the pulse shaping filter.

According to another aspect, the length in time of the pulse shaping filter may be in a range from about eight microseconds (8 usee.) to about eleven microseconds (1 1 usee.) and about ninety-five percent (95%) of an energy of the pulse shaping filter may be in a range from about three microseconds (3 usee.) to about four microseconds (4 usee). Further, the sampling rate may be about 1.28 Msps.

According to another aspect, the method may include inserting a cyclic prefix in the plurality of symbols. Further, the length in time of the pulse shaping filter may be less than the length in time of the cyclic prefix.

According to another aspect, the pulse shaping filter may have a substantially flat passband.

According to another aspect, the pulse shaping filter may be a Gaussian filter.

According to another aspect, each coefficient of the pulse shaping filter may be at least zero. According to another aspect, each symbol may be an OFDM symbol.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of this disclosure are shown. However, this disclosure should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like numbers refer to like elements throughout.

FIG. 1 illustrates one embodiment of the time-domain impulse response of a first pulse shaping filter in accordance with various aspects described herein.

FIG. 2 illustrates one embodiment of the time-domain impulse response of a second pulse shaping filter in accordance with various aspects described herein.

FIG. 3 provides a chart of a complementary cumulative distribution function (CDF) of PAPR for TT/2-BPSK modulation with the first pulse shaping filter and without windowing or overlapping in accordance with various aspects described herein.

FIG. 4 provides a chart of a chart of complementary CDF of PAPR for π/2-BPSK modulation with the first pulse shaping filter and with windowing and 4-sample overlapping in accordance with various aspects described herein.

FIG. 5 provides a chart of a complementary CDF of PAPR for π/2-BPSK modulation with the second pulse shaping filter and without windowing or overlapping in accordance with various aspects described herein.

FIG. 6 provides a chart of a complementary CDF of PAPR for π/2-BPSK modulation with the second pulse shaping filter and with windowing and 2-sample overlapping in accordance with various aspects described herein.

FIG. 7 provides a chart of instantaneous relative power of a signal modulated with ττ/2-

BPSK modulation and filtered by the second pulse shaping filter in accordance with various aspects described herein.

FIG. 8 provides a table summarizing PAPR characteristics using the first pulse shaping filter in accordance with various techniques described herein.

FIG. 9 provides a table summarizing PAPR characteristics using the second pulse shaping filter in accordance with various techniques described herein.

FIG. 10 is a flowchart of one embodiment of a method performed by a wireless device for controlling PAPR of a signal in a communication system in accordance with various techniques described herein.

FIG. 11 illustrates one embodiment of a wireless device for controlling PAPR of a signal in a communication system in accordance with various techniques described herein.

FIG. 12 illustrates one embodiment of a wireless device in accordance with various aspects described herein. FIG. 13 illustrates one embodiment of a wireless device for controlling PAPR of a signal in a communication system in accordance with various techniques described herein.

FIG. 14 illustrates one embodiment of a pulse shaping filter in accordance with various aspects described herein.

DETAILED DESCRIPTION

For simplicity and illustrative purposes, the present disclosure is described by referring mainly to an exemplary embodiment thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be readily apparent to one of ordinary skill in the art that the present disclosure may be practiced without limitation to these specific details. In this description, well-known methods and structures have not been described in detail so as not to unnecessarily obscure the present disclosure.

This disclosure includes describing Narrow-Band Long Term Evolution (NB-LTE) uplink (UL) modulation. NB-LTE UL modulation is based on single-carrier, frequency-division multiple- access (SC-FDMA), which is the same as LTE uplink. This technique allows for flexible UE bandwidth allocation including single tone transmission as a special case of SC-FDMA.

The NB-LTE uplink contains three basic channels including M-PRACH, M-PUCCH, and M-PUSCH. M-PUCCH may not be necessary since its function may be integrated to M-PRACH and M-PUSCH.

NB-LTE uplink modulation may use, for instance, π/2-BPSK, π/4-QPSK, or the like. For π/2-BPSK modulation, the constellation is rotated ττ/2 radians every symbol. For π/4-QPSK modulation, the constellation is rotated ττ/4 radians every symbol. This rotation provides smoother transitions between constellation points, reducing the peak to average power ratio (PAPR). These modulation options may be used for M-PUSCH and M-PUCCH, resulting in reduced PAPR for these channels.

The amplitude variations of a transmission may depend on a pulse shaping filter, which may also be referred to as a transmit filter. FIG. 1 illustrates the time-domain impulse response of a first pulse shaping filter 100 in accordance with various aspects described herein. The first pulse shaping filter 100 may be at least a 12-tap finite impulse response (FIR) filter that is characterized by a substantially flat passband. The first pulse shaping filter 100 may be similar to the filter described by downlink (DL) transmit (Tx) contribution. As shown in FIG. 1 , the time- domain impulse response of the first pulse shaping filter 100 may have the following filter coefficients:

ao is equivalent to about -0.0632,

ai is equivalent to about -0.0610,

a _∑ is equivalent to about 0.0240,

a3 is equivalent to about 0.1958,

a4 is equivalent to about 0.4008, as is equivalent to about 0.5411 ,

ae is equivalent to about 0.5411 ,

a7 is equivalent to about 0.4008,

as is equivalent to about 0.1958,

ag is equivalent to about 0.0240,

aw is equivalent to about -0.0610, and

an is equivalent to about -0.0632.

These filter coefficients are normalized for unity gain. Further, these filter coefficients may be quantized or otherwise modified such as for a particular filter implementation (e.g., lattice form).

FIG. 2 illustrates the time-domain impulse response of a second pulse shaping filter 200 in accordance with various aspects described herein. The second pulse shaping filter 200 may be at least an 8-tap Gaussian FIR filter. The time-domain impulse response of the second pulse shaping filter 200 may have the following filter coefficients:

ao is equivalent to about 0.0348,

ai is equivalent to about 0.1426,

a _∑ is equivalent to about 0.3663,

a3 is equivalent to about 0.5867,

a4 is equivalent to about 0.5867,

as is equivalent to about 0.3663,

ae is equivalent to about 0.1426, and

a7 is equivalent to about 0.0348.

These filter coefficients are normalized for unity gain. Also, these filter coefficients may be quantized or otherwise modified such as for a particular filter implementation.

In one embodiment, a wireless device may generate symbols of length one hundred and twenty-eight (128) samples, before concatenating them with a cyclic prefix (CP) of nine (9) samples (10 samples for every seventh symbol). A subcarrier spacing may be about 2.5 kHz and may correspond to transmitting these samples at about three hundred and twenty kilo- samples per second (320 ksps). For transmit filtering, this signal may be up-sampled and input to a pulse shaping filter.

The wireless device may operate directly at about 1.28 million samples per second (Msps), which may be a sampling rate of a pulse shaping filter. Further, each orthogonal frequency division multiplexed (OFDM) symbol may be five hundred and twelve (512) samples long, which may exclude the CP. At this sampling rate, a length of the first pulse shaping filter 100 may be about eleven microseconds (11 usee.) and a length of the second pulse shaping filter 200 may be about eight microseconds (8 usee). Further, for each of these filters, about 95% of the energy may be contained within about three microseconds (3 usee.) to about four microseconds (4 usee). For NB-LTE UL modulation with 2.5 kHz subcarrier spacing, the CP length may be about twenty-eight microseconds (28 usee.) to about thirty-one microseconds (31 usee.) long, and each of the pulse shaping filters may be well within the CP length.

For determining PAPR, random symbols in each of the two constellation alphabets have been generated and mapped to one subcarrier, and the instantaneous power compared to the average power of the transmitted samples has been measured. FIG. 3 provides a chart 300 of a complementary cumulative distribution function (CDF) of PAPR for Tr/2-BPSK modulation with the first pulse shaping filter 100 and without windowing or overlapping in accordance with various aspects described herein. In FIG. 3, the complementary CDF of the instantaneous PAPR is shown for seventy-two (72) different subcarriers that are available in NB-LTE uplink when transmitted using the first pulse shaping filter 100. FIG. 3 shows that π/2-BPSK modulation with the first pulse shaping filter 100 has about 1.0 dB PAPR at the worst subcarrier(s).

FIG. 4 provides a chart 400 of a complementary CDF of PAPR for π/2-BPSK modulation with the first pulse shaping filter 100 and with windowing and 4-sample overlapping in accordance with various aspects described herein. By using a windowing and overlapping method such as described by GP-150048, "Peak- to-Average Power Ratio and Power Spectral Density of Tone-Phase-Shift Keying", source Qualcomm Incorporated, 3GPP TSG GERAN #65, Shanghai, China, 9 - 13 March 2015, with an overlap of four (4) samples (at 1.28 Msps), the PAPR reduces to 0.5 dB. The same 0.5 dB PAPR is achieved also with π/4-QPSK modulation.

FIG. 5 provides a chart 500 of a complementary CDF of PAPR for π/2-BPSK modulation with the second pulse shaping filter 200 and without windowing or overlapping in accordance with various aspects described herein. In FIG. 5, if the second pulse shaping filter 200 without windowing or overlapping is used, the PAPR is about 1.1 dB for Tr/2-BPSK modulation.

FIG. 6 provides a chart 600 of a complementary CDF of PAPR for π/2-BPSK modulation with the second pulse shaping filter 200 and with windowing and 2-sample overlapping in accordance with various aspects described herein. In FIG. 6, if the second pulse shaping filter 200 with windowing and two (2) sample overlapping is used, the PAPR reduces to about 0.1 dB. If the second pulse shaping filter 200 with windowing and four (4) sample overlapping is used, the PAPR reduces to about 0.04 dB. Further, about the same PAPR is achieved using ττ/4- QPSK modulation.

FIG. 7 provides a chart 700 of instantaneous relative power of a signal modulated with π/2-BPSK modulation and filtered by the second pulse shaping filter in accordance with various aspects described herein. Most of the time, the signal amplitude is constant, but at the symbol boundaries, at the cyclic prefix, the amplitude decreases during a few samples. However, the decrease may be anticipated since it may be determined by the OFDM symbol rate. Both the average and the maximum amplitudes are close to one (1), which provides a low PAPR.

FIG. 8 provides a table 800 summarizing PAPR characteristics using the first pulse shaping filter 100 of FIG. 1 in accordance with various techniques described herein. FIG. 9 provides a table 900 summarizing PAPR characteristics using the second pulse shaping filter 200 of FIG. 2 in accordance with various techniques described herein.

FIG. 10 is a flowchart of one embodiment of a method 1000 performed by a wireless device for controlling PAPR of a signal in a communication system in accordance with various techniques described herein. In FIG. 10, the method 1000 may start, for instance, at block 1001 where it may include modulating a plurality of symbols to obtain modulated signals. At block 1003, the method 1000 may include windowing and overlapping the modulated signals to obtain windowed and overlapped signals. At block 1005, the method may include filtering the windowed and overlapped signals using a pulse shaping filter to obtain filtered signals. The PAPR of the filtered signals may be no more than 0.5 dB.

FIG. 11 illustrates one embodiment of a wireless device 1100 for controlling PAPR of a signal in a communication system in accordance with various techniques described herein. The wireless device 1100 may include a modulator 1101 , a CP insertion circuit 1109, a window and overlap circuit 1105, an interpolation circuit 1111 , a pulse shaping filter 1113, the like, or any combination thereof. The modulator 1101 may be configured to receive a plurality of symbols. Further, the modulator 1101 may modulate the plurality of symbols to obtain modulated signals. In one example, the modulator 1101 may be an OFDM modulator, which may use π/2-BPSK modulation, π/4-QPSK modulation, or the like. It is important to recognize that π/2-BPSK is different from BPSK in that π/2-BPSK uses identical constellations that are rotated by ninety degrees (90°). Further, π/2-BPSK has certain properties that BPSK does not possess. For instance, a π/2-BPSK modulated signal always changes phase at each bit transition, resulting in smaller phase transitions allowing for improved power amplifier performance and receiver synchronization. Similarly, π/4-QPSK modulation is different from QPSK in that π/4-QPSK modulation uses identical constellations that are rotated by forty-five degrees (45°). π/4-QPSK modulation also has certain properties that QPSK does not possess. For instance, π/4-QPSK modulation represented in the complex domain does not have any paths through the origin, resulting in reduced dynamic range of the modulated signal allowing for improved power amplifier performance.

In FIG. 11 , the CP insertion circuit 1109 may insert a CP to the modulated signals. The interpolation circuit 1111 and the pulse shaping filter 1113, in combination or individually, may be used to limit out-of-band power spectrum density such as for π/2-BPSK or π/4-QPSK modulated OFDMA signals. However, interpolation or pulse shaping filtering may cause magnitude variations of the filtered signal such as at π/2-BPSK θΓ π/4-QPSK modulated OFDMA signal boundaries where phase discontinuity may exist. To achieve low PAPR such as no more than 0.5 dB, these magnitude variations should be limited so that a corresponding power amplifier may operate at full capacity with little or no back-off. Various windowing techniques may be used to limit these magnitude variations. For instance, the window and overlap circuit 1105 may window and overlap the modulated signals to obtain windowed and overlapped signals. The window and overlap circuit 1105 may include a window circuit 1106, an overlap circuit 1107 or both. The window circuit 1106 may apply a windowing function such as a symmetrical windowing function. After applying the windowing function to the modulated signal with CP insertion to obtain the windowed signal, the overlap circuit 1107 may overlap one or more samples of two or more consecutive symbols of the windowed signal. In one example, two consecutive symbols are overlapped by two samples and summed so that the CP overhead remains its original length. A skilled artisan will readily recognize various windowing functions and overlap techniques. The interpolation circuit 1111 may interpolate or up-sample the windowed and overlapped signals to a sampling rate of the pulse shaping filter 1113. The pulse shaping filter 1113 may filter the windowed and overlapped signals to obtain filtered signals. In one example, the PAPR of the filtered signals may be no more than 0.5 dB.

For purposes of illustration and explanation only, embodiments of the present disclosure may be described herein in the context of operating in or in association with a RAN that communicates over radio communication channels with wireless devices, also interchangeably referred to as mobile terminals, wireless terminals, UEs and the like, using a particular radio access technology. More specifically, embodiments may be described in the context of the development of specifications for NB-loT, particularly as it relates to the development of specifications for NB-loT operation in spectrum or using equipment currently used by E-UTRAN, sometimes referred to as the Evolved UMTS Terrestrial Radio Access Network and widely known as the LTE system. However, it will be appreciated that the techniques may be applied to other wireless networks, as well as to successors of the E-UTRAN. Thus, references herein to signals using terminology from the 3GPP standards for LTE should be understood to apply more generally to signals having similar characteristics or purposes, in other networks.

A wireless device, as described herein, may be any type of wireless device capable of communicating with a network node or another wireless device (such as a user equipment, UE) over radio signals. In the context of the present disclosure, it should be understood that a wireless device may refer to a machine-to-machine (M2M) device, a machine-type

communications (MTC) device, or an NB-loT device. The wireless device may also be a UE, however it should be noted that the UE does not necessarily have a "user" in the sense of an individual person owning or operating the device. A wireless device may also be referred to as a radio device, a radio communication device, a wireless terminal, or simply a terminal - unless the context indicates otherwise, the use of any of these terms is intended to include device-to- device UEs or devices, machine-type devices or devices capable of machine-to-machine communication, sensors equipped with a wireless device, wireless-enabled table computers, mobile terminals, smart phones, laptop-embedded equipped (LEE), laptop-mounted equipment (LME), USB dongles, wireless customer-premises equipment (CPE), etc. In the discussion that follows, the terms machine-to-machine (M2M) device, machine-type communication (MTC) device, wireless sensor, and sensor may also be used. It should be understood that these devices may be UEs, but are generally configured to transmit or receive data without direct human interaction.

In an IOT scenario, a wireless device as described herein may be, or may be comprised in, a machine or device that performs monitoring or measurements, and transmits the results of such monitoring measurements to another device or a network. Particular examples of such machines are power meters, industrial machinery, or home or personal appliances, e.g.

refrigerators, televisions, personal wearables such as watches etc. In other scenarios, a wireless device as described herein may be comprised in a vehicle and may perform monitoring or reporting of the vehicle's operational status or other functions associated with the vehicle.

FIG. 12 illustrates one embodiment of a wireless device 1200 in accordance with various aspects as described herein. In some instances, the wireless device 1200 may be referred to as a network node, a base station (BS), an access point (AP), a UE, a mobile station (MS), a terminal, a cellular phone, a cellular handset, a personal digital assistant (PDA), a smartphone, a wireless phone, an organizer, a handheld computer, a desktop computer, a laptop computer, a tablet computer, a set-top box, a television, an appliance, a game device, a medical device, a display device, or some other like terminology. In other instances, the wireless device 1200 may be a set of hardware components. In FIG. 12, the wireless device 1200 may be configured to include a processor 1201 that is operatively coupled to an input/output interface 1205, a radio frequency (RF) interface 1209, a network connection interface 1211 , a memory 1215 including a random access memory (RAM) 1217, a read only memory (ROM) 1219, a storage medium

1221 or the like, a communication subsystem 1231 , a power source 1233, another component, or any combination thereof. The storage medium 1221 may include an operating system 1223, an application program 1225, data 1227, or the like. Specific devices may utilize all of the components shown in FIG. 12, or only a subset of the components, and levels of integration may vary from device to device. Further, specific devices may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc. For instance, a computing device may be configured to include a processor 1201 and a memory.

In FIG. 12, the processor 1201 may be configured to process computer instructions and data. The processor 1201 may be configured as any sequential state machine operative to execute machine instructions stored as machine-readable computer programs in the memory, such as one or more hardware-implemented state machines (e.g., in discrete logic, FPGA, ASIC, etc.); programmable logic together with appropriate firmware; one or more stored- program, general-purpose processors, such as a microprocessor or Digital Signal Processor (DSP), together with appropriate software; or any combination of the above. For example, the processor 1201 may include two computer processors. In one definition, data is information in a form suitable for use by a computer. It is important to note that a person having ordinary skill in the art will recognize that the subject matter of this disclosure may be implemented using various operating systems or combinations of operating systems.

In the current embodiment, the input/output interface 1205 may be configured to provide a communication interface to an input device, output device, or input and output device. The wireless device 1200 may be configured to use an output device via the input/output interface 1205. A person of ordinary skill will recognize that an output device may use the same type of interface port as an input device. For example, a USB port may be used to provide input to and output from the wireless device 1200. The output device may be a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. The wireless device 1200 may be configured to use an input device via the input/output interface 1205 to allow a user to capture information into the wireless device 1200. The input device may include a mouse, a trackball, a directional pad, a trackpad, a presence-sensitive input device, a display such as a presence-sensitive display, a scroll wheel, a digital camera, a digital video camera, a web camera, a microphone, a sensor, a smartcard, and the like. The presence-sensitive input device may include a digital camera, a digital video camera, a web camera, a microphone, a sensor, or the like to sense input from a user. The presence-sensitive input device may be combined with the display to form a presence-sensitive display. Further, the presence-sensitive input device may be coupled to the processor. The sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, another like sensor, or any combination thereof. For example, the input device 1205 may be an accelerometer, a magnetometer, a digital camera, a microphone, and an optical sensor.

In FIG. 12, the RF interface 1209 may be configured to provide a communication interface to RF components such as a transmitter, a receiver, and an antenna. The network connection interface 1211 may be configured to provide a communication interface to a network 1243a. The network 1243a may encompass wired and wireless communication networks such as a local-area network (LAN), a wide-area network (WAN), a computer network, a wireless network, a telecommunications network, another like network or any combination thereof. For example, the network 1243a may be a Wi-Fi network. The network connection interface 1211 may be configured to include a receiver and a transmitter interface used to communicate with one or more other nodes over a communication network according to one or more

communication protocols known in the art or that may be developed, such as Ethernet, TCP/IP, SONET, ATM, or the like. The network connection interface 1211 may implement receiver and transmitter functionality appropriate to the communication network links (e.g., optical, electrical, and the like). The transmitter and receiver functions may share circuit components, software or firmware, or alternatively may be implemented separately.

In this embodiment, the RAM 1217 may be configured to interface via the bus 1202 to the processor 1201 to provide storage or caching of data or computer instructions during the execution of software programs such as the operating system, application programs, and device drivers. In one example, the wireless device 1200 may include at least one hundred and twenty-eight megabytes (128 Mbytes) of RAM. The ROM 1219 may be configured to provide computer instructions or data to the processor 1201. For example, the ROM 1219 may be configured to be invariant low-level system code or data for basic system functions such as basic input and output (I/O), startup, or reception of keystrokes from a keyboard that are stored in a non-volatile memory. The storage medium 1221 may be configured to include memory such as RAM, ROM, programmable read-only memory (PROM), erasable programmable readonly memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, floppy disks, hard disks, removable cartridges, flash drives. In one example, the storage medium 1221 may be configured to include an operating system

1223, an application program 1225 such as a web browser application, a widget or gadget engine or another application, and a data file 1227.

In FIG. 12, the processor 1201 may be configured to communicate with a network 1243b using the communication subsystem 1231. The network 1243a and the network 1243b may be the same network or networks or different network or networks. The communication subsystem 1231 may be configured to include one or more transceivers used to communicate with the network 1243b. For example, the communication subsystem 1231 may be configured to include one or more transceivers used to communicate with one or more remote transceivers of a radio access network (RAN) according to one or more communication protocols known in the art or that may be developed, such as IEEE 802.xx, CDMA, WCDMA, GSM, LTE, UTRAN, WiMax, or the like. Each transceiver may implement transmitter or receiver functionality appropriate to the RAN links (e.g., frequency allocations and the like). Further, the transmitter and receiver functions of each transceiver may share circuit components, software or firmware, or alternatively may be implemented separately.

In the current embodiment, the communication functions of the communication subsystem 1231 may include data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. For example, the communication subsystem 1231 may include cellular communication, Wi-Fi communication, Bluetooth communication, and GPS communication. The network 1243b may encompass wired and wireless communication networks such as a local-area network (LAN), a wide-area network (WAN), a computer network, a wireless network, a telecommunications network, another like network or any combination thereof. For example, the network 1243b may be a cellular network, a W-Fi network, and a near-field network. The power source 1233 may be configured to provide an alternating current (AC) or direct current (DC) power to components of the wireless device 1200. In FIG. 12, the storage medium 1221 may be configured to include a number of physical drive units, such as a redundant array of independent disks (RAID), a floppy disk drive, a flash memory, a USB flash drive, an external hard disk drive, thumb drive, pen drive, key drive, a high-density digital versatile disc (HD-DVD) optical disc drive, an internal hard disk drive, a Blu- Ray optical disc drive, a holographic digital data storage (HDDS) optical disc drive, an external mini-dual in-line memory module (DIMM) synchronous dynamic random access memory (SDRAM), an external micro-DIMM SDRAM, a smartcard memory such as a subscriber identity module or a removable user identity (SIM/RUIM) module, other memory, or any combination thereof. The storage medium 1221 may allow the wireless device 1200 to access computer- executable instructions, application programs or the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied in storage medium 1221 , which may comprise a computer-readable medium.

The functionality of the systems and methods described herein may be implemented in one of the components of the wireless device 1200 or partitioned across multiple components of the wireless device 1200. Further, the functionality of the methods described herein may be implemented in any combination of hardware, software or firmware. In one example, the communication subsystem 1231 may be configured to include any of the components described herein. Further, the processor 1201 may be configured to communicate with any of such components over the bus 1202. In another example, any of such components may be represented by program instructions stored in memory that when executed by the processor 1201 performs the corresponding functions described herein. In another example, the functionality of any of such components may be partitioned between the processor 1201 and the communication subsystem 1231. In another example, the non-computative-intensive functions of any of such components may be implemented in software or firmware and the computative- intensive functions may be implemented in hardware. In another example, any of the functionality of the systems and methods described herein may be implemented in a transmitter of the wireless device 1200.

In another embodiment, the techniques described herein may be applied in an

Orthogonal Frequency Division Multiple Access (OFDMA) transmitter of a wireless device. The OFDMA transmitter may include an OFDMA modulator, a CP insertion circuit, a pulse shaping filter, a window and overlap circuit, the like, or any combination thereof. The OFDMA modulator may modulate a plurality of symbols with the modulation adjusted for a rotation of ττ/2, ττ/4, or the like between symbols in time to obtain modulated signals. The CP insertion circuit may insert a CP to the modulated signals. A pulse shaping filter may filter the modulated signals to obtain first filtered signals. The pulse shaping filter may be a Gaussian filter or a non-Gaussian filter. The window and overlap circuit may window and overlap the filtered signals to obtain windowed and overlapped signals. In another embodiment, the OFDMA transmitter may include another pulse shaping filter. The other pulse shaping filter may filter the windowed and overlapped signals.

In another embodiment, the OFDMA transmitter may include one or more interpolator circuits to interpolate/up-sample a signal to a sampling rate of any of the components of the transmitter.

FIG. 1 3 illustrates one embodiment of a wireless device 1 300 for controlling PAPR of a signal in a communication system in accordance with various techniques described herein. In FIG. 1 3, the wireless device 1300 may include an OFDMA modulator 1 301 , a CP insertion circuit 1309, a pulse shaping filter 1 31 3, and a window and overlap circuit 1305. In one example, the OFDMA modulator 1 301 may be configured to receive a serial stream of symbols and may inverse multiplex the symbols into parallel streams of symbols. Further, the OFDMA modulator 1301 may map the binary data in each stream to a π/2-BPSK constellation, ττ/4- QPSK constellation or the like to obtain parallel streams of complex symbols. Further, the OFDMA modulator 1 301 may perform an inverse fast Fourier transform (FFT) on each set of complex symbols from the parallel streams to obtain modulated signals, represented as a set of complex time-domain samples. While one exemplary representation of an OFDMA modulator is provided herein, a skilled artisan will readily recognize that many other representations of an OFDMA modulator are available.

In FIG. 1 3, the CP insertion circuit 1309 may insert a CP to the modulated signals. The pulse shaping filter 1 31 3 may be used to limit out-of-band power spectrum density such as for π/2-BPSK ΟΓ ΤΤ/4-QPSK modulated OFDMA signals. Further, the pulse shaping filter 1 31 3 may perform its pulse shaping filtering at the sample rate of the modulated signals. The window and overlap circuit 1305 may window and overlap the modulated signals to obtain windowed and overlapped signals. The window and overlap circuit 1305 may include a window circuit 1306, an overlap circuit 1307 or both. The window circuit 1306 may apply a windowing function such as a symmetrical windowing function that has a certain length. In one example, this length may include a sample length of the inverse FFT used in the modulator 1301 , a sample length of the CP, and any cyclical extension. After applying the windowing function to the modulated signal with CP insertion to obtain the windowed signal, the overlap circuit 1 307 may overlap one or more samples of two or more consecutive symbols of the windowed signal. In one example, two consecutive symbols are overlapped by two samples and summed so that the CP overhead remains its original length.

A third pulse shaping filter may be at least a 7-tap Gaussian FIR filter that is

characterized by a substantially flat passband. The third pulse shaping filter may be similar to the filter described by downlink (DL) transmit (Tx) contribution. The time-domain impulse response of the third pulse shaping filter may have the following filter coefficients:

ao is equivalent to about 0.0451 ,

ai is equivalent to about 0.2002, a _∑ is equivalent to about 0.4898,

a3 is equivalent to about 0.6602,

B4 is equivalent to about 0.4898,

as is equivalent to about 0.2002, and

ae is equivalent to about 0.0451.

These filter coefficients are normalized for unity gain. Further, these filter coefficients may be quantized or otherwise modified such as for a particular filter implementation.

A fourth pulse shaping filter may be at least an 11 -tap FIR filter. The time-domain impulse response of the fourth pulse shaping filter may have the following filter coefficients: a ₀ s equivalent to about -0.0647,

ai s equivalent to about -0.0563,

a ₂ s equivalent to about 0.0615,

a ₃ s equivalent to about 0.2759,

a ₄ s equivalent to about 0.4922,

a ₅ s equivalent to about 0.5839,

a ₆ s equivalent to about 0.4922,

a? s equivalent to about 0.2759,

a ₈ s equivalent to about 0.0615,

a ₉ s equivalent to about -0.0563, and

aw is equivalent to about -0.0647.

These filter coefficients are normalized for unity gain. Also, these filter coefficients may be quantized or otherwise modified such as for a particular filter implementation.

FIG. 14 illustrates one embodiment of a pulse shaping filter 1400 in accordance with various aspects described herein. The operations of the filter 1400 are generally described by the following convolution equation: where x(n - k) indicates the windowed and overlapped signal, y (n) indicates the filtered signal, a, indicates filter coefficient / ^' , and N indicates the filter order. The z-domain transfer function of this convolution equation is as follows:

N

H(z) = a _n z °

The computation operations of the filter 1400 is based on this transfer function. For instance, filter coefficients 1403a-n, delays 1401 a-n and summation operations 1405a-n are arranged to indicate that the windowed and overlapped signal and its delayed versions by the delays 1401 a-n are multiplied by the filter coefficients 1403a-n with the partial results summed by the summation operations 1405a-n, resulting in the filtered signal according to this transfer function. While one exemplary representation of a pulse shaping filter is provided herein, a skilled artisan will readily recognize that many other representations of a pulse shaping filter are available.

In one embodiment, a method performed by a wireless device for controlling a PAPR of a signal in a communication system may include modulating a plurality of symbols to obtain modulated signals. Further, the method may include windowing and overlapping the modulated signals to obtain windowed and overlapped signals. Also, the method may include filtering the windowed and overlapped signals using a pulse shaping filter to obtain filtered signals. The PAPR of the filtered signals may be no more than about 0.5 dB.

In another embodiment, the PAPR of the filtered signals may be no more than about 0.1 dB.

In another embodiment, the PAPR of the filtered signals may be no more than about 0.04 dB.

In another embodiment, 95% of an energy of the pulse shaping filter may be in less than half of a length in time of the pulse shaping filter.

In another embodiment, a length in time of the pulse shaping filter may be in a range from about eight microseconds (8 usee.) to about eleven microseconds (1 1 usee.) and about

95% of an energy of the pulse shaping filter is in a range from about three microseconds (3 usee.) to about four microseconds (4 usee). Further, the sampling rate may be about 1.28

Msps.

In another embodiment, the method may include inserting a cyclic prefix in the plurality of symbols. A length in time of the pulse shaping filter may be less than a length in time of the cyclic prefix.

In another embodiment, the pulse shaping filter may have a substantially flat passband.

In another embodiment, the pulse shaping filter may be a Gaussian filter.

In another embodiment, the method may include modulating using one of π/2-BPSK modulation and π/4-QPSK modulation.

In another embodiment, each symbol may be an OFDM symbol.

In one embodiment, a wireless device for controlling a peak-to-average power ratio

(PAPR) of a signal in a communication system may include a modulator, a window and overlap circuit, a filter, another component, or any combination thereof. The modulator may be configured to modulate a plurality of symbols to obtain modulated signals. The window and overlap circuit may be configured to window and overlap the modulated signals to obtain windowed and overlapped signals. The filter may be configured to filter the windowed and overlapped signals using a pulse shaping filter to obtain filtered signals. Further, the PAPR of the filtered signals may be no more than about 0.5 dB. In another embodiment, the wireless device may include a cyclic prefix insertion circuit configured to insert a cyclic prefix in the plurality of symbols. Also, a length in time of the pulse shaping filter may be less than a length in time of the cyclic prefix.

In another embodiment, the modulator may be configured to modulate using one of ττ/2- BPSK modulation and π/4-QPSK modulation.

ADDENDUM:

NB-LTE Uplink:

NB-LTE is based on single-carrier frequency-division multiple-access (SC-FDMA), same as LTE uplink. This allows flexible UE bandwidth allocation including single tone transmission as a special case of SC-FDMA.

Uplink Modulation:

NB-LTE uplink contains three basic channels including M-PRACH, M-PUCCH, and M- PUSCH.

Transmit Filters:

The amplitude variations of a transmission depend on the transmit filter, and in this contribution two transmit filters will be studied. The first one, filter 1 , is a 14-tap filter and is characterized by a rather flat passband. The second one, filter 2, is a 10-tap Gaussian filter. The two filters are presented in FIG. 1 and FIG. 2, respectively.

One realization of the transmitter may be to generate symbols of length 128 samples, before concatenating them with a cyclic prefix of 9 samples (10 samples for every seventh symbol). A subcarrier spacing of 2.5 kHz corresponds to transmitting these samples at 320 ksps (kilo-samples per second). For transmit filtering, this signal may be up-sampled a number of times and fed through a transmit filter. Other implementation alternatives are also possible.

In this contribution, for simplicity, the transmitter is operating directly at 1.28 Msps, the sampling rate at which the transmit filter is applied in the evaluations. With such a setup, each OFDM symbol is 512 samples long excluding the cyclic prefix. At this sampling rate, the length of each filter is about 1 1 us and 8 us, respectively, but 95% of the energy is contained within 3-4 usee. With an NB-LTE UL with 2.5 kHz subcarrier spacing, the cyclic prefix length is 28-31 usee, long, and the filters are well within the cyclic prefix length.

Peak-to-Average Power Ratio:

Random symbols in the two constellation alphabets have been generated and mapped to one subcarrier, and the instantaneous power compared to the average power of the transmitted samples has been measured. FIG. 3 shows the complementary cumulative distribution function (CDF) of the instantaneous power to average power ratio for the 72 different subcarriers that are available in NB-LTE uplink when transmitted using filter 1. As shown, pi/2 BPSK at the worst subcarrier has a 1.0 dB PAPR with this transmit filter. By using a windowing and overlap method with an overlap of 4 samples (at 1.28 Msps), the PAPR reduces to 0.5 dB as shown in FIG. 4. The same 0.5 dB PAPR is achieved also with pi/4 QPSK. If instead, filter 2 (Gaussian filter) is used, the PAPR is 1.1 dB for pi/2 BPSK as shown in FIG. 5. However, if windowing and a 2 sample overlap are used with filter 2, the PAPR reduces to 0.1 dB as shown in FIG. 6. With a 4 sample overlap, the PAPR reduces further to 0.04 dB. The same PAPR is achieved with pi/4 QPSK.

FIG. 7 shows an example of the instantaneous relative power of a signal with pi/2-BPSK and filter 2. Most of the time the signal amplitude is constant, but at the symbol boundaries, at the cyclic prefix, the amplitude decreases during a few samples. However, this decrease may be anticipated since it is determined by the OFDM symbol rate. Both the average and the maximum amplitude are close to 1 , which leads to a very low PAPR. FIG. 8 summarizes the PAPR results for filter 1 , and FIG. 9 summarizes the PAPR results for filter 2.

The previous detailed description is merely illustrative in nature and is not intended to limit the present disclosure, or the application and uses of the present disclosure. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding field of use, background, summary, or detailed description. The present disclosure provides various examples, embodiments and the like, which may be described herein in terms of functional or logical block elements. The various aspects described herein are presented as methods, devices (or apparatus), systems, or articles of manufacture that may include a number of components, elements, members, modules, nodes, peripherals, or the like. Further, these methods, devices, systems, or articles of manufacture may include or not include additional components, elements, members, modules, nodes, peripherals, or the like.

Furthermore, the various aspects described herein may be implemented using standard programming or engineering techniques to produce software, firmware, hardware (e.g., circuits), or any combination thereof to control a computing device to implement the disclosed subject matter. It will be appreciated that some embodiments may be comprised of one or more generic or specialized processors such as microprocessors, digital signal processors, customized processors and field programmable gate arrays (FPGAs) and unique stored program

instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the methods, devices and systems described herein. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some

combinations of certain of the functions are implemented as custom logic circuits. Of course, a combination of the two approaches may be used. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.

The term "article of manufacture" as used herein is intended to encompass a computer program accessible from any computing device, carrier, or media. For example, a computer- readable medium may include: a magnetic storage device such as a hard disk, a floppy disk or a magnetic strip; an optical disk such as a compact disk (CD) or digital versatile disk (DVD); a smart card; and a flash memory device such as a card, stick or key drive. Additionally, it should be appreciated that a carrier wave may be employed to carry computer-readable electronic data including those used in transmitting and receiving electronic data such as electronic mail (e- mail) or in accessing a computer network such as the Internet or a local area network (LAN). Of course, a person of ordinary skill in the art will recognize many modifications may be made to this configuration without departing from the scope or spirit of the subject matter of this disclosure.

Throughout the specification and the embodiments, the following terms take at least the meanings explicitly associated herein, unless the context clearly dictates otherwise. Relational terms such as "first" and "second," and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The term "or" is intended to mean an inclusive "or" unless specified otherwise or clear from the context to be directed to an exclusive form. Further, the terms "a," "an," and "the" are intended to mean one or more unless specified otherwise or clear from the context to be directed to a singular form. The term "include" and its various forms are intended to mean including but not limited to. References to "one

embodiment," "an embodiment," "example embodiment," "various embodiments," and other like terms indicate that the embodiments of the disclosed technology so described may include a particular function, feature, structure, or characteristic, but not every embodiment necessarily includes the particular function, feature, structure, or characteristic. Further, repeated use of the phrase "in one embodiment" does not necessarily refer to the same embodiment, although it may. The terms "substantially," "essentially," "approximately," "about" or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1 % and in another embodiment within 0.5%. A device or structure that is "configured" in a certain way is configured in at least that way, but may also be configured in ways that are not listed.