Method and apparatuses for generating an on-off keying, OOK, signal by a multiple carrier generator

Abstract

A method and apparatus for generating an On-Off Keying, OOK, signal by a multiple carrier generator is disclosed. The carriers among the multiple carriers are orthogonal. For a first OOK symbol, a power level for active carriers is assigned and the first OOK symbol is formed from the assigned power level and a first frequency offset from frequencies of the active carriers. For a second OOK symbol, the power level for active carriers is assigned and the second OOK symbol is formed from the assigned power level and a second frequency offset from the frequencies of the active carriers.

Description

METHOD AND APPARATUSES FOR GENERATING AN ON-OFF KEYING, OOK,SIGNAL BY A MULTIPLE CARRIER GENERATORINTRODUCTION

[0001] On-Off Keying (OOK) is a modulation scheme where the presence of a signal represents the ON part and the absence of the signal represents the OFF part. Principles of an OOK signal is depicted in Fig. 1, where the presence of a signal is labeled as ON part and the absence of a signal is labeled as OFF part. For example, the ON and OFF parts could represent binary digits, or the transition between ON to OFF state and OFF to ON state could represent binary digits. There currently exist certain challenge(s).

[0002] In order to decode OOK, the receiver has to estimate which signal level corresponds to the presence of a signal and which signal level corresponds to the absence of a signal in order to determine a threshold value which can be used for making a decision whether the received signal was ON or OFF.

[0003] Manchester Coding is a modulation means used to simplify clock recovery and to simplify demodulation by ensuring that the average signal level of the signal carries no information. The ideas are easily explained by means of an illustration. Referring to Fig. 2, which illustrates principles of Manchester coded data, a data bit with value one is represented by (encoded to) a logical one followed by a logical zero, whereas a data bit with value zero is represented by a logical zero followed by a logical one. Alternatively, the encoding can be swapped so that a data bit with value 1 is represented by a logical zero followed by a logical one.

[0004] The clock recovery is simplified because there will always be a transition from zero to one or vice versa in the middle of each symbol irrespectively of what the data is.

[0005] The decoding of the Manchester coded symbol is essentially done by comparing the first and the second half of the symbols and decide in favor of a logical one if the first half of the symbol is larger than the second half of the same symbol. Implementation-wise, a metric, m, is generated as

[0006] m = ro- ri,

[0007] where ro and n represent the signal during the first and second half of the signaling interval, respectively, see Fig. 2. An estimate of the kth data symbol, dk, is then obtained by just considering the metric m, i.e. , d = 1 if m > 0 and d = 0 if m < 0.

[0008] Since the metric, m, is generated by subtracting the second half of the symbol from the first half, the average signal level will be removed and will thus have no impact on the metric used for making the decision.

[0009] Because of the properties of the Manchester coding when it comes to being insensitive to the average signal level, it is an attractive approach when the alternative would be to estimate a decision threshold for when to decide in favor of a logical one or a logical zero.

[0010] One way to generate OOK may be to just send a carrier wave (CW) which is turned on or off. The occupied bandwidth of such an approach would be proportional to the data rate. As an example, if the data rate would be 100 kb / s, the main lobe of the spectrum of the transmitted signal would be 200 kHz. In many situations, it may be advantageous or even required that the transmitted signal occupies a minimum bandwidth, which then becomes problematic when the data rate is low.

[0011] Often the data rate must be low in order to achieve the desired range as OOK received by a simple receiver typically has quite poor performance in terms of the required signal-to-noise-ratio (SNR). In the IEEE 802.1 Iba standard, where wake-up-radio operation is standardized, an alternative approach for generating OOK is used. The idea being to reuse the transmitter architecture available in IEEE 802.11, and in particular the use of orthogonal frequency division multiplexing (OFDM) based on an Inverse Fast Fourier Transform (IFFT). In this case, a Wake-Up Signal (WUS) is transmitted on 13 sub-carriers in the center of a 20 MHz channel, see Fig. 3 which is an illustration of how the WUS is generated together with the data signal using an IFFT. The reason why 13 sub-carriers were selected was that this gives a signal bandwidth which exceeds 4 MHz, which is required for the frequency band where IEEE 802.1 Iba is intended to operate.

[0012] The reason for not selecting a wider channel was that it was believed to be advantageous to have a guard band to the adjacent channels. It has been shown, however, that using a wider bandwidth for the OOK can give a substantial improvement in the sensitivity performance, especially when the total transmitted power is limited due to power spectral density (PSD) limitation.

[0013] Although generation of OOK using an OFDM transmitter is very attractive, the symbol rate of the OOK should preferably be aligned with the symbol rate of the OFDM system. Specifically, the duration of an ON / OFF period should be an integer number of OFDM symbols, e.g. 1 or 2.

[0014] In general, it is not allowed to transmit a signal at an arbitrary high power level. Sometime, the regulatory rules have requirements that the total power must not exceed a certain power, e.g. must not exceed 20 dBm (lOOmW). Sometimes, the rules are instead put on Power Spectral Density (PSD), e.g., the maximum PSD must not exceed 10 dBm / MHz. In the latter case, this means that a signal with a larger bandwidth can be transmitted at higher power. There may also be requirements on both the maximum power and the maximum PSD, in which case one must make sure that both are fulfilled.

[0015] Concerning the requirements on PSD, this often refers to the maximum PSD measured over 1 MHz. This means that if the transmitted signal has an uneven PSD over the used bandwidth, the peak value, i.e., the maximum power measured over 1 MHz bandwidth, will limit the total power that can be used. For this reason, it is desirable that the transmitted signal has a PSD that is as flat as possible over the used bandwidth.

[0016] It is thus a challenge to provide an efficient OOK signal that the receiver easily can detect, and at the same time not violate any regulations and / or cause interference to the detriment for other users of the spectrum.

[0017] Due to requirements on maximum PSD, it is desirable to have PSD that is as flat as possible so that the total power (integrated over the transmission bandwidth) becomes as large as possible. Without going into details, the transmission of random data can often be made to result in a flat spectrum, whereas transmission of deterministic signals may cause spectral lines thus resulting in undesired spectrum properties. An example of when spectrum lines appear is OOK if the ON signals are represented in exactly the same way, e.g. with the same phase. To avoid, or at least significantly suppress, these spectrum lines one can randomize the phase as done in e.g. IEEE 802.1 Iba. For example, a pseudo-random bit stream is used to generate binary phase shift keyed, BPSK, symbols, taking on the values +1 and -1, and the ON waveform is then multiplied by this binary symbol. This achieves a much more flat PSD, and as the information used by the receiver is only in the amplitude the performance will be improved and the randomization will be completely transparent to the receiver.

[0018] In case it is desirable to support OOK with relatively high data rates and generate the signal using an IFFT, the duration of an OFDM symbol must be short. In particular when Manchester coding is used this becomes even more pronounced as with Manchester coding each information symbol consists of two OFDM symbols. When the duration of an OFDM symbol is decreased, the sub-carrier spacing must increase to ensure the sub-carriers are orthogonal. Specifically, the sub-carrier spacing is inversely proportional to the OFDM symbolduration (excluding the cyclic prefix). Now, referring to the discussion about PSD limitations, the result of a large sub-carrier spacing is that the resulting fluctuations in the PSD will reduce the maximum allowed transmit power.

[0019] It should also be noted that the above randomization will not help to solve this problem as the reason for the fluctuations are due to the properties of the signal generation in the IFFT and does not relate to that the data as such would be deterministic.

[0020] Certain aspects of the disclosure and their embodiments may provide solutions to these or other challenges. This disclosure introduces a method for making the PSD essentially flat even if the OOK signal is generated using an IFFT. The approach for achieving this is to add a slight frequency offset to the signals such that the different OFDM signals will not have the PSD peaks at the same frequencies. As a result, the average PSD will be essentially flat. The procedure is completely transparent for the receiver, as the receiver is only detecting the envelope of the transmitted signal which is not impacted by this small frequency shift.SUMMARY

[0021] Aspects of the approach are defined by the appended independent claims. Embodiments thereof are given in the dependent claims.

[0022] According to a first aspect, there is provided a method of generating an On-Off Keying, OOK, signal by a multi-carrier generator where the carriers among the multiple carriers are orthogonal. For a first OOK symbol, the method comprises assigning a power level for active carriers, and forming the first OOK symbol from the assigned power level and a first frequency offset from frequencies of the active carriers. For a second OOK symbol, the method comprises assigning the power level for active carriers, and forming the second OOK symbol from the assigned power level and a second frequency offset from the frequencies of the active carriers, where the second frequency offset is different than the first frequency offset.

[0023] For a third OOK symbol the method may comprise assigning the power level for active carriers, and forming the third OOK symbol from the assigned power level and a third frequency offset from the frequencies of the active carriers, where the third frequency offset is different than the first and second frequency offset.

[0024] The the multi-carrier generator may be an Inverse Fast Fourier Transformer, IFFT, the multiple carriers correspond to a size of the IFFT, and the active carriers correspond to points of the IFFT to produce OOK symbols of desired length. The frequency offsets may differ by a carrier spacing divided by N, where N is the size of the IFFT used for OOK generation.Subsequent symbols following the first, second, or third symbols may be formed using a first, second, or third frequency offset, respectively, in a periodic pattern with a periodicity of N.

[0025] The frequency offsets may be applied by multiplying the respective active carrier with a sinusoid with a frequency corresponding to the respective frequency offset. The method may comprise adding a cyclic prefix to respective carrier before multiplying with the respective sinusoid.

[0026] The method may comprise randomizing ON signals of the OOK symbol with symbols of a pseudo-random sequence, respectively.

[0027] According to a second aspect, there is provided a signal generator arranged to perform the method of the first aspect.

[0028] According to a third aspect, there is provided a transmitter comprising a signal generator according to the second aspect and wireless transmitter circuitry arranged to transmit the OOK signal.

[0029] According to a fourth aspect, there is provided an access point comprising transceiver and processing circuitry capable of operating a communication in a Basic Service Set, wherein the access point further comprises a transmitter according to the third aspect.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings.

[0031] Fig. 1 illustrates an On-Off Keying, OOK, signal.

[0032] Fig. 2 illustrates Manchester coding of a data signal.

[0033] Fig. 3 schematically illustrates a signal generator implemented through an Inverse Fast Fourier Transformer, IFFT, for forming a desirable OOK signal to be transmitted.

[0034] Fig. 4 illustrates an example of Power Spectral Density, PSD, of a signal generated using an 8 points IFFT without application of the suggested approach.

[0035] Fig. 5 illustrates an example of PSD of a signal generated using a 4 points IFFT without application of the suggested approach.

[0036] Figs 6 and 7 illustrate the flattening of the PSD using the suggested approach for different IFFT setups. The flattened PSD illustrated by the solid line is obtained by averaging the PSDs for the individual symbols illustrated by the dashed lines.

[0037] Fig. 8 illustrates a communication system in which some entities benefit from the suggested approach.

[0038] Fig. 9 schematically illustrates elements of a terminal device which benefit from the suggested approach.

[0039] Fig. 10 schematically illustrates elements of a network node which benefit from the suggested approach.

[0040] Fig. 11 schematically illustrates a signal generator according to embodiments.

[0041] Fig. 12 is a flow chart illustrating methods according to embodiments.DETAILED DESCRIPTION

[0042] An approach for generating an on-off keying, OOK, signal by a multiple carrier generator will now be described, which provides for flattening the Power Spectral Density, PSD, of a signal to be transmitted. The approach is thus to, as schematically illustrated in Fig. 12, for a first OOK symbol, assigning 10 a power level for active carriers, forming 20 the first OOK symbol from the assigned power level and a first frequency offset from frequencies of the active carriers, and for a second OOK symbol, assigning 30 the power level for active carriers and forming 40 the second OOK symbol from the assigned power level and a second frequency offset from the frequencies of the active carriers. For a third OOK symbol (and subsequent), when present, the method proceeds with assigning 50 the power level for active carriers and forming 60 the third OOK symbol from the assigned power level and a third frequency offset from the frequencies of the active carriers, etc. for coming symbols. There may be a periodicity, which may be attractive from an implementation point of view when a multitude of symbols are to be sent, in the assignment of frequency offsets. For example, when the multi-carrier generator is implemented through an Inverse Fast Fourier Transformer, IFFT, with size N, the applicable frequency offsets can be set to differ from each other by an applied carrier spacing divided by the size N. Periodicity of re-use of frequency offset can then be set to N, i.e., the respective frequency offset is re-used every N symbol.

[0043] Application of the frequency offsets to the symbols can be made in different ways. One way is to do it in pre-processing when feeding input to the multi -carrier generator. Another way is to post-process the respective carrier. General for these are the output effect of respectiveactive carrier being multiplied with a sinusoid with a frequency corresponding to the respective frequency offset. As will be further explained below, the application of a cyclic prefix is still possible with the suggested approach. Further is to be mentioned that the above described approach of randomizing ON signals to avoid spectral lines in the PSD is also combinable with the suggested approach for further flattening of the PSD.

[0044] Certain embodiments may provide one or more of the following technical advantage(s). The proposed solution allows for using a larger total transmit power when an OOK signal is generated using an IFFT. The increased transmit power directly translates to an increased transmission range and / or facilitating for the receiver to properly detect the OOK signal.

[0045] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art

[0046] It will now be described in detail how the suggested approach works. For ease of the description, the approach will be described for a system with Wi-Fi-like parameters. However, as is obvious for anyone of ordinary skill in the art, the invention is not limited to Wi-Fi nor to these specific parameters.

[0047] Suppose the sampling rate is 20 MHz and that the channel bandwidth is also 20 MHz. This corresponds to Wi-Fi operating in a 20 MHz channel. The IFFT size may be 64, which is the IFFT size used in e.g. IEEE 802.1 In and IEEE 802.1 lac. For later versions of WiFi, e.g. based on IEEE 802.1 lax and IEEE 802.1 Ibe, an IFFT size of 256 is used for the data in a 20 MHz channel.

[0048] Now, suppose one would like to use a 64-point IFFT at 20 MHz sampling rate. This means that the duration of a corresponding OFDM symbol is 64 / 20e6 = 3.2 ps. The sub-carrier spacing is 20e6 / 64 = 312.5 kHz. Typically, a CP of 0.8 ps is added so that the total duration of an OFDM symbol, including the CP becomes 4 ps.

[0049] If Manchester coded OOK is to be generated using the above IFFT, the duration of one Manchester coded symbol would be 8 ps, corresponding to 125 kb / s.

[0050] To support larger data rates using the same approach, one would have to reduce the size of the IFFT. Since there is a linear relationship between the IFFT size and the symbol duration, it follows that to support 1 Mb / s an 8-point IFFT should be used and to support 2 Mb / s, a 4-point FFT should be used.

[0051] In Fig. 4 the PSD is shown for the case that the signal is generated using an 8-point FFT. To obtain some guard band to the adjacent channels, only 6 of the 8 sub-carriers are used. As discussed above, this corresponds to the situation where it is desirable to generate a 1 Mb / s Manchester coded OOK signal.

[0052] Fig. 5 is an illustration of PSD for a 4-point IFFT, when only 3 sub-carriers are used and shows the corresponding PSD when the generated signal corresponds to 2 Mb / s Manchester coded OOK.

[0053] As can be seen in both these figures, the PSD of the transmitted signal is not flat, but one can easily identify the location of the individual tones. This is not unique for a small size IFFT, but the problem is that the distance between the peaks as well as the widths of the peaks is relatively large compared to the 1 MHz resolution that is used for measuring the maximum PSD. As the maximum PSD effectively is measured by moving a 1 MHz filter across the bandwidth of the signal, it is readily seen from the figures above that such a 1 MHz filter will not be able to average out the variations, but instead such a filter will essentially not be wider than the peak, especially for the 2 Mb / s signal.

[0054] To address the above identified problem, the following method is disclosed. Rather than generating all symbols with exactly the same frequency positions of the sub-carriers, the positions of the sub-carriers are slightly shifted for different symbols.

[0055] As an example, consider the 1 Mb / s signal above which is generated using an 8- point FFT with sub-carrier spacing 2.5 MHz. If one symbol has the spectrum shown in Fig. 4 one may shift the spectrum for the next symbol by 2.5 MHz / 8 = 312.5 kHz, simply by multiplying the signal after the CP has been added by a sinusoid with this frequency. Then the next signal can be shifted by 2x312.5 kHz, and so on until the signal is shift 7x2.5 MHz / 8 = 2.1875 MHz. After these 8 symbols, the procedure is repeated starting with not adding any frequency offset then adding a frequency offset of 312.5 kHz etc. The corresponding PSD when this method is applied is depicted in Fig. 6 which is an illustration of the PSD density for an 8- point IFFT, when only the 6 sub-carriers in the center are used and the approach of shifting the frequency for different symbols is applied. The dashed curves correspond to the PSD for the different frequency offsets and the solid curve corresponds to the average PSD obtained by taking the average of the dashed curves.

[0056] The corresponding PSD for 2 Mb / s is shown in Fig. 7 which is an illustration of the PSD density for a 4-point IFFT, when only the 3 sub-carriers are used and the approach ofshifting the frequency for different symbols is applied. In this case, the frequency is shifted in 4 steps, each being 1.25 MHz wide.

[0057] What step size to use will depend on how fast one needs to achieve a good averaging in frequency. If the averaging time is long, one may take small steps, but if the averaging time is relatively small, one must take steps large enough to get a uniform usage of the spectrum in a sufficiently small time.

[0058] Now, the reason why one wanted to have a flat spectrum as in Fig. 6 and Fig. 7Error! Reference source not found, was that this would allow for a higher total power. Comparing the PSD for these two figures with the corresponding one in Fig. 4Error! Reference source not found, and Fig. 5, one can determine the gain by integrating the PSD to obtain the total power for the different cases. The maximum power is scaled to be the same (and it is expected that the maximum power if measured over 1 MHz would be very similar). It is found that the gain in case of 1 Mb / s is about 1.2 dB and the gain in case of 2 Mb / s is about 1.4 dB.

[0059] It should be noted that this gain is obtained at very low additional complexity at the transmitter and without any changes in the receiver.

[0060] Fig. 8 is an example of a communication system 1100 according to some embodiments. As used herein, the communication system 1100 includes multiple access points (APs) 1110 (with four exemplary APs 1110A, 1110B, 1110C, and HOD being depicted) and multiple stations (STAs) 112 (referred to individually as STA 112A, STA 112B, STA 112C, STA 112D, and STA 112E). STA 112A is served by AP 110A in a first basic service set (BSS) 120A. STA HOB and STA HOC are served by AP HOB in a second BSS, BSS 120B. STA 112D is served by AP 110C in a third BSS, BSS 120C. STA 112E is served by AP 110D in a fourth BSS, BSS 120D. Stations 112 may be non-AP STAs and correspond to various kinds of wireless devices, for example, user terminals, such as mobile or stationary computing devices like smartphones, laptop computers, desktop computers, tablet computers, gaming devices, HMDs, or the like. Further, stations 112 could, for example, correspond to other kinds of equipment like smart home devices, printers, multimedia devices, data storage devices, or the like.

[0061] Each of STAs 112 may connect through a radio link to one of APs 110. For example, depending on location or channel conditions experienced by a given STA 112, the STA may select an appropriate AP and BSS for establishing the radio link. The radio link may be based on one or more orthogonal frequency-division multiplexing (OFDM) carriers from afrequency spectrum that is shared on the basis of a contention-based mechanism, e.g., an unlicensed or license exempt band like 2.4 GHz Industrial, Scientific, and Medical (ISM) band, the 5 GHz band, the 6 GHz band, or the 60 GHz band.

[0062] Each AP 110 may provide data connectivity to STAs 112 connected to a particular AP 110. As illustrated, APs 110 may be connected to a data network 130. In this way, APs 110 may also provide data connectivity between STAs 112 and other entities, e.g., to one or more servers, service providers, data sources, data sinks, user terminals, or the like. Accordingly, the radio link established between a given STA 112 and its serving AP 110 may be sued for providing various kinds of services to STA 112, e.g., a voice service, a multimedia service, or other data service. Such services may be based on applications that are executed on STA 112 and / or on a device linked to STA 112. By way of example, Fig. 8 illustrates an application service platform 132 provided in data network 130. The application(s) executed on STA 112 and / or on one or more other devices linked to STA 112 may use the radio link for data communication with one or more other STA 112 and / or the application service platform 132, thereby enabling utilization of the corresponding service(s) at STA 112.

[0063] Fig. 9 shows a terminal device 200, which may be configured to operate in communication system 100 of Fig. 8 . The terminal device 200 may be referred to as a UE 200, operating in a cellular communication system, and / or as a station (STA) 200 or as a non-accesspoint station (non-AP STA) 200, like a STA 112 within the context of the communication system 100, in accordance with respective embodiments. Thus, it is noted that the terminal device may either operate as an AP STA when operating as a so called "Wi-Fi Hotspot" providing Wi-Fi service to other non-AP STAs and providing backhaul via the cellular communication system, wherein its operation is further discussed with reference to Fig. 10, or operating as a non-AP STA connecting via Wi-Fi services provided by another AP STA, as will be further discussed below. As used herein, a terminal device refers to a device capable, configured, arranged and / or operable to communicate wirelessly with network nodes and / or other UEs. Examples of a terminal device include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle, vehicle-mounted or vehicle embedded / integrated wireless device, etc. Other examples include any UE identified by the 3rdGeneration Partnership Project (3 GPP), including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and / or an enhanced MTC (eMTC) UE.

[0064] A terminal device 200 may support device-to-device (D2D) communication, for example by implementing a 3 GPP standard for sidelink communication, Dedicated Short- Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle-to-everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and / or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).

[0065] The terminal device 200 includes processing circuitry 202 that is operatively coupled via a bus 204 to an input / output interface 206, a power source 208, a memory 210, a communication interface 212, and / or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Fig. 9. The level of integration between the components may vary from one terminal device to another terminal device. Further, certain terminal devices may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

[0066] The processing circuitry 202 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 210. The processing circuitry 202 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, 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 processing circuitry 202 may include multiple central processing units (CPUs).

[0067] In the example, the input / output interface 206 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and / or output devices. Examples of an output device include 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. An input device may allow a user to capture information into the terminaldevice 200. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.

[0068] In some embodiments, the power source 208 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source 208 may further include power circuitry for delivering power from the power source 208 itself, and / or an external power source, to the various parts of the terminal device 200 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 208. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 208 to make the power suitable for the respective components of the terminal device 200 to which power is supplied.

[0069] The memory 210 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 210 includes one or more application programs 214, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 216. The memory 210 may store, for use by the UE 200, any of a variety of various operating systems or combinations of operating systems.

[0070] The memory 210 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD- DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMMSDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and / or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘ SIM card.’ The memory 210 may allow the terminal device 200 to access instructions, application programs and 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 as or in the memory 210, which may be or comprise a device-readable storage medium.

[0071] The processing circuitry 202 may be configured to communicate with an access network or other network using the communication interface 212. The communication interface 212 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 222. The communication interface 212 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another terminal device or a network node in an access network). Each transceiver may include a transmitter 218 and / or a receiver 220 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 218 and receiver 220 may be coupled to one or more antennas (e.g., antenna 222) and may share circuit components, software or firmware, or alternatively be implemented separately.

[0072] In the illustrated embodiment, communication functions of the communication interface 212 may include cellular communication, Wi-Fi communication (e.g., according to an IEEE 802.11 family standard), LPWAN communication, 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. Communications may be implemented in according to one or more communication protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol / internet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[0073] Regardless of the type of sensor, the terminal device 200may provide an output of data captured by its sensors, through its communication interface 212, via a wireless connection to a network node. Data captured by sensors of a terminal device 200can be communicated through a wireless connection to a network node via another terminal device 200. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[0074] As another example, the terminal device 200 comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the terminal device 200 may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input.

[0075] A terminal device 200, when in the form of an Internet of Things (loT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Nonlimiting examples of such an loT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door / window sensor, a flood / moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a headmounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an loT device comprises circuitry and / or software in dependence of the intended application of the loT device in addition to other components as described in relation to the terminal device 200 shown in Fig. 9.

[0076] As yet another specific example, in an loT scenario, a terminal device 200may represent a machine or other device that performs monitoring and / or measurements, and transmits the results of such monitoring and / or measurements to another the terminal device and / or a network node. The terminal device 200 may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the terminal device 200 may implement the 3 GPP NB-IoT standard. In other scenarios, the terminal device 200 may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and / or reporting on its operational status or other functions associated with its operation.

[0077] In practice, any number of terminal devices may be used together with respect to a single use case. For example, a first terminal device 200 might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed. The first and / or the second UE can also include more than one of the functionalities described above. For example, a terminal device 200 might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators.

[0078] Fig. 10 shows a network node 300 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and / or operable to communicate directly or indirectly with a UE and / or with other network nodes or equipment, in a telecommunication network. In accordance with respective embodiments, network node 300 may be configured to operate in communication system 100 of Fig. 8, like an AP 110 or a station 112. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs)), 0-RAN nodes or components of an 0-RAN node (e.g., 0-RU, 0-DU, O-CU).

[0079] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an 0-RAN access node)and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0080] Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell / multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and / or Minimization of Drive Tests (MDTs).

[0081] The network node 300 includes a processing circuitry 302, a memory 304, a communication interface 306, and a power source 308. The network node 300 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node 300 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeB s. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node 300 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 304 for different RATs) and some components may be reused (e.g., a same antenna 310 may be shared by different RATs). The network node 300 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 300, for example GSM, WCDMA, LTE, NR, Wi-Fi (e.g., according to an IEEE 802.11 family standard), Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 300.

[0082] The processing circuitry 302 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and / or encoded logicoperable to provide, either alone or in conjunction with other network node 300 components, such as the memory 304, to provide network node 300 functionality.

[0083] In some embodiments, the processing circuitry 302 includes a system on a chip (SOC). In some embodiments, the processing circuitry 302 includes one or more of radio frequency (RF) transceiver circuitry 312 and baseband processing circuitry 314. In some embodiments, the radio frequency (RF) transceiver circuitry 312 and the baseband processing circuitry 314 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 312 and baseband processing circuitry 314 may be on the same chip or set of chips, boards, or units.

[0084] The memory 304 may comprise any form of volatile or non-volatile computer- readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or any other volatile or non-volatile, non-transitory device-readable and / or computerexecutable memory devices that store information, data, and / or instructions that may be used by the processing circuitry 302. The memory 304 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and / or other instructions capable of being executed by the processing circuitry 302 and utilized by the network node 300. The memory 304 may be used to store any calculations made by the processing circuitry 302 and / or any data received via the communication interface 306. In some embodiments, the processing circuitry 302 and memory 304 is integrated.

[0085] The communication interface 306 is used in wired or wireless communication of signaling and / or data between a network node, access network, and / or UE. As illustrated, the communication interface 306 comprises port(s) / terminal(s) 316 to send and receive data, for example to and from a network over a wired connection. The communication interface 306 also includes radio front-end circuitry 318 that may be coupled to, or in certain embodiments a part of, the antenna 310. Radio front-end circuitry 318 comprises filters 320 and amplifiers 322. The radio front-end circuitry 318 may be connected to an antenna 310 and processing circuitry 302. The radio front-end circuitry may be configured to condition signals communicated between antenna 310 and processing circuitry 302. The radio front-end circuitry 318 may receive digital data that is to be sent out to other network nodes or UEs via a wirelessconnection. The radio front-end circuitry 318 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 320 and / or amplifiers 322. The radio signal may then be transmitted via the antenna 310. Similarly, when receiving data, the antenna 310 may collect radio signals which are then converted into digital data by the radio front-end circuitry 318. The digital data may be passed to the processing circuitry 302. In other embodiments, the communication interface may comprise different components and / or different combinations of components.

[0086] In certain alternative embodiments, the network node 300 does not include separate radio front-end circuitry 318, instead, the processing circuitry 302 includes radio front-end circuitry and is connected to the antenna 310. Similarly, in some embodiments, all or some of the RF transceiver circuitry 312 is part of the communication interface 306. In still other embodiments, the communication interface 306 includes one or more ports or terminals 316, the radio front-end circuitry 318, and the RF transceiver circuitry 312, as part of a radio unit (not shown), and the communication interface 306 communicates with the baseband processing circuitry 314, which is part of a digital unit (not shown).

[0087] The antenna 310 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. The antenna 310 may be coupled to the radio front-end circuitry 318 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, the antenna 310 is separate from the network node 300 and connectable to the network node 300 through an interface or port.

[0088] The antenna 310, communication interface 306, and / or the processing circuitry 302 may be configured to perform any receiving operations and / or certain obtaining operations described herein as being performed by the network node. Any information, data and / or signals may be received from a UE, another network node and / or any other network equipment. Similarly, the antenna 310, the communication interface 306, and / or the processing circuitry 302 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and / or signals may be transmitted to a UE, another network node and / or any other network equipment.

[0089] The power source 308 provides power to the various components of network node 300 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 308 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 300 with power for performing the functionality described herein. For example, the network node 300 may beconnectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 308. As a further example, the power source 308 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

[0090] Embodiments of the network node 300 may include additional components beyond those shown in Fig. 10 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and / or any functionality necessary to support the subject matter described herein. For example, the network node 300 may include user interface equipment to allow input of information into the network node 300 and to allow output of information from the network node 300. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 300.

[0091] Fig. 11 schematically illustrates a signal generator 400 arranged to implement the above-described approach. The signal generator is provided with the OOK sequence to be transmitted and provides a multi-carrier signal with frequency offsets between OOK symbols as described above. The multi-carrier signal is provided to communication interfaces 212, 306 as of Figs 9 and 10, and in particular to front-end circuitry 318 as of Fig. 10. The signal generator 400 may be implemented in the communication interfaces 212, 306 as of Figs 9 and 10, or in the processing circuitry 302 as of Fig. 10. For example, the signal generator 400 may be integrated with transmitter 218 as of Fig. 9 or RF transceiver circuitry 312 of Fig. 10.

[0092] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and / or software needed to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and / or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devicesmay comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and / or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

[0093] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer- readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer- readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and / or by end users and a wireless network generally.

Claims

CLAIMS1. A method of generating an On-Off Keying, OOK, signal by a multi-carrier generator where the carriers among the multiple carriers are orthogonal, the method comprising for a first OOK symbol: assigning (10) a power level for active carriers; and forming (20) the first OOK symbol from the assigned power level and a first frequency offset from frequencies of the active carriers; and for a second OOK symbol: assigning (30) the power level for active carriers; and forming (40) the second OOK symbol from the assigned power level and a second frequency offset from the frequencies of the active carriers, where the second frequency offset is different than the first frequency offset.

2. The method of claim 1, the method further comprising, for a third OOK symbol: assigning (50) the power level for active carriers; and forming (60) the third OOK symbol from the assigned power level and a third frequency offset from the frequencies of the active carriers, where the third frequency offset is different than the first and second frequency offset.

3. The method of claim 1 or 2, wherein the multi-carrier generator is an Inverse Fast Fourier Transformer, IFFT, the multiple carriers correspond to a size of the IFFT, and the active carriers correspond to points of the IFFT to produce OOK symbols of desired length.

4. The method of claim 3, wherein the frequency offsets differ by a carrier spacing divided by N, where N is the size of the IFFT used for OOK generation.

5. The method of claim 4, where subsequent symbols following the first, second, or third symbols are formed using a first, second, or third frequency offset, respectively, in a periodic pattern with a periodicity of N.

6. The method of any one of claims 1 to 5, wherein the frequency offsets are applied by multiplying the respective active carrier with a sinusoid with a frequency corresponding to the respective frequency offset.

7. The method of claim 6, comprising adding a cyclic prefix to respective carrier before multiplying with the respective sinusoid.

8. The method of any one of claims 1 to 7, comprising randomizing ON signals of the OOK symbol with symbols of a pseudo-random sequence, respectively.

9. A signal generator (400) arranged to perform the method of any one of claims 1 to 8.

10. A transmitter (218, 312) comprising a signal generator according to claim 9 and wireless transmitter circuitry (218, 318) arranged to transmit the OOK signal.

11. An access point (110A-D, 300) comprising transceiver (312) and processing circuitry (302) capable of operating a communication in a Basic Service Set, wherein the access point (110A- D, 300) further comprises a transmitter (218, 312) according to claim 10.

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