WO2018232582A1

WO2018232582A1 - Waveform coding symbol

Info

Publication number: WO2018232582A1
Application number: PCT/CN2017/089122
Authority: WO
Inventors: Jung Hoon Suh; Jia Jia; Osama Aboul-Magd
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2017-06-20
Filing date: 2017-06-20
Publication date: 2018-12-27

Abstract

A method of and system for coding and transmitting a data signal, comprising waveform coding successive on-off-keying (OOK) mapped data bits onto successive multicarrier modulated symbols in time domain to generate waveform coded symbols that each represent a data bit, the waveform coded symbols comprising: a first symbol waveform that represents a first data bit value as an first "OFF" duration followed by an "ON" duration followed by a second " OFF" duration, and a second symbol waveform that represents a second data bit value as an first "OFF" duration followed by a further portion that includes an "ON" duration and a second " OFF" duration, wherein the first symbol waveform and the second symbol waveform each have the same total duration, the sum of the first "OFF" duration and "ON" duration of the first symbol waveform being equal to the first "OFF" duration of the second symbol waveform. The waveform coded symbols are upconverted to a carrier frequency to provide a data signal.

Description

WAVEFORM CODING SYMBOL

The present application relates to methods and systems for communicating with waveform coded symbols.

BACKGROUND

In wireless communication, efficient use of the available power is one of the main goals of system design. Often, a wireless local area network (WLAN) device, such as in Internet of Things (IoT) applications, relies on a limited power supply (e.g., as supplied by rechargeable or non-rechargeable batteries) . Examples of such a device may include sensor devices located in remote fields measuring some physical phenomenon, e.g., water level or temperature or location； and wearable devices measuring some bodily function, e.g., pulse rate.

Such a device may be designed to operate on a low duty cycle (e.g., communicating with an access point (AP) only once per day) and thus it may not be appropriate for its WLAN receiver circuit to be always on. The limited power supply (e.g., battery) of the device may be quickly exhausted if not provided with an appropriate sleep mode for the WLAN receiver circuit and an appropriate wake-up mechanism. The wake-up mechanism may require communication of wake-up signals between an AP and a device. In some applications, it may be desirable to enable an AP to communicate wake-up signals with multiple devices simultaneously in a spectrum efficient manner.

Standards are currently being developed for low data rate signals that can be used to implement a wake-up mechanism, including for example IEEE802.11ba for Wake Up Radio (WUR) . There is a need for a symbol that can facilitate low power transmission and reception while mitigating against one or both of inter-symbol interference and intra-symbol interference.

SUMMARY

According to a first aspect is a method of coding and transmitting a data signal. The method includes waveform coding successive on-off-keying (OOK) mapped data bits onto successive multicarrier modulated symbols in time domain to generate waveform coded symbols that each represent a data bit. The waveform coded symbols includes a first symbol waveform and a second symbol waveform. The first symbol waveform represents a first data bit value as an first “OFF” duration followed by an “ON” duration followed by a second ” OFF” duration. The second symbol waveform represents a second data bit value as an first “OFF” duration followed by a further portion that includes an “ON” duration and a second ” OFF” duration. The first symbol waveform and the second symbol waveform each have the same total duration, the sum of the first “OFF” duration and “ON” duration of the first symbol waveform being equal to the first “OFF” duration of the second symbol waveform. The method also includes up-converting the waveform coded symbols to a carrier frequency to provide a data signal； and transmitting the data signal over a wireless channel.

In a first embodiment of the method, the “ON” duration precedes the second “OFF” duration in the second symbol waveform, the sum of the “ON” duration and the second “OFF” duration of the second symbol waveform being equal to the second “OFF” duration of the first symbol waveform. In some examples, the “ON” duration of the second symbol waveform is shorter than the “ON” duration of the first symbol waveform, and in some examples a total energy of the “ON” duration of the second symbol waveform is substantially equal to a total energy of the “ON” duration of the first symbol waveform.. In some examples, the method includes amplifying each of the first and second symbol waveforms by a factor that is proportional to a ratio of the total duration of the symbol waveform to the “ON” duration of the symbol waveform. In some examples, the total duration of each of the first symbol waveform and the second symbol waveform is T_tot＝T_gi+T_u； the first “OFF” duration of the first symbol waveform is T_gi, the “ON” duration first symbol waveform is T_u/2, and the second ” OFF” duration of the first symbol waveform is Tu/2； and the first “OFF” duration of the second symbol waveform is T_gi +T_u/2, the “ON” duration of the second symbol waveform is T_u/2-T_gi, and the second “OFF” duration of the second symbol waveform is T_gi. In a specific example, T_tot＝ 4μs, T_gi＝ 0.8μs and T_u＝ 3.2 μs. In another specific example, T_tot＝ 3.6μs, T_gi＝ 0.4μs and T_u＝ 3.2 μs.

In an alternative example of the method the second “OFF” duration precedes the “ON” duration in the second symbol waveform, the “ON” durations of the first and second symbol waveforms being equal in duration. In some examples, The total duration of each of the first symbol waveform and the second symbol waveform is T_tot＝T_gi+T_u, the first “OFF” duration of the first symbol waveform is T_gi, the “ON” duration of the first symbol waveform is T_u/2-T_gi/2, and the second ” OFF” duration of the first symbol waveform is T_u/2+T_gi/2； and the first “OFF” duration of the second symbol waveform is T_gi and is immediately followed by the second “OFF” duration of the second symbol waveform having a duration of T_u/2+T_gi/2, and the “ON” duration of the second symbol waveform is T_u/2-T_gi/2. In a specific example, T_tot＝ 4μs, T_gi＝ 0.8μs and T_u＝ 3.2 μs.

In various example embodiments, the successive multicarrier modulated symbols each comprise an identical OFDM waveforms generated from a 64 point IFFT and have a subcarrier spacing of 312.5 KHz.

In some examples, the first symbol waveform represents a data bit ” 1” value and the second symbol waveform represents a data bit “0” value. In some examples, the first symbol waveform represents a data bit ” 0” value and the second symbol waveform represents a data bit “1” value.

According to a further aspect is a transmitting device for generating and transmitting the data signal that is provided according to the above methods.

According to another example aspect is a a method of coding and transmitting a data signal, comprising waveform coding successive on-off-keying (OOK) mapped data bits onto successive multicarrier modulated symbols in time domain to generate waveform coded symbols that each represent a data bit, the waveform coded symbols comprising a first symbol waveform and a second symbol waveform. The first symbol waveform represents a first data bit value as an “ON” duration followed by an “OFF” duration, and the second symbol waveform that represents a second data bit value as an “OFF” duration followed an “ON” duration. The method includes amplifying each of the first and second symbol waveforms by a factor that is proportional to a ratio of a total duration of the symbol waveform to the “ON” duration of the symbol waveform, up-converting the waveform coded symbols to a carrier frequency to provide a data signal, and transmitting the data signal over a wireless channel.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made, by way of example, to the accompanying drawings which show example embodiments of the present application, and in which:

FIG. 1 is a block diagram illustrating communications between an AP and an example station having a Wake Up Radio circuit；

FIG. 2 illustrates a frame format for an example wake-up radio data unit；

FIG. 3 is a block diagram illustrating a wake-up frame encoding system according to an example embodiment；

FIG. 4 shows frequency domain and time domain representations of example waveforms used in the system of FIG. 3；

FIG. 5 shows time domain representations example waveforms, after guard interval insertion, used in the system of FIG. 3；

FIG. 6 is a block diagram illustrating a wake-up frame decoding receiver circuit；

FIG. 7 shows frequency domain and time domain representations of example waveforms used in the system of FIG. 3, according to a further example embodiment；

FIG. 8 shows frequency domain and time domain representations of example waveforms used in the system of FIG. 3, according to a further example embodiment； and

FIG. 9 shows frequency domain and time domain representations of example waveforms used in the system of FIG. 3, according to a further example embodiment.

Similar reference numerals may have been used in different figures to denote similar components.

DETAILED DESCRIPTION

A user device or station such as a machine type device or sensor device that is intended to operate in a wireless network such as a wireless local area network (WLAN) may have a separate low-power Wake Up Radio (WUR) circuit in addition to a higher power WLAN transceiver circuit. A WUR circuit is generally a low-power receiver circuit designed for receiving and detecting a wake-up signal, which may for example be a low data rate signal. In some examples the WUR circuit may be a simplified version of the main WLAN transceiver circuit and may be implemented on integrated circuit (IC) or chip. The WUR circuit communicates with the WLAN transceiver circuit, or other equivalent circuit, of the device, so the WLAN transceiver circuit may sleep and conserve power until the WUR circuit wakes up the WLAN transceiver circuit. The WUR circuit wakes up the WLAN transceiver circuit, or other equivalent circuit, when the WUR circuit detects a wake-up signal from an access point AP (typically, an AP associated with the WLAN device) .

In this regard, FIG. 1 is a schematic diagram illustrating an example AP 102 and an example station 104 associated with the AP 102. In example embodiments the station 104 is a low duty cycle WLAN device or other wireless device. The example station 104 includes transmitter/receiver components 105 that include a main radio WLAN transceiver circuit 106 (e.g., a Wi-Fi transceiver) and a WUR circuit 108. In example embodiments, the WUR circuit 108 is a simple low power receiver that does not have a transmitter and functions to wake up the WLAN transceiver circuit 106 when needed. In some example embodiments, WUR circuit 108 can access components of WLAN transceiver circuit 106 to limit component duplication between the two circuits.

The AP 102 includes transceiver/receiver components 110 that can include a WUR encoder 112 for generating wake-up signals and a main radio circuit 114 for WLAN communications. In example embodiments, WUR encoder 112 can access and use components of the main radio circuit 114 to limit duplication of components in the two circuits.

Although aspects and features of the waveform coding described herein can be applied to different types of data signals, example embodiments will be provided in the context of low data rate signals such as wake-up signals. FIG. 1 illustrates a set of example signals that may be communicated for waking up a sleeping WLAN receiver circuit 106. The AP 102 may send a wake-up signal 152, carrying a Wake-Up-Radio (WUR) data unit 200 (described further below) to the station 104. The WUR data unit 200 is detected by the WUR circuit 108, and the WUR circuit 108 sends an internal wake-up signal 154 to the WLAN receiver circuit 106, waking up the WLAN transceiver circuit 106 if the WLAN receiver circuit 106 is in sleep mode. The WLAN transceiver circuit 106 then sends an ACK signal 156 back to the AP 102. Appropriate information exchange 158 between the AP 102 and the station 104 (via the WLAN transceiver circuit 106) may then take place. After the information exchange 158 is finished, the WLAN transceiver circuit 106 may return to the sleep state.

Although FIG. 1 shows wakeup signal 152 being communicated to a WUR circuit 108 that is associated with a WLAN transceiver circuit 106, the processes and systems described in the present disclosure may be applicable to other circuits, including other wireless receiver circuits, which may benefit from a wake-up mechanism or low data rate signal.

An example frame format for a WUR data unit 200 is shown in FIG. 2. The heights of the various blocks shown in FIG. 2 illustrate the relative bandwidths (BWs) of each portion. In the example of FIG. 2, the WUR data unit 200 includes a legacy preamble 210 pre-pended to a WUR frame 250. Legacy preamble 210 is included to silence legacy devices within the network and may be omitted in some examples where legacy equipment is not anticipated to operate. In applications where legacy preamble 210 is omitted, WUR Data Unit 200 will be identical to WUR frame 250. In example embodiments, legacy preamble 210 occupies a channel bandwidth of 20MHz, and WUR frame 250 occupies a bandwidth BW of 4.1MHz.

WUR frame 250 includes information that can be specific for a respective station 104 and can include the following fields: WUR -Reference Signal field 252； WUR signal (SIG) field 254； MAC header 262； frame body 264； and frame check sequence (FCS) 266. In an example embodiment WUR -Reference Signal field 252 may include a wakeup signal preamble, for example a pseudo noise (PN) sequence. The WUR signal (SIG) field 254 may include a control signal. The MAC header 262 may include a receiver address. The MAC header 262, frame body 264 and FCS 266 may together be referred to as the payload of the WUR frame 250. In some examples, WUR fames 250 may omit one or more of the frame fields identified in FIG. 2, and/or may include additional fields.

The WUR-Reference Signal 252 is provided for packet detection and synchronization. In some examples, WUR-Reference signal 252 may include a short training field (STF) that can be used by the WUR circuit 108 in the respective station 104 to detect the WUR frame 250 as distinct from other frames and allow the WUR circuit 108 to synchronize to the WUR frame 250. In some examples, WUR-Reference Signal 252 may include a sequence that can be correlated at the WUR circuit 108 to facilitate frame synchronization.

In example embodiments, the WUR circuit 108 of station 104 is implemented as a simple low power consuming receiver circuit, and accordingly WUR frame 250 is designed to enable efficient and accurate low power decoding at WUR circuit 108. In this regard, time-domain waveform coding (WFC) is used for parts of the WUR frame 250 that follow the WUR Reference Signal 252, shown in Figure 2 as WFC Coded Portion 268. In some example embodiments, filtering may be applied at the WUR circuit 108 station 104 to isolate the WUR Frame 205 for processing. Typically, increasing the filter coefficient (e.g. number of taps) at a filter increases the accuracy of the filtering, however it also increases cost and complexity of the filter. Furthermore, simulations have indicated that in some examples of a WFC signal, the greater the number of taps used in a filter at the WUR circuit 108 the greater the chance of inter-symbol interference. Accordingly, example embodiments are described herein that may provide a waveform coded symbol that can be decoded at a WUR circuit that has a filter with a filter coefficient that optimizes the trade-offs between inter-symbol interference (ISI) , intra-symbol interference and power consumption.

Figure 3 is a basic system block diagram illustrating a WUR system that employs waveform coding. Figure 3 shows the process flow applied at AP transceiver 110 to generate WUR frame 250. In example embodiments, each of the

blocks

300, 304, 306, and 308 represents an operation or function that may be implemented as a module or element of the WUR encoder 112 of the AP transceiver 110. In at least some examples, blocks 301 and 310 represent an operation or function that may be implemented as a module or element of the main radio 114 of the AP transceiver 110.

In the example of Figure 3, source data is provided for station 104 in the form of binary on-off keying (OOK) mapped source data 280. In example embodiments, the source data 280 includes data bits for the WFC coded portion 268 of the WUR frame 250.

In some examples, source data 280 is segmented into groups of K bits for processing. Forward error correction (FEC) encoding is applied at an FEC encoding operation 300 to encode K-bit segments as J-bit codewords. FEC encoding may be omitted in some embodiments. The encoded source data bits are then provided to a waveform coding operation 306, where each bit is encoded as a respective symbol waveform.

In this regard, as shown in Fig. 3, the WUR encoder 112 includes a waveform source 304 that provides successive, identical symbol waveforms 410 to the waveform coding operation 306 for encoding. As shown in Figure 4, each symbol waveform 410 has a pre-defined energy (E_u) within a pre-defined bandwidth (BW) , and a predefined symbol duration (T_u) that includes a predefined number of samples (N) . In example embodiments, symbol waveform 410 is the time domain version of a multi-carrier waveform 402 derived from subcarriers S_-6 to S₆ generated by a 64 point IFFT. In the presently described example, waveform source 304 includes memory 305 that stores a master copy of symbol waveform 410.

In example embodiments, multi-carrier waveform 402 is an Orthogonal Frequency Division Multiplex (OFDM) symbol generated by an OFDM waveform generator 301 that includes a 64 point inverse fast Fourier transform (IFFT) operation. Multi-carrier waveform 402 uses a sub-set of 13 subcarriers (S_- ₆ to S₆ ) of the 64 subcarriers, and has a corresponding bandwidth BW. Although different tone configurations are possible, in the illustrated example of Fig. 4 multi-carrier waveform 402 is generated with the tone configuration as illustrated, which is based on the corresponding tones that are occupied in the conventional OFDM 802.11 Long Training Sequence (LTS) symbol. In particular, central subcarrier S₀ in the central group of 13 subcarriers S_-6 to S₆ is a null or zero and the remaining 12 subcarriers in the central group are assigned values as follows: subcarriers S_-6, S_-4, S_-3, S_-2, S_-1, S₁, S₄, and S₅ are set to plus one (+1) , and subcarriers S_-5, S₂, S₃, and S₆ are each set to negative one (-1) . The remaining subcarriers S_-32 to S_-7 and S₇ to S₃₁ are each set to 0.

In the illustrated example, multi-carrier waveform 402 is a conventional 802.11 OFDM symbol having the following numerology parameters: Number of subcarriers ＝64, with number of used subcarriers SC_U＝13 (including subcarriers S_-6 to S₆, with S₀ used for a null) ； useful symbol duration T_u＝3.2μs； and subcarrier spacing SS ＝ 312.5KHz. The bandwidth BW-1 of symbol 402-1 is 13 X 312.5Khz ≈ 4.1MHz. Waveform 410 in Figure 4 represents a time domain version of OFDM symbol 402. In example embodiments, OFDM time domain waveform 410 is generated using the standard 802.11 sampling rate of 20MHz, such that OFDM waveform 410 includes N＝64 samples.

In example embodiments the operations performed by OFDM symbol generator 301 to provide symbol waveform 410 are done at a configuration time prior to WUR frame 250 processing and transmission, with waveform source 304 providing successive copies of the pre-stored symbol waveform 410 at the time of WUR frame 250 generation by AP Tx/Rx 110. This eliminates the requirement for an IFFT operation for each symbol waveform used for WUR frame 250, and also allows the OFDM waveform generator 301 of the main radio 114 to be used to generate the master copy of basic multicarrier waveform 410. In at least some example embodiments, OFDM waveform generator 301 is configurable and can be used to generate symbol waveforms that have different numerology parameters than those stated above, such that the stored waveform 410 can be changed if required.

In the example of Figure 3, waveform coding operation 306 is used to code FEC encoded OOK source data bits 280 onto successive time-domain symbol waveforms 410 at a ratio of 1 data bit to 1 symbol waveform. In an example embodiment, the waveform coding that is applied at operation 306 is a modified form of Manchester coding, which is also known as phase encoding (PE) . Manchester coding is a line code in which the encoding of each data bit results in a symbol having a waveform that is either low then high, or high then low, of equal time. Table 1 illustrates an example of Manchester encoding in which a symbol waveform is divided into two sub-symbols (SUB₁, SUB₂) of equal duration, where an “OFF” sub-symbol includes zero or substantially low energy, and an “ON” sub-symbol includes a higher, non-zero energy level that exceeds the energy of the “OFF” sub-symbol by a predetermined threshold. In this disclosure the terms “OFF” and “blank energy” mean a duration within a symbol that has zero or substantially zero energy.

Table 1: Waveform encoding of OOK data bits:

Although a data “1” is shown in the above table and described in example embodiments as an “ON” sub-symbol followed by an “OFF” sub-symbol, and a data “0” as an “OFF” sub-symbol followed by an “ON” sub-symbol, it will be appreciated that the sub-symbol order described herein can be reversed for

data bits

0 and 1 in alternative configurations.

In an example embodiment, as shown in Figure 4, the modified Manchester coding applied in time domain at waveform coding operation 306 to basic OFDM waveform 410 results in waveform coded (WFC) symbols 520. Each source data bit “1” is coded as a data “1” waveform 520-1 and each data bit “0” is coded as data “0” waveform 520-0.

In an example embodiment, waveform coding operation 306 uses the standard 802.11 sampling rate of 20MHz. As can be seen in Figure 4, waveform coding operation 306 generates a data bit “1” waveform 520-1 by using the first N/2 samples of multi-carrier waveform 410 for the N/2 samples of sub-symbol SUB₁, and then forcing or setting the last N/2 samples waveform 410 used for the trailing sub-symbol SUB₂ to blank energy. In this regard, data “1” waveform 520-1 uses conventional Manchester coding in that the “ON” duration and the “OFF” duration of the symbol waveform 520-1 are of equal duration (T_u/2) .

In contrast, waveform coding operation 306 generates a data bit “0” waveform 520-0 by forcing or setting the first N/2 samples of waveform 410 used for the leading sub-symbol SUB₁ to blank energy. The trailing sub-symbol SUB₂ is broken into two durations, namely a first duration of T_u/2-T_gi (corresponding to N/2-M samples) and a second duration of T_gi (corresponding to M samples) . N/2-M samples from the duration T_u/2 to T_u/2-T_gi of waveform 410 are used for the first duration of sub-symbol SUB₂, and the next M samples are then forced to or set to blank energy for the final duration (T_gi) of sub-symbol SUB₁. It will be appreciated that the coding used for data “0” waveform 520-0 is modified from the conventional Manchester coding procedure because the total “OFF” duration in waveform 520-0 exceeds the “ON” duration. As will be described in greater detail below, the trailing zero-energy M-sample region in the data “0” waveform 520-0 provides a guard interval (gi) duration (T_gi) to mitigate against inter-symbol interference during filtering at a downstream receiver.

As shown in FIG. 3, the “1” and “0” WFC symbols 520 produced by the waveform coding operation 306 are subjected to a power boosting amplification operation 308, which is described in greater detail below. The symbol waveforms resulting from waveform coding and amplification operations 306/308 are then subjected to a GI insertion operation 310. In at least some example embodiments, GI insertion operation 310 is performed using OFDM symbol generation components of the main radio circuit 114. As noted above, the base symbol waveform 410 is based on a conventional IEEE 802.11 OFDM waveform having a useful symbol duration T_u. A typical 802.11 symbol generator is configured to prepend a guard interval duration (T_gi) to the front of each useful symbol duration T_u by adding a cyclic prefix that is a copy of the last M samples of the useful symbol duration T_u. In many typical applications, M corresponds to 1/4 of the useful symbol duration T_u, however M can also have different values, and may, for example, alternatively correspond to 1/8 of the useful symbol duration T_u.

Figure 5 illustrates WFC symbols 522 after guard insertion operation 310 that correspond to the WFC symbols 520 with prepended guard intervals. With respect to the data “1” waveform 522-1, the final M samples of data “1” waveform 520-1 (which are all zero energy samples) , are copied and prepended to the front of the waveform to provide resulting data “1” waveform 522-1. Relative to the pre-guard interval waveform 520-1, the duration of post guard interval insertion data “1” waveform 522-1 is increased from T_u to T_tot＝T_u+T_gi. In an alternative embodiment, zero energy samples can be prepended to the front of the waveform without first copying them from the final samples of the waveform.

Similarly, for the data “0” waveform 522-0, the final M samples of data “0” waveform 520-0 (which were all zero energy samples as a result of the guard interval process done during waveform coding operation 306) , are copied and prepended to create the post guard interval insertion data “0” waveform 522-0. In an alternative embodiment, zero energy samples can be prepended to the front of the waveform without first copying them from the final samples of the waveform.

As can be seen from FIG. 5, the data “1” waveform 522-1 has a total duration of T_tot. A data “1” is represented by a symbol waveform that is made up of a first “OFF” duration of T_gi, followed by an “ON” duration of T_u/2, followed by an “OFF” duration of T_u/2. The data “0” waveform 522-0 also has a total duration of T_tot, but a data “0” is represented by a symbol waveform that is made up of: a first “OFF” duration of T_gi + T_u/2, followed by an “ON” duration of T_u/2-T_gi, followed by an “OFF” duration of T_gi.

It will be noted from FIG. 5 that the closest that two “ON” durations may occur in successive symbols is when a data “1” waveform 522-1 follows a data “0” waveform 522-0. Thus, the effect of including a zero-energy guard interval duration T_gi at the end of the data “0” waveform 522-0 and a zero-energy guard interval duration T_gi at the beginning of data “1” waveform 522-1 is that the minimum duration between the “ON” portion of successive symbols 522 at transmission will be 2*T_gi. This “double guard interval” can mitigate against ISI in a receiving WUR circuit’s filter.

It will also be noted from FIG. 5 that in each of waveforms 522-1, 522-0 the total “ON” duration is less than the total “OFF” duration, with the result that waveforms 522-1, 522-0 each have substantially less energy than a conventional OFDM symbol could otherwise have. In order to improve performance, in at least some examples power amplification is applied to the “ON” durations of the data “1” and data “0” waveforms to compensate for the zero energy durations. In this regard, in example embodiments, power amplification operation 308 is used to provide a power boost that is proportional to the total symbol duration divided by the total “ON” duration. For each data “1” waveform 522-1 the ratio of symbol duration to “ON” duration is T_tot/ (T_u/2) , and for each data “0” waveform 522-1 the ratio of symbol duration to “ON” duration is T_tot/ (T_u/2-T_gi) . Thus, in an example embodiment, power amplification operation 308 amplifies the power of the “ON” duration of data-1 waveform 520-1 proportional to T_tot/ (T_u/2) . In particular, each of the in-phase (i) and quadrature (q) components of the data “1” waveform 520-1 are amplified by a factor of √ (T_tot/ (T_u/2) ) . Power amplification operation 308 amplifies the power of the “ON” duration of data-0 waveform 520-0 proportional to T_tot/ (T_u/2-T_gi) . In particular, each of the in-phase (i) and quadrature (q) components of the data “0” waveform 520-1 is amplified by a factor of √ (T_tot/ (T_u/2-T_gi) ) .

In addition to increasing the energy of the both of the data “0” and data “1” waveforms, amplification operation 308 also has the effect of equalizing the total energy E0 of the data “0” waveform 520-0 to be about equal to the total energy E1 of the data “1” waveform 520-1. As a result of the shorter duration of the “ON” duration of the data “0” waveform 520-0 relative to the “ON” duration of the data “1” waveform 520-1, the total energy E1 of the data “1” waveform 520-1 will, in the absence of any equalization action, be greater than that of the total energy E0 of the data “0” waveform 502-0. In example embodiments, the downstream receiver WUR circuit 108 relies on relatively simple, low power circuitry to detect the energy differential between the first and second sub-symbols SUB₁ and SUB₂ of received symbol waveforms to differentiate between a data “1” and a data “0” . Accordingly, a relative power differential between the “ON” regions of data “1” waveform 520-1 and data “0” waveform 520-0 can adversely affect receiver performance. Thus, in example embodiments amplification operation 308 boosts the energy of data “0” waveform 520-0 to be about equal to that of the total energy E1 of data “1” waveform 520-1, thereby compensating for the energy of the trailing M samples of the “0” waveform that were forced to zero during waveform coding operation 306 to provide the trailing guard interval duration T_gi. In Figures 4 and 5, the higher amplitude of the “ON” region (E0) of the data “0” waveform 520-0 relative to the longer duration, but lower amplitude “ON” region (E1) of data “1” waveform 520-1, illustrates the extra power boost provided to the data “0” waveform 520-0.

Although power boosting amplification operation 308 is shown as occurring after waveform coding operation in FIG. 3, amplification could be applied on a sample by sample basis as part of the waveform coding operation 306, or alternatively after guard interval insertion operation 310. In some examples, power amplification to compensate for the shorter “ON” duration of the data “0” waveform relative that of the data “1” duration could be applied independently of a common power boost factor applied to both the data “0” waveform and data “1” waveforms.

Table 2 below provides an example set of parameters for WFC symbols 520/522.

Table 2: Example 1 -parameters for WFC symbols 520/522

Accordingly, in the example of table 2, the standard 802.11 sampling rate of 20MHz is applied by waveform coding operation 306. Data “1” waveform 522-1 has a duration of T_tot ＝ 4μs and 80 samples, and includes, in the following order: a guard interval of duration T_gi＝ 0.8μs that includes M＝16 blank samples； an “ON” duration of T_u/2 ＝ 1.6μs that includes N/2＝32 samples copied from symbol waveform 410； and an “OFF” duration T_u/2 ＝ 1.6μs that includes N/2＝32 blank samples in which energy has been forced to “0” . The data “1” symbol waveform 522-1 has negligible or zero energy except during the duration between T_gi and T_u/2+T_gi (namely 0.8 μs to 2.4μs) . The total energy of the data” 1” symbol is boosted by amplifying each of the in-phase and quadrature symbol components by a factor of √2.5.

Data “0” waveform 522-0 has a duration a duration of T_tot ＝ 4μs and 80 samples and includes, in the following order: a guard interval of duration T_gi＝ 0.8μs that includes M＝16 blank samples； a first sub-symbol SUB₁ of duration T_u/2 ＝ 1.6μs that includes N/2＝32 samples in which the subcarrier energy has been forced to “0” ； an “ON” duration of T_u/2-T_gi ＝ 8μs that includes N/-M2＝16 samples copied from symbol waveform 410； and a trailing guard interval of duration T_gi＝ 0.8μs that includes M＝16 blank samples. The data “0” symbol 520-2 has negligible or zero energy except during the duration between T_u/2+T_gi to T_tot-T_gi (namely 2.4μs to 3.2 μs) . The total energy of the data ” 0” symbol is boosted by amplifying each of the in-phase and quadrature symbol components by a factor of √5.

After amplification, the symbol energy E0 of data “0” waveform 522-0 is substantially equal to the symbol energy E1 of data “1” waveform 522-1. As can be seen from Figure 5, the data “1” waveform 522-1 represents a first data bit value as an first “OFF” duration followed by an “ON” duration followed by a second ” OFF” duration, and the data “0” wavefrom 522-0 represents a second data bit value as an first “OFF” duration followed by an “ON” duration and a second ” OFF” duration. The symbol waveforms 522-1, 522-0 each have the same total duration, the sum of the first “OFF” duration and “ON” duration of the data “1” symbol waveform 522-1 being equal to the first “OFF” duration of the data “0” symbol waveform 522-0. The sum of the “ON” duration and the second “OFF” duration of the data “0” symbol waveform 522-0 is equal to the second “OFF” duration of the data “1” symbol waveform 522-1. The “ON” duration of the data “0” symbol waveform 522-0 is shorter than the “ON” duration of the data “1” symbol waveform 522-1.

It will be appreciated that WFC symbols 522 having the characteristics stated in the previous paragraphs could be generated using methods, components and symbol numerology other than those described in respect of the system shown in Figure 3. For example, in some alternative embodiments copies of WFC symbols 522-0 and 522-1 can be pre-generated and stored in memory 305 at waveform source 304, with waveform coding operation 306 selecting the appropriate WFC symbol to output based on the OOK value of an OOK source data 280.

In the example of FIG. 3, at the conclusion of GI insertion operation 310, each set of K OOK source data bits 280 is represented at the as a series of J WFC symbols 522 that form WFC portion 268. WUR–REF Signal 252 is then prepended to the WFC portion 268 to complete WUR frame 250. In examples where legacy preamble 210 is included, the legacy preamble 210 is prepended to WUR frame 250 to form WUR data Unit 200, which is then upconverted at modulator 308 to a channel carrier frequency and transmitted through wireless network channel 410 as part of wake-up signal 152. In example embodiments the same transmit filter used for 802.11 is used to provide spectral filtering to ensure that the transmitted symbols, including any edge tones, fall within a 20MHz spectral mask.

Figure 6 shows a target station 104 and the decoding operations performed at a receiving WUR circuit 108 in respect of a WUR data unit 200 included in a wake-up signal 152 received through wireless channel 410. In some examples, each

processing block

310, 312, 314, 316, 318 and 320 shown as being performed at WUR circuit 108 represents an operation that may be implemented as a module or element that is part of one or more integrated circuits. As shown in Figure, the station includes a filter 312 tuned to the baseband bandwidth of WUR Frame 250. For example, a filter may be a low pass filter, which corresponds to a 0MHz center frequency with a 4 MHz bandwidth. In some examples the filter 312 is an 8-tap filter (filter coefficient ＝ 8) to optimize between inter-band interference rejection and ISI. In some examples the filter 312 is a 4-tap filter (filter coefficient ＝ 4) to optimize between inter-band interference rejection and ISI, but with a greater weighting to reduced power consumption. In some examples, filter 312 could have more or fewer taps, for example 2 taps or 16 taps, or could be omitted.

The processing of a received WUR data unit 200 at the WUR circuit 108 of station 104 will now be described in greater detail according to an example embodiment. The received WUR data unit 200 is received as part of wake-up signal 152 at WUR circuit 108 and down converted at modulator 310 to baseband. The baseband WUR data unit 200 is then filtered at filter 312 to restrict the signal to the bandwidth BW that corresponds to WUR frame 250. Synchronization operation 314 then processes the received WUR frame 250 to synchronize to the symbol boundaries of the WFC symbols 522 that are included in the recovered WFC portion 268 of the WUR frame 250. In this regard, in some example embodiments synchronization operation 314 relies on WUR –Reference Signal 252 in received WUR frame 250 to allow WUR circuit 108 to synchronize sample timing to the incoming symbol boundaries of individual recovered WFC symbols 522 that are included within recovered WFC coded portion 268R, enabling each of the recovered WFC symbols 522 to be sequentially processed by energy detection operation 316 and hard decision operation 318. In example embodiments, prior to or as an initial step in the power detection operation 316, the prepended guard interval duration is removed from the WFC symbol 522 being processed, leaving a received WFC symbol 520. The power detection operation 316 then measures the power distribution in each of first and second sub-symbols SUB₁ and SUB₂. By way of example, in one embodiment, power detection operation 316 is configured to sample the received WFC symbol 520 at the same frequency used at waveform coding operation 306 (for example the conventional 20MHz of 802.11) and process the WFC symbol 520 as follows: the first M samples (corresponding to duration T_gi) are discarded； an average power distribution value is determined for the next N/2 samples (corresponding to a duration of T_u/2) which represent sub-symbol SUB₁； and a further average power distribution value then determined for the next N/2 samples (corresponding to a duration of T_u/2) which represent sub-symbol SUB₂. In the example of a 20MHz sampling rate and total symbol time of T_tot＝4 μs the discarded guard interval includes M＝16 samples, and first sub-symbol SUB₁ and second sub-symbol SUB₂ each include N/2＝ 32 samples.

Decision block 318 is configured to compare the average power distribution values between the first and second sub-symbols SUB₁ and SUB₂ and make a corresponding data “0” or “1” decision. In the illustrated example, if the magnitude of the average power distribution value is greater in the first sub-symbol SUB₁ than the second sub-symbol SUB₂, then the received WFC symbol 520 is decoded as a data “1” ； and if the average power magnitude value is greater in the second sub-symbol SUB₂ than the first sub-symbol SUB₁, then the received WFC symbol 520 is decoded as a data “0” . The successive data bits from decision operation 318 are assembled to provide recovered FEC OOK data, with FEC decoding operation 320 being applied to generate recovered OOK source data 280 that corresponds to original OOK source data 280. The recovered OOK source data 280 may, for example, contain information and instructions for internal wake-up signal 154 for the main WLAN transceiver circuit 106 of station 104.

In at least some examples, the symbol waveforms 522 shown in Figure 5 enable a WiFi enabled main radio 114 in an AP 102 (or Station 104) to be used to implement portions of WUR transmitter circuit with minimal modification.

The

symbol waveforms

520 and 522 shown in Figures 4 and 5 can have different parameters other than those set out in table 2 above. In this regard, table 3 below sets out another example set of parameters for WFC symbols 520/522.

Table 3: Example 2 -parameters for WFC symbols 520/522

Accordingly, in the example of table 3, the standard 802.11 sampling rate of 20MHz is applied by waveform coding operation 306. Data “1” waveform 522-1 has a duration of T_tot ＝ 3.6μs and 72 samples, and includes, in the following order: a guard interval of duration T_gi＝ 0.4μs that includes M＝8 blank samples； an “ON” duration of T_u/2 ＝ 1.6μs that includes N/2＝32 samples copied from symbol waveform 410； and an “OFF” duration T_u/2 ＝ 1.6μs that includes N/2＝32 blank samples in which energy has been forced to “0” . The data “1” symbol waveform 522-1 in the example of table 2 has negligible or zero energy except during the duration between T_gi and T_u/2+T_gi (namely 0.4 μs to 2.0μs) . The total energy E1 of the data ” 1” symbol is boosted by amplifying each of the in-phase and quadrature symbol components by a factor of √2.25.

In the example of table 3, Data “0” waveform 522-0 has a duration of T_tot ＝ 3.6μs and 72 samples and includes, in the following order: a guard interval of duration T_gi＝ 0.4μs that includes M＝8 blank samples； a first sub-symbol SUB₁ of duration T_u/2 ＝ 1.6μs that includes N/2＝32 samples in which the subcarrier energy has been forced to “0” ； an “ON” duration of T_u/2-T_gi ＝ 1.2μs that includes N/2-M＝24 samples copied from symbol waveform 410； and a trailing guard interval of duration T_gi＝ 0.4μs that includes M＝8 blank samples. The data “0” symbol 520-2 has negligible or zero energy except during the duration between T_u/2+T_gi to T_tot-T_gi (namely 2.0μs to 3.2 μs) . The total energy E0 of the data ” 0” symbol is boosted by amplifying each of the in-phase and quadrature symbol components by a factor of √3.

Figure 7 shows a further alternative example of a waveform design with WFC symbols 522A that may be used in place of the WFC symbols 522 in some example embodiments. In the example of Figure 7, a guard interval of duration T_gi (M samples) is prepended to OFDM waveform that is stored in memory 305, and waveform coding operation 306 is performed on the waveform 410A. As a result, the WFC waveforms 522A that are output from the waveform coding operation 306 already include a pre-pended guard interval and post waveform coding guard interval insertion operation 310 is not required.

A data “1” WFC symbol waveform 522A-1 and a data “0” WFC symbol waveform 522A-0 according to the alternative design of WFC symbols 522A is shown in FIG. 7. In one example, data “1” WFC symbol waveform 522A-1 is formed by: forcing the first M samples (duration T_gi) of waveform 410A to blank energy； copying the next N/2–M/2 samples (duration T_gi to T_u/2 -T_gi/2) of waveform 410A to provide an “ON” duration of T_u/2-T_gi/2； and forcing the next M/2 + N/2 samples (duration T_u/2 -T_gi/2 to T_tot) of waveform 410A to blank energy. Data “0” WFC symbol waveform 522A-0 is formed by: forcing the first M +N/2 + M/2 samples (duration T_u/2 + T_gi +T_gi/2) of waveform 410A to blank energy； and copying the next N/2-M/2 samples (duration T_u/2 +T_gi + T_gi/2 to T_tot ) of waveform 410A to provide an “ON” duration of T_u/2-T_gi/2.

It will be noted that in the example of Figure 7 the data “1” and data “0” waveforms 522A-1 and 522A-0 each have the same total “ON” duration, and accordingly the same power amplification factor can be applied to both the waveforms at amplification operation 308. In an example embodiment, the amplification factor is proportional to the ratio of the total symbol duration to the “ON” duration, and more particularly each if the in-phase and quadrature components of the waveforms 522A-1 and 522A-0 are subjected to an energy boosting power amplification factor of √ (T_tot/ (T_u/2-T_gi/2) ) .

Furthermore, in addition to the conventional Manchester coding of a symbol “OFF” duration that is equal in duration to a symbol “ON” duration, the waveforms 522A-1 and 522A-0 each include two guard interval durations, namely and initial guard interval duration of T_gi, and a second guard interval duration of T_gi that occurs in a middle of the symbol from (Tu/2+Tgi-Tgi/2) to (Tu/2+Tgi+Tgi/2) .

Table 4 below provides an example set of parameters for WFC symbols 522A.

Table 4: Parameters for WFC symbols 522A

In at least some example embodiments, at receiver WUR circuit 108, energy detection operation 316 is configured to ignore the first M samples and the middle M samples that correspond to the first and second guard interval durations in the received WFC symbols 522A.

FIG. 8 shows still a further alternative example of waveform design with WFC symbols 522B that may be used in place of the WFC symbols 522A in some example embodiments. As with the example of Figure 7, in the example of Figure 8, a guard interval of duration T_gi (M samples) is prepended to OFDM waveform that is stored in memory 305, and waveform coding operation 306 is performed on the resulting waveform 410A, and post waveform coding guard interval insertion operation 310 is not required.

A data “1” WFC symbol waveform 522B-1 and a data “0” WFC symbol waveform 522B-0 according to the alternative design of WFC symbols 522B is shown in FIG. 8. In one example, data “1” WFC symbol waveform 522B-1 is formed by: forcing the first M samples (duration T_gi) of waveform 410A to blank energy； copying the next N/2 samples (duration T_gi to T_u/2 +T_gi) of waveform 410A to provide an “ON” duration； and forcing the next N/2 samples (duration T_u/2 +T_gi to T_tot) of waveform 410A to blank energy. Data “0” WFC symbol waveform 522B-0 is formed by: forcing the first M +N/2 samples (duration T_u/2 + T_gi) of waveform 410A to blank energy； and copying the next N/2 samples (duration T_u/2 +T_gi to T_tot of waveform 410A to provide an “ON” duration.

It will be noted that in the example of Figure 8 the data “1” and data “0” waveforms 522B-1 and 522B-0 each have the same total “ON” duration, and accordingly the same power amplification factor can be applied to both the waveforms at amplification operation 308. In an example embodiment, the amplification factor is proportional to the ratio of the total symbol duration to the “ON” duration, and more particularly each if the in-phase and quadrature components of the waveforms 522B-1 and 522B-0 are subjected to an energy boosting power amplification factor of √ (T_tot/ (T_u/2) ) .

Table 5 below provides an example set of parameters for WFC symbols 522B.

Table 5: Parameters for WFC symbols 522B

In at least some example embodiments, at receiver WUR circuit 108, energy detection operation 316 is configured to ignore the first M samples that correspond to the leading guard interval duration in the received WFC symbols 522B.

FIG. 9 shows still a further alternative example of a waveform design with WFC symbols 522C that may be used in place of the

WFC symbols

522, 522A or 522B in some example embodiments. In the example of Figure 9, the OFDM waveform 410A that is stored in memory 305 has a total duration of T_tot and L samples, and post waveform coding guard interval insertion operation 310 is not required. OFDM waveform 410A may, for example, have been formed by prepending a cyclic prefix guard interval in time domain onto OFDM symbol 402, or alternatively OFDM symbol 402 may just be created with a duration of T_tot.

A data “1” WFC symbol waveform 522C-1 and a data “0” WFC symbol waveform 522C-0 according to the alternative design of WFC symbols 522C are shown in FIG. 9. In one example, data “1” WFC symbol waveform 522C-1 is formed by: copying the first L/2 samples (duration T_tot/2) of waveform 410A to provide an “ON” duration； and forcing the next L/2 samples (duration T_tot/2 to T_tot) of waveform 410A to blank energy. Data “0” WFC symbol waveform 522B-0 is formed by: forcing the first L/2 samples (duration T_tot/2) of waveform 410A to blank energy； and copying the next L/2 samples (duration T_tot/2 to T_tot of waveform 410A to provide an “ON” duration. In the example of Figure 9 the data “1” and data “0” waveforms 522C-1 and 522C-0 each have the same total “ON” duration equal to total “OFF” duration, namely T_tot/2, and the waveforms have no additional blank energy guard intervals. The same power amplification factor can be applied to both the waveforms at amplification operation 308. In an example embodiment, the amplification factor is proportional to the ratio of the total symbol duration to the “ON” duration, and more particularly each if the in-phase and quadrature components of the waveforms 522B-1 and 522B-0 are subjected to an energy boosting power amplification factor of √ (T_tot/2)

Table 6 below provides an example set of parameters for WFC symbols 522C.

Table 6: Parameters for WFC symbols 522C

The present disclosure may provide certain example algorithms and calculations for implementing examples of the disclosed methods and systems. However, the present disclosure is not bound by any particular algorithm or calculation.

Although the present disclosure may describe methods and processes with steps in a certain order, one or more steps of the methods and processes may be omitted or altered as appropriate. One or more steps may take place in an order other than that in which they are described, as appropriate.

Although the present disclosure may be described, at least in part, in terms of methods, a person of ordinary skill in the art will understand that the present disclosure is also directed to the various components for performing at least some of the aspects and features of the described methods, be it by way of hardware components, software or any combination of the two.

The present disclosure may be embodied in other specific forms without departing from the subject matter of the claims. The described example embodiments are to be considered in all respects as being only illustrative and not restrictive. Selected features from one or more of the above-described embodiments may be combined to create alternative embodiments not explicitly described, features suitable for such combinations being understood within the scope of this disclosure.

All values and sub-ranges within disclosed ranges are also disclosed. Also, although the systems, devices and processes disclosed and shown herein may comprise a specific number of elements/components, the systems, devices and assemblies could be modified to include additional or fewer of such elements/components. For example, although any of the elements/components disclosed may be referenced as being singular, the embodiments disclosed herein could be modified to include a plurality of such elements/components. The subject matter described herein intends to cover and embrace all suitable changes in technology.

Claims

A method of coding and transmitting a data signal, comprising:

waveform coding successive on-off-keying (OOK) mapped data bits onto successive multicarrier modulated symbols in time domain to generate waveform coded symbols that each represent a data bit, the waveform coded symbols comprising:

a first symbol waveform that represents a first data bit value as a first “OFF” duration followed by an “ON” duration followed by a second ” OFF” duration, and

a second symbol waveform that represents a second data bit value as an first “OFF” duration followed by a further portion that includes an “ON” duration and a second “OFF” duration, wherein the first symbol waveform and the second symbol waveform each have the same total duration, the sum of the first “OFF” duration and “ON” duration of the first symbol waveform being equal to the first “OFF” duration of the second symbol waveform；

up-converting the waveform coded symbols to a carrier frequency to provide a data signal； and

transmitting the data signal over a wireless channel.
The method of claim 1 wherein the “ON” duration precedes the second “OFF” duration in the second symbol waveform, the sum of the “ON” duration and the second “OFF” duration of the second symbol waveform being equal to the second “OFF” duration of the first symbol waveform.
The method of claim 2 where the “ON” duration of the second symbol waveform is shorter than the “ON” duration of the first symbol waveform.
The method of claim 3 wherein a total energy of the “ON” duration of the second symbol waveform is substantially equal to a total energy of the “ON” duration of the first symbol waveform.
The method of any one of claims 1 to 4 comprising amplifying each of the first and second symbol waveforms by a factor that is proportional to a ratio of the total duration of the symbol waveform to the “ON” duration of the symbol waveform.
The method of any one of claims 1 to 5 wherein:

the total duration of each of the first symbol waveform and the second symbol waveform is T_tot＝T_gi+T_u；

the initial “OFF” duration of the first symbol waveform is T_gi, the “ON” duration first symbol waveform is T_u/2, and the second ” OFF” duration of the first symbol waveform is Tu/2； and

the initial “OFF” duration of the second symbol waveform is T_gi +T_u/2, the “ON” duration of the second symbol waveform is T_u/2-T_gi, and the second “OFF” duration of the second symbol waveform is T_gi.
The method of claim 6 wherein T_tot＝ 4μs, T_gi＝ 0.8μs and T_u＝3.2 μs.
The method of claim 6 wherein T_tot＝ 3.6μs, T_gi＝ 0.4μs and T_u＝ 3.2 μs.
The method of claim 1 wherein the second “OFF” duration precedes the “ON” duration in the second symbol waveform, the “ON” durations of the first and second symbol waveforms being equal in duration.
The method of claim 9 wherein:

the total duration of each of the first symbol waveform and the second symbol waveform is T_tot＝T_gi+T_u；

the initial “OFF” duration of the first symbol waveform is T_gi, the “ON” duration of the first symbol waveform is T_u/2-T_gi/2, and the second ” OFF” duration of the first symbol waveform is T_u/2+T_gi/2； and

the initial “OFF” duration of the second symbol waveform is T_gi and is immediately followed by the second “OFF” duration of the second symbol waveform having a duration of T_u/2+T_gi/2, and the “ON” duration of the second symbol waveform is T_u/2-T_gi/2.
The method of claim 10 wherein T_tot＝ 4μs, T_gi＝ 0.8μs and T_u＝ 3.2 μs.
The method of any one of claims 9 to 11 comprising amplifying each of the first and second symbol waveforms by a factor that is proportional to a ratio of the total duration of the symbol waveform to the “ON” duration of the symbol waveform.
The method of any one of claims 1 to 12 wherein the successive multicarrier modulated symbols each comprise an identical OFDM waveforms generated from a 64 point IFFT and have a subcarrier spacing of 312.5 KHz.
The method of any one of claims 1 to 13 wherein the first symbol waveform represents a data bit ” 1” value and the second symbol waveform represents a data bit “0” value.
The method of any one of claims 1 to 13 wherein the first symbol waveform represents a data bit ” 0” value and the second symbol waveform represents a data bit “1” value.
A device for transmitting a data signal, comprising:

a waveform coding module configured to waveform code successive on-off-keying (OOK) mapped data bits onto successive multicarrier modulated symbols in time domain to generate waveform coded symbols that each represent a data bit, the waveform coded symbols comprising:

a first symbol waveform that represents a first data bit value as an initial “OFF” duration followed by an “ON” duration followed by a second ” OFF” duration, and

a second symbol waveform that represents a second data bit value as an first “OFF” duration followed by a further portion that includes an “ON” duration and a second ” OFF” duration, wherein the first symbol waveform and the second symbol waveform each have the same total duration, the sum of the first “OFF” duration and “ON” duration of the first symbol waveform being equal to the first “OFF” duration of the second symbol waveform；

a modulator configured to up-convert the waveform coded symbols to a carrier frequency to provide a data signal and transmit the data signal over a wireless channel.
The device of claim 16 wherein:

the total duration of each of the first symbol waveform and the second symbol waveform is T_tot＝T_gi+T_u；

the first “OFF” duration of the first symbol waveform is T_gi, the “ON” duration first symbol waveform is T_u/2, and the second ” OFF” duration of the first symbol waveform is Tu/2； and

the first “OFF” duration of the second symbol waveform is T_gi +T_u/2, the “ON” duration of the second symbol waveform is T_u/2-T_gi, and the second “OFF” duration of the second symbol waveform is T_gi.
The device of claim 17 wherein T_tot＝ 4μs, T_gi＝ 0.8μs and T_u＝ 3.2 μs.
The device of claim 17 wherein T_tot＝ 3.6μs, T_gi＝ 0.4μs and T_u＝ 3.2 μs.
The device of claim 16 wherein:

the total duration of each of the first symbol waveform and the second symbol waveform is T_tot＝T_gi+T_u；

the first “OFF” duration of the first symbol waveform is T_gi, the “ON” duration first symbol waveform is T_u/2, and the second ” OFF” duration of the first symbol waveform is T_u/2； and

the first “OFF” duration of the second symbol waveform is T_gi and is immediately followed by the second “OFF” duration of the second symbol waveform having a duration of T_gi, and the “ON” duration of the second symbol waveform is T_u/2.
The device of claim 20 wherein T_tot＝ 4μs, T_gi＝ 0.8μs and T_u＝ 3.2 μs.
A method of coding and transmitting a data signal, comprising:

waveform coding successive on-off-keying (OOK) mapped data bits onto successive multicarrier modulated symbols in time domain to generate waveform coded symbols that each represent a data bit, the waveform coded symbols comprising:

a first symbol waveform that represents a first data bit value as an “ON” duration followed by an “OFF” duration, and

a second symbol waveform that represents a second data bit value as an “OFF” duration followed an “ON” duration；

amplifying each of the first and second symbol waveforms by a factor that is proportional to a ratio of a total duration of the symbol waveform to the “ON” duration of the symbol waveform,

up-converting the waveform coded symbols to a carrier frequency to provide a data signal； and

transmitting the data signal over a wireless channel.
The method of any one of claims 1 to 15 and 22 wherein the data signal is a wake-up radio signal.