WO2025053904A1 - Wake-up radio using enhancements to burst position modulation - Google Patents

Abstract

Systems, devices, and methods of transmitting and receiving wakeup impulse sequences using enhanced burst position modulation are disclosed. In an exemplary aspect, a transmitter circuit is disclosed. In some embodiments, the transmitter circuit is configured to transmit a wakeup impulse sequence comprising a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, wherein the address comprises a plurality of address symbols that represent a receiver identification. In further aspects, in the enhanced burst position modulation, a time period allocated to a binary 0 and a time period allocated to a binary 1 within each symbol period are separated by a time gap. In further aspects, a receiver for receiving this wakeup impulse sequence is disclosed.

Description

Wake-Up Radio Using Enhancements to Burst Position Modulation

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional App. No. 63/631,758, entitled “Wake-Up Radio Using Enhancements to Burst Position Modulation” and filed on April 9, 2024, and U.S. Provisional App. No. 63/581,176, entitled “UWB Wakeup Radio using Enhanced Burst Position Modulation” and filed on September 7, 2023, both of which are incorporated by reference herein in their entireties.

[0002] This application is related to U.S. Patent Application Serial Number 17/883,048, filed August 8, 2022, which published as U.S. Patent Pub. No. 2023/0139079 and claims the benefit of U.S. Provisional App. No. 63/275,139, the disclosures of all of which are hereby incorporated herein by reference in their entireties.

[0003] This application is also related to U.S. Provisional App. No. 63/522,733 and U.S. Provisional App. No. 63/492,592, both of which are hereby incorporated herein by reference in their entireties.

TECHNICAL FIELD

[0004] The present disclosure relates generally to waking up a wireless communication device, such as an ultra-wideband (UWB) device, via a wakeup signal that uses enhancements to burst position modulation.

BACKGROUND

[0005] Ultra-wideband (UWB) is an Institute of Electrical and Electronic Engineers (IEEE) 802.15.4a/z standard technology optimized for secure micro-location-based applications. UWB based positioning service is enabled by transmitting one or more UWB pulses from a UWB transmitter (e.g., smartphone) to a UWB receiver (e.g., a sensor) and calculating the time it takes the UWB pulse(s) to travel between the transmitter and the receiver.

[0006] A UWB receiver is typically powered by embedded batteries. As such, many UWB receivers stay in power-saving mode (e.g., a sleep mode) much of the time to conserve energy and will wake up in response to detecting a wakeup signal. UWB receivers may employ a wakeup circuit that listens for a wakeup impulse sequence, while a main receiver circuit remains in sleep mode to conserve energy. In aiming for low-power operation, a wakeup sequence may be received in a low signal-to-noise operational environment. Thus, there remains a need to ways to improve performance for UWB communication devices that employ wakeup techniques.

SUMMARY

[0007] Embodiments of the present disclosure include systems, devices, and methods of transmitting and receiving wakeup impulse sequences using enhanced burst position modulation.

[0008] In an exemplary aspect, a transmitter circuit is disclosed. In some embodiments, the transmitter circuit is configured to transmit a wakeup impulse sequence comprising a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, wherein the address comprises a plurality of address symbols that represent a receiver identification. In further aspects, in the enhanced burst position modulation, a time period allocated to a binary 0 and a time period allocated to a binary 1 within each symbol period are separated by a time gap.

[0009] In another exemplary aspect, a method of operating a wireless communication device is disclosed. In some embodiments, the method includes transmitting a wakeup impulse sequence comprising a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, wherein the address comprises a plurality of address symbols that represent a receiver identification. In further aspects, in the enhanced burst position modulation, a time period allocated to a binary 0 and a time period allocated to a binary 1 within each symbol period are separated by a time gap.

[0010] In another exemplary aspect, non-transitory computer-readable medium having program code recorded thereon for operating a transmitter circuit is disclosed. In some embodiments, the program code includes code for transmitting a wakeup impulse sequence comprising a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, wherein the address comprises a plurality of address symbols that represent a receiver identification. In further aspects, in the enhanced burst position modulation, a time period allocated to a binary 0 and a time period allocated to a binary 1 within each symbol period are separated by a time gap.

[0011] In another exemplary aspect, a receiver circuit is disclosed. In some embodiments, the receiver circuit includes a main receiver circuit, and a wakeup receiver circuit. The wakeup receiver circuit may be configured to detect a wakeup impulse sequence, wherein the wakeup impulse sequence comprises a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, wherein the address comprises a plurality of address symbols that represent a receiver identification. The wakeup receiver circuit may further be configured to determine whether the wakeup impulse sequence is intended to wake up the main receiver circuit; and wake up the main receiver circuit in the receiver circuit in response to determining that the wakeup impulse sequence is intended to wake up the receiver circuit.

[0012] Additional aspects, features, and advantages of the present disclosure will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description, serve to explain the principles of the disclosure.

[0014] FIG. 1 is a schematic diagram of an exemplary wireless communication system, according to some aspects of the present disclosure.

[0015] FIG. 2 is a block diagram illustrating a general structure of the wakeup impulse sequence in FIG. 1, according to some aspects of the present disclosure.

[0016] FIG. 3 illustrates conventional burst position modulation (BPM), according to some aspects of the present disclosure.

[0017] FIG. 4 illustrates so-called “enhanced” BPM, according to some aspects of the present disclosure.

[0018] FIG. 5 is a schematic diagram providing an exemplary illustration of the receiver circuit in the wireless communication system of FIG. 1, according to some aspects of the present disclosure.

[0019] FIG. 6 is a schematic diagram providing an exemplary illustration of the wakeup signal detector circuit in the receiver circuit of FIG. 3, according to some aspects of the present disclosure.

[0020] FIG. 7 illustrates an output of a filter circuit for logical 0 versus logical 1 for various time gaps between these logical values using BPM (no time gap) and enhanced BPM (which uses a time gap), according to some aspects of the present disclosure.

[0021] FIGS. 8 A and 8B illustrate a wakeup receiver analog output for conventional BPM and enhanced BPM, according to some aspects of the present disclosure.

[0022] FIG. 9 illustrates an example symbol period, according to some aspects of the present disclosure. [0023] FIG. 10 illustrates a method of operating a receiver circuit, according to some aspects of the present disclosure.

DETAILED DESCRIPTION

[0024] For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It is nevertheless understood that no limitation to the scope of the disclosure is intended. Any alterations and further modifications to the described devices, systems, and methods, and any further application of the principles of the present disclosure are fully contemplated and included within the present disclosure as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and/or steps described with respect to one embodiment may be combined with the features, components, and/or steps described with respect to other embodiments of the present disclosure. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately.

[0025] When a wakeup signal, such as a wakeup impulse sequence, is detected, a main receiver circuit may be alerted to wake up to commence communication. An exemplary wakeup receiver circuit, main receiver circuit, and associated methods are presented in U.S. Patent Pub. No. 2023/0139079, entitled “Receiver Circuit for Detecting and Waking Up to a Wakeup Impulse Sequence,” which is incorporated herein by reference in its entirety. Some communication devices that use UWB wakeup procedures are known to use on-off keying (OOK) as modulation, such as presented in U.S. Patent Pub. No. 2023/0139079. More recently, burst position modulation has been proposed as an improvement over OOK modulation for communicating binary data.

[0026] In theory, the successful demodulation of burst position modulation (BPM) is according to the assumption that received accumulated energy in one time interval will be relatively low and the accumulated energy in another time interval will be relatively high. However, in some implementations, aiming for very low power operation and low complex circuit architecture, the implementation of a wakeup receiver may eliminate a radio frequency oscillator and employ a simpler filtering chain with moderate stopband attenuation. This disclosure recognizes that such design strategy results in weaker selectivity and energy leakage to neighboring time-interval. One outcome is that the accumulated energy between two time -intervals can be very close, particularly under in low signal-to-noise-ratio operating environments.

[0027] Exemplary embodiments of enhancements to BPM are presented herein that result in improved performance, particularly in UWB contexts. In BPM, a logical 0 (also referred to as a binary 0) and a logical 1 (also referred to as a binary 1) are assigned adjacent time intervals within a symbol duration, with the symbol duration typically on the order of 1 millisecond (ms). The time intervals assigned to a logical 0 or logical 1 may be much shorter than the symbol duration, such as 4 nanoseconds (ns), which is 1/250 of an exemplary 1 ms symbol duration. This disclosure recognizes that the performance of BPM can be improved if a time gap (which also may be referred to as a guard interval) is introduced between the time intervals assigned to a logical 0 and a logical 1 within a given symbol duration. Although the enhancements to BPM are not limited to UWB applications, the enhancements are presented herein in the context of UWB embodiments, with the understanding that they are not limited to UWB applications.

[0028] FIG. 1 is a schematic diagram of an exemplary wireless communication system 10, according to some aspects of the present disclosure. As shown the wireless communication system 10 includes two communication devices 80, 82 in communication with each other. The communication devices 80, 82 may be portable wireless communication devices, which may also implement a combination of cellular, Bluetooth, and/or Wi-Fi connectivity. Each communication device 80, 82 includes a transmitter circuit 12, a transmitter antenna (and associated circuit) 18, a receiver circuit 14, a receiver antenna (and associated circuit) 20, a processor 90, and a memory 30 as shown, a transmitter circuit 12 is configured according to embodiments of the present disclosure to wake up a receiver circuit 14 via a wakeup impulse sequence 16. The transmitter circuit 12 can be configured to transmit the wakeup impulse sequence 16 in an RF signal via a transmit antenna circuit 18 and the receiver circuit 14 can be configured to receive the wakeup impulse sequence 16 via a receive antenna circuit 20. Notably, each of the transmit antenna circuit 18 and the receive antenna circuit 20 can include one or more antennas of any suitable type and be arranged in any suitable configuration. In some embodiments, the wakeup impulse sequence 16 is a special sequence with a sole purpose of waking up the receiver circuit 14.

[0029] The processor 90 may process the digitized received signal to extract the information or data bits conveyed in the received signal. This processing may include decoding and error correction. The processor may be generally implemented in one or more general purpose processors, baseband processors, digital signal processors (DSPs), and/or application specific integrated circuits (ASICs). The processor 90 may also format digitized information for the transmitter circuit 12.

[0030] The memory 30 may be used for storage of data and program code and instructions. The memory 30 may include volatile and/or non-volatile memory or storage elements, may be implemented as a non-transitory computer-readable medium, and may be implemented as some combination of random access memory (RAM) and read-only memory (ROM).

[0031] FIG. 2 is a block diagram illustrating a general structure of the wakeup impulse sequence 16 in FIG. 1, according to some aspects of the present disclosure. Specifically, the wakeup impulse sequence 16 includes a preamble 22, a start frame delimiter (SFD) 24 (a.k.a. start bit), and an address 26. The preamble 22 includes multiple preamble symbols 28(1)- 28(N). In a non-limiting example, each of the preamble symbols 28(1)-28(N) has a symbol duration of one millisecond (1 ms). The SFD 24 includes a single stall bit symbol 34 and the address 26 includes multiple address symbols 36(1)-36(M). Like the preamble symbols 28(1)-28(N), each of the single start bit symbol 34 and the address symbols 36(1)-36(M) is also 1 ms in duration.

[0032] In a non-limiting example, the preamble symbols 28(1)-28(N), the single start bit symbol 34, and the address symbols 36(1)-36(M) are all modulated based on enhanced BPM as described herein, where the location of a pulse burst in a time interval designated for a logical “0” indicates that a logical 0 is sent and the location of a pulse burst in a time interval designated for a logical “1” indicates that a logical 1 is sent. A pulse burst may include one or more UWB pulses, for example.

[0033] FIG. 3 illustrates conventional BPM, according to some aspects of the present disclosure. A logical 0 and a logical 1 are illustrated in an exemplary 1 ms symbol interval. As shown, the first two t ps (microseconds) time intervals are designated for pulse bursts and the remaining time is empty. In some embodiments, the value of t is 4 ps, resulting in the reservation of the first 8 ps of the 1 ms symbol duration for pulse energy. In a low -power and low-cost wakeup receiver implementation due to the weaker selectivity, the burst energy emits to the neighboring time interval causing difficulty in distinguishing 1 and 0.

[0034] FIG. 4 illustrates so-called “enhanced” BPM, according to some aspects of the present disclosure. A logical 0 and a logical 1 are illustrated in an exemplary 1 ms symbol interval. Note that a time gap (or guard interval) indicated as T is introduced between the pulse intervals as compared to FIG. 3. Thus, a time period of t ps in this example is reserved at the beginning of a symbol period for one logical value and a time gap T later another time period of t ps is reserved for another logical value. The amount of this time gap T is predetermined and depends on the implementation. The time period t ps may be, as examples, 4 ps, 8 ps, etc. The time gap may be, as examples, 4 ps, 8 ps, 16 ps, ... up to 0.5 ms. [0035] FIG. 5 is a schematic diagram providing an exemplary illustration of the receiver circuit 14 in the wireless communication system 10 of FIG. 1, according to some aspects of the present disclosure. The receiver circuit 14 includes a main receiver circuit 38 and a wakeup receiver circuit 40. The main receiver circuit 38 implements UWB physical (PHY) and medium access control (MAC) layer protocols as defined in the Institute of Electrical and Electronic Engineers (IEEE) 802.15.4a/z standard. In this regard, the main receiver circuit 38 is a UWB receiver circuit, which implements a UWB protocol stack 42 and is operable to receive a UWB signal 44. Since the main receiver circuit 38 supports the entire UWB protocol stack 42, the main receiver circuit 38 will understandably consume more energy (a.k.a. battery power) whenever the main receiver circuit 38 is active and operational. As such, it may be desirable to keep the main receiver circuit 38 in sleep (a.k.a. power saving) mode as much as possible, only to be woken up as necessary.

[0036] The wakeup receiver circuit 40 may typically consume far less energy than the main receiver circuit 38. As such, the wakeup receiver circuit 40 will be operational to monitor the wakeup impulse sequence 16 transmitted from the transmitter circuit 12. In an embodiment, the wakeup receiver circuit 40 may wake up periodically to detect the wakeup impulse sequence 16 to help further reduce power consumption of the receiver circuit 14. [0037] When the wakeup receiver circuit 40 detects the wakeup impulse sequence 16, the wakeup receiver circuit 40 will attempt to decode the address 26 in the wakeup impulse sequence 16 to determine whether the wakeup impulse sequence 16 is intended to wake up the receiver circuit 14. When the wakeup receiver circuit 40 determines that the wakeup impulse sequence 16 is indeed intended to wake up the receiver circuit 14, the wakeup receiver circuit 40 will generate a wakeup signal 46 to wake up the main receiver circuit 38. By keeping the main receiver circuit 38 asleep as much as possible, it is possible to reduce power consumption, thus making the receiver circuit 14 an ideal receiver option for an loT device(s).

[0038] In an embodiment, the wakeup receiver circuit 40 may be turned off when the main receiver circuit 38 is operational. In this regard, the main receiver circuit 38 may send an indication signal 48 to wake up the wakeup receiver circuit 40 when the main receiver circuit 38 is returning to the sleep mode.

[0039] In an embodiment, the wakeup receiver circuit 40 includes a wakeup signal detector circuit 50, a decoder circuit 52, and a control circuit 54. The wakeup signal detector circuit 50 is configured to detect the preamble symbols 28( 1)-28(N), the start bit symbol 34, and the address symbols 36(1)-36(M) in the wakeup impulse sequence 16. In an embodiment, the wakeup signal detector circuit 50 is configured to output a signal detection indication 56 to indicate to the decoder circuit 52 and the control circuit 54 the series of bits indicated by pulse bursts in the preamble symbols 28(1 )-28(N), the start bit symbol 34, and the address symbols 36(1 )-36(M). The decoder circuit 52 is configured to decode the address 26 based on the indication of a binary 0 or binary 1 in each of the address symbols 36(1)-36(M), as indicated by enhanced BPM, such as shown in FIG. 4, to obtain the receiver identification and send the obtained receiver identification to the control circuit 54. [0040] The control circuit 54, which can be a synthesized logic, as an example, is configured to check the receiver identification indicated by the address 26 to determine whether the wakeup impulse sequence 16 is intended to wake up the receiver circuit 14. If the receiver identification indicated by the address 26 matches the identification of the receiver circuit 14, the control circuit 54 can conclude that the wakeup impulse sequence 16 is intended to wake up the receiver circuit 14. Accordingly, the control circuit 54 can generate the wakeup signal 46 to wake up the main receiver circuit 38.

[0041] As mentioned earlier, the wakeup receiver circuit 40 may be turned on periodically or when the main receiver circuit 38 returns to the sleep mode. Moreover, the wakeup receiver circuit 40 may not have an internal clock that is precisely synchronized with a clock in the transmitter circuit 12. As such, the wakeup receiver circuit 40 may be turned on anywhere during the preamble 22. In other words, the wakeup receiver circuit 40 may not always be turned on exactly at the start of the first preamble symbol 28(1). In addition, since the duration of the pulse burst is far shorter than the duration of any of the preamble symbols 28(1)-28(N), the wakeup receiver circuit 40 may not know where exactly the pulse burst is located inside any of the preamble symbols 28( 1)-28(N).

[0042] Fortunately, the embodiments disclosed herein do not require the wakeup receiver circuit 40 to detect all the preamble symbols 28(1 )-28(N). In fact, the wakeup receiver circuit 40 can still carry out the intended operation by detecting a subset of the preamble symbols 28(1)-28(N). As such, whenever the wakeup receiver circuit 40 is turned on, the wakeup signal detector circuit 50 must stay on long enough to detect the pulse burst in any of the preamble symbols 28(1 )-28(N). Thereafter, the wakeup signal detector circuit 50 can correctly detect remaining preamble symbols among the preamble symbols 28(1)-28(N), the start bit symbol 34, and the address symbols 36(1)-36(M).

[0043] FIG. 6 is a schematic diagram providing an exemplary illustration of the wakeup signal detector circuit 50 in the receiver circuit 14 of FIG. 3, according to some aspects of the present disclosure. Common elements between FIGS. 5 and 6 are shown herein with common element numbers and will not be re-described herein.

[0044] In an embodiment, the wakeup signal detector circuit 50 includes a match circuit 8, a low-noise amplifier (LN A) 60, an intermediate frequency (IF) processing circuit 62, a multi-path filter circuit 64, and a baseband processing circuit 66. The match circuit 58 is coupled to the antenna circuit 20 to receive the wakeup impulse sequence 16 and impedance match the antenna 20 to the LNA 60. The LNA 60 is configured to amplify the wakeup impulse sequence 16. The IF processing circuit 62 is configured to convert the wakeup impulse sequence 16 into a multi-tone IF signal 68. In a non-limiting example, an envelope detector (not shown) may be provided in the IF processing circuit 62 to convert the RF signal 16 into the multi-tone IF signal 68. Notably, since the multi-tone IF signal 68 has a narrower bandwidth (e.g., 250 KHz) compared to a much wider bandwidth (e.g., 500 MHz) of the wakeup impulse sequence 16, the multi-tone IF signal 68 can be rich in harmonics and include a large amount of noise. In this regard, the multi-tone IF signal 68 as generated by the IF processing circuit 62 can be a multi-tone signal that includes not only a fundamental response 70, but also multiple harmonic responses 72, and a noise response 74.

[0045] FIG. 7 illustrates an output of a filter circuit for logical/binary 0 versus logical/binary 1 for various time gaps between these logical values using BPM (no time gap) and enhanced BPM (which uses a time gap), according to some aspects of the present disclosure. For example, FIG. 7 may represent a receiver analog output, such as an output of filter circuit 64 in FIG. 6. The binary 1 output is the same for all modulations because binary 1 is conveyed in the first 4 ps time interval. Binary 0 is conveyed in another 4 ps time interval using either no time gap or various time gaps (e.g., 8 ps or 16 ps) as shown in FIG. 7. [0046] For conventional BPM (no gap), it shows the accumulated energy E0 in the first time- interval is just slightly smaller than the accumulated energy El in the second timeinterval. In contrast, the EBPM with 16 us time gap has much lower accumulated energy E0 in first time-interval than the accumulated energy El in the second time interval. Considering the random nature of noise and interference, the large difference in accumulated energy between time intervals provided by EBPM in comparison this to the CBPM can provide a higher probability of successful detection of 0 and 1. This example further outlines the effectiveness and necessity of applying EBPM for a compact and low power implementation of wakeup receiver. [0047] In addition to using the accumulated energy to demodulate the burst, an alternative embodiment is to sample the amplitude or energy at one point per time interval. As shown in FIGS. 8A and 8B below, the EBPM (waveform in green) is demodulated by sampling one point (SO) in this example by 4us rate in the first time-interval and sampling another point (SI) in the second time interval. The same advantage of EBPM over CBPM applies here as well where the EBPM can better distinguish the 1 and 0 bursts. Comparing to the embodiment of demodulation using accumulated energy which requires multiple sampling points with values to calculate the accumulated energy, the alternative embodiment employing one sampling point per time interval can significantly reduce the complexity and power consumption while maintaining similar demodulation performance.

[0048] FIG. 9 illustrates an example symbol period, according to some aspects of the present disclosure. As shown, the symbol period is extended to 1.024 ms as compared to a conventional symbol period, which ensures that no 2 bursts ever occur inside the same 1 ms time period allowing the transmitter to transmit a full 1 ms of energy in each burst. As shown, the burst duration for the binary 1 and binary 0 is 8 ps each out of the 1 ms symbol period, with the time periods allotted for the binary 1 and binary 0 separated by 16 ps. This symbol period slightly reduces the bit rate from 1 kbps (kilobits per second) to about 0.98 kbps as compared to conventional BPM schemes. As compared to OOK, the performance improves by 3 dB and there is increased interference immunity while maintaining the same pulse power.

[0049] FIG. 10 illustrates a method of operating a receiver circuit 1000, according to some aspects of the present disclosure. In some embodiments, the receiver circuit includes a main receiver circuit and a wakeup receiver circuit, such as the receiver circuit 14 illustrated in FIG. 5. In step 1010, a wakeup impulse sequence is detected. In some embodiments, the wakeup impulse sequence comprises a preamble, a start bit, and an address, such as illustrated in FIG. 2. Each symbol of the wakeup impulse sequence, such as the symbols illustrated in FIG. 2, may be modulated using enhanced BPM, such as the BPM format illustrated in FIG. 4. In some embodiments, as shown in FIG. 4, in the enhanced burst position modulation scheme, a time period allocated to a binary 0 and a time period allocated to a binary 1 in a symbol period, such as 1 ms or 1.024 ms, are separated by a time gap (T), which may also be referred to as a guard interval. The wakeup impulse sequence may transmitted from a wireless communication device, such as wireless communication device 80. A transmitter circuit, such as transmitter circuitl2 in FIG. 1, may be responsible for formatting and communicating the wakeup impulse sequence. [0050] In step 1020, it is determined whether the wakeup impulse sequence is intended to wake up a main receiver circuit, such as the main receiver circuit 38 illustrated in FIG. 5. For example, if the address, which may contain a receiver identification, is compared against the identification of the receiver circuit, and there is a match, then the wakeup impulse sequence is indeed intended to wake up the main receiver circuit. Next in step 1030, the main receiver circuit, such as the main receiver circuit 38 in FIG. 5, is woken up in response to determining that the wakeup impulse sequence is intended to wake up the receiver circuit.

[0051] Some additional observations about BPM and enhanced BPM are provided below. [0052] BPM may have an approximately 3dB performance advantage over OOK for a wakeup scheme, even though theoretically OOK and BPM have the same performance. When comparing two modulation schemes the unencoded data is composed of an equal number of Is and 0s and the coded signals have the same power. Suppose BPM energy bursts representing the data have energy e, and are in a first position to represent a 1 or a second position to represent a 0. If the total number of encoded bits is n, then the total signal energy is ne. An OOK signal has no energy to represent a 0, so the energy to represent a I is 2c so that the total signal energy is equal. The OOK has approximately the same performance in the receiver since the difference in measured energy between a 1 and a 0 is 2e for both OOK and BPM. For a wakeup radio signal, using UWB at 1kbps, the total allowed energy in each millisecond is constrained by regulations to some upper limit. If the transmitter is using all the allowed transmit energy, then the OOK and BPM signal both have signal energy e to represent a logical 1. This means that in the receiver the energy difference for BPM is still 2e but for OOK it is only e which confers a 3dB advantage for BPM over OOK.

[0053] In some embodiments, if a 0.5 ms separation is used between a logical 0 and a logical 1, there may be two bursts inside a single ms. To avoid this situation, a much smaller separation may be used, e.g., 16 ps separation of 8 ps bursts. Then the bit rate may be decreased from 1 kbps to 1/1.016 kbps. This may also be done for the start bits. A further advantage is that off 1ms grid will help reducing interference and false detect, with a possible reason being that 1 ms is a good grid for UWB and used in protocols.

[0054] In some embodiments, a technique may be used whereby a check is made that there is no energy after a short while to prevent ordinary UWB signals from triggering a wakeup. During the Wakeup preamble detect phase the receiver turns on the analog circuitry and waits 1ms to see if there is a point where the energy crosses a predetermined threshold. We then also check to see that the energy drops below that threshold (or a different threshold for hysteresis). In practice we probably set that time delay to the same as the delay used to do the data demodulation comparison to differentiate ones and zeros, but it doesn’t have to be the same delay.

[0055] Optionally, in some embodiments, after it is determined that a wakeup preamble signal is being received, instead of going straight to data demodulation (checking that energy in position A is greater or less than in position B) it is verified that at least for the first following bit the energy goes from being below the logical 1 ’ s threshold to being above that logical 1 ’s threshold and then dropping again. This is to guard against false detection including the case where an ordinary UWB signal with lots of 64 MHz envelope energy in it, e.g., a BPRF STS signal, was ending and that makes it look like it was a logical 1 that dropped below the threshold. This may happen at the very start of looking for a Wakeup preamble. Otherwise, the signal may be too long to set off the Wakeup preamble detector.

[0056] Further aspects of the present disclosure include the following:

[0057] Aspect 1 includes a transmitter circuit configured to transmit a wakeup impulse sequence comprising a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, wherein the address comprises a plurality of address symbols that represent a receiver identification.

[0058] Aspect 2 includes the transmitter circuit of aspect 1 , wherein in the enhanced burst position modulation, a time period allocated to a binary 0 and a time period allocated to a binary 1 within each symbol period are separated by a time gap.

[0059] Aspect 3 includes the transmitter circuit of aspect 2, wherein the time period allocated to a binary 0 and the time period allocated to a binary 1 both equal 8 microseconds (ps).

[0060] Aspect 4 includes the transmitter circuit of aspect 2, wherein the time gap is at least 8 microseconds (ps).

[0061] Aspect 5 includes the transmitter circuit of aspect 1, wherein each of the plurality of address symbols has a symbol period of 1.024 millisecond (ms), and wherein each of the plurality of symbols conveys exactly one logical value in a pulse burst of not greater than 8 microseconds (ps).

[0062] Aspect 6 includes the transmitter circuit of aspect 1 , wherein the wakeup impulse sequence is intended for a receiver circuit associated with the receiver identification, wherein the receiver circuit comprises a main receiver circuit and a wakeup receiver circuit, and wherein the wakeup impulse sequence is intended to wake up the main receiver circuit in response to determining that the receiver identification represented by the address matches an identification of the receiver circuit. [0063] Aspect 7 includes the transmitter circuit of aspect 2, wherein the preamble comprises a plurality of preamble symbols and the start bit comprises exactly one start bit symbol representing a start frame delimiter.

[0064] Aspect 8 includes the transmitter circuit of aspect 2, wherein each binary 0 and binary 1 are transmitted using ultra- wideband modulation.

[0065] Aspect 9 includes the method of operating a wireless communication device, the method comprising: transmitting a wakeup impulse sequence comprising a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, wherein the address comprises a plurality of address symbols that represent a receiver identification.

[0066] Aspect 10 includes the method of aspect 9, wherein in the enhanced burst position modulation, a time period allocated to a binary 0 and a time period allocated to a binary 1 within each symbol period are separated by a time gap.

[0067] Aspect 11 includes the method of aspect 10, wherein the time period allocated to a binary 0 and the time period allocated to a binary 1 both equal 8 microseconds (ps).

[0068] Aspect 12 includes the method of aspect 10, wherein the time gap is at least 8 microseconds (ps).

[0069] Aspect 13 includes the method of aspect 9, wherein each of the plurality of address symbols has a symbol period of 1.024 millisecond (ms), and wherein each of the plurality of symbols conveys exactly one logical value in a pulse burst of not greater than 8 microseconds (ps).

[0070] Aspect 14 includes the method of aspect 9, wherein the wakeup impulse sequence is intended for a receiver circuit associated with the receiver identification, wherein the receiver circuit comprises a main receiver circuit and a wakeup receiver circuit, and wherein the wakeup impulse sequence is intended to wake up the main receiver circuit in response to determining that the receiver identification represented by the address matches an identification of the receiver circuit.

[0071] Aspect 15 includes the method of aspect 10, wherein the preamble comprises a plurality of preamble symbols and the start bit comprises exactly one start bit symbol representing a start frame delimiter.

[0072] Aspect 16 includes a receiver circuit comprising: a main receiver circuit; and a wakeup receiver circuit configured to: detect a wakeup impulse sequence, wherein the wakeup impulse sequence comprises a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, wherein the address comprises a plurality of address symbols that represent a receiver identification; determine whether the wakeup impulse sequence is intended to wake up the main receiver circuit; and wake up the main receiver circuit in the receiver circuit in response to determining that the wakeup impulse sequence is intended to wake up the receiver circuit.

[0073] Aspect 17 includes the receiver circuit of aspect 16, wherein in the enhanced burst position modulation, a time period allocated to a binary 0 and a time period allocated to a binary 1 within each symbol period are separated by a time gap.

[0074] Aspect 18 includes the receiver circuit of aspect 17, wherein the time period allocated to a binary 0 and the time period allocated to a binary 1 both equal 8 microseconds (ps).

[0075] Aspect 19 includes the receiver circuit of aspect 17, wherein the time gap is at least 8 microseconds (ps).

[0076] Aspect 20 includes the receiver circuit of aspect 16, wherein each of the plurality of address symbols has a symbol period of 1.024 millisecond (ms), and wherein each of the plurality of symbols conveys exactly one logical value in a pulse burst of not greater than 8 microseconds (ps).

[0077] Aspect 21 includes the receiver circuit of aspect 16, wherein the wakeup receiver circuit is further configured to determine that the wakeup impulse sequence is intended to wake up the main receiver circuit in response to determining that the receiver identification represented by the address matches an identification of the receiver circuit.

[0078] Aspect 22 includes the receiver circuit of aspect 17, wherein the wakeup receiver circuit comprises a wake up signal detector circuit configured to detect the plurality of address symbols.

[0079] Aspect 23 includes a portable wireless communication device comprising: the receiver circuit of aspect 16; and a transmitter circuit configured to transmit a second wakeup sequence.

[0080] Aspect 24 includes the receiver circuit of aspect 17, wherein detecting the wakeup impulse sequence comprises demodulating each of the plurality of address symbols, and wherein demodulating each of the plurality of address symbols comprises comparing an accumulated energy in the time period allocated to a binary 0 and an accumulated energy in the time period allocated to a binary 1.

[0081] Aspect 25 includes a method of operating a receiver circuit, wherein the receiver circuit comprises a main receiver circuit and a wakeup receiver circuit, the method comprising: detecting a wakeup impulse sequence, wherein the wakeup impulse sequence comprises a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, and wherein the address comprises a plurality of address symbols that represent a receiver identification; determining whether the wakeup impulse sequence is intended to wake up the main receiver circuit; and waking up the main receiver circuit in the receiver circuit in response to determining that the wakeup impulse sequence is intended to wake up the receiver circuit.

[0082] Aspect 26 includes the method of aspect 25, wherein in the enhanced burst position modulation, a time period allocated for a binary 0 and a time period allocated for a binary 1 within each symbol period are separated by a time gap.

[0083] Aspect 27 includes the method of aspect 26, wherein the time period allocated to a binary 0 and the time period allocated to a binary 1 both equal 8 microseconds (ps).

[0084] Aspect 28 includes the method of aspect 26, wherein the time gap is at least 8 microseconds (ps).

[0085] Aspect 29 includes the method of aspect 25, wherein each of the plurality of address symbols has a symbol period of 1.024 millisecond (ms), and wherein each of the plurality of symbols conveys exactly one logical value in a pulse burst of not greater than 8 microseconds (ps).

[0086] Aspect 30 includes the method of aspect 25, further comprising determining that the wakeup impulse sequence is intended to wake up the receiver circuit in response to determining that the receiver identification represented by the address matches an identification of the receiver circuit.

[0087] Aspect 31 includes the method of aspect 26, wherein detecting the wakeup impulse sequence comprises demodulating each of the plurality of address symbols, and wherein demodulating each of the plurality of address symbols comprises comparing the accumulated energy in the time period allocated to a binary 0 and the time period allocated to a binary 1.

[0088] Persons skilled in the art will recognize that the apparatus, systems, and methods described above can be modified in various ways. Accordingly, persons of ordinary skill in the art will appreciate that the embodiments encompassed by the present disclosure are not limited to the particular exemplary embodiments described above. In that regard, although illustrative embodiments have been shown and described, a wide range of modification, change, and substitution is contemplated in the foregoing disclosure. It is understood that such variations may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the present disclosure.

Claims

CLAIMS What is claimed is:

1. A transmitter circuit configured to transmit a wakeup impulse sequence comprising a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, wherein the address comprises a plurality of address symbols that represent a receiver identification.

2. The transmitter circuit of claim 1 , wherein in the enhanced burst position modulation, a time period allocated to a binary 0 and a time period allocated to a binary 1 within each symbol period are separated by a time gap.

3. The transmitter circuit of claim 2, wherein the time period allocated to a binary 0 and the time period allocated to a binary 1 both equal 8 microseconds (ps).

4. The transmitter circuit of claim 2, wherein the time gap is at least 8 microseconds (ps).

5. The transmitter circuit of claim 1, wherein each of the plurality of address symbols has a symbol period of 1 .024 millisecond (ms), and wherein each of the plurality of symbols conveys exactly one logical value in a pulse burst of not greater than 8 microseconds (p s).

6. The transmitter circuit of claim 1 , wherein the wakeup impulse sequence is intended for a receiver circuit associated with the receiver identification, wherein the receiver circuit comprises a main receiver circuit and a wakeup receiver circuit, and wherein the wakeup impulse sequence is intended to wake up the main receiver circuit in response to determining that the receiver identification represented by the address matches an identification of the receiver circuit.

7. The transmitter circuit of claim 2, wherein the preamble comprises a plurality of preamble symbols and the start bit comprises exactly one start bit symbol representing a start frame delimiter.

8. The transmitter circuit of claim 2, wherein each binary 0 and binary 1 are transmitted using ultra-wideband modulation.

9. A method of operating a wireless communication device, the method comprising: transmitting a wakeup impulse sequence comprising a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, wherein the address comprises a plurality of address symbols that represent a receiver identification.

10. The method of claim 9, wherein in the enhanced burst position modulation, a time period allocated to a binary 0 and a time period allocated to a binary 1 within each symbol period are separated by a time gap.

11. The method of claim 10, wherein the time period allocated to a binary 0 and the time period allocated to a binary 1 both equal 8 microseconds (ps).

12. The method of claim 10, wherein the time gap is at least 8 microseconds (ps).

13. The method of claim 9, wherein each of the plurality of address symbols has a symbol period of 1.024 millisecond (ms), and wherein each of the plurality of symbols conveys exactly one logical value in a pulse burst of not greater than 8 microseconds (ps).

14. The method of claim 9, wherein the wakeup impulse sequence is intended for a receiver circuit associated with the receiver identification, wherein the receiver circuit comprises a main receiver circuit and a wakeup receiver circuit, and wherein the wakeup impulse sequence is intended to wake up the main receiver circuit in response to determining that the receiver identification represented by the address matches an identification of the receiver circuit.

15. The method of claim 10, wherein the preamble comprises a plurality of preamble symbols and the start bit comprises exactly one start bit symbol representing a start frame delimiter.

16. A receiver circuit comprising: a main receiver circuit; and a wakeup receiver circuit configured to: detect a wakeup impulse sequence, wherein the wakeup impulse sequence comprises a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, wherein the address comprises a plurality of address symbols that represent a receiver identification; determine whether the wakeup impulse sequence is intended to wake up the main receiver circuit; and wake up the main receiver circuit in the receiver circuit in response to determining that the wakeup impulse sequence is intended to wake up the receiver circuit.

17. The receiver circuit of claim 16, wherein in the enhanced burst position modulation, a time period allocated to a binary 0 and a time period allocated to a binary 1 within each symbol period are separated by a time gap.

18. The receiver circuit of claim 17, wherein the time period allocated to a binary 0 and the time period allocated to a binary 1 both equal 8 microseconds (ps).

19. The receiver circuit of claim 17, wherein the time gap is at least 8 microseconds (ps).

20. The receiver circuit of claim 16, wherein each of the plurality of address symbols has a symbol period of 1.024 millisecond (ms), and wherein each of the plurality of symbols conveys exactly one logical value in a pulse burst of not greater than 8 microseconds (ps).

21. The receiver circuit of claim 16, wherein the wakeup receiver circuit is further configured to determine that the wakeup impulse sequence is intended to wake up the main receiver circuit in response to determining that the receiver identification represented by the address matches an identification of the receiver circuit.

22. The receiver circuit of claim 17, wherein the wakeup receiver circuit comprises a wake up signal detector circuit configured to detect the plurality of address symbols.

23. A portable wireless communication device comprising: the receiver circuit of claim 16; and a transmitter circuit configured to transmit a second wakeup sequence.

24. The receiver circuit of claim 17, wherein detecting the wakeup impulse sequence comprises demodulating each of the plurality of address symbols, and wherein demodulating each of the plurality of address symbols comprises comparing an accumulated energy in the time period allocated to a binary 0 and an accumulated energy in the time period allocated to a binary 1.

25. A method of operating a receiver circuit, wherein the receiver circuit comprises a main receiver circuit and a wakeup receiver circuit, the method comprising: detecting a wakeup impulse sequence, wherein the wakeup impulse sequence comprises a preamble, a start bit, and an address, each of which is modulated using enhanced burst position modulation, and wherein the address comprises a plurality of address symbols that represent a receiver identification; determining whether the wakeup impulse sequence is intended to wake up the main receiver circuit; and waking up the main receiver circuit in the receiver circuit in response to determining that the wakeup impulse sequence is intended to wake up the receiver circuit.

26. The method of claim 25, wherein in the enhanced burst position modulation, a time period allocated for a binary 0 and a time period allocated for a binary 1 within each symbol period are separated by a time gap.

27. The method of claim 26, wherein the time period allocated to a binary 0 and the time period allocated to a binary 1 both equal 8 microseconds (ps).

28. The method of claim 26, wherein the time gap is at least 8 microseconds (ps)..

29. The method of claim 25, wherein each of the plurality of address symbols has a symbol period of 1.024 millisecond (ms), and wherein each of the plurality of symbols conveys exactly one logical value in a pulse burst of not greater than 8 microseconds (ps).

30. The method of claim 25, further comprising determining that the wakeup impulse sequence is intended to wake up the receiver circuit in response to determining that the receiver identification represented by the address matches an identification of the receiver circuit.

31. The method of claim 26, wherein detecting the wakeup impulse sequence comprises demodulating each of the plurality of address symbols, and wherein demodulating each of the plurality of address symbols comprises comparing the accumulated energy in the time period allocated to a binary 0 and the time period allocated to a binary 1.