Zero crossing avoidance coding for quadrature amplitude modulation

Abstract

An apparatus for wireless communication is disclosed that performs zero-crossing avoidance coding for quadrature amplitude modulation. In an example aspect, the apparatus includes a polarity transceiver configured to be coupled to an antenna. The polarity transceiver is configured to transmit, via the antenna, data comprising a plurality of symbols associated with quadrature amplitude modulation. The plurality of symbols includes a plurality of sets of two consecutive symbols. An absolute value of a phase difference between the two consecutive symbols within each of the plurality of sets is substantially different from 180 degrees.

Description

Technical Field

[0001] The present disclosure relates generally to wireless transceivers and other components that employ quadrature amplitude modulation, and more particularly to encoding symbols associated with quadrature amplitude modulation to avoid zero-crossing conditions. Background Art

[0002] Electronic devices use radio frequency (RF) signals to communicate information. These RF signals enable users to talk with friends, download information, share pictures, remotely control home devices, and receive global positioning information. While it may be desirable to design electronic devices with a small footprint and long battery life to support mobile operation, designing wireless transceivers that meet the size and / or power constraints of electronic devices can be challenging. Summary of the Invention

[0003] Disclosed is a device for implementing zero-crossing avoidance coding for quadrature amplitude modulation (QAM). Specifically, a modem encodes symbols associated with QAM in a manner that avoids zero-crossing conditions. For example, the modem modifies the phase of the symbols so that the absolute value of the phase difference between two consecutive symbols is substantially different than 180 degrees. Optionally, the modem may further modify the amplitude of the symbols. In some cases, the zero-crossing avoidance coding causes a symbol to have the same symbol state as the previous symbol. The zero-crossing avoidance encoder also generates a correction list to identify symbols encoded using the zero-crossing avoidance coding. Using the zero-crossing avoidance coding, a wireless transceiver can perform QAM and meet adjacent channel power (ACP) and / or error vector magnitude (EVM) performance metrics for electronic devices. The techniques associated with the zero-crossing avoidance coding are applicable to various types of wireless transceivers, including polar and Cartesian transceivers.

[0004] In an example aspect, an apparatus for wireless communication is disclosed. The apparatus includes a polar transceiver configured to be coupled to an antenna. The polar transceiver is configured to transmit, via the antenna, data comprising a plurality of symbols associated with quadrature amplitude modulation. The plurality of symbols includes a plurality of sets of two consecutive symbols. An absolute value of a phase difference between the two consecutive symbols in each set of the plurality of sets is substantially different from 180 degrees.

[0005] In an example aspect, an apparatus for wireless communication is disclosed. The apparatus includes a wireless transceiver configured to be coupled to an antenna. The wireless transceiver is further configured to communicate data via the antenna. The data includes a plurality of symbols associated with quadrature amplitude modulation and encoded using zero-crossing avoidance coding. The wireless transceiver is further configured to communicate a correction list via the antenna, the correction list identifying symbols of the plurality of symbols that have been encoded using zero-crossing avoidance coding.

[0006] In an example aspect, a method for performing zero-crossing avoidance encoding is disclosed. The method includes receiving a first pair of consecutive symbols associated with quadrature amplitude modulation. The first pair of consecutive symbols includes a first symbol and a second symbol. The method also includes outputting the first symbol as part of an encoded data sequence. The method further includes determining that the first pair of consecutive symbols is associated with a zero-crossing condition. Based on the determination, the method includes modifying the second symbol to generate a modified symbol that avoids the zero-crossing condition.

[0007] In an example aspect, at least one computer-readable storage medium is disclosed. The computer-readable storage medium includes instructions that, in response to execution by a processor, cause the processor to receive a first pair of consecutive symbols associated with quadrature amplitude modulation. The first pair of consecutive symbols includes a first symbol and a second symbol. The instructions further cause the processor to output the first symbol as part of an encoded data sequence. The instructions further cause the processor to determine that the first pair of consecutive symbols is associated with a zero-crossing condition. The instructions further cause the processor, based on the determination, to modify the second symbol to generate a modified symbol that avoids the zero-crossing condition. The instructions further cause the processor to generate a correction list indicating that the second symbol has been modified to avoid the zero-crossing condition. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 An example operating environment for a device supporting zero-crossing avoidance coding for quadrature amplitude modulation is illustrated.

[0009] Figure 2 An example modem implementing zero-crossing avoidance coding for quadrature amplitude modulation is illustrated.

[0010] Figure 3 An example wireless transceiver that performs quadrature amplitude modulation is illustrated.

[0011] Figure 4 An example constellation diagram associated with sixteen-level quadrature amplitude modulation is illustrated.

[0012] Figure 5 Example zero-crossing conditions associated with sixteen-level quadrature amplitude modulation are illustrated.

[0013] Figure 6-1 An example sequence of symbols associated with a zero-crossing condition is illustrated.

[0014] Figure 6-2 An example sequence of symbols encoded using zero-crossing avoidance coding is illustrated.

[0015] Figure 7 An example scheme implemented by a zero-crossing avoidance encoder is illustrated.

[0016] Figure 8An example transaction diagram between a transmitting entity and a receiving entity for implementing zero-crossing avoidance coding for quadrature amplitude modulation is illustrated.

[0017] Figure 9 An example protocol data unit according to zero-crossing avoidance encoding for quadrature amplitude modulation is illustrated.

[0018] Figure 10 is a flow chart for performing zero-crossing avoidance coding.

[0019] Figure 11 is a flow chart for performing zero-crossing avoidance decoding. DETAILED DESCRIPTION

[0020] Electronic devices use radio frequency (RF) signals to communicate information. To increase throughput within a given bandwidth, electronic devices may use techniques such as quadrature amplitude modulation (QAM) to communicate multiple bits per symbol. QAM modulates information onto a carrier signal using amplitude modulation, phase modulation, and / or both amplitude and phase modulation. A Cartesian transceiver (or in-phase and quadrature (IQ) transceiver) is a type of wireless transceiver that can perform QAM. A Cartesian transceiver includes an IQ modulator / demodulator. However, the hardware limitations of a Cartesian transceiver can make it challenging to meet the size and / or power constraints of an electronic device.

[0021] Another type of wireless transceiver is a polar transceiver. While Cartesian transceivers can encode information via in-phase and quadrature basis vectors, polar transceivers encode information via polar basis vectors (e.g., amplitude and phase). Compared to Cartesian transceivers, polar transceivers can have a smaller footprint and consume less power.

[0022] Some types of quadrature amplitude modulation generate two consecutive symbols with symbol states that are approximately 180 degrees out of phase. This causes the signal trajectory between these two symbol states to pass through the origin of the constellation diagram, known as a zero-crossing condition. Some polar transmitters, such as those with frequency modulators, may not be able to achieve a 180-degree phase shift because it requires an infinite deviation in frequency. This limitation creates phase distortion, which can degrade the polar transmitter's adjacent channel power (ACP) and / or error vector magnitude (EVM) performance. Therefore, meeting electronic device performance metrics under zero-crossing conditions can be challenging for polar transmitters.

[0023] To avoid zero-crossing conditions, some electronic devices use polar transmitters with other types of modulation that do not cause zero-crossing conditions. In this case, the electronic device does not perform quadrature amplitude modulation, which could cause zero-crossing conditions. Other techniques may add a certain amount of distortion to avoid zero-crossing conditions. However, this additional distortion may make it challenging for the polar transmitter to meet the adjacent channel power and / or error vector magnitude limits of the electronic device.

[0024] In contrast, example techniques for performing zero-crossing avoidance coding for quadrature amplitude modulation (QAM) are described. Specifically, a modem encodes symbols associated with QAM in a manner that avoids zero-crossing conditions. For example, the modem modifies the phase of the symbols so that the absolute value of the phase difference between two consecutive symbols is substantially different than 180 degrees. Optionally, the modem may further modify the amplitude of the symbols. In some cases, the zero-crossing avoidance coding causes a symbol to have the same symbol state as the previous symbol. The zero-crossing avoidance encoder also generates a correction list to identify symbols encoded using the zero-crossing avoidance coding. Using the zero-crossing avoidance coding, a wireless transceiver can perform QAM and meet adjacent channel power and / or error vector magnitude performance metrics for electronic devices. Techniques associated with the zero-crossing avoidance coding are applicable to various types of wireless transceivers, including polar and Cartesian transceivers.

[0025] Figure 1 An example environment 100 for implementing aspects of zero-crossing avoidance coding for quadrature amplitude modulation is illustrated. In environment 100, a computing device 102 communicates with a base station 104 via a wireless communication link 106 (wireless link 106). In this example, computing device 102 is depicted as a smartphone. However, computing device 102 can be implemented as any suitable computing or electronic device, such as a modem, a cellular base station, a broadband router, an access point, a cellular phone, a gaming device, a navigation device, a media device, a laptop computer, a desktop computer, a tablet computer, a wearable computer, a server, a network-attached storage (NAS) device, a smart appliance or other Internet of Things (IoT) device, wireless earbuds or headphones, a medical device, a vehicle-based communication system, a radio, and the like.

[0026] Base station 104 communicates with computing device 102 via wireless link 106, which can be implemented as any suitable type of wireless link. Although depicted as a cellular network tower, base station 104 can represent or be implemented as another device, such as another computing device (e.g., another smartphone), a satellite, a server device, a terrestrial television broadcast tower, an access point, a peer device, a mesh network node, etc. Thus, computing device 102 can communicate with base station 104 or another device via a wireless connection.

[0027] Wireless link 106 may include a downlink for data or control information communicated from base station 104 to computing device 102, an uplink for other data or control information communicated from computing device 102 to base station 104, or both a downlink and an uplink. Wireless link 106 may be implemented using any suitable communication protocol or standard, such as second generation (2G), third generation (3G), fourth generation (4G), or fifth generation (5G) cellular; IEEE 802.11 (e.g., Wi-Fi); ® ); IEEE 802.15 (e.g., Bluetooth ® ); IEEE 802.16 (e.g., WiMAX ® ); etc. In some implementations, the wireless link 106 can provide power wirelessly, and the base station 104 or the computing device 102 can include a power source.

[0028] As shown, computing device 102 includes an application processor 108 and a computer-readable storage medium 110 (CRM 110). Application processor 108 may include any type of processor, such as a multi-core processor, that executes processor-executable code stored by CRM 110. CRM 110 may include any suitable type of data storage medium, such as volatile memory (e.g., random access memory (RAM)), non-volatile memory (e.g., flash memory), optical media, magnetic media (e.g., disk), etc. In the context of the present disclosure, CRM 110 is implemented to store instructions 112, data 114, and other information for computing device 102, and therefore does not include transient propagating signals or carrier waves.

[0029] The computing device 102 may also include input / output ports 116 (I / O ports 116) and a display 118. The I / O ports 116 enable data exchange or interaction with other devices, networks, or users. The I / O ports 116 may include a serial port (e.g., a Universal Serial Bus (USB) port), a parallel port, an audio port, an infrared (IR) port, a user interface port such as a touch screen, and the like. The display 118 presents graphics for the computing device 102, such as a user interface associated with an operating system, program, or application. Alternatively or additionally, the display 118 may be implemented as a display port or a virtual interface through which the graphical content of the computing device 102 is presented.

[0030] The wireless transceiver 120 of the computing device 102 provides connectivity to a corresponding network and other electronic devices connected thereto. The wireless transceiver 120 can facilitate communication over any suitable type of wireless network, such as a wireless local area network (WLAN), a peer-to-peer (P2P) network, a mesh network, a cellular network, an ultra-wideband (UWB) network, a wireless wide area network (WWAN), and / or a wireless personal area network (WPAN). In the context of the example environment 100, the wireless transceiver 120 enables the computing device 102 to communicate with the base station 104 and the network connected thereto. However, the wireless transceiver 120 can also enable the computing device 102 to communicate "directly" with other devices or networks.

[0031] Wireless transceiver 120 includes circuitry and logic for transmitting and receiving communication signals via antenna 122. Components of wireless transceiver 120 may include amplifiers, switches, mixers, filters, analog-to-digital converters, digital-to-analog converters, and the like for conditioning communication signals (e.g., for generating or processing signals). Wireless transceiver 120 may also include logic for performing operations such as synthesis, encoding, decoding, modulation, demodulation, and the like. In some cases, components of wireless transceiver 120 are implemented as separate transmitter and receiver entities. Additionally or alternatively, wireless transceiver 120 may be implemented using multiple or distinct components to implement corresponding transmit and receive operations (e.g., separate transmit and receive chains). Generally speaking, wireless transceiver 120 processes data and / or signals associated with data communicated to computing device 102 via antenna 122.

[0032] exist Figure 1 In the example shown in , the computing device 102 includes at least one modem 124. The modem 124, which may be implemented as a processor, controls the wireless transceiver 120 and enables wireless communications. The modem 124 may include a portion of the CRM 110 or may access the CRM 110 to obtain computer-readable instructions. The modem 124 may include baseband circuitry to perform analog-to-digital conversion, digital-to-analog conversion, Fourier transforms, gain correction, skew correction, frequency conversion, encoding, decoding, modulation, demodulation, and the like. The modem 124 may provide communication data to the wireless transceiver 120 for transmission. The modem 124 may also process a baseband version of the signal obtained from the wireless transceiver 120 to generate data, which may be provided to other parts of the computing device 102 via the communication interface. Although in Figure 1 1. Modem 124 is depicted separately from wireless transceiver 120 in FIG. 1, but other implementations of wireless transceiver 120 may include modem 124. In this case, modem 124 may be considered a component of wireless transceiver 120.

[0033] The wireless transceiver 120 may be implemented using a variety of different types of transceivers, including a polar transceiver 126 or a Cartesian transceiver 128. Generally, the wireless transceiver 120 may perform quadrature amplitude modulation 130. Quadrature amplitude modulation 130 refers to a combination of amplitude modulation and phase modulation. For the purposes of zero-crossing avoidance coding, quadrature amplitude modulation 130 refers to a type of modulation scheme that allows for zero-crossing conditions. Example types of modulation schemes include four-level quadrature amplitude modulation (4-QAM) (or quadrature phase shift keying (QPSK)), sixteen-level quadrature amplitude modulation (16-QAM), 256-level quadrature amplitude modulation (256-QAM), and the like. Zero-crossing conditions may degrade the adjacent channel power and / or error vector magnitude performance of some types of wireless transceivers 120, such as the polar transceiver 126. For Figure 5 Example zero-crossing conditions are further described.

[0034] To avoid zero-crossing conditions, the modem 124 may perform various aspects of zero-crossing avoidance encoding for the quadrature amplitude modulation 130. In an example implementation, the modem 124 includes a zero-crossing avoidance encoder 132 that modifies symbols associated with the quadrature amplitude modulation 130 to avoid zero-crossing conditions. The zero-crossing avoidance encoder 132 may be incorporated into or implemented using software, firmware, hardware, fixed logic circuitry, or a combination thereof. Additionally or alternatively, the modem 124 may include a zero-crossing avoidance decoder (e.g., Figure 2 For Figure 2 The zero-crossing avoidance encoder 132 and the zero-crossing avoidance decoder are further described.

[0035] Generally speaking, the zero-crossing avoidance coding scheme enables the avoidance of zero-crossing conditions, which enables the wireless transceiver 120 to utilize quadrature amplitude modulation 130 in a manner that can meet adjacent channel power and error vector magnitude constraints. Figure 2 and Figure 3 Modem 124 and wireless transceiver 120 are further described.

[0036] Figure 2 An example modem 124 is illustrated that implements various aspects of zero-crossing avoidance coding for quadrature amplitude modulation. In the depicted configuration, the modem 124 includes components associated with a portion of the transmitter 202 (or transmit path) and components associated with a portion of the receiver 204 (or receive path). These components are associated with the digital portion of either the transmitter 202 or the receiver 204. Although Figure 2 2, but the transmitter 202 and the receiver 204 may include other components implemented as part of the wireless transceiver 120, such as for Figure 31. In general, the components of transmitter 202 and receiver 204 implemented as part of modem 124 may be incorporated into or implemented using software, firmware, hardware, fixed logic circuitry, or a combination thereof. In an example implementation, one or more of these components are implemented using a processor formed from an integrated circuit or memory, which may be part of a system on a chip.

[0037] The transmitter 202 is shown as including at least one serial-to-parallel converter 206, at least one zero-crossing avoidance encoder 132, and at least one modulation signal generator 208. The modulation signal generator 208 may include components such as a Cartesian-to-polar converter and / or a splitter. The receiver 204 includes at least one symbol generator 210, at least one zero-crossing avoidance decoder 212, and at least one parallel-to-serial converter 214.

[0038] During transmission, the modem 124 passes data 216 to the serial-to-parallel converter 206. The data 216 comprises a stream or sequence of information bits to be transmitted using the wireless transceiver 120. The serial-to-parallel converter 206 generates symbols 218 associated with the quadrature amplitude modulation 130. For example, the symbols 218 include symbols 218-1 ... 218-(M-1), 218-M, 218-(M+1) ... 218-N, where N and M represent positive integers. In this example, the variable M has a value between 1 and N.

[0039] The symbols 218 have a bit length that indicates the type of quadrature amplitude modulation 130 to be performed by the wireless transceiver 120. For example, according to four-level quadrature amplitude modulation, each symbol 218 may have two bits. For sixteen-level quadrature amplitude modulation, each symbol 218 may have four bits.

[0040] Symbols 218 may be grouped into multiple sets 220 of two consecutive symbols (or multiple pairs of consecutive symbols). Each symbol (except for the first symbol 218-1 and the last symbol 218-N) is associated with two sets 220. For example, symbols 218-(M-1) and 218-M represent a first set 220-1 of two consecutive symbols 218. Similarly, symbols 218-M and 218-(M+1) represent a second set 220-2 of two consecutive symbols 218. In this case, symbol 218-M is included as part of both the first set 220-1 and the second set 220-2. A zero-crossing condition 222 may be associated with at least one of the multiple sets 220 of two consecutive symbols 218.

[0041] To address this issue, the zero-crossing avoidance encoder 132 performs zero-crossing avoidance encoding to avoid the zero-crossing condition 222. Specifically, the zero-crossing avoidance encoder 132 generates a symbol 224 based on the symbol 218. The symbol 224 does not have a zero-crossing condition 226. In other words, each set 220 of two consecutive symbols 224 is not associated with a zero-crossing condition 222. To achieve this, the zero-crossing avoidance encoder 132 encodes some of the symbols 218 in a manner that avoids the zero-crossing condition 222. For example, the zero-crossing avoidance encoder 132 may change one of the symbols 218 within the set 220 to have a different symbol state (e.g., a different phase and optionally a different amplitude). For Figure 6-2 and Figure 7 This operation is further described.

[0042] The modulation signal generator 208 receives the symbols 224 and generates modulation signals 228-1 and 228-2. The modulation signals 228-1 and 228-2 may represent different types of signals, depending on the type of wireless transceiver 120. For a polar transceiver 126, the modulation signals 228-1 and 228-2 may represent amplitude modulated signals and phase modulated signals. For a Cartesian transceiver 128, the modulation signals 228-1 and 228-2 may represent in-phase signals and quadrature signals. Generally speaking, the modulation signals 228-1 and 228-2 represent coded digital signals that enable the wireless transceiver 120 to perform quadrature amplitude modulation 130.

[0043] During reception, the symbol generator 210 receives demodulated signals 230-1 and 230-2 from the wireless transceiver 120. The symbol generator 210 generates a symbol 232 based on the demodulated signals 230-1 and 230-2. The symbol 232 does not have a zero crossing condition 226. The zero crossing avoidance decoder 212 receives the symbol 232 and a correction list 234 that identifies the symbol 232 that has been modified using zero crossing avoidance coding. Using the correction list 234, the zero crossing avoidance decoder 212 generates a symbol 236 based on the symbol 232. Specifically, the zero crossing avoidance decoder 212 recovers the symbol 236 by inverting the zero crossing avoidance coding. At least one pair of symbols 236 is associated with the zero crossing condition 222. The parallel-to-serial converter 214 generates data 238 based on the symbol 236. The data 238 includes a stream or sequence of information bits. The modem 124 may pass the data 238 to the application processor 108 or another component of the modem 124. Figure 3 The transmission of data 216 via wireless transceiver 120 and the reception of data 238 via wireless transceiver 120 are further described.

[0044] Figure 3An example wireless transceiver 120 is illustrated. In the depicted configuration, wireless transceiver 120 includes components associated with a transmitter 202 and another portion of a receiver 204. These components are associated with the analog portion of either transmitter 202 or receiver 204. Transmitter 202 and receiver 204 are coupled to a first antenna 122-1 and a second antenna 122-2, respectively. In other implementations, transmitter 202 and receiver 204 may be connected to the same antenna 122 via a duplexer (not shown). Transmitter 202 is shown as including at least one quadrature amplitude modulator 302, at least one mixer 304, and at least one amplifier 306 (e.g., a power amplifier). Receiver 204 includes at least one amplifier 308 (e.g., a low-noise amplifier), at least one mixer 310, and at least one quadrature amplitude demodulator 312.

[0045] The wireless transceiver 120 may also include a local oscillator 314 (LO 314) coupled to the mixers 304 and 310. In some implementations, the mixers 304 and 310 may be integrated as part of the quadrature amplitude modulator 302 and the quadrature amplitude demodulator 312, respectively. In this case, the quadrature amplitude modulator 302 and the quadrature amplitude demodulator 312 may perform upconversion and downconversion, respectively. Although not explicitly shown, the wireless transceiver 120 may include other components such as digital-to-analog converters, analog-to-digital converters, phase shifters, filters, and switches.

[0046] In some implementations, wireless transceiver 120 is implemented using multiple circuits (e.g., multiple integrated circuits), such as transceiver circuit 316 and radio frequency front end (RFFE) circuit 318 (RFFE circuit 318). Thus, the components that form transmitter 202 and receiver 204 are distributed across these circuits. Figure 3 , transceiver circuitry 316 includes quadrature amplitude modulator 302 of transmitter 202, mixer 304 of transmitter 202, mixer 310 of receiver 204, and quadrature amplitude demodulator 312 of receiver 204. RF front-end circuitry 318 includes amplifier 306 of transmitter 202 and amplifier 308 of receiver 204.

[0047] In other implementations, the quadrature amplitude modulator 302 and / or the quadrature amplitude demodulator 312 (or some of its components) are implemented in another circuit separate from the transceiver circuit 316 and / or in the RF front-end circuit 318. Alternatively, the quadrature amplitude modulator 302 and / or the quadrature amplitude demodulator 312 (or some of its components) may be implemented in the modem 124.

[0048] During transmission, quadrature amplitude modulator 302 accepts modulated signals 228 - 1 and 228 - 2 from modem 124 and generates a transmit signal 320 , which is modulated according to quadrature amplitude modulation 130 . Figure 3 The modulated signals 228-1 and 228-2 shown in FIG can be Figure 2 3. The transmit signal 320 may represent an analog signal. The mixer 304 uses a local oscillator (LO) signal 322 provided by the local oscillator 314 to up-convert the transmit signal 320. The amplifier 306 amplifies the up-converted transmit signal 320. The transmitter 202 passes the signal 324 to the antenna 122-1 for transmission. The signal 324 represents a radio frequency transmit signal associated with wireless communication. In some example implementations, the signal 324 may be associated with a Bluetooth® wireless communication system. ® associated.

[0049] During reception, antenna 122-2 receives RF receive signal 326 and passes RF receive signal 326 to receiver 204. Amplifier 308 of receiver 204 amplifies RF receive signal 326, and mixer 310 downconverts the amplified RF receive signal 326 using local oscillator signal 322 to generate signal 328. Quadrature amplitude demodulator 312 demodulates signal 328 to generate demodulated signals 230-1 and 230-2. Demodulated signals 230-1 and 230-2 may represent polarity signals (e.g., amplitude and phase) associated with polar transceiver 126 or in-phase and quadrature signals associated with Cartesian transceiver 128. Wireless transceiver 120 passes demodulated signals 230-1 and 230-2 to modem 124, as Figure 2 shown.

[0050] Figure 3 One example configuration of the wireless transceiver 120 is illustrated. Other configurations of the wireless transceiver 120 may support multiple frequency bands and share the antenna 122 across multiple transceivers. One of ordinary skill in the art will appreciate the various other configurations in which the wireless transceiver 120 may be implemented. For example, the wireless transceiver 120 may be implemented as a polar transceiver 126 or a Cartesian transceiver 128. The wireless transceiver 120 may also be implemented as a direct conversion transceiver or a superheterodyne transceiver. Some implementations of the computing device 102 may implement portions of the quadrature amplitude modulator 302 and / or the quadrature amplitude demodulator 312 within the modem 124. Figure 4 Aspects of quadrature amplitude modulation 130 are further described.

[0051] Figure 4An example constellation diagram 400 (or polar diagram) associated with 16-level quadrature amplitude modulation is illustrated. Constellation diagram 400 is depicted for an in-phase axis 402 and a quadrature axis 404. Points (e.g., dots or circles) within constellation diagram 400 represent different symbol states 406 associated with 16-level quadrature amplitude modulation. Each symbol state includes four information bits according to the 16-level quadrature amplitude modulation. Although described with respect to 16-level quadrature amplitude modulation, the techniques for zero-crossing avoidance encoding are applicable to any type of quadrature amplitude modulation that may result in a zero-crossing condition 222.

[0052] Each symbol state 406 can be represented by a unique complex number. For example, each symbol state 406 can be associated with an in-phase value (e.g., a real number) and a quadrature value (e.g., an imaginary number). Alternatively, each symbol state 406 can be represented by an amplitude 408 and a phase 410. The amplitude 408 represents the distance between the symbol state 406 and the origin 412 of the constellation diagram 400. The origin 412 is the point where the in-phase and quadrature values ​​are equal to zero. The phase 410 represents the angle between the symbol state 406 and the positive portion of the event axis 402 (e.g., the portion of the event axis 402 to the right of the origin 412).

[0053] Each symbol carried by the RF signal 324 or 326 represents one of the symbol states 406 within the constellation diagram 400. The symbol states 406 of the constellation diagram 400 represent ideal versions of the symbols being transmitted or received. In practice, the symbols being transmitted or received may have amplitudes and / or phases that vary by some amount from the amplitudes 408 and / or phases 410 of the expected symbol states 406. Such variations may be caused by components within the wireless transceiver 120 and / or by non-ideal conditions within the environment. For example, noise, clipping, carrier leakage, or phase noise may cause a symbol to vary by some amount from the expected symbol state 406.

[0054] Throughout this disclosure, symbols carried by radio frequency signals 324 or 326, or represented by 218, 224, 232, and 236, may be described as being approximately equal to (or represented by) a particular symbol state 406. In this context, the term "approximately" may account for some variation, as described above. Generally, if a receiving entity can associate a symbol with the appropriate symbol state 406, then the symbol may represent a particular symbol state 406. The amount of variation that may be covered by the term "approximately" may depend on the distance between adjacent symbol states 406 within the constellation 400. Different levels of quadrature amplitude modulation 130 may allow for different amounts of variation. For Figure 5 Other aspects of the constellation diagram 400 are further described.

[0055] Figure 5 An example zero crossing condition 222 is illustrated in the constellation diagram 400. Figure 54 . A plurality of signal traces 502 (e.g., signal traces 502-1, 502-2, 502-3, and 502-4) are shown in FIG. A signal trace 502 (or state transition) represents a transition from a first symbol state 406 to a second symbol state 406. A zero-crossing condition 222 is associated with a signal trace 502 passing through the origin 412 of the constellation diagram 400. At the origin 412, the amplitude 408 of the signal trace 502 is zero. Explained another way, two symbol states 406 are associated with a zero-crossing condition 222 if the absolute value of the phase difference between the two symbol states 406 is equal to 180 degrees. Considering two consecutive symbols representing these two symbol states, a zero-crossing condition 222 may occur if the absolute value of the phase difference between these consecutive symbols is approximately equal to 180 degrees. Generally speaking, the term "approximately" allows for some variation between symbols and representative symbol states 406. In an example implementation, “substantially” may mean that the absolute value of the phase difference may be within ±1 degree of 180 degrees (eg, within ±0.5 degrees of 180 degrees).

[0056] In constellation diagram 400, an example signal trace 502 is shown between four symbol states 406 in the upper left quadrant of constellation diagram 400 and four symbol states 406 in the lower right quadrant of constellation diagram 400. Signal trace 502 is represented by a line with an arrow. The end of the line opposite the arrow is located at first symbol state 406, which may represent the state of the first symbol (e.g., the start symbol) within a set 220 of two consecutive symbols. The arrow is located at second symbol state 406, which may represent the state of the second symbol (e.g., the end symbol) within the set 220 of two consecutive symbols. Within the set 220, the first symbol precedes the second symbol.

[0057] Signal traces 502-1, 502-2, 502-3, and 502-4 cause zero-crossing conditions 222. The first signal trace 502-1 is between symbol states 406 having binary values ​​(0000) and (1010). The second signal trace 502-2 is between symbol states 406 having binary values ​​(0100) and (1110). The third signal trace 502-3 is between symbol states 406 having binary values ​​(0101) and (1111). The fourth signal trace 502-4 is between symbol states 406 having binary values ​​(0001) and (1011). Although not explicitly shown, there are two additional signal traces 502 that cause zero-crossing conditions 222 between symbol states 406 in the upper left quadrant and the lower right quadrant. These include a signal trace 502 between symbol states 406 having binary values ​​of (0000) and (1111) and another signal trace 502 between symbol states 406 having binary values ​​of (0101) and (1010).

[0058] For 16-QAM, there are six possible signal trajectories 502 that begin in each quadrant of the constellation diagram 400 and cause a zero-crossing condition 222. Thus, 24 of the 256 total signal trajectories 502 may cause a zero-crossing condition 222. The remaining 232 signal trajectories 502 do not cause a zero-crossing condition 222 (e.g., avoid the zero-crossing condition 222).

[0059] Techniques associated with zero-crossing avoidance coding modify the symbol state 406 of the symbol 218 in a manner that avoids any signal trace 502 associated with the zero-crossing condition 222, such as for Figure 6-1 and Figure 6-2 Further described.

[0060] Figure 6-1 An example sequence 602 of symbols 218 with a zero-crossing condition 222 is illustrated. The serial-to-parallel converter 206 may generate the sequence 602 of symbols 218 based on the data 216, such as Figure 2 As shown. In this example, sequence 602 includes symbols 218-1, 218-2, 218-3, 218-4, 218-5, and 218-6. Symbols 218-1 through 218-6 are ordered in time, with symbol 218-1 appearing first and symbol 218-6 appearing last. In other words, symbol 218-1 precedes symbol 218-2, which precedes symbol 218-3, which precedes symbol 218-3, which precedes symbol 218-4, which precedes symbol 218-4, which precedes symbol 218-5, and which precedes symbol 218-5.

[0061] Symbols 218-1 through 218-6 may be mapped to corresponding symbol states 406 based on binary values. Symbol 218-1 is represented by a symbol state 406 having a binary value of (1000). Symbol 218-2 is represented by a symbol state 406 having a binary value of (1100). Symbols 218-3 and 218-4 are represented by symbol states 406 having binary values ​​of (0111) and (0101), respectively. Symbols 218-5 and 218-6 are represented by symbol states 406 having binary values ​​of (1111) and (1110), respectively.

[0062] Constellation diagram 600-1 illustrates signal traces 502 between consecutive symbols 218 within sequence 602. A first signal transition 502-1 occurs between symbol states 406 associated with symbols 218-1 and 218-2. Symbols 218-1 and 218-2 represent a first set 220 of consecutive symbols 218 within sequence 602. A second signal transition 502-2 occurs between symbol states 406 associated with symbols 218-2 and 218-3. Symbols 218-2 and 218-3 represent a second set 220 of consecutive symbols 218 within sequence 602. A third signal transition 502-3 occurs between symbol states 406 associated with symbols 218-3 and 218-4. Symbols 218-3 and 218-4 represent a third set 220 of consecutive symbols 218 within sequence 602. A fourth signal transition 502-4 occurs between symbol states 406 associated with symbols 218-4 and 218-5. Symbols 218-4 and 218-5 represent a fourth set 220 of consecutive symbols 218 within the sequence 602. A fifth signal transition 502-5 occurs between symbol states 406 associated with symbols 218-5 and 218-6. Symbols 218-5 and 218-6 represent a fifth set 220 of consecutive symbols 218 within the sequence 602.

[0063] Signal transitions 502-1, 502-2, 502-3, and 502-5 are not associated with zero-crossing conditions 222. This is because the absolute value of the phase difference between corresponding consecutive symbol pairs 218 is substantially different from 180 degrees. Generally, the term "substantially different" means that the symbol states 406 represented by two consecutive symbols 218 have a phase difference that is not equal to 180 degrees (e.g., the symbol states 406 do not have opposite phases). For some levels of quadrature amplitude modulation 130, the term "substantially different" may mean that the absolute value of the phase difference between corresponding consecutive symbol pairs 218 varies from 180 degrees by at least ±0.5 degrees (e.g., by ±1 degree, ±2 degrees, ±5 degrees, ±10 degrees, or more). The amount of variation associated with the term "substantially different" may depend on the type of quadrature amplitude modulation 130. Generally, the amount of variation may be greater for lower levels of quadrature amplitude modulation (e.g., 4-QAM), while the amount of variation may be smaller for higher levels of quadrature amplitude modulation (e.g., 256-QAM).

[0064] In contrast, signal transition 502-4 is associated with a zero-crossing condition 222. This is because the absolute value of the phase difference 604-1 between symbols 218-4 and 218-5 is approximately equal to 180 degrees. Generally speaking, the term "approximately" means that some variation between symbols and representative symbol states 406 may be allowed. In an example implementation, "approximately" may mean that the absolute value of the phase difference may be within ±1 degree of 180 degrees (e.g., within ±0.5 degrees of 180 degrees). Explained another way, the symbol states 406 represented by two consecutive symbols 218 have a phase difference equal to 180 degrees. To avoid the zero-crossing condition 222 associated with fourth signal trace 502-4, computing device 102 may employ zero-crossing avoidance coding, such as for Figure 6-2 Further described.

[0065] Figure 6-2 An example sequence 606 of symbols 224 encoded using zero-crossing avoidance coding is illustrated. The zero-crossing avoidance encoder 132 generates the sequence 606 of symbols 224 based on the sequence 602 of symbols 218 provided by the serial-to-parallel converter 206. In this example, the sequence 606 includes symbols 224-1, 224-2, 224-3, 224-4, 224-5, and 224-6. The symbols 224-1 through 224-6 are ordered in time, with symbol 224-1 occurring first and symbol 224-6 occurring last. In other words, symbol 224-1 precedes symbol 224-2, symbol 224-2 occurs before symbol 224-3, symbol 224-4 occurs before symbol 224-5, and symbol 224-5 occurs before symbol 224-6. Symbols 224-1 through 224-6 represent the symbols that have passed through the zero-crossing avoidance encoder 132. Figure 6-1 The symbols 224-1 through 224-6 may or may not have similar symbol states 406 as the corresponding symbols 218-1 through 218-6, as further explained below.

[0066] With zero-crossing avoidance coding, symbol pairs that do not cause zero-crossing condition 222 remain unchanged. Thus, symbols 224-1 to 224-4 have the same Figure 6-1 The symbols 218-1 to 218-4 are the same as the symbol state 406. In order to avoid Figure 6-1224-5 is modified 608 relative to symbol 218-5 to avoid the zero-crossing condition 222 associated with signal trace 502-4 in FIG. Explained another way, symbol 224-5 represents an encoded version of symbol 218-5 that avoids the zero-crossing condition 222. Specifically, symbol 224-5 has a symbol state 406 that has a different phase 410 than the symbol state 406 associated with symbol 218-5. The modified phase 410 causes the absolute value of the phase difference 604-2 between symbols 224-4 and 224-5 to be substantially different from 180 degrees. As explained above, the term "substantially different" may mean that the absolute value of the phase difference between corresponding consecutive symbol pairs 218 varies from 180 degrees by at least ±0.5 degrees (e.g., by ±1 degree, ±2 degrees, ±5 degrees, ±10 degrees, or more). The amount of variation associated with the term "substantially different" may depend on the type of quadrature amplitude modulation 130.

[0067] There are various ways in which zero-crossing avoidance encoding can modify the phase 410 of symbol 218-5 to avoid the zero-crossing condition 222 and generate symbol 224-5. In one example, the symbol state 406 of symbol 224-5 is any other symbol state 406 that is not opposite in phase to the symbol state 406 of symbol 224-4. Specifically, the symbol state 406 of symbol 224-5 can be any symbol state 406 other than those associated with the binary values ​​(1111) and (1010). Optionally, the amplitude 408 of symbol 218-5 can also be modified.

[0068] In a first example, the symbol state 406 of symbol 218-5 is in the same quadrant of constellation diagram 600-2 as the symbol state 406 of symbol 224-5. In this example, the symbol state 406 of symbol 224-5 is shifted to an adjacent symbol state 406, such as one of the symbol states 406 represented by the binary values ​​(1110) or (1011). In a second example, the symbol state 406 of symbol 224-5 is in a different quadrant than the symbol state 406 of symbol 224-5 and the symbol state 406 of symbol 218-4. For example, the symbol state 406 of symbol 224-5 is in the upper right quadrant of constellation diagram 600-2 or the lower left quadrant of constellation diagram 600-2. In a third example, the symbol state 406 of symbol 224-5 is in the same quadrant as the symbol state 406 of symbol 224-4. In this example, the symbol state 406 for the symbol 224 - 5 is in the upper left quadrant of the constellation diagram 600 - 2 .

[0069] exist Figure 6-2, the symbol state 406 represented by symbol 224-5 is modified 608 to the symbol state 406 represented by the preceding symbol 218-4. In this manner, the symbol state 406 of symbol 224-5 has the same amplitude 408 and the same phase 410 as the symbol state 406 of symbol 224-4. Explained another way, the absolute value of the phase difference 604-2 between the symbol states 406 represented by symbols 224-5 and 224-4 is equal to zero. In this case, the amplitude 408 of the symbol state 406 of symbol 224-5 is unchanged relative to the amplitude 408 of the symbol state 406 of symbol 218-5. By adjusting at least the phase 410 of the symbol state 406 of symbol 224-5 relative to the phase 410 of the symbol state 406 of symbol 218-5, a zero crossing condition is avoided in the sequence 606. Figure 7 Aspects of zero-crossing avoidance encoding are further described.

[0070] Figure 7 An example scheme 700 implemented by the zero-crossing avoidance encoder 132 is illustrated. At 702, the zero-crossing avoidance encoder 132 receives the symbol 218-M and the symbol 218-(M+1) from the serial-to-parallel converter 206. The value M represents a positive integer incremented between 1 and N-1 by the zero-crossing avoidance encoder 132. The symbols 218-M and 218-(M+1) represent a set 220 of two consecutive symbols 218 within the sequence 602 (e.g., a pair of consecutive symbols 218 within the sequence 602).

[0071] In this example implementation, the zero-crossing avoidance encoder 132 outputs the symbol 218-M as part of the encoded data sequence 702. At 704, the zero-crossing avoidance encoder 132 determines whether the given symbols 218-M and 218-(M+1) are associated with the zero-crossing condition 222. If the symbols 218-M and 218-(M+1) are not associated with the zero-crossing condition 222, the symbol 218-(M+1) remains unchanged. If the symbols 218-M and 218-(M+1) are associated with the zero-crossing condition 222, the zero-crossing avoidance encoder 132 performs zero-crossing avoidance encoding at 706.

[0072] As part of the zero-crossing avoidance encoding, at least the phase 410 of symbol 218-(M+1) is modified or altered such that the absolute value of the phase difference 604 between symbols 218-M and 218-(M+1) is substantially different than 180 degrees. The amplitude 408 of symbol 218-(M+1) may optionally be modified. In an example implementation, the zero-crossing avoidance encoding causes the modified symbol 218-(M+1) to have the same symbol state as symbol 218-M (e.g., to have approximately the same amplitude 408 and approximately the same phase 410 as symbol 218-M). In another example implementation, the zero-crossing avoidance encoding causes symbol 218-(M+1) to represent a symbol state 406 in the same quadrant as the symbol state 406 of symbol 218-M. In this case, the phase 410 of the symbol state 406 represented by symbol 218-(M+1) may be modified, and the amplitude 408 of the symbol state 406 may remain unchanged.

[0073] Additionally, the zero-crossing avoidance encoder 132 updates the correction list 234 based on the symbol identifier 708 associated with the symbol 218-(M+1). The symbol identifier 708 may represent the position of the symbol 218-(M+1) within the sequence 602. In other words, the symbol identifier 708 may represent the value M+1.

[0074] In some implementations, the correction list 234 may include additional information to enable the symbol 218-(M+1) to be recovered or decoded by the receiving entity. For example, the correction list 235 may include information about the type of zero-crossing avoidance coding. A first type of zero-crossing avoidance coding may refer to the zero-crossing avoidance encoder 132 encoding the symbol 218-(M+1) to have the same phase 410 as the symbol 218-M without adjusting the amplitude 408 of the symbol 218-(M+1). A second type of zero-crossing avoidance coding may refer to the zero-crossing avoidance encoder 132 encoding the symbol 218-(M+1) to have the same phase 410 as the symbol 218-M and the same amplitude 408 as the symbol 218-M. Other types of zero-crossing avoidance coding are also possible, including for Figure 6-2 An example of description.

[0075] At 708, the zero-crossing avoidance encoder 132 increments M and repeats the process at 702 until M equals N. During subsequent iterations, the previous symbol 218-(M+1) becomes the symbol 218-M. In this case, the symbol 218-M may represent a modified version or the original version of the symbol 218-(M+1) associated with the previous iteration.

[0076] Over time, the zero-crossing avoidance encoder 132 evaluates each pair of consecutive symbols 218 to determine whether each pair is associated with a zero-crossing condition 222. If the pair of consecutive symbols 218 is not associated with a zero-crossing condition 222, the second symbol 218 within the pair remains unchanged. If the pair of consecutive symbols 218 is associated with a zero-crossing condition 222, the second symbol 218 is modified to circumvent the zero-crossing condition 222. The unchanged and modified symbols 224 are captured as part of the encoded data sequence 702 and are represented by symbols 224. The zero-crossing avoidance encoder 132 generates a correction list 234 to identify which symbols 224 within the encoded data sequence 702 are modified by the zero-crossing avoidance encoding at 706. For Figure 8 Aspects of zero-crossing avoidance encoding are further described.

[0077] Figure 8 An example transaction diagram 800 is illustrated between a sending entity 802 and a receiving entity 804. The sending entity 802 may represent Figure 1 Generally speaking, the sending entity 802 includes at least Figure 2 and Figure 3 The sending entity 802 may or may not include Figure 2 and Figure 3 Receiver 204.

[0078] The receiving entity 804 may indicate Figure 1 Generally speaking, the receiving entity 804 includes at least Figure 2 and Figure 3 The receiving entity 804 may or may not include Figure 2 and Figure 3 802. In some example implementations, the transmitting entity 802 represents a wireless earbud and the receiving entity 804 represents another computing device, such as a smartphone.

[0079] At 806, the sending entity 802 performs zero-crossing avoidance coding, such as for Figure 7 In other words, the transmitting entity 802 generates the symbols 224 (or the encoded data sequence 702) without the zero-crossing condition 226. Explained another way, the phase difference within each set 220 of two consecutive symbols 224 is substantially different from 180 degrees.

[0080] At 808, the transmitting entity 802 performs quadrature amplitude modulation 130 using the wireless transceiver 120. In an example implementation, the wireless transceiver 120 may be a polar transceiver 126 or a Cartesian transceiver 128.

[0081] At 810, the transmitting entity 802 sends a message 812 to the receiving entity 804. The message 812 includes data 814 represented by the symbols 224. The message 812 may also include a correction list 234 to at least identify the symbols 224 modified by the zero-crossing avoidance encoding at 806. Alternatively, the correction list 234 may be communicated using another message other than the message 812.

[0082] The receiving entity 804 receives the message 812. At 816, the receiving entity 804 performs quadrature amplitude demodulation. At 818, the receiving entity 804 performs zero-crossing avoidance decoding based on the correction list 234. In general, the zero-crossing avoidance decoding recovers the original symbol 218 associated with the at least one zero-crossing condition 222. In some implementations, the message 812 may represent a protocol data unit (PDU), such as for Figure 9 Further described.

[0083] Figure 9 An example protocol data unit 902 according to zero-crossing avoidance coding for quadrature amplitude modulation is illustrated. In an example implementation, protocol data unit 902 includes a header 904, a payload 906, a correction list 234, and a checksum 908. Header 904 may include information such as a preamble, an access code, or the length of payload 906. In some embodiments, correction list 234 may be provided as part of header 904. Payload 906 includes symbols 224-1, 224-2, ..., 224-N, which are encoded using zero-crossing avoidance coding. Checksum 908 may include a number representing a checksum or codeword associated with a cyclic redundancy check (CRC) for error detection and / or correction.

[0084] Correction list 234 can be implemented as a binary correction list 910 or a quadrature amplitude modulation correction list 912 (QAM correction list 912). Binary correction list 910 includes bits 914-1, 914-2, ..., 914-N. The number of bits within binary correction list 910 may be equal to the number of symbols 224 within payload 906 (e.g., equal to the value represented by N). Each bit 914 within binary correction list 910 is associated with one of symbols 224-1 through 224-N. For example, bit 914-1 is associated with symbol 224-1, and bit 914-N is associated with symbol 224-N. The value of bit 914 indicates whether the corresponding symbol 224 has been modified by zero-crossing avoidance coding. For example, a value of "1" may indicate that the corresponding symbol 224 has been modified (e.g., encoded using zero-crossing avoidance coding), while a value of "0" may indicate that the corresponding symbol 224 has not been modified (e.g., remains unchanged using zero-crossing avoidance coding).

[0085] The quadrature amplitude modulation correction list 912 includes symbols 916-1, 916-2, ..., and 916-(K+1), where K represents the number of modified symbols within the payload 906. Each symbol 916 represents the position of a symbol 224 modified using zero-crossing avoidance coding within the payload 906. To avoid zero-crossing conditions 222 within the quadrature amplitude modulation correction list 912, symbol pairs that avoid zero-crossing conditions 222 may be used to represent the position of the symbol 224 within the payload 906.

[0086] Figure 10 and Figure 11 is a flow chart illustrating example processes 1000 and 1100 for performing various aspects of zero-crossing avoidance encoding or decoding. Processes 1000 and 1100 are described in terms of a set of blocks that specify operations that may be performed. However, the operations are not necessarily limited to Figure 10 or Figure 11 1000 and 1100 or an alternative process. The operations represented by the illustrated blocks of processes 1000 and 1100 may be performed at least in part by the modem 124. More specifically, the operations of process 1000 may be performed at least in part by the zero-crossing avoidance encoder 132. Furthermore, the operations of process 1100 may be performed at least in part by the zero-crossing avoidance decoder 212.

[0087] exist Figure 10 At 1002 in FIG. 1 , a first pair of consecutive symbols associated with quadrature amplitude modulation is received. For example, the zero crossing avoidance encoder 132 receives a first pair of consecutive symbols from the serial to parallel converter 206, such as Figure 2 The first pair of consecutive symbols may include Figure 7 The symbols 218-M and 218-(M+1) are shown in FIG.

[0088] At 1004, the first symbol is output as part of the encoded data sequence. For example, the zero-crossing avoidance encoder 132 outputs the symbol 218-M as part of the encoded data sequence 702, as shown in FIG. Figure 7 If the symbol 218-M represents the first symbol in the sequence 602 (e.g., symbol 218-1), the symbol state 406 of the symbol 218-M may remain unchanged. If the symbol 218-M represents another symbol in the sequence 602 (e.g., symbol 218-2, 218-3, 218-4, or 218-5), the zero-crossing avoidance encoder 132 may or may not have modified the symbol state 406 of the symbol 218-M to avoid the zero-crossing condition 222. The modem 124 passes the encoded data sequence 702 to the modulation signal generator 208, as shown. Figure 2An example coded data sequence 702 is represented by Figure 6-2 The sequence 606 in is represented.

[0089] At 1006, it is determined that the first pair of consecutive symbols are associated with a zero crossing condition. For example, the zero crossing avoidance encoder 132 determines that the first pair of consecutive symbols are associated with the zero crossing condition 222, such as Figure 7 The zero-crossing condition 222 represents the signal trajectory 502 between two symbol states 406 of consecutive symbols 218, which passes through the origin 412 of the constellation diagram 400. Figure 5 22. Explained another way, the first pair of consecutive symbols is associated with the zero-crossing condition 222 because the symbol states 406 of the first pair of consecutive symbols have opposite phases. In this case, the absolute value of the phase difference between the first pair of consecutive symbols is approximately equal to 180 degrees.

[0090] At 1008, the second symbol is modified based on the determination to generate a modified symbol that avoids the zero crossing condition. For example, the zero crossing avoidance encoder 132 modifies the second symbol 218-(M+1) based on the determination to avoid the zero crossing condition 222, as shown in FIG. Figure 7 In general, the zero-crossing avoidance encoder 132 modifies the phase 410 of at least the second symbol 218-(M+1) so that the absolute phase difference between the first pair of consecutive symbols is substantially different from 180 degrees (e.g., ±0.5 degrees or more for some types of quadrature amplitude modulation 130).

[0091] In some example implementations, the zero-crossing avoidance encoder 132 modifies the second symbol 218-(M+1) so that the first symbol 218-M and the second symbol 218-(M+1) have approximately the same phase 410. In this case, the amplitude 408 of the second symbol 218-(M+1) may be unchanged. In another example implementation, the zero-crossing avoidance encoder 132 may further modify the second symbol 218-(M+1) so that the first symbol 218-M and the second symbol 218-(M+1) have approximately the same amplitude 408. Figure 6-2 In the example shown in , symbol 224 - 5 has the same symbol state 406 as symbol 224 - 4 that precedes symbol 224 - 5 .

[0092] Although not explicitly shown, process 1000 may also include generating a correction list indicating that the second symbol has been modified to avoid a zero crossing condition. For example, zero crossing avoidance encoder 132 generates correction list 234. Correction list 234 indicates that second symbol 218-(M+1) has been modified to avoid a zero crossing condition 222. Correction list 234 may be binary correction list 910 or quadrature amplitude modulation correction list 912, as for Figure 9The correction list 234 at least informs the receiving entity which symbols are encoded to avoid zero-crossing conditions.

[0093] In some cases, the receiving entity is configured to perform appropriate decoding operations to recover previously encoded symbols based on the correction list. In such cases, correction list 234 need not include decoding instructions. In other cases, the receiving entity may not be aware of the decoding operations, and correction list 234 may include decoding information to enable the receiving entity to correctly recover previously encoded symbols.

[0094] exist Figure 11 At 1102 in FIG. 1 , a first pair of consecutive symbols associated with quadrature amplitude demodulation is received. The first pair of consecutive symbols includes a first symbol and a second symbol. For example, the zero crossing avoidance decoder 212 receives the first pair of consecutive symbols 232, such as Figure 2 As shown, the first pair of consecutive symbols 232 is associated with quadrature amplitude demodulation. Symbols 232 represent the encoded data sequence without zero crossing conditions 226.

[0095] At 1104, a correction list is received that identifies the second symbol in the first pair of consecutive symbols as having been modified using zero-crossing avoidance coding. For example, the zero-crossing avoidance decoder 212 receives a correction list 234 that identifies the second symbol in the first pair of consecutive symbols as having been modified using zero-crossing avoidance coding. The correction list 234 can be the binary correction list 910 or the quadrature amplitude modulation correction list 912, such as Figure 9 shown.

[0096] At 1106, the second symbol is modified based on the correction list to invert the zero-crossing avoidance coding and generate a modified symbol associated with the zero-crossing condition. For example, the zero-crossing avoidance decoder 212 modifies the second symbol based on the correction list 234 to invert the zero-crossing avoidance coding (e.g., restore the symbol 218) and generate the modified symbol 236 associated with the zero-crossing condition 222.

[0097] At 1108, the first symbol and the modified symbol are output as part of the decoded data sequence. For example, the zero crossing avoidance decoder 212 outputs the first symbol and the modified symbol as part of the decoded data sequence, as indicated by Figure 2 Indicated by symbol 236 in .

[0098] In general, techniques for zero-crossing avoidance coding may be implemented using any type of wireless transceiver 120. Example wireless transceivers 120 may include those that may not meet performance metrics under zero-crossing conditions 222, such as polar transceivers 126. Other example wireless transceivers 120 include wireless transceivers 120 that may meet performance metrics under zero-crossing conditions 222, such as Cartesian transceivers 128.

[0099] Some aspects are described below.

[0100] Aspect 1: A device comprising:

[0101] A polar transceiver configured to:

[0102] coupled to an antenna; and

[0103] Data including a plurality of symbols associated with quadrature amplitude modulation is transmitted via the antenna, the plurality of symbols including a plurality of sets of two consecutive symbols, an absolute value of a phase difference between the two consecutive symbols within each of the plurality of sets being substantially different from 180 degrees.

[0104] Aspect 2: The apparatus according to aspect 1, wherein:

[0105] The plurality of symbols includes a first symbol, a second symbol, and a third symbol;

[0106] The first symbol, the second symbol and the third symbol represent consecutive symbols;

[0107] The first symbol precedes the second symbol;

[0108] The second symbol precedes the third symbol;

[0109] A first set of the plurality of sets includes the first symbol and the second symbol; and

[0110] A second set of the plurality of sets includes the second symbol and the third symbol.

[0111] Aspect 3: The apparatus according to aspect 1 or 2, wherein the absolute value of the phase difference differs from 180 degrees by at least ±0.5 degrees.

[0112] Aspect 4: The apparatus according to aspect 3, wherein the absolute value of the phase difference differs from 180 degrees by at least ±1 degree.

[0113] Aspect 5: The apparatus of any preceding aspect, wherein the polar transceiver is configured to transmit a correction list identifying symbols within the plurality of symbols that have been encoded to avoid a zero-crossing condition.

[0114] Aspect 6: The apparatus according to aspect 5, wherein:

[0115] The two consecutive symbols include a first symbol and a second symbol;

[0116] The first symbol precedes the second symbol; and

[0117] Each of the symbols that has been encoded to avoid the zero-crossing condition represents the second symbol within one of the multiple sets and has a symbol state in the same quadrant of the constellation diagram as the first symbol within the one of the multiple sets.

[0118] Aspect 7: The apparatus according to aspect 6, wherein the phases of the first symbol and the second symbol within the one of the plurality of sets are approximately equal.

[0119] Aspect 8: The apparatus of aspect 6 or 7, wherein the first symbol and the second symbol within the one of the plurality of sets are approximately equal in magnitude.

[0120] Aspect 9: The apparatus according to any one of aspects 5 to 8, wherein:

[0121] The correction list comprises a plurality of bits; and

[0122] The number of the plurality of bits is equal to the number of the plurality of symbols.

[0123] Aspect 10: The apparatus according to any one of aspects 5 to 9, wherein:

[0124] The correction list includes other symbols associated with the quadrature amplitude modulation; and

[0125] The number of the further symbols is equal to the number of the symbols that have been encoded plus one.

[0126] Aspect 11: The apparatus of any one of aspects 5 to 10, wherein the zero-crossing condition represents a signal transition through an origin of a constellation diagram between symbol states associated with two symbols.

[0127] Aspect 12: The apparatus according to any preceding aspect, wherein:

[0128] The device includes wireless earbuds; and

[0129] The wireless earbud includes the polarity transceiver.

[0130] Aspect 13: The apparatus according to aspect 12, wherein:

[0131] The wireless earbuds are configured to transmit with Bluetooth ® associated radio frequency signals; and

[0132] The radio frequency signal includes the data.

[0133] Aspect 14: A device comprising:

[0134] A wireless transceiver configured to:

[0135] coupled to an antenna;

[0136] communicating, via the antenna, data comprising a plurality of symbols associated with quadrature amplitude modulation and encoded using zero-crossing avoidance coding; and

[0137] A correction list is communicated via the antenna, the correction list identifying symbols of the plurality of symbols that have been encoded using the zero-crossing avoidance coding.

[0138] Aspect 15: The apparatus according to aspect 14, wherein:

[0139] The plurality of symbols comprises a plurality of sets of two consecutive symbols; and

[0140] The two consecutive symbols within each set of the plurality of sets do not have opposite phases.

[0141] Aspect 16: The apparatus according to aspect 15, wherein an absolute value of the phase difference between the two consecutive symbols in each of the plurality of sets is substantially different from 180 degrees.

[0142] Aspect 17: The apparatus according to any one of aspects 14 to 16, wherein each of the symbols that has been encoded using the zero-crossing avoidance coding has substantially the same phase as another symbol preceding the symbol within the plurality of symbols.

[0143] Aspect 18: The apparatus of aspect 17, wherein each of the symbols that has been encoded using the zero-crossing avoidance encoding has substantially the same amplitude as the another symbol preceding the symbol within the plurality of symbols.

[0144] Aspect 19: The apparatus according to any one of aspects 14 to 18, wherein:

[0145] The correction list includes a plurality of bits;

[0146] The number of the plurality of bits is equal to the number of the plurality of symbols;

[0147] At least one bit of the plurality of bits has a first value indicating that a corresponding symbol of the plurality of symbols has been encoded using the zero-crossing avoidance encoding; and

[0148] At least one other bit of the plurality of bits has a second value indicating that a corresponding symbol of the plurality of symbols has not been encoded using the zero-crossing avoidance encoding.

[0149] Aspect 20: The apparatus according to any one of aspects 14 to 18, wherein:

[0150] The correction list includes other symbols associated with the quadrature amplitude modulation; and

[0151] The number of the further symbols is equal to the number of the symbols that have been encoded using the zero-crossing avoidance encoding plus one.

[0152] Aspect 21: The apparatus of any one of aspects 14 to 20, wherein the wireless transceiver is configured to communicate, via the antenna, a protocol data unit comprising the data and the correction list.

[0153] Aspect 22: The apparatus according to any one of aspects 14 to 21, wherein the wireless transceiver comprises:

[0154] a transmitter configured to transmit the data and the correction list; or

[0155] A receiver is configured to receive the data and the correction list.

[0156] Aspect 23: The apparatus according to any one of aspects 14 to 22, wherein the wireless transceiver comprises:

[0157] a polar transceiver configured to perform said quadrature amplitude modulation based on an amplitude and a phase associated with said plurality of symbols; or

[0158] A Cartesian transceiver is configured to perform the quadrature amplitude modulation based on in-phase values ​​and quadrature values ​​associated with the plurality of symbols.

[0159] Aspect 24: The apparatus according to any one of aspects 14 to 23, further comprising:

[0160] A modem, the modem being configured to:

[0161] encoding the data using zero-crossing avoidance coding; and

[0162] generating a modulated signal based on the encoded data; and

[0163] The wireless transceiver is configured to transmit a radio frequency signal including the data, the radio frequency signal being modulated according to quadrature amplitude modulation based on the modulation signal.

[0164] Aspect 25: A method for performing zero-crossing avoidance coding, the method comprising:

[0165] accepting a first pair of consecutive symbols associated with quadrature amplitude modulation, the first pair of consecutive symbols comprising a first symbol and a second symbol;

[0166] outputting the first symbol as part of an encoded data sequence;

[0167] determining that the first pair of consecutive symbols is associated with a zero-crossing condition; and

[0168] Based on the determination, the second symbol is modified to generate a modified symbol that avoids the zero-crossing condition.

[0169] Aspect 26: The method according to aspect 25, wherein the modification of the second symbol comprises: modifying the second symbol so that an absolute value of a phase difference between the first symbol and the second symbol is substantially different from 180 degrees.

[0170] Aspect 27: The method according to aspect 26, wherein the modification of the second symbol comprises: modifying the second symbol to have the same phase as the first symbol.

[0171] Aspect 28: The method according to any one of aspects 25 to 27, further comprising:

[0172] A correction list is generated indicating that the second symbol has been modified to avoid the zero-crossing condition.

[0173] Aspect 29: The method according to any one of aspects 25 to 28, further comprising:

[0174] accepting a second pair of consecutive symbols associated with the quadrature amplitude modulation, the second pair of consecutive symbols comprising the modified symbol and a third symbol;

[0175] outputting the modified symbol as part of the encoded data sequence; and

[0176] It is determined that the second pair of consecutive symbols is not associated with the zero-crossing condition.

[0177] Aspect 30: A computer-readable storage medium comprising instructions that, in response to execution by a processor, cause the processor to:

[0178] accepting a first pair of consecutive symbols associated with quadrature amplitude modulation, the first pair of consecutive symbols comprising a first symbol and a second symbol;

[0179] outputting the first symbol as part of an encoded data sequence;

[0180] determining that the first pair of consecutive symbols is associated with a zero-crossing condition;

[0181] Based on the determination, modifying the second symbol to generate a modified symbol that avoids the zero-crossing condition; and

[0182] A correction list is generated indicating that the second symbol has been modified to avoid the zero-crossing condition.

[0183] Unless the context dictates otherwise, use of the word "or" herein may be considered an "inclusive or," or use permitting inclusion or application of a term that includes one or more items linked by the word "or" (e.g., the phrase "A or B" may be interpreted as permitting only "A," only "B," or both "A" and "B"). As used herein, a phrase referring to "at least one of" a list of items refers to any combination of those items (including single members). As an example, "at least one of a, b, or c" is intended to encompass: a, b, c, ab, ac, bc, and abc, as well as any combination with multiples of the same element (e.g., aa, aaa, aab, aac, abb, acc, bb, bbb, bbc, cc, and ccc, or any other ordering of a, b, and c). Additionally, items shown in the drawings and terms discussed herein may refer to one or more items or terms, and thus, in this written description, reference may be made interchangeably to the singular or plural forms of these items and terms. Finally, although the subject matter has been described in language specific to structural features or methodological operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or operations described above, including being not necessarily limited to the organization in which the features are arranged or the order in which the operations are performed.

Claims

1. A device, comprising: A polar transceiver configured to: coupled to an antenna; as well as Data including a plurality of symbols associated with quadrature amplitude modulation is transmitted via the antenna, the plurality of symbols including a plurality of sets of two consecutive symbols, an absolute value of a phase difference between the two consecutive symbols within each of the plurality of sets being substantially different from 180 degrees.

2. The device according to claim 1, wherein: The plurality of symbols includes a first symbol, a second symbol, and a third symbol; The first symbol, the second symbol and the third symbol represent consecutive symbols; The first symbol precedes the second symbol; The second symbol precedes the third symbol; A first set of the plurality of sets includes the first symbol and the second symbol; and A second set of the plurality of sets includes the second symbol and the third symbol. 3 . The apparatus of claim 1 , wherein the absolute value of the phase difference differs from 180 degrees by at least ±0.5 degrees. The apparatus of claim 3 , wherein the absolute value of the phase difference differs from 180 degrees by at least ±1 degree. 5 . The apparatus of claim 1 , wherein the polar transceiver is configured to transmit a correction list identifying symbols within the plurality of symbols that have been encoded to avoid a zero-crossing condition.

6. The device according to claim 5, wherein: The two consecutive symbols include a first symbol and a second symbol; The first symbol precedes the second symbol; and Each of the symbols that has been encoded to avoid the zero-crossing condition represents the second symbol within one of the multiple sets and has a symbol state in the same quadrant of the constellation diagram as the first symbol within the one of the multiple sets.

7. The apparatus of claim 6, wherein the first symbol and the second symbol within the one of the plurality of sets are approximately equal in phase.

8. The apparatus of claim 6, wherein the first symbols and the second symbols within the one of the plurality of sets are approximately equal in magnitude.

9. The apparatus according to claim 5, wherein: The correction list comprises a plurality of bits; and The number of the plurality of bits is equal to the number of the plurality of symbols.

10. The apparatus according to claim 5, wherein: The correction list includes other symbols associated with the quadrature amplitude modulation; and The number of the further symbols is equal to the number of the symbols that have been encoded plus one.

11. The apparatus of claim 5, wherein the zero-crossing condition represents a signal transition through an origin of a constellation diagram between symbol states associated with two symbols.

12. The apparatus according to claim 1, wherein: The device includes wireless earbuds; and The wireless earbud includes the polarity transceiver.

13. The apparatus according to claim 12, wherein: The wireless earbuds are configured to transmit with Bluetooth ® associated radio frequency signals; and The radio frequency signal includes the data.

14. A device comprising: A wireless transceiver configured to: coupled to an antenna; communicating, via the antenna, data comprising a plurality of symbols associated with quadrature amplitude modulation and encoded using zero-crossing avoidance coding; as well as A correction list is communicated via the antenna, the correction list identifying symbols of the plurality of symbols that have been encoded using the zero-crossing avoidance coding.

15. The apparatus according to claim 14, wherein: The plurality of symbols comprises a plurality of sets of two consecutive symbols; and The two consecutive symbols within each set of the plurality of sets do not have opposite phases.

16. The apparatus of claim 15, wherein an absolute value of a phase difference between the two consecutive symbols within each of the plurality of sets is substantially different from 180 degrees.

17. The apparatus of claim 14, wherein each of the symbols that has been encoded using the zero-crossing avoidance coding has approximately the same phase as another symbol preceding the symbol within the plurality of symbols.

18. The apparatus of claim 17, wherein each of the symbols that has been encoded using the zero-crossing avoidance encoding has approximately the same amplitude as the another symbol preceding the symbol within the plurality of symbols.

19. The apparatus of claim 14, wherein: The correction list includes a plurality of bits; The number of the plurality of bits is equal to the number of the plurality of symbols; At least one bit of the plurality of bits has a first value indicating that a corresponding symbol of the plurality of symbols has been encoded using the zero-crossing avoidance encoding; and At least one other bit of the plurality of bits has a second value indicating that a corresponding symbol of the plurality of symbols has not been encoded using the zero-crossing avoidance encoding.

20. The apparatus of claim 14, wherein: The correction list includes other symbols associated with the quadrature amplitude modulation; and The number of the further symbols is equal to the number of the symbols that have been encoded using the zero-crossing avoidance encoding plus one.

21. The apparatus of claim 14, wherein the wireless transceiver is configured to communicate, via the antenna, a protocol data unit comprising the data and the correction list.

22. The apparatus of claim 14, wherein the wireless transceiver comprises: a transmitter configured to transmit the data and the correction list; or A receiver is configured to receive the data and the correction list.

23. The apparatus of claim 14, wherein the wireless transceiver comprises: a polar transceiver configured to perform the quadrature amplitude modulation based on amplitude and phase associated with the plurality of symbols; or A Cartesian transceiver is configured to perform the quadrature amplitude modulation based on in-phase values ​​and quadrature values ​​associated with the plurality of symbols.

24. The apparatus according to claim 14, further comprising: A modem, the modem being configured to: encoding the data using zero-crossing avoidance coding; as well as generating a modulated signal based on the encoded data; and The wireless transceiver is configured to transmit a radio frequency signal including the data, the radio frequency signal being modulated according to quadrature amplitude modulation based on the modulation signal.

25. A method of performing zero-crossing avoidance coding, the method comprising: accepting a first pair of consecutive symbols associated with quadrature amplitude modulation, the first pair of consecutive symbols comprising a first symbol and a second symbol; outputting the first symbol as part of an encoded data sequence; determining that the first pair of consecutive symbols is associated with a zero-crossing condition; as well as Based on the determination, the second symbol is modified to generate a modified symbol that avoids the zero-crossing condition.

26. The method of claim 25, wherein the modification of the second symbol comprises: The second symbol is modified such that an absolute value of a phase difference between the first symbol and the second symbol is substantially different from 180 degrees.

27. The method of claim 26, wherein the modification of the second symbol comprises: The second symbol is modified to have the same phase as the first symbol.

28. The method according to claim 25, further comprising: A correction list is generated indicating that the second symbol has been modified to avoid the zero-crossing condition.

29. The method according to claim 25, further comprising: accepting a second pair of consecutive symbols associated with the quadrature amplitude modulation, the second pair of consecutive symbols comprising the modified symbol and a third symbol; outputting the modified symbol as part of the encoded data sequence; as well as It is determined that the second pair of consecutive symbols is not associated with the zero-crossing condition.

30. A computer-readable storage medium comprising instructions that, in response to execution by a processor, cause the processor to: accepting a first pair of consecutive symbols associated with quadrature amplitude modulation, the first pair of consecutive symbols comprising a first symbol and a second symbol; outputting the first symbol as part of an encoded data sequence; determining that the first pair of consecutive symbols is associated with a zero-crossing condition; based on the determination, modifying the second symbol to generate a modified symbol that avoids the zero-crossing condition; as well as A correction list is generated indicating that the second symbol has been modified to avoid the zero-crossing condition.

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