Transmitting antenna diversity wireless audio system

Abstract

A wireless audio system is provided that includes a transmitter using multiple antenna diversity techniques for different signal types, thereby optimizing multipath performance and improving the spectral efficiency of the system.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 882,980, filed on August 5, 2019, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates generally to wireless audio systems that utilize transmit antenna diversity. Specifically, the present application relates to a wireless audio system having a transmitter that applies multiple antenna diversity techniques for different signal types. Background Art

[0004] Audio production can relate to and use many components, comprise microphone, wireless audio transmitter, wireless audio receiver, recorder and / or mixer, be used to catch, record and present the sound of production, described production is television program, news, movie, real-time event and other type of production for example.Microphone catches the sound of production usually, and described sound is wirelessly transmitted to wireless audio receiver from microphone and / or wireless audio transmitter.Wireless audio receiver can be connected to recorder and / or mixer, be used for recording and / or mixing sound by the musician component (crew member) of for example making sound mixer.For example the electronic device of computer and smart phone can be connected to recorder and / or mixer, to allow musician component to monitor audio level and time code.

[0005] Wireless audio transmitters, wireless audio receivers, wireless microphones, and other portable wireless communication devices include antennas for transmitting and receiving radio frequency (RF) signals, which may include digital or analog signals, such as modulated audio signals, data signals, and / or control signals. Users of portable wireless communication devices include stage performers, singers, actors, journalists, and the like.

[0006] A wireless audio transmitter can transmit an RF signal containing an audio signal to a wireless audio receiver. The wireless audio transmitter can be contained, for example, in a wireless handheld microphone or shoulder bag that is held or worn by a user and includes an integrated transmitter and antenna. As another example, the wireless audio transmitter can be contained in an access point or other centralized unit. The wireless audio receiver can be portable, such as a wireless headset, a wireless conferencing unit, or a shoulder bag. When the RF signal is received at the wireless audio receiver, it may be attenuated due to multipath fading caused by constructive interference and / or other types of interference. This attenuation can cause the RF signal to have a poor signal-to-noise ratio (SNR), which can lead to bit errors that can cause audio artifacts and noise suppression on the resulting output audio. However, in many scenarios and environments, such as during professional stage productions and concerts, noise suppression on the output audio is undesirable. The effects of such multipath fading and interference are most prevalent in harsh RF environments, where physical and electrical factors, such as the movement of the microphone within the environment, other RF signals, and operation in large venues, can affect the transmission and reception of RF signals.

[0007] To mitigate issues with multipath fading associated with RF signals, wireless audio components can utilize frequency diversity and / or antenna diversity techniques. For example, a wireless audio transmitter can utilize frequency diversity to simultaneously transmit two RF signals at two separate frequencies within a combined RF signal over a single antenna, where the two RF signals contain the same audio signal. A wireless audio receiver can then use one or both of the underlying RF signals. As another example, a wireless audio receiver can utilize antenna diversity to simultaneously receive RF signals from a wireless audio transmitter over multiple antennas. The received RF signals can be combined to produce a single audio output.

[0008] However, utilizing diversity on portable wireless audio receivers can be difficult and challenging due to size and power constraints. For example, portable wireless audio receivers are typically small and battery-powered, so utilizing diversity techniques on such receivers can result in suboptimal antenna placement and / or unacceptable power consumption. Furthermore, utilizing diversity techniques on multiple portable wireless audio receivers can involve considerable cost and complexity.

[0009] Other techniques for alleviating the problem of multipath fading of RF signals may have undesirable side effects. For example, the transmit power of a wireless audio transmitter can be increased to allow for a larger fading margin. However, when the transmit power is increased, the overall spectral efficiency may be negatively affected due to intermodulation products. In addition, the physical design of the transmitter and / or government regulations may limit the amount of increase in transmit power that can be achieved. In addition, increased transmit power cannot address the error floor caused by frequency selective fading. As another example, an antenna can be designed to focus the signal energy transmitted from the wireless audio transmitter to the wireless audio receiver. However, the directionality of such an antenna may be too strong, which may affect the coverage range of the wireless audio transmitter. As another example, in certain applications (e.g., wireless in-ear personal monitors), special signal decomposition techniques can be used to attempt to improve diversity performance. However, such techniques may cause phase cancellation issues, which may lead to reduced performance and become unreliable.

[0010] Therefore, there is an opportunity to develop wireless audio systems that utilize transmit antenna diversity that addresses these concerns. More specifically, there is an opportunity to develop wireless audio systems that have transmitters that use multiple antenna diversity techniques for different signal types to optimize multipath performance and improve spectral efficiency. Summary of the Invention

[0011] The present invention aims to solve the above problems by providing a wireless audio system that utilizes transmit antenna diversity, which is designed to include, among other aspects: (1) simultaneously apply different transmit diversity techniques depending on the type of signal transmitted, such as data / control symbols, pilot symbols and synchronization signals; (2) utilize embedded orthogonal pilot symbols to perform independent channel estimation and coherent demodulation while maintaining the desired data rate; and (3) flexibly perform coding and / or routing to multiple antennas to increase coverage and / or capacity.

[0012] In an embodiment, a wireless audio transmitter includes: a mode selection interface for enabling a user to select one of a plurality of modes of the wireless audio transmitter; a plurality of antennas each configured to transmit an audio signal; an encoder in communication with the mode selection interface, wherein the encoder is configured to receive (i) data symbols comprising an audio data signal and a control signal and (ii) pilot symbols; a synchronous converter; and the plurality of converters each in communication with the encoder, the synchronous converter, and one of the plurality of antennas. The encoder may be further configured to: when in a first mode, receive and route the data symbols and the pilot symbols to each of a plurality of converters; and when in a second mode, receive and encode the data symbols and the pilot symbols based on a first diversity technique, and route the encoded data symbols and the encoded pilot symbols to one or more subsets of the plurality of converters.

[0013] The synchronous converter may be configured to receive and convert a synchronization signal based on a second diversity technique. Each of the converters may be configured to: when in the first mode, combine the data symbols, the pilot symbols, and the converted synchronization signal into the audio signal to be transmitted on one of the plurality of antennas; and when in the second mode, combine the coded data symbols, the coded pilot symbols, and the converted synchronization signal into the audio signal to be transmitted on one of the plurality of antennas.

[0014] In another embodiment, a method for wirelessly transmitting an audio signal using a wireless audio transmitter may include: receiving a selection of one of a plurality of modes of the wireless audio transmitter from a mode selection interface; receiving, at an encoder, (i) data symbols comprising an audio data signal and a control signal and (ii) pilot symbols; when the selection is a first mode, routing, using the encoder, the data symbols and the pilot symbols to each of a plurality of converters; and when the selection is a second mode: encoding, using the encoder, the data symbols and the pilot symbols based on a first diversity technique, and routing, using the encoder, the encoded data symbols and the encoded pilot symbols to one or more subsets of the plurality of converters. The method may further include: receiving a synchronization signal at a synchronous converter; transforming the synchronization signal based on a second diversity technique using the synchronous converter; when the selection is the first mode, using each of the plurality of converters to combine the data symbols, the pilot symbols, and the transformed synchronization signal into the audio signal to be transmitted on one of the plurality of antennas; and when the selection is the second mode, using the one or more subsets of the plurality of converters to combine the encoded data symbols, the encoded pilot symbols, and the transformed synchronization signal into the audio signal to be transmitted on one of the plurality of antennas.

[0015] In another embodiment, a wireless audio system may include: an audio source; a wireless audio transmitter in communication with the audio source; and a wireless audio receiver in wireless communication with the wireless audio transmitter. The audio source may be configured to generate one or more audio source signals, each including data symbols, the data symbols including an audio data signal and a control signal. The wireless audio transmitter may include: a plurality of antennas, each configured to transmit an audio signal; an encoder in communication with the audio source and configured to receive and encode the data symbols and pilot symbols based on a first diversity technique; a synchronous converter in communication with the audio source and configured to receive and convert a synchronization signal based on a second diversity technique; and a plurality of converters, each in communication with the encoder, the synchronous converter, and one of the plurality of antennas, wherein each of the plurality of converters is configured to combine the encoded data symbols, the encoded pilot symbols, and the converted synchronization signal into the audio signal to be transmitted on one of the plurality of antennas. The wireless audio receiver may be configured to receive the audio signal on at least one receive antenna.

[0016] These and other embodiments and various combinations and aspects will become apparent and will be more fully understood from the following detailed description and accompanying drawings, which set forth illustrative embodiments indicative of the various ways in which the principles of the invention may be applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of a wireless audio system utilizing transmit antenna diversity according to some embodiments.

[0018] Figure 2 is a schematic diagram of a portion of a wireless audio transmitter utilizing two antennas for transmit diversity according to some embodiments.

[0019] Figure 3 is a schematic diagram of a portion of a wireless audio transmitter utilizing four antennas for transmit diversity according to some embodiments.

[0020] Figure 4 Flowchart illustrating operations for wirelessly transmitting audio signals using a wireless audio transmitter that utilizes transmit antenna diversity in accordance with some embodiments.

[0021] Figure 5 is a table illustrating encoding of data and pilot symbols using space-time block coding for a wireless audio transmitter utilizing two antennas for transmit diversity, according to some embodiments.

[0022] Figure 6 is an exemplary graph illustrating the performance of a wireless audio system utilizing two antennas for transmit diversity, according to some embodiments.

[0023] Figure 7A 、 7B , 8A, 8B, and 9 are exemplary depictions of encoding and / or routing audio channels to transducers and antennas in different modes of a wireless audio transmitter according to some embodiments. DETAILED DESCRIPTION

[0024] The following description describes, illustrates, and exemplifies one or more specific embodiments of the present invention according to its principles. This description is not intended to limit the invention to the embodiments described herein, but rather to explain and teach the principles of the invention so that a person skilled in the art can understand these principles and, through this understanding, be able to apply the principles to practice not only the embodiments described herein, but also other embodiments that can be conceived according to these principles. The scope of the present invention is intended to encompass all such embodiments that may come within the scope of the appended claims, either literally or under the doctrine of equivalents.

[0025] It should be noted that in the description and drawings, similar or substantially similar elements may be marked with the same reference numbers. However, sometimes, these elements may be marked with different numbers, for example, when such markings help to clarify the description. In addition, the drawings set forth herein are not necessarily drawn to scale, and in some cases, the proportions may have been exaggerated to more clearly depict certain features. Such markings and diagrammatic practices do not necessarily imply underlying substantive purposes. As stated above, this specification is intended to be considered as a whole and to be interpreted in accordance with the principles of the invention as taught herein and as understood by those of ordinary skill in the art.

[0026] The wireless audio system described herein can utilize transmit antenna diversity by including a transmitter using multiple antenna diversity techniques for different signal types to achieve ideal multipath performance and improved spectral efficiency. Different signal types may include, for example, data symbols containing audio data signals and control signals, pilot symbols, and synchronization signals. The wireless audio transmitter can use orthogonal pilot symbols for independent channel estimation and coherent demodulation. Compared to a system with a non-diversity wireless audio transmitter, the data rate of a wireless audio system with transmit antenna diversity can be consistent and unchanged. The number of antennas utilized by the wireless audio transmitter can be optional, expandable, and scalable to achieve greater coverage and / or capacity. In addition, even if a specific transmission path fails, the wireless audio system can still operate with reduced range and / or performance. The performance of the wireless audio system may be more stable in both a single zone (e.g., stage) and multiple zones (e.g., stage and backstage).

[0027] Figure 1 FIG. 1 is a schematic diagram of an exemplary wireless audio system 100 utilizing transmit antenna diversity. System 100 may include a wireless audio transmitter 110 having antennas 112a, 112b for transmitting radio frequency (RF) signals and wireless audio receivers 150a, 150b, 150c having corresponding antennas 152a, 152b, 152c for receiving RF signals. Transmitter 110 may utilize antenna diversity due to the multiple antennas 112a, 112b, as described in more detail below. Antenna diversity may include, for example, the use of physically separated antennas (i.e., antennas positioned spatially apart). It is contemplated and possible that transmitter 110 has more than two antennas and that there are any number of receivers 150. In some embodiments, transmitter 110 may be an access point or other centralized unit. In some embodiments, receivers 150a, 150b, 150c may be portable wireless audio receivers, such as wireless headphones, wireless conferencing units, or shoulder bags.

[0028] In an embodiment, system 100 may be an orthogonal frequency division multiplexing (OFDM) wideband audio system, which allows various types of traffic to be carried on separate subcarriers and multiplexed together into a single wideband carrier. In other embodiments, system 100 may be a narrowband audio system, such as a personal monitoring system. The RF signal transmitted by transmitter 110 and received by receiver 150 may include, for example, data symbols having audio data signals and control signals, pilot symbols, and / or synchronization signals. In some embodiments, the data symbols may be QPSK / QAM modulated subcarriers that may carry audio data signals and / or control signals. The pilot symbols may be known symbols that may enable channel estimation and coherent demodulation of the signal at receiver 150.

[0029] As described in more detail below, in some embodiments, data symbols and pilot symbols may be mapped to multiple antennas using space-time block coding (STBC). Encoding data symbols and pilot symbols using STBC involves processing grouping of symbols and transmitting the symbols multiple times across multiple antennas. In other embodiments, other suitable techniques may be used to transform data symbols and pilot symbols.

[0030] A synchronization signal may be transmitted from transmitter 110 so that receiver 150 can acquire a frequency and / or timing reference for system 100. Transmitter 110 and receiver 150 generally need to be synchronized with each other so that data symbols and pilot symbols can be properly transmitted and received. For example, the frequency and phase of the local oscillator of receiver 150 may need to be synchronized with the frequency and phase of transmitter 110. As described in more detail below, round-robin diversity or cyclic delay diversity (CDD) techniques may be applied to the synchronization signal. Thus, data symbols, pilot symbols, and synchronization signals may utilize different antenna diversity techniques.

[0031] System 100 may also include an audio source 120 in communication with transmitter 110. Audio source 120 may generate one or more audio source signals including data symbols having an audio data signal and a control signal. Transmitter 110 may modulate the data symbols from audio source 120 and insert pilot symbols and synchronization symbols before transmitting the RF signal on antennas 112a, 112b.

[0032] Figure 2 FIG2 is a schematic diagram of a portion of a wireless audio transmitter 210 utilizing two antennas 212a and 212b for transmit diversity. Figure 2 Other components of the transmitter 210, such as a modulator, an analog-to-digital converter, a digital-to-analog converter, a codec, etc., are not shown. The transmitter 210 may transmit an RF signal including data symbols, pilot symbols, and / or synchronization signals for one or more receivers (e.g., Figure 1The various components included in the wireless audio transmitter 210 may be implemented using software that may be executed by one or more servers or computers (e.g., computing devices having processors and memories), and / or may be implemented by hardware (e.g., discrete logic circuits, application specific integrated circuits (ASICs), programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.).

[0033] Figure 4 An embodiment of a process 400 for wirelessly transmitting an audio signal using a wireless audio transmitter that utilizes transmit antenna diversity is shown in FIG. The process 400 may be performed by the transmitter 210. One or more processors and / or other processing components (e.g., analog-to-digital converters, encryption chips, etc.) within or external to the transmitter 210 may perform any, some, or all of the steps of the process 400. One or more other types of components (e.g., memory, input and / or output devices, transmitters, receivers, buffers, drivers, discrete components, etc.) may also be used in conjunction with the processors and / or other processing components to perform any, some, or all of the steps of the process 400.

[0034] Transmitter 210 may generate a signal comprising data symbols, pilot symbols, and synchronization signals for transmission over antennas 212a, 212b. The data symbols may comprise audio data signals and / or control signals. The control signals may comprise system messages and other information. Encoder 214 may have multiple operating modes that allow encoding and / or routing of data symbols and pilot symbols for ultimate transmission over antennas 212a, 212b. At step 402, a selection of a mode for encoder 214 and transmitter 210 may be received, for example, from a user interface. At step 404, data symbols and pilot symbols may be received by encoder 214.

[0035] The synchronization signal may be in the frequency domain or the time domain and may be transformed using cyclic delay diversity (CDD) techniques for transmission on antennas 212a, 212b. At step 406, the synchronization signal may be received by synchronous converter 218. CDD may be applied to the synchronization signal so that no nulls appear in the radiation patterns of antennas 212a, 212b. Specifically, at step 408, a phase ramp may be applied by synchronous converter 218. To transform the synchronization signal in the frequency domain, or the synchronization signal can be transformed by the synchronization transformer 218 using a cyclic delay in the time domain. Thus, the first antenna 212a can transmit the original copy of the synchronization signal, while the second antenna 212b can transmit a cyclically shifted version of the synchronization signal. It should be understood that Figure 2 The two antennas 212a, 212b shown are for exemplary purposes only. In some embodiments, the synchronization signal may be transformed by the synchronization transformer 218 in a round-robin switching diversity scheme.

[0036] At step 410, depending on the selected mode, the data symbols and pilot symbols (whether encoded or unencoded) and the synchronization signal may be combined by the converters 216a, 216b. For example, in a first mode of the transmitter 210, the data symbols and pilot symbols may not be encoded by the encoder 214 and routed to the converters 216a, 216b at step 412. At step 414, the converters 216a, 216b may then combine the data symbols, pilot symbols, and the transformed synchronization signal into an audio signal that is transmitted as an RF signal on the antennas 212a, 212b. In another example, in a second mode of the transmitter 210, the data symbols and pilot symbols may be encoded by the encoder 214 at step 416 and routed to the converters 216a, 216b at step 418. At step 420, converters 216a, 216b may combine the encoded data symbols, the encoded pilot symbols, and the transformed synchronization signal into an audio signal that is transmitted on antennas 212a, 212b.

[0037] In an embodiment, the transmitter 210 may be an OFDM wideband transmitter, and the data symbols and pilot symbols may be mapped in the frequency domain by space-time block coding (STBC) in the encoder 214. The data symbols may be QPSK / QAM modulated subcarriers. Figure 5 As shown in the table, the encoder 214 can process a pair of symbols for transmission on two antennas 212a, 212b. For example, when the input symbol pair of the data subcarrier is s n,0 、s n,1 When the first antenna 212a can transmit the same symbol pair s n,0 、s n,1 , and the second antenna 212b can transmit the symbol pair s * n,0 、-s * n,1 (i.e., the complex conjugate of the input symbol pair). Specifically, as is known in the art, encoder 214 may receive the input symbol pair and encode it using STBC to generate symbols for transmission on antennas 212a, 212b. In an embodiment, the code may be rate-1 STBC (known from Alamouti) or another suitable code.

[0038] The pilot symbols may be known symbols used for channel estimation and coherent demodulation of the signal at the receiver. In an embodiment, the pilot symbols may be orthogonal sequences. Figure 5As shown in the table, STBC encoder 214 can process a pair of values ​​+1 for the pilot symbol and generate an orthogonal pilot pattern on antennas 212a and 212b. For example, when the input symbol pair of the pilot symbol is +1, +1, the first antenna 212a can transmit the same symbol pair +1, +1, while the second antenna 212b can transmit the symbol pair +1, -1. In an embodiment, the pilot symbols can be orthogonal in code rather than in the time or frequency domain. This ensures that capacity is not reduced due to the presence of unique pilots on multiple antennas. In addition, in an embodiment, the pilot symbols can use the same STBC mapping as the data symbols, which can help reduce the complexity of the implementation.

[0039] One or more receivers, such as receivers 150a, 150b, and 150c, may receive RF signals including audio signals transmitted from transmitter 210 on their respective antennas, such as antennas 152a, 152b, and 152c. The receivers may demodulate, convert, and / or process the received RF signals to generate analog or digital output audio signals, as is known in the art. Specifically, the receivers may decode data symbols and pilot symbols based on the symbol encoding scheme (e.g., Alamoti Rate-1 STBC). In an embodiment, the receivers may each have multiple antennas that simultaneously receive the transmitted RF signals from transmitter 210 in a spatial diversity scheme. When both the transmitter and receiver have spatial diversity, multiple-input multiple-output (MIMO) technology may be utilized. For example, because bit error rates are lower in fading environments, the use of MIMO can increase diversity gain for fading mitigation. As another example, the use of MIMO can produce higher throughput, i.e., more bits per frequency, due to spatial multiplexing.

[0040] exist Figure 6 As can be seen in the exemplary graph, the performance of the wireless audio system 100 with two antenna diversity is improved compared to the performance of a single antenna wireless audio system. Specifically, Figure 6 The data bit error rate (BER) performance of the wireless audio system 100 with two antenna diversity (dashed line) is compared with the performance of a single antenna wireless audio system (solid line). -5 ), the performance of the wireless audio system 100 with two antenna diversity is about 5dB better. It should be noted that Figure 6 The graph of φ reflects that the combined transmit power of the wireless audio system 100 with two antenna diversity is equal to the transmit power of the single antenna wireless audio system.

[0041] Figure 3 FIG is a schematic diagram of a portion of an OFDM broadband wireless audio transmitter 310 that utilizes four antennas 312a, 312b, 312c, and 312d for transmit diversity. Figure 3Other components of the transmitter 310, such as a modulator, an analog-to-digital converter, a digital-to-analog converter, a codec, etc., are not shown. The transmitter 310 may transmit an RF signal including data symbols, pilot symbols, and / or synchronization signals for one or more receivers (e.g., Figure 1 The various components included in the wireless audio transmitter 310 may be implemented using software that may be executed by one or more servers or computers (e.g., computing devices having processors and memories), and / or may be implemented by hardware (e.g., discrete logic circuits, application specific integrated circuits (ASICs), programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.).

[0042] Similar to Figure 2 2. The transmitter 210 in FIG. 2 may generate a signal comprising data symbols, pilot symbols, and synchronization signals for transmission on antennas 312a, 312b, 312c, and 312d. The data symbols may include audio data signals and / or control signals. The control signals may include system messages and other information. The data symbols and pilot symbols in transmitter 310 may be in the frequency domain and may be mapped by a space-time block coding (STBC) encoder 314. In an embodiment, the STBC encoder 314 may utilize Alamoti Rate-1 STBC, Quasi-Orthogonal Rate-1 STBC (known from Jafarkhani), Orthogonal Rate-3 / 4 STBC (known from Ganesan), or other suitable codes. The synchronization signal may be in the frequency domain or the time domain and may be transformed using cyclic delay diversity (CDD) techniques for transmission on antennas 312a, 312b, 312c, and 312d. Alternatively, the synchronization signal may be transmitted on antennas 312a, 312b, 312c, 312d in a round-robin switching diversity scheme. Figure 2 The functionality of the synchronous converter 218 is the same or similar Figure 3 functionality of the synchronous converter 318.

[0043] Figure 4 The illustrated embodiment of process 400 may also be performed by transmitter 310. One or more processors and / or other processing components (e.g., analog-to-digital converters, encryption chips, etc.) within or external to transmitter 310 may perform any, some, or all of the steps of process 400. One or more other types of components (e.g., memory, input and / or output devices, transmitters, receivers, buffers, drivers, discrete components, etc.) may also be utilized in conjunction with the processors and / or other processing components to perform any, some, or all of the steps of process 400.

[0044] The STBC encoder 314 can have a variety of operating modes, which allows data symbols and pilot symbols to be encoded and / or routed to ultimately transmit on antennas 312a, 312b, 312c, 312d. At step 402, the selection of the pattern of the STBC encoder 314 and transmitter 310 can be received, for example, from a user interface. The selected pattern can determine the type (if any) and the routing of the mapping performed by the STBC encoder 314. In an embodiment, transmitter 310 can have three patterns, and in other embodiments, transmitter 310 can have the pattern of another number. The number of the pattern of transmitter 310 can depend on the number of antennas, the number of coverage areas and / or the number of audio channels.

[0045] The first mode of the transmitter 310 can cause the STBC encoder 314 to receive (step 404) data symbols and pilot symbols and route them (step 412) to the converters 316a, 316b, 316c, 316d that communicate with the antennas 312a, 312b, 312c, 312d accordingly without utilizing any STBC mapping. This mode can route up to N audio channels to N coverage areas, where N is equal to the number of antennas. Thus, for the transmitter 310, up to four audio channels can be routed to four coverage areas. For example, in this mode, the STBC encoder 314 can route one audio channel (i.e., one data symbol and pilot symbol stream) to four single-antenna coverage areas, such as Figure 7A This mode can achieve coverage of multiple areas along a parade route, for example. As another example, in this mode, the STBC encoder 314 can route four unique audio channels (i.e., four separate data symbol and pilot symbol streams) to four corresponding single antenna coverage areas, such as Figure 7B Depicted.

[0046] A second mode of the transmitter 310 may cause the STBC encoder 314 to receive (step 404) and encode (step 416) data symbols and pilot symbols using a 2-branch STBC mapping. The encoded data symbols and pilot symbols may be routed (step 418) to converters 316a, 316b, 316c, 316d that communicate with the antennas 312a, 312b, 312c, 312d, respectively. This mode may encode up to N / 2 audio channels and route them to N / 2 coverage areas, e.g., for the transmitter 310, up to two audio channels may be encoded and routed to two coverage areas. For example, in this mode, the STBC encoder 314 may encode one audio channel (i.e., one data symbol and pilot symbol stream) and route it to two coverage areas, each having two antennas, e.g., Figure 8ASpecifically, one coverage area may be covered by antennas 312a, 312b, and another coverage area may be covered by antennas 312c, 312d. As another example, in this mode, the STBC encoder 314 may encode two unique audio channels (i.e., two separate streams of data symbols and pilot symbols) and route them to two corresponding coverage areas, each with two antennas, such as Figure 8B Depicted.

[0047] The third mode of the transmitter 310 causes the STBC encoder 314 to receive (step 404) and encode (step 416) data symbols and pilot symbols using a 4-branch STBC mapping. The encoded data symbols and pilot symbols can be routed (step 418) to the converters 316a, 316b, 316c, 316d that communicate with the antennas 312a, 312b, 312c, 312d accordingly. This mode can encode up to N / 4 audio channels and route them to N / 4 coverage areas, for example, for the transmitter 310, up to one audio channel can be encoded and routed to one coverage area. For example, in this mode, the STBC encoder 314 can encode one audio channel (i.e., one data symbol and pilot symbol stream) and route it to one coverage area with four antennas, such as Figure 9 Depicted.

[0048] Converters 316a, 316b, 316c, 316d may combine data symbols, pilot symbols, and synchronization signals, such as in the first mode described above where no encoding is present (step 414), or may combine coded data symbols, coded pilot symbols, and synchronization signals, such as in the second and third modes described above (step 420). Converters 316a, 316b, 316c, 316d may generate audio signals that are transmitted on antennas 312a, 312b, 312c, 312d, respectively.

[0049] Each of the converters 316a, 316b, 316c, 316d may include an inverse fast Fourier transform (IFFT) 320a, 320b, 320c, 320d to convert the data symbols and pilot symbols into the time domain. The output of the synchronization converter 318 (i.e., the converted synchronization signal) may also be passed to the IFFT 320a, 320b, 320c, 320d. The output of the respective IFFT 320a, 320b, 320c, 320d may be converted by a parallel-to-serial converter 322a, 322b, 322c, 322d. To transmit the audio signals on the antennas 312a, 312b, 312c, 312d, a cyclic delay 324a, 324b, 324c, 324d may be applied to the output of the parallel-to-serial converter 322a, 322b, 322c, 322d. Each cyclic delay may result in a unique time shift on each antenna. Specifically, the outputs of the parallel-to-serial converters 322a, 322b, 322c, 322d may include data symbols, pilot symbols, and synchronization signals in the time domain, i.e., after conversion by the IFFTs 320a, 320b, 320c, 320d. As previously discussed, the data and pilot symbols may be encoded in some modes and may not be encoded in other modes.

[0050] One or more receivers, such as receivers 150a, 150b, and 150c, can receive RF signals including audio signals transmitted from transmitter 310 on their respective antennas, such as antennas 152a, 152b, and 152c. The receivers can demodulate, convert, and / or process the received RF signals to generate analog or digital output audio signals, as is known in the art. Specifically, the receivers can decode data symbols and pilot symbols based on a symbol encoding scheme, such as Alamoti Rate-1 STBC, Quasi-Orthogonal Jafarhani Rate-1 STBC, or Orthogonal Ganeson Rate-3 / 4 STBC. In an embodiment, the receivers can each have multiple antennas in a spatial diversity scheme that simultaneously receive the transmitted RF signals from transmitter 310.

[0051] As will be understood by those skilled in the art, any process descriptions or blocks in the drawings should be understood to represent modules, segments, or portions of code, which contain one or more executable instructions for implementing specific logical functions or steps in the process, and that alternative implementations are included within the scope of embodiments of the present invention, in which functions may not be performed in the order shown or discussed, including performing functions substantially simultaneously or in the reverse order, depending on the functionality involved.

[0052] This disclosure is intended to explain how to design and use various embodiments of the technology according to the present invention, not to limit the true, intended and fair scope and spirit of the technology according to the present invention. The foregoing description is not intended to be exhaustive or limited to the exact form disclosed. In view of the above teachings, modifications and variations are possible. The embodiments are selected and described in order to provide the best illustration of the principles of the technology according to the present invention as described and the practical application of the technology according to the present invention, and to enable one of ordinary skill in the art to utilize the technology according to the present invention in various embodiments and with various modifications suitable for the specific use intended. When interpreted according to the breadth of the rights clearly, legally and fairly granted, all such modifications and variations and all equivalents thereof are within the scope of the embodiments as defined by the appended claims and may be amended during the pendency of this patent application.

Claims

1. A wireless audio transmitter, comprising: (A) a mode selection interface for enabling a user to select one of a plurality of modes of the wireless audio transmitter; (B) a plurality of antennas configured to each transmit an audio signal; (C) an encoder in communication with the mode selection interface, the encoder configured to receive (i) data symbols including an audio data signal and a control signal and (ii) pilot symbols, the encoder further configured to: (1) when in a first mode, receiving the data symbols and the pilot symbols and routing them to each of a plurality of converters; and (2) When in the second mode: receiving and encoding the data symbols and the pilot symbols based on a first diversity technique; and routing coded data symbols and coded pilot symbols to one or more subsets of the plurality of switches; (D) a synchronous converter configured to receive and convert a synchronization signal based on a second diversity technique; and (E) the plurality of converters each in communication with the encoder, the synchronous converter, and one of the plurality of antennas, wherein each of the plurality of converters is configured to: (1) when in the first mode, combining the data symbols, the pilot symbols, and the transformed synchronization signal into the audio signal to be transmitted on one of the plurality of antennas; and (2) When in the second mode, combining the encoded data symbols, the encoded pilot symbols, and the transformed synchronization signal into the audio signal to be transmitted on one of the multiple antennas. 2 . The wireless audio transmitter of claim 1 , wherein the first diversity technique comprises space-time block coding in the frequency domain.

3. The wireless audio transmitter of claim 2, wherein the space-time block code comprises an Alamoti rate-1 code.

4. The wireless audio transmitter of claim 1 , wherein the synchronization converter comprises a phase shifter, and the second diversity technique comprises converting the synchronization signal by applying a phase ramp to the synchronization signal using the phase shifter. The wireless audio transmitter of claim 1 , wherein the second diversity technique comprises a round-robin diversity scheme. The wireless audio transmitter of claim 1 , wherein the pilot symbols are orthogonal. 7 . The wireless audio transmitter of claim 1 , wherein each of the plurality of converters comprises an inverse fast Fourier transform and a parallel-to-serial converter.

8. The wireless audio transmitter of claim 1, wherein each of the plurality of converters comprises a cyclic delay module, wherein an amount of delay of the cyclic delay module depends on a selected mode of the plurality of modes.

9. The wireless audio transmitter according to claim 1, wherein: The audio signal is transmitted on a first subset of the plurality of antennas configured to cover a first region; and The audio signal is transmitted on a second subset of the plurality of antennas configured to cover a second region.

10. A method for wirelessly transmitting an audio signal using a wireless audio transmitter, the method comprising: (A) receiving a selection of one of a plurality of modes of the wireless audio transmitter from a mode selection interface; (B) receiving at an encoder (i) data symbols including an audio data signal and a control signal and (ii) pilot symbols; (C) when the selection is a first mode, routing the data symbols and the pilot symbols to each of a plurality of converters using the encoder; (D) When the selection is the second mode: encoding the data symbols and the pilot symbols based on a first diversity technique using the encoder; and routing, using the encoder, coded data symbols and coded pilot symbols to one or more subsets of the plurality of switches; (E) receiving a synchronization signal at a synchronous converter; (F) converting the synchronization signal based on a second diversity technique using the synchronous converter; (G) when the selection is the first mode, combining, using each of the plurality of converters, the data symbols, the pilot symbols, and the transformed synchronization signal into the audio signal to be transmitted on one of a plurality of antennas; as well as (H) When the selection is the second mode, using converters in the one or more subsets of the plurality of converters to combine the encoded data symbols, the encoded pilot symbols, and the transformed synchronization signal into the audio signal to be transmitted on one of the plurality of antennas.

11. The method of claim 10, wherein the first diversity technique comprises space-time block coding in the frequency domain.

12. The method of claim 11, wherein the space-time block code comprises an Alamoti rate-1 code.

13. The method of claim 10, wherein transforming the synchronization signal based on the second diversity technique comprises transforming the synchronization signal by applying a phase ramp to the synchronization signal using a phase shifter in the synchronous converter.

14. The method of claim 10, wherein the second diversity technique comprises a round-robin diversity scheme.

15. The method of claim 10, wherein the pilot symbols are orthogonal.

16. The method of claim 10, wherein: combining the data symbols, the pilot symbols, and the transformed synchronization signal when the selection is the first mode includes combining using an inverse fast Fourier transform and a parallel-to-serial converter in each of the plurality of converters; and Combining the encoded data symbols, the encoded pilot symbols, and the transformed synchronization signal when the selection is the second mode includes combining using the inverse fast Fourier transform and the parallel-to-serial converter in each of the plurality of converters.

17. The method according to claim 10: wherein combining the data symbols, the pilot symbols, and the transformed synchronization signal when the selection is the first mode comprises combining using a cyclic delay module in each of the plurality of converters; wherein combining the coded data symbols, the coded pilot symbols, and the transformed synchronization signal when the selection is the second mode comprises combining using the cyclic delay module in each of the plurality of converters; and The delay amount of the cyclic delay module depends on the selected mode among the multiple modes.

18. The method of claim 10, further comprising: transmitting the audio signal on a first subset of the plurality of antennas configured to cover a first region; as well as The audio signal is transmitted on a second subset of the plurality of antennas configured to cover a second region.

19. A wireless audio system comprising: an audio source configured to generate one or more audio source signals each comprising a data symbol, the data symbols comprising an audio data signal and a control signal; a wireless audio transmitter in communication with the audio source, the wireless audio transmitter comprising: (A) a plurality of antennas configured to each transmit an audio signal; (B) an encoder in communication with the audio source, the encoder configured to receive and encode the data symbols and pilot symbols based on a first diversity technique; (C) a synchronous converter in communication with the audio source, the synchronous converter configured to receive and convert a synchronization signal based on a second diversity technique; and (D) a plurality of converters, each in communication with the encoder, the synchronous converter, and one of the plurality of antennas, wherein each of the plurality of converters is configured to combine encoded data symbols, encoded pilot symbols, and transformed synchronization signals into the audio signal to be transmitted on one of the plurality of antennas; and A wireless audio receiver in wireless communication with the wireless audio transmitter, the wireless audio receiver configured to receive the audio signal on at least one receive antenna.

20. The wireless audio system of claim 19, wherein the first diversity technique comprises space-time block coding in the frequency domain and the second diversity technique comprises a round-robin diversity scheme.

21. The wireless audio system of claim 19, wherein the audio signal is transmitted by the wireless audio transmitter to the wireless audio receiver via a multiple-input multiple-output scheme.

22. The wireless audio system of claim 21, wherein the at least one receive antenna of the wireless audio receiver comprises a plurality of receive antennas.

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