Transmit antenna diversity wireless audio system

Abstract

The invention relates to a transmit antenna diversity wireless audio system. A wireless audio system is provided that includes a transmitter that uses multiple antenna diversity techniques for different signal types. The multipath performance can be optimized, and the spectral efficiency of the system can be improved.

Description

[0001] Information related to divisional application

[0002] This case is a divisional application. The parent application of this divisional application is the invention patent application filed on July 30, 2020, with application number 202080064964.6 and invention title "Transmitting Antenna Diversity Wireless Audio System".

[0003] Cross-references to related applications

[0004] This application claims priority to U.S. Provisional Patent Application No. 62 / 882,980, filed August 5, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0005] This application generally relates to wireless audio systems utilizing transmit antenna diversity. More specifically, this application relates to wireless audio systems having a transmitter employing various antenna diversity techniques for different signal types. Background Technology

[0006] Audio production can involve the use of numerous components, including microphones, wireless audio transmitters, wireless audio receivers, recorders, and / or mixers, to capture, record, and present the produced sound, such as television programs, news, films, live events, and other types of productions. Microphones typically capture the produced sound, which is wirelessly transmitted from the microphone and / or wireless audio transmitter to the wireless audio receiver. The wireless audio receiver can connect to the recorder and / or mixer for recording and / or mixing sound via a crew member, such as in a sound mixing machine. Electronic devices, such as computers and smartphones, can connect to the recorder and / or mixer to allow the crew member to monitor audio levels and timecode.

[0007] 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, etc.

[0008] A wireless audio transmitter transmits an RF signal containing audio signals to a wireless audio receiver. The wireless audio transmitter may be contained, for example, in a wireless handheld microphone or bag held or worn by a user and containing an integrated transmitter and antenna. As another example, the wireless audio transmitter may be contained in an access point or other centralized unit. The wireless audio receiver may be portable, such as a wireless headset, wireless conferencing unit, or bag. When an RF signal is received at the wireless audio receiver, the RF signal may be attenuated due to multipath fading caused by constructive interference and / or other types of interference. This attenuation can result in a poor signal-to-noise ratio (SNR) for the RF signal, which can lead to bit errors that can cause audio artifacts and noise suppression of the resulting output audio. However, noise suppression of the output audio is undesirable in many situations and environments, such as during professional stage productions and concerts. The effects of such multipath fading and interference are most prevalent in harsh RF environments where physical and electrical factors affect the transmission and reception of RF signals, such as microphone movement within the environment, other RF signals, operation in large venues, etc.

[0009] To mitigate the problem of multipath fading in 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 from a combined RF signal on a single antenna, wherein 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 on multiple antennas. The received RF signals can be combined to produce a single audio output.

[0010] 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.

[0011] Other techniques used to mitigate multipath fading in RF signals may have undesirable side effects. For example, the transmit power of a wireless audio transmitter can be increased to account for a larger fading margin. However, when the transmit power is increased, the overall spectral efficiency may be negatively affected due to intermodulation products. Furthermore, the physical design of the transmitter and / or government regulations may limit the possible increase in transmit power. Additionally, increased transmit power cannot resolve the error floor caused by frequency-selective fading. As another example, antennas can be designed to concentrate the signal energy transmitted from the wireless audio transmitter to the wireless audio receiver. However, such antennas may be too directive, which could affect the coverage range of the wireless audio transmitter. As yet another example, in some applications (e.g., wireless in-ear personal monitors), specialized signal decomposition techniques can be used to attempt to improve diversity performance. However, such techniques may introduce phase cancellation problems, potentially leading to performance degradation and unreliability.

[0012] Therefore, there is an opportunity to develop wireless audio systems that utilize transmit antenna diversity to address these concerns. More specifically, there is an opportunity to develop wireless audio systems with transmitters that use multiple antenna diversity techniques for different signal types, which can optimize multipath performance and improve spectral efficiency. Summary of the Invention

[0013] The present invention aims to solve the above-mentioned problems by providing a wireless audio system utilizing transmit antenna diversity, the wireless audio system being designed to include, among other things: (1) simultaneously applying different transmit diversity techniques depending on the type of signal being transmitted, such as data / control symbols, pilot symbols, and synchronization signals; (2) performing independent channel estimation and coherent demodulation using embedded orthogonal pilot symbols while maintaining an ideal data rate; and (3) flexibly encoding and / or routing to multiple antennas to increase coverage and / or capacity.

[0014] In one embodiment, a wireless audio transmitter includes: a mode selection interface for enabling a user to select one of multiple modes of the wireless audio transmitter; a plurality of antennas configured to each transmit an audio signal; an encoder communicating with the mode selection interface, wherein the encoder is configured to receive (i) data symbols including audio data signals and control signals and (ii) pilot symbols; a synchronization converter; and the plurality of converters each communicating with the encoder, the synchronization converter, and one of the plurality of antennas. The encoder may be further configured to: when in a first mode, receive the data symbols and the pilot symbols and route them to each of the 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.

[0015] The synchronization converter can be configured to receive and transform synchronization signals based on a second diversity technique. Each of the converters can be configured to: when in the first mode, 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 in the second mode, 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.

[0016] In another embodiment, a method for wirelessly transmitting audio signals 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 (i) data symbols including audio data signals and control signals and (ii) pilot symbols at an encoder; 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; and when the selection is a second mode: encoding the data symbols and the pilot symbols using the encoder based on a first diversity technique, and routing the encoded data symbols and the encoded pilot symbols to one or more subsets of the plurality of converters using the encoder. The method may further include: receiving a synchronization signal at a synchronization converter; transforming the synchronization signal using the synchronization converter based on a second diversity technique; when the selection is the first mode, combining the data symbols, the pilot symbols, and the transformed synchronization signal using each of the plurality of converters into the audio signal to be transmitted on one of the plurality of antennas; and when the selection is the second mode, combining the encoded data symbols, the encoded pilot symbols, and the transformed synchronization signal using one or more subsets of the plurality of converters into the audio signal to be transmitted on one of the plurality of antennas.

[0017] In another embodiment, a wireless audio system may include: an audio source; a wireless audio transmitter communicating with the audio source; and a wireless audio receiver communicating wirelessly 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 audio data signals and control signals. The wireless audio transmitter may include: a plurality of antennas configured to transmit audio signals; an encoder communicating with the audio source and configured to receive and encode the data symbols and pilot symbols based on a first diversity technique; a synchronization converter communicating with the audio source and configured to receive and transform synchronization signals based on a second diversity technique; and a plurality of converters each communicating with the encoder, the synchronization 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 transformed synchronization signals 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 receiving antenna.

[0018] These and other embodiments, as well as various combinations and aspects, will become apparent and will be more fully understood from the following detailed description and accompanying drawings, which illustrate illustrative embodiments indicating various ways in which the principles of the invention can be applied. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a wireless audio system utilizing transmit antenna diversity according to some embodiments.

[0020] Figure 2 This is a schematic diagram of a portion of a wireless audio transmitter that utilizes two antennas for transmit diversity, according to some embodiments.

[0021] Figure 3 This is a schematic diagram of a portion of a wireless audio transmitter that utilizes four antennas for transmit diversity, according to some embodiments.

[0022] Figure 4 The following is a flowchart illustrating, according to some embodiments, an operation for wirelessly transmitting audio signals using a wireless audio transmitter that utilizes transmit antenna diversity.

[0023] Figure 5 The table below illustrates, according to some embodiments, the encoding of data symbols and pilot symbols using space-time block coding of a wireless audio transmitter for transmit diversity with two antennas.

[0024] Figure 6 This is an exemplary graph illustrating the performance of a wireless audio system that utilizes two antennas for transmit diversity, according to some embodiments.

[0025] Figure 7A , 7B 8A, 8B, and 9 are exemplary depictions of encoding and / or routing audio channels to converters and antennas in different modes of a wireless audio transmitter, according to some embodiments. Detailed Implementation

[0026] The following description illustrates, describes, and exemplifies one or more specific embodiments of the invention based on its principles. This specification 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 those skilled in the art can understand these principles and, through this understanding, apply them to practice not only the embodiments described herein, but also other embodiments conceivable based on these principles. The scope of the invention is intended to cover all such embodiments that are literally or under the principle of equivalence within the scope of the appended claims.

[0027] It should be noted that similar or substantially similar elements may be labeled with the same reference numerals in the description and figures. However, sometimes these elements may be labeled with different numerals, for example, where such labeling helps to describe things more clearly. Furthermore, the figures illustrated herein are not necessarily drawn to scale, and in some cases, the scale may have been enlarged to depict certain features more clearly. Such labeling and drawing practices do not necessarily imply any underlying material purpose. As stated above, this specification is intended to be considered as a whole and to be interpreted according to the principles of the invention as taught herein and as understood by one of ordinary skill in the art.

[0028] The wireless audio system described herein can utilize transmit antenna diversity by incorporating transmitters employing 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 systems with non-diversity wireless audio transmitters, wireless audio systems with transmit antenna diversity can maintain a consistent and constant data rate. The number of antennas utilized by the wireless audio transmitter can be optional, scalable, and extendable to achieve greater coverage and / or capacity. Furthermore, even if a particular transmit path fails, the wireless audio system can still operate with reduced range and / or performance. The performance of the wireless audio system can be more stable in both single zones (e.g., stage) and multiple zones (e.g., stage and backstage).

[0029] Figure 1 This 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. The 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 spaced apart). It is contemplated and possible that the transmitter 110 has more than two antennas and any number of receivers 150. In some embodiments, the transmitter 110 may be an access point or other centralized unit. In some embodiments, the receivers 150a, 150b, 150c may be portable wireless audio receivers, such as wireless headphones, wireless conferencing units, or handbags.

[0030] In one embodiment, system 100 may be an orthogonal frequency division multiplexing (OFDM) wideband audio system, which allows various types of traffic to be carried on individual subcarriers and multiplexed together onto 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, pilot symbols, and / or synchronization signals having audio data signals and control signals. In some embodiments, data symbols may be QPSK / QAM modulated subcarriers capable of carrying audio data signals and / or control signals. Pilot symbols may be known symbols capable of enabling channel estimation and coherent demodulation of the signal at receiver 150.

[0031] 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 the 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.

[0032] A synchronization signal can be transmitted from transmitter 110 so that receiver 150 can obtain a frequency and / or timing reference for system 100. Transmitter 110 and receiver 150 typically need to be synchronized with each other to properly transmit and receive data symbols and pilot symbols. For example, the frequency and phase of receiver 150's local oscillator 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 can be applied to the synchronization signal. Therefore, data symbols, pilot symbols, and synchronization signals can utilize different antenna diversity techniques.

[0033] System 100 may also include an audio source 120 that communicates with transmitter 110. Audio source 120 may generate one or more audio source signals, including data symbols having audio data signals and control signals. Transmitter 110 may modulate the data symbols from audio source 120 and insert pilot symbols and synchronization symbols before transmitting RF signals on antennas 112a and 112b.

[0034] Figure 2 This is a schematic diagram of a portion of a wireless audio transmitter 210 that uses two antennas 212a and 212b for transmit diversity. For simplicity... Figure 2 Other components of transmitter 210, such as modulators, analog-to-digital converters, digital-to-analog converters, encoders / decoders, etc., are not shown. Transmitter 210 can transmit RF signals containing data symbols, pilot symbols, and / or synchronization signals for one or more receivers (e.g., Figure 1The receiver 150 in the wireless audio system 100 receives the audio. The various components included in the wireless audio transmitter 210 may be implemented using software that can be executed by one or more servers or computers (e.g., computing devices with processors and memory), and / or can be implemented using hardware (e.g., discrete logic circuits, application-specific integrated circuits (ASICs), programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.).

[0035] Figure 4 An embodiment of a process 400 for wirelessly transmitting audio signals using a wireless audio transmitter employing transmit antenna diversity is illustrated. Process 400 may be executed by a transmitter 210. One or more processors and / or other processing components (e.g., analog-to-digital converters, encryption chips, etc.) internal or external to the transmitter 210 may execute any, some, or all of the steps of process 400. Alternatively, a processor and / or other processing components may be combined with one or more other types of components (e.g., memory, input and / or output devices, transmitters, receivers, buffers, drivers, discrete components, etc.) to execute any, some, or all of the steps of process 400.

[0036] Transmitter 210 can generate signals including data symbols, pilot symbols, and synchronization signals for transmission on antennas 212a and 212b. Data symbols may include audio data signals and / or control signals. Control signals may include system messages and other information. Encoder 214 may have multiple operating modes, allowing the encoding and / or routing of data symbols and pilot symbols for eventual transmission on antennas 212a and 212b. At step 402, a selection of modes 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.

[0037] The synchronization signal can be in the frequency domain or the time domain and can be transformed using cyclic delay diversity (CDD) technology for transmission on antennas 212a and 212b. At step 406, the synchronization signal can be received by synchronization converter 218. CDD can be applied to the synchronization signal so that no zero values ​​appear in the radiation patterns of antennas 212a and 212b. Specifically, at step 408, a phase ramp can be applied by synchronization converter 218. The synchronization signal can be transformed in the frequency domain, or it can be transformed by the synchronization converter 218 using a cyclic delay in the time domain. Therefore, the first antenna 212a can transmit an 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 and 212b shown are merely exemplary. In some embodiments, the synchronization signal may be transformed by the synchronization converter 218 in a round-robin diversity scheme.

[0038] Depending on the selected mode, at step 410, converters 216a and 216b may combine data symbols and pilot symbols (whether encoded or unencoded) with a synchronization signal. For example, in a first mode of transmitter 210, the data symbols and pilot symbols may not be encoded by encoder 214 and routed to converters 216a and 216b at step 412. At step 414, converters 216a and 216b may then combine the data symbols, pilot symbols, and transformed synchronization signal into an audio signal transmitted as an RF signal on antennas 212a and 212b. In another example, in a second mode of transmitter 210, the data symbols and pilot symbols may be encoded by encoder 214 at step 416 and routed to converters 216a and 216b at step 418. At step 420, converters 216a and 216b can combine encoded data symbols, encoded pilot symbols, and transformed synchronization signals into an audio signal transmitted on antennas 212a and 212b.

[0039] In this embodiment, transmitter 210 may be an OFDM wideband transmitter, and data symbols and pilot symbols may be mapped in the frequency domain by space-time block coding (STBC) in encoder 214. Data symbols may be QPSK / QAM modulated subcarriers. Figure 5 As shown in the table, 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 At that time, the first antenna 212a can transmit the same symbol pair s n,0 s n,1 The second line 212b can emit symbol pairs s * n,0 -s * n,1 (That is, the complex conjugate of the input symbol pair). Specifically, as is known in the art, encoder 214 can use an STBC to receive and encode the input symbol pair to generate symbols for transmission on antennas 212a, 212b. In embodiments, the code may be a rate-1 STBC (known from Alamouti) or another suitable code.

[0040] Pilot symbols can be known symbols used for channel estimation and coherent demodulation of the signal at the receiver. In embodiments, pilot symbols can be orthogonal sequences. For example... Figure 5As shown in the table, the STBC encoder 214 can process a pair of pilot symbols with a value of +1 and generate orthogonal pilot patterns on antennas 212a and 212b. For example, when the input symbol pair of the pilot symbols 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 this embodiment, the pilot symbols can be orthogonal in the code domain, rather than in the time or frequency domain. This ensures that the capacity is not reduced due to the presence of unique pilots on multiple antennas. Additionally, in this embodiment, the pilot symbols can use the same STBC mapping as the data symbols, which helps reduce the complexity of the implementation.

[0041] For example, one or more receivers 150a, 150b, 150c can receive RF signals containing audio signals transmitted from transmitter 210 on their respective antennas, such as antennas 152a, 152b, 152c. The receivers can demodulate, convert, and / or process the received RF signals to generate analog or digital output audio signals, as known in the art. Specifically, the receivers can decode data symbols and pilot symbols based on the symbol encoding method (e.g., Alamoti rate-1STBC). In embodiments, the receivers may each have multiple antennas simultaneously receiving transmitted RF signals from transmitter 210 in a spatial diversity scheme. When both the transmitter and receivers have spatial diversity, multiple-input multiple-output (MIMO) techniques can be utilized. For example, using MIMO can increase diversity gain for fading mitigation due to the lower bit error rate in fading environments. As another example, the use of MIMO can produce higher throughput, i.e., more bits per frequency, due to spatial multiplexing.

[0042] exist Figure 6 As can be seen from the exemplary graph, the performance of a 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 (dashed line) of a wireless audio system 100 with two antenna diversity is shown compared to that of a single-antenna wireless audio system (solid line). Therefore, at low BER rates (e.g., less than 10), the performance is significantly better. -5 Under these conditions, the performance of the wireless audio system 100 with two antenna diversity is approximately 5 dB better. It should be noted that... Figure 6 The graph shows that the combined transmit power of a wireless audio system 100 with two antenna diversity is equal to the transmit power of a single-antenna wireless audio system.

[0043] Figure 3 This 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. For simplicity... Figure 3Other components of transmitter 310, such as modulators, analog-to-digital converters, digital-to-analog converters, encoders / decoders, etc., are not shown. Transmitter 310 can transmit RF signals containing data symbols, pilot symbols, and / or synchronization signals for one or more receivers (e.g., Figure 1 The receiver 150 in the wireless audio system 100 receives the audio. The various components included in the wireless audio transmitter 310 may be implemented using software that can be executed by one or more servers or computers (e.g., computing devices with processors and memory), and / or can be implemented using hardware (e.g., discrete logic circuits, application-specific integrated circuits (ASICs), programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.).

[0044] Similar to Figure 2 Transmitter 210 and transmitter 310 generate signals containing data symbols, pilot symbols, and synchronization signals for transmission on antennas 312a, 312b, 312c, and 312d. Data symbols may contain audio data signals and / or control signals. Control signals may contain 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 code (STBC) encoder 314. In embodiments, 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 or time domain and may be transformed using cyclic delay diversity (CDD) techniques for transmission on antennas 312a, 312b, 312c, and 312d. Alternatively, in a round-robin diversity scheme, the synchronization signal can be transmitted on antennas 312a, 312b, 312c, and 312d. Detailed implementation methods are omitted. Figure 2 The synchronous converter 218 has the same or similar functionality. Figure 3 The functionality of the synchronous converter 318.

[0045] Figure 4 The embodiment of process 400 shown can also be executed by transmitter 310. One or more processors and / or other processing components (e.g., analog-to-digital converters, encryption chips, etc.) inside or outside transmitter 310 can execute any, some, or all of the steps of process 400. Processes and / or other processing components can also be combined with one or more other types of components (e.g., memory, input and / or output devices, transmitters, receivers, buffers, drivers, discrete components, etc.) to execute any, some, or all of the steps of process 400.

[0046] The STBC encoder 314 may have multiple operating modes, allowing the encoding and / or routing of data symbols and pilot symbols for eventual transmission on antennas 312a, 312b, 312c, and 312d. At step 402, a selection of modes for the STBC encoder 314 and transmitter 310 may be received, for example, from a user interface. The selected mode determines the type (if any) of mapping and routing performed by the STBC encoder 314. In one embodiment, transmitter 310 may have three modes, while in other embodiments, transmitter 310 may have another number of modes. The number of modes for transmitter 310 may depend on the number of antennas, the number of coverage areas, and / or the number of audio channels.

[0047] The first mode of transmitter 310 enables STBC encoder 314 to receive (step 404) data symbols and pilot symbols and route (step 412) them to converters 316a, 316b, 316c, 316d that communicate accordingly with antennas 312a, 312b, 312c, 312d, without utilizing any STBC mapping. This mode can route up to N audio channels to N coverage areas, where N equals the number of antennas. Therefore, for transmitter 310, up to four audio channels can be routed to four coverage areas. For example, in this mode, 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 As depicted. This mode can, for example, cover multiple areas along a parade route. As another example, in this mode, the STBC encoder 314 can route four distinct audio channels (i.e., four separate data symbol and pilot symbol streams) to four corresponding single-antenna coverage areas, such as... Figure 7B What is depicted.

[0048] The second mode of transmitter 310 enables STBC encoder 314 to receive (step 404) data symbols and pilot symbols using a 2-branch STBC mapping and encode them (step 416). The encoded data symbols and pilot symbols can be routed (step 418) to converters 316a, 316b, 316c, 316d that communicate with antennas 312a, 312b, 312c, 312d respectively. This mode can encode and route up to N / 2 audio channels to N / 2 coverage areas; for example, for transmitter 310, up to two audio channels can be encoded and routed to two coverage areas. For example, in this mode, STBC encoder 314 can encode and route one audio channel (i.e., one stream of data symbols and pilot symbols) to two coverage areas, each with two antennas, such as... Figure 8AAs depicted. Specifically, one coverage area may be covered by antennas 312a and 312b, and another coverage area may be covered by antennas 312c and 312d. As another example, in this mode, the STBC encoder 314 can encode and route two distinct audio channels (i.e., two separate data symbol and pilot symbol streams) to two corresponding coverage areas, each with two antennas, as shown. Figure 8B What is depicted.

[0049] The third mode of transmitter 310 enables STBC encoder 314 to receive (step 404) data symbols and pilot symbols using a 4-branch STBC mapping and encode them (step 416). The encoded data symbols and pilot symbols can be routed (step 418) to converters 316a, 316b, 316c, 316d that communicate accordingly with antennas 312a, 312b, 312c, 312d. This mode can encode and route up to N / 4 audio channels to N / 4 coverage areas; for example, for transmitter 310, it can encode and route up to one audio channel to one coverage area. For example, in this mode, STBC encoder 314 can encode and route one audio channel (i.e., one stream of data symbols and pilot symbols) to one coverage area with four antennas, such as... Figure 9 What is depicted.

[0050] Converters 316a, 316b, 316c, and 316d can combine data symbols, pilot symbols, and synchronization signals, for example, in the first mode described above where no encoding is present (step 414); or combine encoded data symbols, encoded pilot symbols, and synchronization signals, for example, in the second and third modes described above (step 420). Converters 316a, 316b, 316c, and 316d can generate audio signals transmitted on antennas 312a, 312b, 312c, and 312d, respectively.

[0051] Each of converters 316a, 316b, 316c, and 316d may include inverse fast Fourier transform (IFFT) 320a, 320b, 320c, and 320d to convert data symbols and pilot symbols into the time domain. The output of the synchronization converter 318 (i.e., the transformed synchronization signal) may also be transmitted to IFFT 320a, 320b, 320c, and 320d. The outputs of the corresponding IFFT 320a, 320b, 320c, and 320d may be converted by parallel-to-serial converters 322a, 322b, 322c, and 322d. To transmit audio signals on antennas 312a, 312b, 312c, and 312d, cyclic delays 324a, 324b, 324c, and 324d may be applied to the outputs of parallel-to-serial converters 322a, 322b, 322c, and 322d. Each cycle delay may result in a unique time shift on each antenna. Specifically, the outputs of the parallel-to-serial converters 322a, 322b, 322c, and 322d may contain data symbols, pilot symbols, and synchronization signals in the time domain, i.e., after conversion by IFFT 320a, 320b, 320c, and 320d. As previously discussed, the data symbols and pilot symbols may have been encoded in some modes and may not have been encoded in others.

[0052] For example, one or more receivers 150a, 150b, 150c can receive RF signals containing audio signals transmitted from transmitter 310 on their respective antennas, such as antennas 152a, 152b, 152c. The receivers can demodulate, convert, and / or process the received RF signals to generate analog or digital output audio signals, as known in the art. Specifically, the receivers can decode data symbols and pilot symbols based on a symbol encoding scheme, such as Alamoti rate-1STBC, Quasi-orthogonal Jafarhani rate-1STBC, orthogonal Ganesean rate-3 / 4STBC. In embodiments, the receivers may each have multiple antennas simultaneously receiving transmitted RF signals from transmitter 310 in a spatial diversity scheme.

[0053] As will be understood by those skilled in the art, any process description or block in the accompanying drawings should be understood as representing a module, fragment, or code portion containing one or more executable instructions for implementing a specific logical function or step in the process, and alternative embodiments are included within the scope of the embodiments of the invention, in which functions may be performed in a different order than shown or discussed, including functions performed substantially simultaneously or in reverse order, depending on the functionality involved.

[0054] This disclosure is intended to explain how to design and use various embodiments of the technology according to the invention, and not to limit the true, established, and fair scope and spirit of the invention. The foregoing description is not intended to be exhaustive or limited to the exact form disclosed. In view of the foregoing teachings, modifications and variations are possible. The embodiments were chosen and described to provide the best illustration of the principles of the described inventive technology and its practical application, and to enable one skilled in the art to utilize the inventive technology in various embodiments and with various modifications suitable for the particular intended use. All such modifications and variations, and all their equivalents, are within the scope of the embodiments as defined by the appended claims when interpreted according to the breadth of the rights clearly, lawfully, and fairly conferred. Amendments may be made while this patent application is pending.

Claims

1. A wireless audio transmitter, comprising: Multiple antennas; Multiple converters that communicate with the multiple antennas; The encoder, which is configured to: Receive one or more symbols based on the first diversity technique and encode the one or more symbols; and The encoded one or more symbols are routed to one or more converters among the plurality of converters; and A synchronous converter configured to receive and transform synchronization signals based on a second diversity technique. Each of the plurality of converters communicates with a corresponding antenna among the encoder, the synchronous converter, and the plurality of antennas, and each of the one or more converters is configured to: The encoded one or more symbols are combined with the transformed synchronization signal to generate a combined audio signal for transmission via a corresponding antenna among the plurality of antennas.

2. The wireless audio transmitter of claim 1, wherein the one or more symbols include at least one data symbol, control symbol, or pilot symbol.

3. The wireless audio transmitter according to claim 1, wherein the first diversity technique includes space-time block coding in the frequency domain.

4. The wireless audio transmitter of claim 1, wherein the second diversity technique comprises at least one of the following: Cyclic Delay Diversity (CDD) technique; or Round-robin diversity technique.

5. The wireless audio transmitter of claim 1, wherein at least some of the plurality of converters are configured to use inverse fast Fourier transform.

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

7. The wireless audio transmitter of claim 1, wherein the plurality of antennas are configured to transmit audio signals to a wireless audio receiver via a multiple-input multiple-output (MIMO) scheme.

8. The wireless audio transmitter according to claim 1, wherein: The encoder is further configured to receive one or more second symbols and route them to each of the plurality of converters; The synchronization converter is further configured to receive and transform the second synchronization signal based on the second diversity technique; and Each of the plurality of converters is configured to: The one or more second symbols are combined with the transformed second synchronization signal to generate a second combined audio signal for transmission via a corresponding one of the plurality of antennas.

9. A method comprising: Encoding one or more symbols based on the first diversity technique; The encoded one or more symbols are routed to one or more converters among a plurality of converters; The synchronization signal is transformed based on the second diversity technique; At each of the one or more converters, the encoded one or more symbols and the transformed synchronization signal are combined to generate a combined signal; and The combined signal is transmitted via a corresponding antenna among multiple antennas.

10. The method of claim 9, wherein the one or more symbols include at least one data symbol, control symbol, or pilot symbol.

11. The method of claim 9, wherein the first diversity technique comprises space-time block coding in the frequency domain.

12. The method of claim 9, wherein the second diversity technique comprises at least one of the following: Cyclic Delay Diversity (CDD) technique; or Round-robin diversity technique.

13. The method according to claim 9, wherein: A first subset of the plurality of antennas is configured to cover a first region; and A second subset of the plurality of antennas is configured to cover the second region.

14. The method of claim 9, further comprising: Route one or more second symbols to each of the plurality of converters; The second synchronization signal is transformed based on the second diversity technique; At each of the plurality of converters, the one or more second symbols and the transformed second synchronization signal are combined to generate a second combined audio signal; and The second combined audio signal is transmitted via a corresponding antenna among the plurality of antennas.

15. A non-transitory computer-readable medium having instructions stored thereon that, when executed, cause: At the transmitter, one or more symbols are encoded based on the first diversity technique; The encoded one or more symbols are routed to one or more converters among a plurality of converters; The synchronization signal is transformed based on the second diversity technique; At each of the one or more converters, the encoded one or more symbols and the transformed synchronization signal are combined to generate a combined signal; and The combined signal is transmitted via a corresponding antenna among multiple antennas.

16. The non-transitory computer-readable medium of claim 15, wherein the one or more symbols comprise at least one data symbol, control symbol, or pilot symbol.

17. The non-transitory computer-readable medium of claim 15, wherein the first diversity technique comprises space-time block coding in the frequency domain.

18. The non-transitory computer-readable medium of claim 15, wherein the second diversity technique comprises at least one of the following: Cyclic Delay Diversity (CDD) technique; or Round-robin diversity technique.

19. The non-transitory computer-readable medium according to claim 15, wherein: A first subset of the plurality of antennas is configured to cover a first region; and A second subset of the plurality of antennas is configured to cover the second region.

20. The non-transitory computer-readable medium of claim 15, wherein the instructions, when executed, cause: Route one or more second symbols to each of the plurality of converters; The second synchronization signal is transformed based on the second diversity technique; At each of the plurality of converters, the one or more second symbols and the transformed second synchronization signal are combined to generate a second combined audio signal; and The second combined audio signal is transmitted via a corresponding antenna among the plurality of antennas.

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