Spread spectrum based audio frequency communication system

A spread spectrum based audio frequency communication system at least includes a transmitting apparatus. The transmitting apparatus includes a first dot-product module, a summation module, a transmitting modulation module, a mixture module, a digital-to-analog converter, and a transmitter. The first dot-product module is configured to perform a dot-product of a first data and a first pseudo-noise code, and derive a first spreading data. The summation module is configured to sum up the first spreading data and a second spreading data to form a summed data. The transmitting modulation module is configured to vary a carrier signal with the summed data to form a modulated signal. The mixture module is configured to mix the modulated signal and an acoustic signal up to form a mixed signal. The digital-to-analog converter is configured to convert the mixed signal into acoustic waves. The transmitter transmits the acoustic waves.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system and, more particularly, to a spread spectrum based audio frequency communication system and an audio band signaling system for distance detection.

2. Description of Related Art

The most common wireless technology uses radio waves, which belong to electromagnetic waves within spectrum from 3 Hz to 3 THz. A traditional wireless communication system requires radio frequency (RF) modules for signal transmission. The RF modules typically incorporate a printed circuit board, transmit or receive circuit, antenna, and serial interface for communication to the host processor. The manufacturing of the RF modules causes additional bills of materials (BOM) cost.

In other aspect, there are different wireless communication protocols, which are incompatible with each other. For example, it is difficult to build a communication among smartphones, home entertainments and wearables with a single protocol. The diversity of the protocols limits the application of machine to machine (M2M) communication.

Therefore, it is desirable to provide an improved wireless communication system to mitigate and/or obviate the aforementioned problems.

SUMMARY OF THE INVENTION

The present invention introduces a “whistle technology”, which allows transferring data signals in audio band. Various intrinsic properties of acoustic waves may be combined with the data signals carried therein, thereby realizing various useful applications.

Most of devices already have speakers and/or microphones adapted to the whistle technology according to the present invention, and thus do not require RF modules for wireless communication. A cost effective wireless communication can therefore be achieved.

In a first aspect, the present invention provides a spread spectrum based audio frequency communication system at least including a transmitting apparatus. The transmitting apparatus includes a first dot-product module, a summation module, a transmitting modulation module, a mixture module, a digital-to-analog converter, and a transmitter. The first dot-product module is configured to perform a dot-product of a first data and a first pseudo-noise (PN) code, and derive a first spreading data. The summation module is configured to sum up the first spreading data and a second spreading data to form a summed data. The transmitting modulation module is configured to vary a carrier signal with the summed data to form a modulated signal. The mixture module is configured to mix the modulated signal and an acoustic signal to form a mixed signal. The digital-to-analog converter is configured to convert the mixed signal into acoustic waves. The transmitter transmits the acoustic waves.

Preferably, the transmitting apparatus is adapted to be paired with a receiving apparatus with a complementary structure.

Similarly, the transmitting apparatus may further include a second dot-product module configured to perform a dot-product of a second data and a second PN code, and derive the second spreading data. Optionally, the first PN code and the second PN code are chosen to be orthogonal to each other.

Preferably, the acoustic signal carries voice or audio in digital form.

Preferably, the transmitter is a speaker with beamforming capability in a speaker array.

Preferably, the acoustic waves have data component and voice/audio component, and the data component appears as a background noise of the voice/audio component.

In a second aspect, the present invention provides a spread spectrum based audio frequency communication system at least including a receiving apparatus. The receiving apparatus includes a receiver, an analog-to-digital converter, a receiving modulation module, and a first dot-product module. The receiver receives acoustic waves. The analog-to-digital converter is configured to convert the acoustic waves into a mixed signal. The receiving modulation module is configured to recover summed data from the mixed signal with a carrier signal. The first dot-product module is configured to perform a dot-product of the summed data and a first pseudo-noise (PN) code, and derive a first data.

Accordingly, the data component of the acoustic waves is derived. While, in order further to derive the voice/audio component of the acoustic waves, the receiving apparatus may further includes an interference cancellation module, a delay module, and a mixture module. The interference cancellation module is configured to generate an interference signal from the first data. The delay module is configured to delay the mixed signal to form a delayed signal. The mixture module is configured to subtract the interference signal from the delayed signal to derive an acoustic signal.

Similarly, the receiving apparatus may further include a second dot-product module configured to perform a dot-product of the summed data and a second PN code, and derive a second data.

Preferably, the receiving apparatus is adapted to be paired with a transmitting apparatus with a complementary structure.

Preferably, the receiver is a microphone with beamforming capability in a microphone array. Moreover, the microphone array may have a plurality of virtual groups in term of different functions. Furthermore, the virtual groups may include a first group used to receive beam from a direction, a second group used to receive beam from another direction, and a third group used for noise estimation and/or reduction.

Preferably, the receiving modulation module is a demodulator.

In addition, a plurality of the same spread spectrum based audio frequency communication systems may form an ad-hoc network, and any spread spectrum based audio frequency communication system may serve as a node thereof.

In a third aspect, the present invention provides an audio band signaling system for distance detection including a transmitting apparatus and a receiving apparatus.

The transmitting apparatus includes a spreading module, a mixture module, and a transmitter. The spreading module is configured to modulate a detecting signal S(t) with a high-bandwidth pseudo random binary sequence (PRBS), and output a spread signal. The mixture module is configured to mix the spread signal and an acoustic signal up to form mixed acoustic waves. The transmitter transmits the mixed acoustic waves.

The receiving apparatus includes a receiver, a de-spreading module, and a detection module. The receiver receives the mixed acoustic waves. The de-spreading module is configured to demodulate the mixed acoustic waves with the same PRBS, and return it to the detecting signal S(t). The detection module is configured to detect and analyze the detecting signal S(t).

Moreover, the transmitting apparatus may further include an extra-processing module as a bypass module or a domain transform module, and the receiving apparatus may further include another extra-processing module as another bypass module or another domain transform module.

Preferably, the detecting signal S(t) includes identity information, time information, or other properties helpful to distance detection. In addition, different mixed acoustic waves used to detect different objects at same time are distinguished by the identity information.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a “whistle technology” in wireless communication. The whistle technology aims to transfer signals through audio band. It uses spread-spectrum techniques for signal modulation and/or demodulation, and the spread signal sounds like background noise.

The whistle technology can leverage the existing audio/voice interface, for example, by using a speaker as a transmitter, and using a microphone as a receiver, which both commonly exist in a smart device. Thus, it does not need an RF antenna or a dedicated wireless communication circuit. The whistle technology may be enabled by either a software program of audio and/or voice drivers or a high-level application program (APP), and it may be built in a terminal device or on a cloud server.

When there are multiple users, the code division multiple access (CDMA) technology may be introduced into the whistle technology according to the present invention. The CDMA technology can assign an orthogonal pseudo-random code to each user.

(Spread Spectrum Based Audio Frequency Communication System)

FIG. 1shows a block diagram of the spread spectrum based audio frequency communication system1according to the present invention.

The spread spectrum based audio frequency communication system1includes a transmitting apparatus10and a receiving apparatus20. However, some devices may have only one of the transmitting apparatus10and the receiving apparatus20, depending on their hardware support.

According to the first aspect of the present invention, the transmitting apparatus10includes at least one dot-product module11(three dot-product module are shown in this case), a summation module12, a transmitting modulation module13, a mixture module14, a digital-to-analog converter (DAC)15, and a transmitter16.

Each dot-product module11receives data given by a user and a pseudo-noise (PN) code, performs a dot-product of the data and the PN code, derives a dot-product result as a spreading data (seeFIG. 2), and sends the spreading data to the summation module12.

Three dot-product modules11are illustratively shown inFIG. 1. In the case ofFIG. 1, the top dot-product module11performs a dot-product of a user U1's data and a PN code C1, the middle dot-product module11performs a dot-product of a user U2's data and a PN code C2, and the bottom dot-product module11performs a dot-product of a user U3's data and a PN code C3. The PN codes may be chosen to be orthogonal to each other, that is, for any two of the PN codes, their inner product is zero.

FIG. 2shows an example of a spreading data derived by a dot-product of data given by a user and a PN sequence (i.e. a PN code).

As shown inFIG. 2, a first spreading data section S1is the same as a first PN code section when performing a dot-product with a data bit “logic 1”. A second spreading data section S2is the inverse of a second PN code section when performing a dot-product with a data bit “logic 0”. A third spreading data section S3is the same as a third PN code section when performing a dot-product with a data bit “logic 1”.

It should be noted that “logic 0” in this specification is defined such that the dot-product of a sequence and “logic 0” is the inverse of the sequence rather than a “ground” (zero-amplitude) signal. In some other articles, “logic 0” may be represented as “logic −1”.

Referred back toFIG. 1, the summation module12sums up the spreading data from the least one dot-product module11to form a summed data. The summed data is then sent to the transmitting modulation module13.

The transmitting modulation module13varies a carrier signal with the summed data to form a modulated signal.

The mixture module14receives the modulated signal and an acoustic signal, and mixes them up to form a mixed signal. The acoustic signal may carry (or generally be associated with) voice, such as a speech, or audio, such as a music, or the combination of them, in digital form.

The DAC15converts the mixed signal into acoustic waves.

Finally, the acoustic waves are sent by the transmitter16. The transmitter16may be a speaker, for example.

It is appreciated that, the acoustic waves can be regarded as having two components: the data component and the voice/audio component. The data component is obtained from a pseudo-randomization process, so it appears as a background noise of the voice/audio component, and people are expected not to be aware of the data component.

It is also noted that the term “acoustic waves” and the term “acoustic signal” have different meanings.

FIG. 3illustratively shows three spectrum diagrams, wherein power may be measured in unit of Watt, and frequency may be measured in unit of Hz. The spectrum diagram (a) shows an original spectrum P1of the user U1's data and its spreading data Q1. The spectrum diagram (b) shows three original spectrums P1, P2, P3of the users U1, U2, U3's data and their spreading data Q1, Q2, Q3, respectively. The spectrum diagram (c) shows the spreading data Q1appearing as the background noise in environment.

Accordingly, the transmitting apparatus10can communicate with the receiving apparatus20by transferring data signals in audio band.

On the other hand, the receiving apparatus20is preferably paired with the transmitting apparatus10. According to the second aspect of the present invention, the receiving apparatus20includes a receiver21, an analog-to-digital converter (ADC)22, a receiving modulation module23, and at least one dot-product module24(three dot-product module are shown in this case). The receiving apparatus20may further include an interference cancellation module25, a delay module26, and a mixture module27.

The acoustic waves are received by the receiver21. The receiver21may be a microphone, for example.

The ADC22converts the acoustic waves into the mixed signal. The mixed signal is then sent via two paths.

In one path, the receiving modulation module23recovers the summed data from the mixed signal with the carrier signal. In some cases, the receiving modulation module23may also be regarded as a demodulator.

Each dot-product module24receives the summed data and the PN code, performs a dot-product of the summed data and the PN code, and derives the original data given by the user at the transmitting apparatus10. The dot-product module24may be the same as the dot-product module11.

Three dot-product modules24are illustratively shown inFIG. 1. In the case ofFIG. 1, the top dot-product module24performs a dot-product of the summed data and the PN code C1to derive the user U1's data, the middle dot-product module24performs a dot-product of the summed data and the PN code C2to derive the user U2's data, and the bottom dot-product module24performs a dot-product of the summed data and the PN code C3to derive the user U3's data. Accordingly, the receiving apparatus20successfully derives all the data sent from the transmitting apparatus10. As previously mentioned, in some cases, the PN codes may be chosen to be orthogonal to each other.

Herein, the received user data is said to be the same as the transmitted user data in term of digital (e.g. binary) form, but one may be a multiple of another in term of analog form.

There may be the voice/audio component to be recovered from the acoustic waves. Therefore, the mixed signal is also sent via another path associated with the cancellation module25, the delay module26, and the mixture module27.

The cancellation module25generates an interference signal from the user data.

The delay module26may be a first in first out (FIFO) buffer. The delay module26receives and delays the mixed signal to form a delayed signal so that the delayed signal can be synchronized with the interference signal for calculation in the mixture module27.

The mixture module27receives the delayed signal and the interference signal, and subtract (or remove) the interference signal from the delayed signal to derive the acoustic signal, which may be the (speech) voice, the (music) audio, or the combination of them. InFIG. 1, the plus symbol (+) near the mixture module27means that the interference signal turns into positive value, and the minus symbol (−) near the mixture module27means that the delayed signal turns into a negative value.

Finally, the two components: the data component and the voice/audio component in the acoustic waves are both received and recovered by the receiving apparatus20. Therefore, the spread spectrum based audio frequency communication system1according to the present invention allows data transmission and/or reception along with sound (i.e. in audio band).

It is to be understood that the aforementioned modules of the present invention can be carried out in any desired and suitable manner. For example, they can be implemented in hardware or software. Unless otherwise indicated, the various functional elements, stages and means of the present invention may include a suitable processor, a controller, a functional unit, a circuitry, a processing logic, a microprocessor arrangement, and so on, that are operable to perform the functions. There may be a dedicated hardware element and/or programmable hardware element that can be configured to operate in desired and suitable manners.

FIG. 4shows two examples of beamforming technology incorporated into the spread spectrum based audio frequency communication system1according to the present invention.FIG. 4only shows the transmitters16and the receivers21to respectively represent the transmitting apparatus10and the receiving apparatus20of the spread spectrum based audio frequency communication system1for illustrative purpose.

The transmitter16may be provided with beamforming capability to generate directional beam pattern. For example, as shown in example (a) ofFIG. 4, a transmitter array including two adjacent transmitters16is assigned to transmit acoustic waves to two distanced receivers21. In this case, the beamforming is preferably applied to acoustic waves so that the acoustic waves transmitted from the receiver array can be separated into two directional waves respectively toward the two distanced receivers21.

The receiver21may be provided with beamforming capability for signal quality improvement, interference cancellation, and/or transmitter direction estimation. For example, as shown in example (b) ofFIG. 4, two distanced transmitters16respectively transmit two acoustic waves to a receiver array including two adjacent receivers21. In this case, the beamforming is preferably applied to the two acoustic waves received from the two distanced transmitters16so that one of them can be clearly distinguish from the other of them.

In some embodiments, space-time coding may be applied to the acoustic waves for signal-to-noise ratio (SNR) enhancement

FIG. 5shows design factors for beamforming and a polar diagram of the acoustic waves, wherein the radial distance from the center represents field strength of the acoustic waves.

A main lobe, a back lobe, and a plurality of side lobes are shown inFIG. 5. The main lobe is a lobe in a preferred direction, and it is designed to have highest field strength by giving it with a larger Q×H value, wherein Q represents a receiver array vector and H represents a beamforming coefficients vector. The side lobes are lobes in non-preferred directions, the back lobe is a specific side lobe in an opposite direction from the main lobe, and they are designed to have lower field strength by giving them with smaller Q×H value.

Typical microphone array is used to track one acoustic source.

However, in the present invention, the receiver array can be designed in a linear or circular arrangement. The receivers21in the array are divided into a plurality of virtual groups. Each receiver21can have different functions, such as beamforming, noise estimation and reduction, direction of arrival (DoA) estimation, and/or range estimation.

In addition, the receivers21in one group may not be physically adjacent to each other. In other words, they are grouped in term of their functions rather than their locations, so the grouping is called “virtual grouping”.

Each virtual group divided from the receiver array may be regarded as a beamformer that traces beam (e.g. directional acoustic waves) from a desired direction. A multi-beamformer for tracing different desired directions may be realized with a plurality of virtual groups. The direction referred herein may be directions within a small range rather than one direction along one line.

FIG. 6shows two examples of virtual grouping of the receiver array for the spread spectrum based audio frequency communication system1according to the present invention.

Example (a) ofFIG. 6shows a receiver array6in a linear arrangement, the receiver array6is divided into two groups611and612, the first group611is used to receive beam from a direction D1, and the second group612is used to receive beam from another direction D2.

Example (b) ofFIG. 6shows a receiver array6in a linear arrangement, the receiver array6is divided into three groups: a first group including receivers211represented by white color is used to receive beam from a direction D1, a second group including receivers212represented by black color is used to receive beam from another direction D2, a third group including receivers213represented by dot pattern is used for noise estimation and reduction, and thus the receivers213are preferably arranged in edges of the receiver array.

With the virtual grouping according to the present invention, receivers in the same group can be widely distributed in space and support each other to avoid dead zone.

FIG. 7shows several examples of multiple input multiple output (MIMO) technology incorporated into the spread spectrum based audio frequency communication system1according to the present invention.FIG. 7only shows the transmitters16and the receivers21to respectively represent the transmitting apparatus10and the receiving apparatus20of the spread spectrum based audio frequency communication system1for illustrative purpose.

In these cases, the transmitters16may be speakers, and they may form a speaker array; the receivers may be microphones, and they may form a microphone array, so as to enable the MIMO capability between the transmitting apparatus10and the receiving apparatus20.

With the MIMO technology according to the present invention, the transmitter array can transmit one whistle command to simultaneously control multiple receiving apparatuses20. In other hand, the receiver array can simultaneously receive multiple whistle commands from multiple receiving apparatuses20, and operate according to those whistle commands.

It is appreciated that, the “whistle technology” can be combined with any or all of the “beamforming”, the “virtual grouping”, and the “MIMO technology” depending on practical application.

An ad-hoc network is a decentralized type of wireless network. It does not rely on a pre-existing infrastructure. Instead, each node participates in routing by forwarding data for other nodes.

FIG. 8shows a schematic diagram of the whistle ad-hoc network8according to the present invention.

The whistle ad-hoc network8includes a plurality of whistle-enabled devices, such as a computer81, a speaker82, a smartphone83, a tablet84, a smart television85, and a home entertainment86. Other Internet of thing (IoT) devices may also participate in the ac-hoc network8. Each whistle-enabled device is equipped with the spread spectrum based audio frequency communication system1(as shown inFIG. 1).

The whistle ad-hoc network according to the present invention provides a low cost solution for IoT applications because it is not necessary to construct an intranet by a wired or wireless router. Each whistle-enabled device in the whistle ad-hoc network can work as a router for (data) packet forwarding. The whistle ad-hoc network can be easily expanded or contracted. It is easy to add or remove any device in the whistle ad-hoc network.

In addition, the whistle technology according to the present invention allows transferring data in audio band. Any device having an acoustic transmitter (e.g. speaker) and an acoustic receiver (e.g. microphone) can participate in the whistle ad-hoc network without dedicated RF modules (e.g. antenna) adapted for electromagnetic waves.

With the whistle ad-hoc network according to the present invention, various sensors from various devices can be associated, and it enables sensor fusion for data exchanging and management in different scenarios. For example, in a scenario for “home”, kitchen equipment or bathroom equipment may transmit temperature data or moisture data to a computer easily by their speakers. In a scenario for “traffic”, a vehicle may send measured traffic data to a traffic center easily by its horn.

Echolocation, sonic-vision, proximity or near-field communication, remote whistle command, time synchronization protocol for time synchronization among devices, and other applications may be applicable with the whistle technology according to the present invention.

FIG. 9shows a proximity communication between two whistle-enabled devices91and92.

(Audio Band Signaling for Distance Detection)

The spread spectrum based audio frequency communication system1(as shown inFIG. 1) according to the present invention may use regular (i.e. conventional) speaker and microphone as the transmitter16and the receiver21. They operate in an acoustic frequency band of 0 Hz to 20 KHz. The regular speaker and microphone are readily available and cost effective.

The same speaker-microphone pair can be used for normal audio/voice applications and distance detection simultaneously, which means, the speaker can send data without stopping audio/voice, and the microphone can receive the data along with the audio/voice.

According to the third aspect of the present invention, there is provided an audio band signaling system3, which may be used in distance detection. The audio band signaling system is an alternative form of the spread spectrum based audio frequency communication system1(as shown inFIG. 1).

FIG. 10shows a block diagram of the audio band signaling system3according to the present invention.

The audio band signaling system3includes a transmitting apparatus30and a receiving apparatus40.

The transmitting apparatus30includes a spreading module31, a mixture module33, and a transmitter (e.g. regular speaker)34. The transmitting apparatus30may optionally include an extra-processing module32, which may be a bypass module or a domain transform module. The domain transform module may perform inverse fast Fourier transform (IFFT) module, for example.

In the spreading module31, a signal S(t) used for distance detection is modulated by a high-bandwidth pseudo random binary sequence (PRBS) to increase the processing gain. For example, S(t) bandwidth may be 10 Hz, and PRBS bandwidth may be 16 KHz. The spreading module31then outputs a spread signal.

The spread signal may optionally pass through the extra-processing module32for additional signal processing. The extra-processing module32outputs an extra-processed signal. However, in some embodiments, the extra-processing module32may be omitted.

The spread signal is noise-like because of the modulation by the PRBS, and so is the extra-processed signal.

The mixture module33receives the spread signal (or the extra-processed signal) and an acoustic signal, which may be voice and/or audio waves, and mixes them up to form a mixed acoustic waves.

In this embodiment, the mixed acoustic waves are directly sent by the transmitter34, so that it does not require a DAC.

On the other hand, the receiving apparatus40includes a receiver (e.g. regular microphone)41, a de-spreading module43, and a detection module44. The receiving apparatus40may optionally include another extra-processing module32, which may be a bypass module or a domain transform module. The domain transform module may perform fast Fourier transform (FFT) module, for example. In some embodiment, the transform in the transmitting apparatus30and the transform in the receiving apparatus40may form a pair, one for encoding and another for decoding.

The mixed acoustic waves are received by the receiver41, and may optionally pass through the other extra-processing module42for additional signal processing. The other extra-processing module42may convert the extra-processed signal into the spread signal. However, in some embodiments, the other extra-processing module42may be omitted.

The spread signal is then de-spread (or generally, demodulated) by the de-spread module43with the same PRBS, and returns to the signal S(t), as in the transmitting apparatus30.

The detection module44detects and analyzes the signal S(t). The signal S(t) may include identity information, time information, or other properties helpful to distance detection. The distance between two objects can be calculated by the time between transmission and reception. The two objects may be two common objects, one whistle-enabled device and one common object, or two whistle-enabled devices.

FIG. 11shows two examples of audio band distance detection according to the present invention. Each whistle-enabled device inFIG. 11includes the audio band signaling system3according to the present invention.

Example (a) ofFIG. 11shows a whistle-enabled device W1transmits mixed acoustic waves, and receives the reflection thereof from a common object. By confirming the time between transmitting the mixed acoustic waves and receiving the reflection thereof, the distance from the whistle-enabled device W1to the object can be calculated by a CPU or processor of the whistle-enabled device W1.

In some cases, the whistle-enabled device W1may transmit different mixed acoustic waves to detect different objects at the same time. In these cases, in order to identify respective reflections from respective mixed acoustic waves, identity information or time information may be carried in the respective mixed acoustic waves. (As previously mentioned, space-time coding is possible.) The whistle technology according to the present invention, which allows data transmission and/or reception along audio band, is therefore important. In the prior art, different distance detection with different acoustic waves is not possible because the acoustic waves cannot be distinguished since they are pure acoustic waves without carrying data for identification. However, the present invention conquers the aforementioned problem.

It is also appreciated that electromagnetic waves cannot be used in distance detection because they travel at the speed of light, which is too fast in measurement on the earth.

Example (b) ofFIG. 11shows a whistle-enabled device W2transmits mixed acoustic waves to another whistle-enabled device W3. Time information may be carried in the mixed acoustic waves, so that the other whistle-enabled device W3can acknowledge the transmitting time, and derive the distance from itself to the whistle-enabled device W2. Then, the other whistle-enabled device W3can make a response to the whistle-enabled device W2to inform it about space-time information. In this case, it is not necessary to detect a wave reflection.

In conclusion, the present invention provides a spread spectrum based audio frequency communication system and an audio band signaling system using the “whistle technology”, which allows transferring data signals in audio band. Various intrinsic properties of acoustic waves may be combined with the data signals carried therein, thereby realizing various useful applications. Most of devices already have speakers and/or microphones adapted to the whistle technology according to the present invention, and thus do not require RF modules for wireless communication. A cost effective wireless communication can therefore be achieved.