WO2019033191A1 - Improved method for the transmission of data between devices over sound waves - Google Patents

Abstract

The present invention relates to a method specially developed for direct application to transmission using mobile devices with computing potential (for example, smartphone, tablet), over sound waves, permitting the transmission of data between devices without the need for additional hardware and/or any other type of connectivity. In its broadest concept, the method according to the present invention comprises the use of rapid pulses of disperse frequency, using a broader frequency spectrum for a single pulse, intermittent sound (pulses) and over a broad frequency spectrum (CSS - chirp spread spectrum), and a more rapidly and more easily detectable pulse amplitude. Amongst countless other applications, the method is suitable for use in a system for payment using a mobile device, information sharing, electronic locks.

Description

 "PERFORMED METHOD FOR DATA COMMUNICATION BETWEEN DEVICES THROUGH SOUND WAVES"

Field of the Invention

The present invention relates to a method especially developed for direct application in communication on mobile devices with computational potential (eg smartphone, tablet) through sound waves, allowing the communication of data between two devices without the need for additional hardware and / or any other type of connectivity.

History of the Invention

[002] The concept of using sound waves as a form of communication between devices has already been proposed previously. Several prior patent documents address this issue.

EP 1906696 A1, entitled "Information providing system", describes a model wherein a computer which broadcasts data through sounds emitted by the speaker thereof using NRZ (Non Return to Zero) modulation at frequencies preferably between 12 Khz and 13 Khz. A cellular device picks up the sound emitted and demodulates. Although this document describes in some detail the modulation / demodulation scheme, it ignores that airwaves are subjected to a large amount of noise interference from other sound sources in the environment and, above all, from the interference caused by the signal emitted and reflected by environmental surfaces. This makes it impossible to achieve the specified transmission speeds and makes the effectiveness of the disclosed method questionable. WO 2005055566 A1, entitled "Sonic data communication between mobile phones", describes a generic method for communication between cellular phones through sound, using audio frequencies between 8 Khz and 22 Khz. The description of the method used for modulation / demodulation is quite generic, covering practically all the methods listed in the technical literature and without going into technical details about which method has the most benefits. Although reference is made to the sound communication in the document title, it devotes only a few lines to identify the modulation / demodulation methods to be used, describing all the main methods of digital signal processing (DSP). By simply listing the possible types of modulation, this document ignores the specifics of the medium to be used, namely air. It does not identify any feature that would make any of the methods better or worse, considering the aspects of the medium used. Thus, the effectiveness of the communication becomes questionable without deepening on key issues, such as reflections of the signal being transmitted on nearby surfaces (multipath propagagatiori).

[005] In addition to these documents, others also address the issue. For example, WO 2003096593 A2, entitled "Wireless communication using sound", which uses QPSK (Quadratude Phase Shift Keying) modulation, also does not address aspects addressed by the present invention, which makes its effectiveness questionable.

WO 2013166567 A8, entitled "Method for communicating data between devices via sound waves", of the same depositor, uses BPSK (Binary phase-shift keying) modulation. Although this method is more efficient than the others proposed, it still does not present specific solutions for some key problems highlighted in the scope of this patent. Generally, all such patent references generally describe methods for communicating between mobile devices in a more or less generic fashion. However, when observing the practical issues in this type of communication, it becomes evident a series that issues that are not resolved and solved by said documents.

As is well known, air is a medium of low density and with a velocity of sound propagation significantly lower than other means in which most of the traditionally used modulation / demodulation methods have been devised and developed, such as by example, the electromagnetic field.

[009] Sound waves, unlike electromagnetic waves, are mostly reflected when encountering solid barriers. This makes the existence of reflections of surfaces in the path to be traversed by the transmitted signal should be considered (multipath propagation).

[0010] Current mobile devices (for example, smartphones) as well as computers, desktops or notebooks, have a wide variation in the positioning of their speakers and microphones. In this way, it can be considered that, even at reduced distances, it is likely that the path between the signal emitted by the loudspeaker of one device to the microphone of a second device is not direct, and that in most cases it is subject to interference of the multipath propagation itself.

The use of high sound frequencies, in the order of 8KHz - 22KHz, is recommended because frequencies are less subject to interference from ambient noise, while providing greater bandwidth for data transmission. However, because they have a (<0.136 milliseconds), high frequencies are very susceptible to the constructive / destructive effect of the overlap of the original signal with its reflections. A small distance, for example about 4 cm, may, depending on the configuration of the surrounding surfaces, totally cancel or make stronger the signal picked up by the microphone. In addition, since the devices are not expected to be perfectly stopped during transmission, this constructive / destructive effect can vary greatly in intensity with small changes or changes of angle between the apparatus and the surrounding surfaces during transmission.

It is quite common and expected that there are reflective surfaces close to communicating devices such as tables, walls and, above all, the flat surfaces themselves of the devices, making this problem relevant in effectiveness to the efficiency of communication.

The various modulation methods presented by the state of the art are generally quite affected by the above-described phenomenon, making efficiency and even effectiveness significantly impaired.

Furthermore, the quality of the loudspeakers and microphones of the mobile devices and computers currently on the market is quite heterogeneous. While some devices can efficiently reproduce and pick up frequencies up to 22 Khz, others find it difficult to reproduce as well as pick up in different ranges of the spectrum used in audio playback, that is, up to 22 Khz / 24 Khz. This condition, on the one hand, makes the use of frequencies above the human auditory spectrum (above 20 Khz) unsatisfactory, since only a small set of devices will be able to communicate efficiently. In turn, the use of high frequencies within the audible spectrum may, depending on the modulation chosen, create unpleasant high sounds to the point of disturbing the hearing human.

The set of issues and problems enumerated above is largely responsible for the low effectiveness of the data transmission solutions via sound waves, motivating their little adoption until the present moment.

OBJECTIVES OF THE INVENTION

It is thus an object of the present invention to provide an improved method for communicating data between devices via sound waves which will definitely solve the above-mentioned problems of the prior art.

Another object of the present invention is to provide an improved method for communicating data between devices via sound waves, which can be applied in the vast majority of the devices and varieties of speakers and microphones currently available on the market.

Brief Description of the Figures

The method for communicating data between devices via sound waves in accordance with the present invention may be well understood with the aid of the accompanying figures, which are not to be considered as limiting the scope of the present invention, since of a merely exemplifying, represent:

 Figure 1 shows a general scheme of data transmission between two devices according to the method of the present invention;

Figure 2 illustrates how near surfaces and the devices themselves generate reflections that interfere with the reception of the audio signal transmitted;

 Figures 3A and 3B show a sample FSK (transmitted shift keying) signal and a sample of the captured signal with multipath propagation (B) interference;

 Figures 4A and 4B illustrate a sample PSK (transmitted phase shift keying) signal and a sample of the captured signal with multipath propagation (B) interference;

 Figures 5A and 5B illustrate as a method using OOK (0/7 off keying) audio pulses (A) and a sample of the captured signal with multipath propagation (B) interference;

 - Figure 6A and 6B - Illustrate the spacing between the pulses emitted. The original signal (A) is a sample of the captured signal with interference type multipath propagation (B);

 Figure 7 illustrates the variable spacing used by the second coding method that identifies the bit groupings by the time distance between each pulse;

 Figure 8A and 8B illustrate the variable spacing used by the second coding method that identifies the bit groupings by the time distance between each pulse. The original signal (A) and the signal after the BPF filter (B);

 Figure 9 shows the conceptual block diagram of the method of demodulation of captured sound waves in data.

Detailed Description of the Invention

As schematically illustrated in Figure 1, the general method of data transmission between two devices in accordance with the present invention comprises (i) encoding the digital data into digital sound signal, (ii) sending this digital signal to (iii) the propagation of sound in the air, (iv) the capture of sound through the microphone of the receiving device, (v) the transformation into digital sound data, and (vi) the decoding of the digital sound data for retrieval of the original data as issued.

Due to the large amount of potential interference generated by nearby surfaces and the involved apparatus itself, methods such as FSK (frequency shift keying) and PSK (phase shift keying) are greatly affected by the constructive / destructive effect of interference. The OOK (On Off keying) method, although presenting some performance improvement, is also affected, making it difficult to differentiate between an "on" signal and an eventual reflection of the previously transmitted signal.

Thus, in particular, the improved method for communicating data between devices via sound waves according to the present invention uses fast scattered frequency pulses. This specificity of the method according to the present invention is justified by the following non-exhaustive reasons:

 - uses a wider range of frequencies for a single pulse, between 8 Khz and 20 Khz, and can be easily reproduced and captured by the wide range of speakers and microphones currently on the market. Eventually the frequency limits of the pulses can be changed in their minimum or maximum limit to suit or take advantage of the specific conditions of their implementation;

 - uses intermittent sound (pulses) and a wide frequency bandwidth (CSS), eliminating the need to use high power in the reproduction of higher frequencies in narrow bands. This aspect makes the final sound emitted more pleasing to the human ear;

- Pulse amplitude is faster and easily detectable, making digital signal processors (DSPs) unnecessary more complex and computationally more expensive to the CPU of the devices; - because the pulses are very fast (<0.26 milliseconds), the pulse start can be detected before the interference of its reflections in the captured signal. Depending on the implementation this pulse size can be increased or reduced.

According to the present invention, pulse data encoding can be done in a number of ways, wherein the first form of modulation may be OOK (On Off keying), in which the presence of a pulse indicates a "1" bit ", while the absence of a pulse indicates a" 0 "bit. Figure 5A shows an example graphic of original sound.

Further, according to the present invention, it is of extreme importance that account is taken of possible signal reflections. A close reflection can generate a false bit "1" that is no more than an echo of a previous pulse. Figures 5A and 5B show graphs illustrating and emission of the original sound and its capture with interference.

[0024] A time window should be established where possible interference is ignored. In order to calculate the size of the time window, the maximum tolerable distance must be defined so that the signal can be skipped without sufficient signal attenuation so that it can be ignored.

[0025] Defined distances and duration may vary according to desired specifications. In an example of implementing the method according to the present invention described here, we will consider a maximum distance of 25 cm, that is, 50 cm total for the sound path. Taking the velocity of sound as 34,029 cm / s, the time for the sound to travel 50 cm would be approximately 1.47 ms. We'll call this time of buffer window (B). It adds up to that pulse length time (P) of about 0.45 ms and the F frame (or time window) reserved for each bit would be at 1.92 ms, enabling a baud rate of 520 bps. Figures 6A and 6B illustrate an example data coded with OOK (On Off keying) modulation using the F spacing for the original sound emission and that captured with interference.

A second most efficient form of modulation utilizes DPPM (2-bit Differential Pulse-Position Modulatiorí), combined with the window buffer (B) used in the first method described above. The first pulse indicates the beginning of the information, the second pulse indicates the beginning of a new bit pair. What defines the value of the bit pair is the distance between the pulses. The distance should follow the basics of the previous method, using window buffer B and pulse length P. As in the table below:

Table 1

Figure 7 shows a graph with data encoded by this modulation method. Signal demodulation is done in a similar way. The first pulse identified marks the beginning of the signal. The other pulses identify the data transmitted from the distance of time between the current pulse and the previous pulse. This method is more efficient when B> P ^* (2N-1), where N is equal to the number of bits grouped by frame. In the exemplified embodiment N = 2, however, depending on the desired limits in the transmission, a higher value may be used. A transmission using this second method, with N = 2, B = 1, 54 ms and P = 0.45 ms, will take an average time of (B + 4 ^* P) / 2 = 1.63 ms, reaching a approximately 614 bps, or about 18% higher than the first method.

In addition, by ensuring that only one pulse will be used for each grouping, then only one pulse will be used as a reference. Thus, the method becomes less sensitive to any preemptive noises that may generate false pulses in the audio pickup.

The coding process of the present invention is carried out by the following steps:

 a) encoding the initial signal in a manner similar to a NRZI (Non-return-to-zero inverted) signal where each transition from value "V" to "-V" marks the creation of the pulses used by the methods described above. To verify the correction of the transmitted message, a double-byte (CRC {cyclic redundancy check) is added to the original message;

 b) passing the signal in a BPF (Band Pass Filter) filter so that the modulation is restricted to the selected bandwidth, generating fast signal pulses;

 c) sending the encoded digital audio to the sound reproduction hardware on the transmitting device.

Figures 8A and 8B respectively illustrate the graphics with the sound originally emitted and that filtered and modulated according to step b) above the method according to the present invention. The decoding process is described in the block diagram of Figure 9, and comprises the following steps:

 d) capture of the signal encoded by the microphone and scanning by the audio capture hardware;

 e) passing the signal through a BPF (Band Pass Filter) filter to restrict the range of frequencies to be analyzed;

 f) passing the signal through an AGC (Automatic Gain Control!), which normalizes the input signal;

 g) passing the signal through a Peak Detector (PDET) that identifies the presence of pulses;

 h) retrieving the encoded data by analyzing the detected pulses (Data Recovering) after data encoding; and

 i) verification of the message with the CRC (Cyclic redundancy check) generated by it.

In more detail, the method according to the present invention comprising:

 a) a coding step consisting of:

 - encoding the initial signal similarly to an NRZI signal where each transition from value "V" to "-V" marks the creation of the pulses,

- Use a Frame (F) size corresponding to the Buffer Window (B) added to the Pulse length (P), where each for each Frame (F) inserts and inverts the signal if the data bit has a value of 1;

 - passing said signal on a BPF (Band Pass Filter) filter so that the modulation is restricted to the selected bandwidth generating fast signal pulses; and

 - sending said coded digital audio to the sound reproduction hardware in the device for transmission;

b) a decoding step consisting of: - capture the signal encoded by the microphone and scan through the audio capture hardware;

 - passing the signal through a BPF {Band Pass Filter) filter to restrict the frequency range to be analyzed;

 - pass the signal through an AGC (Automatic Gain Control), which normalizes the input signal;

 - pass the signal through a Peak Detector (PDET) that identifies the presence of pulses;

 retrieve the encoded data by analyzing the detected pulses (Data Recovering) after data encoding;

 - recovering bits 0 or 1 from pulse detection at each time F in the analyzed signal; and

 - check the message with the CRC (Cyclic Redundancy Check) generated by it.

[0034] Alternatively and in detail, the method according to the present invention comprises:

 a) a coding step consisting of:

 - encoding the initial signal similarly to an NRZI signal where each transition from value "V" to "-V" marks the creation of the pulses,

- establish a Frame (F) corresponding to the Buffer Window (B) added to the Pulse (P) length multiplied by the value of each transmitted bit pair ("V") plus 1;

 - making each calculated Frame (F) a signal inversion;

 - passing said signal on a BPF (Band Pass Filter) filter so that the modulation is restricted to the selected bandwidth generating fast signal pulses; and

- sending said coded digital audio to the sound reproduction hardware in the device for transmission; b) a decoding step consisting of:

 - capture the signal encoded by the microphone and scan through the audio capture hardware;

 - passing the signal through a BPF {Band Pass Filter) filter to restrict the frequency range to be analyzed;

 - pass the signal through an AGC (Automatic Gain Control), which normalizes the input signal;

 - pass the signal through a Peak Detector (PDET) that identifies the presence of pulses;

 retrieve the encoded data by analyzing the detected pulses (Data Recovering) after data encoding;

 - analyze the distance of time between the current pulse and the previous one and recover the corresponding bits; and

 - check the message with the CRC (Cyclic redundancy check) generated by it.

Application Examples

It will be appreciated by those skilled in the art that due to the improvements introduced, the improved method for communicating data between devices through sound waves according to the present invention may have numerous practical applications nowadays and others which may occur in the future. Among the current applications, we highlight some which, by way of example only and not limitative of the invention, represent mere embodiments, which may be varied in various ways without departing from the inventive scope described above.

One of the preferred applications of the present invention is its use in payment systems for mobile devices, thus enabling the large amount of mobile devices (smartphones, tablets and the like) present in the market can act as point of sale (POS) and payment devices using a simple mechanics of collection and payment. By means of the data transmission method between two devices according to the present invention it becomes possible to create a fairly simple mechanical payment system. The paying device transmits, via sound, the payment code relating to its purchase. This code may contain information about the purchase ticket. The vending device (POS) receives the code sent and makes the online conferencing of the authenticity of the same. Once authentication is complete, the sale can be completed.

One of the most direct features of the present invention is the pairing of devices, in order to enable two physically close devices to share data in a simple and intuitive way. By means of data transmission between two devices according to the present invention it is possible to easily pair two devices A and B, if device A and device B use the same application (or the functionality is already inserted in the operating system of the device itself ) and are physically close. With an application-specific matching protocol, A and B can recognize and establish a link for information exchange. From this point on, both sender and receiver will already be identified for receiving and sending data.

Electronic locks Another simple and straightforward application of the present invention is for the opening of locks. That is, to enable the opening of locks with the use of mobile devices. Through the method of data transmission between two devices according to the present invention, an LF device may be connected to a door and lock release mechanism. The said DF device connected to the lock will be constantly listening to the ambient sound and will have a database of disposable "keys" (data sequences). A DL opening device will also have a database of "keys" for playback. When one of the "key sounds" is reproduced, the DF lock device will acknowledge its validity and open the door. The "key sound" used automatically becomes invalid after opening and will be discarded from both databases.

Γ00391 Personal information exchange: An example of an additional application is the exchange of personal contact information, for example, business cards. By means of the data transmission method between two devices according to the present invention it is possible to simply transmit, without the need of any other type of connectivity, personal data such as name, company, address, telephone, email, etc. . It is sufficient that both people have a mobile device with the information exchange application according to the present invention and bring their devices closer together. The personal information of each will be sound transmitted and duly registered in an internal database of each device for future use.

Claims

Claims 1 . A PERFECTED METHOD FOR DATA COMMUNICATION BETWEEN DEVICES THROUGH SOUND WAVES, characterized by the use of fast pulses of scattered frequency and thus:  - use a wider range of frequencies for a single pulse;  - use intermittent sound (pulses) and a wide frequency band (CSS); and  - use amplitude of the pulses more quickly and easily detectable. A method according to claim 1, characterized in that the frequency band for a single pulse is in the range of 8 Khz to 20 Khz. A method according to claim 1 or 2, characterized in that said pulse is of the order of <0.26 milliseconds. A method according to claim 1, characterized in that it comprises: a) a coding step consisting of:  - encoding the initial signal similarly to an NRZI signal where each transition from value "V" to "-V" marks the creation of the pulses,  - Use a Frame (F) size corresponding to the Buffer Window (B) added to the Pulse length (P), where each for each Frame (F) inserts and inverts the signal if the data bit has a value of 1;  - passing said signal on a BPF (Band Pass Filter) filter so that the modulation is restricted to the selected bandwidth generating fast signal pulses; and  - sending said coded digital audio to the sound reproduction hardware in the device for transmission; b) a decoding step consisting of: - capture the signal encoded by the microphone and scan through the audio capture hardware;  - passing the signal through a BPF (Band Pass Fiitef) filter to restrict the frequency range to be analyzed;  - pass the signal through an AGC (Automatic Gain Control!), which normalizes the input signal;  - pass the signal through a Peak Detector (PDET) that identifies the presence of pulses;  retrieve the encoded data by analyzing the detected pulses (Data Recovering) after data encoding;  - recovering bits 0 or 1 from pulse detection at each time F in the analyzed signal; and  - check the message with the CRC (Cyclic Redundancy Check) generated by it. A method according to claim 1, characterized in that it comprises: a) a coding step consisting of:  - encoding the initial signal similarly to an NRZI signal where each transition from value "V" to "-V" marks the creation of the pulses,  - establish a Frame (F) corresponding to the Buffer Window (B) added to the Pulse (P) length multiplied by the value of each transmitted bit pair ("V") plus 1;  - making each calculated Frame (F) a signal inversion;  - passing said signal on a BPF (Band Pass Filter) filter so that the modulation is restricted to the selected bandwidth generating fast signal pulses; and  - sending said coded digital audio to the sound reproduction hardware in the device for transmission; b) a decoding step consisting of: - capture the signal encoded by the microphone and scan through the audio capture hardware;  - passing the signal through a BPF {Band Pass Filter) filter to restrict the frequency range to be analyzed;  - pass the signal through an AGC (Automatic Gain Control!), which normalizes the input signal;  - pass the signal through a Peak Detector (PDET) that identifies the presence of pulses;  retrieve the encoded data by analyzing the detected pulses (Data Recovering) after data encoding;  - analyze the distance of time between the current pulse and the previous one and recover the corresponding bits; and  - check the message with the CRC (Cyclic redundancy check) generated by it. A method according to claim 4 or 5, characterized in that in step a) a double cyclic redundancy check (CRC) is added to the original message for verifying the correction of the transmitted message. A method according to claim 4 or 5, characterized in that it is applied in a mobile payment system, information sharing, electronic locks, among other applications.