RU2474062C2 - System and method for in-band modem for data transmission over digital wireless communication networks - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: system is provided for transmitting information through a speech codec (in-band) such as found in a wireless communication network. A modulator transforms the data into a spectrally noise-like signal based on the mapping of a shaped pulse to predetermined positions within a modulation frame, and the signal is efficiently encoded by a speech codec. A synchronisation sequence provides modulation frame timing in the receiver and is detected based on analysis of a correlation peak pattern. A request/response protocol provides reliable transfer of data using message redundancy, retransmission and/or robust modulation modes depending on communication channel conditions.

EFFECT: high noise-immunity.

16 cl, 41 dwg

Description

PRIORITY REQUEST

[0001] Priority claims for the following US provisional claims are claimed: No. 61/059179, "ROBUST SIGNAL FOR DATA TRANSMISSION OVER IN-BAND VOICE MODEM IN DIGITAL CELLULAR SYSTEMS", filed June 5, 2008, and transferred to its assignee, and therefore expressly included in the present description by reference; and No. 61/087923 "SYSTEM AND METHOD OF AN IN-BAND MODEM FOR DATA COMMUNICATIONS OVER DIGITAL WIRELESS (OR CELLULAR) COMMUNICATION NETWORKS", filed August 11, 2008, and transmitted to its assignee, and thereby expressly incorporated into this description by link; and No. 61/093657 "SYSTEM AND METHOD OF AN IN-BAND MODEM FOR DATA COMMUNICATIONS OVER DIGITAL WIRELESS (OR CELLULAR) COMMUNICATION NETWORKS", filed September 2, 2008, and transmitted to its assignee, and thereby expressly incorporated into this description by link; and No. 61/122997 "SYSTEM AND METHOD OF AN IN-BAND MODEM FOR DATA COMMUNICATIONS OVER DIGITAL WIRELESS (OR CELLULAR) COMMUNICATION NETWORKS", filed December 16, 2008, and transmitted to its assignee, and thereby expressly incorporated into this description by link; No. 61/151457 "SYSTEM AND METHOD FOR PROVIDING GENERAL BIDIRECTIONAL IN-BAND MODEM FUNCTIONALITY", filed February 10, 2009, and transmitted to its assignee, and thereby expressly incorporated into this description by reference; and No. 61/166904 "SYSTEM AND METHOD OF AN IN-BAND MODEM FOR DATA COMMUNICATIONS OVER DIGITAL WIRELESS (OR CELLULAR) COMMUNICATION NETWORKS", filed April 6, 2009, submitted to its assignee and hereby expressly incorporated into this description by reference.

RELATED APPLICATIONS

[0002] Related simultaneously pending US patent applications are:

"SYSTEM AND METHOD OF AN IN-BAND MODEM FOR DATA COMMUNICATIONS OVER DIGITAL WIRELESS COMMUNICATION NETWORKS", having the number in the register of the attorney 081226U1, simultaneously filed with this application, submitted to its assignee and explicitly included in the present description by reference; "SYSTEM AND METHOD OF AN IN-BAND MODEM FOR DATA COMMUNICATIONS OVER DIGITAL WIRELESS COMMUNICATION NETWORKS", having the number in the register of the attorney 081226U2, simultaneously filed with this application, transferred to its assignee and explicitly included in the present description by reference; "SYSTEM AND METHOD OF AN IN-BAND MODEM FOR DATA COMMUNICATIONS OVER DIGITAL WIRELESS COMMUNICATION NETWORKS", having the number in the register of the attorney 081226U3, simultaneously filed with this application, transferred to its assignee and explicitly included in the present description by reference; "SYSTEM AND METHOD OF AN IN-BAND MODEM FOR DATA COMMUNICATIONS OVER DIGITAL WIRELESS COMMUNICATION NETWORKS", having the number in the register of the attorney 081226U4, simultaneously filed with this application, transferred to its assignee and explicitly included in the present description by reference; "SYSTEM AND METHOD OF AN IN-BAND MODEM FOR DATA COMMUNICATIONS OVER DIGITAL WIRELESS COMMUNICATION NETWORKS", having the number in the register of the attorney 081226U5, simultaneously filed with this application, transferred to its assignee and explicitly included in the present description by reference.

FIELD OF THE INVENTION

[0003] The present description generally relates to data transmission over a voice communication channel. More specifically, the disclosure relates to the transmission of non-speech information through a speech codec (in-band) in a communication network.

Description of the level of technology

[0004] Voice transmission has been fundamental in data transmission systems since the advent of the landline telephone line and wireless radio. Advances in the research and design of data transmission systems have led the industry towards digital systems. One advantage of a digital data transmission system is its ability to reduce the required transmission bandwidth by implementing compression on the data to be transmitted. As a result, many research and development activities have entered compression methods, especially in the field of speech coding. The standard speech compression device is a “vocoder”, and it is also interchangeably called a “speech codec” or “speech encoder”. A vocoder receives digitalized speech samples and generates collections of data bits known as “speech packets”. Several standardized speech coding algorithms exist in support of various digital data transmission systems that require voice transmission, and in fact speech support is a minimal and essential requirement in most modern data transmission systems. The 3rd Generation Partnership Project 2 (3GPP2) is an exemplary standardization organization that defines IS-95, 1xRTT (1x Radio Transmission Technology) data transmission systems CDMA2000, EV-DO (evolutionary optimized data transmission) CDMA2000 and EV-DV (evolutionary optimized data transmission / votes) CDMA2000. The third-generation partnership project is another exemplary standardization organization that defines GSM (Global System for Mobile Communications), UMTS (Universal System for Mobile Communications), HSDPA (High Speed Downlink Packet Technology), HSUPA (High Speed Uplink Packet Technology), HSPA + (High Speed Packet Development) and LTE (Long Term Development) project. VoIP (Voice over Internet Protocol) is an example protocol used in data transmission systems defined in 3GPP and 3GPP2, as well as in others. Examples of vocoders used in such data transmission systems and protocols include G.729 ITU-T (International Telecommunication Union), AMR (Adaptive Multi-Speech Voice Codec) and EVRC (Options 3, 68, 70 of the Advanced Variable Rate Voice Codec Service data transmission).

[0005] Shared information is the main goal of modern data transmission systems in support of the demand for instant and ubiquitous connectivity. Users of modern data transmission systems transmit speech, video, text messages and other data to stay in touch. Newly developed applications tend to outpace network development and may require upgrading system modulation schemes and data transfer protocols. In some remote geographical areas, only voice services may be available due to a lack of infrastructure support for advanced data services in the system. Alternatively, users may choose to allow only voice services on their data device for economic reasons. In some countries, support for publicly available services is delegated by mandate on a communications network, such as 911 emergency mode (E911) or vehicle emergency request (eCall). In these emergency examples, fast data transfer is a priority, but it is not always realistic, especially when advanced data services are not available in the user terminal. The previous methods provided solutions for transmitting data through a speech codec, but these solutions are able to support only transfers with a low data rate due to the coding inefficiency that occurs when trying to encode a non-speech signal using a vocoder.

[0006] The speech compression algorithms implemented by most vocoders use “synthesis analysis” methods to model the human voice path with parameter sets. Parameter sets typically include digital filter coefficient functions, gain and stored signals, known as cryptographic books, and more. The search for the parameters that most closely match the characteristics of the input speech signal is performed in the vocoder encoder. The parameters are then used in the vocoder decoder to synthesize an estimate of the input speech. The parameter sets available for the vocoder to encode signals are tuned for the best sample speech, characterized by voice periodic segments, as well as non-voice segments that have noise-like characteristics. Messages that do not contain periodic or noise-like characteristics are essentially not encoded by the vocoder and in some cases can lead to serious distortion in the decoded output signal. Examples of signals that do not show speech characteristics include fast-changing single-frequency “tone” signals or dual-tone multi-frequency “DTMF” signals. Most vocoders are not able to efficiently encode such signals.

[0007] Data transmission by means of a speech codec is commonly referred to as “in-band” data transmission, where data is included in one or more voice packets output from the speech codec. Several methods use audio tones at predetermined frequencies in the speech frequency range to represent data. Using predefined frequency tones to transmit data through speech codecs, especially with a higher data rate, is unreliable due to the vocoders used in these systems. Vocoders are designed for exemplary speech signals using a limited number of parameters. Limited parameters are insufficient to effectively model tone signals. The ability of vocoders to simulate these tones is further impaired when trying to increase the data rate by rapidly changing tones. This affects the accuracy of detection and leads to the need to add complex circuits in order to minimize data errors, which, in turn, further reduces the overall data rate of the data transmission system. Therefore, there is a need to effectively and efficiently transmit data through a speech codec in a communication network.

[0008] Accordingly, it would be advantageous to provide an improved system for transmitting and receiving information through a speech codec in a communication network.

SUMMARY OF THE INVENTION

[0009] The embodiments disclosed herein solve the aforementioned needs by using an in-band modem to reliably transmit and receive non-speech information through a speech codec.

[0010] In one embodiment, the method of sending non-speech information through a speech codec comprises processing a plurality of input data symbols to produce a plurality of first pulse signals, generating a plurality of first pulse signals to produce a plurality of generated first pulse signals, and encoding a plurality of generated first pulse signals by speech codec.

[0011] In another embodiment, the device comprises a processor configured to process a plurality of input data symbols to produce a plurality of first pulse signals, a shaper configured to generate a plurality of first pulse signals to produce a plurality of generated pulse signals, and a speech codec configured to encode a plurality of generated first pulse signals to produce a speech packet.

[0012] In another embodiment, the device comprises means for processing a plurality of input data symbols to produce a plurality of first pulse signals, means for generating a plurality of first pulse signals to produce a plurality of generated first pulse signals, and means for encoding the generated first pulse signals by speech codec.

[0013] In another embodiment, a method for synchronizing non-speech frames by means of a speech codec comprises generating a predetermined sequence that has noise-like characteristics and is robust against speech frame errors, and sending this predetermined sequence through the speech codec.

[0014] In another embodiment, the device comprises a generator configured to generate a predetermined sequence that has noise-like characteristics and is error tolerant of a speech frame, and a speech codec configured to process this predetermined sequence to produce a speech packet.

[0015] In another embodiment, the device comprises means for generating a predetermined sequence that has noise-like characteristics and is error tolerant of the speech frame, and means for sending this predetermined sequence through the speech codec.

[0016] In another embodiment, a method for obtaining non-speech data embedded in a vocoder packet comprises the steps of receiving and decoding a vocoder packet, filtering the decoded vocoder packet until a synchronization signal is detected, calculating a clock offset based on the synchronization signal, and extracting non-speech data embedded in a decoded vocoder package based on a clock offset.

[0017] In another embodiment, the device comprises a receiver configured to receive and decode a vocoder packet, a filter configured to filter the decoded vocoder packet until a synchronization signal is detected, a calculation unit configured to calculate a clock offset based on the synchronization signal and an extraction unit configured to extract non-speech data embedded in the decoded vocoder package based on the clock offset.

[0018] In another embodiment, the apparatus comprises means for receiving and decoding a vocoder packet, means for filtering a decoded vocoder packet until a synchronization signal is detected, means for calculating a clock offset based on the synchronization signal, and means for extracting non-speech data embedded in a decoded vocoder package based on a clock offset.

[0019] In another embodiment, a method for controlling transmissions of a source terminal from a destination terminal in an in-band data system comprises transmitting an initial signal from a destination terminal, interrupting transmission of an initial signal after detecting a first received signal, transmitting a NACK signal from a destination terminal, interrupting transmission of a NACK signal after detecting a successfully received data message of the source terminal, transmitting the ACK signal from the destination terminal, and interrupting the transmission of the ACK signal after ak predetermined amount of ACK signals have been transmitted.

[0020] In another embodiment, the device comprises a processor, a memory in electronic communication with the processor, instructions stored in the memory, while these instructions are capable of performing the steps of transmitting the initial signal from the destination terminal, interrupting the transmission of the initial signal after detecting the first received signal, transmitting the NACK signal from the destination terminal, interrupting the transmission of the NACK signal after detecting a successfully received data message of the source terminal, transmitting the ACK signal from the destination terminal, and interrupting Receiving an ACK signal after a predetermined number of ACK signals have been transmitted.

[0021] In another embodiment, a device for controlling transmissions of a source terminal from a destination terminal in an in-band data system includes means for transmitting an initial signal from a destination terminal, means for interrupting the transmission of an initial signal after detecting a first received signal, means for transmitting a NACK signal from a terminal destination, means for interrupting the transmission of the NACK signal after detecting a successfully received data message of the source terminal, means for transmitting the signal and the ACK from the destination terminal and means for interrupting the transmission of the ACK signal after a predetermined number of ACK signals

has been transferred.

[0022] In another embodiment, a method for controlling transmissions of a source terminal from a source terminal in an in-band data system comprises detecting a request signal in a source terminal, transmitting a synchronization signal from a source terminal after detecting a request signal, transmitting a user data segment from the source terminal using the first circuit modulation, and interrupting the transmission of a user data segment after detecting the first received signal.

[0023] In another embodiment, the device comprises a processor, a memory in electronic communication with the processor, instructions stored in the memory, these instructions being able to perform the steps of detecting the request signal in the source terminal, transmitting the synchronization signal from the source terminal after detecting the request signal, transmitting the user data segment from the source terminal using the first modulation scheme; and interrupting the transmission of the user data segment after detecting the first received signal.

[0024] In another embodiment, a device for controlling transmissions of a source terminal from a source terminal in an in-band data system includes means for detecting a request signal in a source terminal, means for transmitting a synchronization signal from a source terminal after detecting a request signal, means for transmitting a user data segment from the source terminal using the first modulation scheme, and means for interrupting the transmission of the user data segment after detecting the first clear signal.

[0025] In another embodiment, a method for controlling bidirectional data transmissions from a destination terminal in an in-band data system comprises transmitting a send signal from a destination terminal, interrupting transmission of a send signal after detecting a first received signal, transmitting a synchronization signal from a destination terminal, transmitting a user data segment from the destination terminal using the first modulation scheme, and interrupting the transmission of the user data segment after detecting the second Answered signal.

[0026] In another embodiment, the device comprises a processor, a memory in electronic communication with the processor, instructions stored in the memory, these instructions being capable of performing the steps of transmitting a sent signal from a destination terminal, interrupting transmission of a sent signal after detecting a first received signal, transmitting the synchronization signal from the destination terminal, transmitting the user data segment from the destination terminal using the first modulation scheme, and stopping the transmission of the user data segment After detecting the second received signal.

[0027] In another embodiment, a device for controlling bidirectional data transmissions from a destination terminal in an in-band data system includes means for transmitting a send signal from a destination terminal, means for interrupting the transmission of a send signal after detecting a first received signal, means for transmitting a synchronization signal from a terminal destination, means for transmitting a user data segment from the destination terminal using the first modulation scheme, and means for interrupting the transmission of the user data segment after detecting the second received signal.

[0028] In another embodiment, a system for transmitting data in an in-band data system from a vehicle containing a system integrated in a vehicle (IVS, PTS) for a public safety point (PSAP) comprises one or more sensors, located in IVS, to provide IVS sensor data, IVS transmitter located in IVS, for transmitting IVS sensor data, PSAP receiver located in PSAP, for receiving IVS sensor data, PSAP transmitter located in PSAP, for transmitting PSAP command data, receiver Ivs located in IVS for receiving PSAP command data; wherein the IVS transmitter contains an IVS message formatting unit for formatting the IVS sensor data and receiving the IVS message, an IVS processor for processing the IVS message and receiving a plurality of generated IVS pulse signals, an IVS speech encoder for encoding the generated IVS pulse signals and receiving the encoded IVS signal, a synchronization generator IVS for generating an IVS synchronization signal; and an IVS transmission controller for transmitting a sequence of IVS synchronization signals and IVS messages; wherein the PSAP receiver comprises a PSAP detector for detecting the IVS synchronization signal and obtaining a PSAP synchronization flag, a PSAP demodulator for demodulating the IVS message and receiving the received IVS message; wherein the PSAP transmitter comprises a PSAP message formatting unit for formatting the PSAP command data and receiving the PSAP command message, a PSAP processor for processing the PSAP command message and receiving the plurality of generated PSAP pulse signals, a PSAP speech encoder for encoding the generated PSAP pulse signals and obtaining the encoded PSAP signal, a PSAP synchronization generator for generating a PSAP synchronization signal, and a PSAP transmission controller for transmitting a sequence of PSAP synchronization signals and PSAP command messages; wherein the IVS receiver comprises an IVS detector for detecting a PSAP synchronization signal and acquiring an IVS synchronization flag and an IVS demodulator for demodulating the PSAP message and receiving the received PSAP message.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Aspects and related advantages of the embodiments described herein will become more apparent by reference to the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0030] FIG. 1 is a diagram of an embodiment of a source terminal and a destination terminal that use an in-band modem to transmit data through a speech codec in a wireless communication network.

[0031] FIG. 2 is a diagram of an embodiment of a transmission data modem used in an in-band data system.

[0032] FIG. 3A is a diagram of an embodiment of a clock signal generator.

[0033] FIG. 3B is a diagram of another embodiment of a clock signal generator.

[0034] FIG. 3C is a diagram of yet another embodiment of a clock signal generator.

[0035] Figure 4 is a diagram of an embodiment of a burst pulse generator.

[0036] FIG. 5 is a diagram of an embodiment of a sequence of bursts of synchronization pulses.

[0037] FIG. 6A is a diagram of an embodiment of a sequence of synchronization preambles.

[0038] FIG. 6B is a diagram of an embodiment of a sequence of synchronization preamble with non-overlapping reference sequences.

[0039] FIG. 7A is a graph of a correlation output signal of a synchronization preamble, wherein the preamble comprises non-overlapping reference sequences.

[0040] FIG. 7B is a graph of a correlation output signal of a synchronization preamble, wherein the preamble comprises non-overlapping reference sequences.

[0041] FIG. 8A is a diagram of an embodiment of a synchronization message format.

[0042] FIG. 8B is a diagram of another embodiment of a synchronization message format.

[0043] FIG. 8C is a diagram of yet another embodiment of a synchronization message format.

[0044] FIG. 9 is a diagram of an embodiment of a transmission data message format.

[0045] FIG. 10 is a diagram of an embodiment of a composite synchronization and data transmission message format.

[0046] FIG. 11A is a graph of a power spectral density of a signal based on an in-band pulse versus frequency.

[0047] FIG. 11B is a graph of a power spectral density of a signal based on an in-band tone versus frequency.

[0048] FIG. 12 is a diagram of an embodiment of a data modulator using sparse pulses.

[0049] FIG. 13 is a diagram of an embodiment of a representation of a sparse pulse data symbol.

[0050] FIG. 14A is a diagram of an embodiment of arranging a generated pulse in a modulation frame using a cyclic transition method.

[0051] FIG. 14B is a diagram of an embodiment of arranging a generated pulse in a modulation frame for a typical example in the art.

[0052] FIG. 15A is a diagram of an embodiment of a clock signal detector and a receiver controller.

[0053] FIG. 15B is a diagram of another embodiment of a synchronization signal detector and a receiver controller.

[0054] FIG. 16 is a diagram of an embodiment of a burst pulse detector.

[0055] FIG. 17A is a diagram of an embodiment of a synchronization preamble detector.

[0056] FIG. 17B is a diagram of another embodiment of a synchronization preamble detector.

[0057] FIG. 18A is a diagram of an embodiment of a synchronization detector controller.

[0058] FIG. 18B is a diagram of another embodiment of a synchronization detector controller.

[0059] FIG. 19 is a diagram of an embodiment of a reception timing control unit.

[0060] FIG. 20 is a diagram of an embodiment of a reception data modem used in in-band data systems.

[0061] FIG. 21 is a diagram of an embodiment of an emergency call system located inside a vehicle.

[0062] FIG. 22 is a diagram of an embodiment of an interaction of a data request sequence transmitted on a downlink to a data destination terminal and a data response sequence transmitted on an uplink to a source data terminal with interaction initiated by a receiving terminal.

[0063] FIG. 23A is a diagram of an embodiment of an interaction of a data request sequence transmitted on a downlink to a data destination terminal and a data response sequence transmitted on an uplink to a source data terminal with an interaction initiated by the source terminal.

[0064] FIG. 23B is a diagram of another embodiment of an interaction of a data request sequence transmitted on a downlink to a data destination terminal and a data response sequence transmitted on an uplink to a source data terminal with an interaction initiated by the source terminal.

[0065] FIG. 24A is a diagram of an embodiment of a bi-directional response request sequence of response data and a response sequence of data transmitted both in a downlink and an uplink.

[0066] FIG. 24B is a diagram of another embodiment of an interaction of a bidirectional data request sequence and a data response sequence transmitted both in a downlink and an uplink.

[0067] FIG. 25 is a diagram of an embodiment of a user data packet format, wherein the user data length is less than the transmission packet size.

[0068] FIG. 26 is a diagram of an embodiment of a user data packet format, wherein the length of the user data is larger than the size of the transmission packet.

[0069] FIG. 27A is a diagram of an embodiment of an interaction of a transmission data request sequence and a transmission data response sequence, wherein the user data length is larger than the transmission packet size.

[0070] FIG. 27B is a diagram of another embodiment of an interaction of a transmission data request sequence and a transmission data response sequence, wherein the user data length is greater than the transmission packet size.

[0071] FIG. 27C is a diagram of another embodiment of an interaction of a transmission data request sequence and a transmission data response sequence, wherein the user data length is larger than the transmission packet size.

[0072] FIG. 27D is a diagram of another embodiment of an interaction of a transmission data request sequence and a transmission data response sequence, wherein the user data length is larger than the transmission packet size.

DETAILED DESCRIPTION

[0073] FIG. 1 shows an embodiment of an in-band data system that can be implemented in a wireless source terminal 100. The source terminal 100 communicates with a receiving terminal 600 via data channels 501 and 502, a network 500, and a data channel 503. Examples of suitable wireless communication systems include cellular telephone systems operating in accordance with the Global System for Mobile Communications (GSM) standards, the third generation universal partnership project mobile phone system (UMTS 3GPP), and the third generation 2 code partnership access code division multiple access ( CDMA 3GPP2), synchronous time and code division multiple access (TD-SCDMA) and global microwave access compatibility (WiMAX). One skilled in the art will recognize that the methods described herein can equally apply to an in-band data system that does not include a wireless channel. Communication network 500 includes any combination of routing and / or switching equipment, communication lines, and other infrastructure suitable for establishing a communication link between source terminal 100 and destination terminal 600. For example, data link 503 may not be a wireless communication line. Typically, the source terminal 100 functions as a voice device.

TRANSMITTER

[0074] Typically, a transmission baseband path 200 routes a user's speech through a vocoder, but it is also able to route non-speech data through a vocoder in response to a request from a source terminal or communication network. Routing non-speech data through a vocoder is advantageous because it eliminates the need for the source terminal to request and transmit data over a dedicated data channel. Non-speech data is formatted into messages. Message data that is still in digital form is converted into a noise-like signal containing the generated pulses. The message data information is embedded at the position of the pulses of a noise-like signal. A noise-like signal is encoded by a vocoder. The vocoder is not configured differently depending on whether the input signal is user speech or non-speech data, so it is advantageous to convert the message data into a signal that can be effectively encoded by the set of transmission parameters assigned to the vocoder. A coded noise-like signal is transmitted within the band via a communications link. Since the transmitted information is embedded in the pulse positions of a noise-like signal, reliable detection depends on the restoration of the clock timing of the pulses relative to the frame boundaries of the speech codec. To help the receiver detect in-band transmission, a predetermined synchronization signal is generated and encoded by the vocoder before transmitting the message data. The sequence of the synchronization protocol, control and messages is transmitted to ensure reliable detection and demodulation of non-speech data in the receiver.

[0075] Referring to a transmission baseband path 200, an input audio signal S210 is input to a microphone and an input audio signal processor 215, and transmitted through a multiplexer 220 to a vocoder encoder 270, wherein compressed speech packets are generated. A suitable audio input signal processor typically includes a circuit to convert the input signal to a digital signal, and a signal conditioning unit to generate a digital signal, such as a low-pass filter. Examples of suitable vocoders include examples described by the following reference samples: GSM-FR, GSM-HR, GSM-EFR, EVRC, EVRC-B, SMV, QCELP13K, IS-54, AMR, G.723.1, G.728, G.729, G.729.1, G.729a, G.718, G.722.1, AMR-WB, EVRC-WB, VMR-WB. A vocoder encoder 270 delivers voice packets to a transmitter 295 and an antenna 296, and voice packets are transmitted over a data channel 501.

[0076] A data transfer request may be initiated by the source terminal or via a communication network. The data transfer request S215 prohibits the voice path through the multiplexer 220 and enables the transmission data path. The input data S200 is pre-processed by the data message formatting unit 210 and output as a transmission message S220 to the data transmission modem 230 Tx. The input data S200 may include user interface (UI) information, user position / location information, time stamps, equipment sensor information, or other suitable data. An example of a suitable data message formatting unit 210 includes a circuit for calculating and summing control bits using a cyclic redundancy check (CRC) to the input data, providing retransmission buffer memory, implement error control coding, such as a hybrid automatic request for retransmission of data (HARQ), and interleave the input. A data transmission modem 230 Tx converts the transmission message S220 Tx into signal transmission data S230 Tx, which are routed through a multiplexer 220 to a vocoder encoder 270. Once the data transfer is completed, the voice path can be re-enabled through the multiplexer 220.

[0077] FIG. 2 is a suitable exemplary block diagram of a data transmission Tx modem 230 shown in FIG. 1. Three signals can be time-multiplexed through a multiplexer 259 into a transmit data signal S230 Tx; synchronization output signal S245, jamming output signal suppression S240, and transmission Tx modulation output signal S235. It should be understood that various orders and combinations of the synchronization output signal S245, jamming output signal S240, and signal transmission modulation signal S235 S235 can be output as transmission data S230 Tx. For example, the synchronization output signal S245 may be sent to each data segment of the transmission Tx modulation output signal S235. Or, the synchronization output signal S245 may be sent once until the output of the transmission Tx modulation signal S235 is completed with the jamming output signal S240 sent between each data segment of the transmission Tx modulation output signal S235.

[0078] The synchronization output signal S245 is a synchronization signal used to establish timing in the reception terminal. The synchronization signals are required to set the clock for the transmitted in-band data, since the data information is embedded in the pulse positions of the noise-like signal. FIG. 3A shows a suitable exemplary block diagram of the clock generator 240 shown in FIG. Three signals can be time-multiplexed through a multiplexer 247 to a synchronization output signal S245; pulse train S241 synchronization, the output signal S236 activation and the output signal S242 of the preamble synchronization. It should be understood that various orders and combinations of the burst of synchronization pulses S241, the activation output signal S236 and the synchronization preamble output signal S242 can be output as the synchronization output signal S245. For example, FIG. 3B shows a synchronization generator 240 consisting of a (circuit) activation output signal S236 and a (circuit) output signal S242 of a synchronization preamble, wherein an activation signal S236 can be sent before each output signal S242 of a synchronization preamble. Alternatively, FIG. 3C shows a synchronization generator 240 consisting of a (circuit) burst of pulses S241 of a synchronization and (circuit) of an output signal S242 of a synchronization preamble, wherein a burst of pulses S241 of a synchronization can be sent before each output signal S242 of a synchronization preamble.

[0079] Referring to FIG. 3A, a sync pulse train S241 is used to establish coarse clocking at the receiver, and it contains at least one sinusoidal frequency signal having a predetermined sampling frequency, sequence, and duration, and is generated by a sync pulse train circuit 250, shown in figure 4. Sinusoidal Frequency 1,251 represents binary data +1, and Frequency 2,225 represents binary data -1. Examples of suitable signals include constant frequency sinusoids in the speech band, such as 395 Hz, 540 Hz and 512 Hz for one sinusoidal signal and 558 Hz, 1035 Hz and 724 Hz for another sinusoidal signal. The synchronization pulse train sequence circuit 253 determines which frequency signal is multiplexed through the multiplexer 254. The information sequence modulated into the synchronization pulse train should be a sequence with good autocorrelation properties. An example of a suitable burst of synchronization pulses 253 is a Barker code with a length of 7, shown in Fig.5. For each symbol “+”, the Sine Wave of Frequency 1 is output as a burst of pulses S241 synchronization, and for each symbol “-” the Sine Wave of Frequency 2 is output.

[0080] Referring to FIG. 3A, the output of the synchronization preamble S242 is used to establish an accurate (sample-based) clock in the receiver, and it contains a predetermined data pattern known in the receiver. A suitable example of a predetermined data pattern of the synchronization preamble output signal S242 is the synchronization preamble sequence 241 shown in FIG. 6A. A composite preamble sequence 245 is generated by concatenating several periods of a pseudo-random noise (PN) sequence 242 with an overlapping and summed result of a PN sequence 242 and an inverted version of the PN sequence 244. The symbols “+” in the composite sequence 245 of the preamble represent binary data +1, and the symbols “-” represent binary data -1. Another suitable example inserts zero-value samples between the data bits of a PN sequence. This provides a temporal (in time) distance between the data bits in order to take into account the effects of the “blurring” effects caused by the characteristics of the band-pass filter of the channel, which seeks to spread the energy of the data bits over more than a few bit time intervals.

[0081] The previously described construction of a synchronization preamble using associated PN sequence periods with overlapping segments of inverted versions of the PN sequence provides advantages in reduced transmission time, improved correlation properties, and improved detection characteristics. These advantages lead to a preamble that is robust against speech frame errors.

[0082] By overlapping PN segments, the resulting composite synchronization preamble contains fewer bits in the sequence than the non-overlapping version, thereby reducing the total time required to transmit the composite preamble sequence 245.

[0083] To illustrate the improvement in the correlation properties of the overlapping synchronization preamble, FIGS. 7A and FIG. 7B show a comparison between the correlation of the PN sequence 242 with the non-overlapping composite preamble sequence 245b shown in FIG. 6B and the correlation of the PN sequence 242 with the overlapping composite preamble sequence 245 synchronization shown in figa. Fig. 7A shows the main correlation peaks, both positive and negative, as well as the secondary correlation peaks located between the main peaks for the non-overlapping composite synchronization preamble sequence 245b. Negative peaks 1010 result from the correlation of the PN sequence 242 with the first inverted segment of the non-overlapping composite preamble sequence 245b. The positive correlation peaks 1011, 1012, 1013 result from the correlation of the PN sequence 242 with three concatenated segments of the PN sequence 242, which make up the middle section of the non-overlapping composite preamble sequence 245b. Negative peaks 1014 result from the correlation of the PN sequence 242 with the second inverted segment of the non-overlapping composite preamble sequence 245b. 7A, the minor correlation peak 1015 corresponding to an offset of 3 samples from the first positive correlation peak 1011 shows a value of approximately 5 (1/3 of the magnitude of the main peaks). Fig. 7B shows several major correlation peaks, both positive and negative, as well as secondary correlation peaks between the main peaks for the overlapping composite sequence 245 of the synchronization preamble. 7B, a minor correlation peak 1016 corresponding to an offset of 3 PN samples from the first positive correlation peak 1011 shows a value of approximately 3 (1/5 of the magnitude of the main peaks). A smaller value of the minor correlation peak 1016 for the overlapping preamble shown in FIG. 7B leads to less false detection of major correlation peaks of the preamble than compared to the non-overlapping minor peak 1015 shown in FIG. 7A.

[0084] As shown in FIG. 7B, five main peaks are generated by correlating the PN sequence 242 with the composite sequence of the synchronization preamble 245. The pattern shown (1 negative peak, 3 positive peaks and 1 negative peak) allows you to determine the frame timing based on any 3 detected peaks and the corresponding time distances between the peaks. The combination of 3 detected peaks with the corresponding time distance is always unique. A similar description of the correlation peak pattern is shown in Table 1, where correlation peaks are referenced by “-” for a negative peak and “+” for a positive peak. The way to use the unique correlation peak pattern is advantageous for in-band systems, since the unique pattern compensates for possible loss of speech frame, for example, due to poor channel conditions. Loss of speech frame can also lead to a loss of the correlation peak. By having a unique pattern of correlation peaks separated by predetermined time distances, the receiver can reliably detect a synchronization preamble even with lost speech frames that result in lost correlation peaks. A few examples are shown in Table 2 for combinations of 3 detected peaks in the pattern (2 peaks lost in each example). Each entry in Table 2 represents a unique pattern of peaks and temporal distances between peaks. Example 1 in Table 2 shows the detected peaks 3, 4, and 5 (peaks 1 and 2 were lost) leading to a “+ + -” pattern with one predetermined distance between each peak. Examples 2 and 3 in Table 2 also show the “+ + -” pattern, however the distances are different. Example 2 has two predetermined distances between the detected peaks 2 and 4, while Example 3 has two predetermined distances between the detected peaks 3 and 5. Thus, Examples 1, 2 and 3 represent a unique pattern from which can be obtained frame timing. It should be understood that the detected peaks may overlap the boundaries of the frame, but that unique patterns and predetermined distances are still applied.

Table 1 Correlation Peak Number one 2 3 four 5 Correlation Peak Polarity - + + + -

table 2 Correlation Peak Number one 2 3 four 5 Detected correlation peaks Example 1 + + - Example 2 + + - Example 3 + + - Example 4 + + + Example 5 - + - Example 6 - + - Example 7 - + + Example 8 - + - Example 9 - + + Example 10 - + +

[0085] One skilled in the art will recognize that a different preamble sequence can be used resulting in a different correlation peak pattern than those shown in FIG. 7B and Table 1. It will also be apparent to one skilled in the art that multiple patterns correlation peaks can be used to identify various operating modes or to transmit bits of information. An example of an additional correlation peak pattern is shown in Table 3. The correlation peak pattern shown in Table 3 supports a unique pattern from which frame timing can be obtained, as described previously. Having multiple correlation peak patterns is beneficial for identifying various transmitter configurations at the receiver, such as message formats or modulation schemes.

Table 3 Correlation Peak Number one 2 3 four 5 Correlation Peak Polarity + - - - +

[0086] Referring again to FIG. 3A, an activation output signal S236 is used to initiate a vocoder encoder 270 to exit sleep mode, low data rate transmission mode, or intermittent transmission mode. The activation output S236 can also be used to prevent the vocoder encoder 270 from entering sleep mode, low transmission mode, or intermittent transmission. The activation output signal S236 is generated by the activation generator 256. Activation signals are advantageous when transmitting in-band data through vocoders that implement sleep function, discontinuous transmission (DTX), or operate at a lower data rate during inactive voice segments to minimize the launch delay that may occur when switching from inactive speech state to the active state of speech. Activation signals can also be used to identify the characteristics of the transmission mode, for example, the type of modulation scheme used. The first example of a suitable activation output signal S236 is a single constant frequency sinusoidal signal in the voice band, such as 395 Hz. In this first example, an activation signal prevents the vocoder encoder 270 from entering sleep mode, DTX, or low data rate mode. In this first example, the receiver ignores the transmitted signal of the activation output signal S236. A second example of a suitable activation output signal S236 is a signal containing multiple sinusoidal signals with each signal identifying a particular data modulation scheme, for example, 500 Hz for modulation scheme 1 and 800 Hz for modulation scheme 2. In this second example, the activation signal prevents the vocoder encoder 270 from entering sleep mode, DTX, or low data rate mode. In this second example, the receiver uses the transmitted activation output signal S236 to identify the data modulation scheme.

[0087] An example of a composite synchronization output signal S245 is a signal comprising a multiplexed sync pulse train S241 and a synchronization preamble output signal S242, as shown in FIG. 8A. Tsb 701 and Tsp 702 represent the duration in time during which each signal is transmitted. An example of a suitable range for Tsb is 120-140 milliseconds, and for Tsp is 40-200 milliseconds. Another example of a composite synchronization output signal S245 is a signal comprising a multiplexed activation output signal S236 and a synchronization preamble output signal S242, as shown in FIG. 8B. Twu 711 and Tsp 702 represent the length of time during which each signal is transmitted. An example of a suitable range for Twu is 10-60 milliseconds, and for Tsp is 40-200 milliseconds. Another example of a composite synchronization output signal S245 is a signal comprising a multiplexed activation output signal S236, a burst of synchronization pulses S241, and a synchronization preamble output signal S242, as shown in FIG. 8C. Twu 711, Tspl 721, Tsb 701, Tsp2 722 represent time durations during which each signal is transmitted. An example of a suitable range for Twu is 20-80 milliseconds, for Tsp1 is 40-200 milliseconds, Tsb is 120-140 milliseconds and Tsp2 is 40-200 milliseconds.

[0088] Referring to FIG. 2, a suitable example of a transmit Tx modulation output signal S235 is a signal generated by a modulator 235 using phase-modulation (PPM) with special waveforms of the modulation. This modulation method leads to low distortion when coding and decoding by various types of vocoders. Additionally, this method leads to good autocorrelation properties, and it can be easily detected by a receiver consistent with the waveform. Additionally, the generated pulses do not have a tonal structure; instead, the signals appear similar to noise in the frequency spectrum region and also retain a noise-like audible characteristic. An example of a power spectral density of a signal based on generated pulses is shown in FIG. 11A. As can be seen in FIG. 11A, the power spectral density displays a noise-like characteristic in the in-band frequency range (constant energy in the frequency range). On the contrary, the power spectral density of a signal with a tonal structure is shown in FIG. 11B, where the data is represented by tones with frequencies of approximately 400 Hz, 600 Hz and 1000 Hz. As can be seen in FIG. 11B, the power spectral density reflects “pulsed interference” of significant energy in the in-band frequency range in tone frequencies and in its harmonic.

[0089] FIG. 12 is an exemplary block diagram of a modulator 235 shown in FIG. 2. The sparse pulse generator 238 produces pulses corresponding to the input transmission message S220 Tx using phase-modulation, and then the pulse generator 239 generates pulses to create a signal for better coding quality in the vocoder encoder. A suitable example of a sparse pulse is shown in FIG. 13. The time axis is divided into modulation frames of duration T _MF . Within each modulation frame, a series of time instants t ₀ , t ₁ , ..., t _{m-1 are} defined relative to the border of the modulation frame, which identify the potential positions of the base pulse p (t). For example, pulse 237 at position t _{3 is} denoted by p (t - t ₃ ). The information bits of the transmission message S220 Tx input to the modulator 235 are mapped to symbols with corresponding conversion to pulse positions according to the mapping table. A pulse can also be formed with polarity conversion ± p (t). Therefore, the symbols can be represented by one of 2m distinct signals in the modulation frame, where m represents the number of times defined for the modulation frame, and the multiplication factor, 2, represents the positive and negative polarity.

[0090] An example of a suitable display of the position of the pulses is shown in Table 4. In this example, the modulator displays a 4-bit symbol for each modulation frame. Each symbol is represented in terms of the position k of the form p (nk) of the pulse and the sign of the pulse. In this example, T _MF is 4 milliseconds, resulting in 32 possible positions for a sampling frequency of 8 kHz. The pulses are separated by 4 points in time, leading to the appointment of 16 different positions of the pulse and combinations of polarity. In this example, the effective data frequency is 4 bits per character for a period of 4 milliseconds or 1000 bits / s.

Table 4 Symbol Pulse decimal binary 0 0000

one 0001

2 0010

3 0011

four 0100

5 0101

6 0110

7 0111

8 1000

9 1001

10 1010

eleven 1011

12 1100

13 1101

fourteen 1110

fifteen 1111

[0091] Another example of a suitable pulse position display is shown in Table 5. In this example, the modulator displays a 3-bit symbol for each modulation frame. Each symbol is represented in terms of the position k of the pulse shape p (nk) and the sign of the pulse. In this example, T _MF is 2 milliseconds, resulting in 16 possible positions for a sampling frequency of 8 kHz. The pulses are separated by 4 points in time, leading to the appointment of 8 different positions of the pulses and combinations of polarity. In this example, the effective data frequency is 3 bits for each character for a period of 2 milliseconds or 1500 bits / s.

Table 5 Symbol Pulse decimal binary 0 000

one 001

2 010

3 011

four one hundred

5 101

6 110

7 111

[0092] To increase stability in poor channel conditions, the modulator 235 can increase the duration of the modulation frame T _MF while maintaining a constant number of time instants t ₀ , t ₁ , ..., t _m-1 . This method is used to accommodate more time spacing between pulses, leading to more reliable detection. An example of a suitable pulse position display includes T _MF 4 milliseconds, resulting in 32 possible positions for a sampling frequency of 8 kHz. As a previous example, if the pulses are separated by 4 points in time, the display results in the assignment of 16 different pulse positions and polarity combinations. However, in this example, the separation between times is increased by a factor of 2 from the previous example, resulting in 8 different pulse positions and polarity combinations. In a suitable example, the modulator 235 may switch between different displays of the position of the pulse or the duration of the modulation frame depending on the feedback signal indicating channel conditions or transmission success. For example, a modulator 235 may start transmission using a T _{MF of} 2 milliseconds and then switch to a T _{MF of} 4 milliseconds if channel conditions are determined to be bad.

[0093] In order to increase stability with some vocoders, the modulator 235 may change the initial time offset in the display of the position of the pulses. An example of a suitable display of the position of the pulses is shown in Table 6. In this example, the modulator displays a 3-bit symbol for each modulation frame. Each symbol is represented in terms of the position k of the pulse shape p (nk) and the sign of the pulse. In this example, T _MF is 2 milliseconds, resulting in 16 possible positions for a sampling frequency of 8 kHz. The initial offset is set to 1 point in time, and the pulses are separated by 4 moments, leading to the appointment of 8 different positions of the pulse and combinations of polarity, as shown in the table.

Table 6 Symbol Pulse decimal binary 0 000

one 001

2 010

3 011

four one hundred

5 101

6 110

7 111

[0094] It should be understood that reducing the number of separation times will result in an increased number of bits for each symbol, and thus, higher data rates. For example, if T _MF is 4 milliseconds, the resulting number of possible positions for a sampling frequency of 8 kHz is 32 with polarity plus or minus for each, resulting in 64 different signals if no branch is turned on. To display 64 positions, the number of supported bits for each character is 6, and the resulting effective data rate is 1500 bits per second. It should also be understood that various combinations of T _MF and sample rates can be used to achieve the desired effective bit rate.

[0095] An example of a suitable pulse shaper 239 is a root cosine transform of a shape:

where β is the selectivity coefficient, 1 / T _S is the maximum symbol rate, and t is the sampling time.

For the previous example with 32 possible pulse positions (time instants), the following transformation generates the root cosine shape of the pulse, where the number of zeros to the first element of a non-zero pulse determines the exact position of the pulse in the frame.

It should be understood that the transform may be shortened or extended for various modulation frame size options.

[0096] FIG. 14A is an example of arranging a pulse in a modulation frame to generate a particular entry in the modulation alphabet. 14A, the pulse is represented by 13 samples, shown as P0-P12, where each sample represents the nonzero elements r (n) shown in the previous example. Figv is an example of a typical implementation in the art. 14B, the pulse is placed at offset 7 in the modulation frame T _MF (n) 1003, and the tail portion of the pulse continues in the next 4 sampling modulation frame T _MF (n + 1) 1004 (P9-P12). Samples from the modulation frame T _MF (n) 1003 extending to the next modulation frame T _MF (n + th) 1004, as shown in FIG. 14B, will result in intersymbol interference if pulse samples for the T _MF (n + 1) frame are placed to any of the first 4 samples of the frame T _MF (n + 1), since there will be overlapping samples. Alternatively, in the “loop transition” method shown in FIG. 14A, “tail” samples that extend to the next modulation frame T _MF (n + 1) 1004 are placed at the beginning of the current modulation frame T _MF (n) 1003. Samples (P9-P12) cycle through to the beginning of T _MF (n) in samples 0-3. Using the cyclic transition method to generate the modulation alphabet eliminates cases where samples of the generated pulse propagate to the next modulation frame. The cyclic transition method is advantageous because it leads to reduced intersymbol interference that will occur if samples of the generated pulse in an existing frame propagate to the next frame and overlap with samples of the generated pulse in the next frame. One skilled in the art will understand that a cyclic transition method can be used for any pulse position in a modulation frame, which will lead to samples propagating to the next modulation frame. For example, a pulse placed at offset 8 in the modulation frame T _MF (n) 1003 will be samples (P8-P12) with a cyclic transition.

[0097] Another example of a suitable pulse shaper 239 is a shape amplitude conversion signal:

An example of a signal for converting the amplitude of a sample 32 has the form:

[0098] Another example of a suitable pulse generator 239 is a linear prediction synthesizing filter. The response of an exemplary recursive synthesis filter LPC is determined by its impulse response:

and coefficients: a (i) = {- 6312, 5677, -2377, 1234, -2418, 3519, -2839, 1927, -629, 96} / 4096, i = 1, ..., 10. Filters with linear prediction is known in the art. The residual signal r (n) is first generated by the input symbols according to the pulse mapping tables discussed above. Then, the actual shape of the modulation pulse is obtained from filtering the modulated signal r (n) with h (n).

[0099] One skilled in the art will appreciate that the methods described herein can equally apply to various waveforms and pulse transformations. The wavelengths and modulations associated with these waveforms may also vary. In addition, waveforms can use fully uncorrelated (or orthogonal) waveforms to represent different symbols. In addition to the polarity of the generated pulse, the amplitude of the generated pulse can also be used to carry information.

[00100] Referring again to FIG. 2, the jamming output signal S240 is a signal used to separate the transmissions of the transmission message Tx, and it is generated by the jamming generator 255. An example of a suitable composite transmission data signal S230 Tx consisting of a multiplexed transmission output signal T23 modulation S235 and a jamming output signal S240 are shown in FIG. 9. Tmu1 731, Td1 732, Tmu2 733, Td2 734, Tmu3 735, Td3 736 and Tmu4 737 represent the time duration during which each signal is transmitted. An example of a suitable range for Tmu1, Tmu2, Tmu3 and Tmu4 is 10-60 milliseconds and for Td1, Td2 and Td3 it is 300-320 milliseconds for normal operation and 600-640 milliseconds for stable operation. Examples of a suitable jamming generator sequence may be a single-zero sequence signal or a sinusoidal frequency signal. Another suitable example of a signal used to separate the transmissions of a transmission Tx message is shown in FIG. 10. In this example, the activation output signal S236 and the synchronization preamble output signal S242 precede each transmission of the Tx modulation output signal S236. One skilled in the art will understand that various combinations of the output signal S242 of the synchronization preamble, the output jamming signal S240, the output signal T23 of the transmission modulation Tx can be equally applied. For example, the jamming output signal S240 may precede and follow the transmission signal Tx modulation output S235 in FIG. 10.

RECEIVER

[00101] Referring to FIG. 1, a reception baseband circuit 400 typically routes decoded voice packets from a vocoder to an audio signal processor, but it is also capable of routing decoded packets through a data demodulator. Since non-speech data has been converted into a noise-like signal and encoded by a vocoder at the transmitter, the receiver's vocoder is able to efficiently decode the data with minimal distortion. Decoded packets are continuously checked for in-band clock. If a synchronization signal is found, the frame clock is restored, and the decoded packet data is routed to the data demodulator. Decoded packet data is demodulated into messages. Messages are deformed and displayed. A protocol sequence containing synchronization, control, and messages ensures reliable detection and demodulation of non-speech data.

[00102] Voice packets are received on a data channel 502 at a receiver 495 and input to a vocoder decoder 390, wherein a decoded voice is generated and then routed through a demultiplexer 320 to an audio signal processor and a speaker 315 generating an audio output signal S310.

[00103] Once the synchronization signal is detected at the output S370 of the vocoder decoder through the synchronization detector 350, the signal S360 of the reception demultiplexer Rx control unit switches to the reception data path Rx in the reception demultiplexer 320 Rx. The vocoder packets are decoded by the vocoder decoder 390 and routed by the receive demultiplexer 320 Rx to a receive Rx clock unit 380 and then to a receive Rx data modem 330. The receive Rx data is demodulated by the receive Rx data modem 330 and sent to the data message formatting unit 301, whereby the output data S300 becomes available to the user or the equipment connected via the interface.

[00104] An example of a suitable data message formatting unit 301 includes a circuit for performing reverse interleaving of data of a reception message S320 Rx, implementing error control decoding such as hybrid automatic data retransmission request (HARQ), and for computing and checking control bits using cyclic redundancy code (CRC). Suitable S300 output may include user interface (UI) information, user position / location information, time stamps, equipment sensor information, or other suitable data.

[00105] FIG. 15A is a suitable exemplary block diagram of a synchronization detector and receiver controller 350 shown in FIG. The output signal S370 of the vocoder decoder is input to a sync pulse burst detector 360 and a sync preamble detector 351. The sync pulse burst detector 360 detects the transmitted sync burst signal in the output signal S370 of the vocoder decoder and generates the burst pulse synchronization index S351. The synchronization preamble detector 351 detects the transmitted output of the synchronization preamble in the output signal S370 of the vocoder decoder and generates a preamble synchronization index S353. The burst signal synchronization index S351 and the preamble synchronization index S353 are input to the synchronization detector controller 370. The synchronization detector controller 370 generates control output signals S360 to a reception demultiplexer Rx, which routes the output signal S370 of the vocoder decoder to a data path S326 or an audio signal path S325, an audio signal jamming control S365 that enables or disables the audio output clock signal S310 and S350, which provides bit timing information to a reception Rx timing block 380 to align reception data S326 Rx for demodulation.

[00106] Another example of a suitable synchronization detector 350 is shown in FIG. The output signal S370 of the vocoder decoder is input into the memory 352 and the synchronization preamble detector 351. A memory 352 is used to store the most recent samples of the output signal S370 of the vocoder decoder, which includes the received activation output signal. A suitable example of memory 352 is first-come-first-served (FIFO) or random access memory (RAM). The synchronization preamble detector 351 detects the transmitted synchronization preamble output signal in the output signal S370 of the vocoder decoder and outputs a SyncFlag signal (synchronization flag) S305. A signal modulation type signal S306 and a synchronization flag SyncFlag S305 are input to the synchronization detector controller 370. The synchronization detector controller 370 generates a modulation search signal S307, which is used to access the memory 352, search for the received activation output signal based on the clock offset signal S350, and evaluate the activation output signal to determine the type of modulation used in transmission. The resulting detected modulation type is output from the memory 352 as modulation type S306. The synchronization detector controller 370 also generates control output signals S360 to a reception demultiplexer Rx, which routes the output signal S370 of the vocoder decoder to a data path or an audio signal path, control S365 to mute the audio signal that enables or disables the audio output signal S310, and S350 a clock offset that provides bit timing information to a reception Rx timing block 380 for aligning reception data S326 Rx for demodulation.

[00107] An example of a suitable sync pulse detector 360 is shown in FIG. The output signal S370 of the vocoder decoder is input to a power calculation unit 361. Examples of a suitable power calculation unit 361 include an input signal squaring function block or an absolute value taking function calculated with respect to an input signal. The output signal S370 of the vocoder decoder is also input to the mixer function block 362, where it is multiplied by the in-phase and quadrature components of the reference frequency sine wave 1 363 and frequency sine wave 2 364 to generate components of the down-converted signal at a frequency of 0 Hz. The output signals 362 of the mixer are processed by a low-pass filter through LPF (LPF) 365 to eliminate high-frequency products of the multiplication unit in the mixed output signal. An example transfer function of a suitable LPF 365 takes the form:

where c = 0.0554, and ₁ = 2, a ₂ = 1, b ₁ = -1.9742, b ₂ = 0.9744. The magnitude of the in-phase and quadrature output signals of the LPF 365 are calculated by the amplitude determining unit 366 and added to the adder 367. The output of the adder 367 is input to a matched filter 368 that is matched to the transmitted sequence of the burst of synchronization pulses. Matching filters are known in the art. The output of the matched filter 368 is searched for the maximum peak in maximum search block 369. Once the maximum is found in the maximum search block 369, the index corresponding to the maximum time offset is output in the signal of the pulse train synchronization index S351.

[00108] An example of a suitable synchronization preamble detector 351 is shown in FIG. The output signal S370 of the vocoder decoder is processed by a matched filter 368, which is matched to the sequence of the synchronization preamble. Then, the output of the matched filter 368 is input to the maximum search unit 369, which searches for the maximum peak. As soon as the maximum is found in the maximum search block 369, the index corresponding to the maximum offset in time is output in the preamble synchronization index S353.

[00109] Another example of a suitable synchronization preamble detector 351 is shown in FIG. The output signal S370 of the vocoder decoder is processed by the filter in step 452. A suitable example of the filter in step 452 is a sparse filter with coefficients based on a bandpass filter filtered pulse response of the synchronization preamble sequence. A sparse filter has a structure with a finite impulse response with some of the coefficients set to zero, and leads to a reduction in computational complexity based on the smaller number of required factors due to zero coefficients. Sparse filters are known in the art. At step 453, the filter output is searched for the maximum positive and negative correlation peaks that match the expected pattern based on the distance of the negative and positive correlation peak. For example, 5 peaks should be found in step 453 based on a sequence 245 of a synchronization preamble, 3 positive peaks corresponding to a correlation with a pseudo-random noise (PN) sequence 243, and 2 negative peaks corresponding to a correlation with an inverted version of a PN sequence 244. In a suitable example, the synchronization detector must find at least 2 peaks to declare that a synchronization preamble is detected. At 461, the number of peaks detected is counted, and if most peaks are detected, the synchronization indicator flag is set to True at 460, indicating that a synchronization preamble has been detected. A suitable example of most peaks detected is 4 out of 5 peaks that match the expected pattern. If most peaks are not detected, then control proceeds to step 454, where the temporal distance between the positive peaks found in step 453 is compared with the expected distance PeakDistT1. PeakDistT1 is set as a function of the period of the PN sequence 242, since filtering the received preamble depending on the PN sequence 242 should provide a temporal distance between the correlation peaks, which is equal to a multiple of the period. If the temporal distance between the positive peaks is in the range PeakDistT1, the positive peak amplitudes are then checked against the PeakAmpT1 threshold in step 455. A suitable range for PeakDistT1 is plus or minus 2 samples. PeakAmpT1 is a function of the amplitudes of previously found peaks. In a suitable example, PeakAmpT1 is set so that the peaks found in step 453 do not differ in amplitude by more than a factor of 3 and the average peak amplitude does not exceed half the maximum peak amplitude observed to this point. If either checking the temporal distance of the positive peak in step 454 or checking the amplitude in step 455 fails, then the temporal distance of the negative peak is checked in step 456. If the temporal distance of the negative peak is in the range PeakDistT2, then the negative peak amplitudes are checked depending on the threshold PeakAmpT2 at step 457. A suitable range for PeakDistT2 is plus or minus 2 samples. PeakDistT2 is set as a function of the PN period of the sequence 242, and PeakAmpT2 is set as a function of the amplitudes of previously found peaks. If either checking the time distance of the positive peak in step 454 and checking the amplitude of the positive peak in step 455, or checking the time distance of the negative peak in step 456 and checking the amplitude of the negative peak in step 457, then the synchronization indicator flag is set to True in step 460, indicating that the synchronization preamble has been detected. If either checking the temporal distance of the negative peak in step 456 or checking the amplitude of the negative peak in step 457 fails, then the synchronization indicator flag is set to False in step 458, indicating that no synchronization preamble has been detected. It should be understood that different orders and combinations of steps will achieve the same result. For example, the detection of most peaks in step 461 can be done after checking the positive peak of steps 454 and 455.

[00110] An example of a suitable synchronization detector controller 370 is shown in FIG. 18a. Step 407 is an entry point in the controller that initializes the memory buffers and configures the initial state of the receiver. At 406, a synchronization search type is checked, indicating whether the synchronization signal is searched in the reception data Rx or in the path of the audio reception signal Rx. Step 372 is entered if a synchronization search is performed in the path of the receive audio signal Rx. Using the burst pulse synchronization index S351, the maximum burst of pulses and the synchronization index are searched for over a series of processing frames, N1 in step 372. Step 373 determines whether the maximum burst of pulses and the synchronization index that are searched in step 372 pass the criterion for successful search. An example of a suitable search decision criterion in step 373 has the form:

(S _maxmax ≥Th _SB ) and (i _Smax ≤ N _sync - N _guard )

where S _maxmax is the maximum of the bursts of synchronization pulses found from N1 processing frames, Th _SB is the detection threshold of the burst of synchronization pulses, i _Smax is the maximum index of the burst of synchronization pulses, N _sync is the number of processing frames that are searched, and N _guard is the waiting period in processing frames. If a burst of synchronization pulses is not found, the control returns back to step 406, and the search is restarted. If a burst of synchronization pulses is found, control proceeds to step 374, and an audio jamming control signal S365 is generated to prevent the output of the audio signal path to the speaker. In step 375, using the preamble synchronization index S353, the maximum preamble and the synchronization index by the number of processing frames, N2, are searched. Step 376 determines whether the maximum preamble and synchronization index that are searched in step 375 pass the criterion for a successful search. An example of a suitable search decision criterion at step 376 has the form:

where S _maxmax is the maximum of the bursts of synchronization pulses found from N1 processing frames, with ₁ and ₂ are the scaling factors, z _maxmax is the maximum of the output signals of the matched filter 368 in the synchronization preamble detector 351, P (i _Smax ) is the maximum power input in block 369 search maximum in the detector 360 bursts of synchronization pulses at the index of the maximum burst of synchronization pulses, i _Smax . If the synchronization preamble is not found at step 376, control returns back to step 406, and the search is restarted. If the synchronization preamble is found, the control signal S360 of the receive demultiplexer Rx is generated in step 378 to switch to the receive data path Rx in the demultiplexer 320. Then, control passes to 377, where the signal clock offset S350 is calculated. An example of a suitable timing offset calculation is of the form:

where i _zmax is the index at the maximum output of the matched filter 368 in the detector of the synchronization preamble 351 per frame, N _sync is the number of processing frames that are searched, N _samp is the number of samples in one frame, and k _max is the maximum phase of the output of the matched filter 368 in the detector 351 preamble synchronization on a single frame. Then, control proceeds to step 418, where the reception modem 330 Rx is enabled using the enable signal S354 of the reception modem Rx, then finally returns back to step 406, and the search is restarted. Step 372a is entered if a synchronization search is performed on the receive data path Rx. Steps 372a, 373a, 375a, and 376a function in exactly the same way as steps 372, 373, 375, and 376, respectively; the main difference is that the audio signal path is not suppressed and the demultiplexer does not switch from Rx receiving audio to Rx receiving data when the synchronization search type checked in step 406 is the receiving Rx data.

[00111] Another example of a suitable synchronization detector controller 370 is shown in FIG. 18b. Step 407 is an entry point in the controller that initializes the memory buffers and configures the initial state of the receiver. At 406, a synchronization search type is checked, indicating whether the synchronization signal is searched on the receive data path Rx or the audio receive signal path Rx. Then, control proceeds to step 411, where the preamble detector 351 is enabled. Step 412 checks the SyncFlag S305 signal, indicating that a synchronization preamble has been found, then confirms this by repeatedly checking the SyncFlag S305, a total of N times. A suitable value for N is 1 (that is, only 1 preamble is detected without confirmation) for destination terminal 600 and 3 for source terminal 100. If a synchronization preamble is found, an audio jamming control signal S365 is generated to prevent the audio path from outputting to the speaker. Then, the receive demultiplexer Rx control signal S360 is generated in step 378 to switch from the path of the receive audio signal Rx to the receive data path Rx in the demultiplexer 320. Then, control returns back to step 377, where the signal clock offset S350 is calculated. An example of a suitable timing offset calculation is of the form:

PulsePosition is the time distance from the positive correlation peak for the first reference point in time, and can be a positive or negative value. PeakDistance is the time distance between the positive correlation peak and the negative correlation peak. An example of a suitable first reference time point may be some sample position relative to the currently received speech frame. Another example of a suitable timing offset calculation is of the form:

PulsePosition is the time distance from the negative correlation peak to the second reference point in time and can be a positive or negative value. An example of a suitable second reference point in time may be some sample position relative to the current received speech frame. Then, control proceeds to step 414, where the modulation type is determined by the modulation search signal S307 by searching the memory 352 at a predetermined position, and the received activation output signal must be stored. Then, control proceeds to step 418, where the reception modem 330 Rx is enabled using the reception modem Rx of the reception modem S354. The demodulation scheme used in the resolution block S354 of the reception modem Rx is determined in step 418 by an input signal of modulation type S306. The control ultimately returns back to step 406, and the search is restarted. Step 411a is entered if synchronization is sought in the receive data path Rx. Steps 411a and 412a function in exactly the same way as steps 411 and 412, respectively; the main difference is that the path of the audio signal is not muffled, and the demultiplexer does not switch from the receiving audio Rx to the receiving Rx data, when the type of synchronization search checked in step 406 is the receiving Rx data. It should be understood that different orders and combinations of steps will achieve the same result. For example, the steps of the jamming audio path 374 and the path switching step 378 can be exchanged without affecting the full synchronization detection.

[00112] FIG. 19 is a suitable exemplary block diagram of a clock Rx 380 of the reception shown in FIG. The receive Rx timing 380 is used to align the boundary of the modulation frame in the data output from the vocoder decoder 390 so that demodulation can take place in the receive Rx data modem 330. The signal reception data S326 Rx is input to the buffer 381, where several samples are stored. Suitable examples of buffer 381 include first-come-first-served memory (FIFO) or random access memory (RAM). Samples from buffer 381 are input to a variable delay unit 382, where a time delay is applied to align a modulation frame boundary corresponding to a clock offset control signal S350. The suitable delay used in variable delay block 382 may be any number of samples from zero to frame size-1. The delayed signal is output as tuned receive data S330 Rx.

[00113] FIG. 20 is a suitable exemplary block diagram of a reception Rx data modem 330 shown in FIG. The two signals are demultiplexed in time from the input of the tuned reception data S330 Rx through the demultiplexer of the reception data 331 Rx modem; a demultiplexer jamming unit S332 and a demultiplexer reception data S333 Rx. Jamming of the S332 demultiplexer is a separation or jamming period that may exist between consecutive received messages, and it is separated from the tuned signal reception data S330 Rx if the separation or jamming signal was used in the transmitter. The demultiplexer receive data S333 Rx is a received modulated message signal input to the demodulator 335. The demodulator 335 demodulates the information bits of the received message from the configured receive data S330 Rx. The receive Rx data modem 330 uses a demodulation frame boundary determined by the receive Rx clocking 380 and a demodulation type indicator determined by the synchronization detector controller 370 to determine the position of the data signal pulse and calculate the output data symbol based on the position of the data signal pulse. An example of a suitable demodulator is a matched filter correlator, consistent with all allowed cyclic modulation pulse shifts applied by the transmission data modulator. Another example of a suitable demodulator is a matched filter correlator, matched to the filtered band-pass version of the pulse used by the transmission data modulator, where the band-pass filter represents the transmission characteristics of the channel.

SYSTEM

[00114] FIG. 21 is an exemplary case for using the system and methods disclosed herein. The diagram represents a typical example of an emergency call system integrated in a vehicle (eCall). Traffic accident 950 is shown as an accident between two vehicles. Other suitable examples of traffic accident 950 include many traffic accidents, a single traffic accident, a single flat tire of a vehicle, a single vehicle engine failure or other incident, with the vehicle malfunctioning or the user needing assistance. Vehicle Integrated System (IVS) 951 is located in one or more vehicles involved in a traffic accident 950, or may be located directly on a user. A system 951 integrated in a vehicle may consist of a source terminal 100 described herein. The system 951 integrated in the vehicle communicates over a wireless channel, which may consist of an uplink channel 501 and a downlink channel 502. The data transfer request may be received by the system integrated in the vehicle through the data channel or may be automatically or manually generated in the system integrated in the vehicle. Wireless tower 955 receives transmission from a vehicle integrated system 951 and communicates with a wired network comprising a wired uplink 962 and a wired downlink 961. A suitable example of a wireless tower 955 is a cell phone data tower consisting of an antenna, transceivers and reverse gear equipment known in the art for interacting with wireless uplink 501 and downlink 502. A wired network communicates with t Public Security Point (PSAP) 960, where emergency information transmitted by system 951 integrated into the vehicle can be received and control and data transferred. Point 960, responsible for public safety, may contain the terminal 600 destination described in the present description. The connection between the system 951 integrated in the vehicle and the public safety point 960 is achieved using the interaction diagrams described in the following sections.

[00115] Fig.22 is an exemplary diagram of the interaction of the sequences of synchronization and data transmission between the source terminal 100 and the terminal 600 destination. In this example, the uplink transmission sequence 810 is initiated by the destination terminal 600. The downlink transmission sequence 800 is the transmission of synchronization messages and data from the destination terminal 600 to the source terminal 100, and the uplink transmission sequence 810 is the transmission of synchronization messages and data from the source terminal 100 to the destination terminal 600. The downlink transmission sequence 800 is initiated at time t0 850 by the destination terminal 600 by the synchronization sequence 801. Suitable examples of synchronization sequences 801 are the synchronization sequences described in FIG. 8A, FIG. 8B and FIG. 8C. Following the synchronization sequence 801, the destination terminal 600 transmits a Start message 802 to instruct the source terminal 100 to start transmitting its uplink transmission sequence 810. Destination terminal 600 continues to transmit alternating synchronization 801 and Start message 802, and it waits for a response from source terminal 100. At t1 851, source terminal 100, having received Start message 802 from destination terminal 600, starts transmitting its own synchronization sequence 811 . Suitable examples of synchronization sequences 811 are the synchronization sequences described in FIG. 8A, FIG. 8B and FIG. 8C. Following the synchronization sequence 811, the source terminal 100 transmits a minimum data set or an “MSD” message 812 to the destination terminal 600. A suitable data example comprising an MSD message 812 includes a sensor or user data formatted by a data message formatter 210. At time t2 852, the destination terminal 600, having received the synchronization message 811 from the source terminal 100, begins to transmit a negative acknowledgment or “NACK” message 803 to the source terminal 100. The destination terminal 600 continues to transmit alternating synchronization 801 and the “NACK” message 803 until until it has successfully received the MSD message 812 from the source terminal 100. A suitable example of successfully receiving the MSD message 812 includes verifying the control by cyclic redundancy code performed on the MSD message 812. At t3 853, the destination terminal 600, having successfully received the MSD message, starts transmitting alternating synchronization 801 and an acknowledgment or “ACK” message 804. The source terminal 100 may attempt to send the MSD message 812 multiple times (813, 814) until it receives the ACK message 804. In a suitable example, if the source terminal 100 attempts to send an MSD message more than 8 times, where each attempt is a different version of the redundancy, it switches to a more stable modulation scheme identified by the activation signal S236. A suitable example of a more robust modulation scheme includes increasing the duration of the modulation frame T _MF while maintaining a constant number of time points, as described previously. At time t4 854, the source terminal 100, having received the ACK message 804 from the destination terminal 600, stops transmitting the MSD message 814. In a suitable example, a retransmission is requested by the destination terminal 600 by sending the initial message 802 again after a predetermined number of ACK messages 804 are sent by the destination terminal 600.

[00116] Fig.23A is another exemplary diagram of the interaction of sequences of synchronization and data transmission between the source terminal 100 and the terminal 600 of the destination. In this case, the uplink transmission sequence 810 is initiated by the source terminal 100. The uplink transmission sequence 810 is initiated at time t0 850a by the source terminal 100 by voice data 815 by configuring the baseband 200 of the transmission of the source terminal 100 to the transmission audio path S225 Tx. At time t1 851a, the source terminal 100 configures the main transmission frequency band 200 to the transmission data path S230 Tx and starts transmitting its synchronization sequence 811, followed by the MSD message 812. At time t2 852a, the destination terminal 600, having received the synchronization message 811 from the source terminal 100, starts transmitting the alternating timing 801 and the NACK message 803 to the source terminal 100. The destination terminal 600 continues to transmit the alternating timing 801 and the NACK message 803 until until it successfully receives the MSD message from the source terminal 100. At time t3 853, the destination terminal 600, having successfully received the MSD message 813, starts transmitting alternating synchronization 801 and an acknowledgment or “ACK” message 804. The source terminal 100 may attempt to send the MSD message 812 multiple times until it receives the ACK message 804, where each attempt is a different version of the redundancy. At time t4 854, the source terminal 100, having received the ACK message 804 from the destination terminal 600, interrupts the transmission of the MSD message 814.

[00117] Fig.23B is another exemplary diagram of the interaction of sequences of synchronization and data transmission between the source terminal 100 and the terminal 600 destination. In this case, the uplink transmission sequence 810 is initiated by the source terminal 100. Instead of transmitting uplink voice data to initiate the transmission, the source terminal 100 transmits alternating synchronization 811 and a “Send” message 805 (SEND) at time t0 850b. At time t1 851b, the destination terminal 600, having received a “Send” message 805 from the source terminal 100, transmits alternating synchronization 801 and a “Start” message 802. At time t2 852b, the source terminal 100, having received the “Start” message 802 from the destination terminal 600, transmits a synchronization sequence 811, followed by the MSD message 812, to the destination terminal 600. At time t3 853b, the destination terminal 600, having received the synchronization message 811 from the source terminal 100, transmits the alternating synchronization 801 and the NACK message 803 to the source terminal 100. At time t4 854b, the destination terminal 600, having successfully received the MSD message, transmits the alternating synchronization 801 and message 804 "ACK". After receiving the ACK message 804 from the destination terminal 600, the source terminal 100 interrupts the transmission of the MSD message.

[00118] Fig.24A is an exemplary diagram of the interaction of sequences of synchronization and data transmission between the source terminal 100 and the terminal 600 of the destination. In this case, data is requested and transmitted by both the source terminal 100 and the destination terminal 600 on the uplink and downlink, respectively, in support of bidirectional data transmission. The downlink transmission sequence 800 is initiated at time t0 850 by the destination terminal 600 with alternating synchronization sequence 801 and a start message 802. At time t1 851, the source terminal 100, having received the Start message 802 from the destination terminal 600, starts transmitting its synchronization sequence 811, followed by data 812. At time t2 852, the destination terminal 600 transmits alternating synchronization 801 and a NACK message 803 to until it successfully receives data 812 from the source terminal 100, after which the destination terminal 600 then sends an alternating synchronization sequence 801 and an ACK message 804. At time t4 854, the source terminal 100, having received the ACK message 804 from the destination terminal 600, interrupts its data transmission. At time t5 855, the destination terminal 600 transmits an alternating synchronization sequence 801 and a “Send” message 805 indicating a downlink data request. At t6 856, the source terminal 100, upon detection of a Send message 805, responds with an alternating synchronization sequence 811 and a Start message 816. At time t7 857, the destination terminal 600, after detecting the “Start” message 816, responds with a synchronization sequence 801 followed by data 806. At time t8 858, the source terminal 100 transmits an alternating synchronization sequence 811 and a “NACK” message 817 until it will not successfully receive data 806 from the destination terminal 600, to which, at t9 859, the source terminal 100 sends an alternating synchronization sequence 811 and an ACK message 818. At t10 860, the destination terminal 600, having received the ACK message 818 from the source terminal 100, interrupts the transmission of its data 806. One skilled in the art will understand that the interactions described herein are symmetrical and can be triggered by the source terminal 100. One of ordinary skill in the art will also understand that the synchronization sequence, the Start message, the NACK message, and the ACK message can be the same or different sequences between messages transmitted in descending order. Institute of communication and uplink communication.

[00119] Fig.24B is another exemplary diagram of the interaction of sequences of synchronization and data transmission between the source terminal 100 and the destination terminal 600, in which data is requested and transmitted by both the source terminal 100 and the destination terminal 600 on the uplink and downlink , respectively. The difference between the interactions according to FIG. 24B and FIG. 24A takes place at t3 853. In this example, the alternating synchronization 801 and the “Send” message 805 are transmitted by the destination terminal 600 instead of the alternating synchronization and the “ACK” message. In this example, a “Send” message 805 is used to indicate that the destination terminal 600 has successfully received data 812 of the source terminal 100, and this leads to the source terminal 100 interrupting its transmission of data to t4 854. The “Send” message also indicates a request from the terminal 600 destinations to send data on the downlink.

[00120] FIG. 25 is an exemplary transmission data packet compilation diagram in which a user data length is less than a transmission data packet length. The user data segment 900 is combined into a transmission data packet 806 or 812 along with a previous length indicator 910 and a subsequent sequence of fill bits 911, which serves to fill the data to the end of the transmission data packet. A suitable example of a length indicator 910 is a value from 1 to 3 bytes indicating the length of a user data segment 900. A suitable example of the length of a packet 806 or 812 of transmission data may be 100-200 bytes. A suitable example of pad bits 911 includes the binary value “0”. One skilled in the art will recognize that fill bits 911 may contain a binary value of “1” or may contain a pattern of binary values of “1” and “0”.

[00121] FIG. 26 is an exemplary transmission data packet composition diagram in which a user data length is greater than a transmission data packet length. User data 900 is divided into multiple segments such that the first segment plus a length indicator is equal to the length of the transmission data packet, and subsequent segments are equal to the length of the transmission data packet. If the user data is not an integer multiple of the length of the transmission data packet, then the last segment contains padding. In the example of FIG. 26, user data is divided into two segments. The first user data segment 901 is combined into a transmission data packet 806 or 812 along with a previous length indicator 910. The second user data segment 902 is combined into a transmission data packet 806 or 812, and since the segment is less than the length of the transmission data packet, padding 911 is used to fill the data to the end of the transmission data packet.

[00122] FIG. 27A is an example diagram of an interaction of a transmission data request sequence and a transmission data response sequence in which a user data length is greater than a transmission packet size. Initiated by the “Start” messages of the requesting terminal in either downlink transmission 800 or uplink transmission 810 during t20 870, a first transmission data packet 806 or 812, consisting of a length indicator 910 and a first user data segment 901, is transmitted by the responding terminal. During t21 871, since the responding terminal has not yet received the ACK message, it again starts transmitting user data in a second attempt 903. At t22 872, the responding terminal, having received the ACK message, interrupts the transmission of the first data packet 806 or 812. At time t23 873, the requesting terminal, after evaluating the length indicator 910 to determine how many segments are expected, requests the next transmission data packet 806 or 812 by transmitting the initial messages to the responding terminal. At time t24 874, the responding terminal, having received the initial message from the requesting terminal, starts transmitting the next data packet 806 or 812 containing the next user data segment 902 and pad 911 (in this example, the next data packet is the last data packet). During t25 875, the responding terminal, having received the ACK message, interrupts its data transmission. One skilled in the art will understand that the interactions described herein are symmetrical, whereby the requesting and responding terminals can be either the source terminal 100 or the destination terminal 600. One skilled in the art will also understand that user data can span more than two transmission data packets 806 or 812.

[00123] FIG. 27B is another exemplary diagram of an interaction of a transmission data request sequence and a transmission data response sequence in which a user data length is greater than a transmission packet size. In this example, after the first transmission data packet 806 or 812 is requested using the “Start” messages transmitted by the requesting terminal, subsequent transmission data packets 806 or 812 are automatically transmitted by the responding terminal based on the receipt of the ACK message from the requesting terminal. In this example, the requesting terminal does not send a “Start” message to initiate the transmission of a subsequent packet 806 or 812 of transmission data from the responding terminal. At time t31 881, the answering terminal, having received the ACK message, interrupts the transmission of the first data packet and then immediately starts transmitting the next transmission data packet 806 or 812, separated only by the synchronization sequence. At time t32 882, the requesting terminal, having received the synchronization sequence, starts transmitting NACK messages until it successfully receives the transmission data packet 806 or 812. During t33 883, having successfully received the transmission data packet 806 or 812, the requesting terminal starts transmitting ACK messages. At time t34 884, the responding terminal receiving the ACK message interrupts transmission of the transmission data packet 806 or 812.

[00124] FIG. 27C is another exemplary diagram of an interaction of a transmission data request sequence and a transmission data response sequence in which a user data length is greater than a transmission packet size. In this example, after the first transmission data packet 806 or 812 is requested using the “Start” messages transmitted by the requesting terminal, subsequent transmission data packets 806 or 812 are automatically transmitted by the responding terminal based on the receipt of the ACK message from the requesting terminal. In this example, the requesting terminal does not send Start messages to initiate the transmission of a transmission data packet 806 or 812 from the responding terminal, nor does the requesting terminal send NACK messages. At t41 891, the answering terminal, having received the ACK message, interrupts the transmission of the first data packet and then immediately starts transmitting the next transmission data packet 806 or 812, separated only by the synchronization sequence. During t42 892, having successfully received the transmission data packet 806 or 812, the requesting terminal starts transmitting ACK messages. As soon as the responding terminal receives ACK messages, it interrupts the transmission of a packet of data 806 or 812.

[00125] FIG. 27D is another exemplary diagram of an interaction of a transmission data request sequence and a transmission data response sequence in which a user data length is greater than a transmission packet size. Fig. 27D is an alternative for the example interaction diagram shown in Fig. 27B. In the example of FIG. 27D, the time interval at t32 882 between the ACK message of the requesting terminal for the first user data segment 903 and the NACK message for the next user data segment 902 is eliminated. This helps maintain timing in the responding terminal so that it does not need to be re-synchronized for the synchronization sequence of the requesting terminal.

[00126] One skilled in the art will recognize that responding terminals can automatically transmit data packets following the first data packet without transmitting a synchronization sequence separator. In this case, the synchronization sequence is sent before the first transmission data packet 806 or 812, then, after receiving the ACK messages, the responding terminal automatically transmits the subsequent data packet without sending the synchronization. One skilled in the art will also understand that a length indicator 910 may also be transmitted with other data segments in addition to the first.

[00127] In the interaction diagrams disclosed herein, there may be error conditions that need to be answered and that are processed in a predetermined manner. The following sections provide examples with respect to handling the error condition corresponding to the interaction diagrams disclosed herein. In each example, the error condition is outlined along with the corresponding response description. One skilled in the art will understand that the error processing described in the present description can be equally applied to the source terminal or the destination terminal in both unidirectional and bidirectional embodiments.

[00128] An exemplary error condition occurs when the source terminal does not detect a transmitted synchronization preamble. In an exemplary response, the source terminal delays the transmission of the MSD message until a predetermined number of synchronization preambles are detected.

[00129] Another exemplary error condition occurs when the source terminal incorrectly detects the synchronization preamble. In an exemplary response, the source terminal delays the transmission of the MSD message until a predetermined number of detected synchronization preambles leads to the same sample offset.

[00130] Another exemplary error condition occurs when the source terminal falsely detects a synchronization preamble, although there has not been any actually transmitted. In an exemplary response, the source terminal ignores falsely detected synchronization preambles. The source terminal only initiates MSD transmission if a predetermined number of detected synchronization preambles leads to the same estimate of the sample offset.

[00131] Another exemplary error condition occurs when the destination terminal does not detect a transmitted synchronization preamble. In an exemplary response, the destination terminal does not start to decode the MSD message, but continues to transmit Start messages to initiate the source terminal to re-initiate the MSD transmission after a predetermined number of Start messages have been received (including the sequence of synchronization preamble).

[00132] Another exemplary error condition occurs when the destination terminal incorrectly detects the synchronization preamble. In an exemplary response, the destination terminal incorrectly decodes the received MSD data in all redundancy versions. Based on incorrectly decoded data, the destination terminal can re-initiate the MSD transmission by sending Start messages to the source terminal.

[00133] Another exemplary error condition occurs when the destination terminal falsely detects a synchronization preamble, although there has not been any actually transmitted. There is no answer, since the probability of this case is very low. The destination terminal does not begin to monitor its received signal until it waits for the synchronization preamble from the source terminal.

[00134] Another exemplary error condition occurs when the source terminal incorrectly interprets the “Start” message as a NACK message. In an exemplary response, if the MSD transmission has not started, the source terminal delays the transmission of the MSD until it receives the “Start” message. In another exemplary response, if the MSD transmission continues, the source terminal delays the reinitialization of this transmission.

[00135] Another exemplary error condition occurs when the source terminal incorrectly interprets the “Start” message as an ACK message. In an exemplary response, if the MSD transmission did not start, the source terminal ignores any ACK message. In another exemplary response, the source terminal ignores the ACK if previous messages were interpreted as a “Start” message. In another exemplary response, if the previous messages were NACK messages, the source terminal goes into standby mode and ends the MSD transmission if the next message is also interpreted as an ACK. In another exemplary response, if the previous message was interpreted as an ACK, the source terminal erroneously terminates the MSD transmission. The probability of this event is low, however, if it does occur, the destination terminal can re-initiate the transmission, again by sending a request with Start messages.

[00136] Another exemplary error condition occurs when the source terminal incorrectly interprets the NACK message as a “Start” message. In the sample answer, the only NACK that is interpreted as “Start” has no effect on MSD transmission. In another exemplary response, a sequence of NACK messages that are interpreted as “Start” messages may cause the transmitter of the source terminal to re-initiate the MSD. The destination terminal does not expect this and will refuse to receive incoming data, realizing this through incorrectly decoded data. Based on incorrectly decoded data, the destination terminal may request the source terminal to re-initiate the transmission by sending a “Start” message.

[00137] Another exemplary error condition occurs when the source terminal incorrectly interprets the NACK message as an ACK message. In the example response, if the previous message was interpreted as a “Start” message, the source terminal ignores any ACK message. In another exemplary response, if the previous message was interpreted as a NACK message, the source terminal waits for another ACK message. If the next message is not another ACK message, the current ACK message is ignored. In another exemplary response, if the previous message was also erroneously detected as an ACK message, the source terminal may complete the MSD transmission, although the destination terminal has not yet correctly received the MSD. The probability of this event is low, however, if it does occur, the destination terminal can re-initiate the transmission, again by sending a request with Start messages.

[00138] Another exemplary error condition occurs when the source terminal incorrectly interprets the ACK message as a “Start” message. In an exemplary answer, the source terminal will not interrupt the transmission of additional versions of MSD redundancy, since the usual condition for interruption is to receive a predetermined number of ACK messages. If more subsequent messages are interpreted as Start (START) messages, the source terminal may re-initiate the MSD transmission. Ultimately, the destination terminal will stop transmitting messages. The source terminal will ultimately determine that the destination terminal is no longer transmitting synchronization frames, and will reset itself, thereby stopping additional transmissions.

[00139] Another exemplary error condition occurs when the source terminal incorrectly interprets the ACK message as a NACK message. In an exemplary response, the source terminal will continue to transmit redundancy versions until ACK messages are detected correctly. Ultimately, the destination terminal will stop transmitting messages. The source terminal will ultimately determine that the destination terminal is no longer transmitting synchronization frames, and will reset itself, thereby stopping additional transmissions.

[00140] Another exemplary error condition occurs when the source terminal determines that the received message is unreliable. In an exemplary response, if the received messages are “Start” messages, the source terminal continues to read unreliable messages, but with a lower weighting factor than if the messages were received with a reliable determination. Subsequent triggering of an event based on counting received messages will require a larger predetermined number of received untrusted messages, if the messages were received with a reliable determination. In another exemplary response, if the unreliable received messages are NACK messages or ACK messages, the source terminal may ignore these messages.

[00141] Another exemplary error condition occurs when the destination terminal is not able to detect the transmitted MSD due to noise or other channel distortions. In an exemplary response, after trying to decode a predetermined number of redundancy versions, the destination terminal may request the source terminal to re-initiate the transmission by sending a “Start” message. In a re-triggered transmission, the source terminal may use a robust modulator that is less susceptible to noise and other channel distortions.

[00142] Another exemplary error condition occurs when the destination terminal cannot evaluate the activation signal correctly. In an exemplary response, if the destination terminal considers the activation signal detection unreliable, it selects the fast (or normal) modulation mode for the first attempt to demodulate MSD data. For any other set of predetermined number of received versions of MSD data redundancy, the destination terminal may use robust modulation mode to demodulate the data.

[00143] Thus, an apparatus and method for reliably and efficiently transmitting data within a band through a speech codec in a wireless communication system are disclosed herein. Those skilled in the art will understand that information and signals can be represented using any of a variety of different technologies and methods. For example, data, instructions, commands, information, signals, bits and symbols that can be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof . In addition, although embodiments have been described primarily with respect to a wireless communication system, the described methods can be applied to other in-band data systems that are fixed (non-portable) or do not include a wireless channel.

[00144] Those skilled in the art will further appreciate that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments disclosed herein may be implemented as electronic hardware, software, or combinations thereof. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been generally described above with respect to their functionality. Whether functionality such as hardware or software is implemented depends on the particular application and the structural constraints imposed on the whole system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the protection scope of the present invention.

[00145] The various illustrative logic blocks, modules, and circuits described in conjunction with the aspects disclosed herein may be implemented or implemented by a general purpose processor, digital signal processor (DSP), custom integrated circuit (ASIC), programmable gate array (FPGA) or other programmable logic device, logic on discrete elements or transistors, discrete hardware components, or any combination thereof designed to complements the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other suitable configuration.

[00146] The steps of a method or algorithm described in conjunction with the embodiments disclosed herein may be directly implemented in hardware, a software module executed by a processor, or a combination thereof. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. The storage medium is connected to the processor so that the processor can read information and write information to the storage medium. In the alternative, the storage medium may be an integral part of the processor. The processor and storage media may reside in the ASIC. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

[00147] The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown in the present description, but it should receive the broadest interpretation consistent with the principles and new features disclosed in the present description.

Claims (16)

1. A method for controlling bidirectional data transmissions from a destination terminal in an in-band data transmission system, the method comprising:
transmitting the sent signal from the destination terminal;
interrupting the transmission of the sent signal after detecting the first received signal, the first received signal indicating successful reception of the sent signal from the source terminal;
transmitting a synchronization signal from a destination terminal;
transmitting a user data segment from the destination terminal using the first modulation scheme;
interrupting the transmission of the user data segment after detecting the second received signal, the second received signal indicating the successful reception of the user data segment from the source terminal, and
switching to a second modulation scheme if the destination terminal receives a predetermined amount of a third received signal, the third received signal indicating an unsuccessful reception of a user data segment from the source terminal. 2. The method according to claim 1, in which the transmission of the sent signal is preceded by:
transmitting a start signal from a destination terminal;
interrupting the transmission of the start signal after detecting the fourth received signal, the fourth received signal indicating successful reception of the start signal from the source terminal;
transmitting a NACK signal from the destination terminal, whereby the source terminal is forced to respond in a first predetermined manner;
interrupting the transmission of the NACK signal after detecting a successfully received initial data message of the terminal;
transmitting the ACK signal from the destination terminal, whereby the source terminal is forced to respond in a second predetermined manner; and
interruption of ACK signal transmission after a predetermined number of ACK signals have been transmitted. 3. The method according to claim 1, in which the sent signal contains a synchronization signal, followed by a sent message. 4. The method of claim 2, wherein the start signal comprises a synchronization signal, followed by a start message. 5. The method of claim 2, wherein the NACK signal comprises a synchronization signal, followed by a NACK message. 6. The method according to claim 2, in which the ACK signal contains a synchronization signal, followed by an ACK message. 7. The method according to claim 2, in which the successfully received data message of the source terminal is a data message verified through monitoring using a cyclic redundancy code. 8. A device for controlling bidirectional data transmissions from a destination terminal in an in-band data transmission system, comprising:
CPU;
memory in electronic communication with the processor; and
commands stored in memory, and the teams are able to perform the steps:
transmission of the sent signal from the destination terminal;
interrupting the transmission of the sent signal after detecting the first received signal, the first received signal indicating successful reception of the sent signal from the source terminal;
transmitting a synchronization signal from a destination terminal;
transmitting a user data segment from the destination terminal using the first modulation scheme;
interrupting the transmission of the user data segment after detecting the second received signal, the second received signal indicating the successful reception of the user data segment from the source terminal, and
switching to a second modulation scheme if the destination terminal receives a predetermined amount of a third received signal, the third received signal indicating an unsuccessful reception of a user data segment from the source terminal. 9. The device of claim 8, in which the memory further comprises instructions, the instructions being capable of performing the following steps preceding the step of transmitting the sent signal:
transmitting a start signal from a destination terminal;
interruption of the transmission of the start signal after detecting the fourth received signal, while the fourth received signal indicates successful reception of the start signal from the source terminal;
transmitting a NACK signal from the destination terminal, whereby the source terminal is forced to respond in a first predetermined manner;
interrupting the transmission of the NACK signal after detecting a successfully received initial data message of the terminal;
transmitting the ACK signal from the destination terminal, whereby the source terminal is forced to respond in a second predetermined manner; and
interruption of ACK signal transmission after a predetermined number of ACK signals have been transmitted. 10. The device of claim 8, in which the sent signal consists of a synchronization signal, followed by a sent message. 11. The device according to claim 9, in which the start signal consists of a synchronization signal, followed by a start message. 12. The device according to claim 9, in which the NACK signal consists of a synchronization signal, followed by a NACK message. 13. The device according to claim 9, in which the ACK signal consists of a synchronization signal, followed by an ACK message. 14. The device according to claim 9, in which the successfully received data message of the source terminal is a data message verified through monitoring using a cyclic redundancy code. 15. A device for controlling bidirectional data transmissions from a destination terminal in an in-band data transmission system, comprising:
means for transmitting the sent signal from the destination terminal;
means for interrupting the transmission of the sent signal after detecting the first received signal, the first received signal indicating successful reception of the sent signal from the source terminal;
means for transmitting a synchronization signal from a destination terminal;
means for transmitting a user data segment from the destination terminal using the first modulation scheme;
means for interrupting the transmission of the user data segment after detecting the second received signal, the second received signal indicating the successful reception of the user data segment from the source terminal,
means for switching to a second modulation scheme if the destination terminal receives a predetermined amount of a third received signal, the third received signal indicating an unsuccessful reception of a user data segment from the source terminal. 16. The device according to clause 15, in which the means for transmitting the sent signal is preceded by:
means for transmitting a start signal from a destination terminal;
means for interrupting the transmission of the start signal after detecting the fourth received signal, in which the fourth received signal indicates successful reception of the start signal from the source terminal;
means for transmitting the NACK signal from the destination terminal, whereby the source terminal is forced to respond in a first predetermined manner;
means for interrupting the transmission of the NACK signal after detecting a successfully received source data message of the terminal;
means for transmitting the ACK signal from the destination terminal, by which the source terminal is forced to respond in a second predetermined manner; and
means for interrupting the transmission of the ACK signal after a predetermined number of ACK signals have been transmitted.

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