© 2005 AIRBIQUITY, INC. A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 37 CFR § 1.71(d).
This invention is related to wireless telecommunications and more specifically to systems and methods to support the transmission of digital data over the audio channel of a wireless telecommunications network while a voice conversation is in progress.
Systems and methods have been disclosed in the past for transmitting digital data over the voice channel of a wireless telecom network. Voice services have the advantages of low cost, high reliability and wide availability across various wireless networks and technologies. Digital wireless data services by contrast are sometimes unreliable, and can vary in bandwidth, delay and other parameters across different networks and technologies.
Moreover, transmitting data in the voice channel has the characteristic that a voice call connection must be established. This enables substantially simultaneous voice and data communications. Thus, for example, an emergency call taker or concierge operator can talk to a person who requires assistance, and at the same time receive data such as the person's location or physiological or medical data.
The prior art suggests simultaneous transmission of voice and data over a wireless voice channel by carving out a frequency band, using notch filtering, to be used exclusively for data. Other prior art teaches simultaneous voice and data transmission by encoding the digital data into audio frequency tones that will pass through the digital wireless network. Another technique is called “blank and burst”—it calls for “blanking” or muting the audio voice channel for a brief interval, and then transmitting the digital data (in the form of audio tones) over the channel during that interval. Hopefully, the data interval is short enough to not interfere with the voice conversation. The need remains for improvements in this field to enable digital data transfer through the voice channel of a digital wireless network concomitantly with a voice conversation and without interrupting the voice conversation.
In one embodiment, an input receives digital data for transmission through the wireless voice channel. A voice activity detector determines that speech is being generated from the local end of the audio channel. An inband signaling modem modulates digital data into synthesized tones. A controller gives priority to speech over modem tones for transmission over the voice channel of a digital wireless telecommunications network. A modem activity detector determines that synthesized tones are present in the incoming audio at the remote end of the audio channel. A second controller mutes the audio so that modem tones are not heard in the voice conversation. A second inband signaling modem demodulates the synthesized tones into digital data. An output transmits digital data that has been received over the network.
Additional aspects and advantages will be apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings.
Preliminarily, it should be noted that the drawing figures are not strictly hardware or software diagrams. Rather, most of the elements shown in the figures will involve a combination of hardware and software in a practical implementation. The present invention can be implemented in various combinations of hardware and software, subject to numerous detailed design choices, all of which should be deemed within the scope of the invention.
The NAD either communicates to a wireless telecommunications network as a circuit switched call or to a wireless internet access point as an Internet Protocol (IP) packet switched Voice Over Wireless LAN (VoWLAN) call. The digital wireless telecommunications network and the wireless internet access point require that the audio PCM signal be processed by a voice coder (vocoder) to reduce the bandwidth required for transmission. The vocoder compresses the information associated with human speech by using predictive coding techniques. The call can be routed from the Public Switched Telephone Network (PSTN) to the IP network or vice versa.
The call is received at the modem bank by a Modem Activity Detector (MAD). The MAD processes the incoming PCM audio and detects the presence of synthesized audio tones through an algorithm analyzing signal energy and frequency content. If the MAD determines that synthesized tones are not present, the modem activity status is used to control a telephony switch to route the audio to a codec for transformation to an analog voice signal. If the MAD detects synthesized audio tones, the modem activity status is used to route the audio through the telephony switch to an IBS modem. Simultaneously, audio noise from a Comfort Noise Generator (CNG) is routed by the telephony switch to the codec.
The IBS modem decodes the synthesized audio tones into digital navigation data. The navigation data is passed to a location processing algorithm that filters and validates the incoming data based on past samples of a multiplicity of navigation information types including timestamp, location, ground speed, and ground track angle. The navigation data is then output to a Geographic Information System (GIS) application for reverse geocoding and display.
The NAD receives the call where the vocoder reconstitutes the coded voice signal into an audio PCM signal. The PCM audio is processed by a MAD that detects the synthesized audio tones from the modem bank and provides the modem activity status to the IBS modem. If the MAD indicates that synthesized tones are not present, the IBS modem forwards the PCM audio to the codec for conversion to an analog signal that can be played over a speaker. If synthesized tones are present, the IBS modem mutes the incoming audio by sending PCM audio that represents silence to the codec. The IBS modem then decodes the tones into the digital data, such as a work order assignment, sent by the application. This data is sent to a mobile computing platform, such as a laptop computer.
For digital data to be transmitted from the wireless node to the modem bank, the codec digitizes an analog voice signal into PCM audio. The VAD determines if speech is present in the PCM audio and passes the voice activity status to the MIBS modem. If speech is present, the MIBS modem passes it to the vocoder. Otherwise it modulates the digital data received from the mobile computing platform into synthesized audio tones and passes them to the vocoder for transmission over the telecommunications network via the NAD.
The modem bank receives the call from the wireless node and routes the audio to a combined MAD/MIBS modem. The MAD determines if modem activity is present and passes the status to a switch. If modem activity is not present, the audio PCM is routed to the codec for conversion to an analog audio signal that may be played on a speaker. If synthesized audio tones are present, the MIBS modem demodulates the digital data and passes it to the destination application. The switch receives status that modem activity is present and passes PCM audio from the CNG to the codec for conversion to an analog signal to be played on a speaker.
For digital data to be transmitted from the modem bank to the wireless node, the VAD analyzes the PCM audio from the codec that represents the analog voice signal and generates a voice activity status signal. If speech is present, the combined MAD/MIBS modem forwards the PCM audio to the telecommunications network without alteration. Otherwise, the MIBS modem modulates the digital data received from the application using a set of synthesized audio tones that are different from those generated by the MIBS modem in the wireless node. These synthesized audio tones are transmitted over the telecommunications network over a plurality of networks such as the PSTN, the internet using VoIP and local area networks using VoWLAN.
The NAD receives the audio from the telecommunications network and forwards it to the vocoder which reconstitutes the signal into audio PCM. The audio PCM is analyzed by a MAD that provides status to the MIBS modem that synthesized tones are present. If synthesized tones are not present, the PCM audio is passed to the codec without change and converted to an analog signal for playing on a speaker. Otherwise, the MIBS modem passes PCM audio that represents silence to the codec, resulting in silence being reproduced at the speaker. The MIBS modem demodulates the audio based on the second set of synthesized audio tone frequencies and passes the digital data to the mobile computing platform.
It will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. The scope of the present invention should, therefore, be determined only by the following claims.