SYSTEM AND METHOD OF DUPLEX WIRELESS AUDIO LINK OVER BROADCAST CHANNELS
A device and method of duplex audio communication over a broadcast channel are disclosed. The device and method disclosed in the present invention use the clear channel technique to automatically select an un-occupied channel for the transmit side and utilizes an identification embedded in a sub-channel to allow the receiver to automatically tune to the channel used by the transmitter. The clear channels may be determined by respective transceivers or determined by a master transceiver.
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The current application is a divisional application of and claims priority to U.S. Non-Provisional patent application Ser. No. 12/895,143, entitled “System and Method of Duplex Wireless Audio Link over Broadcast Channels”, filed on Sep. 30, 2010. This application is related to U.S. Non-Provisional patent application Ser. No. 12/137,535, entitled “Frequency Modulation (FM) Clear Channel Scanning System and Method of Using Same”, filed on Jun. 11, 2008, U.S. Non-Provisional patent application Ser. No. 12/172,147, entitled “Channel Coordination between a Wireless Earphone and a Transmitter,” filed Jul. 11, 2008, U.S. Non-Provisional patent application Ser. No. 12/473,281, entitled “Radio Transmitter and Radio Receiver with Channel Condition Assessment”, filed May 28, 2009, and U.S. Non-Provisional patent application Ser. No. 12/495,796, entitled “Systems for Channel Coordination of Audio and Data Transmission in a Broadcast Band”, filed on Jun. 30, 2009. These U.S. patent applications are hereby incorporated by reference in their entireties.
FIELD OF THE INVENTIONThe present invention relates to wireless audio communication systems. In particular, the present invention relates to duplex wireless audio communication systems that utilize an auxiliary channel to automatically tune to an available channel within a radio band.
BACKGROUNDLow-power frequency modulation (FM) transmission in the FM broadcast channels is a permissible application in many countries for personal use as long as the transmitted power is in compliance with local regulatory standards. On the other hand, cellphones have been widely used almost in all regions around the world. In U.S. patent application Ser. No. 12/137,535, a system and method are disclosed to allow a transmitter to automatically select a clear radio channel that is not occupied by others so as to achieve the best possible transmission quality. In U.S. patent application Ser. No. 12/495,796, a system and method are disclosed which allow an audio link automatically established between an audio transmitter and an audio receiver. The system and method disclosed in U.S. patent application Ser. No. 12/495,796 rely on the clear channel technique disclosed in U.S. patent application Ser. No. 12/137,535 and a handshaking technique to establish the audio link automatically. Wireless earphones are one such application based on the invention of U.S. patent application Ser. No. 12/495,796, where the transmitter may be coupled to a cellphone or a portable media player to allow the audio heard on a matched wireless earphone.
The wireless earphone application can be further extended to allow two-way audio communication between two devices. In other words, the earphone becomes a speakerphone or a hand-free headset which not only receives audio but also provides audio using a microphone. The speakerphone comprises a speaker to deliver amplified audio transmitted from a portable device such as a cellphone or multimedia player, and a microphone to pick up the sound at the remote side and to relay it to the portable device. A speakerphone according to the above description will be useful for group conference call. For applications in a large group conference call, the remote speakerphone may use multiple microphones to pick up sound from multiple conference participants. The wireless speakerphone is also an ideal application for hand-free cellphone operation during driving a vehicle, where the wireless speakerphone can be mounted on the visor or a place close to the mouth of the driver and the wireless speakerphone communicates with the cellphone through the wireless audio link. Therefore, the driver can have conversation through the cellphone without holding the cellphone close to his ear/mouth. The wireless speakerphone can be based on the low-power FM technology which is mature and readily available worldwide. Such duplex audio link will be very useful and desirable for various wireless audio applications. However, there are broadcasters using assigned channels which are not suitable to use these channels for low-power transmission for personal use. Also, there may be channels being used by other nearby which may cause interference if such channels are used. Furthermore, it is desirable to have an easy to use speakerphone system that can automatically coordinate channel selection and tuning.
SUMMARY OF THE INVENTIONMethods and devices for duplex audio communication over broadcast channels are disclosed. In an embodiment of the present invention, a method of coordinating tuning between a first transceiver and a second transceiver for duplex audio communication is disclosed. The method comprising: determining a first radio channel in a radio band; transmitting a first control message at the first radio channel using the first transceiver; determining a second radio channel in the radio band; transmitting a second control message at the second radio channel using the second transceiver; searching for a second ID in the second control message over channels within the radio band to identify the second radio channel using the first transceiver; and searching for a first ID in the first control message over channels within the radio band to identify the first radio channel using the second transceiver. After the first radio channel and the second radio channel are established, the method further comprises receiving second audio from the second transceiver at the second radio channel using the first transceiver and receiving first audio from the first transceiver at the first radio channel using the second transceiver.
In yet another embodiment according to the present invention, a method of coordinating tuning is disclosed where a transceiver is designated as a master and is used to determine a first radio channel and a second radio channel. The first transceiver transmits identification information in a first message at the first radio channel for the slave transceiver to identify the first radio channel. Furthermore, the first transceiver provides information regarding the second radio channel in a second message so that the second transceiver can determine the second radio channel
A method of coordinating tuning for a transceiver is also disclosed. In an embodiment of the present invention, the method comprises determining a transmit radio channel in a radio band; transmitting a transmit control message at the transmit radio channel using the transceiver; searching for an ID in a receive control message over channels within the radio band to identify a receive radio channel using the transceiver; and receiving audio from a remote transceiver at the receive radio channel using the transceiver.
A wireless duplex audio device is also disclosed. According to one embodiment of the present invention, the device comprises a transmitter to transmit first audio and a first control message at a first radio channel in a radio band, wherein the first control message comprises identification associated with the transmitter; a receiver to receive second audio and a second control message at a second radio channel in the radio band; and a controller, wherein the controller includes a clear channel scan unit to determine the first radio channel; and wherein the controller includes a channel search unit to determine the second radio channel.
As described previously, it is possible to take advantage of low-power transmission in the broadcast band for personal wireless use. However, if a channel is randomly selected for transmission, the channel may be occupied by a broadcaster or another user. A technique, named Clear Channel Scan (CCS) is disclosed in U.S. Non-Provisional patent application Ser. No. 12/137,535, wherein the CCS technique allows a best un-occupied channel to be identified quickly. Therefore, a transmitter can use the CCS to identify an un-occupied channel and uses the identified channel to transmit audio and data. A receiver can be tuned to the identified channel to receive audio and data, and play the audio. To automate the channel tuning for the receiver, a handshaking method is disclosed in U.S. Non-Provisional patent application Ser. No. 12/172,147, which utilizes a sub-channel to transmit an identification code in the data channel so that the receiver can search for the channel that contains the pre-specified identification code. The handshaking technique has been applied to wireless earphone for auto-pairing so that a correct channel can be always identified adaptively. The U.S. Non-Provisional patent application Ser. No. 12/495,796 further extends the use of control message in the sub-channel for control of a remote receiver, such as channel switching. While a clear channel may be selected using the CCS technique, the channel quality may vary from time to time due to various reasons. When the channel quality degrades, the system should be able to detect the situation and react accordingly, such as determining and switching to a new clear channel.
In the present invention, a duplex air audio is disclosed which utilizes low-power transmission allowed for certain broadcast bands to achieve two-way audio communication between two devices. One such application is wireless speakerphone extension for cellphone for group voice conference or hand-free operation.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, an embodiment of the present invention discloses a wireless speakerphone system to include a pair of transceivers to establish a 2-way audio link between a portable device and a remote speakerphone. The wireless audio link may be based on the existing FM broadcast bands which are widely available worldwide. The pair of transceivers can be a pair of FM transceiver that transmit and receive audio in the main channel and transmit and receive data in the sub-channel. The sub-channel can be based on the radio data system (RDS or RDBS) adopted for North America. Other radio data standards are also used in other regions of the world and the present invention is not limited to any particular implementation of the radio data standard transmitted in the sub-channel.
At the wireless speakerphone side, the device comprises an FM transceiver 162, a transmit antenna 174 and a receive antenna 176. Two separate antennas 174 and 176 are used for illustration and, again the two antennas may be replaced with a single antenna. A microphone 178 is used to pick up voice at the remote side near the device and multiple microphones may be needed to accommodate a large group conference. A speaker 182 is used to provide sound with adequate volume for group conference. As is well known in the art that a microphone requires suitable audio input interface circuit to match the impedance, to amplify the signal to a proper level, and to convert the analog signal to a digital signal for subsequent processing. The interface circuit may be external to, embedded in, or partially embedded in the transceiver 162. In either case, the present invention can be practiced. As is also well known in the art that the speaker requires a proper audio output interface circuit to convert digital audio into analog audio, and to amplify the signal to a level adequate to drive the speaker. Again, the audio output interface circuit may be external to, embedded in, or partially embedded in the transceiver 162. In either case, the present invention can be practiced. Furthermore, the speaker output to the microphone input may create an unintended audio feedback loop that will cause echo. The wireless speakerphone device may comprise an optional echo cancellation unit, which is not shown in
The sub-system 250 on the left side of
In a duplex wireless audio system, both sides may use the same type of transceiver as shown in
A method of coordinating tuning for a transceiver is also disclosed as shown in
The invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described examples are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
Claims
1. A method of coordinating tuning for a transceiver, the method comprising:
- determining a transmit radio channel in a radio band;
- transmitting a transmit control message within the transmit radio channel using the transceiver;
- searching for an ID in a receive control message over channels within the radio band to identify a receive radio channel using the transceiver; and
- receiving first audio from a remote transceiver at the receive radio channel using the transceiver.
2. The method of claim 1, wherein said determining the transmit radio channel is based on a clear channel scan method.
3. The method of claim 2, wherein the clear channel scan method is started after a random delay.
4. The method of claim 1, wherein the radio band is an FM broadcast band.
5. The method of claim 4, wherein the transmit control message is transmitted in a transmit sub-channel associated with the transmit radio channel.
6. The method of claim 4, further comprising transmitting second audio in the transmit radio channel using the transceiver.
7. The method of claim 4, wherein the receive control message is transmitted in a receive sub-channel associated with the receive radio channel.
8. The method of claim 1 further comprising:
- evaluating channel quality of the receive radio channel using the transceiver; and
- transmitting a new control message related to the quality of the receive radio channel using the transceiver.
9. An apparatus of coordinating tuning for a transceiver, the apparatus comprising:
- means for determining a transmit radio channel in a radio band;
- means for transmitting a transmit control message within the transmit radio channel using the transceiver;
- means for searching for an ID in a receive control message over channels within the radio band to identify a receive radio channel using the transceiver; and
- means for receiving first audio from a remote transceiver at the receive radio channel using the transceiver.
10. The apparatus of claim 9, wherein said means for determining the transmit radio channel is based on a clear channel scan apparatus.
11. The apparatus of claim 10, wherein the clear channel scan apparatus is started after a random delay.
12. The apparatus of claim 9, wherein the radio band is an FM broadcast band.
13. The apparatus of claim 12, wherein the transmit control message is transmitted in a transmit sub-channel associated with the transmit radio channel.
14. The apparatus of claim 12, further comprising means for transmitting second audio in the transmit radio channel using the transceiver.
15. The apparatus of claim 12, wherein the receive control message is transmitted in a receive sub-channel associated with the receive radio channel.
16. The apparatus of claim 9, further comprising:
- means for evaluating channel quality of the receive radio channel using the transceiver; and
- means for transmitting a new control message related to the quality of the receive radio channel using the transceiver.
Type: Application
Filed: Feb 26, 2013
Publication Date: Jul 4, 2013
Applicant: QUINTIC HOLDINGS (Santa Clara, CA)
Inventor: QUINTIC HOLDINGS (Santa Clara, CA)
Application Number: 13/777,415