Abstract:
The present invention discloses a communication system to facilitate natural multiparty conversation in a noisy environment. The communication system may include a wireless headset. Each headset is connected to a wireless hub. In one embodiment, one of the headsets is integrated with the hub. Each participant in the conversation may wear the wireless headset. The speech from each non-hub headset is wirelessly communicated to the hub. The hub combines the speech from each participant into a conversation stream and transmits the conversation stream to all participants.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to technology for wireless communication and, in particular, to wireless technology for voice communication in a noisy environment. 
         [0003]    2. Description of Related Art 
         [0004]    People frequently carry on conversation in a noisy environment, such as diners conversing around a table at a noisy restaurant, first responders communicating in an emergency situation, friends talking in a public place, etc. Because people may have trouble hearing each other, one may have to shout to be heard. Even with shouting, however, it may be difficult for all of the interested party to hear or to participate in a single conversation. 
         [0005]    Communication systems have been developed to facilitate conversation in noisy conditions. For example, helmet mounted systems allow motorcycle riders, constructions workers, and first responders to converse with one another. However, none of these systems provides the combination of features required for carrying on natural conversation in a noisy environment. These requirements may include low-latency (&lt;45 milliseconds), wide audio bandwidth (50-7500 Hz), high dynamic range, full-duplex communication, noise and echo reduction, speech enhancement, non-directional link, non-mouth blocking, long battery life, and multi-party operation. 
         [0006]    Latency is the time interval between when a participant in a conversation utters a sound and when that sound is heard by all participants. Latency is not a significant issue for helmet mounted systems since the participants arc not looking at each other&#39;s lips while communicating. However, it is a significant issue for enhanced conversation systems where participants may be sitting around a dinner table. In fact, latency exceeding 45 milliseconds will be perceived as loss of sync between speech and mouth movement. 
         [0007]    In addition, existing systems provide, at best, telephone equivalent audio bandwidths of 300-3400 Hz and dynamic ranges of 40 to 50 dB. This is adequate for remote communication, as evidenced by telephone usage, but does not provide the sense and feel of natural face-to-face conversation. It is well known that 100% intelligibility requires 5,000 Hz of audio bandwidth. The human voice has frequencies from 80 Hz to 10,000 Hz. The 300-3400 Hz bandwidth offered by existing systems loses two octaves on bass and two on treble. This loss of bandwidth produces a voice that is decidedly metallic. A wider, 50-7500 Hz, bandwidth is required for natural sounding conversation. Also, the normal human ear operates with 90 dB of dynamic range. Natural sounding conversation requires a 60 to 70 dB dynamic range, about 20 dB more than that of the existing system. 
         [0008]    Furthermore, some existing systems are simplex (similar to push-to-talk radios); some do not provide noise and echo reduction or speech enhancement processing; others require that one participant face another participant, or point a microphone at another participant, to hear what that participant is saying. These shortcomings prevent natural multiparty conversations. For natural sounding conversation, full-duplex communication, noise and echo reduction, and speech enhancement are desired. Helmet mounted systems also inherently interfere with eating. Non-mouth blocking is a requirement for enhanced conversation systems where the participants may be sitting around a dinner table. 
         [0009]    Therefore, it is desirable to provide an improved communication system to facilitate natural multiparty conversation in a noisy environment. 
       SUMMARY OF THE INVENTION 
       [0010]    An objective of the present invention is to provide a wireless headset. Each headset is connected to a wireless hub. In one embodiment, one of the headsets is integrated with the hub. Each participant in the conversation may wear the wireless headset. The hub combines the speech from each participant and transmits the speech to all participants. 
         [0011]    Disclosed is a method for enhancing conversation between participants. In one embodiment of the present invention, the method includes capturing the speech of one of the participants by a microphone of a wireless headset. The method also includes wirelessly transmitting the captured speech to a hub. The method further includes wirelessly receiving a conversation stream from the hub. The conversation stream is a combination of speeches from all the participants. The method further includes radiating the conversation stream from a headphone of the wireless headset to the one participant. 
         [0012]    In one embodiment of the present invention, the method includes wirelessly receiving speech samples of one or more remote participants by a hub. The method also includes receiving speech samples of a local participant from a headset, if any, that is integrated with the hub. The method further includes combining the speech samples from all the participants into a conversation stream. The method further includes wirelessly transmitting the conversation stream the hub to the one or more remote participants. 
         [0013]    Disclosed is an apparatus used in wireless communication to enhance conversation between participants. In one embodiment of the present invention, the apparatus includes a microphone used to receive the speech of a user. The apparatus also includes a sampling circuit used to convert the speech into speech samples. The apparatus further includes a processor used to encode and modulate the speech samples. The processor is further used to demodulate and decode a conversation stream received from a hub. The conversation stream is a combination of speech samples from multiple users. The apparatus further includes a transceiver used to transmit the speech samples to the hub. The transceiver is also used to receive the conversation stream from the hub in full duplex. The apparatus further includes a headphone used to radiate the conversation stream to the user. 
         [0014]    In one embodiment of the present invention, the apparatus includes a transceiver used to receive speech samples from one or more headsets. The transceiver is also used to transmit a conversation stream in full duplex to the one or more headsets. The apparatus also includes a processor used to demodulate and decode the speech samples from the one or more headsets. The processor is also used to combine the demodulated and decoded speech samples from all the headsets in combined samples. The processor is further used to encode and to modulate the combined samples into the conversation stream. 
         [0015]    Advantageously, participants wearing a headset may carry on natural multiparty conversation in a noisy environment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The accompanying drawings are provided together with the following description of the embodiments for a better comprehension of the present invention The drawings and the embodiments are illustrative of the present invention, and are not intended to limit the scope of the present invention. It is understood that a person of ordinary skill in the art may modify the drawings to generate drawings of other embodiments that would still fall within the scope of the present invention. 
           [0017]      FIG. 1  illustrates participants using the headsets of the enhanced conversation system to converse with one another through a stand-alone hub according to one or more embodiments of the present invention; 
           [0018]      FIG. 2  illustrates participants using the headsets of the enhanced conversation system to converse with one another through a hub that is integrated with one of the headsets according to one or more embodiments of the present invention; 
           [0019]      FIG. 3  shows a top level block diagram of an enhanced conversation system with a stand-alone hub according to one or more embodiments of the present invention; 
           [0020]      FIG. 4  shows a top level block diagram of an enhanced conversation system with a hub that is integrated into a headset according to one or more embodiments of the present invention; 
           [0021]      FIG. 5  shows the audio flow in an enhanced conversation system according to one or more embodiments of the present invention; 
           [0022]      FIG. 6  shows a top level block diagram of the wireless headset of the enhanced conversation system of  FIG. 1  according to one or more embodiments of the present invention; 
           [0023]      FIG. 7  shows a block diagram of the data processing of the FPGA of the non-hub headset of  FIG. 6  according to one or more embodiments of the present invention; 
           [0024]      FIG. 8  shows the timing of the wireless link of the enhanced conversation system according to one or more embodiments of the present invention; 
           [0025]      FIG. 9  shows a top level block diagram of the standalone hub of the enhanced conversation system according to one or more embodiments of the present invention; 
           [0026]      FIG. 10  shows a block diagram of the data processing of the FPGA of the hub of  FIG. 9  according to one or more embodiments of the present invention; and 
           [0027]      FIG. 11  shows a block diagram of the data processing of the FPGA of the hub headset of  FIG. 6  according to one or more embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    The following paragraphs describe several embodiments of the present invention in conjunction with the accompanying drawings. Like reference numerals are used to identify like elements in one or more of the drawings. It should be understood that the embodiments are used only to illustrate and describe the present invention, and are not to be interpreted as limiting the scope of the present invention. 
         [0029]      FIG. 1  illustrates participants using the headsets of the enhanced conversation system to converse with one another through a stand-alone hub according to one or more embodiments of the present invention. Participants  12  are seated around a table  10  conversing in a noisy environment  11 . Each participant  12  wears a headset  14  incorporating an earpiece for radiating sound into the ear of that participant  12  and a microphone for capturing the speech of that participant  12 . In one or more embodiments of the present invention, the microphone has noise-cancellation, noise-reduction, and/or echo-cancellation capability. Headset  14  processes the captured speech into audio signals. A wireless transceiver in headset  14  uses a wireless links  18  to transmit the audio signals of the speech of participant  12  to a hub  16 . Wireless link  18  may be shared by multiple headsets  14  using one of several multiple access schemes to transmit audio signals from participants  12  in a multi-party conversation. 
         [0030]    A wireless transceiver in the hub  16  receives the audio streams from the multiple headsets  14 . Hub  16  uses digital signal processing to process and combine the multiple audio streams into a single conversation stream. Hub  16  may have noise-cancellation, noise-reduction, echo-cancellation, and/or speech enhancement capability. The wireless transceiver in hub  16  uses wireless link  18  to transmit the conversation stream back to each headset  14 . Hub  16  shares wireless link  18  with headsets  14  in full duplex operation. The wireless transceiver in headset  14  receives the conversation stream from hub  16 . Headset  14  processes and radiates the conversation steam to each participant  12  through the earpiece. 
         [0031]      FIG. 2  illustrates participants using the headsets of the enhanced conversation system to converse with one another through a hub that is integrated with one of the headsets according to one or more embodiments of the present invention. Participants  22  are seated around a table  20  conversing in a noisy environment  21 . One of the participants  22  wears a hub headset  24 . Each of the other participants  22  wears a non-hub headset  26 . Hub headset  24  and non-hub headset  26  each provides an earpiece for radiating sound into the ear of that participant  22  and a microphone for capturing the speech of that participant  22 . In one or more embodiments of the present invention, the microphone has noise-cancellation, noise-reduction, and/or echo-cancellation capability when processing the speech into audio signals. A wireless transceiver in each non-hub headset  26  sends the audio signals captured by its microphone to hub headset  24  using a wireless link  28 . Wireless link  28  may be shared by multiple non-hub headsets  26  using one of several multiple access schemes to transmit audio signals from participants  22  in a multi-party conversation. 
         [0032]    A wireless transceiver in the hub headset  24  receives the audio streams from multiple non-hub headsets  26 . Hub headset  24  incorporates digital signal processing to process and combine the multiple audio streams, including the one from its own microphone, into a conversation stream. Hub headset  24  may have noise-cancellation, noise-reduction, echo-cancellation, and/or speech enhancement capability. The wireless transceiver in hub headset  24  uses wireless link  28  to transmit the conversation stream back to each non-hub headset  26 . Hub headset  24  shares wireless link  28  with non-hub headsets  26  in full duplex communication. The wireless transceiver in non-hub headset  26  receives the conversation stream from hub headset  24 . Non-hub headset  26  processes and radiates the conversation steam to each participant  22  wearing non-hub headset  26  through the earpiece. Hub headset  24  also radiates the conversation stream to participant  22  wearing hub headset  24 . 
         [0033]    One or more embodiments of the present invention use Bluetooth wireless links to connect the headsets in a piconet. A piconet consists of two or more devices occupying the same physical channel (synchronized to a common clock and hopping sequence). A Bluetooth piconet may have a master device. The common (piconet) clock is identical to the clock of the master device in the Bluetooth piconet and the hopping sequence is derived from the clock and the Bluetooth device address of the master device. All other synchronized devices are slaves in the Bluetooth piconet. 
         [0034]    Bluetooth enabled devices use an inquiry procedure to discover nearby devices, or to be discovered by devices in their locality. The inquiry procedure is asymmetrical. A Bluetooth enabled device trying to find other nearby devices is known as an inquiring device. The inquiring device actively sends inquiry requests to discover nearby devices. Bluetooth enabled devices available to be found by the inquiring device are “discoverable” they listen for inquiry requests and send responses back to the inquiring device. 
         [0035]    Once an inquiring device discovers other nearby Bluetooth enabled devices, connections may be formed between the devices. The procedure for forming connections is asymmetrical and requires that one Bluetooth enabled device carry out the page (connection) procedure while the other Bluetooth enabled device is connectable (page scanning). The procedure is targeted, so the page procedure from the paging (connecting) device is only responded to by one specified Bluetooth enabled device, called the connectable device. The connectable device uses a special physical channel to listen for connection request packets from the paging device. This physical channel has attributes specific to the connectable device, hence only a paging device with knowledge of the connectable device is able to communicate on this channel. 
         [0036]    In one or more embodiments of the present invention, the Bluetooth wireless links may be replaced with other low-latency full-duplex links such as Wi-Fi wireless links, other standardized wireless links, non-standard wireless links, or free-space optical links. 
         [0037]      FIG. 3  shows a top level block diagram of an enhanced conversation system with a stand-alone hub according to one or more embodiments of the present invention. Devices of the enhanced conversation system are linked via a Bluetooth piconet. A hub  30  is the master of the Bluetooth piconet. Headsets  32  are slaves of that piconet. Hub  30  and headsets  32  may discover each other and form connections between them using the inquiry procedure and the page procedure as described. Each headset  32  is worn by one of the participants in the conversation, and provides an earpiece for radiating sound into the ear of that participant and a microphone for capturing the speech of that participant. Headset  32  processes the speech captured by the microphone into audio signals. A Bluetooth transceiver in headset  32  sends the audio signals to hub  30  using a Bluetooth link  34 . 
         [0038]    A Bluetooth transceiver in hub  30  receives the audio streams from the multiple headsets  32 . Hub  30  incorporates digital signal processing to process and combine the multiple audio streams into a conversation stream. The Bluetooth transceiver in hub  30  transmits the conversation stream to the multiple headsets  32  using Bluetooth link  34 . The Bluetooth transceiver in headset  32  receives the conversation stream from hub  30 . Headset  32  processes the conversation stream and radiates the processed conversation stream through its earpiece to the participant. Physical channels in Bluetooth link  34  may be shared by multiple headsets  32  and hub  30  using one of several multiple-access schemes, such as time division multiple access (TDMA), frequency division multiple access (FDMA), code division multiple access (CDMA), or others. In one or more embodiments of the present invention, hub  30  may be replaced by Bluetooth enabled devices including smartphones, tablets, laptops, or other portable or mobile communication/computing devices. In one or more embodiments of the present invention, Bluetooth link  34  may be replaced by other low-latency full-duplex links such as Wi-Fi wireless links, other standardized wireless links, non-standard wireless links, or free-space optical links. 
         [0039]      FIG. 4  shows a top level block diagram of an enhanced conversation system with a hub that is integrated into a headset according to one or more embodiments of the present invention. Devices of the enhanced conversation system are linked via a Bluetooth piconet. One of the headsets is a hub headset  40  and is also the master of the Bluetooth piconet. The remaining headsets are non-hub headsets  42  and are slaves of the Bluetooth piconet. Hub headset  40  and each of the non-hub headsets  42  are worn by the participants in the conversation, with each headset providing an earpiece for radiating sound into the ear of that participant and a microphone for capturing the speech of that participant. Hub headset  40  and non-hub headset  42  each processes the speech captured by its microphone into audio signals. A Bluetooth transceiver in each of the non-hub headsets  42  sends the audio signals to hub headset  40  using a Bluetooth link  44 . 
         [0040]    A Bluetooth transceiver in hub headset  40  receives the audio streams from the multiple non-hub headsets  42 . Hub headset  40  incorporates digital signal processing to process and combine the multiple audio streams, including the one from its own microphone, into a conversation stream. The Bluetooth transceiver in hub headset  40  transmits the conversation stream to the multiple non-hub headsets  42  using Bluetooth link  44 . The Bluetooth transceiver in non-hub headset  42  receives the conversation stream from hub headset  40 . Non-hub headset  42  processes the conversation stream and radiates the processed conversation stream through its earpiece to the participant. The conversation stream from hub headset  40  is also radiated by the earpiece of hub headset  40 . Physical channels in Bluetooth link  44  may be shared by multiple non-hub headsets  42  and hub headset  40  using one of several multiple access schemes. In one or more embodiments of the present invention, Bluetooth link  34  may be replaced by other low-latency full-duplex links. 
         [0041]      FIG. 5  shows the audio flow in an enhanced conversation system according to one or more embodiments of the present invention. The speech from each participant  500  is captured by a headset microphone  502 . Headset microphone  502  converts the free-space propagated audible speech into an electrical signal. The electrical signal is sampled and digitized. The digitized samples are encoded and sent to a headset transmitter  504 . Headset transmitter  504  converts the encoded samples into a wireless signal and transmits it through a wireless link. The transmitted wireless signal is received by a hub receiver  506 . Hub receiver  506  converts and decodes the free space propagated wireless signal into samples of the audible speech from participant  500 . A hub DSP  508  processes and combines the speech samples recovered from each of the participants  500 . The samples from the combined conversation stream are encoded and converted into a wireless signal by a hub transmitter  510 . Hub transmitter  510  transmits the wireless signal representing the combined conversation stream through the wireless link back to a handset receiver  512 . Handset receiver  512  converts and decodes the free-space propagated wireless signal into samples of the combined conversation stream. These samples are converted into audio signals by a headset earpiece  514 . Headset earpiece  514  provides the audio signals representing the combined conversation stream to participant  500 . 
         [0042]    Hub DSP  508  may process the audio streams received from each headset transmitter  504  to reduce noise and reduce echoes. After echoes and noise have been reduced in each of the individual audio streams, they are combined in a single conversation stream. Hub DSP  508  may further process the conversation stream to enhance speech. One of ordinary skill of the art will recognize that the processing steps may be performed in different orders and that not all of the steps are necessary. Also, one skilled in the art will recognize that the processing may be partitioned between the hub and the wireless headsets in various ways. 
         [0043]    One or more embodiments of the present invention may incorporate echo cancelling in hub DSP  508 . Echo cancellers operate by synthesizing an estimate of the echo from the participant&#39;s speech stream, and subtracting that synthesis from the conversation stream. This technique uses adaptive signal processing to generate a signal accurate enough to effectively cancel the echo, where the echo can differ from the original due to various kinds of degradation along the path from a participant&#39;s microphone to the conversation stream corning out of that participant&#39;s headphones. 
         [0044]    One or more embodiments of the present invention may incorporate speech enhancement in hub DSP  508 . Speech enhancement consists of temporal and spectral methods to improve the signal to noise ratio of a speech signal. 
         [0045]    One or more embodiments of the present invention may incorporate a noise cancelling microphone in the wireless headsets. These microphones may have two ports through which sound enters; one port oriented toward the participant&#39;s mouth and one orientated in another direction. The microphone&#39;s diaphragm is placed between the two ports; sound arriving from an ambient sound field reaches both ports more or less equally. Participant&#39;s speech will make more of a pressure gradient between the front and back of the diaphragm, causing it to move more. The microphone&#39;s proximity effect is adjusted so that flat frequency response is achieved for the participant&#39;s speech. Sounds arriving from other angles are subject to steep midrange and bass roll-off. 
         [0046]    In one or more embodiments of the present invention, noise cancelling microphones using two or more microphones and active or passive circuitry may be used to reduce the noise. The primary microphone is closer to the participant&#39;s mouth. A second microphone receives ambient noise. In a noisy environment, both microphones receive noise at a similar level, but the primary microphone receives the participant&#39;s speech more strongly. Thus if one signal is subtracted from the other (in the simplest sense, by connecting the microphones out of phase), much of the noise may be canceled while the desired sound is retained. 
         [0047]    The internal electronic circuitry of a noise-canceling microphone may attempt to subtract the noise signal from the primary microphone. The circuitry may employ passive or active noise canceling techniques to filter out the noise, producing an output signal that has a lower noise floor and a higher signal-to-noise ratio. 
         [0048]    One or more embodiments of the present invention may incorporate noise cancelling headphones in the wireless headset. The materials of the headphones may provide some passive noise blocking. Active noise-cancellation techniques may be used to erase lower-frequency sound waves. A microphone placed inside the ear cup may “listen” to external sounds that remain after passive blocking. Electronic circuits sense the input from the microphone and generate a wave that is  180  degrees out of phase with the waves associated with the noise. This “anti-sound” is input to the headphones&#39; speakers along with the conversation audio; the anti-sound reduces the noise by destructive interference, but does not affect the desired sound waves in the conversation audio. 
         [0049]      FIG. 6  shows atop level block diagram of the wireless headset of the enhanced conversation system of  FIG. 1  according to one or more embodiments of the present invention. The participant&#39;s speech is received by a noise canceling microphone  600 . Output from noise canceling microphone is amplified by an amplifier  602  to set the noise floor. A bandpass filter (BPF)  604  with a pass band of 50 Hz to 7500 Hz filters the output from amplifier  602  to attenuate out-of-band noise. The bandpass filtered speech signal is digitized by a 12-bit AID  606  at 16 kHz. The 12-bit quantization provides approximately 76 dB dynamic range and the 16 kHz sampling rate mitigates aliasing of the band-limited speech signal. The quantized speech samples are input to afield programmable gate array (FPGA)  608  where they are partitioned into 10 millisecond frames, each frame comprising 160 samples, or 1920 bits. The 1920 bits are rate-1/2 coded for error protection into a 3820 bit packet. The packets are then QPSK modulated at 1.92 Mbaud to form a 1 millisecond baseband burst. The baseband burst timing is then adjusted to a designated slot  82  in a 10 millisecond frame  80  of  FIG. 8 , and input to an RF transceiver  610  which up-converts the baseband burst to the RF transmission frequency and outputs it to an antenna  620 . Antenna  620  transmits the burst RF transmission through the wireless link to hub  16 . In one or more embodiments of the present invention, FPGA  608  may be implemented by other programmable logic arrays (PLAs), an application specific integrated circuit (ASIC), a digital signal processor (DSP), or software/firmware running on a processor. 
         [0050]    Antenna  620  also receives the burst transmissions from hub  16  and inputs them to RF transceiver  610 . RF transceiver  610  down-converts the received bursts to baseband signals and outputs them to FPGA  608 . FPGA  608  demodulates the baseband signal, decodes it, selects the 1 millisecond burst  84  from hub  16  (shown in  FIG. 8 ), and outputs the 12-bit samples at 16 kHz to a D/A  612 . D/A  612  converts the digitized samples to an analog voltage and outputs it to a BPF  614  which has a 50 Hz to 7500 Hz bandwidth and is used to reconstruct the conversation stream from hub  16 . The reconstructed conversation stream is input to an amplifier  616 . The amplified conversation stream is input to a noise cancelling headphone  618  which radiates it into the ear of participant  12 . 
         [0051]      FIG. 6  may also represent a top level block diagram of the hub headset  24  of the enhanced conversation system of  FIG. 2  according to one or more embodiments of the present invention. Speech from a hub headset-wearing participant  22  is received by noise canceling microphone  600 , amplified by amplifier  602 , filtered by bandpass filter (BFP)  604 , and digitized by 12-bit A/D  606  at 16 KHz. The quantized speech samples are input to FPGA  608  and partitioned into 10 millisecond frames of 160 samples, or 1920 bits. 
         [0052]    Antenna  620  receives the burst transmissions from non-hub headsets  26  during their assigned slots as shown in the frame structure of  FIG. 8  and inputs them to RF transceiver  610 . RF transceiver  610  down-converts the received bursts to baseband signals and outputs them to FPGA  608 . FPGA  608  demodulates the baseband signals for each non-hub headset  26 , decodes it, and may perform echo and/or noise canceling to generate a 1920 bit packet representing 10 milliseconds of speech samples for each non-hub headset  26 . The 1920 bit packets for all of non-hub headsets  26  and the 1920 bit packet for hub headset  24  are combined to generate the conversation stream. The conversation stream may be processed to enhance speech. FPGA  608  outputs the conversation stream as 12-bit samples at 16 KHz to D/A  612 . D/A  612  converts the digitized samples to an analog voltage and outputs it to BPF  614  for baseband filtering. The baseband filtered conversation stream is amplified by amplifier  616  and output to noise canceling headphone  618  which radiates it into the ear of participant  22  wearing hub headset  24 . 
         [0053]    The conversation stream is also rate-1/2 coded for error protection into a 3820 bit packet. The packet is then QPSK modulated at 1.92 Mbaud to form a 1 millisecond baseband burst. The baseband burst is allocated to the designated slot  84  for the hub in the 10 millisecond frame  80  of  FIG. 8 , and input to RF transceiver  610  which up-converts the baseband burst to the RF transmission frequency and outputs it to antenna  620 . Antenna  620  transmits the burst RF transmission of the conversation stream through the wireless link to non-hub headsets  26 . 
         [0054]      FIG. 7  shows a block diagram of the data processing of the FPGA  608  of the non-hub headset of  FIG. 6  according to one or more embodiments of the present invention. The quantized speech from the non-hub headset represented as 12-bit data samples at 16 KHz are encoded by an encoder  701  for error protection. For example, encoder  701  may be a rate-1/2 encoder that encodes each 12-bit data sample into 24 bits. The encoded data are modulated by a modulator  703 . For example, modulator  703  may be a QPSK modulator that modulates each 24-bit encoded data sample into 12 QPSK symbols. The modulated symbols are partitioned into data frames, buffered, and burst out at a faster rate to enable time division multiplexing of the modulated speech samples from multiple headsets over the wireless link. For example, a Tx burst buffer  705  may partition the QPSK-modulated data into a 10 millisecond packet of 1920 symbols. The 1920 symbols are buffered and burst out at 1.92 Mbaud to form a 1 millisecond baseband burst. The 1 millisecond baseband burst is allocated to a designated slot  82  for the headset in the 10 millisecond frame  80  of  FIG. 8 , up-converted to RF transmission frequency, and transmitted over the wireless link to hub  16 . 
         [0055]    Burst transmission of the conversation stream received from hub  16  during designated hub slot  84  of the 10 millisecond frame  80  is down-converted to baseband signals and buffered by an Rx burst buffer  707 . The 1 millisecond burst of conversation stream representing 1920 QPSK symbols of data is read out of Rx burst buffer  707  over the 10 millisecond duration of the frame. The 1920 QPSK symbols are demodulated by a demodulator  702  to 3840 bits and decoded by a rate-1/2 decoder  711  to recover the 1920-bit packet of the conversation stream. The conversation stream is output as 12-bit samples at 16 KHz over the 10 millisecond frame and converted to analog voltage waveforms for radiating to the earphone of the headset. 
         [0056]    To synchronize the non-hub headset with the frame timing, a synchronization prefix demodulator  713  demodulates the synchronization prefix symbols received at the beginning of designated hub slot  84  of the 10 millisecond frame. When synchronization prefix demodulator  713  detects the synchronization prefix, a timing synchronizer  715  synchronizes a frame timer to the beginning of designated hub slot  84 . The frame timer keeps track of the frame timing and generates timing signals to Tx burst buffer  705  to burst out the 1 millisecond packet from the headset at the allocated slot  82 . The frame timer also generates timing signals to Rx burst buffer  707  to receive the 1 millisecond packet of conversation stream from hub  16  during designated hub slot  84 . 
         [0057]      FIG. 8  shows the timing of the wireless link of the enhanced conversation system according to one or more embodiments of the present invention. A TDMA architecture is used with frames  80  of 10 millisecond duration. Each frame is divided into nine burst time slots. The 1.1 millisecond time slot HUB  84  is used by hub  16  to transmit the conversation stream and timing synchronization. The remaining eight 1 millisecond burst time slots  82  are used by each of the up to eight participants  12  in the conversation. Each of the time slots are separated by a 0.1 milliseconds guard time. The participant speech  12  captured during a 10 millisecond frame  80  is transmitted to the hub  16  during the next 10 millisecond frame  80 , and processed into the conversation stream by the hub  16  during the first part of the next 10 millisecond frame. The conversation stream is transmitted to the participant  12  headsets during HUB  84  burst of the third frame, and heard by the participants during the next 10 millisecond frame. This combination provides a 30 millisecond latency. 
         [0058]      FIG. 9  shows a top level block diagram of the stand-alone hub  16  of the enhanced conversation system according to one or more embodiments of the present invention. An antenna  920  receives the burst transmissions from headsets  14  of participants  12  and inputs them to an RF transceiver  910 . RF transceiver  910  down-converts the received bursts to baseband signals and outputs them to an FPGA  908 . FPGA  908  demodulates the baseband signal, decodes it, and selects the up to eight 1 millisecond bursts  82  from each participant  12 . 
         [0059]    FPGA  908  processes the received audio streams to reduce noise and reduce echoes. After echoes and noise have been reduced in each of the individual audio streams, they are combined in a single conversation stream. The conversation stream may be processed to enhance speech. The conversation stream bits are rate-1/2 coded for error protection into a 3820 bit packet. The packets are then QPSK modulated at 1.92 Mbaud and prefixed with a 191 bit BPSK modulated PN sequence for timing synchronization to form a 1.1 millisecond baseband burst. The baseband burst timing is then adjusted to HUB slot  84  in the 10 millisecond frame  80  and input to RF transceiver  910  which up-converts the baseband burst to the RF transmission frequency and outputs it to antenna  920 . 
         [0060]      FIG. 10  shows a block diagram of the data processing of FPGA  908  of the stand-alone hub of  FIG. 9  according to one or more embodiments of the present invention. The quantized speech from headsets  14  are received during slots  82  of the frame by an Rx frame buffer  1001 . The 1 millisecond burst of quantized samples from each handset  14  representing 1920 QPSK symbols are demodulated by a demodulator  1003  to 3840 bits and decoded by a rate-1/2 decoder  1005  to recover the 1920-bit packet. The 1920-bit packet is processed by a noise/echo reduction block  1007  for noise or echo reduction. The 1920-bit packets from multiple headsets are combined by a stream combiner  1009  into a conversation stream. The conversation stream may be processed to enhance speech. The 1920-bit packet of the conversation stream is rate-1/2 coded by an encoder  1011  for error protection into a 3820 bit packet. The packet is then QPSK modulated by a modulator  1013  into 1910 symbols. The modulated symbols are received by a hub slot burst buffer  1015  and burst out at 1.92 Mbaud. 
         [0061]    The conversation stream packet is prefixed with a 191 bit BPSK modulated PN sequence from a synchronization prefix modulator  1017  for timing synchronization to form a 1.1 millisecond baseband burst. The baseband burst is then allocated to HUB slot  84  in the 10 millisecond frame  80 , up-converted to RF transmission frequency, and transmitted over the wireless link to headsets  14 . A frame timer  1019  keeps track of the frame timing and generates timing signals to Rx frame buffer  1001  to receive the 1 millisecond packets of speech samples from headsets  14  during designated slots  82 . Frame timer  1019  also generates timing signals to hub slot burst buffer  1013  to transmit the 1 millisecond packet of conversation stream from hub  16  during designated hub slot  84  of the frame. 
         [0062]      FIG. 11  shows a block diagram of the data processing of FPGA  608  of the hub headset of  FIG. 6  according to one or more embodiments of the present invention. The data processing in  FIG. 11  is similar to the data processing of FPGA  908  of the stand-alone hub described in  FIG. 10  and will not be described. One difference in data processing from that performed by the stand-alone hub is that the 1920-bit packet of quantized speech samples from the hub headset is combined with the 1920-bit packets from multiple headsets by stream combiner  1009  into the conversation stream. The conversation stream is also converted to analog voltage, filtered, amplified, and radiated to the earphone of the hub headset. 
         [0063]    The descriptions set forth above are provided to illustrate one or more embodiments of the present invention and are not intended to limit the scope of the present invention. Although the invention is described in details with reference to the embodiments, a person skilled in the art may obtain other embodiments of the invention through modification of the disclosed embodiment or replacement of equivalent parts. It is understood that any modification, replacement of equivalent parts and improvement are within the scope of the present invention and do not depart from the spirit and principle of the invention as hereinafter claimed.