METHOD AND APPARATUS FOR SUPPORTING NON-VOICE SIGNAL SUCH AS FASCIMILE AND COMPRESSED VOICE OVER A DIGITAL WIRELESS LINK

Abstract: An end-to-end system for transmitting and receiving non-voice data such as, for example, facsimile and voice data over a wireless link. The end-to-end system comprises a first station and a second station. The first station processes facsimile data and voice data for transmission over the wireless link. As the facsimile and data signals have different transmission rate and bandwidth requirements, the first station segments or splits facsimile data, such that facsimile and voice data are properly multiplexed over the wireless link without distortion. The second station may adapt with the first station for receiving and transmitting facsimile and voice data via the wireless link.

Description: METHOD AND APPARATUS FOR SUPPORTING NON-VOICE SIGNAL SUCH AS FACSIMILE AND COMPRESSED VOICE OVER A DIGITAL WIRELESS LINK FIELD OF THE INVENTION The present invention generally relates to data transmission systems. More particularly, the invention relates to a method and apparatus for sending voice data such as, for example, facsimile and compressed voice signals over a digital wireless link. BACKGROUND OF THE INVENTION There are many types of data communication systems in the art for transmitting facsimile, audio, video and data signals. In addition, cordless telephone systems have become enormously popular, offering flexibility and convenience unequaled by traditional corded telephone systems. Cordless telephone systems use digital signal processing for processing voice signals prior to transmission. Once the voice signal is digitized, a cordless telephone system compresses the digitized voice signal using a voice compression algorithm or technique that is based on a speech model. To conserve bandwidth over the digital wireless link (or RF link) and maintain a reasonable speech quality, the compression algorithm operates at compression ratios between two and ten. As cordless telephone systems are enormously popular, it is desirable to incorporate additional features in these systems, such as coupling facsimile machines to a cordless handset or producing a cordless facsimile machine. However, facsimile machines do not process data using a speech model as is used in cordless telephone systems. If a speech model that is applied to the voice compression algorithm used in existing cordless telephone systems were to be applied to facsimile data, the facsimile data would become distorted. Data communications systems that combine voice and data, such as facsimile, are known in the art. Davis et al, in U.S. Patent No. 5,764,628 and Davis et al, in U.S. Patent No. 5,81 2,534 are two examples of such systems. However, these systems require dedicated lines or channels to separately transmit voice and facsimile data and are not applicable to cordless telephone systems. Therefore, a need exists in the art for combining the wireless transmission of non-voice data such as facsimile signals with the wireless transmission of compressed voice signals in cordless telephone systems. SUMMARY OF THE INVENTION The invention overcomes the disadvantages associated with the prior art by providing a method and apparatus for transmitting non-voice data such as facsimile signals over the same wireless or radio frequency (RF) link used for transmitting compressed voice signals. The invention segments a facsimile signal into a format that is similar to a compressed voice signal. The segmented portions of the facsimile signal are separately transmitted through the wireless link. As such, the invention may transmit facsimile and/or compressed voice signals over a wireless link without distortion. Specifically, the inventive apparatus comprises a base station and a remote station. The base station comprises a signal converter for converting facsimile and compressed voice signals from a telephone network respectively into a converted facsimile signal and a converted voice signal, a voice processor coupled to the signal converter for compressing the converted voice signal, a data splitter coupled to the signal converter for segmenting the converted facsimile signal, and a modem coupled to the voice compressor and the data splitter for transmitting the converted voice and facsimile signals via a wireless link to the remote station. The remote station receives these signals from the base station, and converts voice and facsimile signals in a reverse manner to that of the base station, i.e., the segmented facsimile signals are combined into a digital facsimile signal, the digital facsimile signal and the compressed voice signal are processed to form analog voice and facsimile signals. As such, the remote station may be or may contain a wireless facsimile machine and/or a cordless telephone handset having a facsimile machine connected thereto. The base station and remote station contain complementary circuitry that provides full duplex facsimile and voice communications over the wireless link. BRIEF DESCRIPTION OF THE DRAWINGS The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which: FIG. 1 depicts a system level block diagram of an end-to-end system comprising a base station and a receiving station; FIG. 2 depicts a high level block diagram of a base station adapted to communicate with an analog telephone network; FIG. 3 depicts a high level block diagram of a base station adapted to communicate with a digital telephone network; FIG. 4 depicts a high level block diagram of a remote station suitable for use with either of the base stations of FIG. 2 and FIG. 3; and FIG. 5 depicts a high level block diagram of a base station adapted to communicate with a digital telephone network using a single voice compression/decompression technique. To facilitate understanding of the invention, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. DETAILED DESCRIPTION FIG. 1 depicts a system level block diagram of an end-to-end system 100 for providing facsimile transmission and compressed voice transmissions through a wireless link. The end-to-end system 100 comprises a base station 200 and the remote station 400 that communicate with one another in a full duplex manner. The base station 200 receives facsimile or voice signals from, illustratively, a Plain Old Telephone System (POTS) 50 and processes the facsimile or voice signal for transmission to the wireless link via an antenna 201 . The remote station 400 receives the transmitted facsimile or voice signal via an antenna 401 . To receive facsimile output at the remote station 400, a facsimile device 1 02 or facsimile machine is coupled to the remote station 400. Additionally, to receive a voice transmission at the remote station 400, a telephone handset 1 04 is provided. Other variations of the end-to-end system 100 include having the facsimile device 102 embedded within the remote station 400. Also, the handset 104 may be connected to the remote station 400. Other base stations 200 and 400 for receiving facsimile and voice data from a digital network are possible. Those skilled in the art will recognize that other variations of the end-to-end station 100 are also contemplated to be within the scope of the invention. FIG. 2 depicts a high level block diagram of the base station 200 that is adapted to communicate with an analog telephone network such as the ubiquitous POTS network 50. The base station 200 may operate as a transmitter and/or as a receiver. In a transmitter mode of operation, the base station 200 receives voice and/or facsimile data from the POTS network 50, processes the received POTS data, and transmits the processed POTS data to a remote station 400 via a wireless link. Alternatively, in a receiver mode of operation, the base station 200 receives voice and/or facsimile data from the remote station 400 via the wireless link, processes the received facsimile and voice data and couples the processed data to the POTS network 50. The operation of the remote station 400 will be described in more detail below with respect to FIG. 4. Specifically, the base station 200 of FIG. 2 comprises a linear codec 202, a voice compressor/decompressor 204, a facsimile compander/ expander 206, a facsimile data splitter/ combiner 208, a radio frequency (RF) multi-channel modem 210 and an antenna 201 . As the base station 200 may transmit and receive facsimile and compressed voice signals from the digital wireless link, the signal paths between base station 200 components are shown with bi-directional arrows to illustrate complementary functions. For example, the modem 210 modulates signals produced by the voice compressor/decompressor 204 and by the data splitter/combiner 208 for RF transmission via the antenna 201 . The modem 210 also demodulates a RF signal received by the antenna 201 . Other components within the base station 200 may also operate in receive and transmit modes, as will now be discussed. Referring to FIG. 2, the linear codec or linear coder-decoder 202 receives either facsimile or voice signal from a POTS network 50. Unless the POTS network 50 is specifically programmed to simultaneously transmit facsimile and compressed voice signals on a single telephone line to the codec 202, the POTS network 50 generally propagates only one type of signal at any one time. The linear codec 202 samples either the received facsimile or compressed voice signals at, illustratively, an 8 kHz sampling rate using a 14-bit analog to digital converter (ADC). The linear codec 202 operates as a signal converter that converts the received signals into digital form. The converted signals are coupled to the voice compressor/ decompressor 204 via signal path S1 and coupled to the compander/ expander 206 via signal path S5. Signal paths S1 and S5 convey, illustratively, 1 1 2 kilobits per second (Kbps) digital data streams. The voice compressor/decompressor 204 compresses the converted voice data according to, illustratively, the G.727 standard (International Telecommunications Union Recommendation G.727) to produce a compressed voice signal, illustratively a 32 Kbps data stream, that is coupled to the modem 210 via signal path S2. The voice compressor/ decompressor 204 operates as a voice signal processor. The compander 206 compands the converted facsimile data according to, illustratively, the G.71 1 standard (International Telecommunications Union Recommendation G.71 1 ) to produce a 64 Kbps data stream that is coupled to the data splitter 208 via signal path S4. The data splitter 208 or signal segmenter splits or segments the companded 64 Kbps facsimile data stream into two 32 Kbps data streams or segments that are coupled to the RF multi-channel modem 210 via signal path S3. As the companded facsimile data is transmitted at twice the data rate than compressed voice data, thereby requiring twice the bandwidth as compressed voice data, the data splitter 208 segments the companded facsimile data into a format suitable for transmitting compressed voice data. Specifically, the signal segmenter segments a facsimile signal into a plurality of segmented facsimile signals, where each segmented facsimile signal occupies a bandwidth that is less than or equal to a bandwidth of the compressed voice signal. Although segmentation may occur at the bit level (e.g., every other bit), byte level or packet level, other implementations are contemplated within the scope of the invention. Since facsimile data requires approximately twice the bandwidth of voice data, the base station 200 must allocate additional bandwidth for transmitting the facsimile data over the wireless link. The bandwidth allocation depends on whether the base station 200 uses time division multiplexing (TDM) or frequency division multiplexing (FDM) for transmitting facsimile and voice data over the wireless link. If the base station 200 uses TDM, then the base station 200 allocates a greater number of time slots for facsimile data (e.g., twice the number allocated for voice data). Alternatively, if the base station 200 uses FDM, then the base station 200 allocates a greater number of frequency bands or codes for facsimile data (i.e., twice the number allocated for voice data). To simplify the allocation of twice as many time or frequency bands to facsimile data as to voice data, the facsimile data is split into two data streams. Thus, by allocating the same number of time or frequency bands to each of the voice data stream, first facsimile data stream and second facsimile data stream, the facsimile data will inherently receive twice the time or frequency band allocation. It will be appreciated by those skilled in the art that other divisions of data (e.g., a factor of three or four) may be effected to further increase the bandwidth allocation to the facsimile data. Additionally, the base station 200 may use other multiplexing techniques, such as code division multiplexing (CDM), for transmitting facsimile and voice data streams The modem 210 modulates the compressed voice signal as well as the previously split or segmented facsimile signal for transmission over the wireless link. The modem 210 may modulate these signals using FDM, TDM or CDM. The modulated voice and facsimile signals are transmitted to the wireless link via the antenna 201 . The base station 200 in FIG. 2 may also receive modulated facsimile and cordless voice signals from the remote station via the wireless link. In the receive mode of operation, the modem 21 0 receives the RF modulated facsimile and/or voice signals from the remote station and demodulates these signals. The demodulated signals are coupled to the voice decompressor 204 via signal path S2 and to the data combiner 208 via signal path S3. The decompressor 204 decompresses the demodulated voice signal while the data combiner 208 combines the demodulated facsimile signals. These functions are the reverse of that previously discussed for the base station 200 in the transmitter mode. The decompressed voice signal is coupled with the linear codec 202 via signal path S1 while the combined facsimile data is coupled with the expander 206 via signal path S4. The expander 206 expands the combined signal, which is also coupled to the linear codec 202 via signal path S5. The codec 202 operates in the receiver mode as a 1 4-bit digital to analog converter (DAC) to convert the decompressed voice signal and expanded facsimile signal to analog inputs into the POTS network 50. FIG. 3 depicts a high level block diagram of a base station 300 that is adapted to communicate with a digital telephone network 60. In contrast to the POTS network 50, the digital telephone network 60 may simultaneously transmit facsimile and compressed voice signals. As such, the base station 300 may also simultaneously receive and/or transmit facsimile and compressed voice signals. The base station 300, as with the base station of FIG. 2, operates as a transceiver having a transmitter mode and a receiver mode. The base station 300 of FIG. 3 includes a cable modem or digital subscriber line (DSL) modem 302, an encoder/decoder 304, a voice compressor 306, a data splitter/combiner 308, a RF multi-channel modem 310 and an antenna 301 . These components also operate in a bi-directional, full duplex manner, such as previously described with respect to the components of the base station 200 of FIG. 2. The cable modem or DSL modem 302 receives facsimile and voice signals from the digital telephone network 60 through, illustratively, a coaxial cable or twisted wire pair medium. The modem or signal converter 302 decodes the received signals and couples the decoded signals to the encoder/decoder 304 via signal path S6 and to the data splitter 308 via signal path S10. Unlike base station 200 of FIG. 2, the voice signal processor in this embodiment of the base station 300 either compresses or decompresses the decoded voice data in two distinct stages. First, the encoder/decoder 304 decodes the voice signal received from the digital network 60. Then the voice compressor/decompressor 306 compresses the decoded voice data and couples the decompressed and decoded voice data to the modem 31 0. The encoder/decoder 304 and compressor/decompressor 306 combination operates as a voice processor. The encoder/decoder 304 operates as either a compressor/ decompressor or as a compander/expander. If the received voice data has been subjected to compression, then the encoder/decoder 304 operates to decompress the received voice data. Similarly, if the received voice data has been subjected to companding, then the encoder/decoder 304 operates to expand the received voice data. The resulting decompressed or expanded voice signal is coupled to the voice compressor 306 via signal path S7. The compressor 306 compresses the previously decompressed or expanded voice data and couples the compressed voice data to the RF multichannel modem 310 via signal path S8. The data splitter 308 or signal segmenter receives the decoded facsimile data stream, illustratively, 64 Kbps, from the modem 302, and splits or segments the decoded facsimile into two 32 Kbps data streams for subsequent transport over the wireless link. Each of the segmented facsimile streams occupies a bandwidth that is less than or equal to a bandwidth of the compressed voice signal. The resulting "split" or segmented facsimile signals are coupled to the RF multi-channel modem 310 via signal path S9. Note that this embodiment of the base station 300 does not include a compander/expander, as the facsimile data is generally received from the digital network 60 in a companded state. The modem 310 modulates the compressed voice signal received via signal path S8 and the split or segmented facsimile signal received via signal path S9 in substantially the same manner as described above with respect to the modem 210 of FIG. 2. The antenna 301 transmits the modulated voice and facsimile signals over the wireless link. FIG. 4 depicts a high level block diagram of a remote station 400 suitable for use with either of the base stations 200 and 300 depicted, respectively, in FIG. 2 and FIG. 3. As such, the remote station 400 may receive facsimile and voice signals previously transmitted by the base station 200 or 300 over the wireless link. The block diagram for the remote station 400 includes substantially the same components as the block diagram for the base station 200 shown in FIG. 2. As with the base stations 200 and 300, the remote station 400 operates as a transceiver having both a receive mode and a transmit mode. In a receive mode of operation, the remote station 400 receives voice and/or facsimile data from a base station 200 or 300, processes the received data and provides the processed data at an analog input/output port for subsequent use by a facsimile machine, answering machine or person. In a transmit mode of operation, the remote station 400 receives voice and/or facsimile signal via the input/output port, processes the received signal and couples the processed signal to the base station 200 or 300 via RF transmission. Specifically, the remote station 400 includes a linear codec 402, a voice decompressor/compressor 404, an expander/compander 406, a data combiner/splitter 408, a RF multi-channel modem 410 and an antenna 401 . These components are also bi-directional, full duplex, as the remote station 400 will convert data in the reverse direction if applied for transmitting facsimile and compressed voice signals over the wireless link. The modem 41 0 receives the transmitted facsimile and voice data signals through the antenna 401 . The modem 41 0 demodulates the received facsimile and voice signals into, illustratively, 32 Kbps signals. The modem 41 0 couples the demodulated signals to the voice decompressor/compressor 404 via signal path S1 1 and to the data combiner/ expander 408 via signal path S 1 5. The voice decompressor/compressor 404 decompresses the demodulated voice signal into, illustratively, a 1 1 2 Kbps data stream. This decompression is the complementary to the compression performed by the voice compressor 204. The voice decompressor/compressor 404, which operates as a voice processor, couples the decompressed voice signal to the linear codec 402 via signal path S1 2. The data combiner/splitter 408 combines at least two 32 Kbps demodulated and previously segmented facsimile signals into a 64 Kbps signal. The data combiner/splitter 408 couples the combined facsimile signal to the expander/compander 406 via signal path S1 4. The expander/compander 406 expands the combined signals into, illustratively, a 1 1 2 Kbps data stream and couples the expanded facsimile signal to the linear codec 402 via signal path S13. The data combiner/ splitter 408 and expander/compander 406 combination operates as a facsimile processor as with the base station 200. The linear codec 402 operates, illustratively, as a 14-bit digital-to-analog converter (DAC) running at 8 kHz. In this mode, the codec 402 converts the compressed voice signal and expanded facsimile signal into analog signal inputs. As such, one or more remote facsimile machines 102 or telephone handsets 104 can be coupled to the output of the remote station 400. The remote station 400 may also transmit facsimile and digital cordless voice data signals in the reverse outgoing direction to the wireless link. In this transmit mode, the remote station 400 components operate in the reverse manner to the remote station 400 in the receive mode. The operation of the remote station 400 in the transmit mode is substantially the same as the base station 200 of FIG. 2 in the transmit mode, as voice data is compressed and facsimile data is companded. Specifically, the remote station 400 compresses the voice data signal at, illustratively, 32 Kbps to the wireless link. In the case of facsimile data, the remote station 400 compands, illustratively, at 64 Kbps, to the wireless link, since the facsimile signal uses twice the bandwidth of the voice signal. FIG. 5 depicts a high level block diagram of a base station 500 adapted to communicate with a digital telephone system or digital network 60 that uses a single voice compression/decompression technique for both the wireless link and the digital network 60. In contrast to the base station 300 shown in FIG. 3, the voice compression techniques are the same for transmission to the wireless link and to the digital network 60. As such, the incoming voice signal to the base station 500 is in a compressed state suitable for transmission over the wireless link. The voice signal compressor for this base station 500 is, in essence, a unity compressor, as there are no separate compression modules for the digital network 60 or the wireless link. Specifically, the base station 500 includes a Cable or Digital Signal Line (DSL) modem 502, a data splitter/combiner 504, a RF multi-channel modem 506 and an antenna 501 . As with the other base stations 200 and 300, the components of this base station 500 are bi-directional depending on whether the base station 500 operates as a transmitter or as a receiver. The base station 500 may also simultaneously transmit facsimile and compressed voice data. In a receiver mode of operation, the cable modem or DSL modem 502, which operates as a signal converter, decodes the facsimile and compressed voice signals from the digital network 60. The cable modem or DSL modem 502 couples the decoded voice signal to the RF multi-channel modem 506 via signal path S1 6 and couples the decoded facsimile signal to the data splitter via signal path S18. The data splitter 504 or signal segmenter splits or segments the decoded facsimile signal into smaller data streams and couples the RF multi-channel modem 506 via signal path S17. Each of the segmented data streams occupies a bandwidth that is less than or equal to a bandwidth for a compressed voice signal. The modem 506 modulates the decoded compressed voice signal and segmented facsimile signal, where the modulated signals are coupled to the wireless link via the antenna 501 . The base station 500 may receive facsimile and compressed voice signals from the wireless link as with the other base stations 200 and 300. The signal conversions are the reverse than of the base station 500 in a receiver mode. In addition, the remote station 400 is suitable for use with this base station 500. Advantageously, the invention transmits facsimile data over the same wireless link used for transmitting compressed voice data. It is specifically noted that the slotted transmission architecture may be adapted to provide varying bandwidth allocation of the processed facsimile and compressed voice signals. It is also noted that while a single voice channel and a single facsimile channel are depicted, multiple voice and/or facsimile (or other data) channels may be employed within the context of the invention. The numerical values used herein are only examples. As these values are not intended as being limiting, other values and standards are contemplated to be within the scope of the invention. Although various embodiments which incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.

Claims: What is claimed is: 1 . A system for communicating voice and non-voice signals between a first station and a second station, where said first station comprises: a signal converter coupled to a communications network; a voice signal processor for producing a compressed voice signal; a signal segmenter coupled to said signal converter for segmenting a non- voice signal to form a plurality of segmented non-voice signals, each having a bandwidth that is less than or equal to a bandwidth of the compressed voice signal; a modem, coupled to said voice processor and said signal segmenter, for transmitting said compressed voice signal and said plurality segmented facsimile signals to said second station. 2. The system of claim 1 wherein said non-voice signal comprises a facsimile signal. 3. The system of claim 1 wherein said modem receives a compressed voice signal and a plurality of segmented facsimile signals from said second station, said voice signal processor decompresses said received compressed voice signal and said signal segmenter combines said received segmented facsimile signals to form a received facsimile signal. 4. The system of claim 1 wherein said signal converter is a linear codec. 5. The system of claim 1 wherein said signal converter is a digital modem. 6. The system of claim 5 wherein said digital modem receives and transmits said compressed voice signal and said segmented facsimile signals simultaneously. 7. The system of claim 6 wherein said voice signal processor and said signal segmenter operate simultaneously. 8. The system of claim 1 wherein said voice signal processor comprises a voice signal compressor. 9. The system of claim 1 further comprising a compander coupled to said signal converter and said signal segmenter. 10. The system of claim 1 wherein said signal segmenter is a data splitter. 1 1 . The system of claim 2 further comprising a telephone handset and a facsimile machine coupled to said second station. 1 2. A system for communicating voice and facsimile signals between a first station and a second station, where said second station comprises: a modem for receiving a compressed voice signal and a plurality of segmented facsimile signals from said first station; a voice signal processor, coupled to said modem, for decompressing said compressed voice signal to form a voice signal; a signal combiner, coupled to said modem, for combining said plurality of segmented facsimile signals to form a facsimile signal, where said facsimile signal has a bandwidth that is greater than a bandwidth of the compressed voice signal; and a codec for coupling the facsimile signal and the voice signal to at least one user device. 13. The system of claim 12 wherein said voice signal processor compresses a voice signal to form a compressed voice signal and said signal combiner segments a facsimile signal into a plurality of segmented facsimile signals, each having a bandwidth that is less than or equal to a bandwidth of the compressed voice signal. 14. The system of claim 12 wherein said voice signal processor and said signal combiner operate simultaneously. 1 5. The system of claim 1 2 wherein said voice signal processor comprises a voice signal decompressor. 1 6. The system of claim 1 2 further comprising a compander coupled to said signal converter and said signal combiner. 17. The system of claim 1 2 wherein said signal combiner is a data combiner. 1 8. The system of claim 1 2 wherein said user devices comprise a telephone handset and a facsimile machine. 1 9. A system for communicating voice and non-voice signals between a base station and a remote station, where said base station comprises: a signal converter coupled to a communications network that propagates both non-voice and voice signals; a voice signal processor, coupled to said signal converter, for producing a compressed voice signal; a signal segmenter coupled to said signal converter, for segmenting a non- voice signal to form a plurality of segmented non-voice signals, each having a bandwidth that is less than or equal to a bandwidth of the compressed voice signal; a modem, coupled to said voice processor and said signal segmenter, for transmitting said compressed voice signal and said plurality segmented non-voice signals to said remote station; and said remote station comprises: a modem for receiving a compressed voice signal and a plurality of segmented non-voice signals from said base station; a voice signal processor, coupled to said modem, for decompressing said compressed voice signal to form a voice signal; a signal combiner, coupled to said modem, for combining said plurality of segmented non-voice signal to form a non-voice signal, where said non-voice signal has a bandwidth that is greater than a bandwidth of the compressed voice signal; and a codec for coupling the non-voice signal and the voice signal to at least one user device. 20. A method of communicating between a first station and a second station comprising the steps of: compressing a voice signal to form a compressed voice signal; processing a non-voice signal to segment said non-voice signal into a plurality of segmented non-voice signals, each segment non-voice signal having a bandwidth that is less than or equal to a bandwidth of said compressed voice signal; transmitting said compressed voice signal and said segmented non-voice signals from said first station to said second station within a channel having a bandwidth that is substantially the same as the bandwidth of the compressed voice signal. 21 . The method of claim 20 wherein said processing step further comprises the step of companding said non-voice signal. 22. The method of claim 20 wherein said voice and non-voice signals are provided by a communications network. 23. The method of claim 20 wherein said voice and non-voice signals are provided by at least one user device. 24. The method of claim 20 wherein said non-voice signal comprises a facsimile signal.

Inventors: KNUTSON PAUL GOTHARD, RAMASWAMY KUMAR, RAMEY BLAINE EDWARD, KNUTSON, PAUL, GOTHARD, RAMASWAMY, KUMAR, RAMEY, BLAINE, EDWARD
Applicants: KNUTSON PAUL GOTHARD, RAMASWAMY KUMAR, RAMEY BLAINE EDWARD, THOMSON LICENSING SA, KNUTSON, PAUL, GOTHARD, RAMASWAMY, KUMAR, RAMEY, BLAINE, EDWARD, THOMSON LICENSING S.A.
Application year: 2000
Main classification: H04L12
IPC codes: H04J1, H04J3, H04L12, H04N1