GB2322518A

GB2322518A - Apparatus and method for high speed data transfer over telephony channels in a cable communications environment

Info

Publication number: GB2322518A
Application number: GB9802796A
Authority: GB
Inventors: Douglas J Newlin
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 1997-02-12
Filing date: 1998-02-11
Publication date: 1998-08-26
Also published as: DE19805441A1; IL122977A0; GB9802796D0; ID21376A; AU5213598A; CN1193230A; BR9800595A

Abstract

An apparatus (200) and method are provided for data transmission and data reception over telephony channels in a cable communications environment. The apparatus (200) includes a cable network interface (210) coupleable to a communications channel (103 see Fig 1) for data transmission and reception utilizing a first protocol; a processor arrangement such as a microprocessor subsystem (235); and a user modem interface (250). The user modem interface (250) and the processor arrangement are responsive when operably coupled, through a set of program instructions, to establish a communications connection and determine whether the communications connection is direct digital; when the communications connection is direct digital, the user modem interface (250) is further responsive to transfer data to the processor arrangement and the cable network interface (210) to process data in a digital mode for data transmission and data reception; and when the communications connection is not direct digital, the user modem interface (250) and the processor arrangement are further responsive to process data in an analog mode for data transmission and data reception.

Description

1 2322518 APPARATUS AND METHOD FOR HIGH SPEED DATA TRANSFER OVER TELEPHONY

CHANNELS IN A CABLE COMMUNICATIONS ENVIRONMENT

Field of the Invention

This invention relates in general to data, video and multimedia communications systems and devices and, more specifically, to an apparatus and method for high speed data transfer over telephony channels in a cable communications environment.

Background of the Invention

With the advent of multimedia communications, telecommunications and data communications have become increasingly complex. For example, multimedia communications applications such as real time transmission of digitally encoded video, voice, and other forms of data, may require new forms and systems for such data communications and telecommunications. One such new communications system is the CableComm system currently being developed by Motorola, Inc. In the CableComm system, a hybrid optical fiber and coaxial cable ("HFC") is utilized to provide substantial bandwidth over existing cable lines io secoadary stations or devices such as individual, subscriber access units (referred to as multimedia access apparatuses) connected to one or more 2 telephones, videophones, and/or a personal computers, workstations, other data terminal equipment ("DTE"), for example, in households having new or preexisting cable television capability. These coaxial cables are further connected via fiber optical cables to a central location having centralized, primary (or "head end") controllers or stations having receiving and transmitting capability. Such primary equipment may be connected to any variety of networks or other information sources, from the Internet, various on line services, telephone networks, to video/movie subscriber services. With the CableComm system, digital data, voice, video, and other multimedia data may be transmitted both in the downstream direction, from the primary station or controller (connected to a network) to the secondary station of an individual user (subscriber access unit), and in the upstream direction, from the secondary station to the primary station (and to a network).

In this cable environment, a need has remained for an apparatus and method for high speed data transfer not only within the cable environment, but also in an overall environment which includes prior art media such as analog telephone lines and digital telephone lines. In addition, with the advent of high speed but asymmetric analog modems, a need has remained for an apparatus and method to provide high speed data transfer symmetrically, namely, in both the upstream and downstream directions.

3 Brief Description of the Drawings

FIG. 1 is a block diagram illustrating a communications system in accordance with the present invention.

FIG. 2 is a block diagram illustrating a primary station in accordance with the present invention.

FIG. 3 is a block diagram illustrating a multimedia access apparatus in accordance with the present invention.

FIG. 4 is a detailed block diagram illustrating a preferred embodiment of a multimedia access apparatus in accordance with the present invention.

FIG. 5 is a flow diagram illustrating a method for high speed data transfer over telephony channels in a cable communications environment in accordance with the present invention.

4 Detailed Description of the Invention

As mentioned above, a need has remained for an apparatus and method for high speed data transfer not only within the cable environment, but also in an overall environment which includes prior art media such as analog telephone lines and digital telephone lines. In addition, with the advent of high speed but asymmetric analog modems, a need has remained for an apparatus and method to provide high speed data transfer symmetrically, namely, in both the upstream and downstream directions. The apparatus and method of the present invention fulfills these needs, providing for symmetrical, high speed data transfer, which is also capable of communicating in a variety of environments, including cable, digital telephony, and analog telephony environments.

FIG. I is a block diagram illustrating a communications system (or system architecture) 100 in accordance with the present invention. The CableComm portion of the communications system 100 consists of a primary station (or device) 105 coupled through a communications channel 103 to one or more multimedia access apparatuses ("MAAs", also referred to as secondary stations) 110, with the primary station 105 coupled (or coupleable) to a network 160, via a network switch 135 (also referred to as a local digital switch 1335) of a central office 102. In th-ce preferred --.-..b-d;.ment, multimedia access apparatus 110 (illustrated in FIG. 3), is implemented as multimedia access apparatus 200 (illustrated in FIG. 4), and reference to any of the various embodiments of the multimedia access apparatuses 110 or 200 should be understood to include the other embodiments and their equivalents. As indicated above, in the preferred CableComm embodiment, the communications channel 103 is hybrid fiber coaxial cable (HFC). Other, non-CableComm portions of the system 100 are known in the art, such as analog communications devices ("ACDs") 115 (such as POTS telephones or analog modems) coupled through analog telephony line 117 connected to a line card (or other analog-type switch) 137 in central office 102 (where POTS refers to "plain old telephone system") for communication with the network 160; and digital communications devices ("DCDs") 122 (such as ISDN telephones and ISDN terminal adapters) connected through digital telephony line 119 to local digital switch 135 in a central office 102 for communication with the network 160. Typically in such prior art, non-CableComm portions of the system 100, communication is digital except for the digital to analog (D/A) and analog to digital (A/D) conversions at the line card 137, for analog transmission and reception over analog telephony line 117 to and from the various analog communications devices 115.

The CableComm. portion of the communications system 100 provides communications services such as telephony, video conferencing, data networking and transmission, enterprise networking and telemetry, utilizing the network 160, and provisioning for other services, such as cable 6 is television ("CATV") and other services, utilizing CATV and other services infrastructure 112. The primary station 105, described in greater detail below with reference to FIG. 2, preferably is a shared (or trunked) device in a central location and provides services to many subscribers or other users. The multimedia access apparatuses 110 and 200, described in greater detail below with reference to FIGs. 3 and 4, preferably are located within or about a user's premises, and may be coupled to telephones, personal computers, video displays, video cameras, multimedia equipment, and so on. In the preferred embodiment, the communications channel 103 is hybrid fiber coaxial cable ("HFC"), capable of high capacity (or high bandwidth) data communications which may occur between the various secondary stations (MAAs) 110 and the network 160. The network 160, for example, may be a public switched telephone network ("PSTN") or an Integrated Services Digital Network ("ISDN"), or any combination of such existing or future telecommunications networks.

As discussed in greater detail below, communication between the primary station 105 and the multimedia access apparatuses 110 occurs utilizing a first protocol (or modulation mode), such as the CACS protocol (discussed below) utilized in the preferred embodiment or another time division multiple access ("TDMA") protocol. At the primary station 105, any information or signal transmitted to or from a secondary station (MAA) 110 (utilizing the first protocol) is converted, utilizing an appropriate interworking function, into a second 7 protocol signal, such as a signal having a form suitable for transmission over a particular network type, such as an analog signal suitable for transmission over the PSTN portion of the network 160, an ISDN protocol signal for transmission over an ISDN network portion of the network 160, or an IP packet signal for transmission over a packet-based portion of the network 160. The only requirement for the type of first protocol utilized between the primary station 105 and the multimedia access apparatuses 110 is that the first protocol should have sufficient capacity to interface, in real time, with other protocols which may be used by various networks such as network 160, such as ISDN, T1 or El protocols operating at bit rates of 64 kbps (kilobits per second), 128 kbps, 1.54 Mbps, 2.048 Mbps, or more. Preferably, the first protocol should also provide for trunking or sharing of applicable channels (also referred to as multiple access), to provide high efficiency data transmission for both circuit switched (or dedicated bandwidth) transmissions and for packet-based (bursty or variable bandwidth) transmissions. As a consequence, while the preferred first protocol is the CACS protocol discussed below, those skilled in the art will recognize that innumerable other equivalent protocols and modulation modes also may be utilized.

FIG. 2 is a block diagram illustrating a primary station 105 in accordance WIth the present invention. A primary station 105, also referred to as head end equipment, includes a control unit referred to in the preferred embodiment as a cable 8 control unit ("CCU") 155, a network interface 130, and may also include a combiner 104 which is coupleable to the CATV video services infrastructure 112. The CCU 155 consists of a communications controller 145 and a transceiver 120 or preferably a bank of transceivers 120, also referred to as cable port transceiver ("CPX") cards in the preferred embodiment. The communications controller 145 is preferably a form of a processor arrangement, discussed in greater detail below. The communications controller 145 transmits and receives network (or other industry) standard signals, such as time division multiplexed ("TDM") digital signals, via the network interface 130, to and from a local digital switch ("LDS") 135, which in turn connects to the rest of the network (illustrated in FIG. 1). The communications controller 145 may also transmit and receive IP (or other industry) standard packet-based signals such as Internet packets, frame relay packets, X.25 packets, ATM (asynchronous transfer mode) packets. In the preferred embodiment, incoming (received) signals to the communications controller 145 are converted to an internal signaling format such as a first protocol format, may also have TDM time slots interchanged, and are then routed to the transceivers 120. The transceivers 120 convert the received signals to frequencies radio frequencies ("RP)) suitable for the communications channel 103 and the first protocol, such as r"-%-.'Lio frequencies compatible with cable television (CATV) networks. Conversely, the transceivers 120 also receive first protocol signals transmitted from multimedia 9 access apparatuses I 10 via the communications channel 103, demodulate those signals, and with the communications controller 145, convert those first protocol signals to a form suitable for transmission over the network 160. As discussed in greater detail below, the primary station 105 provides concentration of the resources of the network 160 through time slot and frequency management techniques.

In the preferred embodiment, as mentioned above, the signaling between the primary stations 105 and the MAAs 110 (via the communications channel 103) uses a first protocol referred to as "CACS" (for Dible _ACcess Signaling), for transmission and reception of data such as voice, -video, computer files and programs, multimedia applications, and other information (collectively referred to as data). CACS is a multi-layered protocol consisting of a plurality of 768 kbps P/4-DQPSK (differential quadrature phase shift keying) modulated RF carriers using TDM framing in the downstream path (from the primary station 105 to a multimedia access apparatus 110) and TDMA (time division multiple access) in the upstream path (to the primary station 105 from a multimedia access apparatus 110). In the preferred embodiment, each CACS carrier (carrier frequency or center frequency) supports as many as eight time slots of individually addressable user data packets, in which each packet contains 160 bits of user data (the "payload") phuss synchronizz-Ation, address and error correction information. The preferred CACS frame rate is 400 frames per second, providing a net user data throughput of 64 kbps (kilobits per second) for each assigned time slot. Time slots also may be concatenated or otherwise combined to provide even greater data rates, for example, up to 512 kbps per carrier when all eight time slots of an RF carrier are assigned to a single user, or higher data rates when additional RF carriers are utilized.

As a consequence, N x 64 kbps services may be supported with the CACS protocol, where N is the number of assigned time slots. In the case of connectivity for ordinary telephony commonly known as POTS, a single time slot is used in which digital PCM (pulse code modulated) audio samples are transported in the payload of the CACS time slot. In the case of connectivity for higher rate services, such as basic rate ISDN (two 64 kbps B channels plus one 16 kbps D channel), two or more time slots are used to transport the user (bearer) data. For video conferencing and telephony service, compressed digital audio and video signals may occupy from one to multiple time slots per carrier (t.Z., 8 time slots per carrier), depending on the method of compression used and the desired quality of the service.

Also in the preferred embodiment, modulated CACS RF carriers occupy an RF bandwidth of 600 kHz and may be assigned anywhere within the downstream and upstream frequency bands of the service provider. For example, in domestic, North American CATV systems, the downstream band has been designated from 50 to 750 MHz, with an upstream band designated from 5 to 40 MHz. Referring to FIG.

e_ 0 2, for transmission to multimedia access apparatuses 110 at user premises, the transceivers 120 receive a TDM data stream from the communications controller 145 and create CACS frames of eight time slots, along with associated overhead signaling information (including error control Idata), resulting in a 768 kbps data stream. The data stream is then converted to a P/4-DQPSK signal, which in turn is then upconverted in frequency from baseband to an RF carrier within the CATV downstream band (or other downstream band suitable for use on an HFC or other communications medium). This P/4-DQPSK signal may then be optionally combined (in the combiner 104 of the primary station 105) with other signals (such as video) from the CATV and other services infrastructure 112, and transmitted over the communications channel 103.

At the receiving end, as discussed in greater detail below, a multimedia access apparatus 110 downconverts the CACS carrier to baseband and demodulates the P/4-DQPSK signal, resulting in received CACS frames. Time slot information (i.e., the data in the payload) is then extracted from the CACS frames and transferred to an audio codec in the case of telephony (a POTS call), or transferred to an audio/video compression and decompression subsystem in the case of a video conferencing call or session, or transferred to a processor arrangement or modem subsystem in the case of other data trarisirnissions. Conversely, for upstream transmission, voice, video or other data originating, respectively, from an audio codec, or an audio/video compression and decompression 12 subsystem, or a processor arrangement, is put into CACS protocol formatted TDMA data packets. The TDMA data packets are then converted into a P/4-DQPSK signal, upconverted to an RF carrier, and injected into the upstream path on communications channel 103. In turn, one of the transceivers 120 receives the upstream signal from a multimedia access apparatus 110, RF downconverts the signal to baseband and demodulates the P/4-DQPSK signal, resulting in a received TDMA data packet. The user data is then extracted from the packet and transferred to the communications controller 145, which reformats the user data into an appropriate network signal (analog or digital), generally referred to as a second protocol signal, and, through the network interface 130, transmits the second protocol signal to the network 160 (via the local digital switch 135).

In the preferred embodiment, the CACS protocol consists of three types of signaling channels which use designated time slots on CACS carriers. A first type of signaling channel, referred to as a broadcast channel, is utilized to transmit general system information, only in the downstream direction to the various multimedia access apparatuses 110, and to transmit information such as terminating alerts to a multimedia access apparatus 110 when a call or other information is to be received from the network 160. A plurality oi. a second type of signaling channel, referred to as access channels, are used by the various multimedia access apparatuses 110 to gain access to the primary stations 105 and 13 network. A plurality of a third type of signaling channel, referred to as traffic channels, are full-duplex and are used to transport user data to and from the network 160.

In the preferred embodiment, traffic channels may consist of one or more time slots and are assigned to users based on demand (trunked or bonded (bandwidth on demand)) from a pool of available time slots. A traffic channel is assigned for the duration of a call (POTS, ISDN, video, multimedia or other data), and upon call termination, is subsequently released to the pool of available time slots. When a multimedia access apparatus 110 first powers up, it registers with the CCU 155 by first scanning the downstream spectrum for a CACS broadcast channel, synchronizing with that channel, and obtaining information concerning a location of an access channel. On the access channel, the multimedia access apparatus 110 requests an assignment of a traffic channel, and then transmits a registration message over the assigned traffic channel of the plurality of traffic channels. After registration is complete, the multimedia access apparatus 110 may communicate through the network 160.

If a call origination or other data transmission is required, the multimedia access apparatus 110 makes a request to the CCU 155 for the required number of time slots through the access channel. The CCU 155 then grants the request and assigns a traffLic channel (carrier frequency and associated time slot(s)). If a call or data packet delivery is required, the CCU 155 alerts the identified, addressed 14 multimedia access apparatus 110 of an incoming call or data packet over the broadcast channel. Via the access channel, the multimedia access apparatus 110 then requests a traffic channel. The CCU 155 grants the request and a traffic channel is assigned.

In the preferred embodiment, the CACS protocol also provides the capability for transferring calls to other available carrier frequencies and time slots, especially in the event of high noise conditions. Preferably, the quality of all user traffic channels is continuously monitored, and if the quality starts to degrade due to noise, the call is transferred to another RF carrier having less noise.

FIG. 3 is a block diagram illustrating a multimedia access apparatus 110 in accordance with the present invention. The multimedia access apparatus 110 includes another type or network interface such as a cable network interface 210, one or more user interfaces 215, a processor arrangement 190, and preferably a memory 195. The cable network interface 210 is coupleable to the communications channel 103 for reception of a first protocol signal, such as a p/4-DQPSK TDM signal, to form a received protocol signal; and for transmission of a first protocol signal, such as digital data in a TDMA format, to form a transmitted protocol signal, such as a p/4-DQPSK TDMA signal. These various protocol signals may also utilize protocols and modulation types (collectively referred to as protocols) other than those utilized within the CACS protocol such as, for example, more general PSK (phase shift keying) or QPSK ^5 r- (quadrature phase shift keying) modulation methods, OFDM (orthogonal frequency division multiplexing), QAM (quadrature amplitude modulation), H.320, H.323, or H.324. Depending upon the desired implementation, other forms or types of network interfaces may also be utilized, in addition to or in lieu of the cable network interface 210.

Continuing to refer to FIG. 3, one or more user interfaces 215 are utilized for various purposes, such as providing connectivity or interfacing with a telephone 170, a personal computer ("PC") 175, a video display 180, or a LAN (local area network) 185 (such as Ethernet, ATM, or electric power line LANs for home automation and telemetry). In the preferred embodiment, one of the user interfaces 215 is also utilized for reception of a control signal of a plurality of control signals, such as a request to place a telephony call, a request to place an audio and video conference call, and other control signals such as alerting signals of incoming telephony or audio and video conference calls. The processor arrangement 190 is coupled to the cable network interface 210, to the memory 195, and to one or more user interfaces 215. As explained in greater detail below, the processor arrangement 190 (and the communications controller 145) may be comprised of a single integrated circuit ("IC"), or may include a plurality of integrated circuits or other components connected or grouped together, such as microprocessors, digital signal processors, ASICs, associated memory (such as RAM and ROM), and other ICs and components. As a consequence, as used herein, the 16 term processor arrangement (and communications controller) should be understood to equivalently mean and include a single processor, or arrangement of processors, microprocessors, controllers, or some other grouping of integrated circuits which perform the functions discussed in greater detail below, with associated memory, such as microprocessor memory or additional RAM, ROM, EPROM or E2PROM. As discussed in greater detail below, the methodology of the invention may be programmed and stored, as a set of program instructions for subsequent execution, in the processor arrangement 190 with its associated memory (or in memory 195) and/or one of the user interfaces 215, such as the microprocessor subsystem 235 in conjunction with the user modem interface 250 illustrated in FIG. 4, or other equivalent components. The program instructions may then be executed when the processor arrangement 190 is operably coupled, for example, when the multimedia access apparatus is powered on and connected to communications channel 103 for data transmission and reception.

FIG. 4 is a detailed block diagram illustrating the preferred embodiment of a multimedia access apparatus 200 in accordance with the present invention. Many of the various components comprising multimedia (or video) access apparatus 110 have been disclosed and discussed in detail in the related applications, and in the interests of brevity, will not be elaborated upon herein. As illustrated in FIG. 4, the multimedia access apparatus 200 is coupled or connected to

17 communications channel 103 via cable network interface 210 (and directional coupler 225), for communication with a primary station 105. The cable network interface 210 consists of a cable network (CATV) radio frequency (RF) transceiver 220 with communications ASIC 230. The cable network interface 210 is connected to a processor arrangement, which in the preferred embodiment is comprised of a microprocessor subsystem 235, such as a Motorola MC68LC302. The various user interfaces 215 (illustrated in FIG. 3) are implemented as user/audio interface 240, user modem interface 250, and a user video interface 257 (comprised of audio/video compression and decompression subsystem 245, RF modulator 255 and RF demodulator 260). In the preferred embodiment illustrated in FIG. 4, while all three of these user interfaces 215 are implemented, for purposes of the invention herein, only the modem interface 250 is required, and the user/audio interface 240 and user video interface 257 are merely optional. While the term "modem" is utilized to refer to user modem interface 250 as an instantiation of a user interface 215 designed for data transfer, it should be understood that the term "modem" is utilized in a broadest sense of a general data communications device, and is not limited to particular modulation/demodulation functions, analog modem functions or digital modem functions.

Continuing to refer to FIG. 4, the microprocessor subsystem 235 is connected to an audio/video compression and decompression subsystem 245, which in turn is connected 18 to an RF modulator 255 and an RF demodulator 260 which are utilized, respectively, to transmit and receive video or other multimedia signals on communications channel (or line) 271 (via directional coupler 270), such as for video conferencing ttl I As used herein, the audio/video compression and d.compression subsystem 245, RF modulator 255 and RF demodulator 260 form a user video interface 257 (as one of the user interfaces 215). The communications channel 271 is typically located within or about the user (or subscriber) premises, and for example, may be an internal 75 Ohm coaxial cable typically utilized with cable television. Video and other multimedia signals are typically transmitted through the various networks as compressed signals, and corresponding compression and decompression occurs in the audio/video compression and decompression subsystem 245 utilizing protocols such as, for example, H.320 for ISDN or H.324 for PSTN video calls. Received video or other multimedia signals (transmitted from a far end or remote party) are decompressed in the audio/video compression and decompression subsystem 245, modulated onto an available RF carrier or channel (in RF modulator 255), transmitted on communications channel 271, and displayed on any video displays 290, such as connected televisions. Video or other multimedia signals to be transmitted (from the near end (local prarty) and sent to the far end& or remote party) are generated 0 and modulated onto an RF carrier by the multimedia input and control apparatus 295, are demodulated (in RF demodulator 19 260), and are compressed in the audio/video compression and decompression subsystem 245. The microprocessor subsystem 235 and the cable network interface 210 then process and format the video or other multimedia signal for transmission via the first protocol such as CACS to a primary station 105, and subsequently to the network 160. The microprocessor subsystem is also connected to a user interface such as user/audio interface 240, which provides for audio input and output (via telephone 280 coupled via an RJI1 jack), and also provides for the reception or entry of a plurality of control signals, which may include control signals input from a telephone 280, such as off hook, on hook, flash, various DTMF tones, or other programmed or programmable control signals. As disclosed in the related applications, the user/audio interface 240 also provides codec (coder-decoder) functionality and SLIC (subscriber loop interface circuit) functionality.

Continuing to refer to FIG. 4, the microprocessor subsystem 235 is also connected to a user modem interface 250, as another form of user interface 215. The user modem interface 250 is comprised of a digital signal processor (DSP) (such as a Motorola DSP56303/100), and is controlled by the microprocessor subsystem 235. Alternatively, depending upon the desired implementation, such as whether the user video interface 257 and/or user/audio interface 240 are included, the DSP of the user modem interface 250 may be shared between and among these other user interfaces 215. Also as illustrated in FIG. 4, the user modem interface 250 iscoupled to a personal computer (PC) 285 (typically via an RS-232 interface or a universal serial bus, not illustrated), for data transmission and reception, utilizing either of two modes, either a direct digital mode or an analog mode, in accordance with the present invention. In addition, when the user video interface 257 is implemented, the apparatus and method of the present invention may also be utilized for audio/video transmission and reception, including utilization of various forms of audio/video compression and decompression, such as H.320 and H.324.

The direct digital mode of the user modem interface 250 is utilized in circumstances in which the user modem interface 250 will communicate with another data communications device over a completely digital connection, such as for communication between two MAAs 110 or 200 via the CableComm portion of the system 100 or for communication between one MAA 110 or 200 and a digital communications device 122 (via digital line 119 illustrated in FIG. 1). For such direct digital mode, the data rate may vary, for example, from 56 kbps (if the network 160 utilizes robbed bit signaling) to 64 kbps (without bit robbing) for one CACS channel, to data rates in multiples of 64 kbps, such as 128 kbps, depending upon the number of N x 64 CACS channels used. For the direct digital mode, the user modem interface 250 performs a switching function, directly transferring digital data between a connected PC 285 and the microprocessor subsystem (and cable network interface 210). The digital data is then encoded for 21 transmission utilizing the first protocol such as CACS or, conversely, first protocol (CACS) encoded data is demodulated and decoded for received digital data, both by the microprocessor subsystem and cable network interface 210. It should also be noted that for such a direct digital mode, the data rates may be symmetrical, i.e., the same data rates in the upstream and downstream directions for all connected devices.

The analog mode of the user modem interface 250 is utilized in circumstances in which the user modem interface 250 will communicate with another data communications device over a connection which is at least partially analog, such as for communication between an MAA 110 or 200 and an analog communications device 115 via analog line 117 as illustrated in FIG. 1. For such an analog mode, the data rate may also vary, for example, from 28.8 kbps, 33.6 kbps, to 40 kbps for V.34 and V.34bis modems utilized as analog communications devices 115, to as high as 56 kbps when other high speed analog modems are utilized as analog communications devices 115. Analog data rates may also vary depending upon line quality and whether the connections within the network 160 are completely digital (up to line card 137). For the analog mode, the user modem interface 250 and the microprocessor subsystem 235 perform all digital functions associated with modems, namely, all functions other than the actual digital to analog conversion for a,-ltalog transmission, such as trellis coded modulation, echo cancellation, training, line probing, etc. This encoded information (such as V.34 encoded 22 data) is then transported utilizing a first protocol such as CACS, with the D/A and AID conversions performed at the line card 137 for analog transmission and reception, respectively. It should also be noted that for such an analog mode, the data rates may be symmetrical or asymmetrical for the upstream and downstream paths. For example, while the MAA 110 or 200 is capable of a full 56 to 64 kbps in both the upstream and downstream paths to and from a primary station 105, capability for such high data rates may not be available symmetrically in the analog portions of the system 100, with the downstream path from a network 160 to an analog device 115 capable of higher data rates than the upstream path from the analog device 115 to the network 160. As a consequence, data transmission may occur at asymmetric rates, with faster data transmission in the downstream direction, such as 56 kbps compared to 28.8, 33.6, or up to 40 kbps in the upstream direction.

FIG. 5 is a flow diagram illustrating a method for high speed data transfer over telephony channels in a cable communications environment in accordance with the present invention. Beginning with start step 300, the method determines whether there is a request for modem operation, step 305, such as whether the user modem interface 250 has received a request to send from the PC 285 or has received a request to send or receive from a remote terminal or device, such as from an ACD 115, a DCD 122, or another MAA 110 or 200. (Again, the term "modem" is utilized as a shorthand 23 method of broadly referring to general data communications functionality, and is not to be limited to particular modulation/demodulation functions. ) Next, when a request for modem operation has been received in step 305, the method establishes a communications (modem) connection, step 310, such as by transmitting an appropriate command under the first protocol, g.,a, a command to go off hook. The method then determines whether the remote terminal has responded with a direct digital indication, such as that it is an ISDN terminal adapter or another MAA, step 315. When the remote terminal has responded with a direct digital indication in step 315, then a digital training sequence is performed, step 320, such as any training which may be required under ISDN, T1, El or CACS protocols. A bit rate is then determined, step 325, such as whether 64 kbps may be used (no robbed bit signaling) or 56 kbps (robbed bit signaling). The method then transmits and/or receives data at the determined data rate, in this digital mode, step 330. As indicated above, in this digital mode, the user modem interface 250 is performing a switching function, such that digital data is directly CACS encoded or decoded in the microprocessor subsystem 235 and cable network interface 210. When the remote terminal has not responded with a direct digital indication in step 315, then an analog training sequence is performed, step 335, such as any training which may be required under V.314, V.34bis or other protocols. A bit rate is then determined, step 340, such as whether 56 kbps may be used symmetrically or only in the downstream 24 direction, or whether other data rates are to be used, symmetrically or asymmetrically. The method then transmits andlor receives data at the determined data rate or rates, in this analog mode. Also as indicated above, in this analog mode, the user modem interface 250 is performing all digital portions of analog modem functions, such that digital data is modulated/demodulated and encoded/decoded under the appropriate analog protocol within the user modem interface 250, in addition to CACS or other first protocol encoding or decoding in the microprocessor subsystem 235 and cable network interface 210, with the only remaining analog modem function, namely, the D/A and All) conversions, performed at the line card 137. Following steps 330 and 345, the method may terminate, return step 350.

In summary, FIGs. 3-5 disclose an apparatus 110 or 200 for data transmission and data reception, comprising: first, a cable network interface 210 coupleable to a communications channel 103 for data transmission and reception utilizing a first protocol; second, a processor arrangement 190 (such as a microprocessor subsystem 235) coupled to the cable network interface 210; and third, a user modem interface 250 coupled to the processor arrangement 190, the user modem interface 250 and the processor arrangement 190 responsive when operably coupled, through a set of program instructions, to establish a communications connection and determine whether the communications connection is direct digital; when the communications connection is direct digital, the user modem interface 250 further responsive to transfer data to the processor arrangement 190 and cable network interface 210 to process data in a digital mode for data transmission and data reception; and when the communications connection is not direct digital, the user modem interface 250 and the processor arrangement 190 further responsive to process data in an analog mode for data transmission and data reception. The processor arrangement 190 is further responsive, when the communications connection is direct digital, to directly encode digital data utilizing a first protocol for data transmission by the cable network interface 210 and to directly decode digital data utilizing a first protocol for data received by the cable network interface 210. In addition, the user modem interface 250 and the processor arrangement 190 are further responsive, when the communications connection is not direct digital, to performing analog training, to determine a first bit rate for data transmission, and to determine a second bit rate for data reception, where the first bit rate and the second bit rate may be symmetric or asymmetric. The user modem interface 250 and the processor arrangement 190 are further responsive, when the communications connection is not direct digital, to encode digital data utilizing an analog protocol to form analog encoded data, to encode the analog encoded data utilizing a first protocol for data transmission, to decode analog encoded data utilizing a first protocol for data reception, and to decode analog encoded data utilizing an analog protocol to form digital data.

26 205 From the above discussion, numerous advantages of the apparatus and method of the present invention may be apparent. First, the apparatus and method of the present invention provide for high speed data transfer not only within the cable environment, but also in an overall environment which includes prior art media such as analog telephone lines and digital telephone lines. In addition, with the advent of high speed but asymmetric analog modems, the apparatus and method of the present invention provide high speed data transfer symmetrically, namely, in both the upstream and downstream directions. The apparatus and method of the present invention provide for symmetrical, high speed transfer in a variety of environments with a variety of dissimilar equipment, including data communications over digital telephony such as ISDN, and analog telephony over ordinary, POTS telephone lines.

From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the novel concept of the invention. It is to be understood that no limitation with respect to the specific methods and apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.

Claims

What is claimed is:

27 1. A method for data transmission and data reception, the method comprising:

(a) establishing a communications connection (310); (b) determining whether the communications connection is direct digital (315); (c) when the communications connection is direct digital, processing data in a digital mode for data transmission and data reception (330); and (d) when the communications connection is not direct digital, processing data in an analog mode for data transmission and data reception (345).
2. The method of claim 1, wherein step (c) further comprises:

(cl) performing digital training (320); and (c2) determining a bit rate for data transmission and data reception (325).
3. The method of claim 1, wherein step (c) further comprises:

(c3) directly encoding digital data utilizing a first protocol for data transmission.
4. The method of claim 1, wherein step (c) further comprises:

28 (c4) directly decoding digital data utilizing a first protocol for data reception.
5. The method of claim 1, wherein step (d) further comprises:

(dl) performing analog training (335); (d2) determining a first bit rate for data transmission (340); and (0) determining a second bit rate for data reception.

The method of claim 1, wherein step (d) further comprises:

(d4) encoding digital data utilizing an analog protocol to form analog encoded data; and (d5) encoding the analog encoded data utilizing a first protocol for data transmission.
6. The method of claim 1, wherein step (d) further comprises:

(M) decoding analog encoded data utilizing a first protocol for data reception; and (d7) decoding analog encoded data utilizing an analog protocol to form digital data.

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7 The method of claim 1 wherein the direct digital communications connection is over hybrid fiber coaxial cable.

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8. The method of claim 1 wherein the direct digital communications connection is over hybrid fiber coaxial cable and a digital telephony line.
9. The method of claim 1 wherein, when the communications connection is not direct digital, the communications connection is over hybrid fiber coaxial cable and an analog telephony line.
10. An apparatus for data transmission and data reception, the apparatus comprising: a network interface (210) coupleable to a communications channel (103) for data transmission and reception utilizing a first protocol; a microprocessor (235) coupled to the network interface (2 10); and a digital signal processor (250) coupled to the microprocessor, the digital signal processor and the microprocessor responsive when operably coupled, through a set of program instructions, to establish a communications connection and determine whether the communications connection is direct digital; when the communications connection is direct digital, the digital signal processor further responsive to transfer data to the microprocessor and network hitedd-ce to process data in a digital mode for data transmission and data reception; and when the communications connection is not direct digital, the digital signal processor and the microprocessor further responsive to process data in an analog mode for data transmission and data reception.