Abstract: A cable television system provides conditional access to services. The cable television system includes a headend from which service “instances”, or programs, are broadcast and a plurality of set top units for receiving the instances and selectively decrypting the instances for display to system subscribers. The service instances are encrypted using public and/or private keys provided by service providers or central authorization agents. Keys used by the set tops for selective decryption may also be public or private in nature, and such keys may be reassigned at different times to provide a cable television system in which piracy concerns are minimized.

Abstract: An amplifier (125) having automatic gain control (AGC) includes a gain stage (220), having a variable amplifier (215), for amplifying a signal received by the amplifier (125). The amplifier (125) also includes an AGC circuit (228) that adjusts amplification of the gain stage (220) and that includes a manual switch (246) having first and second switch settings. Sequential operation from the first switch setting to the second switch setting causes the AGC circuit (228) to automatically and correctly set the gain of the amplifier (125) without further human intervention.

Abstract: A cable television system (100) includes a display (235) for displaying program information, a terminal (120) for controlling the presentation of the program information, a memory (240) for storing operational parameters, and a receiver (220) for receiving user inputs. A method for presenting the program information within the cable television system (100) includes the steps of storing the program information, including channel information and category information indicative of categories and channels associated with the categories, receiving (510) a command indicating that channel information is to be presented, and driving (520) the display (235) to present only program information associated with channels included in a selected category. The display (235) can, for instance, be driven with a browse banner (310) or a program guide that includes channel information about channels included in the selected category and omits channel information about channels not included in the selected category.

Abstract: An optical signal is modulated by passing it through an optical signal path in an optical modulator. Different electric fields are applied across a first pair of parallel phase modulation arms so as to produce different signal phase modulations in respective portions of the optical signal; and different electric fields are also applied across a second pair of parallel phase modulation arms so as to produce different signal phase modulations in respective portions of the optical signal. The different magnitudes of the electric fields are pre-determined so as to control chirp and to promote modulation linearity. The chirp in the optical signal output from the optical modulator may be reduced or even eliminated or may be predetermined to counteract or even eliminate chirp generated in a transmission path.

Abstract: Techniques for determining an output rate for a bit stream, the output rate being determined by applying information read from the bit stream to available bandwidths. The techniques are employed to construct a statistical multiplexer 80 that multiplexes varying bit-rate bit streams. Minimum and maximum output rates for each bit stream are determined such that neither a queue for the bit stream in the multiplexer nor the bit stream's decoder will underflow or overflow. The multiplexer first allocates each bit stream its minimum bandwidth and then allocates any remaining bandwidth to the bit streams in proportion to the difference between the minimum and maximum output rates for the bit streams, with no bit stream receiving more than its maximum output rate. If there is not enough bandwidth to give every bit stream its minimum rate, glue frames may be inserted, or low priority channels dropped.

Abstract: A system for providing flexible billing in a cable environment can establish billing practices based on tier level of service, quality of service or the amount of network resources consumed. A plurality of tiers or levels of service can be defined by parameters including at least a maximum or peak bit rate or bandwidth for providing services over a shared channel. A plurality of levels or tiers of services are defined by maximum bandwidth or bit rate and a subscriber receives service at that subscribe-to level or at a slower data rate depending on availability of shared bandwidth. Quality of service is maintaining the specified bandwidth, jitter or delay. The amount of network resources consumed may be expressed in terms of the amount of data transmitted or the connect time of a network access device to the network.

Abstract: An optical transmitter (200) in a cable television system (100) includes an uncooled laser diode (250) and a thermal compensation circuit (FIG. 2). The thermal compensation circuit includes a voltage controlled attenuator (220) located between the transmitter input (205), at which an electrical information signal is received, and the laser diode (250). The thermal compensation circuit also includes a thermistor (230) that is situated physically near the laser diode (250) and that is characterized by a resistance that varies with temperature. The thermistor (230) is coupled to a controller (225) for sensing thermistor resistance changes, which are indicative of changes in the laser diode temperature, and for selectively controlling the attenuator (220) to attenuate the level of the electrical information signal.

Abstract: The rate of insertion of data, such as MPEG table packets, into an outgoing bit stream is varied by a packet handler. The packet handler, which is located in a modulator in a cable television system headend, comprises control logic and a packet router. The actual insertion rate of the outgoing data is based on the bit stream's available capacity for insertion of data and the desired insertion rate of the data. When the available capacity for insertion equals or exceeds the desired insertion rate, the actual insertion rate equals the desired insertion rate. When the available capacity for insertion is less than the desired insertion rate, the actual insertion rate is reduced from the desired insertion rate. The present invention dynamically determines the available capacity for insertion and adjusts the actual insertion rate.

Abstract: Two additional structures for addition to the Digital Video Broadcasters (DVB) Service Information (SI) for implementation of the MPEG-2 Systems Standard (ISO/IEC 13818-1) are provided: the Logical Channel Table (LCT) and the Composite Channel Table (CCT). The LCT provides the mapping between a Logical Channel Number (LCN) representing a service and the transport stream(TSID)/program number (PN) on which the service can be found. LCT entries may designate either simple conventional channels or Composite Channels. The LCT contains a Composite Channel Indicator (CCI), which when set to ‘1’, indicates that the selected channel is a composite channel. In this case, the LCT entry gives the home channel of the Composite Channel, which provides the CCT to the decoder so that the tuner can be retuned to the actual program designated in the CCT for current viewing.

Abstract: A reprogrammable subscriber terminal of a subscription television service which can have the control program code of its control processor modified by downloading new program code from the headend. The control processor stores a boot program in an internal read only memory. Upon start up and resets, the boot program determines whether the control program should be changed from a command sent from the headend. The command, termed a parameters transactions, includes the number of expected download program code transactions required to complete the control code modification, the memory space areas where the code is to be loaded, and the channel over which the download program code transactions are to be transmitted. The channel is tuned and when the boot program receives all the download program code transactions accurately and stores them, the boot program will cause the control program to be restarted at a selected address of the new or modified control program code which has been downloaded.

Abstract: An asymmetrical network for coupling customer-premises Internet hosts such as personal computers to the Internet. The head end of a CATV system has a high-bandwidth connection to the Internet. The down link connecting the personal computers to the Internet is the cables provided by the CATV system; the up link is a telephone connection to the head end. A router is connected to the down link by means of an RF modem, to the up link by means of an analog modem, and to a LAN which is connected to the Pcs. The router routes IP packets for the hosts that are received on the CATV cable to the hosts via the LAN; it routes IP packets from the hosts that are destined for the Internet to the head end via the telephone line. The asymmetrical network conserves IP addresses and addresses on the CATV cable by dynamically allocating the IP addresses for an RF modem's hosts and an address on the CATV cable for the RF modem in response to a request made by the RF modem via the telephone line.

Abstract: An embodiment includes an input node, a shunt impedance electrically connected to the input node, and at least one shunt diode connected in series with the shunt impedance. The input node receives an electrical signal from a signal generator. A bias current is applied to the shunt diode from a bias supply. In response, the shunt diode generates second-order distortion and substantially no third-order distortion. The level of bias current is adjusted to substantially eliminate any third-order distortion while the shunt impedance is adjusted so that the appropriate amount of second-order distortion is generated as predistortion. The predistortion is then provided to a nonlinear device, such as a laser, where it operates to substantially cancel inherent distortion generated by the nonlinear device.

Abstract: A communication system (100) processes forward signals generated by headend equipment (105) and reverse signals generated by subscriber equipment (135). A communication medium (110, 120), such as fiber optic cable or coaxial cable, couples the headend equipment (105) and the subscriber equipment (135), and amplifiers (400) are positioned at various locations along the medium (110, 120) to amplify the forward and reverse signals. The amplifiers (400) include a dual forward/reverse test circuit (FIG. 5) having a forward test point (406) coupled to the forward signal, a reverse test point (408) coupled to the reverse signal, and a single directional coupler (404) connected to the forward test point (406), for providing the forward signal thereto, and to the reverse test point (408), for providing the reverse signal thereto.

Abstract: A removable plug-in board for dividing incoming radio frequency (RF) to an external port and providing alternating current (AC) signals to a CATV system amplifier contains a radio frequency choke or inductor for passing the AC power signal, a high pass filter for passing the radio frequency signal and either a directional coupler or a splitter. This plug-in board is inserted into a motherboard on which is mounted amplification circuitry and power supply and divider circuitry. The plug-in board routes RF signals arriving on an input port of the amplifier motherboard through the directional coupler to the amplification circuitry, while additionally tapping off and feeding the incoming RF signals to a second output port of the amplifier motherboard.

Abstract: An interactive terminal comprises a processor, a local data store connected to the processor, a character generator responsive to processor control for generating a television signal output to an associated television receiver, a key pad or remote control for inputting information to the processor, and a power supply input. The terminal is coupled, via 2-way RF communications, to a central location, designated as the system manager, where the terminal is accessed by polling for monitoring and servicing terminal user requests. The interactive terminal has a local storage capacity for storing a number of character screen commands, accessed from a central data base at the system manager, for use in generating prompting screens displayed on the television receiver. In use, a user may call for a variety of services by operating the input keys of the key pad to cause a prompting screen to be displayed. Screen commands are stored at the terminal according to an assigned priority.

Abstract: Techniques for doing motion estimation in video encoding. A predictor block which is a best match for a current block is located by comparing the current block of the picture currently being encoded with candidate blocks that are located using the motion vectors of blocks that are either spatially or temporally proximate to the current block. If a given proximate block does not have a usable motion vector, another proximate block is used. The temporally proximate blocks are blocks in the last picture to be encoded prior to the current picture. The candidate blocks are further used to define a minimized portion of the search space which will fit inside the local RAM of the processor used to compare the current block with the candidates. The minimized search space is used in a two-phase method which begins with the candidates located using the proximate blocks and continues with a diamond-shaped search space centered on the best candidate located using the proximate blocks.

Abstract: A reconfigurable chassis provides thermal management of external electrical modules that are inserted into the chassis and removed from the chassis. The chassis includes a housing into which modules are inserted, and the housing has a front portion and a back portion and further has multiple guides for holding the modules. A removable fan tray is located on top of the housing. The removable fan tray holds fans in first and second positions, wherein, when the fans are located in the first position, air is directed from the front portion of the chassis, and wherein, when the fans are located in the second position, air is directed from the back portion of the chassis. The chassis also includes a removable rear connector panel for use when electrical cables coupled to the modules are to be accessed from the back portion of the housing. The removable rear connector panel is mounted to the back portion of the housing for electrically coupling to the electrical cables that are coupled to the modules.

Abstract: A highly stable soliton source uses a bulk Er/Yb glass laser which operates in two longitudinal modes of the laser cavity with substantially identical amplitudes to generate beat modulation. The beat modulation is then passed through a pulse compression fiber which compresses the beat modulation into a train of soliton pulses. Because the beat modulation is between two modes of the same laser cavity, the soliton pulse train generated is highly stable with low timing jitter.

Abstract: A video compression system comprises a control computer 52; a plurality of encoders 54, 56, 58; a plurality of encoder buffers 60, 62, 64; a multiplexor 66; a data channel 70; a demultiplexor 80; a decoder buffer 82; a decoder 84; and display 86. The control computer controls the encoders and the multiplexor 66 to avoid overflows and underflows of data provided to the decoder buffer 82.

Abstract: An optical transmitter (405) includes a distributed feedback semiconductor laser (100) operated in a linear regime below a threshold associated with stimulated Brillouin scattering to generate an optical signal. A resistor (125) or other heater is physically coupled to the semiconductor laser (100), and a modulated current source (120) drives the resistor (125) with a triangle waveform (300), thereby varying an optical wavelength of the optical signal such that the optical signal and a double Rayleigh backscattered signal are characterized, at the optical receiver (410), by different optical frequencies. As a result, interference generated by Rayleigh backscattering is minimized at the optical receiver (410).