Abstract: Wideband speech signals must be converted to narrowband speech signals if the transmission medium or the destination terminal is constructed with narrowband constraints. A typical wideband-to-narrowband conversion method is the elimination of frequencies above 3400 Hz using a low pass filter and a down sampler. However, this method produces a muffled speech sound since the resulting narrowband signal has a flat frequency response. Methods and apparatus are presented herein to enhance the acoustic quality of a wideband-to-narrowband converted signal. A bandwidth switching filter is used to emphasize a mid-range frequency portion of the wideband signal so that the resulting narrowband signal has a non-flat frequency spectrum.

Abstract: An optical distribution node is provided. The optical distribution node includes a laser transceiver that is coupleable to at least one fiber optic link. The optical distribution node communicates upstream and downstream digital data with the head end over the at least one fiber optic link. The optical distribution node further includes a data concentrator coupled to the laser transceiver. Further, for each of at least one coaxial cable link, the optical distribution node includes a frequency translator and a node modem. The frequency translator receives and translates the upstream digital data from modems on the at least one coaxial cable link to a different carrier to provide a signal to the modems on the at least one coaxial cable link for collision detection. The node modem is coupled between the coaxial cable link and the data concentrator. The node modem demodulates upstream digital data for the data concentrator and modulates downstream digital data for transmission over the coaxial cable link.

Abstract: An optical distribution node for an hybrid fiber/coax network is provided. The optical distribution node includes a laser transmitter coupleable to a fiber optic link that transmits upstream, digital data to a head end of the network. The node also includes a data concentrator coupled to provide the upstream, digital data to the laser. For at least one coaxial cable link of the network coupleable to the optical distribution node, the node also includes a frequency translator that receives the upstream, digital data modulated on a first carrier frequency and retransmits the upstream, digital data to the plurality of modems for collision detection. The node also includes a data interface coupled between the at least one coaxial cable link and the data concentrator that determines whether the upstream data is valid.

Abstract: An OFDM system embeds sequence information in the transmitted signal that reduces peak average power ratio (PAP) with minimal impact on the overall system efficiency. A marker is embedded onto the transmitted information that is used to identify the combining (inversion) sequence at the receiver. In one embodiment, selected tones in a cluster are rotated when the corresponding phase factor rotates the cluster.

Abstract: A method of transmitting data on multiple carriers is disclosed, the method consisting, on a transmitter side, of binary to signal coding of the data to be transmitted so as to form modulation signals, of modulating a plurality of sub-carriers with the modulation signals as to form symbols, referred to as OFDM symbols, and then of transmitting, over a channel between the transmitter and a receiver, the OFDM symbols at a rate which is related to a sampling frequency referred to as the transmitter sampling frequency, and, on the receiver side, of determining, from a clock signal at a frequency related to a sampling frequency referred to as the receiver sampling frequency, an analysis window for the signal received from the transmitter so as to form a block of samples, and of estimating the transmitted modulation signals by demodulating the sub-carriers for the block of samples under consideration.

Abstract: According to the invention, during the transmission of data by multi-carrier modulation, the data is combined to form blocks on the transmitter side and is modulated in blocks by Inverse Discrete Fourier Transformation (IDFT). Several carriers, which are not occupied by data, are reserved and these carriers are occupied in such a way as to generate a large amount of temporal functions, which after filtration exhibit Dirac-like characteristics. Said temporal functions are generated in such a way that the Dirac-like temporal functions obtained after filtration reach their maxima in an oversampled temporal resolution of different, preferably adjacent positions. Both the oversampled Dirac-like temporal functions after filtration and the corresponding filter input functions that have not been oversampled are stored and a pair is iteratively selected from the pairs of stored temporal functions or filter input functions.

Abstract: An average value of reception power of subcarriers A to D is calculated by a control circuit 162, and the average value is divided by envelops of received signals of subcarriers A to D, respectively, so as to calculate a coefficient signal of each subcarrier. Multipliers 106 to 109 multiply transmitting signals of subcarriers A to D output from mapping circuits 102 to 105 by the coefficient signals, respectively. Whereby, power between the subcarriers at a reception time can be maintained substantially constant so as to improve an error rate characteristic.

Abstract: A signal demultiplexer includes serially-connected 2-demultiplexing filter banks, including band-stop filters and down-samplers for culling sampling frequencies of output signals from filters to 1/2. When the 2-demultiplexing filter bank operates on four types of filters, first to fourth filters in an ascending order of frequencies, 2-demultiplexing filter bank is arranged in one of two configurations so that a first filter bank contains at least the first filter or the second filter, or a second filter bank contains at least the third filter or the fourth filter. The filter banks are connected in such a way that signals processed through the first filter are processed by the first 2-demultiplexing filter bank in a next-stage; signals processed through the second filter are processed by the second 2-demultiplexing filter bank in a next-stage.

Abstract: In a digital bus, such as the IEEE 1394 serial bus, the procedure for sending data from a link layer IC onto the data bus is that the link layer IC requests access to the bus and then waits until the physical layer IC grants the desired access. Upon detecting the grant status, the link layer IC is free to send data onto the bus. But if in the meantime the link layer IC refrains from sending data onto the bus, the granted bus access will not be given up. As a consequence the bus is blocked for an indefinite time period because the bus access granted cannot be overwritten by the physical layer IC. According to the invention an additional timer function is implemented in the link layer IC. This ‘bus grant missed’ timer function controls the link layer IC in such a way that it automatically gives back the bus control to the physical layer IC after a predetermined time period has elapsed during which the link layer IC has sent no data onto the bus.

Abstract: A translation apparatus retains a first correlation between a Mobile IPv6 terminal's home address and virtual IPv4 address. When the Mobile IPv6 terminal transmits a packet to said IPv6 network with a care-of address specified as the packet's source address and a home address specified in an extension header, the translation apparatus changes the packet's source address to a virtual IPv4 address that corresponds to the packet's home address in accordance with the first correlation, and then transmits the packet to an IPv4 network. Mobile IPv6 terminal-to-IPv4 terminal communication can then be established between an IPv6 network to which Mobile IPv6 terminals are connected and an IPv4 network to which IPv4 terminals are connected.

Abstract: A communication system such as an OFDM or DMT system has nodes which are allowed to transmit continuously on one or just a few of the sysiem's frequency sub-channels, while the other nodes avoid putting any signal into those sub-channels. Simple low data rate nodes are allowed to use a small number of sub-channels while more complicated nodes use the remainder, and preferably functionality is provided to ensure that adjacent sub-channels are reliably spaced apart in frequency so that they do not bleed over into one another; to ensure that signals from all nodes arrive at the base station with well-aligned symbol transitions; and to ensure that signals from the various nodes arrive at the base station with similar power levels.

Abstract: A method for transmitting data packets having a heading followed by a data field. The data of the field is transmitted by groups of symbols. According to the OFDM technique, subcarriers modulated by the groups are generated. A frequency modulation of a carrier signal delivered by a linear ramp generator is produced with a set of modulated subcarriers. When the signal is received, mixing with a linear ramp results in subcarriers which are separated and then demodulated for supplying data. This is useful for transmitting data packets particularly in wide band networks.

Abstract: A multi-carrier modulation apparatus to which transmultiplexers are applied. A multiplexing signal is treated as a synthesis of a plurality of multiplexed signals which are separated by a wider interval than the multiplexing frequency interval. Signals of channels 1 to M continuously frequency-multiplexed at a channel interval fB are treated as a synthetic signal of signals of channel 1 to channel 2N−1 and signals of channel 1 to channel 2N which are frequency-multiplexed at a channel interval 2fB. Individual multiplexed signals are synthesized by a plurality of transmultiplexers of less multiplexing number to make characteristics of polyphase filters required for the transmultiplexers less sharp.

Abstract: A network utilizing two or more wiring systems with a bridging function to provide a signal interconnect for communication within and between wiring systems. The bridging function can translate the network signals to a different frequency.

Abstract: An orthogonal frequency division multiplexed wideband communication system provides improved time and frequency synchronization by inserting an unevenly spaced pilot sequence within the constellation data. A receive correlates the received data using the unevenly spaced pilot sequence. The pilot sequence is generated with a maximum length pseudo random noise code and inserted into frequency bins having prime numbers.

Abstract: A method and apparatus for modulating a plurality of information signals onto respective unique intermediate frequency (IF) carrier signals, summing the respective IF carrier signals to provide a stacked IF carrier signal and upconverting the stacked IF carrier signal to a radio frequency (RF). Advantageously, the invention reduces the cost and complexity of modulation and frequency conversion processes in those systems requiring a multiplicity of audio, video or data carriers placed side by side or in a consecutive order within a defined frequency spectrum.

Abstract: A physical layer device (PHY) device in a home LAN employs discrete multitone technology (DMT). The DMT system enables usage of existing residential wiring, which typically is telephone system grade twisted copper pair. The PHY device comprises an analog front end (AFE) circuit that frequency shifts the spectral images by using a clock signal. The multiplication of the clock signal is accomplished using a digital mixer or, in the alternative, an analog switch.

Abstract: An intermediate repeater that can make available at least a minimum of information to the end user sites connected with it even in the event of a power failure. The intermediate repeater has a broadband amplifier (AMP) for the amplification of the received broadband signals and for the subsequent forwarding of the amplified broadband signals, as well as a first device (HP1, LP1; S1,LP, C1), which is connected in series to the broadband amplifier (AMP) and is set to separate the received narrow band signals from the received broadband signals according to frequency, and to forward them without amplification by bypassing the broadband amplifier (AMP). Thus, the transmission of the narrow band signals is guaranteed even during a disturbance.

Abstract: This invention relates to a method and apparatus for channel estimation. A method of determining a maximum likelihood frequency domain estimate of the channel response of a channel between at least one transmitting peer and at least one receiving peer, said method comprising transmitting NU reference tones from said transmitting peer to said receiving peer; capturing said NU reference tones at said receiving peer; and determining at said receiving peer from said NU reference tones said maximum likelihood frequency domain estimate of said channel response at NF predetermined frequencies by directly exploiting the finiteness of the time response of said channel.

Abstract: An average value of reception power of subcarriers A to D is calculated by a control circuit 162, and the average value is divided by envelops of received signals of subcarriers A to D, respectively, so as to calculate a coefficient signal of each subcarrier. Multipliers 106 to 109 multiply transmitting signals of subcarriers A to D output from mapping circuits 102 to 105 by the coefficient signals, respectively. Whereby, power between the subcarriers at a reception time can be maintained substantially constant so as to improve an error rate characteristic.

Abstract: We describe an improved method for decreasing the probability of an unacceptably high peak-to-average power ratio in a signal to be transmitted by a Frequency Division Multiplexing (FDM) system, such as a discrete multitone (DMT) system. The method involves generating at least two alternative signal sequences, computing Fourier transforms of the respective alternative signal sequences, and selecting for transmission one of these sequences, based on the Fourier transform computations. More specifically, the selection of one sequence may be based, e.g., on the determination that the Fourier transform of that sequence has an acceptable peak power. Alternatively, a comparison may be made among the Fourier transforms of the respective signal sequences, and selection made of that sequence whose Fourier transform exhibits the lowest peak power.

Abstract: A system for synchronizing a carrier frequency of an orthogonal frequency division multiplexing (OFDM) transmission apparatus, even when a carrier frequency offset is above a frequency bandwidth of one subchannel. The synchronization of the carrier frequency in the OFDM transmission apparatus is accomplished by alternating between a coarse mode for synchronizing an integer part of the carrier frequency offset and a fine mode for synchronizing a prime part of the carrier frequency offset.

Abstract: In the present invention, high speed data is provided by transmitting data on multiple carrier frequencies, multiple code channels and/or from multiple base stations. In a first embodiment of the present invention, multiplexed code symbols are transmitted on a plurality of carrier frequencies from the same base station. In second embodiment, code symbols are transmitted on multiple carrier frequencies with at least one corner frequency providing the code symbols is a multiple code channels. In a third embodiment, a subset of the multiplexed code symbols are redundantly provided on a different carrier from at least one additional base station. In a fourth embodiment, multiplexed symbols as transmitted on different carriers from the same base station and are redundantly transmitted on another set of carriers from a different base station. In a fifth embodiment, code symbols are multiplexed onto carriers from a plurality of base stations for increased throughput.

Abstract: A system for transporting radio frequency (RF) signals across a RF network comprises a central transport unit and a remote transport unit. The frequencies of at least some of the RF signals to be transported hop in accordance with predetermined hopping sequences. The central transport unit uses the hopping sequences to convert the hopping frequencies into fixed frequencies for efficient transport through the RF network. The remote transport unit uses the hopping sequences to convert the fixed frequencies back to the original hopping frequencies. The transport system is also capable of reverse operation in the direction from the remote transport unit to the central transport unit.

Abstract: CDMA (Code Division Multiple Access) communications systems and methods for performing a single to multiple frequency band conversion for mobile communications. The systems and methods include mixing a portion of a first CDMA signal in a first frequency band with a reference signal to convert a portion of the first CDMA signal to a second frequency band. The converted portion and the other portion of the first frequency band can then be transmitted. The systems and methods further include filtering a portion of a second CDMA signal having frequency components in multiple frequency bands to provide a filtered CDMA signal in the first frequency band. The filtered CDMA signal is then mixed to convert it to the second frequency band for receiver processing.

Abstract: The switchable dividing network includes two individual filters whose center frequencies are selected from the group consisting of f.sub.a /8, 3f.sub.a /8, 5f.sub.a /8 and 7f.sub.a /8. The passband of its transmission function is shiftable to other frequency ranges by changing signs of a few coupling devices.

Abstract: The spread spectrum communication system of the present invention is intended to equalize link capacity by taking deterioration of link quality so as to enable reliable communication which enhances the frequency diversity effect even if it is affected by the frequency selective fading or the like. Then, between a base station and a mobile station in a code division multiple access communication system which multiplexes the hopping frequencies by varying them with hopping series different for each channel, a same frequency band is used for a forward-link and a reverse-link, and the number of hopping frequencies and/or the number of hops per one data symbol being assigned is varied according to line quality. There is provided means for performing communication by multiplexing the forward- and reverse-links using the different hopping frequencies for transmission and receiving, so that the link capacity is equalized for the forward- and reverse-links.

Abstract: A wideband frequency signal digitizer and method for digitizing multiple bands of a wideband frequency signal. The digitizer and method providing for optimally positioning a segment (402) of the wideband frequency signal within a Nyquist band of an analog-to-digital converter. Remaining segments (402) of the wideband frequency signal are closely positioned relative to the first segment such that the entire wideband frequency signal (400) is easily digitized using a single or multiple analog-to-digital converters (36) while reducing or eliminating undesirable spurious signals.

Abstract: A digital data receiver having a converter for frequency conversion of the input high frequency digital orthogonal modulation signal in a fixed intermediate frequency band, a demodulator for orthogonally demodulating an intermediate frequency signal output from the conversion signal based on a fixed frequency, and a controller for matching a frequency of the oscillation signal to a central frequency of the intermediate frequency band based on a frequency control signal generated to perform an orthogonal detection process by the demodulator. The central frequency of the oscillation signal is offset to correspond to a carrier frequency of the digital data orthogonal modulation signal in the state that a plurality of digital orthogonal modulation signal is frequency division multiplexed in the intermediate frequency band.