Abstract: A scheme for configuring an FEC encoder (including an associated interleaver) for changing data channel characteristics. Channel information specifying a modulation mode and carriers capable of supporting the modulation mode for the data channel is received by a transmitting network node for use in a data transmission to a receiving network node. The received channel information is based on a prior data transmission to the receiving network node over the data channel. Configuration values are computed from the received channel information and an amount of data to be transmitted in a data transmission. The FEC encoder is configured to operate on the data transmission data amount according to the configuration information.

Abstract: A partial ARQ protocol for multicast and broadcast transmissions in network devices operating in a shared medium access network. To support the partial ARQ, a media access control (MAC) protocol uses robustly transmitted frame delimiters and a MAC management frame structure. In a multicast or broadcast frame with partial ARQ, a destination address field is set to that of a selected proxy device's address, and the address of the intended recipients (of group address of the intended recipients) is placed in an entry in the MAC management frame structure. The frame also contains a multicast flag set to indicate that the transmission is intended for more than one device and a value in the frame delimiters to indicate that a response is requested. Upon receipt of such a frame, the proxy device specified by the destination address field provides an appropriate response type on behalf of the group.

Abstract: A scheme for configuring an FEC encoder (including an associated interleaver) for changing data channel characteristics. Channel information specifying a modulation mode and carriers capable of supporting the modulation mode for the data channel is received by a transmitting network node for use in a data transmission to a receiving network node. The received channel information is based on a prior data transmission to the receiving network node over the data channel. Configuration values are computed from the received channel information and an amount of data to be transmitted in a data transmission. The FEC encoder is configured to operate on the data transmission data amount according to the configuration information.

Abstract: A scheme for identifying usable carriers for a particular modulation type and selecting, if possible, a modulation type for modulation of OFDM symbol block associated with data packets in a standard transmission mode based on data channel conditions. Channel estimation for an OFDM symbol block received by a receiving network node over a data channel during a packet transmission by a transmitting network node generates information indicative of noise events on symbols and carriers in the OFDM block, the generated information being related to modulation types available for the standard transmission mode, and determines from the generated information if at least one of the modulation types available for the standard transmission mode may be used for a next data transmission over the data channel by the transmitting network node using the standard transmission mode. One of the modulation types is selected if it is determined that at least one of the modulation types may be used.

Abstract: A scheme for configuring an FEC encoder (including an associated interleaver) for changing data channel characteristics. Channel information specifying a modulation mode and carriers capable of supporting the modulation mode for the data channel is received by a transmitting network node for use in a data transmission to a receiving network node. The received channel information is based on a prior data transmission to the receiving network node over the data channel. Configuration values are computed from the received channel information and an amount of data to be transmitted in a data transmission. The FEC encoder is configured to operate on the data transmission data amount according to the configuration information.

Abstract: An encoder/decoder scheme for robust transmission of PHY layer frame control information (to support medium access) in OFDM frames (or packets). The PHY layer frame control information to be modulated onto carriers in OFDM symbols is encoded using a product coding to form a product code block or matrix. The product coding is based on a shortened hamming code codeword set having properties of symmetry. Elements of the product code matrix are interleaved so that the elements are modulated onto the carriers of the symbols in diagonal groupings (across time and frequency) and with some degree of redundancy. The modulated elements are demodulated to produce soft decision values, which are de-interleaved to combine copies of the soft values for elements and re-order the soft values in the order of the elements prior to interleaving.

Abstract: An interleaving/de-interleaving scheme for providing redundancy with both time and frequency diversity to data in OFDM symbols in a data transmission system. On the transmit side, encoded data to be modulated onto carriers in OFDM symbols is interleaved by storing the encoded data in an interleaver memory and reading multiple copies of the encoded data from the interleaver memory so that the encoded data copies are spread in time on non-consecutive symbols and in frequency on non-adjacent carriers. On the receive side, the multiple copies of the OFDM data are received, and phase noise computations are used to combine the multiple copies (in either metric or phase angle form) into one. From the combined copies a single metric value to be used in decoding the OFDM data is produced.

Abstract: A windowing mechanism for processing an OFDM symbol is presented. The windowing mechanism applies an apodizing window function having the property Wj+W(FFTSize/2 +j)=constant, where FFTSize is the size of the FFT sample, to a received OFDM symbol sample and a time-offset version of the OFDM symbol sample to produce sets of windowed values. The time-offset sample is offset from the original symbol by one half the symbol period. The time-offset windowed sample is shifted into realignment with the windowed original symbol. Corresponding ones of the windowed values are summed together to restore the windowed symbol to its original form.

Abstract: A method is described for temporally aligning a received symbol that is transmitted via orthogonal channels, e.g., OFDM channels, with a reference symbol and/or an earlier received symbol. The method includes computing phases of the first symbol for the orthogonal transmission channels and comparing the computed phases of the first symbol with phases of the reference. The phases of the first symbol are successively displaced by a predetermined phase shift which depends on the channel frequency to obtain a correlation result. The temporal alignment is determined by detecting a correlation maximum based on the correlation result and used to synchronize the first symbol with the reference. The reference can also be an earlier received symbol to provide autocorrelation. The received symbols can be processed by applying a window function, e.g. a Hanning, Hamming or Blackman window.

Abstract: A mechanism for determining phases of a symbol for phase correlation is provided. The mechanism performs a symmetric apodizing window function on a symbol sample of a symbol having a symbol period of T and a time-offset symbol symbol sample offset from the symbol sample by T/2 to produce first windowed values for the symbol sample and second windowed values for the time-offset symbol sample. The mechanism applies a time shift to re-align the time-offset symbol sample with the symbol sample and sums the second windowed values and the corresponding first windowed values. The summed values are then converted to phases. The symmetric apodizing window function is an apodizing window function having the property W.sub.j +W.sub.(FFTSize,/2+j) =constant, where FFTSize is the size of the FFT sample. The symmetric apodizing window function, such as a Hanning window, may be performed in the time or frequency domain.

Abstract: An apparatus and methods are provided for network radio frequency ("RF") data communications. The apparatus preferably has an extended channel radio transmitter for selectively transmitting data communication radio signals across a plurality of different carrier frequencies which respectively define a plurality of extended data communication channels. The transmitter preferably includes a channel scanner for scanning the extended data communication channels for availability prior to transmitting across a selected one of the plurality of extended data communication channels. An extended channel radio receiver is responsive to the extended channel radio transmitter for receiving the data communication signals from the selected one of the extended data communication channels.

Abstract: A transversal adaptive finite impulse response (FIR) filter is modified for automatically filtering modulated signal components from a received signal based on frequency modulation rate. Coefficients of the filter are adapted to provide for filtering of signals having undesired modulation rates. The adapting operation includes selectively updating the coefficients using an error signal and iteratively decaying all the coefficients towards zero. The adaptation of the filter coefficients ensures symmetrical coefficient growth and introduces a constant group delay to the received signal to provide for filtering of complex signal components from a received signal according to frequency modulation rate without the use of a reference source.

Abstract: An apparatus and methods are provided for controlling data communications across power lines. The apparatus preferably has a power line interface for interfacing with a power line so as to detect both a wide bandwidth data communications protocol being initiated across the power line and a narrow bandwidth data communications protocol being initiated across the power line synchronously with the power line mains frequency and so as to initiate either a wide bandwidth data communications protocol onto the power line or a narrow bandwidth data communications protocol onto the power line synchronously with the power line mains frequency. The narrow bandwidth of the narrow bandwidth data communications protocol preferably falls within the wide bandwidth of the wide bandwidth data communications protocol. An input wide and narrow bandwidth protocol receiver is positioned responsive to the power line interface for receiving either the wide bandwidth protocol or the narrow bandwidth protocol.

Abstract: Spread spectrum chirps (i.e., wideband frequency packets) are propagated on a local area network in a hostile communications environment, such as a powerline or a crowded radio frequency band. Chirps are self-synchronizing, data bit (or subdata bit) in length and detectable by all network nodes, to allow the contention resolution and collision detection needed to support carrier-sense based network protocols. A matched filter of the same time length and encoding sequence as the transmitted chirp provides the self-synchronized chirp reception at each receiver.

Abstract: Spread spectrum communication using direct sequences that approximate a swept frequency waveform in which successive square waves are formed by the chips making up the sequence, and in which the durations of the square waves extend over a plurality of chips, and in which the frequency of the square waves varies across at least a portion of the sequence. Information is encoded by varying the direction of the direct sequence, so that the sequence is transmitted as either a forward or a reverse frequency-swept sequence. The spectrum of the direct sequences is in a passband. The direct sequence biphase modulates a carrier (e.g., RF) to produce a spread-spectrum signal with two passbands centered about the frequency of the modulated carrier.

Abstract: A method of transmitting and receiving data packets across a noisy communication medium, e.g., an AC power line. The data packets are transmitted using spread-spectrum chirps. A first sequence of the chirps forms a contention-resolution preamble used by transmitters to resolve conflicting contentions for access to the communication medium. The preamble is followed by a second sequence of chirps that form a start-of-packet symbol used by receivers to delineate the start of data within the packet. To simplify detection at the receiver, identical chirps are used in the preamble and the start-of-packet symbol. To enable the receiver to avoid erroneously interpreting preamble chirps as start-of-packet chirps, and thereby erroneously begin to accept packet data, chirps in the preamble are transmitted at a different pitch (i.e., different time period between inception of successive chirps) from chirps in the start-of-packet symbol.

Abstract: Communication apparatus and method that includes generating a series of successive spread-spectrum chirp signals, which are progressively swept within a defined bandwidth. The chirps are divided into two frequency-swept portions, one beginning at an intermediate frequency within the bandwidth being swept to one end of the frequency range of the chirp, and a second beginning at the other end of the frequency range and being swept to the intermediate frequency. This has the effect of moving the frequency transition from the boundaries of the chirp to its center, with the result that the discontinuities introduced at the boundaries by phase reversals due to successive modulated chirps generate less out-of-band energy.

Abstract: Spread spectrum chirps (i.e., wideband frequency packets) are propagated on a local area network in a hostile communications environment, such as a powerline or a crowded radio frequency band. Chirps are self-synchronizing, data bit (or subdata bit) in length and detectable by all network nodes, to allow the contention resolution and collision detection needed to support carrier-sense based network protcols. A matched filter of the same time length and encoding sequence as the transmitted chirp provides the self-synchronized chirp reception at each receiver.