摘要:
Systems and methods for orthogonal frequency division multiplexing are provided. In one embodiment, a multi-carrier modem comprising: a receiver configured to de-modulate symbols from at least one of a plurality of spectrally overlapping carrier signals; a transmitter configured to modulate symbols onto at least one of a plurality of the spectrally overlapping carrier signals; a processor coupled to the transmitter, wherein the processor outputs data for transmission by the transmitter, wherein the processor applies an inverse Fourier transform to the data transmitted by the transmitter; and a controller programmed to instruct the transmitter to transmit a coarse timing adjustment followed by at least one secondary timing adjustment, wherein the secondary timing adjustment is a fine tuning adjustment with respect to the coarse timing adjustment.
摘要:
Systems for tone hopping in a multipoint-to-point orthogonal frequency division multiplexing (OFDM) communication system are provided. In one embodiment, a bidirectional communication system comprises: a first remote unit for communicating with a host unit using OFDM, the host unit communicatively coupled to a plurality of remote units in a multipoint-to-point configuration; the first remote unit including a modulator for modulating up to a plurality of tones with upstream information using orthogonal frequency division multiplexing, wherein the modulator is configured to adjust at least one characteristic of the plurality of tones such that when any tones are transmitted from the first remote unit and at least one other remote unit of the plurality of remote units, the orthogonality of the tones when received at the host unit is improved. The first remote unit switches modulation between tones of the plurality of tones to reduce the impact of using any corrupted tones.
摘要:
Systems for tone allocation are provided. In one embodiment, a system comprises: a plurality of remote units and a host including a demodulator. Each remote transmits an upstream OFDM signal using a multiple access scheme to the host using an OFDM waveform. The host receives the upstream OFDM signals, the tones of the upstream signals substantially orthogonal when received at the host. Portions of upstream OFDM signals from at least two remotes arrive at the host at the same time. The host demodulates said portions. At least one remote transmits to the host using a first tone allocated by the host. The host sends an adjustment signal to the remote to adjust the timing of transmissions to improve orthogonality of the OFDM waveform. After the remote has begun transmission using the first tone but before the remote has completed its transmission, the host allocates to the remote a different tone.
摘要:
Systems and methods for orthogonal frequency division multiplexing are provided. In one embodiment, a multi-carrier modem comprises: a receiver configured to de-modulate symbols from at least one of a plurality of spectrally overlapping carrier signals; a transmitter configured to modulate symbols onto at least one of a plurality of the spectrally overlapping carrier signals; a processor coupled to the transmitter, wherein the processor outputs data for transmission by the transmitter, wherein the processor applies an inverse Fourier transform to the data transmitted by the transmitter; and a controller programmed to instruct a transmitter to transmit one or more timing adjustments to at least one of the plurality of remote units based on detected variations in transmissions received from the at least one of the plurality of remote units.
摘要:
Methods for multiple use subchannels are provided. In one embodiment, a method for an orthogonal frequency division multiplexing (OFDM) multipoint-to-point communications system comprises: establishing communication between a first remote unit of a plurality of remote units and a host unit, the plurality of remote units communicatively coupled to the host unit in a multipoint-to-point configuration; transmitting up to a plurality of tones from the first remote unit, the up to a plurality of tones modulated with upstream information using OFDM; adjusting a carrier frequency of the up to a plurality of tones such that when any tones are transmitted from a first remote unit and a least one other remote unit, the orthogonality of the tones when received at the host unit is improved; and transmitting both control data and payload data on at least one of the up to a plurality of tones from the first remote unit.
摘要:
Systems and methods for bidirectional communication are provided. In one embodiment, a multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system comprises: a plurality of remote units, a host unit; wherein the host sends an adjustment signal to a remote instructing the remote to adjust the timing of transmissions from the remote to improve orthogonality of the OFDM waveform received at the host, wherein the host sends an adjustment signal to a remote instructing the remote to adjust the frequency of transmissions from the remote to improve orthogonality of the OFDM waveform received at the host, wherein payload data is transmitted between a remote and the host over a first orthogonal tone within the OFDM communication system during a first time interval, and wherein control data is transmitted between a remote and the host over the first orthogonal tone within the OFDM communication system during a second time interval.
摘要:
A power line based communication system includes a power line termination module, a plurality of power line gateways, and a plurality of power line nodes. The power line termination module manages data for local area networks within the power line based communication system. The plurality of power line gateways is arranged in sets of power line gateways, wherein each set of power line gateways constitutes a local area network. Each of the plurality of power line nodes is operably coupled to the power line termination module via a high-speed communication path. In addition, each power line node is operably coupled to set of power line gateways, i.e., to a local area network, via power lines of a local transformer. Each of the power line nodes receives data for its respective LAN from the power line termination module and provides the data to the power line gateways of its LAN via the power lines of the local transformer. Virtual local area networks are enabled between the power line termination module and the power line gateways.
摘要:
A power line based communication system includes a power line termination module, a plurality of power line gateways, and a plurality of power line nodes. The power line termination module manages data for local area networks within the power line based communication system. The plurality of power line gateways is arranged in sets of power line gateways, wherein each set of power line gateways constitutes a local area network. Each of the plurality of power line nodes is operably coupled to the power line termination module via a high-speed communication path. In addition, each power line node is operably coupled to set of power line gateways, i.e., to a local area network, via power lines of a local transformer. Each of the power line nodes receives data for its respective LAN from the power line termination module and provides the data to the power line gateways of its LAN via the power lines of the local transformer. Virtual local area networks are enabled between the power line termination module and the power line gateways.
摘要:
A system is described which provides bidirectional transport of data at different data rates for each direction over a shared medium. In one embodiment, the different data rates are accomplished using different modulation techniques. For example, in the downstream direction, quadrature amplitude modulation (QAM) 64 is used and in the upstream direction orthogonal frequency division multiplexing (OFDM) is used. The QAM 64 modulation provides for a higher number of bits per hertz in a transmission channel. By using QAM 64 modulation, down stream transmission rates on the order of 30 megabits per second (Mbps) in a 6 MHz channel can be achieved. A number of 6 MHz channels can be combined to provide for even higher data rates.
摘要:
A power line based communication system includes a power line termination module, a plurality of power line gateways, and a plurality of power line nodes. The power line termination module manages data for local area networks within the power line based communication system. The plurality of power line gateways is arranged in sets of power line gateways, wherein each set of power line gateways constitutes a local area network. Each of the plurality of power line nodes is operably coupled to the power line termination module via a high-speed communication path. In addition, each power line node is operably coupled to set of power line gateways, i.e., to a local area network, via power lines of a local transformer. Each of the power line nodes receives data for its respective LAN from the power line termination module and provides the data to the power line gateways of its LAN via the power lines of the local transformer. Virtual local area networks are enabled between the power line termination module and the power line gateways.