US 8,638,655 B2 · Systems and method for orthogonal frequency divisional multiplexing

Abstract

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 to produce a receiver output; 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; the processor coupled to the receiver, wherein the processor applies a Fourier transform to the receiver output; and a controller programmed to instruct the transmitter to transmit at least one symbol representing a request for bandwidth allocation on a first carrier; wherein the controller is further programmed to determine when a collision has occurred on the first carrier.

Claims33

Dependent claims

A remote unit using frequency guard bands in a multipoint-to-point communication system in which orthogonal frequency division multiplexed carriers are used for carrying upstream and downstream communications, and in which more than one remote unit, after receiving allocations of orthogonal frequency division multiplexed carriers for upstream communications, may transmit upstream communications that are received at a host at the same time, the remote unit comprising:

a radio frequency receiver communicatively coupled with the host unit, the radio frequency receiver receiving downstream communications carried on orthogonal carriers;
a radio frequency transmitter communicatively coupled with the host unit in a multipoint-to-point configuration, the radio frequency transmitter configured to transmit upstream payload communications using orthogonal carriers allocated by the host;
the radio frequency transmitter including at least one converter that generates an analog signal based on a stream of time domain in-phase and quadrature phase data, wherein the radio frequency transmitter transmits the analog signal using orthogonal carriers;
a multi-carrier modulator coupled to the radio frequency transmitter and configured to modulate upstream payload data onto orthogonal carriers;
wherein the multi-carrier modulator is synchronized with the host unit such that when orthogonal carriers from the remote unit are received at the host at the same time as orthogonal carriers from at least one other remote unit, the orthogonal carriers from the remotes are substantially orthogonal to each other when received at the host unit;
wherein the multi-carrier modulator further includes:
at least one symbol mapper that maps payload data into symbols using quadrature amplitude modulation (QAM) symbol mapping and phase-shift keying (PSK) symbol mapping;
and
a Fast Fourier Transform (FFT) engine that receives parallel data inputs derived from the symbol data generated by the symbol mapper, the Fast Fourier Transform (FFT) engine generating time domain in-phase and quadrature phase data;
and
wherein the remote transmits a non-payload signal separated from payload bearing carriers of another remote unit by a frequency guard band.

8 more elements

A method for a host unit in a multipoint-to-point communication system using frequency guard bands, and in which orthogonal frequency division multiplexed carriers are used for carrying upstream communications, and in which more than one remote unit, after receiving allocations of orthogonal frequency division multiplexed carriers for upstream communications, may transmit upstream communications that are received at a host at the same time, the method for the host unit comprising:

receiving from a remote a non-payload signal separated from payload bearing carriers of another remote unit by a frequency guard band;
transmitting to a remote unit allocations of orthogonal frequency division multiplexed carriers for upstream communications;
after receiving the non-payload signal, transmitting synchronizing information to the remote unit such that when payload bearing orthogonal carriers from the remote unit are received at the host at the same time as payload bearing orthogonal carriers from at least one other remote unit, the orthogonal carriers from the remotes are substantially orthogonal to each other when received at the host unit;
after transmitting synchronizing information, receiving upstream payload communications carried on orthogonal frequency division multiplexed carriers allocated by the host that are synchronized to orthogonally arrive at the host with simultaneously received upstream payload communications carried on orthogonal frequency division multiplexed carriers from at least one other remote unit.

1 more element

Dependencies are inferred from the claim text.

Systems and method for orthogonal frequency divisional multiplexing

Life of this patent

Systems and method for orthogonal frequency divisional multiplexing

Life of this patent

Abstract

Claims33