Abstract: A fixed wireless system (FWS) utilizing Orthogonal Frequency Division Multiplexing (OFDM) communication techniques is spectrally efficient and responsive to communications involving both voice and high speed data, such as Internet data. The FWS includes a wireless base unit; a plurality of fixed wireless remote units; a plurality of wireless data traffic channels available between the wireless base unit and the plurality of fixed wireless remote units; and a plurality of wireless voice traffic channels available between the wireless base unit and the plurality of fixed wireless remote units. Each wireless traffic channel is identifiable by a unique combination of frequency and time slots. Each wireless data traffic channel is used for carrying high speed data in addressed data packets to and from the plurality of fixed wireless remote units.

Abstract: Automatic gain control (AGC) methods and apparatus suitable for use in orthogonal frequency division multiplexing (OFDM) receivers are described. One AGC method includes the steps of repeatedly performing a first AGC process which adjusts amplifier gain based on determining that a signal level of multiple time sample values is outside a limit set by a first predefined threshold; and repeatedly performing a second AGC process which adjusts the amplifier gain based on determining that a signal level of multiple frequency sample values associated with a plurality of pilot tones is outside a limit set by a second predefined threshold. Preferably, the first AGC process is performed repeatedly at a first rate and the second AGC process is performed repeatedly at a second rate that is less than the first rate.

Abstract: A method, apparatus and system detects a loss of synchronization between a transmitter and a receiver in a multiple-carrier communication system such as an OFDM system. A phase-frequency synchronization detector determines when the receiver has lost synchronization with the transmitter based on a phase-frequency relationship of plurality of pilot signals transmitted at different frequencies from the transmitter and received at the receiver. A loss of synchronization is detected when a slope of a line defined by the phase-frequency relationship exceeds a timing threshold more at a rate in excess of an occurrence threshold within a time period.

Abstract: A method, apparatus and system detects a loss of synchronization between a transmitter and a receiver in a multiple-carrier communication system such as an OFDM system. A plurality of synchronization indicators are observed to determine whether a loss of synchronization between a transmitter and a receiver in the wireless system has occurred. In one embodiment, the receiver is determined to have lost synchronization with the transmitter if two or more of the three synchronization indicators indicate a loss of synchronization. In such an embodiment, the three synchronization indicators include a timing error indicator, an energy guard band indicator and a phase-frequency slope indicator.

Abstract: An orthogonal frequency division multiplexing (OFDM) communication system includes base units which simultaneously transmit pilot tones in a predetermined pilot tone pattern during one or more time slots of a message slot. OFDM signals are received within a time slot; an OFDM signal level is determined at each frequency of a plurality of pilot tone frequencies; the signal levels and the predetermined pilot tone pattern are correlated; and a pattern detection value based on performing the correlation is generated and stored. This process is repeated for each time slot of a plurality of time slots. This process may be repeated for a plurality of message frame durations to produce a plurality of averaged pattern detection values, following which the plurality of averaged pattern detection values and a predetermined message frame pattern may be correlated. Then, a boundary of a message slot may be detected based on the correlation.

Abstract: A frequency correction process involves the steps of generating a plurality of tone values for a plurality of tone bins, where the plurality of tone bins includes a first set of tone bins assigned to a first frequency range and a second set of tone bins assigned to a second frequency range; performing complex conjugate multiplication between the tone values of the first and the second sets of tone bins; identifying a maximum value from results of the complex conjugate multiplication; and shifting receiver frequency based on a location of the maximum value relative to a predetermined pilot tone location.

Abstract: An iterative method involves performing a coarse frequency correction process which adjusts receiver frequency so that a pilot tone signal is within a predetermined frequency range and, after performing the coarse frequency correction process, performing a fine frequency correction process which adjusts receiver frequency so that the pilot tone signal is substantially aligned with a pilot tone reference within the predetermined frequency range. By performing these processes, the receiver frequency may be adjusted so that the alias pilot tone signal is substantially aligned with the pilot tone reference and the pilot tone signal is undesirably shifted outside the predetermined frequency range. To eliminate this condition, the method further involves performing the coarse frequency correction process again and, after performing the coarse frequency correction process again, performing the fine frequency correction process again.

Abstract: Automatic gain control (AGC) methods and apparatus suitable for use in orthogonal frequency division multiplexing (OFDM) receivers are described. One AGC method includes the steps of repeatedly performing a first AGC process which adjusts amplifier gain based on determining that a signal level of multiple time sample values is outside a limit set by a first predefined threshold; and repeatedly performing a second AGC process which adjusts the amplifier gain based on determining that a signal level of multiple frequency sample values associated with a plurality of pilot tones is outside a limit set by a second predefined threshold. Preferably, the first AGC process is performed repeatedly at a first rate and the second AGC process is performed repeatedly at a second rate that is less than the first rate.

Abstract: Automatic gain control (AGC) methods and apparatus suitable for use in orthogonal frequency division multiplexing (OFDM) receivers are described. One AGC method includes the steps of repeatedly performing a first AGC process which adjusts amplifier gain based on determining that a signal level of multiple time sample values is outside a limit set by a first predefined threshold; and repeatedly performing a second AGC process which adjusts the amplifier gain based on determining that a signal level of multiple frequency sample values associated with a plurality of pilot tones is outside a limit set by a second predefined threshold. Preferably, the first AGC process is performed repeatedly at a first rate and the second AGC process is performed repeatedly at a second rate that is less than the first rate.

Abstract: Automatic gain control (AGC) methods and apparatus suitable for use in orthogonal frequency division multiplexing (OFDM) receivers are described. One AGC method includes the steps of repeatedly performing a first AGC process which adjusts amplifier gain based on determining that a signal level of multiple time sample values is outside a limit set by a first predefined threshold; and repeatedly performing a second AGC process which adjusts the amplifier gain based on determining that a signal level of multiple frequency sample values associated with a plurality of pilot tones is outside a limit set by a second predefined threshold. Preferably, the first AGC process is performed repeatedly at a first rate and the second AGC process is performed repeatedly at a second rate that is less than the first rate.

Abstract: A method, apparatus and system detects a loss of synchronization between a transmitter and a receiver in a multiple-carrier communication system such as an OFDM system. A guard band synchronization detector provides a synchronization indicator based on the energy detected within a guard band where a pilot tone is transmitted adjacent to the guard band. A timing error results in energy leakage into one or more guard bands. In one embodiment, a plurality of synchronization indicators are observed to determine whether a loss of synchronization between a transmitter and a receiver in the wireless system has occurred.

Abstract: Automatic gain control (AGC) methods and apparatus suitable for use in orthogonal frequency division multiplexing (OFDM) receivers are described. One AGC method includes the steps of repeatedly performing a first AGC process which adjusts amplifier gain based on determining that a signal level of multiple time sample values is outside a limit set by a first predefined threshold; and repeatedly performing a second AGC process which adjusts the amplifier gain based on determining that a signal level of multiple frequency sample values associated with a plurality of pilot tones is outside a limit set by a second predefined threshold. Preferably, the first AGC process is performed repeatedly at a first rate and the second AGC process is performed repeatedly at a second rate that is less than the first rate.