Abstract: An improved Nyquist filter can be used as a matched filter in a digital communications system. This filter is characterized in that the frequency domain response meets the Nyquist criteria and that the square root of the frequency domain response has a first derivative that is continuous at all points. In other embodiments, the square root of the frequency domain response continuous over all points for all higher order derivatives.

Abstract: Efficient usage of available spectrum is increased by logically dividing government licensed frequency channels into sub-channels, each of which can individually transmit a signal between a base unit and terminal. The sub-channels are each offset from the center of the frequency channel by a unique offset amount to avoid interference. Power control, sub-channel interference cancellation, and frequency control are employed to minimize the effects of out-of-band sub-channel signals on adjacent sub-channels. Any given sub-channel can be dynamically configured to transmit voice or data signals. Further spectral efficiency is realized using time division multiplexing on some or all of the sub-channels.

Abstract: Channel induced distortion is cancelled from a QAM or similarly modulated signal that has both a signal component and a distortion component. Using digital signal processing, the information component of the received signal is removed by canceling magnitude variations arising from the information content. This is accomplished by normalizing the received signal to the magnitude value of one ring on the QAM constellation. Once the distortion component of the received signal is reconstructed, a compensation factor can be derived and applied to the received signal in order to remove the effects of the channel distortion prior to further processing and decoding of the received signal.

Abstract: An improved Nyquist filter can be used as a matched filter in a digital communications system. This filter is characterized in that the frequency domain response meets the Nyquist criteria and that the square root of the frequency domain response has a first derivative that is continuous at all points. In other embodiments, the square root of the frequency domain response continuous over all points for all higher order derivatives.

Abstract: In method of communicating from a terminal unit to a base unit, an incoming signal is sent from the base unit and received at the terminal unit. The terminal unit will measure the level of this incoming signal. The terminal unit may also extract digital information from the incoming signal. Based on either the measured signal level, the extracted information or both, the terminal will calculate an output power level to use in transmitting a signal back to the base unit. An outgoing signal can then be transmitted from the terminal unit using the output power level.

Abstract: Efficient usage of available spectrum is increased by logically dividing government licensed frequency channels into sub-channels, each of which can individually transmit a signal between a base unit and terminal. The sub-channels are each offset from the center of the frequency channel by a unique offset amount to avoid interference. Power control, sub-channel interference cancellation, and frequency control are employed to minimize the effects of out-of-band sub-channel signals on adjacent sub-channels. Any given sub-channel can be dynamically configured to transmit voice or data signals. Further spectral efficiency is realized using time division multiplexing on some or all of the sub-channels.