Abstract: A wireless broadband communications system that provides increased reliability in environments in which portions of the available operating frequency band are subject to interference. The system determines whether the operating frequency band is being subjected to interference. If so, then the system determines whether such interference is affecting one or more portions of the band. If interference is affecting just portions of the band, then the system reduces the data rate and the number of sub-carriers used to transmit data. Next, the system allocates the data to be transmitted to the sub-carriers currently being subjected to the lowest levels of interference, while allocating no data to the sub-carriers currently being subjected to the highest levels of interference. In this way, the system allocates the data to be transmitted to the sub-carriers occupying optimal portions of the operating frequency band, in response to detected changes in the interference environment.

Abstract: A wireless broadband communications system that can maintain high data rates while taking into account channel interference resulting from operating in shared frequency bands, signal fading resulting from dynamic channel degradation, and signal distortion resulting from compliance with maximum power output regulations. In one mode of operation, the system performs adaptive modulation by transmitting a first signal over a selected channel using a first modulation mode having a level of distortion associated therewith resulting from operating the system at a predetermined maximum power output level. Next, a SINAD level is measured on the first channel. The level of distortion associated with the first modulation mode is then subtracted from the measured SINAD level to obtain a first noise level.

Abstract: A wireless broadband communications system that provides increased reliability in environments in which portions of the available operating frequency band are subject to interference. The system determines whether the operating frequency band is being subjected to interference. If so, then the system determines whether such interference is affecting one or more portions of the band. If interference is affecting just portions of the band, then the system reduces the data rate and the number of sub-carriers used to transmit data. Next, the system allocates the data to be transmitted to the sub-carriers currently being subjected to the lowest levels of interference, while allocating no data to the sub-carriers currently being subjected to the highest levels of interference. In this way, the system allocates the data to be transmitted to the sub-carriers occupying optimal portions of the operating frequency band, in response to detected changes in the interference environment.

Abstract: A wireless broadband communications system that can transmit signals over communications links with multiple modes of diversity, thereby allowing signals having very low correlation to propagate over the link along multiple orthogonal paths. The system can be implemented as a non-line-of-sight (NLOS) system or a line-of-sight (LOS) system. The NLOS system employs orthogonal frequency division modulation (OFDM) waveforms to reduce multi-path interference and frequency selective fading, adaptive modulation to assure high data rates in the presence of channel variability, and spectrum management to achieve increased data throughput and link availability. The LOS system employs space-time coding and spatial and polarization diversity to minimize ground bounce nulls. The system achieves levels of link availability, data throughput, and system performance that have heretofore been unattainable in wireless broadband communications systems.

Abstract: A wireless broadband communications system that increases data throughput and link availability through more efficient use of the electromagnetic spectrum allocated to the system. In one mode of operation, the system periodically measures a noise or interference level associated with each one of a plurality of communications channels, and generates a histogram of the measurements associated with each channel. Next, the system determines a noise/interference level estimate for each channel as a predetermined percentile of the histogram associated with the respective channel. The system then selects a respective one of the channels having the lowest noise/interference level estimate for subsequent signal transmission.

Abstract: Techniques for facilitating and reducing the costs associated with the installation of a wireless broadband communications system. In one mode of operation, the system employs a first transceiver to identify n channels having the n lowest levels of noise and interference associated therewith by a spectrum management technique. Next, the first transceiver transmits a predetermined code over the n channels to a second transceiver, which attempts to identify the predetermined code within a captured transmission. In the event the code is correctly identified, the second transceiver measures a noise and/or interference level associated with the corresponding channels. The channel having the lowest measured noise and interference level is then selected for use in system installation.