Abstract: In method for facilitating the more efficient opportunistic use of one or more frequency division multiplexed (FDM) channels by a two or more secondary users (SU) in a point-to-multipoint, centralized ad hoc network, one SU acts as a central node and the remaining SU acting as remote nodes. Each SU adheres to a predetermined protocol utilizing synchronized time slots in each of the channels, each time slot having at least one data transmission period and at least one primary user detection period during which no SU transmits. The central SU node determines channel availability.

Abstract: Improvements for radios for communications between an end of train unit to a head of train that allows for simultaneous reception of messages on any one of three RF link types, for example, Association of American Railroads (AAR) S-9152 RF links in the 450 MHz band, ITCR (Interoperable Train Control Radio) links in the 220 MHz band, and RF links in the 450 MHz band using a higher-order modulation and coding scheme than provided by S-9152.

Abstract: A radio for determining the occupancy of a variable width channel for secondary use, the variable width channel with a bandwidth equal to an integer multiple of the bandwidth of a plurality of narrowband channels in an RF frequency band. The radio decides whether the variable width channel in the RF band is occupied by whether classifying each of the narrowband channels corresponding to the variable width channel and each of a plurality of sub-bands with bandwidths of narrowband channels but center frequencies shifted by one-half of the bandwidth of the narrowband channel and overlap with the bandwidth of the variable width channel as containing signal or noise based on measured energy levels.

Abstract: A radio for determining the occupancy of a variable width channel for secondary use, the variable width channel with a bandwidth equal to an integer multiple of the bandwidth of a plurality of narrowband channels in an RF frequency band. The radio decides whether the variable width channel in the RF band is occupied by whether classifying each of the narrowband channels corresponding to the variable width channel and each of a plurality of sub-bands with bandwidths of narrowband channels but center frequencies shifted by one-half of the bandwidth of the narrowband channel and overlap with the bandwidth of the variable width channel as containing signal or noise based on measured energy levels.

Abstract: A method for facilitating the more efficient opportunistic use of one or more frequency division multiplexed (FDM) channels in a frequency band by a group of two or more secondary users (SU) that have formed a point-to-multipoint, centralized ad hoc network, with one SU acting as a central node and the remaining SU acting as remote nodes. Each SU adheres to a predetermined protocol utilizing synchronized time slots in each of the channels being used by the network, each time slot having at least one data transmission period and at least one primary user detection period during which no SU transmits. The central SU node determines channel availability. Remote SU nodes may listen for primary user transmissions in a channel and inform the central SU node of detected activity. Remote nodes contend for transmission during a data transmission period of a time slot unless the channel has been reserved by a remote node after successful transmission in the data transmission period of a preceding time slot.

Abstract: A railroad communication system includes a radio transmitter for generating radio communications signals and a length of railroad rail coupled to the radio transmitter. The length of rail is disposed on a set of nonconductive railroad ties to form a transmission line for radiating the radio communications signals to a radio receiver in a vicinity of the length of railroad rail.

Abstract: A cabinet capable of attenuating or blocking wireless signals contains, a medical device, such as an AED, an internal directional antenna mounted to an internal surface of the cabinet, an external omnidirectional antenna mounted to an external surface of the cabinet, and an electrical connection between the internal directional antenna and the external omnidirectional antenna. The internal and external antennas are configured to transmit wireless signals at particular frequencies and to receive wireless signals at the particular frequencies. The internal antenna is a high gain directional antenna, and the external antenna is a lower gain omnidirectional antenna.

Abstract: A method of linearizing a relationship between a signal to an amplifier and an output signal from the amplifier includes applying an inverse of a transfer function of the amplifier to the signal prior to presenting the signal as the amplifier input. The inverse transfer function is represented by a polynomial defined by a set of coefficients. The transmitter output signal is measured by the idle receiver in a time division duplex system. The output signal is filtered to isolate intermodulation products of a selected order and the peak power of the isolated intermodulation products is then estimated. An adaptive algorithm is applied in response to the estimate of the peak power to update the set of coefficients of the polynomial representing the inverse of the transfer function of the amplifier.

Abstract: A railroad communication system includes a radio transmitter for generating radio communications signals and a length of railroad rail coupled to the radio transmitter. The length of rail is disposed on a set of nonconductive railroad ties to form a transmission line for radiating the radio communications signals to a radio receiver in a vicinity of the length of railroad rail.

Abstract: A railroad communication system includes a radio transmitter for generating radio communications signals and a length of railroad rail coupled to the radio transmitter. The length of rail is disposed on a set of nonconductive railroad ties to form a transmission line for radiating the radio communications signals to a radio receiver in a vicinity of the length of railroad rail.

Abstract: A method of linearizing a relationship between a signal to an amplifier and an output signal from the amplifier includes applying an inverse of a transfer function of the amplifier to the signal prior to presenting the signal as the amplifier input. The inverse transfer function is represented by a polynomial defined by a set of coefficients. The transmitter output signal is measured by the idle receiver in a time division duplex system. The output signal is filtered to isolate intermodulation products of a selected order and the peak power of the isolated intermodulation products is thenestimated. An adaptive algorithm is applied in response to the estimate of the peak power to update the set of coefficients of the polynomial representing the inverse of the transfer function of the amplifier.

Abstract: A cabinet capable of attenuating or blocking wireless signals contains, a medical device, such as an AED, an internal directional antenna mounted to an internal surface of the cabinet, an external omnidirectional antenna mounted to an external surface of the cabinet, and an electrical connection between the internal directional antenna and the external omnidirectional antenna. The internal and external antennas are configured to transmit wireless signals at particular frequencies and to receive wireless signals at the particular frequencies. The internal antenna is a high gain directional antenna, and the external antenna is a lower gain omnidirectional antenna.

Abstract: A method of linearizing a relationship between a signal to an amplifier and an output signal from the amplifier includes applying an inverse of a transfer function of the amplifier to the signal prior to presenting the signal as the amplifier input. The inverse transfer function is represented by a polynomial defined by a set of coefficients. The transmitter output signal is measured by the idle receiver in a time division duplex system. The output signal is filtered to isolate intermodulation products of a selected order and the peak power of the isolated intermodulation products is then estimated. An adaptive algorithm is applied in response to the estimate of the peak power to update the set of coefficients of the polynomial representing the inverse of the transfer function of the amplifier.

Abstract: A railroad communication system includes a radio transmitter for generating radio communications signals and a length of railroad rail coupled to the radio transmitter. The length of rail is disposed on a set of nonconductive railroad ties to form a transmission line for radiating the radio communications signals to a radio receiver in a vicinity of the length of railroad rail.

Abstract: A method of supporting voice-band modem-to-modem calls in a wireless communication system is disclosed. In some embodiments, once a modem call is detected, the modem call is terminated. Data in the terminated modem call is then demodulated and relayed from one end of a wireless broadband channel to the other end of the wireless broadband channel. Transfer of the data to the second modem is completed when the other end of the wireless broadband channel places a modem call to the second modem. By sending data in high-rate modem calls via a wireless broadband channel rather than over multiple, dedicated wireless voice channels, resources of the wireless communication system are utilized more efficiently that can result in significant gains in system capacity.

Abstract: A method of supporting voice-band modem-to-modem calls in a wireless communication system is disclosed. In some embodiments, once a modem call is detected, the modem call is terminated. Data in the terminated modem call is then demodulated and relayed from one end of a wireless broadband channel to the other end of the wireless broadband channel. Transfer of the data to the second modem is completed when the other end of the wireless broadband channel places a modem call to the second modem. By sending data in high-rate modem calls via a wireless broadband channel rather than over multiple, dedicated wireless voice channels, resources of the wireless communication system are utilized more efficiently that can result in significant gains in system capacity.

Abstract: A system for receiving a communication signal includes an antenna that can be coupled to a subscriber terminal, a compass secured to the antenna, the compass adapted to measure an orientation of the antenna, a memory unit for storing data associated with a desired mounting configuration of the antenna, and a processor, the processor configured to generate a signal based on the measured orientation and the data stored in the memory unit. A device for installing an antenna includes a structure attachable to the antenna, a compass secured to the structure, the compass adapted to measure an orientation of the antenna, a memory unit for storing data associated with a desired mounting configuration of the antenna, and a processor, the processor configured to generate a signal based on the measured orientation and the data stored in the memory unit.

Abstract: A system and method are provided for controlling the gain of signals transported over transmission media in a distributed antenna network. The system includes a plurality of remote antenna units where each remote antenna unit includes a signal level comparator for comparing the level of the signals received by the respective antenna unit with a predetermined reference level, and a gain controller for reducing the gain of the remote antenna unit when the signal level comparator determines that the level of the received signal exceeds said predetermined reference level. The system may accommodate TDMA systems when a gain controller is used that is fast enough to respond within the time slots of the received signals. As a result, the signal levels output from the remote antenna units are prevented from exceeding a maximum signal level.

Abstract: A communications system and method are provided for reducing noise in a distributed antenna network. The system includes a plurality of remote antenna units with each remote antenna unit including a receiver for receiving input signals, a signal strength processor for determining whether a valid signal is present at its respective remote antenna unit and an output controller for switching off the network connection when no valid signal is present. As a result, the cumulative noise generated by uplink stages connected to the remote antenna units is reduced by switching off the network connection of remote antennas that are do not have to be connected. The communications system and method may further include an output controller for controlling the output for its respective remote antenna unit based on the comparison by the signal strength processor.

Abstract: A communication system and method are provided for equalizing delay of transmission paths in a distributed antenna network. The distributed antenna network includes a plurality of remote antenna units, a central unit or a base station connected to the remote antenna units by transmission media, where each connection between the base station and one of the remote antenna units forms a separate transmission path having an associated delay time, a delay detector for determining the associated delay time of the separate transmission paths for each of the remote antenna units, and a delay compensator for adjusting the associated delay times in response to the delay detectors so that all of the associated delay times are substantially equalized. The system and method allow the delay parameters for the entire network to be set upon installation and then to be periodically updated without physical intervention by an operator.