Abstract: A transcoder architecture and method for transcoding in land mobile radio (LMR) systems are provided. The LMR system includes a first communication site configured to communicate using a first LMR communication protocol and a second communication site configured to communicate using a second LMR communication protocol. The LMR system further includes a transcoder configured to receive LMR content from the first communication site communicated using the first LMR communication protocol and digitally convert the LMR content to the second LMR communication protocol to be communicated to the second communication site.

Abstract: A method and system is provided for improving bit error rate (BER) performance in delay spread fading conditions, such as the fading associated with simulcast systems. BER is improved through novel symbol synchronization that comprises oversampling an input signal and filtering the samples to determine a composite symbol sample point that converges toward the center of the signal's effective eye pattern. The composite symbol sample point may be an average of previous composite symbol sample points and an instantaneous sample point determined based on samples from a synchronization field of the signal. The updated composite symbol sample point may be utilized for future sampling of the incoming signal.

Abstract: A security system for a digital trunked radio system having a digital control channel and a plurality of working channels, wherein said working channels are assigned for temporary use of individual radio units by digital control signals transmitted over said control channel, said control channel carrying digital control signals between a base site and said radio units, comprising a digital key, said key used to limit access to the system equipment and system control channel transmissions.

Abstract: A system and method for automatic roaming in land mobile radio (LMR) systems are provided. The method includes determining a signal quality value for each of a plurality of communication channels in the LMR system and determining if a signal quality level of a current communication channel is below a predetermined threshold. The method further includes automatically switching communication from the current communication channel to one of the plurality of communication channels if the signal quality level is determined to be below the predetermined threshold.

Abstract: A method for reliable communication within a digital trunked radio system having a digital control channel and a plurality of working channels, wherein said working channels are assigned for temporary use by a subset of radio units by digital control signals transmitted over said control channel, said control channel carrying outbound digital control signals from a base site to said radio units, said outbound digital control signals having a fixed transmission time slot, said method comprising the steps of: (a) transmitting a first message and a second message, each 28 bits in length, within said time slot; (b) defining at least one first message type identifier field within said first message; (c) defining a group identifier in said first message, said group identifier comprising from greater than 11 up to 16 bits; (d) defining at least one second message type identifier field within said second message; (e) defining a logical identifier in said second message, said logical identifier comprising from greater

Abstract: A method and system is provided for improving bit error rate (BER) performance in delay spread fading conditions, such as the fading associated with simulcast systems. BER is improved through novel symbol synchronization that comprises oversampling an input signal and filtering the samples to determine a composite symbol sample point that converges toward the center of the signal's effective eye pattern. The composite symbol sample point may be an average of previous composite symbol sample points and an instantaneous sample point determined based on samples from a synchronization field of the signal. The updated composite symbol sample point may be utilized for future sampling of the incoming signal.

Abstract: A transcoder architecture and method for transcoding in land mobile radio (LMR) systems are provided. The LMR system includes a first communication site configured to communicate using a first LMR communication protocol and a second communication site configured to communicate using a second LMR communication protocol. The LMR system further includes a transcoder configured to receive LMR content from the first communication site communicated using the first LMR communication protocol and digitally convert the LMR content to the second LMR communication protocol to be communicated to the second communication site.

Abstract: A self-calibrating radio is described. In one exemplary implementation, a radio signal from its local voltage controlled oscillator. The calibration system automatically calibrates the radio by: (i) receiving a reference signal having a calibrated reference frequency, (ii) comparing the local frequency to the reference frequency to determine whether there is a difference between the local frequency and the reference frequency and (iii) adjusting the local frequency by an offset frequency, if the difference between the local frequency and the reference frequency is greater than a threshold value.

Abstract: A security system for a digital trunked radio system having a digital control channel and a plurality of working channels, wherein said working channels are assigned for temporary use of individual radio units by digital control signals transmitted over said control channel, said control channel carrying digital control signals between a base site and said radio units, comprising a digital key, said key used to limit access to the system equipment and system control channel transmissions.

Abstract: A security system for a digital trunked radio system having a digital control channel and a plurality of working channels, wherein said working channels are assigned for temporary use of individual radio units by digital control signals transmitted over said control channel, said control channel carrying digital control signals between a base site and said radio units, comprising a digital key, said key used to limit access to the system equipment and system control channel transmissions.

Abstract: Method processor and processor-readable medium for reducing the level of feedback-induced noise in the output signal from an audio automatic gain control circuit are provided. The method allows for receiving a stream of pulses comprising an input signal to the automatic gain control circuit. The method further allows for receiving estimates of respective high and low frequency energy components of the input signal. The respective high and low frequency components are averaged, e.g., over a respective sliding window. An energy scalar is calculated based on the ratio of a predefined target energy level over a combined value of the high and low frequency components. A relating action allows to compare the target energy level to the combined value of the high and low frequency components. Based on the comparison results, the calculated energy scalar is limited to within the two limit values.

Abstract: A self-calibrating radio is described. In one exemplary implementation, a radio signal from its local voltage controlled oscillator. The calibration system automatically calibrates the radio by: (i) receiving a reference signal having a calibrated reference frequency, (ii) comparing the local frequency to the reference frequency to determine whether there is a difference between the local frequency and the reference frequency and (iii) adjusting the local frequency by an offset frequency, if the difference between the local frequency and the reference frequency is greater than a threshold value.

Abstract: An extended addressing protocol for use with digital trunked radio systems that allows the maximum number of radios on a digital trunked radio system to be increased, and also allows the maximum number of groups within the system to be increased, while at the same time remaining consistent with the timing structure currently used by existing radios.

Abstract: Method processor and processor-readable medium for reducing the level of feedback-induced noise in the output signal from an audio automatic gain control circuit are provided. The method allows for receiving a stream of pulses comprising an input signal to the automatic gain control circuit. The method further allows for receiving estimates of respective high .and low frequency energy components of the input signal. The respective high and low frequency components are averaged, e.g., over a respective sliding window. An energy scalar is calculated based on the ratio of a predefined target energy level over a combined value of the high and low frequency components. A relating action allows to compare the target energy level to the combined value of the high and low frequency components. Based on the comparison results, the calculated energy scalar is limited to within the two limit values.

Abstract: Single Channel Autonomous Trunking (SCAT) radio frequency systems and methods use a single duplex Time Division Multiple Access (TDMA) channel for the control and working channels thereof. By providing a single duplex TDMA radio frequency channel including a plurality of TDMA time slots in SCAT systems and methods, the SCAT systems and methods can simultaneously operate in a control channel mode and a working channel mode using the single duplex TDMA radio frequency channel.