Abstract: An FM receiver (100) that includes a plurality of filtering elements (120-124) that have various center frequencies and bandwidths that adjust to maximize the signal quality of a desired signal (104) recovers the desired signal (104) by inputting the desired signal (104) to each of the plurality of filtering elements (120-124). Signal recovery is performed on an output of each of the filtering elements (120-124) to obtain a plurality of recovered signals. The recovered signals are then measured to obtain a plurality of signal quality metrics for the desired signal.

Abstract: A method of allowing use of small, low-power communication systems (20) within the coverage area (11) of larger trunked communication systems. A low-power communication system re-uses the same communication resources used by the larger trunked system whenever sufficient distance exists between large system communication units and the low power system so as to avoid interference. Large system communication units may also be constructed to operate in a dual mode format so as to transmit and receive in a low power mode and on re-used resources, whenever near a low power system or to transmit and receive in a high power mode whenever else necessary.

Abstract: In a simulcast communication system (100), a communication unit (110-115) may request enhanced coverage area services by transmitting a request for enhanced signal quality to a central simulcast controller (101). Upon receipt, the central simulcast controller (101) identifies, based on information pertaining to the location of the communication unit, a set of transmitters (102-109) to enhance coverage in the area of the communication unit. The central simulcast controller determines enhanced coverage area delays for each of the transmitters and adjusts the respective delays of each transmitter such that transmitted signal quality is enhanced at the location of the communication unit.

Abstract: A simulcast radio transmission system (250) transmits message signals (318) including selective call tones, originating from a message source (202), to a geographical area (115). The simulcast system includes a controller (204) coupled between the message source (202) and a plurality of remote transmitter sites (208, 210) for exchanging message signals (318) including selective call tones therebetween. Connecting the controller (204) to the plurality of transmitter sites (208, 210) are a plurality of interconnect links (224, 226), each having bounded propagation time delay characteristics. The simulcast system (250) employs phase numbers associated with the starting phase of the selective call tones to allow accurate reconstruction of the selective call tones.

Abstract: A transceiver compatible with both wide channel constant envelope 4 level FSK FM modulation and narrow channel .pi./4 differential QPSK linear modulation allows compatible interaction between modified constant envelope and non-constant envelope transmitters. All Nyquist filtering occurs in the transmitters, and none in the receiver.

Abstract: A data transmitter (100) operating at a transmit frequency provides a modulated data signal (114) by adjusting a reference frequency signal (108). The method of modulating an N-level data signal (102) inputted to the transmitter (100) provides for inputting, to a signal processor (201), a frequency deviation value. Using the frequency deviation value, the signal processor (201) then determines a maximum rate of enabling the frequency adjustment. Further, a deviation ratio corresponding to one of the N-levels is determined, and an increment value is then calculated (302) using this deviation ratio. Lastly, the frequency adjustment is enabled (312, 320) using the calculated increment value.

Abstract: A method and apparatus for generating an output signal (616) having a pre-determined frequency shift relative to the frequency of a reference signal from a reference frequency generator (202) comprise a digital phase-locked loop (206) coupled to the reference signal for generating the output signal (616). The method and apparatus further comprise adding pulses to the reference signal in a pulse addition circuit (304), the pulses recurring at a first cyclical rate determined by a microprocessor (702). The method and apparatus further comprise concurrently subtracting pulses from the reference signal in a pulse subtraction circuit (302) at a second cyclical rate.

Abstract: A method for measuring channel delay measures the delay for a message to propagate from a prime site (100, 400) to a remote site (200, 500) via the channel (300, 600). The prime site includes a clock for providing a first value, T1, based on the current time at the prime site. The remote site includes a clock for providing a second value, T2, based on the current time at the remote site. Both clocks are synchronized with a common timing source, such as a GPS satellite timing signal. Therefore, T2 equals T1. In one embodiment, the prime site determines T1, and simultaneously sends a message to the remote site via the channel, the message including T1. Upon receiving the message, the remote site simultaneously determines T2. The remote site decodes the message to determine T1, and then determines the delay based on the difference between T2 and T1.

Abstract: A network (2) utilizing power conductor distribution and incorporating infra-red (IR) radiation nodes having IR transducers (4, 6, 8). The IR transducers are located in ceiling-mounted lighting fixtures (16, 18, 20) and are connected to power terminals in the lighting fixtures both for powering the IR transducers in operation and for communicating network information. The transducers are thus positioned optimally for good IR communication and require no additional cabling.

Abstract: Shown, herein, is a method of allowing use of small, low-power communication systems within the service coverage area of larger trunked systems. The small, low-power systems are constructed to reuse at least some of the communication resources, also used by the larger system. The large system measures signal strength values of large cell communication units and transfers such values to the small systems. A small system compares the transferred values with a threshold and when the threshold is exceeded, reuses the communication resources under a TDM format within the small system.

Abstract: An improved synchronization method and apparatus, according to the invention, is provided. According to the invention, in a simulcast system having a remote site receiving frames from a base site, each frame containing a predetermined number (k) of transmit sample periods, and the transmit sample clock and remote synchronization clock frequencies known (f.sub.tx and f.sub.pps respectively), the remote site synchronizes a frame as follows. First, it receives a frame from the base site. Second, it determines the sequence number n for the frame. Third, it determines the launch time the first frame was to be broadcast from the remote site. Fourth, it computes a realignment time based on [(n-1)*(k)+launch time for first frame] MOD (f.sub.tx f.sub.pps). Fifth, it transmits the first bit of the frame at the realignment time.

Abstract: An adaptive digital equalization filter is provided to remedy the differential time delay problem in a digital simulcast system. The digital simulcast system includes an adaptive digital equalization filter with N coefficients, and a fixed analog anti-alias filter. According to the invention, the adaptive digital equalization filter first measures the amount of delay contributed to the output signal by the fixed anti-alias filter. This is accomplished by exciting the anti-alias filter with a unit impulse, and measuring the resulting impulse response. The adaptive filter next determines the characteristics needed to compensate for the amount of measured delay contributed to the output signal by the fixed filter. This is accomplished by computing a new set of N coefficients using the Levinson-Durbin algorithm. The adaptive filter next adjusts its coefficients based on these determined characteristics. Further, the adaptive filter periodically determines when it is time to update the N coefficients.

Abstract: Shown, herein, is a method of allowing use of small, low-power communication systems within the service coverage area of larger trunked systems. The small, low-power systems are constructed to reuse at least some of the inbound frequencies of communication resources, also used by the larger system. The large system measures signal strength values of large cell communication units and transfers such values to the small systems. A small system also measures the signal strength and compares the measured and transferred values with thresholds and when the thresholds are exceeded, reuses the communication resources under a TDM format within the small system.

Abstract: A way of allowing small, low-power communication units to reuse trunked system communication resources within the service coverage area of the larger trunked system without experiencing significant interference from the trunked system. The low power units (requestors and targets) avoid interference through spread spectrum transmissions.

Abstract: A time division multiplexed system is disclosed in which communication messages among a wide area site and a plurality of substantially scattered local sites are communicated on a radio frequency channel which is divided into a plurality of time slots, wherein at least one of the time slots is further divided into a plurality of subslots. Communication units operating in the wide area site communicate communication messages during the time slots, and the communication units operating in the local sites communicate communication messages during the subslots which are assigned to each of the local sites.

Abstract: A TDM cellular communication (100) system includes a plurality of repeaters (102) each providing communication coverage for a cell site. A plurality of communication units communicate with the repeaters. The communication units are handed off from one cell site to another by measuring the range of the communication units from the repeaters. If the range exceeds a predetermined range the received signal quality of the adjacent cell site repeaters are measured. An available cell site which provides the best received signal quality is selected by the communication unit for hand off.

Abstract: According to the invention, an information signal, such as a information signal, is sampled, quantized and processed digitally through an information encoder. Digitally processed samples produced by the encoder are modulated onto a communication channel to create channel symbols having a magnitude of modulation proportional to a characteristic of a respective digitally processed sample. Both a radio frequency (RF) transmission embodiment, and a wireline embodiment are provided. In a final aspect of the present invention, encryption is provided to ensure communication privacy.