Abstract: A method and apparatus for calculating the travel time of a vehicle as it transits through multiple locations. The method and apparatus includes a device for detecting a radio signal from a vehicle, attaching information to the radio signal, and transmitting a message packet with the signal and attached information to a central server. The central server stores the message packet. The central server compares the information in the message packet against other stored message packets received from multiple locations. When matching information is found, an algorithm is run to compute a vehicle travel time between two locations.

Abstract: A method and apparatus for calculating the travel time of a vehicle as it transits through multiple locations. The method and apparatus includes a device for detecting a radio signal from a vehicle, attaching information to the radio signal, and transmitting a message packet with the signal and attached information to a central server. The central server stores the message packet. The central server compares the information in the message packet against other stored message packets received from multiple locations. When matching information is found, an algorithm is run to compute a vehicle travel time between two locations.

Abstract: A context (112) of a communication received from a user in a vehicle is determined. The context (112) relates to a characteristic associated with the vehicle. An address of the communication is formed based upon the context (112) of the communication received from the user in the vehicle. The communication is transmitted to a recipient using the address.

Abstract: A wireless communication system (100) contains a number of service providers (145, 148, 149) that provide different services to communication units (105-108). The communication units (105-108) are limited as to how many of the services they can concurrently receive. Each communication unit (105-108) is associated with a service manage agent (SMA) (185-190) that manages the provision of the services to the communication unit (105-108). In one embodiment, each SMA (185-190) manages the provision of the services to only one of the communication units (105-108).

Abstract: A dispatch controller (103) located logically external to an existing telephone network (101) is coupled to the existing telephone network. When an originating communication device (e.g., 111) desires to initiate a dispatch call, the originating device transmits a call request to the existing telephone network, wherein the call request includes an identification (ID) of the originating device and a target address associated with the dispatch controller. The existing telephone network provides the call request to the dispatch controller. Upon receiving the call request, the dispatch controller retrieves dispatch-related information from a database (105) coupled to the dispatch controller based on the originating device's ID. Based on the retrieved dispatch-related information, the dispatch controller identifies a group of target communication devices (e.g., 107-110) for the dispatch call.

Abstract: A dispatch controller (103) located logically external to an existing telephone network (101) is coupled to the existing telephone network. When an originating communication device (e.g., 111) desires to initiate a dispatch call, the originating device transmits a call request to the existing telephone network, wherein the call request includes an identification (ID) of the originating device and a target address associated with the dispatch controller. The existing telephone network provides the call request to the dispatch controller. Upon receiving the call request, the dispatch controller retrieves dispatch-related information from a database (105) coupled to the dispatch controller based on the originating device's ID. Based on the retrieved dispatch-related information, the dispatch controller identifies a group of target communication devices (e.g., 107-110) for the dispatch call.

Abstract: In a digital communication system (100), a second message (309) may be substituted for a first message (301) by detecting a suitable transition point and beginning transmission of the second message at this transition point. In a frame-synchronous digital communication system, this transition point is a frame boundary within the first message.

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: A data communication protocol permits efficient and cost-effective transmission of control and ancillary messages among the components of a communication system infrastructure (200). Messages are organized into Infrastructure Control Words (300) with accompanying Format Identifiers (304), and interleaved with voice and data segments (707) to form message streams (700) that are transmitted from one infrastructure component, such as a base station (201), to another infrastructure component, such as a Digital Interface Unit (202).

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: 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 layered session data unit frame (300) is provided wherein a first frame (200), designated a session data unit("SDU"), containing user information (209), a link control field (205) and an encryption field (207), is divided into a plurality of smaller frames (321, 323), each having an information field and designated a link data unit("LDU"). According to the invention, the SDU user information (209) is allocated into the information fields (211, 213) of the plurality of LDU's. The SDU link control field (205) is divided into a plurality of sub-fields and imbedded into the information fields of a first group of LDU's. The SDU encryption field (207) is divided into a plurality of sub-fields and imbedded into the information fields of a second group of LDU's. The sub-fields may be distributed throughout the LDU's in a generally uniform fashion.

Abstract: In an RF communication system, a method for developing and communicating usage context information. When an inbound communication (110) is received from a communication unit (107), a repeater (101) at a base site (100) retransmits the received communication as an outbound signal (114), including usage context information interleaved with the information signal. Communication units are informed of communications of interest occurring over other communication resources without the need for sequential monitoring.

Abstract: In a mobile communications system, a plurality of base stations may receive the same signal, whereby the "best" reception may be determined. The plurality of received digital signals are combined to form a majority signal. Each of the received digital signals is compared to the majority signal to estimate the bit-error-rate (BER) of each received signal. If the difference between the highest and lowest BER is less than a predetermined threshold, the majority signal is selected for reception. Conversely, if the BER difference is greater than the predetermined threshold, the received digital signal with the lowest BER is selected for reception. Thus, the signal with the lowest BER is selected to provide the best possible communications.

Abstract: A data detector is disclosed wherein a received signal is analyzed to determine its statistical characteristics. These characteristics are compared to a predetermined statistical distribution. If the signal is statistically close to the statistical characteristics of a known signal a detect signal is generated and the received signal is passed for further processing and reception.

Abstract: A signal selection system is disclosed wherein a plurality of received signals are analyzed to determine their statistical characteristics. These characteristics are compared to a predetermined statistical distribution. The signal that is statistically closest to the statistical characteristics of a known signal is selected for further processing and reception.

Abstract: A receiver of digitally encoded voice signals that may be encrypted according to a plurality of keep subjects a received signal to decryption according to each of the keys. Decrypted signals are tested for the presence of modulation, and the signal, if any, that is decrypted is recovered for use. If it is desired, a visual indication may tell a user which key is being used to decrypt the signal.