Abstract: A time division multiple access (TDMA) communications system (20) includes a first TDMA platform (22) for transmitting a call (32) over a circuit switched communication link (36) to a second TDMA platform (24). The call (32) exhibits a first signal type (84) and second signal type (86). A controller (42) establishes a capacity allocation (200) responsive to the first signal type (84) for the communication link (36). When the call (32) exhibits the first signal type (84), the first TDMA platform (22) transmits first packets (111) of the call (32) in a first packet format (113) using the capacity allocation (200), and when the call (32) exhibits the second signal type (86), the first TDMA platform (22) transmits second packets (140) of the call (32) in a second packet format (139) using the capacity allocation (200).

Abstract: A pre-payment energy metering system uses two-way smart card communications. Secure power line carrier communications are provided at the consumer locations communication between a customer terminal and the utility meter. Two-way secure communication of data is provided through the use of a smart card or memory card which conveys data from the utility service provider to the customer's terminal and also conveys information from the customer's terminal back to the utility. The pre-payment power system of the present invention allows consumers to pay for electricity prior to consumption through the use of the smart card which is loaded with funds at a fully automatic point-of-sale (POS) terminal or at the utility service providers staffed customer service center. Back office software interfaces between the POS terminals and customer service centers, and utility service providers customer information systems.

Abstract: A point-to-multipoint (PTM) communication system (20) includes a cellular radio infrastructure (22) having base stations (32) implemented in satellites (34) placed in low earth orbits (38). PTM subscriber radios (24) share common cellular radio infrastructure (22) multipoint channels (52) to engage in a common PTM communication session while the cellular radio infrastructure (22) also conveys point-to-point communications. A group control computer (28) constructs a channel list (126) which is downloaded to PTM subscriber radios (24). The channel list (126) identifies multipoint channels (52) and indicates when and where the channels (52) are active. Without emitting transmissions to the cellular radio infrastructure (22), PTM subscriber radios (24) autonomously switch to new multipoint channels (52) in response to their current time and location and the channel list (126).

Abstract: The present invention utilizes a dual polarization reception system (200) that utilizes the energy available in orthogonal polarizations to effectively increase link margin, thereby allowing for adequate signal quality reception in difficult environments. A co-polarized and a cross-polarized signal are separately downconverted and demultiplexed. The signals from each demultiplexed output are then sampled and weighted. The weighted samples for each polarity are combined in soft decision combining/decoding circuitry (255, 360), and this circuitry determines the most likely state of a received symbol's transmitted value.

Abstract: An active bias circuit 30 connected to a power amplifier PA maintains a power amplifier DC quiescent current at a fixed value over a wide temperature range. The active bias circuit 30 includes first and second current mirror circuits 32, 34. The power amplifier PA is an element of the second current mirror circuit 34. A temperature compensation circuit 42 is connected to the first current mirror circuit 32 for providing temperature compensation therewith. A first reference voltage source is connected to the first current mirror circuit 32 by way of the temperature compensation circuit 42 for providing a first reference voltage Vref to the first current mirror circuit 32. A current sink 36 is connected to a transistor of the first current mirror circuit 32 and a voltage source adjustment circuit 38 is connected to the first current mirror circuit 32 for setting a voltage provided to the first current mirror circuit 32.

Abstract: A master routing hub (50, FIG. 1 ) selects a communications path which enables subscriber units (10, 140) using disparate networks to communicate with each other. The master routing hub (50) receives a quality of service indicator (FIG. 4, 410) from a subscriber unit (FIG. 1, 10) as well as cost information from alternate communications networks and terrestrial communications networks. The master routing hub (50) selects an appropriate communications path in accordance with the quality of service indicator and thus provides the best available quality of service at the lowest cost to the subscribers (10, 140). The master routing hub (50) also provides the protocol conversion in order to enable the disparate communications networks to communicate with each other.

Abstract: An orthogonal frequency division multiplexed wideband communication system provides improved time and frequency synchronization by inserting an unevenly spaced pilot sequence within the constellation data. A receive correlates the received data using the unevenly spaced pilot sequence. The pilot sequence is generated with a maximum length pseudo random noise code and inserted into frequency bins having prime numbers.

Abstract: A communication system (10) includes a group call controller (GCC) (26) for use in establishing, maintaining, and controlling the provision of group call services within the communication system (10). To initiate a group call session for a particular subscriber group, a group call request is delivered to the GCC (26) that identifies the desired group. Upon receipt of the request, the GCC (26) coordinates the delivery of group call notification to the members of the identified group to notify the members of the initiation of the group call session and to identify to the members a physical communication channel (36) to be used by each member to participate in the group call. Upon receipt of the notification, the group members each tune to a corresponding physical communication channel (36) and are immediately made part of the group call. The group members are not required to make any transmissions on the physical channel (36) to participate in the group call.

Abstract: A method and apparatus for generating digitally modulated signals in which a serial data stream of digital signals to be modulated (70) is provided, the serial data stream being converted into real and imaginary components (74) which are then converted into a complex polar signal (80) representing the serial data stream. A carrier of appropriate frequency is generated by an infinite impulse response filter (84,86) and the polar signal is mixed with the output of the infinite impulse response filter to provide a representation of the complex polar signal modulated at the frequency generated by the infinite impulse response filter (88). Subsequently the imaginary component of the resulting representation is stripped from the signal (90) and the real component of the resulting representation is applied to a digital to analog converter (92) to produce an analog version of the serial data stream.

Abstract: The effect of Single Event Upsets (SEUs) occurring in cache memory (103) utilized in satellites is reduced. The idle time of a processor (102), utilizing cache memory (103), is monitored. If processor (102) idle time reaches a predetermined minimum (205), cache memory (103) is engage. When processor (102) idle time subsequently reaches a predetermined maximum threshold (203), cache memory (103) is disabled.

Abstract: A method (46) controls preferred communications periods as satellites (12) of a satellite-based communication system (10) move in their orbits (14) around the earth. The satellites (12) monitor for periods of low subscriber activity, and evaluate conditions such as a quantity of idle channels (60), available power level for the satellites (68), and satellite functional status (76) to control the onset and termination of preferred communications periods. A preferred communications period is initiated by transmitting an alert message to the subscriber units (26) in a coverage zone (16) and notifying a billing center (32). During a preferred communication period, the subscribers can be provided with incentives, such as discounted airtime rates, to increase call activity on the system (10).

Abstract: A shipping container (100) for transporting and handling a satellite (106) is disclosed. The shipping container (100) includes a support structure (102) for securing the satellite during transport, a base (116) hingedly connected to the support structure (102), and a cover (104) to protect the satellite (106) during transport, coupled to the support structure (102). The shipping container (100) also includes a upending actuator (112), a ballast arm (110), and a handling sling (108) to facilitate removal of the satellite (106) from the shipping container (100).

Abstract: A directable laser transmission module incorporating a vertical cavity surface emitting laser (VCSEL) array (28) and a refractive optical element (ROE) array (36) is provided. Each VCSEL (30) generates a laser beam (32) having an axis (44) substantially perpendicular to a substrate (42). The ROE array (36) is positioned proximate the VCSEL array (28) substantially parallel to the substrate (42) so that each laser beam (32) is intersected by only one ROE (34). Each of a plurality of communication signals is carried by at least one laser beam (32). An laser beam (32) carrying a one-beam signal is intersected, collimated, and directed by a single ROE (34) to its predetermined reception location (24). A plurality of laser beams (32) carrying a single multiple-beam signal is intersected, collimated, and directed by multiple ROEs (34) to a common predetermined reception location (24).

Abstract: A hands-free communications unit employs a downlink peak power memory element (150, FIG. 1), a downlink voice activity detector (140), and an uplink voice activity detector (180). The downlink voice activity detector (140) evaluates the incoming signal to determine if the signal includes voice. In a similar manner, the uplink voice activity detector (180) determines if an outgoing signal includes voice. In the event that the incoming signal includes voice and the energy of the outgoing signal exceeds a threshold calculated from the peak power of the incoming signal, the uplink voice activity detector (180) indicates that a double-talk condition exists (350, FIG. 3). In the event that the incoming signal does not include voice, the uplink voice activity detector (180) compares the uplink signal to a voice threshold above a noise floor to determine if the outgoing signal includes voice.

Abstract: A satellite communication system uses dual satellite coverage techniques to simulate the provision of full duplex communications in the system. Each subscriber (100) in the system communicates with two satellites (102, 104) that use complementary time division duplex (TDD) frame structures (50, 72) for communicating with the subscriber (100). In one embodiment, each satellite in the system performs a transition between a first TDD frame structure (50) and a second TDD frame structure (72) while travelling through a transition region (102) of an associated orbit (130). Preferably, the transition is performed gradually so that an abrupt reduction in system capacity is avoided. In another embodiment, individual orbital planes in the satellite system are dedicated for use with particular TDD frame structures. A subscriber thus communicates with one satellite in each of two planes during a connection.

Abstract: A method for scrubbing and passivating an anode plate (100) of a field emission display (120) includes the steps of providing a scrubbing passivation material (127); imparting to scrubbing passivation material (127) an energy selected to cause removal of a contamination layer (123, 117) from anode plate (100); causing scrubbing passivation material (127) to be received by contamination layer (123, 117), thereby removing contamination layer (123, 117); and depositing at least a portion of scrubbing passivation material (127) on anode plate (100), thereby forming a passivation layer (129).

Abstract: A point-to-multipoint (PTM) radio communication system (20`) includes a cellular radio infrastructure (22) having base stations (32) implemented in satellites (34) placed in low earth orbits (38). PTM subscriber radios (24) share common cellular radio infrastructure (22) multipoint channels (52) to engage in a common PTM communication session while the cellular radio infrastructure (22) also conveys point-to-point communications. The shared multipoint channels (52) are operated in according with different protocols to deliver system information to PTM subscriber radios (24), to provide access to PTM subscriber radios (24), to provide synchronization, to originate a PTM monolog and to be one of many targets of a PTM monolog.

Abstract: A method and apparatus encompasses a technique for routing an information packet through a satellite communications system 20 from a source satellite 38 to a destination satellite 40. A path through the system 20 is chosen for the packet and an identifier identifying the path is appended to the packet. In addition, an identifier identifying the destination satellite 40 is appended to the packet. Satellites in the system 20 then use the identifiers in the packet to route the packet to the destination satellite 40. If the chosen path is not available, an alternate path can be taken by the packet. In one embodiment of the present invention, a centralized controller 36 is provided for controlling the routing of packets throughout the entire system 20.

Abstract: A satellite ground station (500) mitigates potential interference from a fixed service installation (130, 150) by scanning a field of view and logging potentially interfering transmitters in a data structure (400). The data structure includes fields for azimuth, elevation, and frequency channel, and when complete, forms a map of potentially interfering transmitters within the field of view of the ground station. When a satellite traverses the field of view such that the ground station may interfere with, or be interfered with by, a known potentially interfering transmitter as identified in the map, the ground station takes mitigation measures such as changing frequency channels or handing-off to a different satellite.

Abstract: A subscriber unit (26) communicates with a satellite communication system (10) that projects cells. The satellites (12) and cells move relative to the earth. During every other TDMA frame, a subscriber unit (26) measures the signal strength of all candidate hand-off beams. The signal strength of the current beam is compared to the signal strength of the candidate hand-off beams. When the signal strength of the current beam is not the strongest, a counter is incremented (108). A hand-off is requested to the beam with the greatest signal level when the counter exceeds a predetermined threshold. Accordingly, only after the current antenna beam has not been the strongest beam for a certain period of time, is a hand-off requested. A different counter threshold is used for candidate hand-off beams from other satellites (12).