摘要:
The present invention relates to a point-to-multipoint or broadcast TDMA or FDMA satellite arrangement wherein each up-link message unit is intended for reception at one or more geographically dispersed remote receiving sites within a wide service area. In one arrangement of a TDMA or FDMA satellite, the up-link message units are received and each message unit is directed to a transponder and to one or more down-link antenna ports for concurrent transmission to each of the destinations receiving sites for such message. An alternative TDMA satellite arrangement provides for each up-link message unit to be temporarily stored during the receiving frame period and then transmitted in accordance with a predetermined frame format during the appropriate time segments of the subsequent frame period to all of the destinational receiving sites. A technique for providing such predetermined frame format is also disclosed.
摘要:
The present invention provides a processor for interfacing a TDMA burst modem (40), which transmits and receives bursts of information at high data rates in assigned time slots, and slow speed terminal processing equipment. The present processor comprises circuitry (50) capable of detecting frame or superframe markers in a received sequence and regenerating such markers, after initiation, at the normal interval for such markers despite false alarms or missed marker signals. Other circuitry (53, 57 and 52, 62) causes a memory (48, 56) to directly output a burst of information during an assigned time slot to the modem (40) and directly store received information from modem (40) during a predetermined interval which is designed to start before and end after the expected arrival of an assigned burst. Slower processing equipment is then used to find and process the burst in the stored information.
摘要:
The present invention relates to method and apparatus for substantially reducing the effects of interference at a receiver between concurrently received first and second digital signals which use the same frequency spectrum. Interference between signals is effectively reduced by transmitting the first digital signal in an uncoded form while concurrently transmitting the second digital signal with both reduced capacity when compared with the first signal and in coded form using a forward error correcting code such as, for example, a block or convolutional code. At the receiver intercepting both digital signals, a suitable detection process is performed to decode the second signal and separate both signals. The present invention is applicable to the simultaneous satellite transmission of an area coverage beam and a plurality of spot coverage beams or to increase capacity on a radio channel.
摘要:
The present invention relates to method and apparatus for communicating with one or more receiver stations disposed within a blackout region located in the vicinity of and surrounding each spot beam coverage area, the blackout region being caused by interference between concurrently transmitted and overlapping global coverage and spot coverage antenna radiated beams using the same frequency band despite the application of global beam interference suppression techniques at the spot beam receiving areas. Access to the receiver stations within each blackout region is provided by selectively turning off the associated interfering spot beam during a predetermined interval of time while ensuring that the power level of the radiated global coverage beam is not suppressed within the accessed blackout region to permit the global coverage beam to communicate with these receiver stations.
摘要:
A radio link management system for a home or office substantially (i) an ad hoc network of agents wirelessly communicating among themselves, while (iii) clients wirelessly communicate with proximate agents. Control of the network may be centralized as network controller integrated with an agent, or may be distributed upon the network of agents. Some agent or agents, which may include an agent that is also the network controller, typically serves as a gateway device which connects to a worldwide communications network external to the home or office, normally by fiber or by wire.Each agent is most commonly a small radio transceiver plus logic and power supply that mounts upon a wall and plugs directly into an AC power socket. Agents wirelessly communicate among themselves and with the controller—which may be centralized or distributed—in a bandwidth-efficient mode since prime power is not an issue. Each client, which is most commonly a battery-powered user device, wirelessly radio communicates with one or more proximately-located agents. Consistent with overall demand for the radio resource, parameters for radio communication are allocated ad hoc in a manner which is (a) client-dependent, and which (b) uses the least power from the battery-powered client. The agents establish an ad-hoc network among themselves, with routing among and between the agents being both multi-hop and “minimum hop” to conserve bandwidth. Accordingly both power and bandwidth are conserved, each as and where required and desired.
摘要:
A device and method for utilizing a single clock signal to generate a digital data stream signal for transmission in a compressed domain transmission system. The device includes a plurality of packetized elementary stream encoders electronically coupled to a transport stream encoder electronically coupled to an output interface adapted to generate the digital data stream signal. The method includes: operating each of the packetized elementary stream encoders responsively to the single clock sequence to generate a plurality of packetized elementary stream signals; operating the transport stream encoder responsively to the single clock signal to form a transport stream signal from the plurality of packetized elementary stream signals, wherein the transport stream signal includes a plurality of data packets each formed using the transport stream encoder and select ones of the plurality of data packets formed by the transport stream encoder include synchronization data; and, operating the output interface responsively to the single clock reference to output the digital data stream signal in compliance with an predefined manner.
摘要:
A transmitted high definition television signal is represented by a packetized datastream configured as a sequence of data fields (FIG. 1) with a non-uniform data rate due to unequal inter-data overhead information intervals. Each data field is prefaced by a Field Sync overhead segment followed by 312 packetized data segments each with associated overhead information (FEC). At a transmitter (FIG. 33), a transport processor (14) forms data packets with associated headers and exhibits uninterrupted operation at a constant uniform data rate, while supplying a packetized datastream to a network (17) which constructs sequential data fields by inserting the non-data overhead information into the datastream. The transport processor is advantageously operated at a constant uniform data rate without having to modify the original data field structure to accommodate the needs of the data field construction network. This result is facilitated by transferring data from the transport processor to an associated interface/buffer network (46) in response to a 3/8 symbol clock, in combination with a predetermined buffer fullness level. Specifically, a video recorder/playback device (15) receives a constant uniform data rate packetized datastream from the transport processor, and outputs a constant uniform data rate datastream to the interface/buffer network. A counterpart transport processor/decoder (86) at a receiver (FIG. 34) coacts with a data field processor (75) and similarly exhibits uninterrupted operation at a constant uniform data rate. A video recorder/playback device (85) receives a constant uniform data rate datastream from an interface/buffer (84) after removal of overhead information, and outputs a constant uniform data rate datastream to the transport decoder.
摘要:
In a digital television signal processing system, a special codeword, a Packet Alignment Flag (PAF), is inserted into an MPEG codeword bitstream to signify the presence of a Group of Pictures (GOP). The PAF immediately precedes a Picture Start codeword for an "I" frame, which initiates a GOP. A data packet under construction when a PAF appears is terminated since a GOP is intended to begin at a packet boundary. Such termination may result in an abbreviated packet of less than a prescribed number of codewords needed to complete a data packet. The last word of each packet is designated as such to facilitate the subsequent combining of data packets with respective headers. An incomplete data packet is filled with null (zeroed bits) words to make up a complete data packet with a prescribed number of words.
摘要:
A method for packet signalling between a base station with a variable antenna system and remote stations uses pilot tones sent by the remote stations to the base station at the start of each data transfer period in which signalling will occur in either direction. The base station uses the pilot tone to configure the directional antenna for communication with the remote station during that data transfer period. The pilot tone signals are initiated by polling signals and polling acknowledgment signals.
摘要:
Contention among a plurality of synchronous and asynchronous devices connected to a shared communication medium for access to time slots in a sequence of frames is resolved by assigning a unique priority word including a priority code prefix to each device and granting access to a given slot by comparing the values of the priority words assigned to competing devices. The priority code prefix is assigned as a joint function of whether synchronous or asynchronous communication is desired and whether synchronous communication is being initiated or continued. In each assignment protocol, synchronous communication is enabled by assuring any device that initially gains access to a particular time slot continued access to the same slot in succeeding frames. If desired, devices with synchronous access may relinquish unused time slots to asynchronous traffic, while reserving the ability to resume synchronous communication.