Abstract: Diverse communication terminals attach via broadband radio to a communications network at any of typically three hierarchical cell sizes increasing from, typically, a single building to a city to a region. Almost all telecommunications traffic transpires, however, within lowest-level "picocells 1" to and from low cost "base stations 11" that have typically one radio transceiver 111, four optical transceivers 112, an ATM switch 113 and an ATM controller 114. Each local "base station 11" is interconnected to a regional "end office switch 12", where is realized connection to a worldwide wire/fiber line communications backbone 4, upon a multi-hop mesh network 100 via short highly-focused free-space broadband directional optical links 10. By this free-space wireless broadband access the need for new broadband access cabling the "last mile" to subscriber/users is totally surmounted. Subscriber service is of the order of 20 Mb/s peak rate, and 10 Mb/s average rate.

Abstract: A transmitted high definition television signal is represented by a packetized datastream configured as a sequence of data fields with a non-uniform data rate due to different types of different duration non-data overhead information. Each data field is prefaced by a Field Sync overhead segment followed by 312 packetized data segments each with associated overhead information. At a transmitter, a transport processor forms data packets with associated headers and exhibits uninterrupted operation at a constant uniform data rate, while supplying a packetized datastream to a network 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.

Abstract: A system of the present invention addresses the difficulty of aligning a reference sync byte at the beginning of a data packet during situations where the system experiences severe problems such as arbitrary resets/restarts or transmission disturbances. Specifically, the sync byte at the beginning of the data packet is automatically aligned with the beginning of a data acquisition interval when data is requested, even when there are arbitrary system resets/restarts. The alignment of the first data packet following a system reset is facilitated by the use of a Start Of Packet flag concurrent with the reference byte, together with a controlled logic network.

Abstract: A transmission processor (16) receives an input packetized datastream (FIGS. 6-9; FIGS. 15-18 signal A) containing packets of data bytes including MPEG coded video information. The transmission processor outputs a symbol datastream (FIGS. 15-18 signal F) representing a sequence of data fields (FIG. 1) comprising groups of data segments (X) with an associated field sync segment. The transmission processor inserts overhead information. e.g., FEC error coding information, into each data segment, and inserts the longer duration field sync overhead segment between groups of data field segments. The frequency of the transmission processor input byte clock (SC/2, FIG. 6; FIG. 15) an integer sub-multiple of an output symbol clock (SC) frequency. The input datastream exhibits constant uniform inter-packet data gaps and a constant uniform data rate, thereby facilitating the seamless insertion of the field sync overhead segment into the datastream without interrupting the datastream.

Abstract: 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 MPEG codewords less than a prescribed number of bits 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 bits.

Abstract: In a digital television signal processing system, a special codeword, a Packet Alignment Flag (PAF (14), 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 (12) under construction when a PAF (14) 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 (12) with respective headers (18). An incomplete data packet is filled with null (zeroed bits) words to make up a complete data packet with a prescribed number of words.

Abstract: 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.

Abstract: A method is disclosed for optimizing the operation of a packet transport system generating a packet stream carrying a plurality of component signals, and includes the following steps. First the packet stream is partitioned into successive groups, each group containing a predetermined number of packet slots. A plurality of lists are maintained, one associated with each packet slot in a group. A packet stream is generated by placing data representing a component signal selected in response to entries in the list associated with that packet slot into the packet slot. The contents of the plurality of lists are updated based on a predetermined parameter.

Abstract: 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.

Abstract: Techniques for making a recursive mesh network for connecting a varying number of access stations within a service area is disclosed. The techniques include (a) dividing the service area into M.times.N rectangular regions, having (M+1).times.(N+1) corners, which cover the entire range of the service area; (b) placing an access station at an available region corner whenever a new access station becomes available, and connecting the access station to its corresponding optical connection paths, until (M+1).times.(N+1) access stations have been so connected; (c) determining, for each additional new access station, which region the additional new access station falls within; (d) if this determined region has not been divided, dividing the determined region into S.times.T sub-regions; (e) if the divided determined region has less than (S+1).times.

Abstract: The present invention relates to a multichannel multihop lightwave communication network which allows packet concurrency in the network while avoiding the need for agile optical devices. The network comprises a lightwave communication medium (10) for supporting a plurality of independent user nodes; and a plurality of N network interface units (NIUs) (11). Each NIU is connected to the lightwave medium and one or more separate user nodes and comprises a trnasmitter section (28-35) and a receiver section (20-27) which are each fixedly assigned to transmit and receive, respectively, over a single channel or a plurality of separate channels to or from other NIUs of the network. In a connectivity pattern for one embodiment of the network, the NIUs are divided into k groups of p.sup.k NIUs such that each NIU of a first group of p.sup.

Abstract: The present invention relates to a wideband communication network using wireless radio transmissions either on a stand-alone basis or to supplement a hard-wired network. The exemplary network comprises (a) a plurality of transceivers associated with separate users of the network; (b) optionally at least one concentrator associated with certain separate subgroups of wireless and possibly hard-wired transceivers for providing duplex operation; and (c) a central node (i) capable of providing both duplex communications directly via a radio channel using radio links with certain subgroups of the transceivers and via a hard-wired connection with each optional concentrator, and (ii) for polling the needs of all transceivers and directing all packets of information from active transceivers through the central node and to the destined transceivers during each frame period.

Abstract: The present invention relates to an N-input, N-output "Knockout" packet switch (11) which uses decentralized control and distributed routing. More particularly, within the switch, the N input signals comprising fixed-length packets propagate along separate broadcast buses (14) to each of N bus interface units (15) which include N packet filters (20), a concentrator (21) and a shared buffer (22). Each bus interface unit is associated with a separate one of the N outputs (12) of the switch, and the N packet filters therein are each associated with a separate one of the N broadcast buses for detecting if a packet on the associated bus is destined for the associated switch output. The concentrator is used to reduce the number of separate buffers needed to receive packets which may arrive simultaneously and are destined for the associated output. Contending packets at the output of the concentrator are stored in the shared buffer before placement on the output line on a first-in, first-out basis.

Abstract: The present invention relates to a fast packet assignment technique, and a TDMA or FDMA multi-port switching arrangement for implementing such technique. In the present technique, the total traffic in a two-dimensional traffic matrix (T) from and to each of N remote service areas, regardless of destination or origination, is totaled to form separate input (R) and output (S) traffic vectors, respectively. Non-conflicting assignments are then made from these vectors for each packet or channel available during a predetermined time period while also providing the capability of substantially reducing multi-path or antenna sidelobe interference. An M.times.M switch (16) is designed to implement such technique which directs C input packets from M inputs (20.sub.1-M) into separate memory locations (Z.sub.ij). During the time period of the next C input packets, the M.times.M switch directs the presently stored packets to the proper ones of M outputs (27.sub.

Abstract: A terrestrial radio system which utilizes spot beams, time division multiple access and frequency reuse to provide communications services from a base station to remote customers within a system service region. The base station advantageously is arranged with multistage switching so as to permit the respective sharing of radio transmitters and receivers over larger number of antenna transmitting and receiving ports.

Abstract: The present invention relates to a burst demodulator for use, for example, in a TDMA communication system, which comprises a first section that downconverts a received r-f burst sequence signal to an approximate baseband signal with a local oscillator, samples the baseband signal at a predetermined rate, and converts the analog samples into an equivalent digital signal. A second section comprises a memory for storing the digital signals associated with a particular burst in a predetermined time period, and a slow-speed processor for reconstructing the received burst signal from the stored information and processing the reconstructed signal to provide for carrier and clock recovery, start-of-message identification, data detection, etc.

Abstract: The present invention relates to a dynamic resource allocation technique for multiple users of a channel that employs variable coding and associated redundancy to provide a maximum data rate for various demand conditions while simultaneously providing a maximal margin that is matched to the current demand condition. For such technique, each first data rate input signal is synchronized to a second higher data rate, the synchronized signals are then separately demultiplexed for propagation along separate paths and encoded in a separate variable rate coder (VRC). The output from each VRC is stored in a separate bus interface which contends for a common bus when full. A rate controller maintains the activity on the common bus at a minimum level by either monitoring (1) the activity on the bus, (2) the rate the bus interfaces are filling up, or (3) both (1) and (2) above, and in response thereto to transmit control signal to the VRCs to appropriately vary the codes and redundancy used.

Abstract: 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.

Abstract: The present invention relates to transmitters and receivers in a digital time division multiple access (TDMA) communication system wherein the resource sharing concept is generalized by fully exploiting the available clear air carrier-to-noise ratio (CNR) of a transmission link to achieve very high transmission capacity while maintaining low rain outage. Transmission is accomplished by using a first predetermined redundancy code and a first predetermined signal constellation for quadrature amplitude modulation during clear air conditions to permit a high rate of information transfer. When the fade depth exceeds the built-in fade margin, a second predetermined redundancy code and a second predetermined signal constellation is used while using time slots borrowed from a resource sharing reserved time slot pool to maintain the data rate at the fade site. Either one of the first redundancy code or signal constellation can equal either one of the second redundancy code or signal constellation.

Abstract: A digital communications satellite (12,44) receives signals from a plurality of narrow input spot-beams (14) of an uplink. It regenerates, multiplexes and routes the signals for transmission in a plurality of narrow output spot-beams (42) of a downlink. The uplink beams (14) each include a plurality of frequency re-use channels (18), while the downlink beams (42) each have only a single wide-band channel. The satellite (12,44) may multiplex the signals either before or after routing them. The spot-beams (14,42) may be fixed or scanning.