Bell Telephone Laboratories

American Telephone & Telegraph Co., At&t Bell Laboratories

At&t Bell Laboratories

American Telephone and Telegraph, Co.

At&t Information Systems Inc.

Anthony Acampora

Douglas O Reudink

Yu S Yeh

Michael J Gans

Rollin E Langseth

Michael G Hluchyj

Corrado Pietro Dragone

Mark John Karol

Kai Y Eng

Jack Harriman Winters

Ta-Shing Chu

Chan D Tsao

Michael G Hluchjy

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.k NIUs is capable of transmitting over the fixedly assigned single channel, or any or all of the p separate channels, to a preferred one or all of the associated p separate NIUs of a second group, etc. based on a generalization of a perfect shuffle pattern. Such technique permits all NIUs of the network to communicate with all other NIUs either via a single hop or via multiple hops where NIUs in subsequent groups of p.sup.k NIUs act as intermediate retransmission units.

Multichannel, multihop lightwave communication system

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. The network also preferably includes diversity and resource sharing techniques to provide added protection against channel impairments on an as-needed basis.

Wireless network for wideband indoor communications

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. The lost packet rate of the 'Knockout' switch can be made as small as desired and latency of packets in the switch is the smallest achievable by any comparable switch.

N-by-N 'knockout' switch for a high-performance packet switching system

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.1-M) at the appropriate time for transmission in the proper packet or channel to the destined remote service areas. In accordance with the present technique and switch, the M packets concurrently directed from memory to the M output ports can comprise more than one packet from a particular service area to other separate service areas.

Fast assignment technique for use in a switching arrangement

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.

Terrestrial communications system

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.

Burst demodulator

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.

Technique for dynamic resource allocation in a communication system

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.

Network protocol for integrating synchronous and asynchronous traffic on

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.

Transmitter and receivers using resource sharing and coding for

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.

Satellite communications system with frequency channelized beams

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.

Broadcast type satellite communication systems

The present invention relates to a satellite communication system comprising a plurality of limited scan spot beams which permits high transponder utilization efficiency by virtue of pooling the resources of each terrestrial footprint. In an embodiment of the invention, a satellite comprises a plurality of transponders, the signals from each transponder being directed via one or more associated scanning beams over a separate limited scanning beam region on the surface of a celestial body. In a preferred arrangement, each of the plurality of scanning spot beams is scanned linearly and parallel to the other scanning spot beams in a manner wherein each of the scanning beams covers a separate one of adjacent bands dividing the overall service region on the celestial body. By proper orientation of each of the scan regions or bands, nearly equal volumes of traffic can be served by each transponder.

Satellite communication system with a plurality of limited scan spot

The present invention relates to a technique for increasing the rain margin at ground stations of a satellite communication system. In the present technique, spare TDMA time slots in each frame sequence are shared among all ground stations as required by stations experiencing a fade condition which exceed a predetermined power margin. Additional up-link power margin at a faded transmitter can be achieved by either increasing power transmission of a normal burst or by the use of spare time slots plus encoding and preamble field extension techniques for burst extension. Additional down-link power margin to a faded receiver is accomplished by either increased transmitter power transmission or by the use of burst extension and coding and field extension techniques. Apparatus for implementing framing, carrier and clock recovery and start of message detection using extended fields and coding techniques for other data at a transmitter and receiver and disclosed to overcome fade conditions.

Technique for increasing the rain margin of a satellite communication

The present invention relates to a technique for increasing the rain margin of a satellite communication system which includes a satellite capable of transmitting multiple concurrent beams comprising time slot bursts in a TDMA mode. The present technique creates a small pool of TDMA time slots which are dedicated or formed at some instant of time by the rearrangement of traffic to permit the power normally transmitted in any portion of the multiple concurrent beams to be applied to one beam in a multiple fixed beam or limited scanning beam system or any portion of the beams which are directed at one ground station in a multiple unlimited scanning beam system for accessing a ground station experiencing, for example, a fade condition.

Technique for increasing the rain margin of a TDMA satellite

The present invention relates to a technique for creating dedicated in-band, two-way, signaling channels between a master signaling ground station and each remote ground station of a satellite communication system using either an area coverage beam or a plurality of fixed and/or scanning spot beams. In the present technique, separate bursts of information within a superframe sequence are dedicated for only providing signaling information between the master signaling station and each ground station of the system. Each ground station, in turn, is dedicated a separate burst of information for transmitting only signaling information back to the master signaling station. Coarse ranging is performed by triangulation methods and then each ground station transmits a unique word within the predetermined time period of its dedicated signaling burst to the master signaling station. The master signaling station then transmits synchronization correction information back to each ground station in its dedicated signaling burst.

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Freehold, NJ, United States of America

Anthony Acampora