Bell Telephone Laboratories

Lucent Technologies Inc.

At&t Bell Laboratories

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

Yu S Yeh

Douglas O Reudink

Michael J Gans

Anthony Acampora

Kai Y Eng

Mark John Karol

Rollin E Langseth

Michael G Hluchyj

Laurence Eugene Mailaender

Lawrence Joel Greenstein

Ta-Shing Chu

Sing H Lin

For use in a wireless network having geographically-distributed base stations that serve wireless terminals, a system for, and method of, improving an operation of the wireless network. In one embodiment, the system includes: (1) a signal quality determination circuit that determines a relative quality of signals communicated between one of the wireless terminals and a set of base stations within range of the one of the wireless terminals and (2) a base station selection circuit, coupled to the signal quality determination circuit, that selects a base station in the set to serve the one of the wireless terminals based on the relative quality of signals.

System and method for optimizing a wireless network by adaptive configuration of base stations and wireless terminals

A CDMA communication system is disclosed offering a near continuum of data rates up to a maximum rate. The disclosed CDMA communication system increases the data rate variability, without disturbing the orthogonality between users. An increased number of data rates is obtained by time multiplexing the data rates achievable with conventional CDMA systems to provide additional data rates for various multimedia applications. If a user is assigned a specific orthogonal code sequence, such as a Walsh sequence, which permits a maximum data rate, nR, with conventional systems, the user can obtain additional desired data rates up to the maximum rate nR, by time multiplexing the specific orthogonal code set. Desired bit rates are achievable for applications requiring bit rates that are not an integer multiple of the rates provided by conventional techniques. A fundamental rate of R or &ldquo;fat pipe&rdquo; rates of powers-of-two multiples of the fundamental rate can be achieved in a conventional manner. A desired rate up to the maximum &ldquo;fat pipe&rdquo; rate is achieved by time multiplexing the codes w to achieve rates between R and nR, where w , denotes the first nth of the spread spectrum code w . The transmitter of the present invention achieves a rate conversion to match the appropriate codeword to the appropriate data rate, by employing buffering and reclocking of the data, with time multiplexing of the orthogonal Walsh codes corresponding to the available lower and upper rates. The rate conversion must be synchronized with the selection of the orthogonal Walsh code (corresponding to the lower and upper rates).

Method and apparatus for achieving data rate variability in orthogonal spread spectrum communication systems

The present invention relates to an antenna system utilizing a power sharing network to facilitate linear operation of power amplifiers by equally distributing an electromagnetic communication signal to the plurality of power amplifiers provided in the antenna system of the present invention. The power sharing network configuration enables linear power amplifier sharing with an input signal. In particular, the present invention antenna system provides a circuit arrangement providing a greater number of linear power amplifiers relative to antenna elements provided.

Power shared linear amplifier network

The present invention provides a wireless communication system which employs Butler matrix combiners and circuit switching at transmitter and receiver antenna arrays to provide directive beamwidth capabilities. Such narrow beamwidths permit the communication system to determine and select the transmission path having an optimum signal quality. The antenna arrays are integrated in a multilayer construction which reduces power consumption, increases the coverage range, improves the efficiency of the antenna array, and which has lower fabrication costs.

Directive beam selectivity for high speed wireless communication networks

An intermodulation distortion (IMD) detection system improves IMD reduction capability of power shared linear amplifier networks. In one embodiment, first and second power sharing networks, preferably Butler Matrices, are provided with a plurality of linear amplifier circuits coupled therebetween. A plurality of input signals are applied to respective input ports of the first power sharing network, with a portion of each input signal amplified by each amplifier circuit and then recombined in the second power sharing network so that each amplified input signal appears at only one output port of the second power sharing network. An antenna coupled to each of these output ports then radiates the amplified signal energy associated with one of the input signals. A test signal, which may be a dual tone signal, is applied to another input port of the first power sharing network, where it is split and amplified by each amplifier circuit. Each amplifier circuit includes detection circuitry for detecting IMD energy of the test signal produced in the amplifier, which is also indicative of the IMD energy generated due to the amplification of the input signals. The amplified test signal is then recombined by the second power sharing network so that it appears only at one output port, where it is terminated.

Intermodulation distortion detection in a power shared amplifier network

Disclosed is a low distortion amplifier circuit of the predistortion type that employs a cuber circuit in the predistortion path to provide optimized signal energy at third order intermodulation frequencies, which cancels IMD products generated by the main power amplifier. The cuber circuit employs a pair of anti-parallel diodes that are biased with at least one D.C. source to produce a D.C. current flow through each diode. The input signal applied to the cuber circuit produces signal current flow in each diode to enable a third order output current to be extracted. A desired amount of third order power is thereby provided to realize minimal IMD power in the main amplifier output over a wide dynamic range of the input signal. Using a circuit analysis based on a power series approach, circuit parameters of the cuber circuit can be optimized to provide a desired amount of cancellation of third order IMD products in the main amplifier, without generating excessive higher order power, over an optimized dynamic range of the input signal.

Low distortion amplifier

This invention is large N.times.N packet switch, formed using a plurality of smaller packet switches. The invention comprises an N input, L output interconnect fabric (L&gt;N), and a plurality of J.times.K smaller packet switches (J&gt;K). Each of the J inputs to each packet switch is connected to a separate one of the L outputs of the interconnect fabric, and each of the K outputs from each packet switch is connected to a destination equipment. In operation, packets are received at the N inputs to the interconnect fabric, and each packet is routed to one of the inputs of the packet switch associated with the destination user equipment for the packet. Simultaneous packets, up to J in number, are routed to separate inputs of a particular packet switch for distribution to their respective destinations, while all other simultaneous packets destined for user equipments associated with the same packet switch are lost, the probability of such a loss being acceptably small.

Growable packet switch architecture

This invention is an inventive N input by L output interconnect fabric. In operation, packets comprising an information field and an address are received at the N inputs to the interconnect fabric, and the address in each packet is mapped to a group of outputs, rather than to any particular output. Each packet is then routed to any available one of the interconnect fabric outputs associated with the group to which the packet is mapped. If a number of packets destined for the same group simultaneously arrive at the interconnect fabric inputs and the group to which they are all destined does not comprise enough outputs to accept them, then all packets in excess of the number that the destined group can accept are simply discarded. The probability of lost jackets due to such discarded packets is acceptably small. In one exemplary embodiment, the invention can be utilized to build arbitrarily large packet switches.

Interconnect fabric providing connectivity between an input and

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 an N-input, N-output 'Knockout' packet switch (11) which uses decentralized control and distributed routing for routing high-speed, time-multiplexed, variable-length packets of information from the N inputs to the N outputs. More particularly, within the switch, the N input signals are separately synchronized such that the start of each arbitrarily arriving variable-length packet is synchronized to the start of a next mini time period of a sequence of mini time periods common to all inputs. The synchronized N input signals then 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) capable of processing variable-length packets. 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 (a) reduce the number of separate buffers needed to receive packets which may arrive simultaneously and are destined for the associated output, and (b) only directs a maximum of L concurrently arriving packets to the shared buffer while discarding, or 'knocking' out, the remainder. 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 discarded 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.

The present invention relates to a space diversity combiner which includes two branches wherein separate multipath signals received from a remote source are propagated. The branch signals are combined and the combiner output signal is used for obtaining noncoherent spectrum measurements which are in turn used to account for both dispersion and noise in controlling the relative amplitudes and phases of the two branch signals to provide a maximum performance measure for the combiner.

Technique for digital radio space diversity combining

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 technique for efficient spectrum utilization in mobile radio systems divided into a plurality of geometrically-shaped cells (10-21). Mobiles (24) in each cell are served by at least one base station (30-40) comprising a directional antenna having a beamwidth corresponding to the overall area of the associated cell. Each base station communicates with mobiles within the associated cell using separate primary channels (C.sub.p) within a first portion of the system frequency spectrum when a mobile is not experiencing interference above a predetermined interference level, and switches a mobile to a separate secondary channel (C.sub.p) within a selected section (f.sub.1, f.sub.2, f.sub.3) of the remaining second portion (f.sub.i) of the system frequency spectrum when the interference at a mobile exceeds the predetermined interference level. Each selected section used in adjacent portions of adjacent cells being within a different frequency subband of the second portion.

Technique for efficient spectrum utilization in mobile radio systems

The present invention relates to a cooperating arrangement for a pair of space diversity stations (30 and 40) interconnected by a communication link (20) wherein each station normally communicates independently with a remote point (12) of the system while handling traffic related to a separate service region (32 and 42) or separate portion of an overall service region. At the occurrence of a fade condition at one of the two stations, the fading station alerts the other station of the pair of such condition, and both stations are enabled to cause the normal two-way communications between the faded station and the distant point to be routed over the communication link for two-way transmission between the non-faded station of the pair and the distant point along with the normal associated two-way transmissions between the non-faded station and the distant point.

Cooperating arrangement for diversity stations

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

Yu S Yeh