Bell Telephone Laboratories

At&t Bell Laboratories

Rollin E Langseth

Yu S Yeh

Anthony Acampora

Douglas O Reudink

William L Aranguren

A carrier and timing recovery technique is disclosed for combating the phase effects of multipath fading occurring during radio transmission. The technique is based on a known mathematical model of multipath fading. A test variable generator (26) develops a number of test variables whose relationship characterizes the multipath distortion. A processor (27) derives a plurality of coefficients of weighting measures from the test variables. The coefficients serve to adjust a matched filter (28) to provide greater use of those portions of the received radio signal yielding higher signal-to-noise ratios than those portions with lesser yields, as well as to compensate for multipath phase perturbations. The technique is also compatible with maximum-likelihood sequence detection techniques to provide further compensation for multipath fading effects.

Matched filter for combating multipath fading

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.

Signaling and ranging technique for a TDMA satellite communication system

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.

Processor for a TDMA burst modem

The present invention relates to a small digital time-division switching arrangement capable of interfacing with a plurality of PCM communication lines on one side and a separate plurality of transmission channels on the other side. A first processor primarily tracks call progress by scanning signalling bits indicating on/off hook state changes and a second processor controls the action of a time slot interchanger which both assembles and disassembles channel data and telemetry messages and establishes and breaks down calls while connecting appropriate service circuits to the communication lines during the progress of a call. The processors are implemented with separate microprocessor chips and associated memory and the switching arrangement can simultaneously communicate with a variety of call originating circuits employing a wide variety of control signals.

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Colts Neck, NJ, United States of America

Rollin E Langseth