International Business Machines Corporation

Joseph M Bensadon

Norman F Brickman

Joseph A Alvarez, Iii

Robert W Krug

John F Brennen

Harold G Markey

Jacques A Besseyre

Robert P Barner

A mechanism is disclosed for a time division multiple access communications network, to enable the synchronizing of traffic messages between a transmitting and a receiving node. A transmit clock mechanism at the transmitting node includes a slip counter for accumulating a slip count value during consecutive intervals of transmission. The slip count value is transmitted along with the traffic messages over the communications link to the receiving node. A slip count detector is located at the receiving node, for receiving the slip count value and adjusting the receive clock at the receiving node in response to the slip count value. In this manner, a timing slip adjustment which has been made at the transmitting node will have a corresponding timing slip adjustment imposed at the receiving node so as to maintain the proper synchronization between the sending and receiving stations during a time division multiple access communications session.

Apparatus and method for providing a transparent interface across a

A system is disclosed to provide X.21 in-band call establishment signaling in the data path of a data communication system by utilizing a data port, digital switch and telephone signaling call processor in a satellite communications controller. The system includes an X.21 signaling protocol between a DTE and the satellite communications controller on the terrestrial side and allows self-switched digital data port functions in lieu of associated voice port and line functions as practiced in the prior art. An important aspect is that the signaling rate is the same as the line data rate. The data port goes through three generalized states during a normal call process. The first general state is idle, the second general state is the signaling state and the third general state is the data transfer state. At the start of the signaling state, the E input to the call processor is activated for the appropriate port. Call establishment signals are then processed through the digital switch and an X.21 adapter to the system's control processor. In the third data transfer state, the call establishment signaling has been completed and all data bits go through the digital switch and are transmitted to the digital interface. At the end of the call the data port goes back to the first, idle state. The significant overall feature of the system is the provision for X.21 in-band signaling on the terrestrial side of the satellite communications controller so that a digital data port can accept X.21 in-band call processing type signals. The digital data port detects the call processing type signals with the X.21 protocol and passes them on to the X.21 adapter in the satellite communications controller.

X.21 Switching system

A self-switched in-band signaling communication apparatus is disclosed which enables the switching of the signaling mode to the data mode on a single transmission line between a data terminal equipment or data communication equipment and the data port of a satellite communications controller, and the opposite switching from the data mode to the signaling mode under a single control bit. Signaling to and from the data port of the satellite communications controller is carried out using conventional dialing pulses at a signaling rate which is independent of the line data rate. The apparatus provides for the multipoint communication between a plurality of data terminal equipments using a unique multipoint turn-around process which provides a mobile bandwidth capability for the communications system.

Self-switched data port in-band signaling protocol

The position of a channel of information transmitted from a particular port is varied in response to the changing priority of that port's messages as time passes. Variable priority assignments become necessary when low speed data has been deferred in its transmission until a time just prior to the production of a second unit of data. The effect of changing the priority of deferred data messages in a TDMA burst is to change the relative position of the associated channel within the TDMA burst by means of compiling the address of that message in a higher priority threaded list. The mechanism by which a deferred data message has its priority changed from an initial low value to a subsequent higher value is by measuring the amount of time remaining for retaining a deferred data message relative to the expected time of arrival of the next data message, the impending arrival of a new message causing the priority of the deferred message to be increased, thereby increasing the probability of its successful transmission.

Dynamically variable priority, variable position channels in a TDMA burst

The transmission and reception pattern generators are synchronized for all data ports operating at the same data rate throughout an entire TDMA system. This eliminates the necessity for bit stuffing to accommodate non-integral multiple data rate data ports and yet allows data activity compression operations to be carried out.

Growing community of inventors

Germantown, MD, United States of America

Joseph M Bensadon