International Business Machines Corporation

Michel F Choquet

Daniel Pilost

David Frederick Bantz

Victor Spagnol

Jacques Belloc

Jean Cholat-Namy

Simon Huon

Kenneth R Swartz

James B Staton, Iii

Francois De Saint Michel

Andre Vade

Jack L Rosenfeld

A DTE can control the modems attached thereto by transmitting command messages over the data path and analyzing report messages supplied by the modems in return. Each command message is identified by a specific header. A command message intended for a remote modem (34) is intercepted by the local modem (30) and reformatted so as to obtain a supervisory message that is then transmitted at the rate of one bit per baud. A command message intended for a remote multichannel modem (48) is transmitted either by means of a supervisory message or in the data mode of operation. Messages are specifically addressed to individual modems by a special hierarchical address which utilizes information of the network link level on which the desired modem resides together with information as to which terminal (DTE), if any, the desired modem is attached. All locally attached primary modems are assigned an address comprising the link level designation and a first constant. All remotely attached primary modems are assigned an address comprising their link level designation and the first constant. All secondary modems are assigned an address comprising their link level designation and a second constant or, in the event they serve an attached terminal (DTE), the DTE address is used instead of the second constant.

Method and system for addressing and controlling a network of modems

A DTE can control the modems attached thereto by transmitting command messages over the data path and analyzing report messages supplied by the modems in return. Each command message is identified by a specific header. A command message intended for a remote modem (34) is intercepted by the local modem (30) and reformatted so as to obtain a supervisory message that is then transmitted at the rate of one bit per baud. A command message intended for a remote multichannel modem (48) is transmitted either by a supervisory message or in the data mode of operation.

Method and system for controlling a network of modems

A communication system includes a plurality of requestors and a plurality of responders representing resources. A protocol exercised by all elements provides accurate and consistent interconnection of all elements in a system where messages may be delayed or lost. Requestors are provided with means to transmit a request for use of a plurality of resources, respond to acceptances from one or more responders and create a cooperative relationship by transmitting a confirmation to one responder and cancellation of the request to all other responders. Responders become committed to a requestor by signalling an acceptance to a request if a previous acceptance has not been transmitted, or if the resource is not already committed to another requestor, and a subsequent confirmation signal is received. The responder does not become committed after transmitting an acceptance if the next signal directed to it from the requestor is a request cancellation. Request signals and cancellation signals by a requestor can either be broadcast simultaneously to all responders of a class or transmitted to particular, designated responders, one at a time.

Protocol for inter-processor dialog over a communication network

Digital data communication system uses a common channel to carry both normal messages and supervisory messages, the latter being inserted into the message stream during intervals between normal messages. Each transmitting location has a switch or equivalent controller with three settings. Setting 1 enables data to pass from the normal message generator directly to the channel. Setting 2 enables data to pass indirectly from the normal message generator through a delay line to the channel. Setting 3 enables data to pass from the supervisory message generator to the channel. Message status means associated with the delay line enables the switch to assume setting 3 when no normal message is being generated and a supervisory message is awaiting transmission. When the supervisory message ends, the switch may assume setting 1 if the delay line contains no significant normal message data nor any indication that an out-of-synchronism condition exists; otherwise the switch assumes setting 2 until the delay line is cleared of normal message data or reaches a synchronous state, as the case may be, whereupon it returns to setting 1. Each supervisory message has a distinctive format which enables it to be recognized at the receiving location and diverted from the message stream to a supervisory message receiver before it can enter the normal message receiver.

Time domain supervisory channel for data terminal equipments

A method of and apparatus for determining during an initial training period the initial values of the coefficients of a transversal equalizer in a data transmission system in which the transmission channel creates frequency shift. The received periodic training sequence is modulated by a time-domain window signal whose Fourier transform exhibits a relatively flat central peak and has comparatively low values in the vicinity of those frequencies which are a multiple of the inverse of the period of the transmitted sequence, and the discrete Fourier transform W.sub.k of the modulated signal is computed. The values of the coefficients of the equalizer are obtained by computing the inverse discrete Fourier transform of the ratio F.sub.k =Z.sub.k /W.sub.k, where Z.sub.k is the discrete Fourier transform of the transmitted sequence.

Channel equalization apparatus and method using the Fourier transform

This invention relates to a new clock synchronizing arrangement for use in the receiving device of a data transmission system employing PSK modulation. In PSK systems, the received signal x(t), for a given carrier angular frequency .omega..sub.c can be defined by its envelope and its phase r (t) and .phi.(t), respectively. r(t) and .phi.(t) can be expressed by:

Growing community of inventors

Saint Donat, France

Michel F Choquet