High speed modem

• US 4,771,417 A
• Filed: 09/18/1986
• Issued: 09/13/1988
• Est. Priority Date: 09/18/1986
• Status: Expired due to Fees

• Current Assignee: Racal-Datacom, Inc. (Thales SA)
• Original Assignee: Racal Data Communications Incorporated
• Inventors: Prasad, Venkat, Maxwell, Ronald K., Yoshikawa, Harunori, Smith, Fred G., Zorzi, Karl J.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Scutch, III, Frank M.
• Application Number:
  US06/909,012
• Time in Patent Office: 726 Days
• Field of Search: 370/35, 370/32, 370/110.1, 375/8
• US Class Current: 370/296
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/1877 for semi-reliable protocols, e.g. for less sensitive applications like streaming video buffer level management for video bitstream control arrangements H04N21/44004
• CPC Class Codes: H04L 27/00 Modulated-carrier systems
• CPC Class Codes: H04L 5/1446 of transmission speed
• CPC Class Codes: H04L 5/16 Half-duplex systems; Simplex/duplex switching; Transmission of break signals non-automatically inverting the direction of transmission
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

A modem is disclosed having a data transmission protocol involving lower-speed, full-duplex operation during the connect sequence with a remote modem and an automatic switch to higher-speed, half-duplex operation for data transfer. Further, the modem data transmission involves transparently changing between lower-speed, interactive operation and higher-speed operation based upon transmission demands. The operation is controlled by a processor monitoring the contents of a transmit data buffer and providing a mode control command to the modem transmitter. The modem also adapts its speed to the quality of the telephone line by fallback or fallforward to a different speed based upon predetermined data frame retransmission criteria.

Claims

1. Apparatus for communication of data over a telephone line, comprising:

a transmit data buffer for accepting digital data;

a transmitter receiving data from the transmit data buffer, for placing a transmit signal on the telephone line;

said transmitter being selectively operable in either a lower-speed, full-duplex mode or a higher-speed, half duplex mode in response to a mode control command; and

a control circuit coupled to the transmitter to provide the mode control command;

the control circuit providing a mode control command to the transmitter to select the lower-speed, full-duplex mode during a handshake sequence, and for thereafter monitoring the transmit data buffer and providing a mode control command to the transmitter to select the higher-speed, half-duplex mode when there is a predetermined amount of data in the buffer for transmission and providing a mode control command to select the lower-speed, full-duplex mode when there is less than the predetermined amount of data in the buffer for transmission.

2. Apparatus for communication of data over a telephone line to a remote data receiver, comprising:

a transmit data buffer for holding data;

a transmitter receiving data from the transmit data buffer, for placing a transmit signal on a telephone line to communicate date and control frames;

said transmitter being selectively operable in either a lower-speed, full-duplex mode or a higher-speed, half-duplex mode in response to a control command; and

a control circuit coupled to the transmitter, for providing a control frame to be sent by the transmitter to the remote data receiver to signal higher-speed operation and producing the control command to the transmitter to select the higher-speed, half-duplex mode based upon the amount of data in the transmit data buffer.

3. The mode of claim 2 wherein said control circuit further provides a control frame to be sent by the transmitter to the remote data receiver to signal lower-speed operation and producing the control command to the transmitter to select the lower-speed, full-duplex mode.

4. Apparatus for communication of data over a telephone line between a local data terminal and a remote modem, comprising:

a transmitter for accepting data and control frame information and placing a transmit signal on a telephone line;

said transmitter being selectively operable in either a lower-speed, full-duplex mode or a higher-speed, half-duplex mode in response to a mode control command;

a receiver for accepting a transmit signal of link control frame information from a remote modem over the telephone line and providing a receiving signal of control frame information;

a transmit data buffer for accepting data from a local data terminal at a rate established by data transmission demand, said buffer being coupled to the transmitter;

a control circuit coupled to the transmitter to provide control frame information and the mode control command, and coupled to the receiver to obtain the receive signal of the control frame information; and

the control circuit for providing the mode control command to the transmitter to select the lower-speed, full-duplex mode during an exchange of control frame information with a remote modem, and for thereafter monitoring the transmit data buffer and providing a mode control command to the transmitter to select the higher-speed, half-duplex mode based upon the data transmission demand.

5. A modem for providing communication of data over a telephone line between a local data terminal and a remote modem, comprising:

a transmitter for accepting data and control frame information and placing a transmit signal on a telephone line to the remote modem;

said transmitter being selectively operable in either a lower-speed, full-duplex mode or a higher-speed, half-duplex mode in response to a control command;

a receiver for accepting a transmit signal from a remote data communication unit over the telephone line in either a higher-speed, half-duplex mode or a lower-speed, full-duplex mode in response to a mode control command and providing a receive signal;

a transmit data buffer for accepting data from a local data terminal;

a processor coupled to the transmitter and the receiver and providing mode control commands thereto;

the processor controlling transmitter and receiver operation during a connect sequence with a remote modem to effect an exchange of control frame information therebetween and thereafter controlling transmitter and receiver operation to effect data communication with the remote modem based upon the data transmission demands by monitoring the data going to the transmit data buffer and providing a mode control command to the transmitter to select the higher-speed, half-duplex mode upon determining a predetermined number of characters in the buffer for communication and providing a mode control command to the transmitter to select the lower-speed, full-duplex mode upon determining that insufficient data is in the buffer to require higher-speed operation.

6. The modem of claim 5 wherein the processor further monitors the receive signal to determine a request by the remote modem for higher-speed operation and provides a control command to the receiver to accept the remote modem transmit signal in a higher-speed, half-duplex mode.

7. The modem of claim 5 wherein the processor further monitors the receive signal to determine a request by the remote modem for lower-speed operation and provides a control command to the receiver to accept the remote modem transmit signal in a lower-speed, full-duplex mode.

8. Apparatus for communication of data over a telephone line, comprising:

a receiver for accepting a transmit signal of data or control frame information over the telephone line and providing a receive signal;

said receiver being selectively operable to accept a transmit signal in either a higher-speed, half-duplex mode or a lower-speed, full-duplex mode in response to a mode control command; and

a control circuit coupled to the receiver to obtain the receive signal of control frame information,

said control circuit for providing the mode control command to the receiver to select the lower-speed, full-duplex mode or the higher-speed, half-duplex mode based upon a receive signal of control frame information.

9. The apparatus of claim 8 further comprising:

a transmitter for placing a transmit signal on a telephone line.