High speed two wire modem

• US 5,347,539 A
• Filed: 01/15/1993
• Issued: 09/13/1994
• Est. Priority Date: 04/15/1991
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Codex Corporation (Motorola Solutions, Inc.)
• Inventors: Mukherjee, Aniruddha, Moran, John L. III, Sridhar, Manickam R.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Kobayashi, Duane
• Application Number:
  US08/004,037
• Time in Patent Office: 606 Days
• Field of Search: 375/7, 375/8, 375/38, 375/40, 370/24, 370/32, 370/54, 455/62, 455/69, 340/825.01, 371/68.1, 371/68.2
• US Class Current: 375/222
• CPC Class Codes: H04L 1/22 using redundant apparatus to increase reliability
• CPC Class Codes: H04L 5/143 for modulated signals H04L5/1469 takes precedence

Abstract

A two wire modem selects a carrier frequency in a baud rate from a predetermined plurality of carrier frequencies and baud rates to communicate with another modem over a communication media in a full duplex mode based on signal and echo characteristics of the communication media estimated by the modem. In addition, the processes of estimating channel characteristics and estimating range are combined in a common start up procedure comprising a plurality of successive time segments for a call modem to communicate with an answer modem over a communication media. Still further, a method is provided for switching from a primary communication media connection to a secondary connection of a data communications network for communication by first and second modems coupled to the network. More specifically, when a failure is detected in the primary connection, the secondary connection is qualified before switching thereto. Similarly, while communicating over the secondary connection, the primary connection is qualified so that communication may be restored thereto at some later time.

Claims

1. In a data communications network, method of switching between primary and secondary communication media connections of said network, which connections are used for communication by first and second modems coupled to said network, said method comprising the steps of:

(a) communicating data between said first and second modems over said primary communication media connection;

(b) detecting a failure in said primary connection;

(c) in response to said failure detection, qualifying a secondary communication media connection, wherein qualifying a secondary communication media connection includes the steps of;

(c1) selecting one secondary connection from a plurality of secondary connections;

(c2) determining if said selected secondary connection can support communication at a desired combination of carrier frequency, baud rate and data a bit rate in order to accept said selected secondary connection;

(c3) qualifying said selected secondary connection upon acceptance; and

(c4) upon rejection of said selected secondary connection, selecting another secondary connection of said plurality and repeating the steps of (c2) through (c4);

(d) switching communication of said first and second modems from said failed primary to said qualified secondary communication media connection;

(e) while communicating data between said first and second modems over said qualified secondary communication media connection, qualifying said primary communication media connection, wherein qualifying said primary communication media connection includes the steps of;

(e1) determining if said primary connection can support communication at a desired combination of carrier frequency, baud rate and data bit rate in order to accept said primary connection;

(e2) qualifying said primary connection upon acceptance; and

(e3) upon rejection, maintain the communication of data over said selected secondary connection; and

(f) restoring communication of said first and second modems from said secondary to said qualified primary communication media connection and repeating step (a).

2. The method in accordance with claim 1 wherein the primary connection being communicated over by the first and second modems is a leased line connection.

3. The method in accordance with claim 1 wherein the secondary connection being switched to is a dial-up line connection.

4. The method in accordance with claim 1 wherein step (c2) includes determining if the selected secondary connection can support a minimum data bit rate at a prespecified carrier frequency and baud rate for acceptance.

5. The method in accordance with claim 4 wherein step (k) includes determining if the primary connection can support a minimum data bit rate at a prespecified carrier frequency and baud rate for acceptance.