Method of determining automatically the rate of data signals in a modem

• US 4,663,766 A
• Filed: 10/10/1984
• Issued: 05/05/1987
• Est. Priority Date: 10/10/1984
• Status: Expired due to Term

• Current Assignee: Paradyne Corporation (Dasan Networks Incorporated)
• Original Assignee: Paradyne Corporation (Dasan Networks Incorporated)
• Inventors: Bremer, Gordon
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US06/659,288
• Time in Patent Office: 937 Days
• Field of Search: 370/79, 370/84, 375/13, 375/108, 375/111, 375/114, 375/116, 375/121, 375/122, 375/106, 178/63 C, 178/69 M, 328/109, 328/110, 307/522
• US Class Current: 375/225
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 25/0262 Arrangements for detecting the data rate of an incoming signal

Abstract

A method of determining the data rate of signals received on a communication line is disclosed. The method analyzes the training signals which normally precede each data transmission to determine whether they contain a preselected pattern of phase reversals. The presence or absence of the pattern indicates the data rate.

Claims

1. In a data communication system having first and second modems for exchanging data signals at one of a first and a second rate, a method of determining the rate of the signals sent by the first modem comprising:

a. transmitting a sequence of training signals, said training signals being sent only for the purpose of determining the rate of the signals being sent by the first modem and containing no message data interspersed therein from said first modem said sequence comprising a first segment comprising a series of preselected signals;

b. detecting said sequence of training signals at said second modem;

c. initializing a pulse generator which outputs pulses which correspond to the period of training signals having a first data rate;

d. initializing a timing means which operates form the moment said sequence is first detected for a first pre-selected time period which corresponds to the period of said first segment at said first data rate;

e. comparing the training signals received after said first segment with a set of stored constants representation of the first data rate to determine whether they correspond to the pre-selected signals of said second segment; and

f. changing said pulse generator to generate pulses corresponding to the second rate if said received signals do not correspond to said stored constants.

2. The method of claim 1 wherein each data transmission is preceded by a short training sequence if a previous rate is maintained and a long training sequence if a new rate is used.

3. The method of claim 2 wherein said second segment comprises marks.

5. The method of claim 1 wherein each training sequence is selected from a group consisting of a short sequence and a long sequence, each including a first and a second segment, comprising:

initiating said timing means for said first period corresponding to a training period of said first short segment at said first rate;

storing a first pre-selected number of signals received by said second modem after said first period;

comparing the stored signals to said first preset value;

storing a second pre-selected number of signals received by said second modem after said second period corresponding to said first long training signal;

comparing said second stored signals to a second preset value; and

changing said signal timing means when said second stored signals do not correspond to said second preset value.

4. A method of data communication comprising:

a. sending data signals and a carrier signal from a first modem to a second modem at a first rate said second modem including signal timing means for generating pulses at first intervals corresponding to said first rate;

b. interrupting said carrier signal upon the receiving of an appropriate command by said first modem from a channel impairment analyzer, external control means, or DTE;

c. initiating a sequence of training signals from said first to said second modem at one of said first and a second rate, said second rate being slower than said first rate, said training sequence comprising a first segment and a second segment, said training signals being sent only for the purpose of determining the rate of the signals being sent from the first modem to the second modem and containing no message data interspersed therein;

d. initiating a timing means for a first period corresponding to a training period of said first segment at said first rate;

e. storing a pre-selected number of signals received by said modem after said first period;

f. comparing the stored signals to a set of pre-selected stored signals corresponding to said first rate;

g. changing said signal timing means to generate pulses at second intervals corresponding to said second rate when the stored signals do not correspond to said preset value.