Multi-mode modem and data transmission method

• US 5,481,562 A
• Filed: 04/01/1991
• Issued: 01/02/1996
• Est. Priority Date: 11/03/1989
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Microcom Systems Incorporated
• Inventors: Melhorn, Nathan R., Pearson, Gregory, Onarato, Michael F., Richards, Craig A.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Bocure, Tesfaldet
• Application Number:
  US07/678,755
• Time in Patent Office: 1,737 Days
• Field of Search: 375/8, 375/121, 375/107, 375/94, 375/109, 375/222, 375/377, 375/340, 375/356, 375/358, 371/32, 379/93
• US Class Current: 375/222
• CPC Class Codes: H04L 1/0008 by supplementing frame payload, e.g. with padding bits
• CPC Class Codes: H04L 1/18 Automatic repetition systems, e.g. Van Duuren systems
• CPC Class Codes: H04L 69/24 Negotiation of communication capabilities
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A multi-mode modem and a method of transmitting data utilizing the multi-mode modem are disclosed in which different modes of operation may be automatically selected by sending multiple link requests to a receiving modem in order to provide either optimized or non-optimized data transmission according to line conditions.

Claims

1. A method of initiating data telecommunications between at least a first unit of data terminal equipment and a second unit of data terminal equipment, over a communications medium, each of said first unit and said second unit of said data terminal equipment being connected to said communications medium through, respectively, a first modem and a second modem, said first modem operating as an initiating modem when said second modem is operating as a receiving modem and said first modem operating as a receiving modem when said second modem is operating as an initiating modem, at least one of said first and second modems being capable of operating in at least a special mode and a normal mode, said at least one modem operating in (A) said special mode so as to provide for (1) optimized data transmission by pacing the flow of data between said first and second modems, (2) error detection of errors in a transmitted data stream from said initiating modem to said receiving modem and (3) the automatic re-transmission of said transmitted data stream by said initiating modem to said receiving modem when an error is detected, and (B) said normal mode so as to provide for the direct, non-optimized transmission of a data stream without any error detection analysis of the data stream or automatic re-transmission of the transmitted data stream by said initiating modem to said receiving modem, said method comprising the steps of:

(a) establishing a physical connection between said initiating modem and said receiving modem;

(b) transmitting a data stream of data characters from said initiating modem to said receiving modem over said communication medium;

(c) examining in said receiving modem a next received character in said data stream transmitted by said initiating modem to said receiving modem;

(d) attempting to establish a special mode link between said initiating and receiving modems if said next received character examined by said receiving modem is a special mode indicating character that completes a special mode link request of the type including a plurality of special mode indicating characters, and attempting to establish a normal mode link if said next received character is a normal mode indicating character;

(e) repeating steps (c) and (d) after fetching another data character from said data stream until a complete sequence of special mode indicating characters of a special mode link request is detected, or until a normal mode indicating character is detected, or until a first preselected period of time has elapsed;

(f) repeating steps (c) and (d) for a second preselected period of time upon the detection within said first preselected period of time of a portion of a special mode link request to provide said receiving modem with an additional opportunity to detect either a complete special mode link request, or said normal mode indicating character; and

(g) continuing the transmission by said initiating modem of said stream of data under either said special mode or said normal mode until all of said data stream has been transmitted.

2. In a method of operating a multi-mode modem as a receiving modem in a data telecommunications system, said multi-mode modem being capable of operating in a special mode or a normal mode, said multi-mode modem providing (A) when operating in said special mode:

(1) optimized data transmission that paces the flow of data between an initiating modem and said multi-mode modem and (2) error detection of errors in a transmitted data stream and automatic re-transmission of said data stream by said initiating modem when an error occurs, and (B) when operating in said normal mode;

direct, non-optimized data transmission that provides transmission of the data stream without error detection of errors in the transmitted data stream and without automatic re-transmission of said data stream by said initiating modem when an error occurs, wherein a first time period is allotted for the detection of a special mode indicating character in said data stream such that at the expiration of said first time period a normal mode link is established if said special mode indicating character is not detected, the improvement comprising the steps of;

(a) sending more than one link request from said initiating modem to said multi-mode modem operating as a receiving modem; and

(b) upon detection within said first time period by said multi-mode modem of at least a portion of a special mode link request having a sequence of special mode indicating characters, providing a second time period after said initial time period to provide said receiving modem with an additional opportunity to detect a complete special mode link request.

3. A multi-mode modem for connecting between a unit of data terminal equipment and a communications medium to facilitate data telecommunications, said multi-mode modem operating as a receiving modem for receiving data transmitted across said communications medium from a second modem operating as an initiating modem, said multi-mode modem being capable of operating in a special mode or a normal mode, said multi-mode modem providing for (A) when operating in said special mode:

(1) the optimized transmission of data by pacing the flow of data between said multi-mode modem and said initiating modem, (2) the detection of errors in a transmitted data stream from said initiating modem to said multi-mode modem and (3) the automatic re-transmission of said transmitted data stream by said initiating modem when an error is detected, and (B) when operating in said normal mode the direct, non-optimized transmission of data from said initiating modem to said multi-mode modem in order to provide for the simple transmission of data without any error detection analysis of the data stream or associated automatic re-transmission of said data stream when an error is detected, said multi-mode modem comprising;

(a) means for receiving a transmitted stream of data characters from said initiating modem;

(b) detection means for detecting at least one special mode indicating character or a normal mode indicating character in said received stream of data characters;

(c) first timing means cooperative with said detection means, for allotting an initial first time period during which said detection means may detect in said received stream of data characters a special mode link request having a sequence of special mode indicating characters;

(d) second timing means, cooperative with said detection means, for providing a second time period if a portion of a special mode link request is detected by said detection means during said first time period, the second time period being for detecting additional special mode indicating characters in said received stream of data characters until a complete special mode link request is detected, or until said normal mode indicating character is detected;

(e) means for causing said multi-mode modem to operate in said special mode upon detecting said complete special mode link request; and

(f) means for causing said multi-mode modem to operate in said normal mode upon detecting said normal mode indicating character or upon the expiration of said initial and extended time period.

4. A data telecommunications system for providing data communications between at least a first unit of data terminal equipment and a second unit of data terminal equipment over a communication medium, said system comprising:

a first modem connected between said first unit of data terminal equipment and said communication medium and a second modem connected between said second unit of data terminal equipment and said communication medium equipment, at least one of said first and second modems operating as a receiving modem capable of operating in either a special mode or a normal mode, said other of said first and second modems operating as an initiating modem when said one of said first and second modems is operating as a receiving modem, said receiving modem providing for (A) when operating in said special mode;

(1) the optimized transmission of data by pacing the flow of data between said receiving modem and said initiating modem, (2) the detection of errors in a transmitted data stream from said initiating modem to said receiving modem, and (3) the automatic retransmission of said transmitted data stream by said initiating modem when an error is detected, and (B) when operating in said normal mode the direct, non-optimized transmission of data from said initiating modem to said receiving modem in order to provide for the simple transmission of data without any error detection analysis of the data stream or associated automatic re-transmission of said data stream when an error is detected, said receiving modem being capable of operating in said special and normal modes and including;

(a) means for receiving a stream of data characters transmitted from said initiating modem;

(b) detection means, cooperative with said means for receiving, for detecting a special mode link request having a plurality of special mode indicating characters, and for detecting a normal mode indicating character in said received stream of data characters;

(c) first timing means, cooperative with said detection means, for allotting a first time period during which said receiving modem may detect a sequence of special mode indicating characters in said received stream of data characters;

(d) second timing means, cooperative with said detection means for providing a second time period when said detection means may detect a sequence of special mode indicating characters in said received stream of data characters, said second timing means adding said second time period to said initial time period only upon detection by said detection means of receipt of a portion of a special mode link request during said first time period to provide said receiving modem with an opportunity to complete detection of either said special mode link request, or said normal mode indicating character;

(e) means for causing said receiving modem to operate in said special mode upon detecting said special mode link request; and

(f) means for causing said receiving modem to operate in said normal mode upon detecting said normal mode indicating character or upon the expiration of said initial and extended time period.