Data communication apparatus for adjusting frame length and method of operating same

• US 5,307,351 A
• Filed: 08/26/1991
• Issued: 04/26/1994
• Est. Priority Date: 08/26/1991
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Universal Data Systems Incorporated
• Inventors: Webster, James M.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Patel, Ajit
• Application Number:
  US07/749,835
• Time in Patent Office: 974 Days
• Field of Search: 370/110.1, 370/94.1, 370/82, 370/83, 370/24, 370/99, 371/32, 371/33
• US Class Current: 370/470
• CPC Class Codes: H04J 3/14 Monitoring arrangements for SDH/SONET rings H04J3/085
• CPC Class Codes: H04J 3/16 in which the time allocation to individual channels within a transmission cycle is variable, e.g. to accommodate varying complexity of signals, to vary number of channels transmitted H04J3/17, H04J3/24 take precedence
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 1/1867 Arrangements specially adapted for the transmitter end
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

Data communication apparatus (DCA) receives digital data from data terminal apparatus (DTA) and transmits the digital data assembled in the form of frames over a communication medium. Included in the DCA is apparatus for adjusting the length of the data frames being assembled based on a determined degree of impairment of the communication medium. A corresponding method of adjusting the length of the data frames in the data communication apparatus is also included.

Claims

1. Data communication apparatus DCA, interfaceable with data terminal apparatus and a communication medium for exchanging digital data in the form of data frames between the data terminal apparatus and communication medium, each data frame including data frame overhead, said data communication apparatus comprising:

means for interfacing with said data terminal apparatus to receive data therefrom to be transmitted over said communication medium;

means for assembling said received data to form assembled data frames, each of the assembled data frames having a length that is adjustable;

means for transmitting the assembled data frames over the communication medium;

error determining means coupled to the communication medium for determining an error rate of the communication medium; and

means coupled to the error determining means for adjusting the length of the assembled data frames based on said error rate,

wherein the error determining means includes means for determining a number of unacceptable transmissions of assembled data frames over the communication medium;

and wherein the adjusting means includes means for adjusting the length of the assembled data frames based on said number of unacceptable transmissions of assembled data frames over the communication medium,

and wherein the determining means includes;

means for monitoring the communication medium for a retransmit indication corresponding to said unacceptable assembled data frame transmission, thus forming a number of retransmit inductions, said monitoring means causing the assembling means and transmitting means to retransmit the assembled data frame in response to its associated retransmit indication;

and wherein the adjusting means includes means for adjusting the length of the assembled data frames based on the number of retransmit indications, the number of assembled data frames transmitted and the data frame overhead, and wherein the adjusting means includes;

first counting means responsive to the assembling means for determining the number of assembled data frames assembled for transmission;

second counting means responsive to the error determining means for determining the number of retransmit indications; and

setting means for setting a new assembled data frame length for data transmission based on the number of assembled data frames assembled for transmission and the number of retransmit indications.

2. Data communication apparatus interfaceable with data terminal apparatus and a communication medium for exchanging digital data int he form of data frames between the data terminal apparatus and communication medium, each data frame including data frame overhead, said data communication apparatus comprising;

means for interfacing with sad data terminal apparatus to receive data therefrom to be transmitted over said communication medium;

means for assembling said received data to form assembled data frames, each of the assembled data frames having a length that is adjustable;

means for transmitting the assembled data frames over the communication medium;

error determining means coupled to the communication medium for determining an error rate of the communication medium; and

means coupled to the error determining means for adjusting the length of the assembled data frames based on said error rate,

wherein the error determining means includes means for determining a number of unacceptable transmissions of assembled data frames over the communication medium;

and wherein the adjusting mans includes means for adjusting the length of the assembled data frames based on said number of unacceptable transmissions of assembled data frames over the combination medium,

and wherein the determining means includes;

means for monitoring the communication medium for a retransmit indication corresponding to said unacceptable assembled data frame transmission, thus forming a number of retransmit indications, said monitoring means causing the assembling means and transmitting means to retransmit the assembled data frame in response to its associated retransmit indication;

and wherein the adjusting means includes means for adjusting the length of the assembled data frames based on the number of retransmit indication, the number of assembled data frames transmitted and the data frame overhead, and wherein the adjusting means includes;

means for establishing a sliding window of a predetermined number n of assembled data frames assembled for transmission;

counting means for determining the number of retransmit indication over each predetermined group m of assembled data frames of said sliding window;

means for combining the number of counts of the counting means corresponding to each group m of the sliding window thus forming a total number of counts of retransmit indication corresponding to the sliding window; and

means for setting a new assembled data frame length for data transmission based on said total number of counts, the predetermined number n of the sliding window, and the data frame overhead;

wherein n≧

m≧

1.

3. The DCA in accordance with claim 2 wherein the adjusting means further includes storing means including n/m storage locations for storing the corresponding number of counts of the counting means;

and wherein the combining means combines the number of counts of the storing means for the sliding window to obtain the total number of counts.

4. The DCA in accordance with claim 3 including a controlling means for casing the number count of the counting means corresponding to an instant group m of assembled data frames to be stored in an unfilled location of the storage means until all of the locations thereof are filled,

and thereafter, for causing the oldest stored number of counts to be removed from the storing means to make available a storage location for storing the number of counts of the instant group m,

whereby only the number of counts of the counting means corresponding to the immediately preceding n/m groups of assembled data frames are storable in the storing means.

5. The DCA in accordance with claim 2 including a controlling means for causing the combining means and setting means to perform their respective functions for each group m of assembled data frames such that a new total number of counts of retransmit indications is obtained and a new assembled data frame length is settable based thereon for each group m of assembled data frames.

6. The DCA in accordance with claim 2 wherein the setting means includes means for limiting the setting of the new assembled data frame length to a predetermined maximum assembled data frame length.

7. The DCA in accordance with claim 2 wherein the setting means includes means for setting the new assembled data frame length to a predetermined maximum assembled data frame length when the corresponding obtained total number count is below a predetermined minimum number of counts.

8. The DCA in accordance with claim 2 wherein the setting means includes means for setting the new assembled data frame length to a predetermined maximum assembled data frame length when the corresponding obtained total number of counts is zero.

9. In a data communication apparatus interfaceable with data terminal apparatus and a communication medium for exchanging digital data int he form of data frames between the data terminal apparatus and communication medium, each data frame including data frame overhead, a method of adjusting the length of aid data frames comprising the steps of:

interfacing with the data terminal apparatus to receive data therefrom to be transmitted over the communication medium;

assembling the received data to from assembled data frames, each of the assembled data frames having a length that may be adjusted;

transmitting the assembled data frames over the communication medium;

determining an error rate of the communication medium; and

adjusting the length of the assembled data frames based on said error rate;

wherein the step of determining includes a step of determining a number of unacceptable transmissions of assembled data frames over the communication medium;

and wherein the step of adjusting includes a step of adjusting the length of the assembled data frames based on said number of unacceptable transmissions; and

including the steps of;

monitoring the communication medium for a retransmit indication corresponding to an unacceptable assembled data frame transmission; and

effecting the assembling step and transmitting step to retransmit the assembled data frame in response to its associated retransmit indication;

and wherein the step of adjusting includes a step of adjusting the length of the assembled data frames based on the retransmit indications, the assembled data frames transmitted and the data frame overhead; and

wherein the adjusting step includes the steps of;

determining the number of assembled data frames assembled for transmission;

determining the number of retransmit indications; and

setting a new assembled data frame length for data transmission based on the total number of counts of assembled data frames and the number of retransmit indications.

10. In a data communication apparatus interfaceable with data terminal apparatus and a communication medium for exchanging digital data int he form of data frames between the data terminal apparatus and communication medium, each data frame including data frame overhead, a method of adjusting the length of said data frames comprising the steps of:

interfacing with the data terminal apparatus to receive data therefrom to be transmitted over the communication medium;

assembling the received data to form assembled data frames, each of the assembled data frames having a length that may be adjusted;

transmitting the assembled data frames over the communication medium;

determining an error rate of the communication medium; and

adjusting the length of the assembled data frames based on said error rate;

wherein the step of determining includes a step of determining a number of unacceptable transmissions of assembled data frames over the communication medium;

and wherein the step of adjusting includes a step of adjusting the length of the assembled data frames based on said number of unacceptable transmissions; and

including the steps of;

monitoring the communication medium for a retransmit indication corresponding to an unacceptable assembled data frame transmission; and

effecting the assembling step and transmitting step to retransmit the assembled data frame in response to its associated retransmit indication;

and wherein the step of adjusting includes a step of adjusting the length of the assembled data frames based on the retransmit indications, the assembled data frames transmitted and the data frame overhead; and

wherein the step of adjusting includes the steps of;

establishing a sliding window of a predetermined number n of assembled data frames assembled for transmission;

counting the number of retransmit indications over each predetermined group m of assembled data frames of aid sliding window;

combining the total number of counts of the counting step corresponding to each group m of the sliding window to obtain a total number of counts of retransmit indications corresponding to the sliding window; and

setting a new data frame length for data transmission based on said total number of counts, the predetermined number n of the sliding window, and the data frame overhead;

wherein n≧

m≧

1.

11. The method in accordance with claim 10 wherein the adjusting step further includes a step of storing the number of counts of the counting step in n/m storage locations of a storing means;

and wherein the combining step includes a step of combining the total number of counts of the storing means for the sliding window to obtain the total number of counts.

12. The method in accordance with claim 11 including the steps of:

causing the number count of the counting step corresponding to an instant group m of assembled data frames to be stored in an unfilled location of the storing means until all of the locations thereof are filled;

and thereafter, causing the oldest stored number of counts to be removed from the storing means to make available a storage location for storing the number of counts of the instant group m.

whereby only the number of counts of the counting step corresponding to the immediately preceding n/m groups of assembled data frames are storable in the storing means.

13. The method in accordance with claim 10 including the step of causing the combining step and setting step to perform their respective operations for each group m of assembled data frames such that anew total number of counts of retransmit indications is obtained and a new assembled data frame length is settable based thereon for each group m of assembled data frames.

14. The method in accordance with claim 10 wherein the setting step includes a step of limiting the setting of the new assembled data frame length to a predetermined maximum frame assembled data length.

15. The method in accordance with claim 10 wherein the setting step includes a step of setting the new assembled data frame length to a predetermined maximum assembled data frame length when the corresponding obtained total number count is below a predetermined minimum number of counts.

16. The method in accordance with claim 10 wherein the setting step includes a step of setting the new assembled data frame length to a predetermined maximum assembled data frame length when the corresponding obtained total number of counts is zero.