Data communication system

• US 5,297,139 A
• Filed: 06/19/1992
• Issued: 03/22/1994
• Est. Priority Date: 06/19/1991
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Okura, Yoshinori, Okada, Masakazu, Sugimoto, Norihiko, Inada, Shunji
• Primary Examiner(s): Chin, Wellington
• Application Number:
  US07/901,131
• Time in Patent Office: 641 Days
• Field of Search: 375/118, 370/94.1, 370/94.2, 370/60, 370/60.1, 370/85.15, 370/61, 370/84, 370/105.3, 370/108, 370/58.1, 370/58.2, 370/58.3, 370/77, 370/79, 370/84, 370/85.1, 370/85.2 , 370/85.3, 370/85.4, 370/85.5, 370/13, 370/17
• US Class Current: 370/428
• CPC Class Codes: H04J 3/0626 plesiochronous multiplexing systems, e.g. plesiochronous digital hierarchy [PDH], jitter attenuators
• CPC Class Codes: H04J 3/0632 Synchronisation of packets and cells, e.g. transmission of voice via a packet network, circuit emulation service [CES] queuing arrangements in packet switching elements H04L49/90; synchronising systems for the synchronous transmission of a pulse code modulated video signal with one or more other pulse code modulated signals H04N7/56
• CPC Class Codes: H04L 12/6418 Hybrid transport
• CPC Class Codes: H04L 2012/5616 Terminal equipment, e.g. codecs, synch.
• CPC Class Codes: H04L 2012/5649 Cell delay or jitter
• CPC Class Codes: H04L 2012/5682 Threshold; Watermark
• CPC Class Codes: H04L 2012/6489 Buffer Management, Threshold setting, Scheduling, Shaping
• CPC Class Codes: H04Q 11/04 for time-division multiplexing H04Q11/0001 takes precedence
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

In a method of controlling a buffer device, data are received from a communication transmission line, and the received data are written in a buffer device at a predetermined write rate. The data written from the buffer device are started to be read at a predetermined read rate. The quantity of data written and accumulated in the buffer device is compared with a predetermined threshold for a predetermined period from the read start point of time. When it is found as the result of comparison that the quantity of accumulated data is the same as or less than the threshold, the buffer device performs only write of data from the communication transmission line and, when the quantity of accumulated data is larger than the threshold, the buffer device performs both write of data from the communication transmission line and read of data out of the buffer device at the same time during a predetermined period.

Claims

1. A method of controlling writing of data from a communication transmission line of a communication system in a buffer device and reading of the data out of said buffer device, comprising the steps of:

receiving data from said communication transmission line and writing received data in said buffer device at a predetermined write rate;

starting to read the data, written in said buffer device, out of said buffer device at a predetermined read rate;

comparing the quantity of data written and accumulated in said buffer device with a predetermined threshold during a predetermined period from a read start point of time;

writing the data from said communication transmission line by said buffer device when it is found as a result of comparison that the quantity of said accumulated data is the same as or less than said threshold; and

performing both write of data from said communication transmission line and read of data out of said buffer device during said predetermined period when the quantity of said accumulated data is larger than said threshold.

2. A method of controlling a buffer device according to claim 1, further comprising a step of:

performing both write of data from said communication transmission line and read of data out of said buffer device at the same time after the lapse of said predetermined period irrespective of said threshold.

3. A method of controlling a buffer device according to claim 1, wherein said threshold is determined in accordance with a variation quantity of a clock signal, which drives said buffer device, for determining said predetermined write rate or said predetermined read rate.

4. A method of controlling a buffer device according to claim 1, wherein said predetermined period is a period corresponding to one frame period of said data.

5. A method of controlling writing of communication data in a buffer device and reading of said communication data out of said buffer device in a communication system in which a plurality of time slots are provided, said communication data being arranged in reserved ones of said time slots, and said communication data including control information and being propagated in a communication transmission line, comprising the steps of:

receiving said communication data from said communication transmission line and writing said communication data in said buffer device at a predetermined write rate;

starting to read said communication data, written in said buffer device, out of said buffer device at a predetermined read rate;

detecting positions of said reserved ones of said tome slots based on said control information of said communication data;

determining a position where the quantity of said communication data accumulated in said buffer device becomes a minimum based on detected positions of said reserved ones of said time slots;

comparing the quantity of said communication data written and accumulated in said buffer device with a predetermined threshold during the period from a read start point of time until reaching the position where the quantity of data becomes the minimum;

writing said communication data from said communication transmission line in said buffer device when it is found as a result of comparison that the quantity of said accumulated communication data is the same as or less then said threshold; and

writing said communication data from said communication transmission line and reading said communication data out of said buffer device at the same time when the quantity of said accumulated data is larger than said threshold.

6. A method of controlling writing of communication data in a buffer device and reading of said communication date out of said buffer device in a communication system in which a plurality of time slots are provided, said communication data being arranged in reserved ones of said time slots, and said communication data including control information and being propagated in a communication transmission line, comprising the steps of:

receiving said communication data from said communication transmission line and writing said communication data in said buffer device at a predetermined write rate;

starting to read said communication data, written in said buffer device, out of said buffer device at a predetermined read rate;

detecting positions of said reserved ones of said time slots based on said control information of said communication data;

determining a position where the quantity of said communication data accumulated in said buffer device becomes a minimum based on said detected positions of said reserved ones of said time slots;

not performing read of said communication data out of said buffer device during the period from a read start point of time until reaching the position where the quantity of said communication data becomes the minimum; and

performing both write of said communication data from said communication transmission line and read of said communication data out of said buffer device at and after the position where the quantity of said accumulated data becomes the minimum.

7. A buffer device arranged between a communication transmission line and a communication terminal equipment in a communication system for controlling transmission of communication data, comprising:

means for receiving communication data from said communication transmission line;

memory means for storing received communication data;

means form controlling timing of writing received communication data in said memory means at a predetermined write rate;

threshold setting means for designating as a threshold the minimum quantity of communication data accumulated in said memory means; and

means for comparing the quantity of communication data written and accumulated in said memory means with said threshold during a predetermined period from the read start point of time, and prohibiting read of said communication data out of said memory means when the quantity of said accumulated data is the same as or less than said threshold, and permitting read of said communication data out of said memory means at a predetermined read rate when the quantity of said communication data accumulated in said memory means is larger than said threshold.

8. A buffer device according to claim 7, wherein communication data in said communication transmission line are communicated in a plurality of time slots and the communication data are arranged in reserved ones of said time slots, and said buffer device further includes means for detecting said reserved ones of said time slots and applying a signal for write permit to said means for controlling every time said reserved ones of said time slots are detected.

9. A buffer device according to claim 7, wherein communication data in said communication transmission are communicated in a plurality of time slots, said communication data being arranged in reserved ones of said time slots, and said communication data further include data control information, said buffer device further comprising:

means for detecting positions of said reserved ones of said time slots based on said control information of said communication data and determining the position where the quantity of said communication data accumulated in said memory means becomes a minimum based on said detected positions of said reserved ones of said time slots; and

means for comparing the quantity of said communication data written and accumulated in said memory means with said threshold during the period from the read start point of time until reaching the position wherein said communication data quantity becomes the minimum, and prohibiting read said communication of data out of said memory means when the quantity of said accumulated communication data is the same as or less than said threshold and permitting read of said communication data out of said memory means at a predetermined read rate when the quantity of said communication data accumulated in said memory means is larger than said threshold.

10. A communication system having a communication transmission line in which communication data are transmitted and a plurality of communication nodes coupled with said communication transmission line, each of said communication nodes comprising:

means for receiving data from said communication transmission line;

communication terminal equipments coupled with said communication nodes;

a buffer device arranged between said communication receiving means and said communication terminal equipments for controlling transmission of the communication data;

memory means for storing received communication data;

memory means for storing received communication data;

means for controlling timing to write received communication data in said memory means at a predetermined write rate;

threshold setting means for designating as a threshold the minimum quantity of said communication data accumulated in said memory means; and

means for comparing the quantity of said communication data written and accumulated in said memory means with said threshold for a predetermined period from a read start point of time, and prohibiting read of said communication data out of said memory means when the quantity of said accumulated communication data is the same as or less than said threshold, and permitting read of said communication data out of said memory means at a predetermined read rate when the quantity of said communication data accumulated in said memory means is larger than said threshold.