Random access communication system with contention scheduling of subpacketized data transmissions and scheduled retransmission of unsuccessful subpackets

• US 4,745,599 A
• Filed: 01/05/1987
• Issued: 05/17/1988
• Est. Priority Date: 01/05/1987
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Raychaudhuri, Dipankar
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Scutch, III, Frank M.
• Application Number:
  US07/000,424
• Time in Patent Office: 498 Days
• Field of Search: 370/60, 370/94, 370/110.1, 370/85, 370/104, 370/93, 340/825.5
• US Class Current: 370/348
• CPC Class Codes: H04B 7/18528 Satellite systems for providing two-way communications service to a network of fixed stations, i.e. fixed satellite service or very small aperture terminal [VSAT] system
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control
• CPC Class Codes: H04L 1/188 Time-out mechanisms
• CPC Class Codes: H04L 1/1887 Scheduling and prioritising arrangements
• CPC Class Codes: H04W 74/02 Hybrid access
• CPC Class Codes: Y10S 370/913 Wireless or radio

Abstract

A random access communication system forms messages to be transmitted into subpackets of fixed duration. A message packet includes two or more subpackets. Each subpacket includes information relating to the source transmitter-receiver and the number of subpackets in the message. The subpackets of the message packet are transmitted contiguously over the transmission path in a contention mode. Some subpackets are successfully received and some are lost due to collisions. After a period of asynchronous contention operation, a predetermined number of subpackets are successfully received, and the system switches to a short-term synchronous, scheduled operating mode. In the scheduled operating mode, those transmitter-receivers which were the sources of message packets including some successful and some unsuccessful subpackets retransmit the data from the unsuccessful subpackets, ordering themselves in accordance with the order of receipt of successful subpackets. The system capacity is high, average delay is short and continuous global synchronization is not required.

Claims

1. A method for burst communication among a plurality of similar associated transmitter-receivers by way of a transmission path having a time delay between any transmitter and any receiver which is longer than the duration of an information packet, the method comprising the steps at each transmitter-receiver of:

accepting at a source transmitter-receiver offered information to form accepted information which is to be transmitted to at least one destination transmitter-receiver;

forming said accepted information into a plurality of sequential information subpackets, each of predetermined duration;

determining the number of said information subpackets in said plurality of sequential information subpackets to produce a length-representative word;

associating with each of said information subpackets of said plurality of sequential information subpackets control information comprising said length-representative word, and words representing the identities of said source and destination transmitter-receivers, to produce combined subpackets;

selecting a random time during times in which said source transmitter-receiver is enabled for initiation of nonscheduled transmissions;

transmitting at least one of said combined subpackets of said sequence of said combined subpackets into the sending end of said transmission path beginning at said random time to produce transmitted combined subpackets;

receiving transmitted combined subpackets from the receiving end of said transmission path in the form of own combined subpackets originating from the same transmitter-receiver by which they are received, and other combined subpackets originating from transmitter-receivers other than the receiving transmitter-receiver;

counting successfully received combined subpackets up to a predetermined number, and ending a nonscheduled operating interval of an operating cycle including a nonscheduled operating mode interval and a scheduled operating mode interval upon reaching said predetermined number of successfully received combined subpackets;

enabling initiation of nonscheduled transmissions during each said nonscheduled operating mode interval;

storing the identities of the source and destination transmitter-receivers, and the associated length-representative word of successfully received combined subpackets;

for those successfully received combined subpackets from each particular source in which said length-representative word is greater than the number of combined subpackets successfully received from said particular source, calculating the number of said combined subpackets from said particular source which are not received to form a nonreceived number, and forming a continuous sum representative of the sum of all such nonreceived numbers;

at each transmitter-receiver whose transmitted combined subpackets resulted in a combination of own combined subpackets which were successfully received and own combined subpackets which were not successfully received, retransmitting at least the data contained in those of its own combined subpackets which were not successfully received as a result of said transmitted combined subpackets, said retransmission beginning at a time following the beginning of said scheduled operating mode interval by a delay which is the sum of an integer multiple of said predetermined duration plus the product of said continuous sum multiplied by said predetermined duration.

2. A method according to claim 1 further comprising the step, at each transmitter-receiver, of:

at a time following transmission of sequential combined subpackets which is in excess of said time delay of said transmission path, in the event that no said own combined subpackets are successfully received, selecting a new random time within the next following nonscheduled operating mode interval and transmitting said sequential combined subpackets beginning at said new random time.

3. A method according to claim 1 further comprising the step of inhibiting new nonscheduled transmissions during said scheduled operating mode interval, while allowing completion of nonscheduled transmissions initiated during the preceding nonscheduled operating mode interval.

4. A method according to claim 3 wherein said nonscheduled transmissions initiated during the preceding nonscheduled operating mode interval, the completion of which is allowed during said scheduled operating mode interval, have a duration equal to one said predetermined duration.

5. A method according to claim 3 wherein said nonscheduled transmissions initiated during the preceding nonscheduled operating mode interval, the completion of which is allowed during said scheduled operating mode interval, have a duration which is an integer multiple of said predetermined duration.

6. A method according to claim 1, wherein at least some of said transmitted combined subpackets which are transmitted in relation to said transmitting step during said nonscheduled mode operating interval are received in relation to said receiving step during said scheduled mode operating interval.

7. A method according to claim 1 wherein said storing step includes the step of storing said identities and said length representative word of said successfully received combined subpackets in order of successful reception.

8. A transmitter-receiver adapted for burst communication among a plurality of similar associated transmitter-receivers by way of a transmission path, comprising:

accepting means adapted to be coupled to a source of offered information for accepting offered information which is to be transmitted, thereby forming accepted information;

forming means coupled to said accepting means for forming said accepted information into a plurality of sequential information subpackets, each of predetermined duration;

determining means coupled to said forming means for determining the number of said information subpackets contained in said plurality of sequential information subpackets, to produce a length-representative word;

associating means coupled to said accepting means, said forming means and said determining means for associating control information with each of said information subpackets of said plurality of sequential information subpackets, said control information comprising said length-representative word, and words representing the identities of the source and destination transmitter-receivers, thereby producing combined subpackets;

random time selection means for selecting a random time during which said source transmitter-receiver is enabled for initiation of nonscheduled transmissions;

transmitting means coupled to said associating means and to said random time selection means and adapted to be coupled to said transmission path for transmitting at least one of said combined subpackets into said transmission path beginning at said random time to produce transmitted combined subpackets;

receiving means adapted to be coupled to said transmission path for receiving said transmitted combined subpackets in the form of own combined subpackets originating from the same transmitter-receiver by which they are received, and other combined subpackets originating from transmitter-receivers other than the receiving transmitter-receiver;

counting means coupled to said receiving means for counting successfully received combined subpackets up to a predetermined number, and for ending a nonscheduled operating interval of an operating cycle including a nonscheduled operating mode interval and a scheduled operating mode interval upon reaching said predetermined number of successfully received combined subpackets;

enabling means coupled to said counting means and to said random time selection means for enabling initiation of nonscheduled transmissions during each said nonscheduled operating mode interval;

storing means coupled to said receiving means for storing the identities of the source and destination transmitter-receivers, and the associated length-representative word of successfully received combined subpackets;

calculating means coupled to said storing means for calculating a nonreceived number representing the number of said combined subpackets which are not received from those particular source transmitter-receivers in which said length-representative word in a successfully received subpacket is greater than the number of combined subpackets successfully received, and for forming a continuous sum representative of the sum of all such nonreceived numbers; and

retransmission means coupled to said calculating means for retransmitting at least the data contained in those of its own combined subpackets which were not successfully received, said retransmission beginning at a time following the beginning of said scheduled operating mode interval by a delay which is the sum of an integer multiple of said predetermined duration plus the product of said continuous sum multiplied by said predetermined duration.

9. A transmitter-receiver according to claim 8, further comprising means for selecting a new random time within the next following nonscheduled operating mode interval in the event that no said own combined subpackets are successfully received as a result of transmission during a nonscheduled operating mode interval, and for transmitting said sequential combined subpackets beginning at said new random time.

10. A transmitter-receiver according to claim 8 further comprising inhibiting means coupled to said counting means for inhibiting new nonscheduled transmissions during said scheduled operating mode interval.

11. A transmitter-receiver according to claim 10, wherein said inhibiting means allows completion of during scheduled operating mode intervals of new transmissions initiated during a nonscheduled operating mode interval.