TDMA satellite communication method and system

• US 5,065,398 A
• Filed: 05/15/1989
• Issued: 11/12/1991
• Est. Priority Date: 05/16/1988
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Takashima, Hideo
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Marcelo, Melvin
• Application Number:
  US07/352,029
• Time in Patent Office: 911 Days
• Field of Search: 370/94.1, 370/95.1, 370/95.3, 370/104.1, 370/17, 370/97
• US Class Current: 370/230
• CPC Class Codes: H04B 7/212 Time-division multiple access [TDMA]
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 28/10 Flow control between communication endpoints
• CPC Class Codes: H04W 28/26 Resource reservation
• CPC Class Codes: H04W 74/00 Wireless channel access
• CPC Class Codes: H04W 84/06 Airborne or Satellite Networks space-based or airborne stations H04B7/185

Abstract

A subpacket control system used in a time division multiple access system in which a hub station communicates with a plurality of terminal stations via a satellite. When a datum to be transmitted from a terminal station to a hub station has a length exceeding one slot length, the datum is divided into subpackets each having one time slot length, and subpacket information indicating the sequential number of each subpacket in the subpackets is added to the subpacket. A plurality of subpackets are transmitted to the hub station without waiting for a return of an answer back with respect to a first subpacket. On the basis of the subpacket information, the hub station controls reservation access permission.

Claims

1. A terminal station for satellite communication comprising:

first means for dividing a packet datum having a length of at least two time slots to be transmitted to a hub station into packet data which each have a length of one time slot and for holding the packet data;

second means for adding a header and subpacket information indicating a sequential number of one of the packet data to each of the packet data held in said first means to form a subpacket;

third means for transmitting subpackets produced by said second means to the hub station one at a time or a plurality of subpackets at a time;

fourth means for receiving a signal indicating a traffic quantity representative of traffic loading from the hub station;

fifth means for producing and holding at least one copy of one of the packet data to be transmitted emergently to the hub station;

sixth means for adding a header and subpacket information indicating a sequential datum number to each data packet copy held by said fifth means to form a subpacket; and

seventh means for transmitting at least one subpacket to the hub station one at a time or a plurality of subpackets at a time.

2. A hub station for satellite communication system comprising:

first means for receiving at least one subpacket transmitted from a terminal station;

second means or discriminating a number of subpackets which are not yet received by said first means by analyzing subpacket information added to a subpacket received by said first means; and

third means for permitting reservation access to said terminal station based on information discriminated by said second means.

3. A hub station for satellite communication system according to claim 2, further comprising:

fourth means for monitoring a number of subpackets transmitted from a plurality of terminal stations and for detecting a traffic quantity representative of traffic loading of data; and

fifth means for transmitting the traffic quantity detected by said fourth means to each of said plurality of terminal stations as a signal.

4. A satellite communication system comprising:

(a) a plurality of terminal stations each comprising;

first means for dividing a datum having a length of at least two time slots to be transmitted via a satellite into a plurality of data which each have a length of one time slot and for holding the plurality of data;

second means for adding a header and a sequential number representing where a datum is positioned in relation to a first position of each of the plurality of data held by said first means and thereby producing a plurality of subpackets; and

third means for transmitting said plurality of subpackets; and

(b) a hub station comprising;

fourth means for receiving subpackets transmitted from a first one of the terminal stations;

fifth means for discriminating a number of subpackets which are not yet received by said fourth means by analyzing sequential information added to the subpackets received by said fourth means; and

sixth means for permitting reservation access with respect to said first terminal station based on discrimination information supplied from said fifth means,

wherein said first terminal station comprises seventh means for transmitting subpackets produced by said second means one by one or based on reservation access permitted by said sixth means to said hub station.

5. In a satellite communication system including a hub station and a plurality of terminal stations, wherein said hub station includes:

first means for receiving at least one subpacket transmitted from at least one of said terminal stations;

second means or discriminating a number of subpackets which are not yet received by said first means from said at least one terminal station by analyzing subpacket information added to a subpacket received by said first means;

third means for permitting reservation access to said at least one terminal station based on information discriminated by said second means;

fourth means for monitoring the number of subpackets transmitted from said plurality of terminal stations and for detecting a traffic quantity representative of traffic loading of data transmitted from all of said plurality of terminal stations to said hub stations; and

fifth means for transmitting the traffic quantity detected by said fourth means to each of said plurality of terminal stations as a signal;

a satellite communication method comprising the steps of;

detecting at said at least one terminal station the traffic quantity representative of traffic loading of data transmitted from all of the plurality of terminal stations to the hub station, said traffic quantity being returned to said at least one terminal station by the hub station; and

controlling a number of copies of an emergency datum according to said traffic quantity.

6. A satellite communication method according to claim 5, further comprising the steps of:

converting a packet datum transmitted from each terminal station to the hub station into subpackets which each have a predetermined slot length;

transmitting a first predetermined number of subpackets or only one subpacket included in said converted subpackets to the hub station when the traffic quantity is below a predetermined level; and

collecting together and transmitting a second predetermined number of subpackets included in said converted subpackets when the traffic quantity is above a predetermined level, said second predetermined number being greater than said first predetermined number.

7. A satellite communication method according to claim 5, further comprising the steps of:

converting a packet datum transmitted from each terminal station to the hub station into subpackets which each have a predetermined slot length;

collecting together and transmitting a first predetermined number of subpackets included in said converted subpackets when the traffic quantity is below a predetermined level, said

transmitting a second predetermined number of subpackets or only one subpacket included in said converted subpackets to the hub station when the traffic quantity is above a predetermined level, said second predetermined number being less than said first predetermined number.

8. A satellite communication method used in a system for communication between a hub station and a plurality of terminal stations via a satellite, the method comprising the steps of:

converting a packet datum into subpackets each having a predetermined slot length and transmitting the subpackets form at least one of said terminal stations to the hub station via the satellite; and

transmitting from said at least one terminal station, within a time slot predetermined by said hub station, a packet to be received by said hub station when said hub station has received at least one packet datum contained in packet data which has been converted into subpackets and transmitted to said hub station.

9. A satellite communication method used in a system for communication between a hub station and a plurality of terminal stations via a satellite, the method comprising the steps of:

producing at least one copy of an emergency datum to be transmitted emergently from a terminal station to the hub station

converting each copy into a packet;

transmitting at least one of said packets; and

terminating communication to the hub station of the packets resulting form said converting of said emergency datum copies when the hub station has received at least one of said transmitted packets.

10. A satellite communication method used in a system for communication between a hub station and a plurality of terminal stations via a satellite, the method comprising the steps of:

discriminating a degree of emergency of a datum to be transmitted emergently from a terminal station to the hub station upon occurrence of such a datum;

producing a first predetermined number of copies of said emergency datum, converting respective copies of said first predetermined number of copies into subpackets, and transmitting the resultant subpackets when the degree of emergency is high; and

maintaining said emergency datum as it is or producing only a second predetermined number of copies of said emergency datum, converting each copy of said second predetermined number of copies into a subpacket, and transmitting the resultant subpackets converted from said second predetermined number of copies when the degree of emergency is low.

11. A method of satellite communication in a star type network including a hub station and a plurality of terminal stations, the method comprising the steps of:

(a) at an origination terminal station from among the plurality of terminal stations;

dividing an accepted datum into a plurality of data having a predetermined length;

forming each of said plurality of data into a data subpacket by combining each of said plurality of data with subpacket information including an identity of a source and a destination of each of said plurality of data, a sequence number of each of said plurality of data, and a division number of said plurality of data divided from said accepted datum;

determining a number of at least two data subpackets to be transmitted to said hub station; and

transmitting said data subpackets in randomly selected time slots, except for time slots which have already been reserved, before receiving an acknowledgement for a first one of said data subpackets, said time slots being periods between time references transmitted from said hub station;

(b) at said hub station;

receiving data subpackets transmitted from said origination terminal station from among the plurality of terminal stations;

storing said subpacket information and transmitting an acknowledgement signal to said origination terminal station;

calculating a number of data subpackets not received by said hub station from said origination terminal station to form a non-received data subpacket number representative of data subpackets not received by said hub station form said origination terminal station based on a sequence number of successfully received data subpackets and a division number of data subpackets resulting from division;

assigning for said data subpackets not received by said hub station from said origination terminal station a calculated number of time slots which have not been reserved; and

transmitting time slot assignment information including a number of assigned time slots, a sequence number of nonreserved data subpackets and a division number to said origination terminal station; and

(c) at said origination terminal station;

receiving said time slot assignment information; and

retransmitting data subpackets not successfully received at said hub station to said hub station.

12. A method of satellite communication according to claim 11, further comprising the step of transmitting data subpackets which have not yet been transmitted in time slots notified in said time slot assignment information to said hub station from said origination terminal station.

13. A method of satellite communication according to claim 11, wherein said number determining step at said origination terminal station from among the plurality of terminal stations is made based on traffic loading information representative of a satellite communication traffic quantity received from said hub station.

14. A method of satellite communication in a terminal station for communicating with a hub station comprising the steps of:

dividing an accepted datum into a plurality of data having a predetermined length;

forming each of said plurality of data into a data subpacket by combining each of said plurality of data with subpacket information including an identity of a source and a destination of each of said plurality of data, a sequence number of each of said plurality of data, and a division number of said plurality of data divided form said accepted datum;

determining a number of at least two data subpackets to be transmitted to said hub station;

transmitting said data subpackets in randomly selected time slots, except for time slots which have already been reserved, before receiving an acknowledgement for a first one of said data subpackets, said time slots being periods between time references transmitted from said hub station;

receiving time slot assignment information including a number of assigned time slots, a sequence number of non-reserved data subpackets representative of a number of data subpackets not received by said hub station from an originating terminal station and a division number from said hub station; and

retransmitting data subpackets not successfully received at said hub station.

15. A method of satellite communication in a star type network including a hub station and a plurality of terminal stations, the method comprising the steps carried out at one of the plurality of terminal stations of:

producing at least one copy of an accepted datum to be transmitted emergently from said terminal station to said hub station based on traffic loading information including a traffic quantity representative of traffic loading transmitted from said hub station;

forming said at least one copy of the accepted datum into at least one subpacket by combining said at least one subpacket with subpacket information including an identity of a source and a destination of said at least one subpacket, a sequence number of said at least one subpacket, and a number of said at least one copy; and

transmitting a subpacket in a randomly selected time slot exclusive to a time slot notified from said hub station which has already been reserved.

16. A method of satellite communication in a star type network according to claim 15, further comprising the step of:

terminating transmission of said at least one subpacket when the hub station has received at least one subpacket containing an emergency datum.

17. A system for satellite communication in a terminal station for communicating with a hub station comprising:

means for dividing an accepted datum into a plurality of data having a predetermined length;

means for forming each of said plurality of data into a data subpacket by combining each of said plurality of data with subpacket information including an identity of a source and a destination, a sequence number of each of said plurality of data, and a division number of said plurality of data divided from said accepted datum;

means for determining a number of at least two data subpackets to be transmitted to said hub station;

means for transmitting said data subpackets in randomly selected time slots, except for time slots which have already been reserved, before receiving an acknowledgement for a first one of said data subpackets, said time slots being periods between time references transmitted from said hub station;

means for receiving time slot assignment information including a number of assigned time slots, a sequence number of non-reserved data subpackets representative of a number of data subpackets not received by said hub station from an originating terminal station, and a division number from said hub station; and

means for retransmitting data subpackets not successfully received at said hub station.