Method and apparatus for segmentation, reassembly and inverse multiplexing of packets and ATM cells over satellite/wireless networks

• US 20040179486A1
• Filed: 03/26/2004
• Published: 09/16/2004
• Est. Priority Date: 07/15/1997
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Hariharan, Moorthy N., Agarwal, Anil K., Patankar, Shekhar V., Borkar, Udayan N.
• Granted Patent: US 7,443,814 B2
• Time in Patent Office: Days
• US Class Current: 370/316
• CPC Class Codes: H03M 13/15 Cyclic codes, i.e. cyclic shifts of codewords produce other codewords, e.g. codes defined by a generator polynomial, Bose-Chaudhuri-Hocquenghem [BCH] codes H03M13/17 takes precedence
• CPC Class Codes: H03M 13/1515 Reed-Solomon codes
• CPC Class Codes: H03M 13/23 using convolutional codes, e.g. unit memory codes
• CPC Class Codes: H03M 13/29 combining two or more codes or code structures, e.g. product codes, generalised product codes, concatenated codes, inner and outer codes
• CPC Class Codes: H03M 13/35 Unequal or adaptive error protection, e.g. by providing a different level of protection according to significance of source information or by adapting the coding according to the change of transmission channel characteristics
• CPC Class Codes: H03M 13/6312 Error control coding in combination with data compression
• CPC Class Codes: H03M 7/30 Compression speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N; Expansion; Suppression of unnecessary data, e.g. redundancy reduction
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04B 7/18532 Arrangements for managing transmission, i.e. for transporting data or a signalling message
• CPC Class Codes: H04B 7/1858 Arrangements for data transmission on the physical system, i.e. for data bit transmission between network components
• CPC Class Codes: H04B 7/18582 Arrangements for data linking, i.e. for data framing, for error recovery, for multiple access
• CPC Class Codes: H04J 3/0608 Detectors therefor, e.g. correlators, state machines
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control
• CPC Class Codes: H04L 12/5601 : Transfer mode dependent, e.g. ATM
• CPC Class Codes: H04L 2012/5607 : Radio
• CPC Class Codes: H04L 2012/5608 : Satellite
• CPC Class Codes: H04L 2012/5616 : Terminal equipment, e.g. codecs, synch.
• CPC Class Codes: H04L 2012/5627 : Fault tolerance and recovery
• CPC Class Codes: H04L 2012/5632 : Bandwidth allocation
• CPC Class Codes: H04L 2012/5647 : Cell loss
• CPC Class Codes: H04L 2012/5649 : Cell delay or jitter
• CPC Class Codes: H04L 2012/5653 : using the ATM adaptation layer [AAL]
• CPC Class Codes: H04L 2012/5662 : Macrocells or frames
• CPC Class Codes: H04L 2012/5675 : Timeslot assignment, e.g. TDMA
• CPC Class Codes: H04L 5/023 : Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04L 5/06 : the signals being represented by different frequencies combined with time-division multiplexing H04L5/26
• CPC Class Codes: H04L 7/048 : using the properties of error detecting or error correcting codes, e.g. parity as synchronisation signal
• CPC Class Codes: H04Q 11/0478 : Provisions for broadband connections
• CPC Class Codes: H04W 24/00 : Supervisory, monitoring or testing arrangements
• 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 8/26 : Network addressing or numbering for mobility support
• CPC Class Codes: H04W 84/06 : Airborne or Satellite Networks space-based or airborne stations H04B7/185

Abstract

A method of transmitting information arranged in packets from one location to a second location via a wireless/satellite network, comprising: (a) examining each packet to determine whether its size is equal to a minimum (STEP 11A1) and (STEP 11A2); (b) if a minimum size, generating a first SAR header (STEP 11A4) and applying the header to packet to form a SAR segment (STEP 11A7); (c) if greater than a minimum size, dividing the packet into uniform sized segments (STEP 11A5), generating a second SAR header unique for each segment (STEP 11A6) and applying the header to respective segment to form SAR segments (STEP 11A7); (d) forwarding the SAR segments to modems for transmission to terminals at the second location (STEP 11A7).

Claims

1. A communication system for efficiently transmitting information signals that were formatted in variable sized packets of more than a minimum size by using time division transmission of packet segments and allocating available bandwidth on demand, said system comprising:

a satellite/wireless network;

at least two sites, each comprising a plurality of terminals operative to transmit and receive signals via said satellite/wireless network and a local area network for interconnecting said terminals at a common site, each said terminals comprising;

(a) a modem for transmitting signals from a terminal on predetermined channels having a predetermined bandwidth;

(b) means for time dividing data signals input to said terminal from an external location and for assembling said time divided data signals as bursts within repeated frames, each frame having a unique frame header;

(c) means for dividing information signals arranged in variable sized packets into a plurality of segments;

(d) means for combining each segment in said plurality of segments with a unique segment and reassembly header to form a SAR segment;

(e) means for combining said SAR segments representing a single packet with a unique frame header to form a SAR frame; and

(f) means for selectively appending a terminal ID header to each said SAR frame for transmission in a burst from a modem.

2. The communication system as set forth in claim 1 wherein each terminal further comprises:

(g) means for detecting said SAR frame and for dividing said SAR frame into SAR segments;

(h) means for rearranging the segments in said SAR segments on the basis of said SAR header; and

(i) means for reassembling said packets on the basis of said rearranged segments.

3. The communication system as set forth in claim 2 further comprising means for receiving a SAR frame on the basis of said terminal ID information.

4. The communication system as set forth in claim 2 wherein said SAR frame comprises information defining the total length of said plurality of SAR Segments representing a single packet.

5. The communication system as set forth in claim 2 wherein said SAR segment comprises at least a signal identifying the packet sequence number for said segment.

6. The communication system as set forth in claim 2 wherein said SAR segment comprises at least a signal identifying a SAR id of such header.

7. The communication system as set forth in claim 2 wherein said SAR segment comprises at least a signal indicating whether a given segment is first or last among said plurality of segments defining a variable size packet.

8. The communication system as set forth in claim 2 wherein said SAR segment comprises at least a signal identifying at least one receiving modem for said packet.

9. The communication system as set forth in claim 2 wherein said terminal ID header comprises at least one of control group, site and unit information.

10. The communication system as set forth in claim 2 wherein said SAR header comprises one byte having identification information about a sending terminal and a receiving terminal.

11. The communication system as set forth in claim 10 wherein said SAR segment is for point to point bursts between sites having only one terminal each.

12. The communication system as set forth in claim 1 further comprising means for detecting the needed bandwidth for transmitting information signals and for allocating segments of a single packet to respective ones of multiple modems.

13. The communication system as set forth in claim 2 further comprising a central network controller for assigning bandwidth among plural modems on a per packet basis.

14. The communication system as set forth in claim 2 further comprising a controller distributed among plural modems for assigning bandwidth among plural modes on a per packet basis.

15. The communication system as set forth in claim 2 further comprising means for filling a SAR segment with fill data when said packet does not have sufficient data to completely fill a segment.

16. The communication system as set forth in claim 2 wherein said SAR segment has a uniform size data content.

17. The communication system as set forth in claim 16 wherein said size is identical to the size of an ATM cell.

18. The method of transmitting information arranged in packets from one location to a second location via a wireless/satellite network, comprising:

(a) examining each packet to determine whether its size is equal to a minimum;

(b) if a minimum size, generating a first SAR header and applying said header to said packet to form a SAR segment;

(c) if greater than a minimum size, dividing said packet into a plurality of segments having a uniform size, generating a second SAR header that is unique for each segment and applying said header to a respective one of said segments to form SAR segments;

(d) forwarding said SAR segments to one or more modems for transmission to at least one terminal at said second location.

19. The method of transmitting information as set forth in claim 18 further comprising:

(e) sorting said SAR segments by at least one of carrier id, burst position in frame and channel in burst;

(f) sending said SAR segments to a predetermined modem;

(g) determining whether the source and destination ID for segments and bursts are identical; and

(h) on the basis of the identity of the unit, site and control group, generating burst and identity information for transmission to said second site.

20. A communication method as set forth in claim 19, wherein said packets comprise ATM cells.

21. A communication method as set forth in claim 19, wherein said packets comprise frame relay packets.

22. A communication method as set forth in claim 19, wherein said packets comprise at least one of ATM cells and frame relay packets.

23. A segmentation and reassembly cell comprising a segment of a packet and a header comprising at least a packet sequence number for uniquely identifying a packet to which said segment relates, a SAR id for uniquely identifying the segment among all segments derived from the packet, and a destination id for uniquely identifying the destination for the packet.

24. A segmentation and reassembly cell as set forth in claim 23 further comprising a first and last segment indicator.

25. A communication method for reassembling segments transmitted by a satellite/wireless network in a time divided manner by discrete bursts that identify the terminals by at least one of unit, site and control group, comprising:

selecting a modem and receiving a burst at said selected modem on the basis of common addresses in said burst;

sorting segments within burst received by said modem to restore the original order of the segments prior to transmission;

resequencing said sorted segments in a queue at a selected one of a plurality of locations on the basis of a burst slot and key; and

combining said segments at each of said plurality of locations to reassemble a packet.

26. The method as set forth in claim 25 wherein said resequencing step comprises computing a burst slot and composing a key for arranging said segments into a queue.

27. The method as set forth in claim 25 wherein segments received in bursts are processed in the order received in the burst.