PACKET-SWITCHED NETWORK SYNCHRONIZATION SYSTEM AND METHOD

• US 20080151940A1
• Filed: 12/21/2006
• Published: 06/26/2008
• Est. Priority Date: 12/21/2006
• Status: Active Grant

• Current Assignee: Edgewater Computer Systems Inc.
• Original Assignee: Edgewater Computer Systems Inc.
• Inventors: Wang, Yu, Fanson, John
• Granted Patent: US 7,664,144 B2
• Time in Patent Office: Days
• US Class Current: 370/503
• CPC Class Codes: H04L 27/2656 Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
• CPC Class Codes: H04L 27/2689 Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
• CPC Class Codes: H04L 7/042 Detectors therefor, e.g. correlators, state machines digital correlators in general G06F17/15

Abstract

A synchronization system and method for use in a packet switched communication network are provided. The synchronization system comprises a transmitter-identification system, a packet-boundary detection system and a storage-access system. The transmitter-identification system enables each receiving terminal within the network to know the identity of the originating transmitter terminal for a given packet of information, prior to the reception of this packet of information. The packet-boundary detection system enables detection of packet synchronization parameters for all transmitter-receiver pairs of terminals within the network. The storage-access system stores the detected packet synchronization parameters and allows the receiver to access the packet synchronization parameters. According to one embodiment of the invention, the synchronization method comprises the step of detecting synchronization parameters and, for a given receiver terminal, establishing the identity of the originating transmitter for an incoming packet of information, accessing synchronization parameters corresponding to the identified transmitter, adjusting receiver based on accessed synchronization parameters and decoding the incoming packet of information.

Claims

1. Within a packet switched communication network comprising a plurality of terminals for sending and receiving packets of information, a synchronization system comprising:

a transmitter-identification system for communicating to each receiving terminal within the network the identity of the originating transmitter terminal for a given packet of information, said communication of the transmitter identity occurring prior to the reception of the given packet of information;

a packet-boundary detection system for enabling detection of packet synchronization parameters for all transmitter-receiver pairs of terminals within the network; and

a storage-access system for storage of detected packet synchronization parameters and for allowing access by the receiver within the corresponding transmitter-receiver pair to access said packet synchronization parameters.

2. The synchronization system as in claim 1, wherein said packets of information are based on Orthogonal Frequency Division Multiplexing (OFDM ) modulation technique.

3. The synchronization system as in claim 1, wherein the transmitter identification system comprises a Bus Controller periodically transmitting a bus control message on the bus.

4. The synchronization system as in claim 1, wherein the transmitter identification system comprises a transmission scheduler for sharing a transmission schedule among all terminals.

5. The synchronization system as in claim 1, wherein the transmitter identification system comprises a priority signaler for enabling each terminal to assert priority during a priority signaling interval and for enabling each terminal to acknowledge priority signaling intervals for other terminals.

6. The synchronization system as in claim 1, wherein the packet boundary detection system comprises a synch symbol alignment subsystem, for detecting synch symbol boundaries with respect to a given receiver'"'"'s reference timing system.

7. The synchronization system as in claim 1, wherein the packet boundary detection system comprises a module for performing synch symbol alignment at a receiver based on a single packet.

8. The synchronization system as in claim 1, wherein the packet switched network comprises a Bus Control (BC) terminal sending a bus control message to a plurality of Remote Terminals (RT'"'"'s).

9. The synchronization system as in claim 8, and wherein BC packets and RT packets are different only with respect to sync symbols within the packet preamble.

10. The synchronization system as in claim 1, wherein the packet boundary detection system comprises a correlation receiver.

11. The synchronization system as in claim 1, wherein the packet boundary detection system comprises a block based receiver for performing correlation over predetermined number of samples.

12. The synchronization system as in claim 11, wherein the packet boundary detection declares sync symbol alignment when p out of N-1 sync symbols are detected via the block based receiver, where k smaller than or equal to N-1, and N is the number of sync symbols within preamble.

13. The synchronization system as in claim 1, wherein each packet has a preamble having a plurality of periodic synch symbols.

14. The synchronization system as in claim 1, wherein each packet has a preamble having a plurality of phase continuous synch symbols.

15. The synchronization system as in claim 1, wherein synchronization parameters include relative timing offsets of packet boundaries with respect to internal reference timing systems of receiving terminals.

16. The synchronization system as in claim 1, wherein synchronization parameters are updated.

17. The synchronization system as in claim 15, wherein synchronization parameters are integrated over time.

18. The synchronization system as in claim 1, wherein synchronization parameters include global synchronization parameters and local synchronization parameters.

19. The synchronization system as in claim 18, wherein global synchronization parameters include the average time delay on the network.

20. The synchronization system as in claim 1, wherein synchronization parameters take into account bus dual-redundancy within the network.

21. A method of packet synchronization at a given receiver terminal within a packet-switched communication network comprising a plurality of terminals, the method comprising the steps of:

establishing the identity of the originating transmitter for an incoming packet of information;

if synchronization parameters corresponding to the identified transmitter are available, accessing said synchronization parameters, adjusting receiver based on synchronization parameters and decoding incoming packet of information;

if synchronization parameters corresponding to the identified transmitter are not available, detecting packet synchronization parameters associated with identified transmitter and storing the detected synchronization parameters.

22. A method of packet synchronization within a packet-switched communication network comprising a plurality of terminals, the method comprising the steps of:

detecting synchronization parameters associated with all transmitter-receiver terminal pairs within the network and storing the detected synchronization parameters; and

for a given receiver terminal,

establishing the identity of the originating transmitter for an incoming packet of information;

accessing synchronization parameters corresponding to the identified transmitter;

adjusting receiver based on accessed synchronization parameters; and

decoding incoming packet of information.