Reliable Synchronization Apparatus And Method Within A Multicast And Broadcast Service Zone

• US 20110116434A1
• Filed: 03/05/2010
• Published: 05/19/2011
• Est. Priority Date: 11/13/2009
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Yang, Jen-Shun, Wang, Jui-Tang, Kuo, Wei-Han, Liu, Chia-Lung
• Granted Patent: US 8,391,198 B2
• Time in Patent Office: Days
• US Class Current: 370/312
• CPC Class Codes: H04L 12/1868 Measures taken after transmission, e.g. acknowledgments
• CPC Class Codes: H04L 12/1881 with schedule organisation, e.g. priority, sequence management
• CPC Class Codes: H04L 12/189 in combination with wireless systems selective distribution or broadcast in wireless communication networks H04W4/06
• CPC Class Codes: H04W 4/06 Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others

Abstract

A reliable synchronization apparatus and method within a multicast and broadcast service (MBS) zone having m sync executers (SEs) belonging to n retransmission zones is provided. Each retransmission zone has a selected leader SE and other member SEs. The apparatus comprises a sync controller and the n selected leader SEs. When the Sync controller multicasts a sync ruler to all SEs in a retransmission zone, the leader SE that loses the Sync ruler sends a NACK message to request the sync controller to retransmit the sync ruler. An election is triggered for updating leader information and announcing election to all SEs. The member SE that loses the sync ruler sends a NACK message to request its leader or the Sync controller to retransmit the sync ruler.

Claims

1. A reliable synchronization apparatus within a multicast and broadcast service (MBS) zone, said MBS zone having m sync executers (SEs) and said m SEs belonging to n retransmission zones respectively, m>

n≧

1, each retransmission zone having a selected leader SE and un-selected SEs being member SEs of said leader SE, said apparatus comprising;

said n selected leader SEs; and

a sync controller, in each said retransmission zone, when multicasting a sync ruler to all SEs in said retransmission zone, leader SE not having received said sync ruler unicasting a NACK message to said sync controller to request retransmitting said sync ruler;

said sync controller retransmitting said sync ruler and triggering an election to update leader SE information and multicasting said information to all SEs in said retransmission zone, each member SE not having received said sync ruler unicasting a NACK message to its leader SE or said sync controller to request retransmitting said sync ruler.

2. The apparatus as claimed in claim 1, wherein for each said retransmission zone of said n retransmission zones, said sync controller further includes a leader priority list to record priority information of selecting said leader SE in said retransmission zone.

3. The apparatus as claimed in claim 1, wherein said sync controller multicasts through a core network a sync ruler in every other recover period of sync ruler to all SEs of each said retransmission zone.

4. The apparatus as claimed in claim 3, wherein said core network is a wireless network.

5. The apparatus as claimed in claim 1, wherein after said election generates an election result, said sync controller multicasts said election result to all SEs of said retransmission zone and updates leader SE information.

6. The apparatus as claimed in claim 3, wherein said sync controller keeps said sync ruler during said recovery period of said sync ruler.

7. The apparatus as claimed in claim 1, wherein said member SE further includes a timer and sets said timer when receiving an election message multicast by said sync controller, and when said timer expires, said member SE unicasts current leader SE information to said sync controller.

8. The apparatus as claimed in claim 1, wherein if each of said member SE not having received said sync ruler has not received said sync ruler after said recovery period of said sync ruler expires, the member SE requests said leader SE to retransmit said sync ruler.

9. The apparatus as claimed in claim 1, wherein if each of said member SE not having received said sync ruler has not received said sync ruler after said recovery period of said sync ruler expires and before a MAX_REQUEST_DELAY_BOUND expires, the member SE requests said leader SE to retransmit said sync ruler.

10. The apparatus as claimed in claim 1, wherein said sync controller generates an election result containing current leader SE information according to an election algorithm.

11. A reliable synchronization method within a multicast and broadcast service (MBS) zone, said MBS zone having m sync executers (SEs) and said m SEs belonging to n retransmission zones respectively, m>

n≧

1, said method comprising;

pre-selecting a leader SE in each retransmission zone of said n retransmission zones and un-selected SEs being corresponding member SEs of said leader SE;

through a sync controller, multicasting a sync ruler to all SEs of a retransmission zone of said n retransmission zones;

leader SE not having received said sync ruler unicasting a NACK message to said sync controller to request retransmitting said sync ruler;

said sync controller retransmitting said sync ruler and triggering an election to update leader SE information and multicasting said information to all SEs; and

each of said member SE not having received said sync ruler unicasting a NACK message to its leader SE or said sync controller to request retransmitting said sync ruler.

12. The method as claimed in claim 11, wherein said sync controller generates an election result containing current leader SE information according to one of either distributed or centralized election algorithm.

13. The method as claimed in claim 11, wherein if said leader SE of said retransmission zone having successfully received said sync ruler multicast by said sync controller, said leader SE further executes:

checking whether having received a retransmission request from a member SE in said recovery period of said sync ruler; and

if so, transmitting said sync ruler to said member SE;

repeating said operation until no further retransmission request having been received in said recovery period of said sync ruler.

14. The method as claimed in claim 11, wherein if a member SE of said retransmission zone having successfully received said sync ruler multicast by said sync controller, said member SE further executes:

checking whether having received a retransmission request from other member SEs having lost said sync ruler in said recovery period of said sync ruler; and

if so, said member SE transmitting said sync ruler and current leader SE information to said member SE requesting retransmission; and

updating the leader SE information.

15. The method as claimed in claim 14, wherein if no retransmission request from other member SEs having lost said sync ruler is received, and if the leader SE of said retransmission zone is crashed or overloaded, said member SE receives message of electing new leader SE and an election result, and then updates the leader SE information.

16. The method as claimed in claim 11, wherein among all of said member SEs not having received said sync ruler, if a member SE has received said sync ruler after said recovery period of said sync ruler expires and before a MAX_REQUEST_DELAY_BOUND expires, said member SE further executes:

requesting its leader SE retransmitting said sync ruler after said recovery period of said sync ruler expiring;

before said MAX_REQUEST_DELAY_BOUND expiring, receiving said sync ruler; and

checking whether having received current leader SE information from a same SE, if so, updating leader SE information.

17. The method as claimed in claim 11, wherein among all of said member SEs not having received said sync ruler, if a member SE has received said sync ruler after a MAX_REQUEST_DELAY_BOUND expires, said member SE further executes:

requesting its leader SE retransmitting said sync ruler;

before said MAX_REQUEST_DELAY_BOUND expiring, not having received sync ruler; and

requesting said sync controller retransmitting sync ruler, and said member SE successfully received said sync ruler.

18. The method as claimed in claim 11, wherein among all of said member SEs not having received said sync ruler, if a NACK message from a member SE is received, said member SE further executes:

checking whether to repeat obtaining said sync ruler; and

if so, returning said sync ruler and current leader SE information;

otherwise, returning current leader SE information.

19. The method as claimed in claim 11, wherein among all of said member SEs not having received said sync ruler, if a said member SE has received current leader SE information before a MAX_REQUEST_DELAY_BOUND expires, said member SE further executes:

checking whether to repeat obtaining said sync ruler; and

if not having received said sync ruler, updating current leader SE information and requesting a new leader SE to retransmit sync ruler;

otherwise, updating current leader SE information.

20. The method as claimed in claim 11, wherein among all of said member SEs not having received said sync ruler, if a member SE has received current leader SE information after a MAX_REQUEST_DELAY_BOUND expires, said member SE updates current leader SE information.

21. The method as claimed in claim 11, wherein among all of said member SEs not having received said sync ruler, if a said member SE has received a message for electing new leader SE during recovery period of said sync ruler, said member SE ignores said election message.

22. The method as claimed in claim 11, wherein in the condition of said leader SE successfully received said sync ruler, each member SE not having received said sync ruler requests to said leader SE for retransmitting said sync ruler, and said leader SE retransmits said sync ruler to said member SE requesting retransmission.

23. The method as claimed in claim 11, wherein in the condition of said leader SE having lost said sync ruler, said leader SE loses leadership and unicasts said NACK message to said sync controller, and then said election is triggered and said sync controller generates and announces new leader SE information according to an election algorithm.

24. The method as claimed in claim 11, wherein in the condition of said leader SE having lost said sync ruler and in crashed state, if a said member SE has not received said sync ruler before a MAX_REQUEST_DELAY_BOUND expires, said member SE requests said sync controller for retransmitting said sync ruler, and further executes:

said sync controller retransmitting said sync ruler to said member SE; and

performing an election process, after said election process, said sync controller announcing new leader SE information.

25. The method as claimed in claim 12, wherein when said sync ruler uses said distributed election algorithm, each member SE in said retransmission zone has a fair opportunity to become leader SE of said retransmission zone.

26. The method as claimed in claim 12, wherein when said sync ruler uses said centralized election algorithm, a leader priority list is used in generating a new leader SE.