Method to enable simultaneous connections to multiple wireless networks using a single radio

• US 20040218580A1
• Filed: 05/02/2003
• Published: 11/04/2004
• Est. Priority Date: 05/02/2003
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Bahl, Paramvir, Chandra, Ranveer, Bahl, Pradeep
• Granted Patent: US 7,720,045 B2
• Time in Patent Office: Days
• US Class Current: 370/350
• CPC Class Codes: H04J 3/0641 Change of the master or reference, e.g. take-over or failure of the master
• CPC Class Codes: H04J 3/0658 Clock or time synchronisation among packet nodes
• CPC Class Codes: H04W 48/18 Selecting a network or a communication service
• CPC Class Codes: H04W 8/22 Processing or transfer of terminal data, e.g. status or physical capabilities
• CPC Class Codes: H04W 8/245 from a network towards a terminal
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

A system and method that allows a user to concurrently connect to multiple wireless networks with a single network interface card is presented. The networks may be infrastructure (“IS”) networks and ad hoc (“AH”) networks. A driver is inserted into a device'"'"'s networking stack and exposes a plurality of virtual wireless network adapters, one for each network. The adapters are enabled and disabled in accordance with which network is presently activated. Packets for a network are queued when the network is not enabled. The wireless driver controls the switching of the network card. In one embodiment where multiple wireless cards are switching in and out of AH networks, the method converges the switching times for the cards in an AH network to ensure concurrent connectivity in the AH network for at least a brief time period every switching cycle of the wireless cards.

Claims

1. A method to synchronize a wireless node having a single wireless card participating in a plurality of networks to at least one other wireless node in at least one ad hoc network in the plurality of networks comprising the steps of:

determining a leader in the at least one ad hoc network;

synchronizing the wireless node with the leader.

2. The method of claim 1 wherein the step of determining the leader comprises the steps of:

remaining on the at least one ad hoc network for at least two switching cycles;

if an announcement from an other node is received;

determining if a MAC address of the other node indicates the other node is a leader;

designating the other node as a leader if the MAC address of the other node indicates the other node is a leader.

3. The method of claim 2 wherein the step of designating the other node as a leader if the MAC address of the other node indicates the other node is a leader comprises the step of designating the other node as a leader if the MAC address of the other node is greater than the MAC address of the wireless node.

4. The method of claim 3 wherein each announcement has a MAC address, the method further comprising the steps of:

storing the MAC address of the other node if the MAC address of the other node is greater than the MAC address of the wireless node, resulting in a stored MAC address;

for each announcement received;

comparing the MAC address in the announcement to the stored MAC address

if the MAC address in the announcement is greater than the stored MAC address, designating a node sending the announcement as the leader; and

resynchronizing the wireless node with the leader.

5. The method of claim 2 wherein the step of designating the other node as a leader if the MAC address of the other node indicates the other node is a leader comprises the step of designating the other node as a leader if the MAC address of the other node is less than the MAC address of the wireless node.

6. The method of claim 5 wherein each announcement has a MAC address, the method further comprising the steps of:

storing the MAC address of the other node if the MAC address of the other node is less than the MAC address of the wireless node, resulting in a stored MAC address;

for each announcement received;

comparing the MAC address in the announcement to the stored MAC address

if the MAC address in the announcement is less than the stored MAC address, designating a node sending the announcement as the leader; and

resynchronizing the wireless node with the leader.

7. The method of claim 2 wherein the step of designating the other node as a leader if the MAC address of the other node indicates the other node is a leader comprises the step of designating the other node as a leader if the other node'"'"'s time since last boot is one of greater than the time since last boot of the wireless node and smaller than the time since last boot of the wireless node.

8. The method of claim 2 further comprising the step of announcing an activity period and an elapsed time if an announcement from the other node is received and a MAC address of the other node indicates the other node is not a leader.

9. The method of claim 8 wherein the step of announcing the activity period and the elapsed time if an announcement from the other node is received and the MAC address of the other node indicates the other node is not a leader comprises the step of announcing the activity period and the elapsed time if the MAC address of the other node is less than the MAC address of the wireless node.

10. The method of claim 8 wherein the step of announcing the activity period and the elapsed time if an announcement from the other node is received and the MAC address of the other node indicates the other node is not a leader comprises the step of announcing the activity period and the elapsed time if the MAC address of the other node is greater than the MAC address of the wireless node.

11. The method of claim 1 wherein each wireless node has an activity time period, an elapsed time inside an activity time period and a switching cycle and wherein the step of synchronizing the wireless node with the leader comprises the steps of:

changing the wireless node'"'"'s activity period to the leader'"'"'s activity period; and

changing the wireless node'"'"'s elapsed time to the leader'"'"'s elapsed time.

12. The method of claim 1 further comprising the step of resynchronizing to a new leader if the wireless node has not received an announcement from the leader for at least two switching cycles.

13. The method of claim 12 further comprising the step of determining the new leader.

14. The method of claim 1 wherein each wireless node has an activity time period, an elapsed time inside an activity time period and a switching cycle the method further comprising the steps of:

determining which node of the wireless nodes in each of the ad hoc networks in the plurality of networks is a network leader, each network leader having an activity time period and an elapsed time in the ad hoc network in which the node is a network leader;

synchronizing the activity period and elapsed time of the wireless node with the activity period and elapsed time of each network leader for the ad hoc network that the network leader is a network leader.

15. The method of claim 14 further comprising the step of resynchronizing to a new network leader in a particular ad hoc network if the wireless node had not received an announcement from the network leader in the particular ad hoc network.

16. The method of claim 1 further comprising the step of switching between the plurality of networks using a switching strategy.

17. The method of claim 16 wherein the step of switching between the plurality of networks comprises switching between the networks in accordance with an allocated activity period for each network.

18. The method of claim 16 wherein the step of switching between the plurality of networks comprises switching between the networks based on an amount of traffic seen in each of the networks over a period of time.

19. The method of claim 16 wherein the step of switching between the plurality of networks comprises switching between the networks based on a number of packets buffered by the wireless node.

20. The method of claim 16 wherein at least one of the plurality of networks requires an authentication protocol be used, the method further comprising the step of storing authentication state for subsequent connections to the at least one of the plurality of networks to reduce the number of authentications from being performed.

21. The method of claim 16 further comprising the step of trapping media disconnect and media connect messages when switching between the plurality of networks.

22. The method of claim 16 further comprising the step of maintaining state of other wireless nodes in each ad hoc network in the plurality of networks.

23. The method of claim 22 wherein the state is maintained in a state table, the method further comprising the steps of:

checking the state table when a packet is to be sent to a destination node to determine if the destination node is currently associated with the current network in which the wireless node is associated;

sending the packet to the destination node if the destination node is currently associated with the current network; and

buffering the packet if the destination node is currently associated with another network.

24. The method of claim 23 further comprising the step of sending buffered packets destined for the destination node on the current network after the state table indicates that the destination node is on the current network.

25. The method of claim 22 wherein the step of maintaining state of other wireless nodes in each ad hoc network in the plurality of networks comprises maintaining state for directly reachable wireless nodes in each ad hoc network.

26. A computer-readable medium having computer-executable instructions for performing steps to synchronize a wireless node having a single wireless card in a plurality of networks having a plurality of wireless nodes, each of the plurality of wireless nodes having an activity time period, an elapsed time inside an activity time period and a switching cycle, the steps comprising:

determining which node of the plurality of wireless nodes in at least one ad hoc network in the plurality of networks is a network leader, each network leader having an activity time period and an elapsed time in the at least one ad hoc network in which the node is a network leader;

synchronizing the activity period and elapsed time of the wireless node with the activity period and elapsed time of each network leader for the at least one ad hoc network.

27. The computer readable medium of claim 26 having further computer executable instructions for performing the step comprising one of resynchronizing the wireless node to a new leader and becoming a new leader if the wireless node has not received an announcement from the leader for at least two switching cycles.

28. The computer readable medium of claim 26 further comprising the step of switching between the plurality of networks using a switching strategy.

29. The computer readable medium of claim 28 wherein the step of switching between the plurality of networks comprises one of switching between the networks in accordance with an allocated activity period for each network, switching between the networks based on an amount of traffic seen in each of the networks over a period of time, and switching between the networks based on a number of packets buffered by the wireless node.

30. The computer readable medium of claim 28 wherein at least one of the plurality of networks requires an authentication protocol be used, the method further comprising the step of storing authentication state for subsequent connections to the at least one of the plurality of networks to reduce the number of authentications from being performed.

31. The computer readable medium of claim 28 further comprising the step of trapping media disconnect and media connect messages when switching between the plurality of networks.

32. The computer readable medium of claim 28 further comprising the step of maintaining state of other wireless nodes in each ad hoc network in the plurality of networks.

33. The computer readable medium of claim 32 wherein the state is maintained in a state table, the computer readable medium having further computer executable instructions for performing the steps comprising:

checking the state table when a packet is to be sent to a destination node to determine if the destination node is currently associated with the current network in which the wireless node is associated;

sending the packet to the destination node if the destination node is currently associated with the current network; and

buffering the packet if the destination node is currently associated with another network.

34. The computer readable medium of claim 33 further comprising the step of sending buffered packets destined for the destination node on the current network after the state table indicates that the destination node has switched to the current network.

35. The computer readable medium of claim 32 wherein the step of maintaining state of other wireless nodes in each ad hoc network in the plurality of networks comprises maintaining state for directly reachable wireless nodes in each ad hoc network.

36. The computer readable medium of claim 26 wherein the at least one ad hoc network comprises a plurality of ad hoc networks and the step of synchronizing the activity period and elapsed time of the wireless node with the activity period and elapsed time of each network leader includes the steps of:

determining if there is an overlap of activity periods of at least two network leaders in the plurality of ad hoc networks;

if the at least two network leaders have overlapping activity periods;

synchronizing the activity period of the wireless node with one of the at least two network leaders based on a priority of the wireless node; and

remaining on the network where the other of the at least two network leaders is a network leader for a part of a duration of the activity period of the other of the at least two network leaders.

37. The computer readable medium of claim 36 having further computer executable instructions for performing the step comprising not sending any announcement messages in the network where the other of the at least two network leaders is a network leader.

38. A method for a wireless node to switch between a plurality of networks using a single wireless card comprising the steps of:

switching between the plurality of networks in accordance with a switching strategy;

if the plurality of networks has at least one ad hoc network;

determining a network leader in the at least one ad hoc network;

adjusting the switching strategy based on an activity time period and an elapsed time period of the network leader of the at least one ad hoc network.

39. The method of claim 38 wherein the step of switching between the plurality of networks comprises switching between the networks in accordance with an allocated activity period for each network.

40. The method of claim 39 wherein the allocated activity period for each network is allocated by a user.

41. The method of claim 38 wherein the step of switching between the plurality of networks comprises switching between the networks based on an amount of traffic seen in each of the plurality of networks over a period of time.

42. The method of claim 38 wherein the step of switching between the plurality of networks comprises switching between the networks based on a number of packets buffered by the wireless node.

43. The method of claim 38 wherein the step of switching between the plurality of networks in accordance with a switching strategy includes the step of broadcasting a message before the wireless node switches between one of the plurality of networks to an other of the plurality of networks, the message indicating the wireless node is switching from the one of the plurality of networks.

44. The method of claim 43 further comprising the step of buffering packets for the other wireless node if a broadcast message is received from the other wireless node indicating that the other wireless node is leaving the network in which the wireless node is active.

45. The method of claim 38 further comprising the step of trapping at least one of media disconnect messages and media connect messages when switching between the plurality of networks.

46. The method of claim 38 further comprising the step of selecting a default gateway in one of the plurality of networks to send a message if a destination of the message is not on any of the plurality of networks.

47. The method of claim 46 further comprising the step setting a flag to indicate when the one of the plurality of networks with the default gateway is active.