Methods and apparatus for downlink macro-diversity in cellular networks

• US 20040141502A1
• Filed: 11/05/2003
• Published: 07/22/2004
• Est. Priority Date: 05/06/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Park, Vincent, Corson, M. Scott, Laroia, Rajiv, Kapoor, Samir
• Granted Patent: US 7,623,477 B2
• Time in Patent Office: Days
• US Class Current: 370/389
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 36/00692 using simultaneous multiple data streams, e.g. cooperative multipoint [CoMP], carrier aggregation [CA] or multiple input multiple output [MIMO] allocation of physical resources in CoMP or in CA H04L5/0035
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 36/185 using make before break
• CPC Class Codes: H04W 40/02 Communication route or path selection, e.g. power-based or shortest path routing
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

The invention described herein enables a form of downlink macro-diversity in packet-switched cellular networks. It allows packets to be selectively delivered from a network/internetwork to an end node, e.g., a wireless communication device or terminal, over a set of available link-layer connections to/from the end node, through one or more access nodes, e.g., base stations. Downlink macro-diversity is particularly important when the link-layer connections between the end node and the corresponding access node, e.g., the access links, are subject to independent or partially correlated time variations in signal strength and interference. In accordance with the invention, the end node dynamically selects the downlink to be used out of a set of available access links on a per packet basis subject to prevailing channel conditions, availability of air-link resources and other constraints. The invention improves the robustness and efficiency of communication, overall utilization of air-link resources, and quality of service experienced by the end node.

Claims

1. A communications method comprising:

operating an end node to maintain multiple communications links, a first one of said communications links being between a first access node and said end node; and

controlling which one of said multiple communications links is used to transmit packets to said end node at any given time.

2. The method of claim 1, wherein said end node controls which one of said multiple communications links is used, the method further comprising:

operating the end node to transmit a signal to said first access node to control said first access node to transmit packets to said end node using said first communications link.

3. The method of claim 2, further comprising:

operating the end node to send a signal to said first access node to prevent the transmission of packets to said end node over the first communications link for at least a portion of time during which packets are being received by said end node via said second communications link.

4. The method of claim 3,

wherein said first and second communications links are both between said first access node and the end node;

and

wherein said first access node transmits packets to said end node using one of said communications links at any given point in time.

5. The method of claim 3, wherein the second communications link is a communications link between a second access node and said end node, the method further comprising:

sending a first stream of packets directed to said end node to the first access node;

sending a duplicate stream of packets to said second access node, the duplicate stream of packets including at least one packet having a payload which is a duplicate of a payload of at least one packet in said first stream; and

operating at least one of said first and second access nodes to discard at least some packets directed to the end node.

6. The method of claim 5, wherein during a first period of time packets from said first stream are transmitted to said end node over said first communications link and during a second period of time packets from the second stream are transmitted to said end node, the first and second periods of time being consecutive periods of time, at least some of the packets transmitted to said end node during said first and second periods of time being non-duplicative.

7. The method of claim 5, further comprising:

operating a network node coupled to said first and second nodes to perform a duplication operation on a series of packets directed to said end node to generate said first and second streams of packets;

routing the first stream of packets to said first access node; and

routing the second stream of packets to said second access node.

8. The method of claim 7, further comprising the step of:

operating the end node to reconstruct a single series of packets from packets received from said first and second communications links, the packets in said single series matching at least a portion of the series of packets duplicated to generate said first and second streams of packets.

9. The method of claim 1, wherein controlling which one of said multiple communications links is used to transmit packets to said end node at any given time is performed as a function of link state quality measurements.

10. The method of claim 9, wherein said end node controls which of said multiple communications links is used to communicate packets to said end node.

11. The method of claim 1, wherein said end node selects which of said multiple communications links is to be used at any point in time for transmission of packets to the end node based on link state quality information.

12. The method of claim 1, wherein said end node controls which one of said multiple communications links is used to transmit packets to said end node at any given time by transmitting at least one control signal to said first access node.

13. The method of claim 12, wherein a second one of said multiple communications links is between said end node and a second access node;

and

wherein said end node sends control signals to at least one access node to control which of said first and second communications links is used to transmit packets to said end node.

14. The method of claim 13, wherein said end node sends packet transmission control signals to at least two access nodes having communications links with said end node.

15. The method of claim 13, further comprising:

operating a network node to duplicate packets directed to said end node to thereby generate first and second packet streams;

communicating the first packet stream to said first access node;

communicating the second packet stream to said second access node; and

operating said first and second access nodes to discard packets transmitted to said end node by the other one of said first and second access nodes.

16. The method of claim 15, wherein the time required to transmit the control signal from the end node to the first access node is less than the time required to transmit packets from said network node which duplicates packets to said first access node.

17. The method of claim 16, wherein the time required to transmit the control signal from the end node to the second access node is less than the time required to transmit packets from said network node which duplicates packets to said second access node.

18. The method of claim 15, wherein the time required to transmit the control signal from the end node to the first access node is less than the time required to transmit packets from said network node which duplicates packets to said end node.

19. The method of claim 18, wherein the time required to transmit the control signal from the end node to the second access node is less than the time required to transmit packets from said network node which duplicates packets to said end node.

20. The method of claim 2, wherein said access node is a base station.

21. The method of claim 2,

wherein said end node is a mobile device;

and

wherein said multiple communications links are wireless communications links.

22. The method of claim 21, wherein said communications links are OFDM communications links.

23. The method of claim 21, wherein said communications links are CDMA communications links.

24. The method of claim 21, wherein said access node is a base station.

25. The method of claim 7,

wherein said network node is a router;

wherein said access node is a base station; and

wherein said end node is a portable notebook computer.

26. A communications system, comprising:

an end node, said end node including;

means for maintaining multiple communications links, a first one of said communications links being between a first access node and said end node; and

means for controlling which one of said multiple communications links is used to transmit packets to said end node at any given time.

27. The communication system of claim 26, further comprising:

said first access node; and

a second access node, said first and second access nodes being coupled to said end node by first and second communications links, respectively, said second access node including means for discarding packets directed to said end node in response to a control signal from said end node indicating that packets are not to be transmitted to said end node.

28. The communications system of claim 27, wherein said first access node includes means for discarding packets directed to said end node in response to a control signal from said end node indicating that packets are not to be transmitted to said end node.

29. The communications system of claim 28, further comprising:

a network node coupled to said first and second access nodes, the network node including;

means for performing a duplication operation on a series of packets directed to said end node to generate first and second streams of packets, the second stream of packets including packets having payloads which are duplicates of the payloads of at least some packets in the first stream.

30. The communications system of claim 29,

wherein said first access node is a first base station;

wherein said second access node is a second base station;

wherein said multiple communications links are wireless communications links; and

wherein said end node is a mobile device.

31. The communications system of claim 30, wherein said network node is a router.

32. A communications method comprising:

maintaining a plurality of communications connections, said plurality of communications connections including a first connection between a first transmitter and an end node and a second connection between a second transmitter and said end node, said communications connections being for transmitting portions of packets to said end node from a stream of packets directed to said end node;

receiving information from said end node;

determining as a function of the received information which one of said plurality of communications connections should be used for purposes of transmitting at least a portion of a packet in said stream of packets to said end node;

transmitting at least a portion of a packet using the determined communications connection; and

repeating said receiving, determining and transmitting steps.

33. The communications method of claim 32, wherein said portion of a packet is a frame.

34. The communications method of claim 33, wherein said portion of a packet is a frame which includes the content of a complete packet.

35. The communications method of claim 32,

wherein said communications connections are wireless;

and

wherein each transmitted portion of a packet in said stream of packets is directed over a single one of said communications connections to said end node.

36. The method of claim 32, wherein said communications connections are physical layer connections.

37. The method of claim 32, wherein said communications connections are link layer connections.

38. The method of claim 32, wherein portions of packets transmitted over said first communications connection are transmitted using a first communications protocol and wherein portions of packets transmitted over said second communications connection are transmitted using a second communications protocol which is different from said first communications protocol.

39. The method of claim 32, wherein each portion of a packet is included in a frame, said selecting step being performed to correspond to frame boundaries.

40. The method of claim 39, wherein each of said first and second transmitters are located in the same access node, each of the first and second transmitters corresponding to a different sector.

41. The method of claim 32, wherein said selecting step is performed to correspond to packet boundaries.

42. The method of claim 41, wherein said first transmitter is located in the first access node and the second transmitter is located in the second access node, the method further comprising:

operating a node coupled said second access node to duplicate packets in said stream of packets prior to sending the duplicated packets to said second access node; and

operating the second access node to discard duplicated packets which are transmitted to said end node over the first communications connection without transmitting said discarded packets to said end node.

43. The method of claim 42, wherein said node coupled to said second access node is said first access node.

44. The method of claim 42, wherein said node coupled to said second access node is a network node which is also coupled to said first node, the method further comprising:

operating the first access node to discard duplicate packets which are transmitted to said end node by said second access node via the second communications connection without transmitting said discarded packets to said end node.

45. The method of claim 42, wherein said selecting is performed multiple times resulting in a communications connection being used as a downlink to said end node being changed multiple times during a period of time in which the end node uses an uplink which does not change during said period of time to communicate packets to an access node.

46. The communications method of claim 32, wherein said information from said end node is control information indicating which one of said communications connections should be used for transmission purposes.

47. The communications method of claim 32, wherein said information from said end node is channel condition information.