LOW-POWER WIRELESS MULTI-HOP NETWORKS

• US 20100097969A1
• Filed: 12/13/2007
• Published: 04/22/2010
• Est. Priority Date: 12/15/2006
• Status: Active Grant

• Current Assignee: GreenPeak Technologies BV (Qorvo, Inc.)
• Original Assignee: GreenPeak Technologies BV (Qorvo, Inc.)
• Inventors: Van Den Bosch, Bram, Noel, Stephan, De Kimpe, Wim
• Granted Patent: US 8,514,758 B2
• Time in Patent Office: Days
• US Class Current: 370/311
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 68/025 Indirect paging
• CPC Class Codes: H04W 76/28 Discontinuous transmission [DTX]; Discontinuous reception [DRX]
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method of communication or transmission of data between a first and a second node in a wireless multi-hop network comprises bringing the first node and the second node in a fully operative mode for communication with each other and subsequently bringing the first node and the second node in a reduced operative mode where no communication with any other node is possible and, before bringing the second node in the fully operative mode, bringing the second node in a listening mode during a token listening period to check for presence of a wake-up token from the first node, and thereafter bringing the second node into the reduced operative mode if no wake-up token is received, and bringing the second node into the fully operative mode for reception of data from the first node if a wake-up token is received. This wake-up scheme is a kind of scheduled rendezvous scheme with collision avoidance, and may be called an induced wake-up scheme. It is advantageous because of its low power consumption (no des only wake up completely when a message is present for them to receive) and because of the low latency in data transfer. The wake-up tokens used enable random access to other nodes, nevertheless having a system which is low-power in operation.

Claims

1-27. -27. (canceled)

28. A method of communication between a first (A), a second (B) and a third node (C) in a wireless multi-hop network (A, B, C), the method comprising

bringing the first node (A) and the second node (B) respectively the third node (C) in a fully operative mode (53) for communication with each other and subsequently bringing the first node (A) and the second node (B) respectively the third node (C) in a reduced operative mode (55) where no communication with any other node is possible,

wherein the method furthermore comprises:

before bringing the respective node (A, B, C) in the fully operative mode (53),

bringing the respective node (B) in a listening mode (50) during a token listening period to check for presence of a wake-up token (51),

bringing the respective node (A, B, C) into the reduced operative mode (55) if no wake-up token is received, and bringing the respective node (A, B, C) into the fully operative mode (53) for reception of data if a wake-up token is received, and

wherein the method furthermore comprises synchronising the timing of the listening mode of the respective node (A, B, C) with the timing of the transmitting of the wake-up tokens by another node, wherein synchronising includes one node transmitting a beacon signal and another node synchronising with the beacon signal,

wherein the number of wake-up tokens, sent by the respective node (A, B, C) during each time the respective other node (A, B, C) is in said listening mode (53), is not more than a single wake-up token,

wherein collisions of the wake-up tokens are reduced by using a collision avoidance scheme according to which

the third node (C) intending to send a wake-up token to the second node (B), having received a wake-up token sent from the first node (A) to the second node (B) cancels the wake-up token to the second node (B), and

respectively scheduling a first (S1), second (S2) and third time slot (S6) selected among different time slots in a beacon period between two subsequent beacon signals,

respectively allocating the token listening period of the second node (B) to the first time slot (S1), the token listening period of the third node (C) to the second time slot (S2) and the token listening period of the first node (A) to the third time slot (S6),

29. The method according to claim 28, wherein an additional time slot is allocated behind the selected time slot.

30. The method according to claim 28, wherein all nodes in the network synchronise with the beacon signal.

31. The method according to claim 28, wherein the wake-up token is an electromagnetic wave data packet with a length of between 200 μ

s and 5 ms.

32. The method in accordance with claim 28, furthermore comprising transmitting a wireless communication data packet from the first node to the second node.

33. The method in accordance with claim 32, furthermore comprising the second node acknowledging receipt of the wireless communication data packet to the first node.

47. A computer program product enabling a processor to carry out a method as described in claim 28.

48. A machine readable data storage device storing the computer program product of claim 47.

34. A wireless data communication system comprising

a plurality of nodes (A, B, C) organised into a multi-hop network of connection paths between said nodes,

wherein the nodes are adapted for having a reduced operative mode (55) in which said node is inoperative to transmit or receive wireless communications, and an fully operative mode (53) during which said node is operative to transmit or receive wireless communications to or from a neighbouring node within reception range,

a node (A, B, C) furthermore being adapted for, before going into the fully operative mode, going in a listening mode (50) during which it listens for tokens sent by a neighbouring node within reception range, the node being adapted for deciding, depending on the outcome of the listening mode, to go into the fully operative mode (53) after reception of a wake-up token (51) from the neighbouring node, or to go into the reduced operative mode (55) if no such wake-up token is received,

wherein the system furthermore comprises an internal time reference in form of a beacon that is periodically sent for synchronising operation of the nodes (A, B, C),

wherein the number of wake-up tokens, sent by the first node during each time the first node is in said fully operative mode, is not more than a single wake-up token, and

wherein collisions of the wake-up tokens are reduced by using a collision avoidance scheme according to which

a third node (C) intending to send a wake-up token to a second node (B), having received a wake-up token sent from a first node (A) to the second node (B) is configured to cancel the wake-up token to the second node (B), and

to respectively schedule a first (S1), second (S2) and third time slot (S6) selected among different time slots between two subsequent beacon signals, and

to respectively allocate a period for listening to tokens of the second node (B) to the first time slot (S1), a period for listening to tokens of the third node (C) to the second time slot (S2) and a period for listening to tokens of the first node (A) to the third time slot (S6).

35. The wireless data communication system according to claim 34, wherein a node comprises

a receiver for receiving wireless communications data packets from a neighbouring node,

a transmitter for transmitting wireless communication data packets to a neighbouring node, and

a processor, said processor being programmed to bring the node in the listening mode (50) at pre-determined time intervals to listen for tokens (51) sent by a neighbouring node within reception range, and if such token (51) is received, to bring the node into its fully operative mode (53), and if not, to bring the node into its reduced operative mode (55).

36. The wireless data communication system according to claim 35, furthermore comprising a counter for timing the duration of the listening mode.

37. The wireless data communication system according to claim 36, wherein the counter is hardware implemented.

38. The wireless data communication system according to claim 36, wherein the counter is implemented in software.

39. The wireless data communication system according to claim 34, wherein a node is adapted for transmitting, during its fully operative mode, a wireless communication data packet to a neighbouring node which is also brought in its fully operative mode.

40. The wireless data communication system according to claim 39, wherein the neighbouring node is adapted for, after having received the wireless communication data packet, transmitting an acknowledgement message to the node.

41. The wireless data communication system according to claim 34, wherein the internal time reference includes a beaconing system.

42. The wireless data communication system according to claim 34, including a node comprising a time slot allocation unit for allocating a time slot for sending data packets.

43. The wireless data communication system according to claim 34, wherein a node is adapted to perform clear channel assessment before transmission of a wireless communication data packet.

44. The wireless data communication system according to claim 34 wherein a node is a sensor.

45. A controller for controlling operation of a node (A, B, C) in a wireless multi-hop network, the controller comprising

first mode switching means for bringing the node in a listening mode (50) during a token listening period to check for presence of a wake-up token (51) transmitted by another node,

second mode switching means for bringing the node in a fully operative mode (53) for communication with another node if a wireless communication data packet is to be sent to another node or if a wake-up token (51) is received from another node, and

third mode switching means for bringing the node in a reduced operative mode (55) where no communication with any other node is possible if no wireless communication data packet is to be sent to another node and if no such wake-up token is received,

wherein the controller further comprises an internal time reference in the form of a beacon receiver/transmitter for synchronising operation of the nodes, the number of wake-up tokens, transmitted by the other node during each time the first node is in said fully operative mode, comprises not more than a single wake-up token,

wherein the first mode switching means is adapted to bring the node in the listening mode (50) during a first time slot (S1) selected among different time slots between two subsequent beacon signals, and

wherein the controller is adapted to reduce collisions of the wake-up tokens by using a collision avoidance scheme according to which it is adapted to bring the node (C) intending to send a wake-up token to a second node (B), having received a wake-up token sent from a first node (A) to the second node (B) to cancel the wake-up token to the second node (B).

46. The controller in accordance with claim 45, wherein the controller is an embedded controller.