Wireless mesh network with multisized timeslots for TDMA communication

• US 8,005,020 B2
• Filed: 09/28/2007
• Issued: 08/23/2011
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Karschnia, Robert J.
• Primary Examiner(s): Rao; Seema S.
• Assistant Examiner(s): DUONG, CHRISTINE T
• Application Number:
  US11/906,163
• Publication Number:
  US 20080084852A1
• Time in Patent Office: 1,425 Days
• Field of Search: None
• US Class Current: 370/255
• CPC Class Codes: H04B 7/2656 for structure of frame, burst
• CPC Class Codes: H04J 3/1682 Allocation of channels according to the instantaneous demands of the users, e.g. concentrated multiplexers, statistical multiplexers
• CPC Class Codes: H04W 72/51 based on terminal or device properties
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

A wireless mesh network uses communication frames that can include timeslots of different sizes depending on communication speed capabilities of the devices assigned to the timeslots. The communication frame is divided into timeslot increments of equal length. The timeslots are made up of one or more timeslot increments.

Claims

1. A method of operating a wireless mesh network having a plurality of nodes capable of transmitting and receiving messages, the method comprising:

determining a shortest timeslot length to be used by the wireless mesh network based upon minimum time requirements for communication by each node, wherein each timeslot comprises one or more time slot increments each having a time duration t_i;

synchronizing the nodes to a communication cycle having a frame, wherein the frame has a time duration T_f=Nt_i based on a refresh rate of the wireless mesh network, where N is a total number of timeslot increments in the frame, N being a positive integer and each timeslot increment t_i being of equal length, wherein the frame forms timeslots each having lengths Mt_i; and

assigned to the nodes, wherein, for each timeslot individually, M is a positive integer less than N, and wherein a value of M is initially equal for all of the timeslots;

registering a plurality of new nodes with a network manager when the new nodes join the wireless mesh network;

determining a shortest timeslot length of which the new nodes are capable within the wireless mesh network based upon minimum time requirements for communication by each new node to turn on its radio, verify an associated channel is clear, send a message, and listen for an acknowledgement; and

assigning timeslots within each frame for communication between pairs of nodes, wherein lengths of the assigned timeslots vary as a function of the shortest timeslot length for each pair of nodes, such that at least one pair of the new nodes both having lower minimum time requirements than other nodes is assigned a correspondingly shorter timeslot;

wherein the network manager assigns the timeslots.

2. The method of claim 1, wherein the frame includes at least one timeslot of a duration of t_i.

3. The method of claim 1, wherein the frame includes at least one timeslot of a duration of 2t_i.

4. The method of claim 1, wherein the frame includes at least one timeslot of a duration of 4t_i.

5. The method of claim 1, wherein assigning timeslots is based upon stored configuration data for each node.

6. The method of claim 5, wherein the stored configuration data includes a minimum time period required by each node to communicate during a timeslot.

12. The wireless mesh network of claim 1, wherein the network manager uses stored configuration data for the nodes to determine the time durations Mt_i of the timeslots.

7. A wireless mesh network comprising a plurality of nodes capable of transmitting and receiving messages during assigned timeslots within a repeating communication frame, characterized by:

the plurality of nodes comprising a first set of one or more nodes having first minimum communication time capabilities and a second set of one or more nodes having second minimum communication time capabilities that are faster than the first minimum communication time capabilities, the first and second minimum communication time capabilities being times for each associated node to turn on its radio, verify an associated channel is clear, send a message, and listen for an acknowledgement;

the frame comprising N timeslot increments of equal time duration t_i, the time duration t_i selected as a function of both the first and second minimum communication time capabilities, wherein the frame has a total time based on a refresh rate of the wireless mesh network;

each timeslot has a time duration Mt_i, where the time duration Mt_i is a positive integer multiple of the time duration t_i, and wherein the time duration of each timeslot is independently determined based upon a minimum communication time required by each node assigned to that timeslot to communicate, and wherein the minimum communication time is determined by the first or second minimum communication time capabilities of each node; and

a network manager that assigns selected nodes of only the first set to the timeslots and determines the time duration Mt_i of each timeslot, and that reassigns selected nodes of both the first and second sets to the time slots and re-determines the time duration Mt_i of each timeslot.

8. The wireless mesh network of claim 7, wherein the frame includes at least one timeslot having the time duration Mt_i equal to t_i.

9. The wireless mesh network of claim 7, wherein the frame includes at least one timeslot having the time duration Mt_i equal to 2_i.

10. The wireless mesh network of claim 7, wherein the frame includes at least one timeslot having the time duration Mt_i equal to 4t_i.

11. The wireless mesh network of claim 7, wherein the frame includes timeslots of different time durations Mt_i.

13. A wireless mesh network comprising:

a plurality of nodes capable of transmitting and receiving messages, wherein the plurality of nodes comprises a first set of one or more nodes having first minimum communication time capabilities and a second set of one or more nodes having second minimum communication time capabilities faster than the first minimum communication time capabilities, the first and second minimum communication time capabilities being times for each associated node between turning on its radio and listening for an acknowledgement of a sent message; and

a network manager for synchronizing the nodes based upon a communication cycle of repeating frames having total frame times based on a refresh rate of the wireless mesh network, wherein each frame includes timeslots assigned to selected nodes, wherein each frame comprises N timeslot increments of equal time duration t_i, N being a positive integer, and wherein each timeslot has a time duration Mt_i, determined individually, where the time duration Mt_i is a positive integer multiple of the time duration t_i and wherein the network manager assigns timeslots of different time durations depending on the first minimum communication time capabilities of selected nodes of only the first set, and wherein the network manager then reassigns timeslots of different time durations depending on both the first and second minimum communication time capabilities of selected nodes of both the first and second sets, wherein the network manager determines the time duration of each timeslot based upon a minimum time required by the selected nodes to communicate during that timeslot.

14. The wireless mesh network of claim 13, wherein the network manager determines the time duration of each timeslot based upon the minimum time required by the selected nodes to communicate during that timeslot.

15. The wireless mesh network of claim 13, wherein the frame includes at least one timeslot having the time duration Mt_i equal to 2t_i.

16. The wireless mesh network of claim 13, wherein the frame includes at least one timeslot having the time duration Mt_i equal to 4t_i.