Adaptive synchronous protocol for minimizing latency in TDD systems

• US 9,247,512 B2
• Filed: 08/25/2011
• Issued: 01/26/2016
• Est. Priority Date: 08/25/2011
• Status: Active Grant

• Current Assignee: Ubiquiti Inc.
• Original Assignee: Ubiquiti Networks, Inc. (Ubiquiti Inc.)
• Inventors: Schultz, Gary, Odlyzko, Paul
• Primary Examiner(s): Pezzlo, John
• Application Number:
  US13/217,428
• Publication Number:
  US 20130051286A1
• Time in Patent Office: 1,615 Days
• Field of Search: 370/278, 370/282, 370/252, 370/294, 370/442
• US Class Current: 1/1
• CPC Class Codes: H04L 5/1469 using time-sharing
• CPC Class Codes: H04L 5/1476 operating bitwise
• CPC Class Codes: H04L 7/04 Speed or phase control by synchronisation signals H04L7/0075 takes precedence
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others

Abstract

Systems and methods are presented that offer significant improvements in the performance of time division duplex (TDD) systems by utilizing an adaptive synchronous protocol. Conventional TDD systems are limited because data is transmitted during discreet and limited intervals of time, and because TDD transceivers may not simultaneously transmit and receive for reasons of insufficiently separated frequencies and limited receiver selectivity. Typically, TDD systems have significant latency due to the time to change from transmission to reception and the propagation delay time. By synchronizing the master nodes and the one or more remotes and by scheduling the traffic loads between these nodes, remote nodes may begin transmitting before the master node is finished with its transmission, and vice versa. This method reduces latency and improves the frame efficiency. Further, the frame efficiency may improve as the distance from the master node to the remote node increases.

Claims

1. A method comprising:

transmitting from a master node to one or more remote nodes, a synchronization signal, said synchronization signal operable to cause the one or more remote nodes to transmit according to a predetermined timing;

receiving at the master node a response to the synchronization signal, said response providing propagation time information, and

transmitting, from the master node to the remote nodes, schedule information causing at least one of the remote nodes to transmit information to the master node while the master node is transmitting on substantially the same channel.

2. The method as in claim 1 wherein the synchronization signal is based on an external source.

3. The method as in claim 2 wherein a synchronization source is provided by a global time reference.

4. The method of claim 1 further including:

receiving, at the master node, traffic load information from at least one of the remote nodes;

transmitting to the at least one remote nodes, schedule information, said schedule information operable to cause the remote nodes to transmit traffic on a predetermined schedule.

5. The method of claim 4 wherein the traffic loads of the master node and the remote nodes are asymmetrical.

6. The method as in claim 1 wherein the master node transmits a broadcast signal to one or more remote nodes to synchronize the one or more remote nodes.

7. The method of claim 6 wherein the broadcast signal includes either a pre-amble or a pilot message.

8. The method of claim 1 wherein scheduling is implemented with a three message handshake comprising:

communicating from at least one of the one or more remote nodes to the master node, the communicating comprising an indication of a desire to transmit one or more traffic loads;

sending available transmission options from the master node to one of the one or more remote nodes, and

selecting by the one of the one or more remote nodes an option with registration and ranging message information and notifying the master node of the selection.

9. The method of claim 1 wherein the one or more remote nodes refrain from transmitting based on control messages from the master node.

10. The method of claim 1 wherein scheduling occurs on a frame by frame basis.

11. The method of claim 1 further including:

coordinating between a plurality of sector access points wherein a sector access point does not receive a signal while another sector access point in same cluster is transmitting on either the same or a substantially close frequency.

12. The method of claim 1 wherein the one or more remote nodes begin transmitting before the master node is finished with its transmission, and the master node begins transmitting before the one or more remote nodes is finished with its transmission.

13. The method of claim 12 wherein the transmitting is modified to correct for propagation delay and data packet transmission duration.

14. The method of claim 13 wherein degree of temporal overlap of the transmission of the master node and a remote node is proportional to distance between the remote node and the master node.

15. A system comprising:

a master node;

one or more remote nodes;

a time reference; and

a schedule of planned traffic loads from the master node to the one or more remote nodes, and from the one or more remote nodes to the master node, said schedule based at least partially on a propagation time between the master node and at least one of the remote nodes,

wherein the schedule is arranged to minimize transition time for each node by directing them to transmit substantially simultaneous transmissions on substantially the same channel.

16. The system of claim 15 wherein the one or more remote nodes begin transmitting before the master node is finished with its transmission, and the master node begins transmitting before one or more remote nodes is finished with its transmission.

17. The system of claim 16 wherein degree of temporal overlap of the transmission of the master node and a remote node is proportional to distance between the remote node and the master node.

18. Non transitory media having processor readable code embodied on said media, said processor readable code for programming one or more processors to perform a method including:

transmitting from a master node to one or more remote nodes, a synchronization signal, said synchronization signal operable to cause the one or more remote nodes to transmit according to a predetermined timing,;

receiving at the master node a response to the synchronization signal, said response providing propagation time information, and

transmitting, from the master node to the remote nodes, schedule information causing at least one of the remote nodes to transmit information to the master node while the master node is transmitting on substantially the same band.

19. The media of claim 18 wherein the method further includes:

receiving, at the master node, traffic load information from at least one of the remote nodes;

transmitting to the at least one remote nodes, schedule information, said schedule information operable to cause the remote nodes to transmit traffic on a predetermined schedule.

20. The media as in claim 18 wherein the master node transmits a broadcast signal to one or more remote nodes to synchronize the one or more remote nodes.