Adaptive synchronous protocol for minimizing latency in TDD systems

• US 10,298,383 B2
• Filed: 02/12/2018
• Issued: 05/21/2019
• Est. Priority Date: 08/25/2011
• Status: Active Grant

• Current Assignee: Ubiquiti Inc.
• Original Assignee: Ubiquiti Networks, Inc. (Ubiquiti Inc.)
• Inventors: Schulz, Gary, Odlyzko, Paul
• Primary Examiner(s): Pezzlo, John
• Application Number:
  US15/894,598
• Publication Number:
  US 20180176004A1
• Time in Patent Office: 463 Days
• Field of Search: 370252, 370278, 370294, 370442, 370503
• 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 system connected to a network comprised of computers, the system comprising:

a master node;

one or more remote nodes;

a transmission medium,

wherein the transmission medium is capable of supporting a data link between the master node and the one or more remote nodes;

a time reference;

a datum, wherein the data consists of one or more data symbols, wherein the data symbols are contained in one or more frames; and

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

wherein the schedule is arranged to maximize frame efficiency and for communications between the master node and the one or more remote nodes.

2. The system of claim 1, wherein a frame size represents selected data transmitted in one frame as the frame is transmitted across the transmission medium, wherein the frame size is allocated as a whole integer multiple of data symbols, and wherein the frame size is determined, at least in part, by a propagation time of data symbols transmitted between the master node and the one or more remote nodes.

3. The system of claim 2, wherein the schedule instructs the master node to send at least one request grant protocol,

wherein the request grant protocol provides permission for a remote node to transmit one or more frames, and

wherein the frames are sent during one or more transmission periods.

4. The system of claim 3, wherein the schedule instructs the master node and one or more remote nodes to avoid network traffic collisions via at least:

the time reference and,

the submission of one or more request grant protocols,

wherein the one or more request grant protocols coordinate alternating transmission periods of frames sent by either the master node or the one or more remote nodes.

5. The system of claim 1, wherein an end-of-transmit instruction causes the master node or the remote node to cease transmitting,

wherein a start-of-receive instruction causes a master node or a remote node to begin receiving, and

wherein a transition time denotes a delay between reception of the end-of-transmit instruction and reception of the start-of-receive instruction.

6. The system of claim 5, wherein the schedule instructs the master node and the one or more remote nodes to simultaneously transmit data across the transmission medium, and

wherein said simultaneous transmission occurs approximately until data symbols arrive at either the master node or the one or more remote nodes across the transmission medium.

7. The system of claim 5, wherein the schedule instructs the master node and the one or more remote nodes to simultaneously transmit data across the transmission medium, and

wherein the schedule causes the transmission of the end-of-transmission instruction and the start-of-receive to the master node and the one or more remote nodes approximately before data symbols arrive at either the master node or the one or more remote nodes across the transmission medium.

8. The system of claim 1, wherein the master node periodically sends one or more ranging messages to at least one remote node,

wherein the ranging messages determine the distance between a master node and at least one remote node,

wherein the frame size is decreased when the distance between a master node and at least one remote node is decreased, and

wherein the frame size is increased when the distance between a master node and at least one remote node is increased.

9. The system of claim 1 wherein degree of temporal overlap of the transmission of the master node and at least one of the one or more remote nodes is proportional to the distance between the at least one of the one or more remote node.

10. The system of claim 1, wherein the schedule instructs the one or more remote nodes to enter a listening state and await one or more pertinent control messages from the master node, and

wherein the one or more remote nodes refrain from transmitting data while in the listening state.

11. The system of claim 1, wherein the system employs a time-division multiplexing communications scheme.

12. The system of claim 1, wherein the system employs a orthogonal frequency-division multiplexing communications scheme.

13. The system of claim 1, wherein the system employs a fast-Fourier transform algorithm to sample the transmission medium and reconstruct a transmitted signal.

14. The system of claim 1, wherein the remote nodes are of varying distances from the master node.

15. The system of claim 1, wherein the transmission medium is either air, space, or conductive material.

16. A system connected to a network comprised of computers, the 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, 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 maximize frame efficiency and for communications between the master node and the one or more remote nodes and at least a portion of the schedule is communicated to the one or more remote nodes.