DEVICE FOR SYNCHRONIZING A TIME BASE FOR V2V COMMUNICATION

• US 20130279393A1
• Filed: 03/28/2013
• Published: 10/24/2013
• Est. Priority Date: 04/24/2012
• Status: Active Grant

• Current Assignee: Zetta Research and Development LLC - FORC Series, Zetta Research and Development LLC (Zetta Research, LLC)
• Original Assignee: Zetta Research and Development LLC - FORC Series
• Inventors: Rubin, Kim T., Betts-lacroix, Jonathan
• Granted Patent: US 9,300,423 B2
• Time in Patent Office: Days
• US Class Current: 370/312
• CPC Class Codes: G08G 1/163 involving continuous checking
• CPC Class Codes: H04J 3/1694 Allocation of channels in TDM/TDMA networks, e.g. distributed multiplexers Passive Optical Networks H04Q11/0062
• CPC Class Codes: H04L 67/12 specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks
• CPC Class Codes: H04W 56/0025 synchronizing potentially movable access points
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase
• CPC Class Codes: H04W 74/0816 with collision avoidance
• CPC Class Codes: H04W 76/40 for selective distribution or broadcast

Abstract

A device and vehicle for use in, and system for, a vehicle-to-vehicle (V2V) communication and safety system that uses TDMA communication architecture with a self-synchronized TDMA time base. The time base starts with a GPS and internal clock, then fine-tunes by averaging the time bases of all vehicles within radio range. In the described algorithms, all vehicles within a communication range rapidly converge on a common time base to high precision. The regularly broadcast safety messages themselves are used for time base synchronizing, eliminating the need for separate time stamps or transmissions. A range group of vehicles, first converges itself, then converges the group on a UTC time via GPS. Embodiments include use of vehicle distances in time computations. Applications anti-collision systems, optimized traffic flow and signal timing.

Claims

1. A device of manufacture for sending and receiving vehicle-to-vehicle (V2V) safety messages, in a V2V communication system, comprising a transceiver in a subject vehicle wherein the transceiver is configured to wirelessly broadcast and receive messages comprising a protocol comprising:

a synchronized time base used by all V2V transceivers in the V2V communication system;

a basic time interval, of a predetermined duration, repeating continuously and contiguously, responsive to the synchronized time base;

n contiguous time slots, of a predetermined duration, enumerated from 1 to n, wherein the basic time interval comprises the n time slots;

wherein at least some messages are transmitted in a time-division, multiple-access (TDMA) protocol comprising the basic time interval and the time slots;

an algorithm for self-selecting a selected time slot by the V2V transceiver;

an internal time base synchronization function;

wherein the time base synchronization is responsive to (i) a global positioning satellite transmission;

(ii) an internal clock; and

(iii) a plurality of valid transmissions received from a plurality of similar transceivers in other vehicles within wireless communication range.

2. The device of claim 1 wherein:

the time base further comprises a reference point in time; and

the transceiver further comprises an internal time base adjustment function wherein the amount of time by which the reference point of the internal time base is adjusted is an amount between 0 and the difference between a reference point in time of a valid transmission from a similar transceiver and the internal reference point, inclusive.

3. The device of claim 1 wherein:

the time base further comprises a internal time base adjustment value E0 wherein this value is the time difference between the internal time and UTC; and

the transceiver further comprises an internal time base adjustment function wherein the next value of E0, (that is, E0′

) is computed by the function E0′

=(A+B)/C;

wherein A=k*E0, where k is a non-negative weighting factor;

wherein N is the number of equipped V2V vehicles from which valid messages have been received in a most recent basic time interval;

wherein B=the sum of (Em) over m from 1 to M, where Em is the time difference between the internal time base adjustment value of each transceiver m from which a valid message has been received in the most recent basic time interval and UTC;

wherein C=k+M+u, wherein u is a non-negative weighting factor; and

wherein En are determined by the timing of the physical layer transmissions of the valid received messages.

4. The device of claim 1 wherein:

the time base further comprises a reference point in time; and

the transceiver further comprises an internal time base adjustment function wherein the internal time base adjustment occurs once per basic time interval.

5. The device of claim 1 wherein:

the time base further comprises a reference point in time; and

;

the transceiver further comprises an internal time base adjustment function wherein internal time base adjustment is rate limited such that the rate of adjustment does not exceed a predetermined rate of time per unit time.

6. The device of claim 1 wherein:

the time base further comprises a reference point in time; and

;

the transceiver further comprises an internal time base adjustment function such that the reference point in time converges to a single reference point for all transceivers with wireless communication range.

7. The device of claim 1 wherein the protocol further comprises:

the time base synchronization is further responsive to (v) a distance between the transceiver and the similar transceiver.

9. The device of claim 1 wherein:

the basic time interval is in the range of five milliseconds to two seconds.

10. The device of claim 1 wherein:

the basic time interval is in less than or equal to one second.

11. The device of claim 1 wherein:

the number of time slots is in the range of 20 to 10,000, inclusive.

12. The device of claim 1 wherein the protocol further comprises:

the number of time slots is in the range of 200 to 2000, inclusive.

13. The device of claim 1 wherein the protocol further comprises:

the frequency bands for transmission comprise communication bands allocated by a government for use in Dedicated Short Range Communication (DSRC).

14. The device of claim 1 wherein the protocol further comprises:

the modulation scheme used for broadcast comprises one or more modulation schemes from the set;

(BPSK, QPSK, nQAM, OFDM, CCK).

15. The device of claim 1 wherein:

the vehicles are land vehicles.

16. The device of claim 1 further comprising:

a first range of contiguous time slots p1 to p2 used for a first priority class of messages using TDMA protocol;

a second range of contiguous time slots p3 to p4 used for a second priority class of messages using collision-sense, multiple-access (CSMA) protocol, wherein the second range does not overlap with the first range; and

wherein no transmissions of the second priority class occur outside the time window consisting of p3 to p4 inclusive; and

wherein p1, p2, p3 and p4 are in the range of 1 to n inclusive, and p2>

p1 and p4>

p3.

17. The device of claim 1 wherein:

the transceiver further comprises an internal time base adjustment function;

the time base adjustment function maintains the internal time base within 5 nanoseconds of Coordinated Universal Time (UTC).

18. The device of claim 1 wherein:

An inter-frame time gap is variable, responsive to the current communication range limit of the V2V communication system.

19. A system that uses the device of claim 1.

20. A vehicle comprising the device of claim 1.

8. The device of claim 8 wherein:

the time base synchronization is further responsive to (vi) a difference in distance between the shortest path between the transceiver and the similar transceiver and the path of the valid transmission received.