# US 2014/0153560 A1 · Systems and methods for optimization of syncrhonization message transmission intervals in a peer-to-peer network

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- Number: US 2014/0153560 A1
- Document ID: US20140153560A1
- Status: Published application
- Kind: A1
- Application number: 13/789,425
- Filed: 2013-03-07
- Published: 2014-06-05
- Earliest claimed: 2012-11-30
- Assignees: QUALCOMM Incorporated
- Applicants: Qualcomm Incorporated
- Inventors: Yan Zhou; Santosh Paul Abraham; George Cherian
- Web page: https://patentgrep.com/patent/US20140153560A1

## CPC

- H04W 56/001: {Synchronization between nodes}
- H04J 3/0638: {Clock or time synchronisation among nodes; Internode synchronisation (synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43)}
- H04W 56/0015: {one node acting as a reference for the others}
- H04W 56/002: {Mutual synchronization}
- H04W 84/18: Self-organising networks, e.g. ad-hoc networks or sensor networks
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)

## Abstract

Methods, devices, and computer program products for optimization of synchronization message transmission intervals in a peer-to-peer network are described herein. In one aspect, a method for determining an optimized timing for synchronization messages is provided. The method includes receiving clock drift information from other devices on the peer-to-peer wireless communication network. This clock drift information may be used to determine the frequency with which new synchronization messages must be sent in order to keep synchronization error under a certain requirement at other devices, while minimizing the network traffic due to the transmissions of synchronization messages.

## Claims

### Claim 1

A root device in an ad-hoc wireless communication network comprising:
a receiver configured to receive a message from other devices in the network, the message including drift information of clocks of other devices in the network;
a processor configured to set a timing of synchronization frames based, at least in part, on the drift information of clocks of other devices in the network; and
a transmitter configured to transmit synchronization frames in accordance with the set timings.

### Claim 2 (depends on 1)

The root device of claim 1, wherein drift information of clocks of other devices in the network comprises a maximum clock drift in the network and a minimum clock drift in the network.

### Claim 3 (depends on 1)

The root device of claim 1, wherein the processor is further configured to determine a clock drift of the root device.

### Claim 4 (depends on 1)

The root device of claim 1, wherein the processor is configured to set the timing of synchronization frames based, at least in part, on a clock drift of the root device and the drift information of clocks of other devices in the network.

### Claim 5 (depends on 1)

The method of claim 1, wherein the transmitter is configured to transmit synchronization frames which include information of a timing of a next synchronization frame, the timing of the next synchronization frame based at least in part on the set timing of synchronization frames.

### Claim 6

A method of determining a timing of synchronization frames transmitted by a root device in an ad-hoc wireless communication network, the method comprising:
receiving a message from a device in the wireless communication network, the message including drift information of clocks of devices in the network;
determining the timing of synchronization frames, based at least in part on the drift information of clocks of devices in the network; and
transmitting a synchronization frame based at least in part on the determined timing of synchronization frames.

### Claim 7 (depends on 6)

The method of claim 6, where the drift information comprises a maximum clock drift in the network and a minimum clock drift in the network.

### Claim 8 (depends on 7)

The method of claim 7, wherein determining the timing of synchronization frames comprises calculating the timing of synchronization frames, based at least in part on an absolute maximum clock drift threshold and an absolute minimum clock drift threshold and the maximum clock drift in the network and the minimum clock drift in the network.

### Claim 9 (depends on 6)

The method of claim 6, wherein the method further comprises determining a clock drift of the root device.

### Claim 10 (depends on 9)

The method of claim 9, wherein determining the timing of synchronization frames comprises calculating the timing of synchronization frames, based at least in part on the clock drift of the root device and drift information of clocks of devices in the network.

### Claim 11 (depends on 6)

The method of claim 6, wherein transmitting a synchronization frame comprises transmitting a synchronization frame that includes information about a timing of a next synchronization frame, the information about the timing of the next synchronization frame based at least in part on the determined timing of synchronization frames.

### Claim 12

A non-transitory, computer readable medium comprising instructions that when executed cause a processor in a device to perform a method for wireless communication within a peer to peer network, the method comprising:
receiving a message from a device in the wireless communication network, the message including drift information of clocks of devices in the network;
determining a timing of synchronization frames, based at least in part on the drift information of clocks of devices in the network; and
transmitting a synchronization frame based at least in part on the determined timing of synchronization frames.

### Claim 13 (depends on 12)

The non-transitory, computer readable medium of claim 12, wherein the drift information comprises a maximum clock drift in the network and a minimum clock drift in the network.

### Claim 14 (depends on 13)

The non-transitory, computer readable medium of claim 13, wherein determining a timing of synchronization frames comprises calculating a timing of synchronization frames, based at least in part on an absolute maximum clock drift threshold and an absolute minimum clock drift threshold and the maximum clock drift in the network and the minimum clock drift in the network.

### Claim 15 (depends on 12)

The non-transitory, computer readable medium of claim 12, wherein the method further comprises determining a clock drift of a root device.

### Claim 16 (depends on 15)

The non-transitory, computer readable medium of claim 15, wherein determining a timing of synchronization frames comprises calculating the timing of synchronization frames, based at least in part on the clock drift of the root device and drift information of clocks of devices in the network.

### Claim 17 (depends on 12)

The non-transitory, computer readable medium of claim 12, wherein transmitting a synchronization frame comprises transmitting a synchronization frame that includes information about a timing of a next synchronization frame, the information of the timing of the next synchronization frame based at least in part on the determined timing of synchronization frames.

### Claim 18

A wireless device in an ad-hoc wireless communication network comprising:
a receiver configured to receive one or more messages from one or more other devices in the network, the one or more messages including drift information of clocks of other devices in the network;
a processor configured to determine adjusted drift information based at least in part on a clock drift of the wireless device and the drift information of clocks of other devices received in the one or more messages; and
a transmitter configured to transmit a message to other devices in the network, the message including adjusted drift information.

### Claim 19 (depends on 18)

The wireless device of claim 18, wherein the drift information comprises a maximum clock drift in the network and a minimum clock drift in the network, based on information collected by the one or more other devices.

### Claim 20 (depends on 19)

The wireless device of claim 19, wherein the adjusted drift information comprises a maximum clock drift in the network and a minimum clock drift in the network and the processor is configured to determine an adjusted maximum clock drift by calculating the maximum of the clock drift information of the wireless device and the maximum clock drift in the network from each of the one or more received messages and to determine an adjusted minimum clock drift by calculating the minimum of the clock drift information of the wireless device and the minimum clock drift in the network from each of the one or more received messages.

### Claim 21 (depends on 20)

The wireless device of claim 20, wherein the processor is configured to compare the clock drift of the wireless device to an absolute maximum clock drift threshold and to an absolute minimum clock drift threshold to determine the adjusted drift information.

### Claim 22 (depends on 21)

The wireless device of claim 21, wherein the processor is configured to not include the clock drift of the wireless device in the adjusted drift information if the clock drift of the wireless device is above an absolute maximum clock drift threshold or if the clock drift of the wireless device is below absolute minimum clock drift threshold.

### Claim 23 (depends on 18)

The wireless device of claim 18, wherein the processor is further configured to determine a clock drift of the wireless device.

### Claim 24 (depends on 23)

The wireless device of claim 23, wherein the processor is programmed with the clock drift of the clock in the wireless device.

### Claim 25 (depends on 23)

The wireless device of claim 23, wherein the processor is configured to determine the clock drift of the wireless device based at least in part on an accurate external timing source.

### Claim 26 (depends on 18)

The wireless device of claim 18, wherein the processor is further configured to receive a reset message and to determine adjusted drift information based only on the clock drift of the wireless device when the reset message is received.

### Claim 27

A method of transmitting clock drift information in an ad-hoc wireless communication network, the method comprising:
receiving one or more messages over the network, the one or more messages including drift information of clocks of other devices in the network;
determining clock drift information of a wireless device;
comparing the clock drift information of the wireless device to the drift information of clocks of other devices in the network;
determining adjusted clock drift information based on the drift information of clocks of other devices in the network contained in the one or more messages, and based on the clock drift information of the wireless device;
transmitting a message over the network, the message including the adjusted clock drift information.

### Claim 28 (depends on 27)

The method of claim 27, wherein the drift information comprises a maximum clock drift in the network and a minimum clock drift in the network, based on information collected by one or more other devices.

### Claim 29 (depends on 28)

The method of claim 28, wherein the adjusted drift information comprises an adjusted maximum clock drift in the network and an adjusted minimum clock drift in the network and wherein determining adjusted clock drift information comprises:
determining the adjusted maximum clock drift, by calculating the maximum of the clock drift information of the wireless device and the maximum clock drift of other devices in the network from each of the one or more received messages; and
determining the adjusted minimum clock drift, by calculating the minimum of the clock drift information of the wireless device and the minimum clock drift of other devices in the network from each of the one or more received messages.

### Claim 30 (depends on 27)

The method of claim 27, further comprising comparing the clock drift of the wireless device to an absolute maximum clock drift threshold and to an absolute minimum clock drift threshold.

### Claim 31 (depends on 27)

The method of claim 27, wherein determining clock drift information of a wireless device comprises accessing a measurement of the clock drift of the wireless device that is programmed into the wireless device.

### Claim 32 (depends on 31)

The method of claim 31, wherein determining clock drift information of a wireless device comprises calculating the clock drift of the wireless device, based at least in part on an accurate external timing source.

### Claim 33 (depends on 27)

The method of claim 27, further comprising:
receiving a reset message over a network; and
determining adjusted clock drift information in the network based only on the clock drift information of the wireless device.

### Claim 34

A non-transitory, computer readable medium comprising instructions that when executed cause a processor in a device to perform a method of transmitting clock drift information in an ad-hoc wireless communication network, the method comprising:
receiving one or more messages over a network, the one or more messages including drift information of clocks of other devices in the network;
determining clock drift information of a wireless device;
comparing the clock drift information of the wireless device to the drift information of clocks of other devices in the network;
determining adjusted clock drift information based on the drift information of clocks of other devices in the network contained in the one or more messages, and based on the clock drift information of a wireless device;
transmitting a message over the network the message including the adjusted clock drift information.

### Claim 35 (depends on 34)

The non-transitory, computer readable medium of claim 34, wherein the clock drift information comprises a maximum clock drift in the network and a minimum clock drift in the network, based on information collected by one or more other devices.

### Claim 36 (depends on 35)

The non-transitory, computer readable medium of claim 35, wherein the adjusted drift information comprises an adjusted maximum clock drift in the network and an adjusted minimum clock drift in the network, and wherein determining adjusted clock drift information comprises:
determining the adjusted maximum clock drift, by calculating the maximum of the clock drift information of the wireless device and the maximum clock drift of other devices in the network from each of the one or more received messages; and
determining the adjusted minimum clock drift, by calculating the minimum of the clock drift information of the wireless device and the minimum clock drift of other devices in the network from each of the one or more received messages.

### Claim 37 (depends on 34)

The non-transitory, computer readable medium of claim 34, further comprising comparing the clock drift of the wireless device to an absolute maximum clock drift threshold and to an absolute minimum clock drift threshold.

### Claim 38 (depends on 34)

The non-transitory, computer readable medium of claim 34, wherein determining clock drift information of a wireless device comprises accessing a measurement of the clock drift of the wireless device that is programmed into the wireless device.

### Claim 39 (depends on 38)

The non-transitory, computer readable medium of claim 38, wherein determining clock drift information of a wireless device comprises calculating the clock drift of the wireless device, based at least in part on an accurate external timing source.

### Claim 40 (depends on 34)

The non-transitory, computer readable medium of claim 34, the method further comprising:
receiving a reset message over a network; and
determining adjusted clock drift information in the network based only on the clock drift information of the wireless device.