# US 2021/0243003 A1 · Receiver for high precision synchronization in a shared medium

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- Number: US 2021/0243003 A1
- Document ID: US20210243003A1
- Status: Published application
- Kind: A1
- Application number: 16/777,094
- Filed: 2020-01-30
- Published: 2021-08-05
- Earliest claimed: 2020-01-30
- Assignees: Roku, Inc.
- Applicants: Roku, Inc.
- Inventors: Jan NEERBEK; Bjorn Reese; Brian Moller
- Web page: https://patentgrep.com/patent/US20210243003A1

## CPC

- H04L 7/0012: {by comparing receiver clock with transmitter clock}
- H04N 21/4305: {Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets (arrangements for synchronising receiver with transmitter by comparing receiver clock with transmitter clock H04L7/0012; arrangements for synchronising receiver with transmitter wherein the receiver takes measures against momentary loss of synchronisation H04L7/0083)}
- H04B 1/713: using frequency hopping
- H04J 3/0661: {using timestamps}
- H04L 7/0331: {with a digital phase-locked loop [PLL] processing binary samples, e.g. add/subtract logic for correction of receiver clock (H04L7/0337 takes precedence)}
- H04N 21/43076: {of the same content streams on multiple devices, e.g. when family members are watching the same movie on different devices}
- H04N 21/43637: {involving a wireless protocol, e.g. Bluetooth®, RF or wireless LAN [IEEE 802.11] (arrangements for wireless networking or broadcasting of information in indoor or near-field type systems H04B10/114)}
- H04N 21/8547: involving timestamps for synchronizing content
- H04W 56/0015: {one node acting as a reference for the others}
- H04W 56/0035: {detecting errors in frequency or phase}
- H04W 56/0085: {detecting a given structure in the signal}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04B: TRANSMISSION
- 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)
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

Some embodiments include an apparatus, method, and computer program product for high precision device synchronization of electronic devices in a shared medium. Some embodiments include a first electronic device that utilizes a combination of synchronization techniques to synchronize with a second electronic device. The first electronic device receives a first signal from the second electronic device that includes network-based synchronization data and marker data, and performs network-based synchronization with the second electronic device at a first synchronization accuracy. The first electronic device receives a second signal, and uses the marker data and phase lock synchronization to detect a frequency change of the second signal received, as well as to determine a corresponding time marker. The first electronic device updates a clock of the first electronic device based at least on the corresponding time marker, the network-based synchronization data, and the marker data.

## Claims

### Claim 1

A first electronic device, comprising:
a transceiver configured to receive wireless communications over a shared medium from a second electronic device;
a processor, coupled to the transceiver, configured to:
receive a first signal via the shared medium comprising data: a network-based time stamp, a corresponding accuracy of the network-based time stamp, and marker data;
perform network-based synchronization with the second electronic device based on the network-based time stamp and the corresponding accuracy, to synchronize a clock of the first electronic device to a clock of the second electronic device within the corresponding accuracy;
receive a second signal at a first frequency;
detect a frequency change of the second signal based on the marker data, wherein the frequency change of the second signal identifies a first time marker;
determine a relative accuracy based at least on the first time marker, the marker data, the network-based time stamp, and the corresponding accuracy; and
update the clock of the first electronic device based at least on the relative accuracy.

### Claim 2 (depends on 1)

The first electronic device of claim 1, wherein the marker data comprises a rate of frequency change of the second signal:
x+∝*m*δt,
where x is the network-based time stamp, δt is the corresponding accuracy, ∝ is a settable value greater than 2, and m is an integer.

### Claim 3 (depends on 2)

The first electronic device of claim 2, wherein the first time marker is a time, t,
wherein the clock of the first electronic device indicates t=x+∝*m*δt+δx, where δx is the relative accuracy, and −δt=<δx=<δt; and
wherein the clock of the second electronic device indicates t=x+∝*m*δt, for some value of m.

### Claim 4 (depends on 1)

The first electronic device of claim 1, wherein the shared medium is wave-based and wherein to detect the frequency change of the second signal, the first electronic device further comprises:
a phase lock loop (PLL) circuit coupled to the processor, wherein the PLL circuit performs PLL synchronization.

### Claim 5 (depends on 4)

The first electronic device of claim 4, wherein the PLL synchronization is based on a frequency change, amplitude change, or a presence change of the second signal.

### Claim 6 (depends on 5)

The first electronic device of claim 5, wherein the rate of frequency change is based on frequency hopping.

### Claim 7 (depends on 1)

The first electronic device of claim 1, wherein the marker data comprises a known number of wave pulses, m, of the second signal, and to detect the frequency change of the second signal, the processor is configured to:
subsequent to updating the clock of the first electronic device, count a number of wave pulses of the second signal received;
determine that the count satisfies m;
determine a second time marker corresponding to the m count being satisfied; and
update the clock of the first electronic device based at least on the second time marker.

### Claim 8 (depends on 1)

The first electronic device of claim 1, wherein the first signal comprises: a WiFi signal, a radio frequency (RF) signal, an infrared (IR) frequency signal, a sound signal, or a light signal.

### Claim 9 (depends on 8)

The first electronic device of claim 8, wherein the first signal is a different type of signal than the second signal.

### Claim 10 (depends on 8)

The first electronic device of claim 8, wherein the first signal is a same type of signal as the second signal.

### Claim 11 (depends on 8)

The first electronic device of claim 8, wherein the first signal comprises a WiFi synchronization beacon signal.

### Claim 12 (depends on 1)

The first electronic device of claim 1, wherein the processor is further configured to implement a machine learning algorithm to detect the frequency change of the second signal.

### Claim 13 (depends on 12)

The first electronic device of claim 12, wherein the machine learning algorithm comprises a convolutional neural network (CNN) or long short-term memory network (LSTM).

### Claim 14 (depends on 1)

The first electronic device of claim 1, wherein the processor is configured to use a subsequent frequency change as a heartbeat for the clock of the first electronic device.

### Claim 15 (depends on 1)

The first electronic device of claim 1, wherein the processor is configured to use network time protocol (NTP), hypertext transfer protocol (HTTP), or a proprietary protocol to receive the wireless communications.

### Claim 16

A method for a first electronic device, comprising:
receiving from a second electronic device, a first signal comprising data: a network-based time stamp, a corresponding accuracy of the network-based time stamp, and marker data;
performing network-based synchronization with the second electronic device based on the network-based time stamp and the corresponding accuracy, to synchronize a clock of the first electronic device to a clock of the second electronic device within the corresponding accuracy;
receiving a second signal at a first frequency;
detecting a frequency change of the second signal based on the marker data, wherein the frequency change of the second signal identifies a time marker;
determining a relative accuracy based at least on the first time marker, the marker data, the network-based time stamp, and the corresponding accuracy; and
updating the clock of the first electronic device based at least on the relative accuracy.

### Claim 17

A non-transitory computer-readable medium storing instructions that, when executed by a processor of a first electronic device, cause the processor to perform operations, the operations comprising:
transmitting a first signal over a shared medium, wherein the first signal comprises network synchronization data and marker data;
transmitting a second signal on a base frequency;
performing network-based synchronization with a second electronic device, wherein a clock of the second electronic device is updated based on the network synchronization data;
determining that the marker data is satisfied at a time marker; and
based on the determination, transmitting the second signal on an excited frequency, where the excited frequency is different than the base frequency,
wherein the second electronic device detects a frequency change of the second signal, and updates the clock of the second electronic device based on: the time marker, the network synchronization data, and the marker data.

### Claim 18 (depends on 17)

The non-transitory computer-readable medium of claim 17,
wherein the network synchronization data comprises: a network-based time stamp, x, and a corresponding accuracy of the network-based time stamp, δt;
wherein the marker data comprises: a rate of frequency change of the second signal comprising:
x+∝*m*δt,
where ∝ is a settable value greater than 2, and m is an integer.

### Claim 19 (depends on 18)

The non-transitory computer-readable medium of claim 18, wherein the operations further comprise:
determining that m is not an odd value;
in response to m being an even value, changing a frequency of the second signal to the excited frequency; and
incrementing m.

### Claim 20 (depends on 18)

The non-transitory computer-readable medium of claim 18, wherein the operations further comprise:
determining that m is an odd value;
in response to m being an odd value, changing a frequency of the second signal to the base frequency; and
incrementing m.