TECHNIQUES FOR SYNCHRONIZING A CLOCK OF A WIRED CONNECTION WHEN TRANSMITTED OVER A WIRELESS CHANNEL

• US 20130195233A1
• Filed: 01/25/2013
• Published: 08/01/2013
• Est. Priority Date: 01/26/2012
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Wilocity, Ltd. (Qualcomm, Inc.)
• Inventors: Amichai, Sanderovich
• Granted Patent: US 9,425,948 B2
• Time in Patent Office: Days
• US Class Current: 375/354
• CPC Class Codes: G06F 1/14 Time supervision arrangements, e.g. real time clock
• CPC Class Codes: G09G 2370/10 Use of a protocol of communication by packets in interfaces along the display data pipeline
• CPC Class Codes: G09G 2370/12 Use of DVI or HDMI protocol in interfaces along the display data pipeline
• CPC Class Codes: G09G 2370/16 Use of wireless transmission of display information
• CPC Class Codes: G09G 5/008 Clock recovery
• CPC Class Codes: H04L 7/0012 by comparing receiver clock with transmitter clock

Abstract

An apparatus and method for synchronizing a multimedia interface clock between a multimedia source device and a multimedia sink device connected over a wireless channel. The method comprises measuring a frequency of the source clock signal generated by the multimedia source device, wherein the measurement of the frequency is performed using a first reference clock signal; generating a frequency-stamp message including in part the measured frequency; encapsulating the frequency-stamp message in at least one packet; and transmitting the at least one packet to a wireless receiver connected to the multimedia sink device over the wireless channel.

Claims

1. A method for synchronizing a multimedia interface clock between a multimedia source device and a multimedia sink device connected over a wireless channel, comprising:

measuring a frequency of the source clock signal generated by the multimedia source device, wherein the measurement of the frequency is performed using a first reference clock signal;

generating a frequency-stamp message including in part the measured frequency;

encapsulating the frequency-stamp message in at least one packet; and

transmitting the at least one packet to a wireless receiver connected to the multimedia sink device over the wireless channel.

2. The method of claim 1, further comprising:

receiving the at least one packet;

extracting the frequency-stamp from the at least one packet;

determining the measured frequency based on the contents of the frequency-stamp; and

synthetizing the sink clock signal using the determined measured frequency and a second reference clock signal.

3. The method of claim 2, wherein the first reference clock signal is generated by a first oscillating device, and the second reference clock signal is generated by a second oscillating device, wherein the first and second oscillating devices are distributed from each other.

4. The method of claim 3, wherein the first and second reference clock signals are deviated from each other by up to 20 parts per million (PPM).

5. The method of claim 2, further comprising:

encapsulating multimedia and control signals generated by the multimedia source device in the at least one packet.

6. The method of claim 1, wherein measuring the frequency of the source clock signal further comprising:

counting clock cycles of the source clock signal during a predefined number of clock cycles of the first reference clock signal;

multiplying the cycles'"'"' count by a frequency of the first reference clock; and

dividing the result by the predefined number of clock cycles.

7. The method of claim 2, wherein synthetizing the sink clock signal further comprising;

synthetizing a clock signal having a frequency that is a multiplication of a frequency of the second reference clock signal multiplied by the determined frequency.

8. The method of claim 2, wherein synthetizing the sink clock signal is performed by any one of:

a phase-locked loop (PLL) circuit and a synthesizer.

9. The method of claim 1, wherein the multimedia source device and the multimedia sink device are compatible with a multimedia interface including any one of:

a high-definition multimedia interface (HDMI), a DisplayPort interface, a mobile high-definition link (MHL) interface, and Mobility DisplayPort interface.

10. The method of claim 1, wherein any of the multimedia source device and the multimedia sink device is any one of:

a universal serial bus (USB) device and a peripheral component interconnect express (PCIe).

11. The method of claim 1, wherein the at least one packet is transmitted over the wireless channel using a transport protocol, wherein the transport protocol is at least an IEEE 802.11ad protocol.

12. The method of claim 1, wherein the multimedia source device is connected at a first end of a distributed bus apparatus and the multimedia sink device is connected at a second end of a distributed bus apparatus.

13. The method of claim 1, wherein the distributed bus apparatus is a peripheral component interconnect express (PCIe).

14. An apparatus for synchronizing a multimedia interface clock between a multimedia source device and a multimedia sink device connected over a wireless channel, comprising:

a frequency measurement module for measuring a frequency of a source clock signal generated by the multimedia source device, wherein the measurement of the frequency is performed using a first reference clock signal, wherein the frequency measurement module is further configured to generate a frequency-stamp message including in part the measured frequency;

a packetizer for encapsulating the frequency-stamp message in at least one packet; and

a wireless transmitter for transmitting the at least one packet to a wireless receiver connected to the multimedia sink device over the wireless channel, wherein the measured frequency is recovered using a second reference clock, the measured frequency and the second reference clock are utilized to synthetize a sink clock signal for the multimedia sink device.

15. The apparatus of claim 14, wherein the first reference clock signal is generated by a first oscillating device, and the second reference clock signal is generated by a second oscillating device, wherein the first and second oscillating devices are distributed from each other, wherein the first and second reference clock signals are deviated from each other by up to 20 parts per million (PPM).

16. The apparatus of claim 15, wherein the multimedia source device is connected at a first end of a distributed bus apparatus and the multimedia sink device is connected at a second end of a distributed bus apparatus, wherein the distributed bus apparatus is at least a peripheral component interconnect express (PCIe).

17. The apparatus of claim 14, wherein the apparatus is integrated in a media access control (MAC) operable according to an IEEE 802.11ad standard.

18. An apparatus for synchronizing a multimedia interface clock between a multimedia source device and a multimedia sink device connected over a wireless channel, comprising

a de-packetizer for extracting a frequency-stamp from at least one packet received from a wireless transmitted connected to the multimedia source;

a frequency setting unit for determining a frequency value based on the frequency-stamp, wherein the frequency value is respective of a frequency of a source clock signal and is measured using a first reference clock signal, the source clock signal is generated by the multimedia source device; and

a clock generation unit for synthetizing a sink clock signal for the multimedia source device using the determined frequency value and a second reference clock signal.

19. The apparatus of claim 18, wherein the first reference clock signal is generated by a first oscillating device, and the second reference clock signal is generated by a second oscillating device, wherein the first and second oscillating devices are distributed from each other, wherein the first and second reference clock signals are deviated from each other by up to 20 parts per million (PPM).

20. The apparatus of claim 18, wherein the multimedia source device is connected at a first end of a distributed bus apparatus and the multimedia sink device is connected at a second end of a distributed bus apparatus, wherein the distributed bus apparatus is at least a peripheral component interconnect express (PCIe).

21. The apparatus of claim 18, wherein the apparatus is integrated in a media access control (MAC) operable according to an IEEE 802.11ad standard.