Timing system and a method for receiving clock information from a satellite system
An outdoor device of a timing system includes a receiver for receiving clock information from a satellite system, a processing system for running master functionality of a clock synchronization protocol to transfer the clock information to an indoor device of the timing system, and a transceiver for transferring data between the outdoor device and the indoor device. A memory device stores a fixed delay value estimating a time delay from a reception moment of a request message related to the clock synchronization protocol to a transmission moment of a reply message. There is no need to compute a difference between clock times corresponding to the reception moment and the transmission moment because the fixed delay value is used in lieu of the difference in the clock synchronization protocol. Thus, quality requirements related to an oscillator of the outdoor device can be mitigated.
1. An outdoor device for a timing system configured to receive clock information from a satellite system, the outdoor device comprising:
a receiver configured to receive the clock information from the satellite system,
a processor configured to run master functionality of a clock synchronization protocol to transfer the clock information to an indoor device of the timing system,
a transceiver configured to transfer, via a data transfer link, data between the outdoor device and the indoor device in accordance with the clock synchronization protocol, and
a memory device configured to store a fixed delay value estimating a time delay from a moment of reception of a request message related to the clock synchronization protocol at the transceiver to a moment of transmission of a reply message from the transceiver,
wherein the processor is configured to include the fixed delay value into the reply message to be transmitted.
2. The outdoor device according to claim 1 , wherein the processor is configured to prepare a synchronization protocol data unit prior to a reception of a synchronization pulse from the satellite system and to control the transceiver to transmit the prepared synchronization protocol data unit in response to the reception of the synchronization pulse from the satellite system.
3. The outdoor device according to claim 2 , wherein the synchronization pulse is one pulse of a pulse per second signal.
4. The outdoor device according to claim 2 , wherein the processor is configured to compute a clock time value corresponding to a clock time at an upcoming moment of reception of the synchronization pulse from the satellite system and to include the computed clock time value into the synchronization protocol data unit when preparing the synchronization protocol data unit prior to the reception of the synchronization pulse.
5. The outdoor device according to claim 3 , wherein the processor is configured to compute a clock time value corresponding to a clock time at an upcoming moment of reception of the synchronization pulse from the satellite system and to include the computed clock time value into the synchronization protocol data unit when preparing the synchronization protocol data unit prior to the reception of the synchronization pulse.
6. The outdoor device according to claim 1 , wherein the processor is configured to run the master functionality of the clock synchronization protocol otherwise in accordance with the IEEE1588 specification but the processor is configured to include the fixed delay value into a delay response message instead of a difference between a clock time at a moment of reception of a delay request message and a clock time at a moment of transmission of the delay response message.
7. The outdoor device according to claim 1 , wherein the receiver comprises an antenna for receiving radio signals from the satellite system.
8. The outdoor device according to claim 1 , wherein the transceiver is configured to transmit the data between the outdoor device and the indoor device via a cable link.
9. The outdoor device according to claim 1 , wherein the processor is configured to stop a transmit queue of data traffic other than data traffic related to the clock synchronization protocol in response to a reception of a synchronization pulse from the satellite system and to allow transmission of the other data traffic after transmission of a synchronization protocol data unit corresponding to the received synchronization pulse.
10. A timing system for receiving clock information from a satellite system, the timing system comprising:
one or more outdoor devices each comprising a receiver configured to receive the clock information from the satellite system,
an indoor device comprising a processor configured to run slave functionality of a clock synchronization protocol to receive the clock information from the one or more outdoor devices, and
one or more data transfer links each being configured to transfer data between one of the outdoor devices and the indoor device,
wherein each of the one or more outdoor devices further comprises:
a processor configured to run master functionality of the clock synchronization protocol to transfer the clock information to the indoor device,
a transceiver configured to transfer, via the corresponding data transfer link, the data between the outdoor device and the indoor device in accordance with the clock synchronization protocol, and
a memory device configured to store a fixed delay value estimating a time delay from a moment of reception of a request message related to the clock synchronization protocol at the transceiver to a moment of transmission of a reply message from the transceiver,
wherein the processor is configured to include the fixed delay value into the reply message to be transmitted.
11. A method for receiving clock information from a satellite system, the method comprising:
receiving, at an outdoor device of a timing system, the clock information from the satellite system,
running, at the outdoor device, master functionality of a clock synchronization protocol to transfer the clock information to an indoor device of the timing system,
storing, in a memory device of the outdoor device, a fixed delay value estimating a time delay from a moment of reception of a request message related to the clock synchronization protocol at the outdoor device to a moment of transmission of a reply message from the outdoor device,
including the fixed delay value into the reply message to be transmitted, and
transmitting the reply message from the outdoor device to the indoor device.
12. The method according to claim 11 , wherein the method comprises preparing a protocol data unit prior to a reception of a synchronization pulse from the satellite system and transmitting the prepared protocol data unit in response to the reception of the synchronization pulse from the satellite system.
13. The method according to claim 12 , wherein the synchronization pulse is one pulse of a pulse per second signal.
14. The method according to claim 12 , wherein the method comprises computing a clock time value corresponding to a clock time at an upcoming moment of reception of the synchronization pulse from the satellite system and including the computed clock time value into the protocol data unit when preparing the protocol data unit prior to the reception of the synchronization pulse.
15. The method according to claim 13 , wherein the method comprises computing a clock time value corresponding to a clock time at an upcoming moment of reception of the synchronization pulse from the satellite system and including the computed clock time value into the protocol data unit when preparing the protocol data unit prior to the reception of the synchronization pulse.
16. The method according to claim 11 , wherein the master functionality of the clock synchronization protocol is otherwise run in accordance with the IEEE1588 specification but the fixed delay value is included into a delay response message instead of a difference between a clock time at a moment of reception of a delay request message and a clock time at a moment of transmission of the delay response message.
17. The method according to claim 11 , wherein data between the outdoor device and the indoor device is transferred via a cable link connected to the outdoor device and to the indoor device.
18. A non-transitory computer readable medium encoded with a computer program for controlling an outdoor device of a timing system to receive clock information from a satellite system and to transfer the clock information to an indoor device of the timing system, the computer program comprising computer executable instructions for controlling a programmable processor of the outdoor device to:
run master functionality of a clock synchronization protocol to transfer clock information received from the satellite system to the indoor device of the timing system,
read, from a memory device, a fixed delay value estimating a time delay from a moment of reception of a request message related to the clock synchronization protocol at the outdoor device to a moment of transmission of a reply message from the outdoor device,
include the fixed delay value into the reply message to be transmitted, and
control the outdoor device to transmit the reply message from the outdoor device to the indoor device.