Method and a system for synchronising respective state transitions in a group of devices

1. A method of synchronizing respective state transitions in a group of devices comprising at least one responding device that is communicatively coupled to an initiating device via a communication network, the method comprising:

the at least one responding device receiving a message from the initiating device, the message including a field containing one of a state transition time and a time from which a state transition time is obtainable; and

the at least one responding device jointly making a respective state transition with the initiating device at the state transition time.

2. A method according to claim 1 , wherein at least one state transition comprises executing a task that causes said at least one responding device to make a measurement on a device under test.

3. A method according to claim 1 , wherein the message further comprises another field containing information relating to an event, the information being used by the responding device to determine a state to transition to.

4. A method according to claim 1 , wherein the time from which a state transition time is obtainable comprises a time when the initiating device composes the message.

5. A method according to claim 4 , wherein the state transition time comprises a time that is obtained by adding to the time in the message the longest of the time intervals between the creation of the message by the initiating device and each of the at least one responding device being able to make the state transition.

6. A method according to claim 5 , wherein each time interval between the creation of the message by the initiating device and a responding device making the state transition comprises the sum of:

an upper bound on the time between the creating of the message and the sending of the message at the initiating device;

an upper bound on the delay in the network for delivering the message from the initiating device to the responding device; and

an upper bound on the time between the receiving of the message and the state transitioning at the responding device.

7. A device that makes a state transition when initiated by an initiating device communicatively coupled via a communication network to a group of devices including at least the device, the device comprising:

means that receives a message from the initiating device, the message including a field containing, one of a state transition time and a time from which a state transition time is obtainable, the state transition time being the time at which the group of devices can jointly make a respective state transition; and

means that makes the state transition at the state transition time, wherein at least one of the group of devices is caused to make a measurement on a device under test at a time determined by the message.

8. A device according to claim 7 , wherein the means that makes the state transition comprises a means that executes a task.

9. A device according to claim 7 , wherein the message further comprises another field containing information relating to an event and the means that makes the state transition comprises a means that makes a transition to a state that is determined based on the event.

10. A device according to claim 7 , wherein, the time from which a state transition time is obtainable comprises a time when the initiating device composes the message.

11. A device according to claim 10 , wherein the state transition time comprises a time that is obtained by adding to the time in the message the longest of the time intervals between the creation of the message by the initiating device and each of the devices in the group being able to make the respective state transition.

12. A device according to claim 11 , wherein each time interval between the creation of the message by the initiating device and a device in the group making the respective state transition comprises the sum of:

an upper bound on the time between the creating of the message and the sending of the message at the initiating device;

an upper bound on the delay in the network for delivering the message from the initiating device to the device; and

an upper bound on the time between the receiving of the message and the state transitioning, at the device.

13. A system comprising an initiating device cooperating, with a group of at least one responding device to synchronize respective transitions therein, wherein the initiating device comprises:

means that sends the responding device a message including a field containing one of a state transition time and a time from which a state transition time is obtainable, the state transition time being the time at which the group of devices can jointly make a respective state transition; and

the responding device comprises:

means that receives the message; and

means that makes a respective transition at the state transition time,

wherein said responding device is caused to make a measurement on a device under test at a time determined by the state transition time.

14. A system according to claim 13 , wherein the means that makes the state transition comprises a means that executes a task.

15. A system according to claim 13 , wherein the message further comprises another field containing information relating to an event and the means that makes the state transition comprises a means that makes a transition to a state that is determined based on the event.

16. A system according to claim 13 , wherein the time from which a state transition time is obtainable comprises a time when the initiating device composes the message.

17. A system according to claim 16 , wherein the state transition time comprises a time that is obtained by adding to the time in the message the longest of the time intervals between the creation of the message by the initiating device and each of the responding devices in the group being able to make the respective state transition.

18. A system according to claim 17 , wherein each time interval between the creation of the message by the initiating device and a responding device in the group making the respective state transition comprises the sum of:

an upper bound on the time between the creating of the message and the sending of the message at the initiating device;

an upper bound on the delay in the network for delivering the message from the initiating device to the responding device; and

an upper bound on the time between the receiving of the message and the transitioning at the responding device.