ENSURING PHYSICAL LOCALITY OF ENTITIES SHARING DATA

• US 20090059797A1
• Filed: 08/31/2007
• Published: 03/05/2009
• Est. Priority Date: 08/31/2007
• Status: Active Grant

• Current Assignee: Lattice Semiconductor Corporation
• Original Assignee: Silicon Image, Inc. (Lattice Semiconductor Corporation)
• Inventors: Schmidt, Brian K., Northcutt, J. Duane
• Granted Patent: US 8,233,432 B2
• Time in Patent Office: Days
• US Class Current: 370/238
• CPC Class Codes: H04L 12/2838 Distribution of signals within a home automation network, e.g. involving splitting/multiplexing signals to/from different paths adaptations of television systems for transmission by electric cable for domestic distribution H04N7/106; hybrid transport H04L12/6418; home network arrangements specially adapted for distribution of digital video signals H04N7/24
• CPC Class Codes: H04L 45/122 by minimising distances, e.g. by selecting a route with minimum of number of hops
• CPC Class Codes: H04L 45/126 minimising geographical or physical path length
• CPC Class Codes: H04L 45/70 Routing based on monitoring results
• CPC Class Codes: H04L 63/0492 by using a location-limited connection, e.g. near-field communication or limited proximity of entities
• CPC Class Codes: H04L 63/10 for controlling access to devices or network resources

Abstract

A method and system for ensuring that data is only distributed within a certain physical area are disclosed. In one embodiment, a method provides that data is distributed only if the distance between a source and a sink is within a distance threshold. Under this system, the distance between the source and the sink may be estimated directly or indirectly. In some embodiments, the distance may be estimated by estimating the propagation delay for a signal traversing between the devices. The physical distance between the devices may be determined from the propagation delay. If the physical distance is outside a threshold value, the source may be prohibited from transmitting the data or the sink may refuse to display the data.

Claims

1. A method of controlling distribution of data between entities comprising:

estimating a distance between a first entity and a second entity; and

distributing the data between the first entity and the second entity only if the estimated distance between the first entity and the second entity is within a distance threshold for the data.

2. The method of claim 1 wherein the estimation of the distance between the first entity and the second entity includes:

determining a propagation delay for a signal transmission between the first entity and the second entity; and

calculating a distance based on the propagation delay.

3. The method of claim 2 wherein the determination of the propagation delay includes:

determining a relationship between a clock in the first entity and a clock in the second entity;

transmitting a packet from the first entity to the second entity over a network medium, the packet containing a transmission time;

receiving the packet at the second entity at a receive time;

returning the packet from the second entity at a second transmission time;

receiving the returned packet at the first entity at a second receive time; and

determining the propagation delay using the transmission times and the receive times.

4. The method of claim 3, further comprising establishing the transmission time when a first bit of the packet is transmitted on the network medium, and establishing the receive time when the first bit of the packet is received on the network medium.

5. The method of claim 3, wherein establishing the relationship between the clock of the first entity and the clock of the second entity includes synchronizing the clocks to a time server.

6. The method of claim 2, wherein the determination of the propagation delay is made without determining a relationship between the clock of the first entity and the clock of the second entity.

7. The method of claim 6 wherein the determination of the propagation delay further includes:

transmitting a packet from the first entity to the second entity at a transmission time;

sending a response packet from the second entity to the first entity in response to the packet;

receiving the response packet at the second entity at a receive time; and

determining propagation delay by using a difference between the transmission time and the receive time.

8. The method of claim 1, wherein there is an intermediate node between the first entity and the second entity, and further comprising determining a processing time for the intermediate node.

9. The method of claim 8, further comprising inserting the processing time for the intermediate node into the packet.

10. The method of claim 9, further comprising authenticating the identity of the intermediate node.

11. The method of claim 10, wherein the packet is encrypted, and wherein the intermediate node decrypts the packet to insert the processing time, and re-encrypts the packet for transmission.

12. The method of claim 1, wherein the threshold distance varies depending on the content being distributed.

13. An apparatus comprising;

a distance module configured to estimate the distance from the apparatus to a second apparatus in a network; and

a decision module, the decision module to decide whether a data transmission between the apparatus and the second apparatus is authorized based on a comparison of the distance estimate to a distance threshold.

14. The apparatus of claim 13, wherein the distance module is configured to estimate the distance based on a propagation delay for a signal sent between the apparatus and the second apparatus.

15. The apparatus of claim 14, wherein the signal comprises a data packet, wherein the estimate of the propagation delay is based on the time period from the transmission of the data packet to a receipt of a response packet.

16. The apparatus of claim 14, further comprising timing hardware to determine a transmission time for the signal, a receive time for the signal, or both.

17. The apparatus of claim 16, wherein the timing hardware is utilized to determine a transmission time when a first bit of the packet is placed on the network, to determine a receive time when the first bit of the packet is received on the network, or both.

18. The apparatus of claim 14, further comprising a clock, the apparatus to utilize the clock to estimate the distance between the apparatus and the second apparatus.

19. A system for controlling distribution of data comprising:

a source configured to transmit data;

a sink configured to receive the data;

a distance module configured to estimate a distance between the source and the sink; and

a decision module configured to allow the data to be distributed only if the estimated distance is within a threshold distance for the data.

20. The system of claim 19, wherein the decision module is contained in the source.

21. The system of claim 19, wherein the decision module is contained in a device distinct from the source or the sink.

22. The system of claim 19, wherein the distance module determines distance by determining a propagation delay for a packet transmitted between the source and the sink.

23. The system of claim 22, wherein the source and the sink include timing hardware to determine when the signal is first transmitted, when the signal is first received, or both.

24. The system of claim 23, further comprising one or more intermediate nodes between the source and the sink, wherein each intermediate node determines a processing delay time for the intermediate node.

25. The system of claim wherein each intermediate node inserts the processing delay time into the signal.