Control interface protocol for telephone sets for a satellite telephone system

• US 20010005377A1
• Filed: 12/07/2000
• Published: 06/28/2001
• Est. Priority Date: 11/30/1998
• Status: Active Grant

• Current Assignee: Clement B. Edgar III, Gibson R. Nicholson
• Original Assignee: Clement B. Edgar III, Gibson R. Nicholson
• Inventors: Edgar, Clement B. III, Gibson, R. Nicholson
• Granted Patent: US 6,724,753 B2
• Time in Patent Office: Days
• US Class Current: 370/445
• CPC Class Codes: H04B 7/18582 Arrangements for data linking, i.e. for data framing, for error recovery, for multiple access
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 1/1838 for semi-reliable protocols, e.g. for less sensitive applications such as streaming video buffer level management for video bitstream receiver H04N21/44004
• CPC Class Codes: H04L 1/188 Time-out mechanisms
• CPC Class Codes: H04L 12/403 with centralised control, e.g. polling
• CPC Class Codes: H04L 12/413 with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
• CPC Class Codes: H04L 2001/0093 Point-to-multipoint
• CPC Class Codes: H04M 9/02 involving a common line for all parties

Abstract

A control interface protocol governs communications in a satellite telephone system. The satellite telephone system comprises a radio antenna unit (RAU) and a plurality of desksets connected to the RAU. An interface bus connects the desksets to the RAU. The RAU and the desksets communicate with each other by packets. Each packet comprises a start of header (SOH) byte, an address number (ADDR) byte, a command (CMD) byte, an argument (ARG) and a block check character (BCC). The ADDR byte comprises a source and a destination address of the packet. All packets, except negative acknowledgment (NAK) packets from the desksets, are acknowledged by the RAU. The packets originating from the desksets are tagged with an address of the desksets. A packet to a specific deskset includes a destination address. A packet originating from the RAU to all desksets includes a first default address. A packet originating from the RAU to a deskset that does not have an address includes a second default address.

Claims

1. A telephone apparatus, comprising:

a transceiver that communicates with a central station;

a plurality of desksets; and

an interface bus that permits said desksets to communicate with said transceiver.

2. The apparatus of

claim 1

, wherein said interface bus interface transceiver and said desksets exchange packets over said interface bus, each packet comprising:

an address (ADDR) byte that includes source and destination addresses of the packet;

a command (CMD) byte;

an argument (ARG); and

a block check character (BCC) for error checking.

3. The apparatus of

claim 2

, wherein said BCC is produced by a longitudinal parity check.

4. The apparatus of

claim 2

, wherein said BCC is produced by a cyclic redundancy check.

5. The apparatus of

claim 2

, wherein each packet further comprises a start of header (SOH) byte that indicates the start of the packet.

6. The apparatus of

claim 1

, wherein said interface bus comprises a pair of conductors.

7. The apparatus of

claim 1

, wherein said interface bus comprises an unshielded twisted pair.

8. The apparatus of

claim 1

, wherein said interface bus comprises an EIA-485 interface.

9. The apparatus of

claim 1

, wherein a media access layer of said interface bus is carrier sense multiple access with collision detect.

10. In a communication system having a plurality of terminals connected to a common node by a digital interface bus, a method for handling error control for packets sent to the terminals by the common node, each packet having modulo-sequential sequence numbers, comprising the steps of:

sending a packet from the common node to one of the terminals; and

sending a negative acknowledgment (NAK) from said one of the terminals to the common node when an error or unexpected sequence number is detected in said packet, wherein said NAK includes the sequence number of the last valid packet received.

11. The method of

claim 10

, further comprising the step of re-sending any lost packets from the common node to said one of the terminals when an unexpected sequence number is detected.

12. The method of

claim 10

, further comprising the step of sending a reboot command from the common node to said one of the terminals when the number of missed packets exceeds a predetermined threshold.

13. The method of

claim 10

, further comprising the step of sending a reboot command from the common node to said one of the terminals when a NAK is received at the common node from said one of the terminals.

14. The method of

claim 10

, further comprising the steps of:

determining that a packet is new when the sequence number in the current packet is one greater than the sequence number in the previous packet;

determining that a packet is repeated when the sequence number in the current packet equals the sequence number in the previous packet;

determining that a packet is repeated when the sequence number in the current packet is N less than the sequence number in the previous packet, where N is a predetermined threshold; and

detecting a bad sequence number otherwise.

15. The method of

claim 10

, further comprising the step of detecting an error based on a block check character in said one of the packets.

16. The method of

claim 10

, further comprising the step of detecting an error when a predetermined period elapses between receipt of successive characters in said one of the packets.