Radio signal data transmission synchronization

• US 5,189,411 A
• Filed: 10/10/1990
• Issued: 02/23/1993
• Est. Priority Date: 11/27/1985
• Status: Expired due to Term

• Current Assignee: Protocol-ip.com, LLC, Seiko Instruments Incorporated (Seiko Group)
• Original Assignee: Seiko Corporation (Seiko Group), Seiko Epson Corporation (Seiko Group)
• Inventors: Shanks, Carl D., Wells, Rick T., Collar, James K., Park, Daniel J., Gaskill, Garold B.
• Primary Examiner(s): Yusko, Donald J.
• Assistant Examiner(s): Weissman, Peter
• Application Number:
  US07/595,145
• Time in Patent Office: 867 Days
• Field of Search: 340/825.14, 340/825.2, 340/825.44, 370/94.1, 370/100.1, 370/101, 370/102, 375/107, 375/112
• US Class Current: 340/7.2
• CPC Class Codes: G04G 21/04 using radio waves radio-controlled time-pieces G04R
• CPC Class Codes: G04R 20/20 the radio signal being an AM/FM standard signal, e.g. RDS
• CPC Class Codes: G08B 3/1016 using wireless transmission calling systems using transmission by inductive loop H04B5/00
• CPC Class Codes: G08B 5/222 Personal calling arrangements or devices, i.e. paging systems selective calling systems and call receivers H04W84/00, H04W68/00
• CPC Class Codes: G08B 5/223 using wireless transmission
• CPC Class Codes: H04L 1/18 Automatic repetition systems, e.g. Van Duuren systems
• CPC Class Codes: H04W 88/022 Selective call receivers
• CPC Class Codes: H04W 88/026 using digital address codes
• CPC Class Codes: H04W 88/185 Selective call encoders for paging networks, e.g. paging centre devices
• CPC Class Codes: H04W 88/187 using digital or pulse address codes

Abstract

Real time synchronization of radio signal data is achieved by a feedback loop between a clearinghouse generating data and a radio station transmitting data. Transmission time is adjusted in response to detected timing errors by selectively inserting padding data between certain data packets to shift data packet position within a data stream transmitted at a predetermined transmission rate. Data flow control is achieved by use of variable length flags delimiting data packets whereby longer flags result in less data flow and shorter flags result in greater data flow.

Claims

1. A method of transmitting time of day information by radio signal, the method comprising:

providing a transmission sequence of data packets to be transmitted at a predetermined transmission rate, said data packets including time packets carrying time of day information corresponding to an expected time of transmission, said transmission sequence including padding data selectably inserted between the data packets;

transmitting said transmission sequence of data packets substantially at said predetermined transmission rate;

detecting a time of transmission for ones of said data packets;

comparing detected times of transmission with expected times of transmission for said data packets to calculate a timing error representing a difference between time of day information carried in a given time packet and a calculated time of transmission for the given time packet; and

modifying the amount of padding data within said transmission sequence based on said timing error to cause transmission of subsequent time packets substantially at a time corresponding to the time of day information carried therein.

2. The method according to claim 1 wherein said modifying step includes providing more padding data to delay transmission of subsequent data packets in response to a detected timing error indicating early transmission of data packets and providing less padding data to advance transmission time of subsequent data packets in response to a detected timing error indicating late transmission of data packets.

3. A method of adjusting a time of radio signal transmission for data packets in a synchronous communication protocol, the method comprising:

ordering the data packets in a transmission sequence corresponding to an associated predetermined time of transmission for each packet in accordance with the synchronous communication protocol;

selectably inserting padding data between selected data packets in said transmission sequence;

transmitting said transmission sequence of data packets including said padding data;

determining a time of transmission for ones of said data packets;

comparing the time of transmission for said ones of said data packets to establish a transmission timing error; and

adjusting time of transmission for subsequent data packets as a function of said transmission timing error by modifying the amount of padding data inserted into said transmission sequence.

4. A method of indicating a time of radio signal transmission for communication data, the method comprising:

coupling a communication data generating process and a communication data transmitting process by means of a bi-directional communication link;

providing said communication data on a first leg of said bi-directional communication link from said data generating process to said data transmitting process;

modulating at said data transmission process the communication data received on said first leg at a predetermined transmission rate to produce a modulated signal for radio signal transmission;

extracting as verification data said communication data from said modulated signal for radio signal transmission;

providing said verification data on a second leg of said bi-directional communication link to said data generating process, said second leg having a first portion carrying a variable volume of said verification data and a second portion operating at a predetermined data rate;

providing within said verification data indicia of time of transmission for selected portions of communication data within said verification data, said indicia of time of transmission indicating when said first portion of said second leg carries a predetermined volume of said verification data.

5. The method according to claim 4 wherein a time of transmission for a given portion of said communication data is calculated by reference to said predetermined data rate, said predetermined volume, and a time of receiving at said data generating process said indicia of time of transmission.

6. The method according to claim 5 wherein said communication data is transmitted in accordance with a synchronous transmission protocol wherein each portion of said communication data is to be transmitted at an associated predetermined time, and said method further comprises:

comparing said calculated time of transmission for said given portion of said communication data with said associated predetermined time of transmission; and

inserting padding data within said communication data to adjust a time of transmission for subsequent portions of said communication data, the volume of said inserted padding data being a function of said comparing step.

7. A method of transmitting communication data by radio signal in accordance with a synchronous communication protocol requiring transmission of data packets at associated predetermined times, the method comprising:

collecting the communication data as said data packets in a transmission sequence corresponding to the associated predetermined times for said data packets;

selectably inserting padding bits between said data packets in said transmission sequence;

modulating said data packets including said inserted padding bits on a carrier signal to provide a modulated carrier signal adapted for radio signal transmission;

delivering the modulated carrier signal by an antenna communication link to a radio signal transmission antenna for radio signal transmission of said modulated carrier signal; and

monitoring said antenna communication link to extract said data packets as verification data, said verification data further including indicia of time of transmission with respect to a given one of said extracted data packets,

whereby selection of padding bits for insertion within said transmission data sequence is a function of timing errors detected by comparison of said indicia of time of transmission relative to the associated predetermined time of transmission for said given data packet.

8. The method according to claim 7 wherein said verification data is delivered on a verification communication link operating at a predetermined rate and carrying a varying volume of said verification data whereby said indicia of time of transmission marks said given data packet in association with said verification communication link containing a predetermined volume of data.

9. The method according to claim 8 wherein said verification communication link includes a buffer containing a variable volume of said verification data and the remaining portions of said verification communication link carry a known volume of said verification data and said predetermined volume of verification data is detected by a predetermined volume of verification data within said buffer.

10. The method according to claim 7 wherein said method further comprises:

delivering said verification data on a verification communication link operating at a predetermined rate and carrying a varying volume of said verification data;

providing said indicia of time of transmission in association with said given data packet when said verification communication link contains a known volume of data; and

establishing a time of arrival for said binary variable of said predetermined value at a terminal portion of said verification communication link.

11. The method according to claim 7 wherein the number and distribution of said padding data inserted within said transmission sequence as a function of said detected timing errors is such to maintain time of transmission for said data packets at associated predetermined times of transmission.

12. The method according to claim 11 wherein the amount of padding data inserted within said transmission sequence is increased when a detected timing error indicates that said given data packet is transmitted earlier than its associated predetermined time of transmission.

13. The method according to claim 11 wherein the amount of padding data inserted within said transmission sequence is decreased when a detected timing error indicates that said given data packet is transmitted later than its associated predetermined time of transmission.

14. The method according to claim 7 including consecutive periods of sampling to establish an average timing error, periods of correction for inserting padding data to correct the timing error, and periods of holdoff wherein no sampling or correction occurs.

15. In a synchronous communication protocol requiring transmission of data packets at predetermined times relative to a time reference and within a given margin of timing error, selected ones of said data packets being separable by padding bits, a method of maintaining transmission synchronization comprising:

constructing at a data generating installation the data packets and ordering the data packets in accordance with a transmission sequence;

providing the ordered data packets to a transmission installation;

transmitting the ordered data packets from the transmission installation;

providing to said data generating installation as verification data the ordered data packets as transmitted, said verification data being marked in accordance with a time of transmission;

receiving said verification data at said data generating installation, detecting marked verification data, and comparing a time of transmission indicated by said marked verification data with an expected time of transmission for said marked verification data to detect a transmission timing error; and

upon detecting a transmission timing error, inserting additional padding bits between selected ones of said data packets in said ordered data packets or removing selected ones of said padding bits between selected ones of said data packets in said ordered data in accordance with said detected timing error to maintain data transmission within said margin of error.

16. The method according to claim 15 wherein said step of marking verification data comprises the steps:

monitoring a volume of data in a return data path operating at a predetermined return path data rate, said return data path providing said verification data to said data generating installation; and

marking verification data when said return path data volume equals a known volume,

whereby said data generating installation determines a time of transmission by detecting the marked verification data, referencing said predetermined return path volume, and referencing said predetermined return path data rate.