METHOD AND A SYSTEM FOR TIME SYNCHRONISATION BETWEEN A CONTROL CENTRE AND SEVERAL TRANSMITTERS

• US 20110141975A1
• Filed: 06/23/2009
• Published: 06/16/2011
• Est. Priority Date: 07/04/2008
• Status: Active Grant

• Current Assignee: Rohde & Schwarz GmbH & Company KG
• Original Assignee: Rohde & Schwarz GmbH & Company KG
• Inventors: Zurek-Terhardt, Guenther, Herzog, Norman
• Granted Patent: US 8,553,619 B2
• Time in Patent Office: Days
• US Class Current: 370/328
• CPC Class Codes: H04H 20/67 Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/005 Iterative decoding, including iteration between signal detection and decoding operation
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/006 Trellis-coded modulation
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 1/0066 Parallel concatenated codes
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 2001/0093 Point-to-multipoint
• CPC Class Codes: H04L 27/02 Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation H04L27/32 takes precedence
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/43637 involving a wireless protocol, e.g. Bluetooth, RF or wireless LAN [IEEE 802.11] arrangements for wireless networking or broadcasting of information in indoor or near-field type systems H04B10/114
• CPC Class Codes: H04N 21/6131 involving transmission via a mobile phone network wireless downlink channel access H04W74/006
• CPC Class Codes: H04W 72/30 Resource management for broadcast services

Abstract

A central station and several transmitters in a single-frequency network are synchronised. A first reference time signal is generated with a high degree of time and frequency accuracy on the short and long time horizon and a second reference time signal is generated and supplied to the central station with a low degree of time and frequency accuracy on the short time horizon and a high degree of accuracy on the long time horizon. A transport data stream with a temporally variable data rate that corresponds to the frequency of the second reference time signal is generated by means of the central station, said stream being supplied to several transmitters and comprising distributed data packets that contain the transmission instant of the data packet, referenced to the second reference time signal, for the transmitters. The time accuracy of the transmission instant of each data packet is optimised by averaging the time and frequency accuracy of the second reference signal over time. The system temporally offsets the transport data stream received by each transmitter from the central station until the data packets of the transport data stream that each contain a transmission instant are transmitted at the correct transmission instant with regard to the first reference time signal supplied to each transmitter.

Claims

1. A method of time synchronisation between a control centre and a plurality of transmitters in a single frequency network, comprising the steps of:

at least one of generating and receiving a first reference time signal with a high time and frequency accuracy in the short and long time horizon and a second reference time signal supplied to the control centre with a low time and frequency accuracy in the short time horizon and a high time and frequency accuracy in the long time horizon;

generating a transport data stream to be supplied to the plurality of transmitters with a time-variable data rate through the control centre corresponding to the frequency of the reference time signal, wherein data packets containing the transmission time of the data packet referenced to the first reference time signal in the transmitters are distributed within the transport data stream, and wherein the time accuracy of the transmission time of the respective data packet is optimised by time averaging of the time and frequency accuracy of the second reference time signal; and

performing time displacement of the transport data stream received from the control centre by the respective transmitter until the data packets of the transport data stream each containing a transmission time are transmitted, with regard to the first reference time signal supplied to the respective transmitter at the correct transmission time.

2. The method of time synchronisation according to claim 1, wherein the time averaging of the time and frequency accuracy of the second reference time signal is implemented by summing the previously transmitted data packets and weighting with a reference data rate corresponding to the frequency of the first reference time signal.

3. The method of time synchronisation according to claim 1, wherein the time averaging of the time and frequency accuracy of the second reference time signal is implemented through time averaging of the time-variable frequency of the second reference time signal.

4. The method of time synchronisation according to any one of claims 1 to 3, wherein the time interval between two successive transmission times of data packets each containing a transmission time is constant, and the transport data stream within the time interval contains a number of data packets dependent upon the data rate present in the respective time interval.

5. The method of time synchronisation according to claim 4, wherein the data packets received in the respective transmitter before the transmission time of each data packet, correspondingly, are buffered in a buffer of the respective transmitter and accordingly time delayed.

6. The method of time synchronisation according to any one of claims 1 to 3, wherein the time interval between two successive transmission times of data packets each containing a transmission time is time variable, and the transport data stream in every time interval contains in each case a constant number of data packets.

7. The method of time synchronisation according to any one of claims 1 to 3, wherein the transmission time is an absolute time datum referenced to the first or second reference time signal.

8. The method of time synchronisation according to any one of claims 1 to 3, wherein the transmission time is a relative time datum referenced to the first or second reference time signal.

9. The method of time synchronisation according to any one of claims 1 to 3, wherein in order to achieve a high frequency accuracy of the data rate of the transport data stream generated in the control centre in the long time horizon, the data rate of the transport data stream is regulated to the reference data rate.

10. A system for time synchronisation between a control centre and a plurality of transmitters within a single frequency network, comprising:

a first reference signal generator operable to generate a first reference time signal with a high time and frequency accuracy in the short and long time horizon;

a second reference signal generator connected to the reference signal generator operable to generate a second reference time signal with a low time and frequency accuracy in the short time horizon and a high time and frequency accuracy in the long time horizon;

a control centre connected to the second reference signal generator for the generation of a transport data stream supplied to several transmitters with a data rate corresponding to the frequency of the second reference time signal,

wherein data packets with transmission times referenced to the second reference time signal in the transmitters are distributed within the transport data stream,

wherein the time accuracy of the transmission times is optimised by time averaging of the time accuracy of the second reference time signal, and

wherein the transport data stream received from the control centre by the plurality of transmitters are time displaced until the data packets of the transport data stream each containing a transmission time with regard to the first reference time signal supplied in each case to the transmitters are transmitted at the correct transmission time.