Transparent Mesh Overlay in Hub-Spoke Satellite Networks

• US 20100034136A1
• Filed: 08/10/2009
• Published: 02/11/2010
• Est. Priority Date: 08/11/2008
• Status: Active Grant

• Current Assignee: Gilat Satellite Networks Limited
• Original Assignee: Gilat Satellite Networks Limited
• Inventors: HALFON, Haim, LEVITAS, Guy, BRENER, Snir, HACCOON, Eran
• Granted Patent: US 8,804,606 B2
• Time in Patent Office: Days
• US Class Current: 370/321
• CPC Class Codes: H04B 7/18584 Arrangements for data networking, i.e. for data packet routing, for congestion control data switching networks H04L12/00
• CPC Class Codes: H04J 3/0644 External master-clock
• CPC Class Codes: H04L 7/0008 Synchronisation information channels, e.g. clock distribution lines
• CPC Class Codes: H04N 21/242 Synchronization processes, e.g. processing of PCR [Program Clock References] arrangements for synchronising broadcast or distribution via plural systems in broadcast distribution systems H04H20/18
• CPC Class Codes: H04N 21/4305 Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets arrangements for synchronising receiver with transmitter by comparing receiver clock with transmitter clock H04L7/0012; arrangements for synchronising receiver with transmitter wherein the receiver takes measures against momentary loss of synchronisation H04L7/0083
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

In a satellite-based communication network comprised of a central hub and plurality of remote terminals configured to transmit data to and receive data from the central hub in accordance with EN 301 790 (DVB-RCS), and where one or more of these remote terminals may be configured to include an additional receiver module configured to receive MF-TDMA transmission of other remote terminals, a mesh receiver and methods for coupling the mesh receiver with the host remote terminal. In addition, described herein are methods for synchronizing the mesh receiver on the network'"'"'s timing and frequency and for utilizing the available link power for achieving efficient connectivity.

Claims

1. In a satellite communication system comprised of a central hub and plurality of remote terminals, wherein one or more of these remote terminals are configured to support mesh connectivity, a mesh receiver configured to receive MF-TDMA transmissions from other remote terminals, said mesh receiver comprising:

a signal splitter;

two or more frequency synthesizers;

two or more configurable tuners;

a channel switch;

at least one demodulator;

at least one decoder;

at least one processor;

at least one transport stream demultiplexer; and

synchronization and control circuits.

2. The mesh receiver of claim 1, wherein each configurable tuner is configured to:

receive a copy of an input signal from the signal splitter;

receive a local oscillator signal from one frequency synthesizer;

extract or filter a signal of interest from the copy of the input signal; and

convert the extracted signal to a digitally sampled signal.

3. The mesh receiver of claim 1, wherein the channel switch is configured to:

receive two or more digitally sampled signals from two or more tuners, wherein each signal is received over a different input;

select one of the inputs on a per burst basis; and

pass the digitally sampled signal from the selected input to at least one demodulator.

4. The mesh receiver of claim 1, wherein each demodulator is configured to:

receive information corresponding to expected bursts and their expected modulation types;

demodulate each received burst according to the expected modulation type;

forward blocks of demodulated coded bits to a decoder; and

provide measurements for each received bursts, including but not limited to a frequency offset measurement and a reception level measurement.

5. The mesh receiver of claim 1, wherein the transport stream demultiplexer is configured to:

receive a transport stream comprised of a plurality of frames immediately following one another;

extract at least a burst time plan table from the transport stream; and

forward the extracted burst time plan table to a processor.

6. The mesh receiver of claim 1, wherein each processor is configured to:

receive blocks of user bits from one or more decoders;

extract frames of interest from the blocks of user bits;

assemble the extracted frames into packets or messages; and

forward the packets or messages to a host terminal via an Ethernet interface.

7. The mesh receiver of claim 1, wherein the synchronization and control circuits are configured to:

receive a reference clock and a frame synchronization signal;

drive a counter using the reference clock;

load a predetermined value into the counter upon a transition of the frame synchronization signal; and

provide interrupts, sample clocks and other control signals on a burst-by-burst basis to one or more other modules according to the values of the counter.

8. The mesh receiver of claim 1, wherein the mesh receiver is hosted in a remote terminal comprising:

at least one tuner;

at least one demodulator;

at least one demultiplexer;

at least one modulator;

at least one output power control module;

at least one processor coupled to volatile or non-volatile memory devices

at least one Ethernet interface; and

synchronization circuits.

9. The mesh receiver of claim 8, wherein the synchronization circuits of the remote terminal are configured to:

receive timestamps of a network clock reference;

reconstruct a reference clock (PCR) using said received timestamps;

provide signals for timing the remote terminal'"'"'s transmissions so that these transmissions arrive at the satellite at their designated times; and

generate a frame synchronization signal for synchronizing a mesh receiver.

10. The mesh receiver of claim 8, wherein each tuner includes a configurable down converter capable of tuning on a forward link signal.

12. The mesh receiver of claim 8, wherein the remote terminal is configured to couple with an antenna or with an LNB mounted on an antenna, wherein:

the antenna or the LNB are configured to couple to a first port of the mesh receiver, wherein the first port is configured to receive an input signal;

a tuner of the remote terminal is configured to couple to a second port of the mesh receiver, wherein the second port includes a copy of the input signal;

the tuner of the remote terminal is configured to provide DC current and voltage to the LNB; and

DC current and voltage are passed to a coupled LNB via the mesh receiver'"'"'s second and first ports.

13. The mesh receiver of claim 8, wherein the remote terminal is configured to:

couple the reference clock input of a mesh receiver with a reconstructed reference clock (PCR) generated by its synchronization circuits;

couple the frame synchronization input of a mesh receiver with the frame synchronization signal generated by its synchronization circuits;

couple the transport stream input of a mesh receiver with a transport stream output of its demodulator;

couple the external reference signal input of a mesh receiver with the reference signal of the remote terminal'"'"'s tuner; and

couple the Ethernet interface of a mesh receiver with an Ethernet interface of the remote terminal.

11. The mesh receiver of claim 32, wherein each down converter is further configured to include a reference signal or to receive a reference signal, for generating a local oscillator signal.

14. A method of synchronizing a mesh receiver in a remote terminal in a satellite communication system comprised of a central hub and plurality of remote terminals, comprising:

reconstructing a reference clock (PCR) at the remote terminal and coupling it with the mesh receiver;

generating a frame synchronization signal at the remote terminal and coupling it with the mesh receiver;

calculating at the remote terminal a local reference clock (PCR) value corresponding to the timing of a next significant edge of the frame synchronization signal; and

sending a packet from the remote terminal over an Ethernet interface to the mesh receiver, wherein the packet includes a calculated reference clock value.

15. The method of claim 14, wherein the remote terminal is configured to send a packet containing a calculated reference clock value at least a predetermined interval prior to the occurrence of a corresponding next significant edge of the frame synchronization signal.

16. The method of claim 14, further comprising at the mesh receiver:

receiving a reference clock (PCR);

driving a local reference clock counter;

receiving a frame synchronization signal;

receiving a packet containing a reference clock value; and

loading the reference clock value into the reference clock counter at the timing of the closest significant edge of the frame synchronization signal.

17. The method of claim 16, further comprising:

at the mesh receiver, upon loading the reference clock value into the reference clock counter, comparing the clock reference value to be loaded with a current value of the clock reference counter; and

notifying the remote terminal if the difference between the two clock reference values exceeds a predefined threshold.

18. A method of synchronizing a mesh receiver in a first remote terminal in a satellite communication system comprised of a central hub and plurality of remote terminals, comprising:

establishing a mesh connection between the first remote terminal and a second remote terminal;

receiving utility transmission bursts, not containing user data, from the second remote terminal at the first remote terminal, wherein the bursts are transmitted at timeslots allocated for said connection between first and second remote terminals;

assuming an initial frequency offset at the mesh receiver of the first remote terminal; and

adjusting said frequency offset at the mesh receiver of the first remote terminal at least for the purpose of receiving at least one utility burst transmitted by the second remote terminal at a time and frequency matching an allocated timeslot.

19. The method of claim 18, further comprising:

receiving at the mesh receiver at least one frequency offset measurement related to the forward link (Δ

F_FS), wherein said measurement is read from a demodulator at the first remote terminal and sent to the mesh receiver over an Ethernet interface;

measuring at the mesh receiver a frequency error of a reference signal, wherein the reference signal is used for at least generating local oscillators signals at least for the tuners of the mesh receiver and for the tuner of the first remote terminal used for receiving the forward link signal;

calculating at the mesh receiver a frequency error of the forward link'"'"'s tuner (Δ

F_T431) based on the reference signal'"'"'s measured frequency error and knowledge of the nominal frequency of the forward link signal;

calculating at the mesh receiver a frequency error of the mesh receiver'"'"'s tuners (Δ

F_T32x) at an applicable reception frequency;

assuming at the mesh receiver a predefined frequency offset, for at least the purpose of compensating for any offset introduced by hub components (Δ

F_HUB); and

calculating at the mesh receiver an initial frequency offset (Δ

F_RCS) using the formula Δ

F_RCS=Δ

F_FS−

Δ

F_T431+Δ

F_T32x−

Δ

F_HUB.

20. The method of claim 18, wherein receiving bursts transmitted by the second remote terminal at the mesh receiver further comprises:

receiving a terminal burst time plan table (TBTP) transmitted by the hub;

identifying allocations made for said mesh connection based on one or more identifiers provided during connection establishment and comparable to parameters included in the terminal burst time plan table; and

programming a tuner to an appropriate frequency at an appropriate time, wherein the reception frequency is shifted from the nominal frequency by a calculated frequency offset.

21. The method of claim 18, further comprising:

adjusting the value assumed for the frequency offset introduced by hub components (Δ

F_HUB) for at least the purpose of receiving utility bursts transmitted by the second remote terminal at the center or at any other desired position within a predefined frequency window;

determining the frequency offset introduced by hub components (Δ

F_HUB) using the formula Δ

F_RCS=Δ

F_FS−

Δ

F_T431+Δ

F_T32x−

Δ

F_HUB;

storing the determined frequency offset introduced by hub components (Δ

F_HUB) in non-volatile memory; and

terminating said connection between the first and second remote terminals.

22. A method of dynamically determining a mesh factor for a first remote terminal in a satellite communication system comprised of a central hub and plurality of remote terminals, wherein the first remote terminal is configured to include a mesh receiver, the method comprising:

dynamically determining the mesh factor as the difference in link condition between the central hub'"'"'s down-link and the down-link of the first remote terminal.

23. A method of dynamically determining and distributing a mesh factor figure for a remote terminal in a satellite communication system comprised of a central hub and plurality of remote terminals, wherein the mesh factor figure is dynamically determined at the central hub, wherein the first remote terminal is configured to include a mesh receiver, the method comprising at the hub:

receiving a mesh factor reference measurement from a the first remote terminal, wherein the reference measurement includes a mesh factor figure (MF_REF) and a forward link reception level figure (FL_REF);

receiving a forwarding link reception level measurement (FL_CUR) from the first remote terminal; and

calculating an actual mesh factor (MF_ACT) for the first remote terminal using the formula MF_ACT=MF_REF−

(FL_CUR−

FL_REF).