MF-TDMA FREQUENCY HOPPING

• US 20090016260A1
• Filed: 07/17/2008
• Published: 01/15/2009
• Est. Priority Date: 10/03/2006
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Thesling, William H.
• Granted Patent: US 8,077,652 B2
• Time in Patent Office: Days
• US Class Current: 370/321
• CPC Class Codes: H04B 7/18582 Arrangements for data linking, i.e. for data framing, for error recovery, for multiple access

Abstract

Systems, methods, and devices are described for scheduling and mapping upstream communications in a satellite communications system. The disclosure includes various channelization and frequency hopping techniques. A gateway is described to perform novel allocation of time slots on upstream frequency channels to allow frequency hopping. A subscriber terminal may perform frequency hopping according to the allocation, and the range may be limited to the transition range of a digitally controlled oscillator unit at the subscriber terminal. A gateway is described to allocate time slots on different upstream frequency channels in a prioritized manner. Subscriber terminals may receive the allocation, and then control the assignment of their upstream traffic to the time slots.

Claims

1. A device for generation of wireless upstream signals for satellite communications, the device comprising:

an analog frequency synthesizer unit configured to tune an output signal to a frequency within a frequency range allocated for upstream satellite communications;

a digitally controlled oscillator unit, coupled with the analog frequency synthesizer unit, and configured to vary the output signal among a set of carrier frequencies within a subset of the frequency range;

a receiving unit configured to receive data mapping the wireless upstream signals to different ones of the set of carrier frequencies in a series of time slots, the mapping limited to carrier frequencies within the subset of the frequency range; and

a processing unit, communicatively coupled with the digitally controlled oscillator unit and the receiving unit, and configured to control the digitally controlled oscillator unit to cause the varied output signal to hop between carrier frequencies according to the received data.

2. The device of claim 1, wherein the processing unit is further configured to:

determine the set of carrier frequencies, the set comprising carrier frequencies to which the digitally controlled oscillator unit is capable of transition during an available transition time.

3. The device of claim 1, wherein the processing unit is further configured to:

generate a set of data for transmission, the set of data identifying carrier frequencies to which the digitally controlled oscillator unit is capable of transition during a predetermined transition time.

4. The device of claim 1, wherein the processing unit is further configured to:

identify the different ones of the set of carrier frequencies based at least in part on a determination of settling time for transitions between the different ones.

5. The device of claim 1, wherein the processing unit is further configured to generate data for transmission identifying current bandwidth requirements and associated traffic types for the device.

6. The device of claim 1, wherein the processing unit is further configured to generate data for transmission estimating future bandwidth requirements and associated traffic types.

7. The device of claim 1, wherein,

the subset of the frequency range is allocated for upstream satellite communication for a subset of a plurality of subscriber terminals transmitting upstream in the frequency range, the subset of subscriber terminals associated with a selected sub-channel identifier of a plurality of sub-channel identifiers.

8. The device of claim 1, wherein,

each one of the set of carrier frequencies corresponds to a frequency channel allocated for use in upstream satellite communications;

and

the frequency channels comprise frequency channels in a multi-frequency time-division multiple access system.

9. A method of generating wireless upstream signals for satellite communications, the method comprising:

receiving data including a mapping of time slots to different ones of a set of carrier frequencies within a subset of a frequency range allocated for the wireless upstream signals;

tuning an output signal to a frequency within the subset of the frequency range; and

varying the output signal to hop among the different ones of the set of carrier frequencies according to the received mapping data, the variance limited to a digitally controlled oscillator range to which the output signal is capable of transitioning from the tuned frequency during transitional periods.

10. A device for allocating time slots on a plurality of adjacent frequency channels for upstream satellite communications to a plurality of respective subscriber terminals, the device comprising:

a monitoring unit configured to;

monitor a traffic load on the plurality of adjacent frequency channels; and

determine that the traffic load on a first frequency channel of the plurality of adjacent frequency channels exceeds a first threshold capacity;

a scheduling unit, communicatively coupled with monitor unit, and configured to;

identify a first subscriber terminal of the plurality of respective subscriber terminals, the first subscriber terminal transmitting upstream on the first frequency channel;

select a second frequency channel of the plurality of adjacent frequency channels, the second frequency channel selected based at least in part because the first subscriber terminal is configured with a digitally controlled oscillator unit capable of transitioning between the first frequency channel and the second frequency channel;

allocate a first series of future time slots in the first frequency channel to the first subscriber terminal; and

allocate a second series of future time slots in the second frequency channel to the first subscriber terminal, the second series exclusive of the first series and allocated so as to allow the first subscriber terminal to hop between the first frequency channel and the second frequency channel for respective time slot allocations; and

a transmitting unit, communicatively coupled with the scheduling unit, and configured to transmit data directed at the first subscriber terminal, the data comprising the first series and the second series.

11. The device of claim 10, further comprising:

a receiving unit, communicatively coupled with the monitoring unit, and configured to receive data from the plurality of respective subscriber terminals each transmitting on the first frequency channel requesting future upstream bandwidth,

wherein the monitoring unit is further configured to use the received data in the determination of whether the traffic load on the first frequency channel exceeds the first threshold capacity, the traffic load comprising a future traffic load.

12. The device of claim 10, further comprising:

a receiving unit, communicatively coupled with the monitoring unit, and configured to receive data from the first subscriber terminal transmitting on the first frequency channel and requesting additional upstream bandwidth,

wherein the additional upstream bandwidth causes the traffic load on the first frequency channel to exceed the first threshold capacity.

13. The device of claim 10, further comprising:

a receiving unit, communicatively coupled with the monitoring unit, and configured to receive data from the first subscriber terminal identifying a subset of the plurality of adjacent frequency channels, the identified subset comprising two or more frequency channels the digitally controlled oscillator unit is capable of transitioning to from the first frequency channel.

14. The device of claim 10, wherein the threshold capacity is less than a total capacity for the first frequency channel.

15. The device of claim 10, wherein the scheduling unit is configured to select the second frequency channel based at least in part because the second frequency channel includes a time slot that can be transitioned to coherently from the first frequency channel.

16. The device of claim 10, wherein the scheduling unit is configured to select the second frequency channel based at least in part because the frequency channel is a closest channel from the first frequency channel.

17. The device of claim 10, wherein the scheduling unit is configured to select the second frequency channel based at least in part because the frequency channel is an available channel with more available capacity than other available channels.

18. The device of claim 10, wherein the scheduling unit is configured to select the second frequency channel based at least in part on a settling time associated with transition between the first frequency channel and the second frequency channel.

19. The device of claim 10, wherein the scheduling unit is further configured to:

identify a subset of the plurality of adjacent frequency channels, the subset comprising two or more frequency channels the digitally controlled oscillator unit is capable of transitioning to from the first frequency channel.

20. The device of claim 10, wherein the scheduling unit is further configured to:

assign a first subset of the plurality of adjacent frequency channels for exclusive use among a first subset of the plurality of respective subscriber terminals; and

assign a second subset of the plurality of adjacent frequency channels for exclusive use among a second subset of the plurality of respective subscriber terminals.

21. The device of claim 20, wherein the transmitting unit is further configured to:

transmit a first downstream packet with a first sub-channel identifier in a physical layer header, the first sub-channel identifier used to differentiate packets destined for the first subset of the plurality of respective subscriber terminals; and

transmit a second downstream packet with a second sub-channel identifier in a physical layer header, the second sub-channel identifier used to differentiate packets destined for the second subset of the plurality of respective subscriber terminals

22. The device of claim 20, wherein each of the first subset of frequency channels is adjacent to at least one other frequency channel of the first subset of frequency channels, and each of the second subset of frequency channels is adjacent to at least one other frequency channel of the second subset of frequency channels.

23. A method of allocating time slots on a plurality of adjacent frequency channels for upstream satellite communications, the method comprising:

determining that a traffic load on a first frequency channel of the plurality of adjacent frequency channels exceeds a first threshold capacity;

identifying a subscriber terminal transmitting upstream on the first frequency channel;

selecting a second frequency channel of the plurality of adjacent frequency channels, the second frequency channel selected based at least in part because the subscriber terminal is configured with a digitally controlled oscillator unit configured to transition between the first frequency channel and the second frequency channel;

allocating a first series of time slots in the first frequency channel to the subscriber terminal; and

allocating a second series of time slots in the second frequency channel to the subscriber terminal, the second series exclusive of the first series,

wherein the first and the second series of time slots are allocated to allow the subscriber terminal to hop between the first frequency channel and the second frequency channel for respective time slot allocations.

24. A system for allocating time slots in frequency channels for upstream satellite communications, the system comprising:

a gateway device configured to;

monitor a traffic load on the plurality of adjacent frequency channels;

determine that the traffic load on a first frequency channel of the plurality of adjacent frequency channels exceeds a first threshold capacity; and

select a second frequency channel of the plurality of adjacent frequency channels, the second frequency channel selected based at least in part because a subscriber terminal using the first frequency channel is configured with a digitally controlled oscillator unit to transition between the first frequency channel and the second frequency channel;

allocate a first series of time slots in the first frequency channel to the subscriber terminal;

allocate a second series of time slots in the second frequency channel to the subscriber terminal, the second series exclusive of the first series and allocated so as to allow the subscriber terminal to hop between the first frequency channel and the second frequency channel for respective time slot allocations; and

transmit data including the first series and second series directed at the subscriber terminal via a satellite;

the satellite, in wireless communication with the gateway device and the subscriber terminal, and configured to receive the transmitted data and retransmit the received data to the subscriber terminal; and

the subscriber terminal configured to;

receive the retransmitted data; and

hop between the first frequency channel and the second frequency channel according to the received mapping data.

25. The system of claim 24, wherein the subscriber terminal is configured to:

determine a set of carrier frequencies to which the digitally controlled oscillator unit is capable of transition, each carrier frequency of the set corresponding to a selected one of the adjacent frequency channels; and

transmit data comprising the determined set of carrier frequencies to the gateway device.