System and method for satellite based controlled ALOHA

• US 7,260,069 B2
• Filed: 06/15/2001
• Issued: 08/21/2007
• Est. Priority Date: 06/15/2000
• Status: Active Grant

• Current Assignee: Gilat Satellite Networks Limited
• Original Assignee: Gilat Satellite Networks Limited
• Inventors: Ram, Uzi, Meiri, Tzvi, Heiman, Refi
• Primary Examiner(s): Rao; Seema S.
• Assistant Examiner(s): MEW, KEVIN D
• Application Number:
  US09/880,793
• Publication Number:
  US 20020034165A1
• Time in Patent Office: 2,258 Days
• Field of Search: 370/322, 370/345, 370/347, 370/442, 370/443, 370/444, 370/445, 370/447, 370/458, 370/461, 370/462
• US Class Current: 370/322
• CPC Class Codes: H04B 7/18528 Satellite systems for providing two-way communications service to a network of fixed stations, i.e. fixed satellite service or very small aperture terminal [VSAT] system
• CPC Class Codes: H04B 7/204 Multiple access

Abstract

A system and method for satellite based controlled ALOHA is provided. The system and method configure VSATs so that they accept guidance from a centralized and/or distributed system controller to determine when, where, and/or on what portion of a satellite resource to attempt to access a channel. The system and method take advantage of traffic patterns to maximize efficiency by utilizing a centralized and/or distributed control to determine which VSATs are and are not currently active, and to allocate to a portion of the inbound channel to the active VSATs and a portion of the inbound channel to the inactive VSATs. In a distributed approach, each VSAT decides for itself whether it captures a certain part of the inbound resource or not. This decision can be made based on previous transmissions that went through the part of the inbound intended to be captured.

Claims

1. A system for communicating with a large number of remote satellite locations comprising:

a plurality of a first set of remote terminal devices;

a plurality of second remote terminal devices operating in a dedicated mode using the same overlapping channels; and

a hub site which determines threshold criteria for determining when said remote terminal devices are active, and allocates said channels, wherein when said one of said plurality of second remote terminal devices has been sufficiently active during a sliding window, said one of said plurality of second remote terminal devices directly accesses said channels, wherein collisions between inbound packets from different ones of said first and second remote terminal devices are prevented by allocating one of frequency, time slot, and frequency and time slot to said ones of said first and second remote terminal devices that generate the most inbound traffic, wherein when there are more active ones of said first and second remote terminal devices than there are channels, each of said first and second remote terminal devices is allocated a mini-slot, wherein said hub site calculates load for each of said first and second remote terminal devices and retains loads in memory, and wherein said hub site correlates loads for each of said first and second remote terminal devices with the last time slot in which a burst was last received from each of said first and second remote terminal devices, and maintains said correlated loads in an allocation table.

2. A system for communicating with a large number of remote satellite locations as recited in claim 1, wherein said hub site transmits changes to said allocation table to said first and second remote terminal devices.

3. A system for communicating with a large number of remote satellite locations as recited in claim 1, wherein said hub site updates said allocation table every inbound frame.

7. A system for communicating with a large number of remote satellite locations as recited in claim 1, wherein said allocation table comprises information relating to a number of frequencies a remote terminal device is capable of utilizing, a number of mini-slots said remote terminal device may receive, a total number and identification of free inbound ones of said channels and mini-slots, a minimum and assigned maximum load value allocated to each of said first and second remote terminal device, current inbound resources allocated to each of said plurality of first and second remote terminal devices, whether said remote terminal device may become an active site, and whether said remote terminal device has any weighting factors associated with its load calculations.

8. A system for communicating with a large number of remote satellite locations as recited in claim 1, wherein said allocation table comprises a list of all remote sites from which a packet was received during a last measure increment.

9. A system for communicating with a large number of remote satellite locations as recited in claim 8, wherein said measure increment is one of a multi-slot time period and window.

4. A system for communicating with a large number of remote satellite locations comprising:

a plurality of a first set of remote terminal devices;

a plurality of second remote terminal devices operating in a dedicated mode using the same overlapping channels; and

a hub site which determines threshold criteria for determining when said remote terminal devices are active, and allocates said channels, wherein when said one of said plurality of second remote terminal devices has been sufficiently active during a sliding window, said one of said plurality of second remote terminal devices directly accesses said channels, wherein collisions between inbound packets from different ones of said first and second remote terminal devices are prevented by allocating one of frequency, time slot, and frequency and time slot to said ones of said first and second remote terminal devices that generate the most inbound traffic, wherein when there are more active ones of said first and second remote terminal devices than there are channels, each of said first and second remote terminal devices is allocated a mini-slot, and wherein said first and second remote terminal devices comprise a multi-slot counter, said multi-slot counter in each of said first and second remote terminal devices being synchronized with said hub site and each of said first and second remote terminal devices.

5. A system for communicating with a large number of remote satellite locations comprising:

a plurality of a first set of remote terminal devices;

a plurality of second remote terminal devices operating in a dedicated mode using the same overlapping channels; and

a hub site which determines threshold criteria for determining when said remote terminal devices are active, and allocates said channels, wherein when said one of said plurality of second remote terminal devices has been sufficiently active during a sliding window, said one of said plurality of second remote terminal devices directly accesses said channels, wherein collisions between inbound packets from different ones of said first and second remote terminal devices are prevented by allocating one of frequency, time slot, and frequency and time slot to said ones of said first and second remote terminal devices that generate the most inbound traffic, wherein when there are more active ones of said first and second remote terminal devices than there are channels, each of said first and second remote terminal devices is allocated a mini-slot, wherein said hub site calculates load for each of said first and second remote terminal devices and retains loads in memory, and wherein said load (L_new) for each of said first and second remote terminal devices is calculated according to the following formula;

$L_{\mathrm{new}}={L_{\mathrm{old}}<br><br>\left(1-\mathrm{\tau <br><br>}\right)}^n+\mathrm{\tau <br><br>},$

where τ

is a configurable constant, n is the number of time slots since the last time slot on which a packet was received from a remote terminal device, and L_old is the previous load value of the remote terminal device.

6. A system for communicating with a large number of remote satellite locations comprising:

a plurality of a first set of remote terminal devices;

a plurality of second remote terminal devices operating in a dedicated mode using the same overlapping channels; and

a hub site which determines threshold criteria for determining when said remote terminal devices are active, and allocates said channels, wherein when said one of said plurality of second remote terminal devices has been sufficiently active during a sliding window, said one of said plurality of second remote terminal devices directly accesses said channels, wherein collisions between inbound packets from different ones of said first and second remote terminal devices are prevented by allocating one of frequency, time slot, and frequency and time slot to said ones of said first and second remote terminal devices that generate the most inbound traffic, wherein when there are more active ones of said first and second remote terminal devices than there are channels, each of said first and second remote terminal devices is allocated a mini-slot, wherein said hub site calculates load for each of said first and second remote terminal devices and retains loads in memory, and wherein said load (L_new) each of said first and second remote terminal devices is calculated according to the following formula;

$L_{\mathrm{new}}=L_{\mathrm{old}}*M*{\left(1-1/N\right)}^n+M/N$

where M is a normalizing constant M, N is a time constant, which is the number of time slots in T seconds (where T is a configuration parameter), τ

is 1/N, n is the number of time slots since the last time slot on which a packet was received from a remote terminal device, and L_old is the previous load value of the remote terminal device.

10. A method for communicating with a large number of remote satellite locations, comprising the steps of:

simultaneously communicating in random access mode with a plurality of a first set of remote terminal devices and communicating with a plurality of second remote terminal devices in a dedicated mode using the same overlapping channels;

determining threshold criteria at a hub site to determine when said first and second set of remote terminal devices are active; and

allocating said channels;

calculating load at said hub site for each of said first and second remote terminal devices and retaining loads in memory; and

correlating said loads at said hub site for each of said first and second remote terminal devices with the last time slot in which a burst was last received from each of said first and second remote terminal devices; and

maintaining said correlated loads in an allocation table.

11. A method for communicating with a large number of remote satellite locations as recited in claim 10, wherein said hub site transmits changes to said allocation table to said first and second remote terminal devices.

12. A method for communicating with a large number of remote satellite locations as recited in claim 10, wherein said hub site updates said allocation table every inbound frame.

13. A method for communicating with a large number of remote satellite locations as recited in claim 10, wherein said allocation table comprises information relating to a number of frequencies a remote terminal device is capable of utilizing, a number of mini-slots said remote terminal device may receive, a total number and identification of free inbound ones of said channels and mini-slots, a minimum and assigned maximum load value allocated to each of said first and second remote terminal device, current inbound resources allocated to each of said plurality of first and second remote terminal devices, whether said remote terminal device may become an active site, and whether said remote terminal device has any weighting factors associated with its load calculations.

14. A method for communicating with a large number of remote satellite locations as recited in claim 10, wherein said allocation table comprises a list of all remote sites from which a packet was received during a last measure increment.

15. A method for communicating with a large number of remote satellite locations as recited in claim 14, wherein said measure increment is one of a multi-slot time period and window.

16. A method for communicating with a large number of remote satellite locations, comprising the steps of:

simultaneously communicating in random access mode with a plurality of a first set of remote terminal devices and communicating with a plurality of second remote terminal devices in a dedicated mode using the same overlapping channels;

preventing collisions between inbound packets from different ones of said first and second remote terminal devices by allocating one of frequency, time slot, and frequency and time slot to said ones of said first and second remote terminal devices that generate the most inbound traffic;

allocating a mini-slot to each of said first and second remote terminal devices when there are more active ones of said first and second remote terminal devices than there are channels; and

wherein said first and second remote terminal devices have a multi-slot counter, said multi-slot counter in each of said first and second remote terminal devices synchronizing with said hub site and each of said first and second remote terminal devices.

17. A method for communicating with a large number of remote satellite locations, comprising the steps of:

simultaneously communicating in random access mode with a plurality of a first set of remote terminal devices and communicating with a plurality of second remote terminal devices in a dedicated mode using the same overlapping channels;

determining threshold criteria at a hub site to determine when said first and second set of remote terminal devices are active; and

allocating said channels;

calculating load at said hub site for each of said first and second remote terminal devices and retaining loads in memory, and wherein

said load for each of said first and second remote terminal devices (L_new) is calculated according to the following formula;

$L_{\mathrm{new}}={\left(L_{\mathrm{old}}<br><br>\left(1-\mathrm{\tau <br><br>}\right)\right)}^n+\mathrm{\tau <br><br>}$

where τ

is a configurable constant, n is the number of time slots since the last time slot on which a packet was received from a remote terminal device, and L_old is the previous load value of the remote terminal device.

18. A method for communicating with a large number of remote satellite locations, comprising the steps of:

simultaneously communicating in random access mode with a plurality of a first set of remote terminal devices and communicating with a plurality of second remote terminal devices in a dedicated mode using the same overlapping channels;

determining threshold criteria at a hub site to determine when said first and second set of remote terminal devices are active; and

allocating said channels;

calculating load at said hub site for each of said first and second remote terminal devices and retaining loads in memory, and wherein

said load (L_new) for each of said first and second remote terminal devices is calculated according to the following formula;

$L_{\mathrm{new}}=L_{\mathrm{old}}*M*{\left(1-1/N\right)}^n+M/N$

where M is a normalizing constant M, N is a time constant, which is the number of time slots in T seconds (where T is a configuration parameter), and τ

is 1/N, n is the number of time slots since the last time slot on which a packet was received from a remote terminal device, and L_old is the previous load value of the remote terminal device.