WO2001028130A1

WO2001028130A1 - Dynamic allocation of satellite spectrum resources

Info

Publication number: WO2001028130A1
Application number: PCT/US2000/027374
Authority: WO
Inventors: Darryl Lane Sale; Peter Joseph Armbruster; Victor Hawes Cutler, Jr.
Original assignee: Motorola, Inc.
Priority date: 1999-10-08
Filing date: 2000-10-04
Publication date: 2001-04-19
Also published as: AU7993100A

Abstract

A communications satellite (12) is operated to provide for efficient usage of spectrum resources (111) to support connection and connectionless-oriented service. Each satellite (12) includes a resource allocation manager (109). The resource allocation manager (109), on a request for service, loads a voice service engine (113) or a data service engine (115), depending upon the nature of the received request for service. The resource allocation manager (109) allocates the appropriate spectrum resource (111) to the request for service and a communication path is established.

Description

WHAT IS CLAIMED IS:

1. A method of operating a communication system having a plurality of spectrum resources, comprising the steps of: receiving a request for communication service from a requestor; determining whether said request is for a first type communication or second type communication; loading a first service engine if said request is for said first type communication or loading a second service engine if said request is for said second type communication; allocating a spectrum resource selected from said plurality of spectrum resources to said request; and establishing a communication path utilizing said spectrum resources to service said request.

2. A method in accordance with claim 1 , comprising: providing spectrum resource information for said allocated spectrum resources to said requestor.

3. A method in accordance with claim 1 , comprising: releasing said spectrum resource upon completion of said requested communication service.

4. A method in accordance with claim 1, comprising: determining from said request an amount of said spectrum resource required to service said request.

5. A method in accordance with claim I, wherein: said communication path is a connection-oriented communication path. -11-

6. A method in accordance with claim 1, comprising: determining which of said plurality of spectrum resources is not in use prior to said allocating step.

7. A method in accordance with claim 1, comprising: selecting said plurality of spectrum resources from a first plurality of spectrum resources, said plurality of spectrum resources being those of said first plurality of spectrum resources that are not assigned to other requests for service.

8. A method in accordance with claim 1, comprising: releasing said spectrum resource for reallocation upon completion of said communication service requested.

9. A method in accordance with claim 1, wherein: said first type communication is voice and said second type communication is data.

10. A method in accordance with claim 1 , wherein: at least a portion of said method is carried out aboard a satellite vehicle.

11. A method in accordance with claim 1 , wherein: said spectrum resources include a plurality of channels.

12. A method in accordance with claim 11 , wherein: said allocation step includes determining a number of changes for said request.

13. A method in accordance with claim 11, comprising: determining if said number of channels exceeds a first number of channels assigned to said requestor. -12-

14. A method in accordance with claim 13, comprising: allocating additional channels to service said request if said number exceeds said first number.

15. A satellite for use in a satellite communication system to provide voice and data communication, said satellite comprising: a plurality of spectrum resources; at least one processor monitoring for a request for communication service; said at least one processor operable to identify requests for communication service for voice or data communication; memory containing a voice service engine and a data service engine; a resource allocation manager, said resource allocation manager loading said voice service engine if said request is identified as being for voice communication, or loading said data service engine if said request is identified as being for data communication; said resource allocation manager allocating a spectrum resource selected from said plurality of spectrum resources to said request for service; and said at least one processor establishing a communication path utilizing said spectrum resource to service said request.

16. A satellite in accordance with claim 15, wherein: said at least one processor is operable to release said allocated spectrum resource upon completion of said voice or data communication.

17. A satellite in accordance with claim 15, wherein: said at least one processor is operable to determine from said request, the amount of said spectrum resource required to service said request.

18. A satellite in accordance with claim 15, wherein: said at least one processor is operable to determine which of said plurality of spectrum resources is not in use prior to said allocation of said spectrum resource. -13-

19. A satellite in accordance with claim 15, wherein: said at least one processor is operable to select said plurality of spectrum resources from a first plurality of spectrum resources, said plurality of spectrum resources being those of said first plurality of spectrum resources that are not assigned to other requests for service.

20. A satellite in accordance with claim 15, wherein: said at least one processor is operable to release said spectrum resource for reallocation upon completion of said communication service requested.

-1- DYNAMIC ALLOCATION OF SATELLITE SPECTRUM RESOURCES

FIELD OF THE INVENTION

The present invention relates generally to satellite-based communications, and, more particularly, to dynamic allocation of spectrum resources for voice and data communication.

BACKGROUND OF THE INVENTION

Wireless communications utilize spectrum resources for each user's communication channel. Two general types of communications services are typically utilized. Connectionless services are typically utilized for data communication, and wireless connection-oriented services are typically utilized for voice communication. Connectionless services provide the convenience of not having to establish an independent or dedicated connection from source to destination to send short messages. However, connectionless service is typically not used for voice communication since the quality of connectionless service falls short of that necessary for the continuous use nature of voice communication.

Existing satellite communications systems provide connection-oriented services for both voice and data service requests. The same communication setup procedure is used for both data and voice, which results in relatively long setup times for data transmissions and, therefore, inefficient use of spectrum resources. Typically, voice communications comprise the majority of traffic, so a connection oriented protocol is used to maintain high quality. Since data is an ancillary service, it uses the connection-oriented protocol, even though a connectionless protocol is more suitable. The connectionless protocol is more suitable because data service is generally less delay sensitive and is more bursty in nature and, therefore, does not require high quality service, which connection- oriented protocols provide.

Because of the limited spectrum resources available on a communications satellite, it is desirable that an efficient method for the allocation of spectrum resources between connection oriented and connectionless services is used. -2- BRIEF DESCRIPTION OF DRAWINGS

The invention will be better understood from a reading of the following detailed description of an embodiment of the invention, taken in conjunction with the drawings in which like reference designators are used to identify like elements in the various drawing figures, and in which:

FIG. 1 is a highly simplified diagram of a satellite-based communication system of which the present invention may form a portion;

FIG. 2 depicts communication paths between a satellite, voice subscriber unit, data subscriber unit and gateway, in accordance with an embodiment of the present invention;

FIG. 3 is a functional block diagram of a portion of one of the satellites shown in FIG. 1;

FIG. 4 is a flowchart of service engine instantiations for request of either voice or data services;

FIG. 5 depicts communication paths between a channel allocation manager to voice and data service engines in order to allocate resources to the various service engines as needed; and

FIG. 6 is a flow chart of the operation of a system in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention presents an efficient method for providing both voice and data services in satellite applications. A communication satellite in accordance with the invention provides a connection oriented service for voice communication and a connectionless service for data communication, with dynamic load based selection of spectrum resources. Spectrum resources are not dedicated for voice and data, but rather, a dynamic allocation is made of the resources based upon current demand and need. A service request results in a service-specific protocol engine being loaded into memory.

The data service engine protocol allows for sharing the radio frequency medium between multiple data users via a connectionless, multiple access protocol, since small data transfers can be conducted relatively quickly. This engine controls -3- the communication setup and data transfer processes. Each engine requests bandwidth from a channel assignment process, which allocates bandwidth based on the service being provided. Only the amount of bandwidth needed for the service is allocated. The satellite dynamically allocates its resources autonomously or under ground station control. The dynamic allocation is performed by service-specific protocol engines and a demand-based channel assignment algorithm.

A satellite system in accordance with the invention optimizes RF resource efficiency to support a larger number of connections while providing higher rate data services. Service-specific protocol engines and demand-based channel assignment are utilized.

FIG. I illustrates a highly simplified diagram of satellite-based communication system 10, dispersed over and surrounding the earth through use of orbiting satellites 12 occupying orbits 14. The present invention is particularly well suited for communication systems including satellites in low earth orbit (LEO) and medium earth orbit (MEO). Additionally, it is applicable to orbits having any angle of inclination (e.g., polar, equatorial or another orbital pattern).

Communication system 10 uses six polar orbits 14, with each orbit 14 having eleven satellites 12 for a total of sixty-six satellites 12. Although this is preferred, it is not essential, because more or fewer satellites, or more or fewer orbits, may be used. While the present invention is advantageously employed when a large number of satellites are being used, it is also applicable with as few as one satellite. For clarity, FIG. 1 illustrates only a few satellites 12 of the constellation.

In the illustrative embodiment of FIG. 1 , each orbit 14 encircles the earth at an altitude of approximately 785 km, although higher or lower orbital altitudes may be usefully employed. Due to the relatively low orbits of satellites 12, substantially line-of-sight electromagnetic (e.g., radio, light, etc.) transmission from any one satellites 12 or reception of signals by any one of satellites 12 covers a relatively small area of the earth at any instant. For the example shown, satellites 12 travel with respect to the earth at approximately 25,000 km/hr, allowing one of satellites 12 to be visible to a terrestrial station or radio communication voice subscriber units (VSUs) 26 for a period of approximately nine minutes.

Satellites 12 communicate with terrestrial stations that may include some number of VSUs 26 and earth terminals (ETs) 24 connected to system control -4- segment (SCS) 28. ETs 24 may also be connected to gateways (GWs) 22 that provide access to a public switched telephone network (PSTN) or other communications facilities. Only one each of GWs 22, SCSs 28 and VSUs 26 are shown in FIG. 1 for clarity and ease of understanding. ETs 24 may be co-located with, or separate from, SCS 28 or GWs 22. ETs 24 associated with SCSs 28 receive data describing the status of satellites 12 and GWs 22, and relay packets of control information. ETs 24 associated with GWs 22 primarily receive and relay packets relating to communications in progress from/to VSUs 26 and satellites 12. VSUs 26 may be located anywhere on the surface of the earth or in the atmosphere above the earth. VSUs 26 are preferably communications devices capable of transmitting data to and receiving data from satellites 12. By way of example, VSUs 26 may be hand-held, portable cellular telephones adapted to communicate with satellites 12. Ordinarily, VSUs 26 need not perform any control functions for communication system 10. Communication system 10 may accommodate any number, potentially in the millions, of VSUs 26. In the preferred embodiments of the present invention, VSUs 26 communicate with nearby satellites 12 via subscriber links 16. Links 16 encompass a limited portion of the electromagnetic spectrum that is divided into numerous channels. Links 16 are preferably combinations of L-Band and/or K-Band frequency channels and may encompass Frequency Division Multiple Access (FDMA) and/or Time Division Multiple Access (TDMA) and/or Code Division Multiple Access (CDMA) communications or combinations thereof. At a minimum, satellites 12 regularly transmit over one or more broadcast channels 18. VSUs 26 synchronize to broadcast channels 18 and monitor broadcast channels 18 to detect data messages which may be addressed to them. VSUs 26 may transmit messages to satellites 12 over one or more acquisition channels 19. Broadcast channels 18 and acquisition channels 19 are not dedicated to any one of VSUs 26, but are shared by all VSUs 26 currently within view of one of satellites 12.

However, traffic channels 17 are two-way channels that are assigned to a particular one of VSUs 26 by satellites 12 from time to time. In the preferred embodiments of the present invention, a digital format is used to communicate data over channels 17-19, and traffic channels 17 support real-time communications. At least one traffic channel 17 is assigned for each communication, and each traffic channel 17 has sufficient bandwidth to support, at a minimum, a two-way voice -5- conversation. To support real-time communications, a time division multiple access (TDMA) scheme is desirably used to divide time into frames, preferably in the 10-90 millisecond range. Particular traffic channels 17 are assigned particular transmit and receive time-slots, preferably having durations in the 3-10 millisecond range, within each frame. Analog audio signals are digitized so that an entire frame's signal is transmitted or received in a single, short, high-speed burst during an allotted time-slot. Preferably, each of satellites 12 support up to one thousand or more traffic channels 17, so that each of satellites 12 may simultaneously service a number of independent communications. Those skilled in the art, however, will recognize that traffic channels may be formed without this time-slot structure and that methods that do not require digitizing analog voice signals may be employed. The precise method used to form the channels and process voice communication is not important to this invention.

Satellites 12 communicate with other nearby satellites 12 through crosslinks 23. Thus, communication from one of VSUs 26 located at any point on or near the surface of the earth may be routed through the constellation of satellites 12 to within range of substantially any other point on the surface of the earth. A communication may be routed to one of VSUs 26 on or near the surface of the earth from one of satellites 12 using subscriber link 16. Alternatively, a communication may be routed to or from any of many ETs 24, of which FIG. 1 shows only two, through earth links 15. ETs 24 are usually distributed over the surface of the earth in accordance with geopolitical boundaries. In the preferred embodiments, each of satellites 12 may communicate with up to four ETs 24 and over one thousand VSUs 26 at any given instant. SCS 28 monitors the health and status of system communication nodes (e.g.,

GWs 22, ETs 24 and satellites 12) and desirably manages operations of communication system 10. One or more ETs 24 provide the primary communications interface between SCS 28 and satellites 12. ETs 24 include antennae and RF transceivers and, preferably, perform telemetry, tracking and control functions for the constellation of satellites 12.

GWs 22 may perform communication processing functions in conjunction with satellites 12, or GWs 22 may exclusively handle communication processing and allocation of communication handling capacity within communications system 10. Diverse terrestrial-based communications systems, such as the PSTN, may access -6- communications system 10 through GWs 22.

With the example constellation of sixty-six satellites 12, at least one of satellites 12 is within view of each point on the earth's surface at all times, resulting in full coverage of the earth's surface. Any of satellites 12 may be in direct or indirect data communication with any of VSUs 26 or ETs 24 at any time by routing data through the constellation of satellites 12. Accordingly, communication system 10 may establish a communication path for relaying data through the constellation of satellites 12 between any two VSUs 26, between SCS 28 and GWs 22, between any two GWs 22 or between VSUs 26 and GWs 22. The present invention is also applicable to satellite constellations where full coverage of the earth is not achieved (i.e., where there are "holes" in the communications coverage provided by the constellation) and constellations where plural coverage of portions of the earth occur (i.e., more than one satellite is in view of a point on the earth's surface). In general terms, communications system 10 may be viewed as a network of nodes. Each of satellites 12, GWs 22, and VSUs 26 represent a node of communications system 10. All nodes of communications system 10 are or may be in data communication with other nodes of communications system 10 through communication links 15, 16, and/or 23. In addition, all nodes of communications system 10 are or may be in data communication with other telephonic devices dispersed throughout the world through PSTNs and/or conventional terrestrial cellular telephone devices coupled to the PSTN through conventional terrestrial base stations. In addition to VSUs 26, communications system 10 may include digital subscriber units (DSUs) 31. FIG. 2 shows typical communication paths between a satellite 12, VSU 26,

DSU 31, and GW 22 in accordance with an embodiment of the present invention. A user having a VSU 26 initiates a communication session by monitoring broadcast channels 18 to determine, first, if communication services are available and, second, the spectrum and time-slot of acquisition channels 19. VSU 26 then proceeds to refine communication parameters, such as timing parameters inherent in synchronous TDMA communication systems and transmission frequency offsets injected by Doppler frequencies introduced by high-velocity orbiting base stations such as satellites 12. Satellite 12 evaluates the communication parameters employed by VSU 26 and provides feedback for refining both timing and frequency -7- parameters in broadcast channel 18. VSU 26 adjusts subsequent transmissions in acquisition channel 19 (FIG. 1) until satellite 12 determines that communication parameters are sufficiently refined to non-interferingly operate in a narrowband traffic channel 17. Satellite 12, through crosslinks 23 and earthlinks 15, cooperatively with GW 22, establishes a connection from VSU 26 to the terminating party as requested by the user of VSU 26. This connection process from point-to- point requires that spectrum resources be dedicated from VSU 26 to a terminating party for the duration of a communication session.

As illustrated in FIG. 3, satellites 12 include an onboard processing unit 107. Onboard processing unit 107 includes a resource allocation manager 109. As satellites 12 receive service requests for data communication from one of DSUs 31 and/or voice communications from one of VSUs 26, resource allocation manager 109 assigns spectrum resources in a manner which maximizes efficient use of the limited resources available on board satellites 12. As requests for service are received, resource allocation manager 109 identifies voice requests to be processed by voice service engines 113 stored in memory 114 and identifies requests for data services to be processed by data service engines 115 stored in memory 116. Once resource allocation manager 109 identifies a request as one for voice service, it establishes a connection-oriented service via a spectrum resource assignment. Spectrum resources 111 are indicated by a matrix representation. Likewise, a connectionless service is established by resource allocation manager 109 when it identifies a request for data services. The connectionless service is provided by assignment of spectrum resources as 111. It will be appreciated by those skilled in the art that existing satellite systems may be operated in conformance with the invention by uploading software into the satellite processing units which provide for resource allocation management. In contrast to prior art systems, the onboard processing unit, when programmed in accordance with the present invention, provides for dynamic resource allocation. After a request for service is identified, the appropriate service engine is loaded and an allocation is made for spectrum resources.

FIG. 4 is a flowchart of service engine instantiations for channel allocation. Initially, a service request is received by onboard processing unit 107 for either voice or data service. When the service type has been determined, the appropriate service engine 113 or 115 will be loaded and executed. After the loading and -8- execution of the service engine 113 or 115, the engine identity or "handle" is passed to a resource allocation manager 109, which maximizes efficiency of the limited channel resources.

As each request for service is received at step 401, a determination is made at step 403 as to whether the request is for voice service. If the request is for voice service, voice service engine 113 is loaded as indicated at step 405. After voice service engine 113 is loaded, voice service engine 113 is executed as indicated at step 407. After voice service engine 113 is executed, voice service engine 113 is passed to resource allocation manager 109 as indicated at step 409. If, however, at step 403, it is determined that the request for service is not a request for voice service, data service engine 115 is loaded as indicated at step 411. After data service engine 115 is executed as indicated at step 413, data service engine 115 is passed to resource allocation manager 109 at step 409. Voice services require higher quality connection-oriented resources, whereas data services can tolerate connectionless resources.

In a TDMA-type system, resource allocation manager 109 of FIG. 3 includes a channel allocation manager to allocate channels.

FIG. 5 is a functional illustration of how resource allocation manager 109 communicates with voice service engines 1 3 and data service engines 115 to allocate spectrum resources 111 to the respective engines 113, 115 as needed. Voice service engines 113 require higher quality resources of the connection- oriented services. Data service engines 115 require only the resources of connectionless service, thereby reserving other resources for other users. Resource allocation manager 109 assigns channels to voice service engines 113 and data service engines 115 as needed. The assignment of voice service engines 113 are connection-oriented so that the connection is maintained for the duration of the communication. In contrast, data service engines 115 are assigned channels on a connectionless based protocol.

FIG. 6 is a flow chart setting forth the interaction between channel allocation and service engines. Initially, at step 601, the number of channels requested from a subscriber or originator of a request for service is determined. Once this number has been ascertained, it must be determined whether the requested number of channels exceeds current allocation at step 603. If the requested number of channels exceeds the current allocation, additional channels from spectrum -9- resources 111 are requested by resource allocation manager 109 at step 605. The subscriber is reconfigured at step 607 to use the provided channels.

If the requested number of channels does not exceed the current channel allocation at step 603, an additional determination is made at step 609 as to whether the requested number of channels equals the current allocation. If the requested number of channels equals the current channel allocation, there will be no change in the number of channels assigned to the subscriber as indicated at step 611. However, if the requested number of channels does not equal the current allocation, there must be more channels provided than necessary, which will require a reduction in the number of required channels for maximum efficiency. At this point, the subscriber is reconfigured to release channels at step 613. The released channels will be returned to the channel allocation manager for other use at step 615.

The present invention has been described above with reference to preferred embodiments. However, those skilled in the art will recognize that changes and modifications may be made in these preferred embodiments without departing from the spirit and scope of the present invention. For example, base stations need not be orbiting satellites but instead may be terrestrial base stations employing substantially the same procedures as discussed above. Others may devise alternate procedures to accomplish substantially the same functions as those described herein. These and other changes and modifications which are obvious to those skilled in the art are intended to be included within the scope of the present invention.