Method for handover between ATC and satellite component of an integrated MSS/ATC system

Abstract

A communications system comprising a first transceiver and a second transceiver, which system employs a device that measures power over a frequency band from sources other than those monitoring downlink radiation received at a radio terminal from the satellite, and a controller that receives these power measurements to determine on which frequency channel within a band a transmitter is to transmit.

Description

V. BRIEF DESCRIPTION OF THE DRAWINGS

The above set forth and other features of the invention are made more apparent in the ensuing Detailed Description of the Invention when read in conjunction with the attached drawings, wherein:

FIG. 1 illustrates an integrated MSS/ATC.

FIG. 2 illustrates an MSS/ATC system in a LEO constellation.

FIG. 3 illustrates improvement in MSS area.

FIG. 4A illustrates a transmission frequency determined for transceiver 2 (100) for transmission to transceiver 1 (200).

FIG. 4B illustrates the determination of a transmission frequency for transceiver 1 (200) for transmission to transceiver 2 (100).

VI. DETAILED DESCRIPTION OF THE INVENTION

The system of the instant invention, which is set out above in precise and accurate terms so as to enable one of ordinary skill in the art to practice same, will be better understood with reference to the following examples:

Example 1

An example application of FIG. 4A is one where transceiver 1 is at the gateway of a satellite system such as the Globalstar® system, and transceiver 2 in the figure is at the user terminal of an MSS user. Here the gateway transceiver measures, with a spectrum analyzer, the power levels in each frequency channel that it is receiving. These measurements, or a summary of these measurements, are then sent to the user terminal (transceiver 2) which then decides to transmit on a frequency that has the least interference power as reported by the gateway in its summary of measurements. In this way, the user terminal is able to transmit with low power since it is using a relatively clear channel to transmit on. When applied to multiple user terminals, this results in all these users from transmitting at the lowest power in the best channels; i.e., the ones with the least interference.

Example 2

Another application of FIG. 4, which is described in FIG. 4B, would be similar to Example 1, with the difference that in this case the gateway makes the decision itself on what frequency is best for the user terminal to transmit on and merely sends this information on a control channel to the user terminal.

Example 3

Another application of FIG. 4B is similar to Example 2 above in that the gateway measures power or signal-to-noise ratio or bit-error-rate in different frequency channels, decides that all frequency channels are running close to their capacity limit, and then directs the user terminal (transceiver 2) to go to the ATC component rather than the satellite component. In a system like Globalstar®, this is possible because the radiation in all frequencies, ATC or not, from user terminals in a satellite beam, are transmitted through the satellite and received at the gateway. Thus, the gateway is in a good position to look at all the interference presented from all sources (ATC as well as MSS) and determine which frequency, if any, is available for MSS and, if none is available, to direct the user terminal to switch to ATC mode. Likewise, when the gateway senses that any one of the channels becomes available due to some of its traffic being decreased, it can send a control message to the user terminal directing it to go from ATC mode to satellite (MSS) mode.

FIG. 1 shows an integrated MSS/ATC system conceptually. In this system, a user terminal can be operated in either ATC mode or MSS mode. In the Figure, user terminal (1) is shown as operating in ATC mode; i.e., communicating to and from an ATC base station (2). User terminal (3) is shown as operating in MSS mode. In this mode, the user terminal transmits to and receives from a gateway (5) via satellite (4). Satellite (4) may be a GEO satellite, or one of a constellation of GEO or MEO or LEO satellites. The ATC base station potentially interferes with the MSS downlink/uplink inside the ATC coverage area (6).

FIG. 2 shows an example of an MSS/ATC system that uses a LEO constellation of satellites, some of which are shown as (11), (12), (13), (14), (15), (16). In this figure, the darker shaded zones (e.g., zone 17) show normal full-spectrum MSS beams that are using all the MSS frequency channels available. The lighter shaded zones (e.g., zone 18) show regions where worst case ATC frequency interference causes impaired MSS service in frequencies used for ATC.

FIG. 3 shows the same regions, but now with an improvement in MSS area by assigning two separate frequencies dynamically to MSS and ATC segments. In this figure, zones 20 use selected MSS frequencies via selected satellites. Separate ATC frequencies are designated by dotted zones 30.

FIG. 4A shows a transmission frequency determined for transceiver 2 (100) for transmission to transceiver 1 (200). In this case, receiver 1 makes measurements on the signal it receives in various frequency channels from transmitter 2 and sends these measurements to receiver 2 which decides what frequency is best (least interference) for transmitter 2 to transmit on.

FIG. 4B shows the determination of a transmission frequency for transceiver 1 (200) for transmission to transceiver 2 (100). Here receiver 2 makes measurements on the signal it receives in various frequency channels from transmitter 1, and uses these measurements to decide what frequency is best (least interference) for transmitter 1 to transmit on, and then sends this information about this best frequency to transceiver 1.

While the present invention has been particularly described with respect to certain components in its preferred embodiment, it will be understood that the invention is not limited to these particular components described in the preferred embodiments, or the sequence in employing or methods of processing the components. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention defined by the appended claims.

In addition, other components may be employed in the system of the instant invention as claimed as well as variations and alternatives to the components disclosed and claimed with similar results with regard to the operation and function of the system of the instant invention. In particular, the scope of the invention is intended to include, for example, GEO satellites equipped with dynamic beam forming which further enhances the performance of the system, or equipped with a Digital proCessing Router (DCR) or employing virtual gateway techniques as set out in U.S. Pat. No. 6,735,440, especially in FIGS. 15B-C.

Claims

1. A communication system comprising: at least a first transceiver including at least a first receiver and at least a first transmitter;at least a second transceiver including at least a second receiver and at least a second transmitter;a device that measures power over a frequency band from sources other than those monitoring downlink radiation received at a radio terminal from a satellite; anda controller that receives said measurements to determine in which frequency channel within a band a transmitter is to transmit.

2. The communication system as defined in claim 1 wherein the power measurements are transmitted over a control channel.

3. A communication system as defined in claim 1 wherein signal to noise ratio is measured instead of power.

4. The communication system as defined in claim 1 wherein said first transceiver communicates with a plurality of a second set of transceivers.

5. The communication system as defined in claim 1 wherein the at least first transceiver measures the interference or power from each transceiver in the at least second set of transceivers.

6. The communication system as defined in claim 1 wherein said at least second transceiver transmits the said frequency channel to said at least first transceiver to determine frequency for said first transceiver to transmit to said second transceiver.

7. A communication system comprising: at least a first transceiver including at least a first receiver and at least a first transmitter;at least a second transceiver including at least a second receiver and at least a second transmitter;said at least first transceiver communicating to said at least second transceiver power measurements over a frequency band employing power measurements from sources other than those monitoring downlink radiation received at a radio terminal from a satellite; anda controller in said at least second transceiver that receives said measurements to determine on which frequency channel within a band the at least second transmitter is to transmit.

8. A method for handing over wireless communications in a satellite communications system, the satellite communications system comprising at least one satellite that is configured to wirelessly communicate with at least one radio terminal in a satellite coverage area over a satellite frequency band and an ancillary terrestrial component that is configured to wirelessly communicate with at least one radio terminal in the satellite coverage area over at least some of the satellite frequency band, to thereby terrestrially reuse at least some of the satellite frequency band, the handover method comprising: handing over wireless communications with a radio terminal from the ancillary terrestrial component to the satellite component by determining which frequencies are more suitable or receive less interference in a band by measuring the interference levels at each frequency at a gateway.

9. A method for handing over wireless communications in a satellite communications system, the satellite communications system comprising at least one satellite that is configured to wirelessly communicate with at least one radio terminal in a satellite coverage area over a satellite frequency band and an ancillary terrestrial component that is configured to wirelessly communicate with at least one said radio terminal in the satellite coverage area over at least some of the satellite frequency band, to thereby terrestrially reuse at least some of the satellite frequency band, the handover method comprising: handing over wireless communications with a radio terminal from the satellite component to the ancillary terrestrial component by determining which frequencies are more suitable or receive less interference in a band by measuring the interference levels at each frequency at a gateway.

10. The method as defined in claim 8 wherein handing over comprises handing over wireless communications with the radio terminal from the ancillary terrestrial component to the satellite component when the radio terminal transmit power exceeds a threshold, an aggregate radio terminal interference exceeds a limit and the satellite component signal quality exceeds a threshold, even though the radio terminal is able to wirelessly communicate with the ancillary terrestrial component.

11. The method as defined in claim 8 wherein handing over comprises handing over wireless communications with the radio terminal from the ancillary terrestrial component to the satellite component if the radio terminal transmit power exceeds a threshold, the satellite component signal quality exceeds a threshold and the radio terminal is at least a predetermined distance away from the ancillary terrestrial component when the radio terminal is able to wirelessly communicate with the ancillary terrestrial component.

12. A communication system comprising: at least a first transceiver including at least a first receiver and at least a first transmitter; at least a second transceiver including at least a second receiver and at least a second transmitter;said at least second transceiver measures the power over a frequency band;a controller in said at least second transceiver that receives said measurements to determine which frequency channel within a band the at least first said transmitter is to transmit on; andsaid at least second transmitter transmits the said frequency channel information to said at least first transceiver.

13. The communication system as defined in claim 12 wherein said at least second transceiver communicates with a plurality of at least a first set of transceivers.

14. The communication system as defined in claim 12 wherein the at least second transceiver measures the interference or power from each transceiver in the at least first set of transceivers.