Abstract:
A system includes a method for automatically reconfiguring a satellite network with a high accuracy in order to enable system reconfiguration very quickly and at a low cost. The system employs a single axis steering mechanism.

Description:
RELATED APPLICATIONS 
       [0001]    The present application is a non-provisional of U.S. Provisional application Ser. No. 61/029,716, filed Feb. 19, 2008, entitled “Satellite Redundancy for Critical Applications,” the contents of which is incorporated herein by reference in its entirety for all purposes. 
     
    
     FIELD 
       [0002]    The invention relates to providing suitable satellite reconfiguration facilities for automatically repositioning a VSAT terminal at a low cost upon a change of satellite. 
       BACKGROUND 
       [0003]    In satellite networks, the remote satellite terminals are usually installed using a fixed satellite dish antenna aligned towards the applicable satellite. If another satellite has to be used for whatever reason, the antenna of each such remote satellite terminal has to be realigned towards the new satellite. As realignment requires each such site to be visited, the process of transferring the entire network to the new satellite may require expensive logistics and considerable time (weeks or even months) to implement even in medium-sized networks (hundreds of remote satellite terminals). That is all the more troublesome for large networks (many thousands of remote satellite terminals) and/or for networks with terminals located in remote and difficult-to-access locations. During the time period of the reconfiguration, remote terminal functionality may be disabled, causing service discontinuity. 
       BRIEF SUMMARY 
       [0004]    Satellite diversity may enable a remote terminal to use another satellite on a different orbital position without a need for manually re-pointing the antenna. Such capability may be used in several scenarios. One scenario may include recovering from unexpected problems with the satellite itself, such as malfunction of the satellite or even a complete satellite loss. Another scenario may include a planned transfer of the network to a different satellite. Such transfer may be driven from a need to increase the total space segment used by the network (e.g. because of network growth) where that might not be possible over the existing satellite (already fully allocated). Another drive for such transfer may be lowering operation cost, if less expensive space segment can be rented on a different satellite. 
         [0005]    Currently, existing products allowing antenna movement over the geostationary orbital arc are used only for receive-only antennas and even then typically only for automated setup scenarios. The invention described herein suggests capabilities for two-way communication systems that may dynamically reconfigure themselves for additional satellite locations. 
         [0006]    Each remote site may include an automatic motorized apparatus and a controlling unit. The apparatus may be configured to rotate the antenna towards a pre-defined active satellite. The control unit, which may be incorporated into the remote terminal or externally implemented, may be used both for translating the remote terminal&#39;s commands to DisEqC protocol and for enabling an end-user to locally initiate a satellite switchover. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  shows a satellite system having a hub and a plurality of remote terminals in accordance with the aspects of the invention. 
           [0008]      FIG. 2  shows an embodiment of the invention which may include a VSAT, an externally connected indoor control unit and a polar mount apparatus. 
           [0009]      FIG. 3  shows an embodiment of the invention including an additional external control device connected to an auxiliary control interface of the indoor control unit. 
           [0010]      FIG. 4  shows an embodiment of an indoor control unit as a unit externally connected to the VSAT. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]      FIG. 1  shows a satellite system  1 , having a hub  2  and a plurality of remote terminals  3  to  5  in accordance with the aspects of the invention. 
         [0012]      FIG. 2  shows an embodiment of the invention, including a very small aperture terminal (VSAT)  110 , an externally connected indoor control unit (ICU)  120  and a polar mount apparatus  130  that may be mounted on or otherwise integrated with the antenna. Other embodiments of this invention may integrate the functionality of indoor control unit  120  into VSAT  110 . 
         [0013]    VSAT  110  may be used for two-way communication over satellite. VSAT  110  may be connected to an indoor control unit via a communication channel (e.g. RS-232 serial channel, USB bus, or similar communication standard) for the purpose of sending commands and receiving telemetry. ICU  120  may be a device, which communicates satellite positions using DisEqC (digital satellite equipment control) to the polar mount  130 . In some embodiments, ICU  120  may also include a suitable mechanism (e.g. control push-buttons) allowing an operator to manually initiate a procedure for repositioning the antenna in order to enable communication via a different satellite. Polar mount  130  may be an automatic motorized apparatus for rotating the satellite dish around a single axis. 
         [0014]      FIG. 3  shows an embodiment of the invention, further including an additional external control device  200  connected to an auxiliary control interface of ICU  120 . External control device  200  may be a personal computer, a laptop computer, PDA or any other device with proper communication port and software for sending and receiving commands and telemetry to and from the ICU respectively. ICU  120  may include a mechanism, which enables external control device  200  to monitor the exchange of information between VSAT  110  and ICU  120 . Furthermore, ICU  120  may include a mechanism for suppressing any command received via the auxiliary control interface while executing a command received through the main control interface. 
         [0015]      FIG. 4  shows an embodiment of ICU  120  as a unit externally connected to a VSAT. In such embodiment, ICU  120  may contain a micro-controller  121 , a communication adaptor  122  (which may be integrated into micro-controller  121 ) for supporting a main and an auxiliary control channels, and a universal LNB driver  122 . In addition, ICU  120  may also contain an option for manual control  124 , allowing manual selection of pre-determined antenna positions, and local indicators  125  for purposes such as, but not limited to, indicating which of the pre-defined position is currently in effect and/or that the antenna is currently on the move. The implementation of manual control and local indicators may vary considerably while maintaining similar functionality. 
         [0016]    In a satellite communication system having a hub and plurality of remote terminals, two-way communication may be supported. A remote terminal may transmit towards the hub and receive information from the hub via the satellite. In addition, a remote terminal may send information to another remote terminal via the hub. In some embodiments, a remote terminal equipped with a suitable receiver may receive information directly from another terminal in mesh connectivity, i.e. without information being routed via the hub and/or processed by it. 
         [0017]    In exemplary satellite communication systems, each remote terminal may include an indoor unit (referred to herein as VSAT), which processes the information sent and received by the remote terminal, a satellite dish antenna, a satellite transmitter and a low-noise block amplifier (LNB), the last two preferably being mounted on the antenna and connected to the indoor unit with appropriate cables. In most cases, the dish antenna lacks any automatic alignment capabilities. The installation procedure of such remote terminal often includes a step of aligning the antenna towards the position of the applicable satellite in the sky. Once installation is complete, any transfer to another satellite requires manual realignment of the antenna, which means revisiting the site where the remote terminal is installed. 
         [0018]    Except maybe for the cases where an antenna has to be realigned because of extreme wind gusts or because of the need to relocate the antenna (e.g. as the line of site towards the satellite becomes partially or entirely blocked by new buildings or other interfering objects), the cost and logistics of revisiting sites for antenna realignment may be saved by installing dish antennas with automatic alignment capabilities. While antennas with alignment capabilities over both azimuth and elevation are quite expensive, much less expensive devices, e.g. polar mounts, are capable of rotating a dish antenna over a single axis. These mountings are sometimes used for one-way (receive only) applications. 
         [0019]    By using a polar mount device in a two-way communication system, a two-way remote terminal may support automatic realignment of its dish antenna. As polar mount devices may be very accurate, a proper installation and alignment of the antenna towards the geostationary arc not only insures proper reception at every position along the arc but also sufficient transmission conditions, such as cross-polarization isolation. 
         [0020]    By aligning the antenna towards the geostationary arc, the remote terminal may use any geostationary satellite located within the rotation angle of the device (often up to around 75 degrees off the center position). In most cases, the use of alternate satellites may be limited to those which support same frequency band and polarity (e.g. vertical or horizontal), as the mounting of the satellite transmitter and the low-noise block amplifier remains unchanged. However, using different frequency bands might be possible through use of much more expensive multi-band equipment (both for reception and transmission). In addition, some universal LNB types may detect the supply voltage level (e.g. 13 volts versus 18 volts) in order to control reception polarity. Similar mechanisms may exist for satellite transmitters as well, therefore allowing two-way communication over different satellites with practically no polarity limitation. 
         [0021]    In embodiments of the invention, in addition to the VSAT and the polar mount, the remote terminal site may also include an indoor control unit (ICU) that may be connected between the VSAT and the polar mount. Such stand-alone ICU may be used in order to introduce satellite diversity capabilities to remote terminals, which do not internally support the necessary functionality for realizing such capabilities. In other embodiments, the functionality of such ICU may be embedded and/or integrated into the VSAT. 
         [0022]    The main function of such ICU may be the transmitting of commands in DisEqC (Digital Satellite Equipment Control) protocol, or any other suitable protocol, towards the polar mount over the RF cable, which may be configured to connect the LNB to the VSAT indoor unit. In these embodiments, this cable carries DC power from the indoor unit to the LNB and RF signal from the LNB to the indoor unit. The commands towards the polar mount may be modulated over a carrier signal (e.g. 22 KHz). The polar mount may detect this modulated signal, demodulate the commands and respond to them, e.g. by rotating the antenna and aligning it at a new position. 
         [0023]    The ICU may transmit towards the polar mount only those commands received from the VSAT, which are properly formatted and contain an appropriate id field. In order to simplify the ICU, it is possible to use polar mount models supporting a subset of the DisEqC v1.2 protocol named USALS (Universal Satellite Automatic Location System), which is unofficially known also as DisEqC v1.3. The USALS protocol utilizes a single command out of the DisEqC v1.2 protocol for driving the polar mount motor to a specified angular position (in degrees). 
         [0024]    In another embodiment of this invention, the VSAT may measure the level of the received forward link signal and transmit this measurement to the ICU, either as a raw measurement or as an indication calculated from that measurement. The ICU may then transmit this indication to the polar mount. This indication may then be used by the polar mount for adjusting its alignment about the nominal position, maximizing the received signal level and improving the system&#39;s pointing accuracy. During installation, received signal level may be indicated visually, acoustically and/or by other means, providing an installer with a feedback on pointing accuracy and assisting him in the alignment process. 
         [0025]    When a switchover to another satellite is initiated, the VSAT may obtain the location of the new satellite in several ways. The position may be given as part of the command that triggers the switchover procedure. In other embodiments, the position may be part of the VSAT configuration or part of its installation parameters and therefore may be retrieved from local memory. Regardless, the VSAT may then send the ICU the angle relative to a reference point at which the antenna should be rotated. The ICU may then translate this information to the DisEqC protocol and send it to the polar mount&#39;s motorized back structure over the reception coax cable. Once the antenna completes its rotation, the VSAT may program parameters of a new forward signal into its reception hardware and reestablish connectivity with the hub without any intervention from the VSAT end-user. 
         [0026]    In reference to the external ICU embodiment, such ICU may include a micro-controller, communication ports (which may be integrated within said micro-controller), a universal LNB driver, controls for manual initiation of switchover procedure, and some indicators or a display for providing indication regarding the current status of the unit to any person at the site. The universal LNB driver may control the power supply voltage to the LNB for the purpose of signaling the desired polarity. In other embodiments, such capability may be used for accommodating long cable length installations. 
         [0027]    The VSAT may communicate with the ICU via a communication channel such as but not limited to a serial channel. The physical signals of the serial channel may follow the RS-232 or other suitable bus standard. The VSAT may generate commands, which may include parameters. The VSAT may then sequentially send these commands over the communication channel in order to control and monitor the ICU. The protocol between the VSAT and the ICU may be based on a structural format and may contain an ICU identifier, a command code, one or more data elements and an error detection code (e.g. a 16-bit checksum). 
         [0028]    The ICU may interrupt the VSAT via the communication channel. In embodiments where the communication channel is a serial RS-232 channel, the RTS signal may be used for this purpose. Such interruptions may occur due to any number of events, including but not limited to switching activity, internal communication failure, power reset etc. When the VSAT detects such interrupt, it may query the ICU for the interrupt cause. 
         [0029]    An external control device, such as a personal computer (PC), a laptop computer, a PDA or any other device equipped with a suitable communication port and appropriate software may be used for installation purposes. Such a device may be connected to an auxiliary port of the ICU. The ICU may include a mechanism enabling the external control device to monitor commands and telemetry exchanged between the VSAT and the ICU. Furthermore, the ICU may include a mechanism for normally receiving commands through the auxiliary control interface and suppressing any such commands while executing a command received through the main control interface or while sending telemetry via the main control interface. 
         [0030]    If both main and auxiliary control interfaces of the ICU are implemented as serial RS-232 communication channels, the mechanisms described above may be implemented inside the ICU as follows. The receive signal of the main control port may always be connected to the transmit signal of the auxiliary control port, allowing the external control device to receive and monitor any information sent from the VSAT towards the ICU. The receive signal of the auxiliary control port may be normally connected to the transmit signal of the main control port. As the VSAT may echo any character received, any command sent from the external control device and any response sent by the ICU to the VSAT may reach the VSAT and then be echoed back to the ICU. That way, the external control device may also monitor the information sent by the ICU and send commands to the ICU. If the ICU listens for command only on the main control port, it may not distinguish between a command originated from the VSAT and a command originated from the external control device. When the ICU has to send any information to the VSAT, it may internally disconnect the transmit signal of the main control port form the receive signal of the auxiliary port and transmit its own information. As the ICU may limit itself to receiving commands only through the main control port, this disconnection blocks the external control device from sending any commands while the ICU is engaged in exchanging information with the VSAT. It should be noted that in this embodiment the external control device may fail to communicate with the ICU when the VSAT does not echo characters being sent to it (e.g. when the VSAT is reset or powered off). 
         [0031]    In some further embodiments of the invention, the communication channel between the VSAT and the ICU may be implemented using the coaxial cable that carries the DC power towards the LNB and the RF signal from the LNB to the VSAT. In such embodiment, both the remote terminal and the ICU may include applicable hardware for transmitting and receiving information over the coaxial cable using an appropriate protocol. 
         [0032]    In yet further embodiments of the invention, more than one ICU may be connected at a site, supporting testing capabilities, redundancy and/or any other expansion purpose, where the communication channel is common (or concatenated) between the units. For that purpose, each ICU may have 2 identifiers, a private identifier, which may be unique per ICU device, and a global identifier, which may be shared by all VSATs. Any response by an ICU may contain the unique id. 
         [0033]    In another aspect of this invention, the ICU may have two or more buttons, switches or other devices for user control, mounted on one or more of its exterior panels. Each such button, switch or any other control option may represent a pre-selected satellite position. The buttons, switches or other control options may be numbered and where applicable may further include light indicators or other type of display for the purpose of indicating the currently selected satellite position. The remote terminal&#39;s end-user may trigger a procedure of switching to another pre-defined satellite by pressing the appropriate button, flipping the appropriate switch or otherwise manipulating any other control option built into the ICU for this purpose. When such a procedure is triggered the ICU may send the request to the VSAT, which may have the locations of the applicable satellites stored in its memory, e.g. as part of its installation parameters or as a downloadable configuration. The VSAT may then perform the procedure as described above, causing the antenna to rotate and then establish connectivity with the hub using the satellite at the new position. 
         [0034]    In yet another aspect of this invention, the VSAT may be commanded by the network operator to switch to another satellite. The command may include the position of the new satellite, therefore switching can be done to any satellite in view from the location of the VSAT (and not just to the predefined locations supported by any ICU hardware and calibrated during installation). The VSAT may then perform the same procedure described above. The VSAT commands the ICU, which commands the polar mount to rotate the antenna. Once the antenna is aligned according to the desired position, the VSAT may resume connectivity with the hub over the alternative satellite.