Network-access satellite communication system

RELATED APPLICATIONS

0001This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 60/840,809 filed Aug. 29, 2006.

TECHNICAL FIELD

0002This invention relates generally to communication systems, and more particularly to a network-access satellite communication system.

BACKGROUND

0003Commercial satellites have historically been optimized for broadcast applications, where data are transmitted from a broadcast center on the earth up to a satellite in space, and the satellite retransmits these signals down to a population of receive-only earth stations or satellite terminals on the earth. Traditional broadcast satellites are characterized by two features. First, traditional broadcast satellites provide “one-way” communications, such that the recipient of the data (i.e. the end-user) is equipped with a receive-only terminal that has no ability to transmit a signal back up to the satellite. Second, traditional broadcast satellites are designed for wide geographic coverage using antennas or combinations of antennas on the satellite with beams that cover large regional, national, or continental areas.

0004A typical business goal for traditional broadcast satellite operators is to provide as much data as possible (e.g., hundreds of television channels) to a large number of end-users or customers. For content of national or international interest (e.g., televised sports, movies and news), a satellite operator may choose to broadcast the same data to an entire country or even to an entire continent. A video broadcast satellite, with a single antenna beam covering the continental U.S. and providing hundreds of television channels to U.S. customers, is a good example of a traditional broadcast satellite. For regional content, some broadcast satellites have several antenna beams that effectively divide the earth terminal population into large regional groups such that certain combinations of the broadcast data content are transmitted to each group. In both cases, the broadcast satellite system provides one-way communications to customers over a large geographic area.

0005Using a traditional broadcast satellite with antenna beams covering entire national or large regional areas to private communications with a single terminal somewhere in the coverage area is not an efficient approach for network-access satellite services. For example, if a customer with a two-way earth terminal located in New York wants to establish a private two-way connection to the Internet, transmitting energy from a satellite over the entire continental U.S. to send information to a single customer in New York would be an inefficient use of limited and costly satellite resources.

0006In recent years, satellite operators have used satellites to provide network-access services (e.g., telephony, private networks, and Internet access) to a large population of end-users or customers. In modern network-access satellite communications systems, end-users are equipped with earth terminals that both receive signals from a satellite and also transmit signals back up to a satellite. Modern network-access satellite systems are architecturally different from traditional one-way broadcast satellite systems in that each earth terminal is, in effect, carrying on a two-way private conversation with the satellite network and generally has no interest in “hearing” signals being transmitted to and from any other earth terminals on the network.

0007A satellite with a more highly focused antenna beam limited in area to an individual customer's immediate local area s a much more efficient way for transmitting data to this particular customer than a traditional broadcast satellite. Similarly, in the earth-to-space direction, if a receiver on a satellite is focused in on a much narrower geographical region that covers just the customer's immediate area, less power is required for that customer's earth terminal to transmit information to the highly focused receiver on the satellite.

0008Modern network-access satellites are characterized by two features. First, modern network-access satellites provide “two-way” communications between satellites in space and terminals on the earth that have both transmit and receive capability. Second, modern network-access satellites are designed with antennas that cover the geographic area of interest on the earth with many smaller antenna beams, often tightly packed together to provide fall coverage across the area of interest without any gaps. For example, some modern network-access satellites transmit tightly packed clusters of small antenna beams that collectively cover a large geographic area, such as the continental U.S. For two-way network-access communications, by using a number of “spot-beams” over their coverage area, spot-beam satellites have significant advantages over satellites that have a single beam over the coverage area. For example, spot-beam satellites require less satellite transmitter power per customer. As another example, less transmitter power is required for earth terminals to transmit to spot-beam satellites, allowing for smaller and less expensive earth terminals. Additional advantages include the ability to reuse the same frequency bands and channels throughout the spot-beam pattern and associated coverage area, dramatically higher non-broadcast capacity per satellite to provide more compelling services to more customers, and dramatically lower satellite cost per customer. For example, the capacity of a spot-beam satellite to support a large population of end-users may be greatly enhanced by frequency reuse techniques, whereby the same frequency bands and channels are used over and over again in non-adjacent spot-beams. For example, a satellite operator may have a 500 MHz bandwidth allocation for space to earth transmissions assigned by the appropriate regulatory authority. In a single beam network architecture, this satellite operator is limited to 500 MHz of total transmission bandwidth. The transmission bandwidth may be increased by dividing this bandwidth into multiple channels, such as for example, four 125 MHz channels, and assigning one channel to each of numerous spot-beams. In this example, if the satellite utilizes 100 spot-beams, this satellite operator could utilize 12,500 MHz of total transmission bandwidth. This ability to apply frequency reuse techniques to greatly increase the capacity of a satellite network is a technical advantage of the spot-beam satellite architecture.

Overview

0009Particular embodiments of the present invention may reduce or eliminate problems and disadvantages associated with previous network-access satellite communications systems.

0010According to one embodiment, a satellite communications system includes first, second, and third microwave radiators; first and second signal splitters; and a selector. The first microwave radiator is configured to direct microwave signals to a first earth-based gateway antenna system, the microwave signals carrying communications data from a first user terminal located in a spot beam coverage region; and the first signal splitter is configured to collect at least a portion of communications data from the first user terminal. The second microwave radiator is configured to direct microwave signals to a second earth-based gateway antenna system, the microwave signals carrying communications data from a second user terminal; and the second splitter is configured to collect at least a portion of communications data from the second user terminal. The third microwave radiator is configured to direct microwave signals to a third earth-based gateway antenna system; and the first selector is configured to selectively couple the third microwave radiator to a selected one of the first and second splitters, such that the microwave signals directed by the third microwave radiator carry communications data collected from the selected one of the first and second splitters.

0011According to another embodiment, a satellite communications system includes first, second, and third feed horns; first and second directional couplers; and a switch. The first feed horn is configured to direct microwave signals to a first earth-based gateway antenna system, the microwave signals carrying communications data from a first user terminal located in a spot beam coverage region; and the first directional coupler is configured to collect at least a portion of communications data from the first user terminal. The second feed horn is configured to direct microwave signals to a second earth-based gateway antenna system, the microwave signals carrying communications data from a second user terminal; and the second directional coupler is configured to collect at least a portion of communications data from the second user terminal. The third feed horn is configured to direct microwave signals to a third earth-based gateway antenna system; and the first switch is configured to selectively couple the third feed horn to a selected one of the first and second directional couplers, such that the microwave signals directed by the third feed horn carry communications data collected from the selected one of the first and second directional couplers.

0012According to another embodiment, a method of mitigating microwave signal propagation loss for satellite communications includes: transmitting a first microwave signal from a satellite to a first earth-based gateway antenna system, using a first microwave radiator, the microwave signals carrying communications data from an earth-based user terminal; detecting propagation loss in at least one signal between the satellite and the first earth-based gateway antenna system; and transmitting a second microwave signal from the satellite to a second earth-based gateway antenna, using a second microwave radiator, the second microwave signal carrying communications data from the earth-based user terminal.

0013According to another embodiment, a method for use in managing satellite communications, comprising: receiving, at a first earth-based gateway antenna system, one or more microwave communication signals from a substantially geostationary satellite; monitoring for a performance change in at least one signal from the satellite; and in response to detecting a performance change in the at least one signal, transmitting instructions to the satellite to transmit at least a portion of the one or more microwave communication signals to a second earth-based gateway antenna system.

0014According to another embodiment, a method for use in managing satellite communication signal traffic, comprising: monitoring, at a satellite, a signal from a first earth-based gateway antenna system; and in response to detecting a performance change in the monitored signal, transmitting one or more microwave communication signals from the satellite to a second earth-based gateway antenna system.

0015In certain embodiments, an additional gateway may be utilized to provide one or more benefits to a satellite communications system. For example, an additional gateway may be used to provide improved performance by transferring capacity from an existing gateway to the additional gateway in periods when the existing gateway is experiencing problems due to, for example rain or weather fade. As another example, an additional gateway may be used as a backup gateway in cases of a failure at an existing gateway. Certain embodiments may provide all, some, or none of the advantages discussed above. In addition, certain embodiments may provide one or more other advantages, one or more of which may be readily apparent to those skilled in the art from the figures, descriptions, and claims included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and certain of its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

<figref idref="DRAWINGS">FIG. 1</figref> illustrates an example network-access satellite communication system;

<figref idref="DRAWINGS">FIG. 2</figref> illustrates example coverage regions for a spot-beam network-access satellite communications system;

<figref idref="DRAWINGS">FIG. 3</figref> illustrates an example payload for a spot-beam network-access satellite;

<figref idref="DRAWINGS">FIG. 4</figref> illustrates an example downstream signal path through example components of a network-access satellite;

<figref idref="DRAWINGS">FIG. 5</figref> illustrates an example upstream signal path through example components of a network-access satellite;

<figref idref="DRAWINGS">FIGS. 6A and 6B</figref> illustrate example upstream and downstream signal paths through example components of a network-access satellite;

<figref idref="DRAWINGS">FIGS. 7 and 8</figref> illustrate example components that may be used to provide incremental capacity for a network-access satellite;

<figref idref="DRAWINGS">FIG. 9</figref> illustrates example components that may be used to implement non-contiguous beams;

<figref idref="DRAWINGS">FIGS. 10A through 10C</figref> illustrate example components that may be used to implement a utility gateway;

<figref idref="DRAWINGS">FIG. 11</figref> illustrates example components that may be used to control signal power;

<figref idref="DRAWINGS">FIG. 12</figref> illustrates an example method for use in controlling signal power;

<figref idref="DRAWINGS">FIG. 13</figref> illustrates example components that may be used to control signal power;

<figref idref="DRAWINGS">FIG. 14</figref> illustrates an example method for use in controlling signal power; and

<figref idref="DRAWINGS">FIGS. 15A through 15C</figref> illustrate example signals associated with an example method for use in controlling signal power.

DESCRIPTION OF EXAMPLE EMBODIMENTS

0031<figref idref="DRAWINGS">FIG. 1</figref> illustrates an example network-access satellite communications system <b>100</b>. System <b>100</b> includes satellite <b>10</b>, one or more gateways <b>20</b>, and one or more user terminals <b>32</b>. In operation, system <b>100</b> provides for two-way communications between user terminals <b>32</b> and network <b>70</b> through satellite <b>10</b> and gateway <b>20</b>. Satellite <b>10</b> includes payload <b>80</b> and one or more solar arrays <b>90</b>. In certain embodiments, satellite <b>10</b> may be a geosynchronous or geostationary satellite although in alternative embodiments any appropriate orbit for satellite <b>10</b> may be used. Satellite <b>10</b> represents a spot-beam network-access satellite configured to communicate with a population of user terminals <b>32</b> distributed across a defined coverage area. Each user terminal <b>32</b> in communication with satellite <b>10</b> is positioned within at least one spot beam coverage region <b>30</b>. User terminals <b>32</b> are two-way capable and may be designed with adequate transmit power and receive sensitivity to communicate reliably with satellite <b>10</b>. Satellite <b>10</b> communicates with user terminals <b>32</b> by sending and receiving signals through one or more spot beams <b>40</b>.

0032Satellite <b>10</b> communicates with gateway <b>20</b> through signals traveling in beam <b>60</b>. Gateway <b>20</b> sends and receives signals to and from satellite <b>10</b> using gateway antenna system <b>22</b> located within gateway region <b>50</b>. Gateway <b>20</b> is connected to one or more networks <b>70</b>. Network <b>70</b> may represent a local area network (LAN), metropolitan area network (MAN), wide area network (WAN), global communications network such as the Internet, a telephony network, such as the Public Switched Telephone Network (PSTN), or any other suitable public or private network.

0033<figref idref="DRAWINGS">FIG. 2</figref> illustrates example spot beam coverage regions <b>30</b> for spot-beam network-access satellite communications system <b>100</b>. In the embodiment shown, a pattern of spot beam coverage regions <b>30</b> is used to provide coverage for an example satellite coverage area <b>34</b>. Satellite coverage area <b>34</b> may include land masses, water or ocean areas, or a combination of land masses and water areas. As shown in <figref idref="DRAWINGS">FIG. 2</figref>, satellite coverage area <b>34</b> represents the continental United States and portions of Alaska. Although any appropriate pattern may be used for spot beam coverage regions <b>30</b>, in certain embodiments, spot beam coverage regions <b>30</b> may be distributed in a pattern that provides continuous coverage throughout satellite coverage area <b>34</b>. In certain embodiments, one or more spot beam coverage regions <b>30</b> may overlap at least in part with one or more other spot beam coverage regions <b>30</b>.

0034In certain embodiments, network access may be provided to the spot beam coverage regions <b>30</b> within satellite coverage area <b>34</b> using one or more satellites <b>10</b>. In addition, each satellite <b>10</b> providing network access to satellite coverage area <b>34</b> may receive signals from one or more gateways <b>20</b>. In certain embodiments, each satellite <b>10</b> may receive signals from as many as ten or more gateways <b>20</b> to provide network access to user terminals <b>32</b> within multiple spot beam coverage regions <b>30</b> in satellite coverage area <b>34</b>.

0035<figref idref="DRAWINGS">FIG. 3</figref> illustrates an example payload <b>80</b> for satellite <b>10</b>. Payload <b>80</b> includes antenna reflectors <b>82</b>, feed horn clusters <b>84</b>, telemetry command and ranging (TC&amp;R) horn <b>88</b>, and beacon horn <b>89</b>. Each feed horn cluster <b>84</b> may include numerous feed horns <b>86</b>. In operation, microwave signals may be transmitted by one or more feed horns <b>86</b> and then focused onto a particular region of the earth by antenna reflector <b>82</b>. In certain embodiments, antenna reflector <b>82</b> may represent a Ka band transmit reflector, a Ka band receive reflector, or any appropriate reflector for directing the transmission path of microwave signals in the appropriate frequency band. In certain embodiments, particular antenna reflectors <b>82</b> and feed horn clusters <b>84</b> may be utilized to transmit signals from satellite <b>10</b>, while particular antenna reflectors <b>82</b> and feed horn clusters <b>84</b> may be utilized to receive microwave signals at satellite <b>10</b>. In alternative embodiments, satellite <b>10</b> may utilize one or more of two-way antennas, direct radiating antennas, array antennas, or other electromagnetic transducers.

0036In operation, through the use of multiple feed horns <b>86</b> within a feed horn cluster <b>84</b>, a plurality of spot beams <b>40</b> may be projected into satellite coverage area <b>34</b>, such that each spot beam <b>40</b> defines a particular spot beam coverage region <b>30</b>. Similarly, each particular feed horn <b>86</b> within a feed horn cluster <b>84</b> may operate together with antenna reflector <b>82</b> to receive microwave signals within a particular spot beam <b>40</b> from one or more user terminals <b>32</b> within a particular spot beam coverage region <b>30</b>. In certain embodiments, one or more dedicated feed horns <b>86</b> may be used to transmit microwave signals through one or more beams <b>60</b> to one or more gateways <b>20</b> within gateway region <b>50</b>. In alternative embodiments, when a gateway <b>20</b> is located within a particular spot beam coverage region <b>30</b>, satellite payload <b>80</b> may be configured such that a particular feed horn <b>86</b> transmits (or receives) microwave signals to (or from) one or more user terminals <b>32</b> and gateway <b>20</b>. In certain embodiments, a gateway region <b>50</b> may be included within or overlap with one or more spot beam coverage regions <b>30</b>. In certain embodiments, a gateway region <b>50</b> may be entirely outside satellite coverage area <b>34</b>.

0037Although feed horns are illustrated in the drawings and identified throughout this description, in certain embodiments other suitable microwave radiators can be used together or as an alternative to feed horns. For example, and not by way of limitation, other suitable microwave radiators may include phased arrays, direct radiating apertures, slotted arrays, and helical radiators. Various embodiments may be utilized any suitable microwave radiator without departing from the scope of the invention.

0038The operation of system <b>100</b> can be separated into a forward (downstream) direction and a return (upstream) direction. In the downstream direction, data arrives at gateway <b>20</b> from network <b>70</b>, gateway <b>20</b> transmits that data up to satellite <b>10</b>, and satellite <b>10</b> relays that data down in a spot beam <b>40</b> to user terminal <b>32</b> in region <b>30</b>. In the upstream direction, user terminal <b>32</b> transmits data up to satellite <b>10</b>, satellite <b>10</b> relays that data down to gateway <b>20</b>, and gateway <b>20</b> forwards that data to network <b>70</b>.

0039Although the components of satellite payload <b>80</b> are described herein and illustrated in <figref idref="DRAWINGS">FIGS. 4-10A</figref> and <b>13</b> as analog components that may be used to guide and manipulate microwave signals, in alternative embodiments, one or more digital components may be used in addition to or as an alternative to the use of analog components. For example, satellite payload <b>80</b> may include one or more analog-to-digital converters, digital signal processors, and/or digital-to-analog converters. In various embodiments, one or more of the functions described herein may be performed with analog components, digital components, or a combination thereof without departing from the scope of the invention.

0040<figref idref="DRAWINGS">FIG. 4</figref> illustrates an example downstream signal path through example components of satellite payload <b>80</b>. For example, In the embodiment shown, a microwave signal may be received from gateway antenna system <b>22</b>, split into multiple channels, amplified, and transmitted through eight different spot beams <b>40</b> to eight different spot beam coverage regions <b>30</b>. Although the example components may be utilized to transmit signals through eight different spot beams <b>40</b>, in alternative embodiments, more or fewer components may be utilized to provide more or fewer functions than those described below, and may be utilized to transmit signals through more or fewer spot beams <b>40</b>.

0041Moving from left to right in <figref idref="DRAWINGS">FIG. 4</figref>, microwave signals are received from gateway <b>20</b> through beam <b>60</b> at feed horn <b>86</b>. The signals travel through polarizer <b>102</b> and switch <b>104</b> into low noise amplifier <b>106</b>. As with many of the components described herein, within satellite payload <b>80</b> many of the components may be implemented with redundancies designed to increase the longevity of satellite <b>10</b> in the event of failure of one or more components. This redundancy may be implemented through the use of multiple components distributed in parallel or in a ring configuration. Although particular configurations are shown and described herein as having specified numbers and configurations of redundant components, in alternative embodiments, any appropriate number and configuration of components may be utilized to achieve the desired level of redundancy. Accordingly, as shown in <figref idref="DRAWINGS">FIG. 4</figref> there are two low noise amplifiers <b>106</b> distributed in parallel along the signal path. The signal traveling out of low noise amplifier <b>106</b> travels through another switch <b>104</b> and into down converter <b>108</b>. Again, in the embodiment shown down converter <b>108</b> is doubly redundant with two down converters <b>108</b> implemented in parallel along the signal path. From down converter <b>108</b>, the signal travels through a third switch <b>104</b> and into input multiplexer <b>110</b>. In the embodiment shown, input multiplexer <b>110</b> is a one-to-four multiplexer with one signal input and four signal outputs. The four signal outputs shown on the right side of input multiplexer <b>110</b> represent four different channels from the input signal on the left-hand side of input multiplexer <b>110</b>. In this example embodiment, these four output channels travel from input multiplexer <b>110</b> into a bank of ring redundancy switches <b>112</b>. In the embodiment shown, ring redundancy switches <b>112</b> provide for six potential signal paths for these four signal channels. The signal channels traveling from ring redundancy switches <b>112</b> travel through a channel amplifier <b>114</b> and into traveling wave tube (TWT) amplifier <b>116</b> before returning to a second bank of ring redundancy switches <b>112</b>. From the second bank of ring redundancy switches <b>112</b>, each signal channel travels to an output multiplexer <b>118</b> which divides each of these four signal channels into two separate channels for a total of eight signal channels. Each of these eight signal channels is then polarized using polarizer <b>102</b> and transmitted using feed horn <b>86</b> through a spot beam <b>40</b> to one or more user terminals <b>32</b> within particular spot beam coverage regions <b>30</b>. In various embodiments, polarizers <b>102</b> may be implemented for use with multi-band or dual-band signals utilizing linear (vertical/horizontal) polarization and/or circular (left-hand/right-hand) polarization. In alternative embodiments, more or fewer components may be utilized to provide the same, more, or fewer functions.

0042<figref idref="DRAWINGS">FIG. 5</figref> illustrates an example upstream signal path through example components of satellite payload <b>80</b>. In the embodiment shown, microwave signals may be received from user terminals <b>32</b> located within eight different spot beam coverage regions <b>30</b> amplified, combined into a single composite signal, and transmitted through a spot-beam <b>60</b> to gateway antenna system <b>22</b>. Although the example components may be utilized to receive signals from user terminals <b>32</b> located in eight different coverage areas <b>30</b>, in alternative embodiments, more or fewer components may be utilized to provide more or fewer functions than those described below, and may be utilized to receive signals from user terminals <b>32</b> located in more or fewer spot beam coverage regions <b>30</b>.

0043Moving from right to left in <figref idref="DRAWINGS">FIG. 5</figref>, upstream communication signals are received from one or more user terminals <b>32</b> through spot beam <b>40</b> at feed horn <b>86</b>. The communication signals then pass through polarizer <b>102</b> and switch <b>104</b> into low noise amplifier <b>106</b>. As shown in <figref idref="DRAWINGS">FIG. 5</figref>, low noise amplifier <b>106</b> is shown as two-for-one redundant with two low noise amplifiers <b>106</b> distributed in parallel along the signal path. From low noise amplifier <b>106</b>, the signal passes through switch <b>104</b> and into input multiplexer <b>120</b>. In the embodiment shown, the upstream signals from eight different feed horns feed into input multiplexer <b>120</b> which combines these eight signals into a single composite signal. From input multiplexer <b>120</b>, the composite signal travels through switch <b>104</b> and into down converter <b>122</b>. In the embodiment shown, two for one sparing is utilized with two down converters <b>122</b> distributed in parallel along the signal path. From down converter <b>122</b>, the composite signal travels through switch <b>104</b>, into. As with down converter <b>122</b>, in the embodiment shown, two for one sparing is utilized for channel amplifier <b>114</b> and traveling wave tube amplifier <b>116</b> with each of these components distributed in parallel. From traveling wave tube amplifier <b>116</b>, the composite signal travels through switch <b>104</b> and into transmission filter <b>124</b>. The composite signal is then polarized using polarizer <b>102</b> and transmitted by feed horn <b>86</b> through beam <b>60</b> to gateway <b>20</b>. In alternative embodiments, more or fewer components may be utilized to provide the same, more, or fewer functions.

0044In the embodiments shown in <figref idref="DRAWINGS">FIGS. 4 and 5</figref>, communication signals traveling to and from gateway <b>20</b> utilize a separate feed horn <b>86</b> from the feed horns <b>86</b> utilized for communications to and from user terminals <b>32</b>. However, in alternative embodiments, as discussed above, one or more feed horns <b>86</b> may send and/or receive communication signals to gateway <b>20</b> and one or more user terminals <b>32</b>.

0045<figref idref="DRAWINGS">FIGS. 6A and 6B</figref> illustrate example upstream and downstream signal paths through example components of satellite payload <b>80</b>, in which one or more feed horns <b>86</b> are utilized to communicate both with one or more gateway transmitters <b>22</b> and one or more user terminals <b>32</b>.

Incremental Capacity

0046In embodiments of system <b>100</b> utilized to provide network access to a population of user terminals <b>32</b>, numerous gateways <b>20</b> may be required. Each gateway <b>20</b> may be expensive to construct and may require costly manpower to maintain and operate. Following initial launch, satellite <b>10</b> may experience a light signal traffic load for a period of time until demand increases. During this period of time, while satellite <b>10</b> is operated below capacity, the number of gateways <b>20</b> required to provide sufficient coverage may be less than the entire set of gateways <b>20</b> required to support fall capacity. Constructing and operating the entire set of gateways <b>20</b> during initial operations when the satellite is experiencing a light signal traffic load may be prohibitively expensive. The ability to launch a new satellite and immediately provide full geographic coverage with a smaller number of gateways <b>20</b>, and then add additional gateways incrementally as required to support increasing demand, has significant economic advantages. One way to provide such incremental capacity is through a “filter-and-switch” approach. A filter-and-switch approach allows the bandwidth (or channels) from certain gateways <b>20</b> to be divided into two or more subsets, where each subset is assigned to a group of feed horns <b>86</b> using switches within payload <b>80</b> of satellite <b>10</b>.

0047<figref idref="DRAWINGS">FIG. 7</figref> illustrates example components that may be included in payload <b>80</b> to provide incremental satellite capacity in the downstream direction using a filter-and-switch approach. In the example shown in <figref idref="DRAWINGS">FIG. 7</figref>, a single gateway <b>20</b> may be used initially to provide network-access to user terminals <b>32</b> located in six spot beam coverage regions <b>30</b> associated with six different spot beams <b>40</b>. Using these components, incremental capacity may be added through the use of switches <b>202</b> and the addition of an additional gateway <b>20</b>. In this initial configuration, all of the switches <b>202</b> are set to position “1” to support six spot beam coverage regions <b>30</b> with a single gateway <b>20</b>. Moving from left to right in <figref idref="DRAWINGS">FIG. 7</figref>, the communication signals are initially received at feed horn <b>86</b><i>a </i>from beam <b>60</b><i>a. </i>In the single gateway configuration, the signals received at feed horn <b>86</b><i>a </i>pass through switch <b>202</b><i>a </i>(set at position “1”) and into channel filters <b>204</b><i>a </i>and <b>204</b><i>b. </i>Communication signals for channels <b>1</b> through <b>3</b> pass from channel filter <b>204</b><i>a </i>through switch <b>202</b><i>b </i>(set at position “1”) and into power combiners <b>212</b><i>a </i>through <b>212</b><i>c. </i>Using these components, the communication signals associated with channel <b>1</b> are transmitted by feed horn <b>86</b><i>b </i>to one or more user terminals <b>32</b> through spot beam <b>40</b><i>a. </i>Similarly, the communication signals associated with channel <b>2</b> are transmitted by feed horn <b>86</b><i>c </i>and the communication signals associated with channel <b>3</b> are transmitted by feed horn <b>86</b><i>d. </i>The communication signals associated with channels <b>4</b> through <b>6</b> leave channel filter <b>204</b><i>b, </i>pass through switch <b>202</b><i>c </i>(set at position “1”), and arrive at power combiners <b>212</b><i>d </i>through <b>212</b><i>f. </i>Using these components the communication signals associated with channel <b>4</b> are transmitted by feed horn <b>86</b><i>e </i>to one or more user terminals <b>32</b> through spot beam <b>40</b><i>d. </i>Similarly, the signals associated with channel <b>5</b> are transmitted by feed horn <b>86</b><i>f </i>and the communication signals associated with channel <b>6</b> are transmitted by feed horn <b>86</b><i>g. </i>

0048Using the filter-and-switch approach illustrated, the capacity of satellite <b>10</b> may be increased by adding an additional gateway <b>20</b> to support the six spot beam coverage regions <b>30</b>. In this configuration, all of switches <b>202</b> are set to position “2,” such that feed horns <b>86</b><i>b </i>through <b>86</b><i>d </i>are supported by a first gateway <b>20</b> in communication with feed horn <b>86</b><i>a </i>and feed horns <b>86</b><i>e </i>through <b>86</b><i>g </i>are supported by a second gateway <b>20</b> in communication with feed horn <b>86</b><i>h. </i>In this configuration, moving from left to right in <figref idref="DRAWINGS">FIG. 7</figref>, the communication signals received at feed horn <b>86</b><i>a </i>pass through switch <b>202</b><i>a </i>(set at position “2”) and into channel filter <b>204</b><i>c. </i>From channel filter <b>204</b><i>c, </i>the communication signals travel through switch <b>202</b><i>b </i>(set at position “2”), through power combiners <b>212</b><i>a </i>through <b>212</b><i>c, </i>and are then transmitted by feed horns <b>86</b><i>b </i>through <b>86</b><i>d. </i>The communication signals received by feed horn <b>86</b><i>h </i>pass through channel filter <b>206</b>, through switch <b>202</b><i>c </i>(set at position “2”), through power combiners <b>212</b><i>d </i>through <b>212</b><i>f, </i>and are transmitted by feed horns <b>86</b><i>e </i>through <b>86</b><i>g. </i>

0049Using the example filter-and-switch approach illustrated, spot beams <b>40</b><i>a </i>through <b>40</b><i>f </i>may be serviced at half capacity using a single gateway <b>20</b>, as shown in <figref idref="DRAWINGS">FIG. 7</figref> with switches <b>202</b> set at position “1,” or serviced at full capacity using two gateways <b>20</b>, as shown in <figref idref="DRAWINGS">FIG. 7</figref> with switches <b>202</b> set at position “2.” The filter-and-switch approach for use in the upstream direction may be implemented in a similar manner.

0050In alternative embodiments, incremented capacity may be provided with fewer filters and switches than used with the “filter-and-switch” approach. For example, such incremental capacity may be provided using a “direct-connect” approach. Using the direct-connect approach, gateways <b>20</b> may be connected to spot beams <b>40</b> such that a first portion of each spot beam <b>40</b> capacity may be serviced by a first gateway <b>20</b> and a second portion of each spot beam <b>40</b> capacity may be serviced by a second gateway <b>20</b>. This approach can be extended and scaled to allow various portions of the capacity of particular spot beams <b>40</b> to be serviced by multiple gateways <b>20</b>, such that the operational capacities of these particular spot beams <b>40</b> increase in increments as each additional gateway <b>20</b> is built and activated.

0051<figref idref="DRAWINGS">FIG. 8</figref> illustrates example components that may be included in satellite payload <b>80</b> to provide incremental capacity in the downstream direction using a direct-connect approach. In the example shown, a single gateway <b>20</b> may be used to initially provide network access to user terminals <b>32</b> located in six spot beam coverage regions <b>30</b> associated with six different feed horns <b>86</b>. Using these components, incremental capacity may be added without changing the configuration of the components in satellite payload <b>80</b>. Moving from left to right in <figref idref="DRAWINGS">FIG. 8</figref>, the communication signals are initially received at feed horn <b>86</b><i>a </i>through beam <b>60</b><i>a. </i>The communication signals received at feed horn <b>86</b><i>a </i>are directed through channel filter <b>206</b><i>a. </i>From channel filter <b>206</b><i>a, </i>the communications signals are split and directed through six frequency selective power combiners. In the embodiment shown, the communications signals are split into six different wave paths; however, in alternative embodiments, other variations may be used with an alternative number of wave paths and/or power combiners.

0052As shown in <figref idref="DRAWINGS">FIG. 8</figref>, the communication signals received by feed horn <b>86</b><i>a </i>are filtered by channel filter <b>206</b><i>a, </i>split, directed through six different frequency selective power combiners <b>212</b><i>a </i>through <b>212</b><i>f </i>and transmitted by feed horns <b>86</b><i>b </i>through <b>86</b><i>g. </i>The communication signals received by feed horn <b>86</b><i>h </i>are directed to channel filter <b>206</b><i>b. </i>From channel filter <b>206</b><i>b, </i>the communications signals are split six ways through the use of a microwave signal splitter or other appropriate device. In the embodiment shown, the communications signals are split into six different wave paths; however, in alternative embodiments, other variations may be used with an alternative number of wave paths. In addition, although the number of wave paths used for the communications signals received by feed horn <b>86</b><i>a </i>is the same as the number of channels utilized for the communications signals received by feed horn <b>86</b><i>h, </i>in alternative embodiments, these numbers may vary from each other, such that the one-to-one ratio is not maintained. Each channel of communication signals is then directed through a frequency selective power combiner in communication with a feed horn <b>86</b>. In alternative embodiments, rather than utilize a signal splitter and a frequency selective power combiner, a multiplexer and a power combiner may be used.

0053In embodiments in which a single gateway <b>20</b> is transmitting communication signals through beam <b>60</b><i>a </i>to feed horn <b>86</b><i>a, </i>spot beams <b>40</b><i>a </i>through <b>40</b><i>f </i>may be serviced at half capacity. In embodiments in which two gateways <b>20</b> are transmitting communication signals and these communication signals are received at feed horns <b>86</b><i>a </i>and <b>86</b><i>h </i>through beams <b>60</b><i>a </i>and <b>60</b><i>b, </i>power combiners <b>212</b> combine selected channels of communication signals received from both feed horns <b>86</b><i>a </i>and <b>86</b><i>h. </i>As shown in <figref idref="DRAWINGS">FIG. 8</figref>, in certain embodiments, the channels selected to be combined in each of power combiners <b>212</b><i>a </i>through <b>212</b><i>f </i>may be selected such that each power combiner frequency selects two distinct channels to avoid interference. By combining the communication signals from beams <b>60</b><i>a </i>and <b>60</b><i>b, </i>spot beams <b>40</b><i>a </i>through <b>40</b><i>f </i>may be serviced at full capacity. The direct-connect approach for use in the upstream direction may be implemented in a similar manner.

0054The direct-connect approach, may provide a lower cost and increased reliability solution for a network-access satellite with incremental capacity. For example, the direct-connect approach may be less expensive than the filter-and-switch approach because the direct-connect approach does not require the added weight and cost of additional filters and switches. As another example, the direct-connect approach may be more reliable because it utilizes fewer switches and filters in the primary signal path than the filter-and-switch approach. In certain embodiments, the provision of incremental capacity may allow each spot beam <b>40</b> to be serviced by multiple gateways, such that only a portion of the capacity is lost if a gateway <b>20</b> suffers an outage. Certain embodiments may easily be scaled to any number of gateways <b>20</b> and any number of associated spot beams <b>40</b>. In certain embodiments, satellite payload <b>80</b> may be configured such that certain spot beams <b>40</b> have one associated gateway <b>20</b>, certain spot beams <b>40</b> have two associated gateways <b>20</b>, certain spot beams <b>40</b> have three associated gateways <b>20</b>, etc.

Non-Contiguous Beams

0055Demand for network-access satellite services may be non-uniform within satellite coverage area <b>34</b>. In certain embodiments, network-access satellite communication system <b>100</b> may be configured to provide non-uniform capacity within satellite coverage area <b>34</b>. For example, system <b>100</b> may be configured to provide (1) larger spot beams <b>40</b> to cover lower density spot beam coverage regions <b>30</b>; (2) lower bandwidth for spot beams <b>40</b> covering lower density spot beam coverage regions <b>30</b>; (3) lower power transmitters to serve spot beams <b>40</b> covering lower density spot beam coverage regions <b>30</b>; and (4) non-contiguous spot beams <b>40</b>. Non-contiguous beams may provide both non-uniform capacity and flexibility to balance capacity across two or more beams without physical switching or processing on satellite <b>10</b>. An example non-contiguous beam may be implemented as two or more downstream spot beams <b>40</b> that may transmit identical, or substantially identical, communication signals over the same channel to multiple non-contiguous spot beam coverage regions <b>30</b> and as two or more upstream spot beams <b>40</b> that may be received and processed by payload <b>80</b> as a single spot beam <b>40</b> or as a single channel.

0056Transmitters <b>32</b> throughout the non-contiguous spot beam coverage regions <b>30</b> may share the same increment of satellite capacity. In particular, satellite <b>10</b> may transmit the same downstream signal to all transmitters <b>32</b> in multiple non-contiguous spot beam coverage regions <b>30</b> and may process upstream signals from transmitters <b>32</b> in multiple non-contiguous spot beam coverage regions <b>30</b> as if they were located in a single spot beam coverage region <b>30</b>. In certain embodiments, the downstream signal may be power divided into two or more signals, which may occupy the same bandwidth and may have equal or unbalanced power. These signals may then be transmitted using two or more feed horns <b>86</b> to two or more non-contiguous and non-overlapping spot beam coverage regions <b>30</b>. In the upstream direction, receive signals from two or more feed horns <b>86</b> may be power combined and processed as a single signal. This approach may be scaled to any number of spot beam coverage regions <b>30</b>.

0057In certain embodiments, capacity may be efficiently shared across multiple spot beam coverage regions <b>30</b> using, for example, time domain techniques such as time division multiple access (TDMA) technology. In a satellite network where each user terminal <b>32</b> performs turn-around ranging, either to the satellite or through the satellite, to establish a time delay reference, user terminals <b>32</b> in each spot beam coverage region <b>30</b> supported by a single communication channel may share capacity on a single TDMA waveform.

0058In certain embodiments, the use of non-contiguous spot beams <b>40</b> may allow shared capacity across multiple spot beam coverage regions <b>30</b> supported by a single communication channel. In certain embodiments, the use of non-contiguous spot beams <b>40</b> may allow spot beam coverage regions <b>30</b> to be the same size and shape as other spot beam coverage regions <b>30</b> in a uniform pattern within satellite coverage area <b>34</b>, which may provide improved performance and may minimize interference in a tightly packed pattern of spot beam coverage regions <b>30</b>. In certain embodiments, the use of non-contiguous spot beams <b>40</b> may provide for the shared use of the identical, or substantially identical, signals, (including burst rates, bandwidths, and waveforms) in beam areas where the demand for network access may be dramatically lower than the average beam capacity.

0059<figref idref="DRAWINGS">FIG. 9</figref> illustrates example components that may be included in payload <b>80</b> to implement non-contiguous spot beams <b>40</b>, according to particular embodiments. The components illustrated in <figref idref="DRAWINGS">FIG. 9</figref> may be used in combination with and/or as an alternative to one or more of the components illustrated in <figref idref="DRAWINGS">FIG. 4</figref>, <b>5</b>, or <b>6</b>A-<b>6</b>B. In the embodiment shown, signals generated by transmitter <b>230</b> are passed to power divider <b>232</b> which then passes the signals on to both transceiver <b>234</b><i>a </i>and transceiver <b>234</b><i>b. </i>As used herein, a transceiver is a device configured to allow upstream and downstream signals to be transmitted and/or received through the same node, device, and/or path. In certain embodiments, a transceiver may or may not include or be coupled to a diplexer, a transmit-receive filter, or other similar device.

0060Signals from transceiver <b>234</b><i>a </i>are then transmitted by feed horn <b>236</b><i>a </i>through spot beam <b>40</b><i>a </i>to spot beam coverage region <b>30</b><i>a. </i>Similarly, signals from transceiver <b>234</b><i>b </i>are transmitted by feed horn <b>236</b><i>b </i>through spot beam <b>40</b><i>b </i>to spot beam coverage region <b>30</b><i>b. </i>Through the use of these components, a single signal generated by transmitter <b>230</b><i>a </i>may be distributed to two non-contiguous spot beam coverage regions <b>30</b><i>a </i>and <b>30</b><i>b. </i>Similarly, signals generated by one or more transmitters within spot beam coverage region <b>30</b><i>a </i>may be transmitted through spot beam <b>40</b><i>a </i>and received by feed horn <b>236</b><i>a. </i>These signals may then be directed through transceiver <b>234</b><i>a </i>and into power combiner <b>238</b>. At the same time, signals generated by one or more transmitters <b>32</b> within spot beam coverage region <b>30</b><i>b </i>may be transmitted through spot beam <b>40</b><i>b </i>and received by feed horn <b>236</b><i>b. </i>These signals may be directed through transceiver <b>234</b><i>b </i>and into power combiner <b>238</b>. The signals generated by transmitter <b>32</b> within spot beam coverage regions <b>30</b><i>a </i>and <b>30</b><i>b </i>may be combined within power combiner <b>238</b> and directed to receiver <b>239</b>. In certain embodiments, techniques such as time-division multiplexing, frequency-division multiplexing, and code-division multiplexing may be used to combine communications signals associated with non-contiguous regions using a single channel or discrete frequency band.

Mitigating Rain Fade

0061Certain types of weather, especially the heavy rain often associated with thunderstorms, can cause significant propagation loss or attenuation of electromagnetic waves, particularly at microwave and millimeter wave frequencies. In a network-access satellite system, many tens of thousands of user terminals <b>32</b> may access network <b>70</b> through a single gateway <b>20</b>. Disruptive weather between a particular gateway <b>20</b> and satellite <b>10</b> could result in disruption of service for all user terminals <b>32</b> who connect to network <b>70</b> through that particular gateway <b>20</b>.

0062One approach to mitigating propagation loss or attenuation due to disruptive weather such as heavy rain (i.e., “rain fade” or “weather fade”) is to build a second, backup gateway <b>20</b>, which may be near the first gateway <b>20</b> but far enough away from the primary gateway <b>20</b> such that the probability of both gateways <b>20</b> being simultaneously affected by weather is diminishingly small. Using this approach, a second gateway <b>20</b> may be built for every primary gateway <b>20</b> that transmits signals to satellite <b>10</b>. Using this approach, each second gateway <b>20</b> would not provide any additional capacity or generate any additional revenue. Another approach to mitigating weather fade is to build a utility gateway <b>250</b> with utility transceiver <b>252</b>.

0063This approach utilizes satellite <b>10</b> with a net capacity that utilizes a number of operational gateways <b>20</b>, for example N, and also utilizes a utility gateway, for a total of N+1 gateways. The utility gateway can take over the functions of any one of the N operational gateways. The satellite is designed with commandable switching, either automatic or by ground control, to switch capacity from a gateway <b>20</b> suffering propagation loss or attenuation and at risk of outage to the utility gateway. A single utility gateway may provide a weather diversity site capable of backing up any of the operational gateways <b>20</b> on a “one at a time” basis. In certain embodiments, network-access satellite communications system <b>100</b> may utilize more than one utility gateway.

0064<figref idref="DRAWINGS">FIG. 10A</figref> illustrates example components that may be used to implement a utility gateway for use in mitigating weather fade and/or disaster at an operational gateway. In the embodiment shown, the components are utilized to implement two operational gateways <b>20</b><i>a </i>and <b>20</b><i>b </i>and a single utility gateway <b>250</b>. In alternative embodiments, any number of operational gateways and utility gateways may be implemented using similar components. <figref idref="DRAWINGS">FIG. 10A</figref> is intended to illustrate only those components which may be included in payload <b>80</b> to implement the utility gateway function, according to certain embodiments. In various embodiments, the components illustrated in <figref idref="DRAWINGS">FIG. 10A</figref> may be used together with some or all of the components illustrated in <figref idref="DRAWINGS">FIG. 4</figref>, <b>5</b>, or <b>6</b>A-<b>6</b>B.

0065In the embodiment shown in <figref idref="DRAWINGS">FIG. 10A</figref>, for each operational gateway <b>22</b>, payload <b>80</b> includes a transmitter <b>232</b>, a transceiver <b>234</b>, a feed horn <b>236</b>, and a receiver <b>238</b>. These components may be utilized together with other components in payload <b>80</b> to transmit and/or receive communication signals to and/or from gateway <b>22</b> through beam <b>60</b>. In certain embodiments, a utility gateway may be implemented by the addition of directional couplers <b>240</b>, switches <b>202</b>, transmitter <b>242</b>, transceiver <b>244</b>, feed horn <b>246</b>, and receiver <b>248</b>. For example, in the event of rain fade experienced at gateway <b>20</b><i>a, </i>switches <b>202</b> may be set to position “ <b>1</b>.” Utility gateway <b>250</b> may then be used to transmit and/or receive communication signals previously associated with operational gateway <b>20</b><i>a. </i>Similarly, in the event of rain fade experienced at operational gateway <b>20</b><i>b, </i>switches <b>202</b> may be set to position “2.” Utility gateway <b>250</b> may then be utilized to transmit and/or receive signals previously associated with operational gateway <b>20</b><i>b. </i>In certain embodiments, switches <b>202</b> may have additional positions, such as an off position. Although directional couplers are discussed herein as an example component that may be utilized to combine or split a signal, any appropriate active or passive combiner or splitter may be used to perform the functions provided by a directional coupler. In certain embodiments, as an alternative to or in addition to directional couplers <b>240</b> or other appropriate active or passive combiner or splitter, one or more switches may be utilized to direct communication signals to and/or from utility gateway <b>250</b>.

0066An example of the utility gateway concept is shown in <figref idref="DRAWINGS">FIG. 10A</figref> for the case where the functions of any one of two operational gateways <b>20</b> may be replaced by a utility gateway <b>250</b>. In certain embodiments, the transition of communications traffic from an operational gateway <b>20</b> to utility gateway <b>250</b> may be performed all at once. As an alternative, the transition of communications traffic may be performed incrementally. For example, the transition of communication traffic may be performed incrementally by channel or by other category.

0067In certain embodiments, the use of utility gateway <b>250</b> may substantially mitigate the risk of service disruptions at multiple operational gateways <b>20</b> by serving as a backup for multiple operational gateways <b>20</b> on a one-at-a-time basis. In addition, the use of utility gateway <b>250</b>, that can serve as a backup for multiple operational gateways <b>20</b>, may be less expensive than building backup gateways for each operational gateway <b>20</b> on a one-to-one basis. In particular embodiments, utility gateway <b>250</b> may be located far enough from any operational gateway <b>20</b> that the likelihood of a single storm affecting both an operational gateway <b>20</b> and a utility gateway <b>250</b> is nearly zero. In certain embodiments, a utility gateway <b>250</b> may be located in a dry area, such as in a desert, or on a mountain top where the likelihood of a disruptive rain event at utility gateway <b>250</b> is diminishingly small.

0068A number of extensions of the utility gateway for weather related outages can be envisioned, including (1) extending the concept to two or more utility gateways <b>250</b> to provide protection from simultaneous disruptive events at operational gateways <b>20</b>; and (2) utilizing an operational gateway <b>20</b> with adequate available capacity as a partial utility gateway to take over at least a portion of the functions of another operational gateway suffering disruption or weather propagation loss or attenuation.

Disaster Recovery

0069Gateways may be vulnerable to electrical failures, fire, flood, tornado, physical destruction, sabotage, or other risks that could result in the gateway being non-operational for an extended period of time. Methods to mitigate these risks may include any combination of careful site location, facility hardening, and construction of backup gateways. Alternative methods may include the utilization of a transportable gateway which can be brought to or near the damaged gateway to quickly provide temporary service until the damaged gateway can be repaired. As yet another alternative, a utility gateway may be utilized to mitigate the risk of a disaster at an operational gateway. By utilizing a utility gateway, a satellite operator may transfer all or a portion of the load from a failed, damaged or otherwise non-operational gateway to a utility gateway to quickly restore service. A satellite may utilize multiple utility gateways to provide simultaneous protection against multiple events including weather and disaster related outages.

Network Management

0070In certain embodiments, a utility gateway <b>250</b> may be utilized to monitor, on a non-interference basis, the signals from one or more selected operational gateways <b>20</b> to satellite <b>10</b> and/or signals from satellite <b>10</b> to those selected operational gateways <b>20</b>. A utility gateway <b>250</b> with monitoring capabilities may be utilized to facilitate network management by evaluating power levels, signal quality, loading levels, interference, and other key parameters associated with the selected operational gateways <b>20</b>. Utility gateway <b>250</b> may utilize a single instance of monitoring equipment to monitor an operational gateway's full downstream and upstream communications traffic without using any of the operational gateway's bandwidth or reducing its capacity.

0071In order to monitor an operational gateway <b>20</b>, the downstream communications traffic from the operational gateway <b>20</b> to satellite <b>10</b> is transmitted by satellite <b>10</b> to user terminals <b>32</b>, and a copy of the downstream traffic is also transmitted by satellite <b>10</b> to the utility gateway <b>250</b>. In a similar manner, satellite <b>10</b> may transmit a copy of the upstream communications traffic that is transmitted from satellite <b>10</b> to the operational gateway <b>20</b> to utility gateway <b>250</b> for monitoring.

0072<figref idref="DRAWINGS">FIG. 10B</figref> illustrates example components that may be used to implement a utility gateway <b>250</b> for use in network management. <figref idref="DRAWINGS">FIG. 10B</figref> is intended to illustrate only those components which may be included in payload <b>80</b> to implement a utility gateway <b>250</b> for use in network management, according to certain embodiments. In various embodiments, the components illustrated in <figref idref="DRAWINGS">FIG. 10B</figref> may be used together with some or all of the components illustrated in <figref idref="DRAWINGS">FIG. 4</figref>, <b>5</b>, or <b>6</b>A through <b>6</b>B. In the embodiment shown, the example components may be utilized to monitor upstream and/or downstream traffic from one of operational gateways <b>20</b><i>a </i>and <b>20</b><i>b, </i>without disrupting the communication traffic to and/or from either of operational gateways <b>20</b><i>a </i>and <b>20</b><i>b. </i>Through the use of switches <b>202</b>, a selection may be made as to which portion of communications traffic will be monitored by utility gateway <b>250</b> at any given time. For example, in order to monitor upstream network traffic at operational gateway <b>20</b><i>a, </i>switch <b>202</b><i>a </i>may be set to position “1” and switch <b>202</b><i>c </i>may be set to position “1,” as illustrated in <figref idref="DRAWINGS">FIG. 10B</figref>. As another example, downstream communications traffic may be monitored at operational gateway <b>20</b><i>a </i>by setting switch <b>202</b><i>a </i>to position “2” and setting switch <b>202</b><i>c </i>to position “1.” Communications traffic may be similarly monitored by setting switch <b>202</b><i>c </i>to position “2,” and setting switch <b>202</b><i>b </i>to either position “1” or “2” to monitor upstream or downstream traffic, respectively.

0073In certain embodiments, both the downstream and upstream communications traffic may be monitored simultaneously. In alternative embodiments, satellite <b>10</b> may be designed to monitor either upstream or downstream communications traffic; the selection being either on a rotating basis, automatically selected by satellite <b>10</b>, or in response to a command. Satellite <b>10</b> may also be designed to simultaneously monitor a portion, for example half, of the upstream traffic and a portion of the downstream traffic; the particular portion being selected either on a rotating basis, automatically selected by satellite <b>10</b>, or in response to a command.

Real-Time Performance Measurement

0074Some satellites utilize beams that transmit signals to a national or continental size region. For these satellites, a satellite operator may monitor the performance of all of the signals being transmitted by the satellite from a single site within these national or continental regions. In contrast, a spot-beam satellite may have tens, hundreds, or even more beams, with each beam directed to a smaller region. For these spot-beam satellites, it may be difficult for a satellite operator to establish, operate, and maintain monitoring facilities within each of these regions.

0075In certain embodiments, rather than monitoring downstream and upstream communications traffic for an operational gateway <b>20</b> through the use of monitoring facilities located in many or all of these regions, a utility gateway <b>250</b> may be utilized to monitor the corresponding downstream (satellite to end-user) and upstream (end-user to satellite) communication traffic associated with an operational gateway <b>20</b>. In this manner, a utility gateway <b>250</b> may be utilized to emulate end-users and perform two-way communications between these emulated end-users and the associated operational gateway <b>20</b>.

0076In certain embodiments, a number of end-users may be emulated at utility gateway <b>250</b> for test and monitoring purposes. In certain embodiments, connectivity, speed, quality of service, and other performance measurements may be determined for the operational gateway <b>20</b> being evaluated based on an evaluation of communications signals, test signals, or simulated user terminal signals. In certain embodiments, a suite of end-user terminals may be emulated and connected, logically or by channel and band, into every beam, carrier, or group of actual end-users being serviced by the operational gateway <b>20</b>. In this manner, the satellite operator may obtain real-time performance measurements as if the monitoring equipment were remotely located in each spot beam coverage region <b>30</b>. In certain embodiments, an ability to monitor the signals in all, or substantially all, of spot beams <b>40</b> across an entire network from a single site may greatly improve capabilities to manage network performance.

0077<figref idref="DRAWINGS">FIG. 10C</figref> illustrates example components that may be used to implement a utility gateway <b>250</b> for use in performance measurement. <figref idref="DRAWINGS">FIG. 10C</figref> is intended to illustrate only those components which may be included in payload <b>80</b> to implement a utility gateway <b>250</b> for use in performance measurement, according to certain embodiments. In various embodiments, the components illustrated in <figref idref="DRAWINGS">FIG. 10C</figref> may be used together with some or all of the components illustrated in <figref idref="DRAWINGS">FIG. 4</figref>, <b>5</b>, or <b>6</b>A through <b>6</b>B. In the embodiment shown, the example components may be utilized to monitor downstream and upstream communication traffic associated with a selected operational gateway <b>20</b>, without disrupting the communication traffic to and/or from the selected operational gateway <b>20</b>. In the embodiment shown, the example components allow utility gateway <b>250</b> to selectively monitor communications traffic associated with either gateway <b>20</b><i>a </i>or gateway <b>20</b><i>b. </i>In alternative embodiments, components may be similarly configured to allow a particular gateway <b>250</b> to selectively monitor communications traffic associated with a different number of operational gateways <b>20</b>. As shown in <figref idref="DRAWINGS">FIG. 10C</figref>, when switches <b>202</b> are set to position “1,” the communications signals transmitted by gateway <b>250</b> through beam <b>60</b><i>c </i>and received by feed horn <b>246</b> are received by receiver <b>248</b> and coupled to the communications signal input to transmitter <b>232</b> for transmission through feed horn <b>236</b> to operational gateway <b>20</b><i>a. </i>Similarly, communications signals transmitted from gateway <b>20</b><i>a </i>through beam <b>60</b><i>a </i>are received by receiver <b>238</b> and directed to transmitter <b>242</b> using directional coupler <b>240</b>. From transmitter <b>242</b>, the signals are further directed through beam <b>60</b><i>c </i>to gateway <b>250</b>. Through the use of these components, with switches <b>202</b> set to position “1,” gateway <b>250</b> may emulate a user terminal <b>32</b> and measure the connectivity, speed, quality of service, and other performance metrics over a complete communications path similar to the path utilized by an end-user at a user terminal <b>32</b>. As shown in <figref idref="DRAWINGS">FIG. 10C</figref>, by setting switches <b>202</b> to position “2,” gateway <b>250</b> may be utilized to emulate end-users associated with gateway <b>20</b><i>b. </i>In certain embodiments, gateway <b>250</b> may be allowed to emulate end-users associated with various operational gateways <b>20</b> on a rotating basis, according to an automatically selected pattern, or in response to a command.

Earth-Based Power Control Beacon

0078A beacon transmitter may be utilized on satellite <b>10</b> to transmit a known signal down to earth at a carefully controlled constant power level. By monitoring the beacon signal down on the earth, the signal path losses between the satellite and the earth station of interest may be determined.

0079A satellite operator may monitor satellite beacon power to maintain their earth-to-space signals, such that the signals arrive at the satellite at a constant power level. If the satellite beacon power changes, due to rain or other phenomena along the line of sight, the satellite operator may adjust his earth station transmitter power by a corresponding amount to maintain a constant level at the satellite. Maintaining a constant signal power level at the satellite in this manner may reduce interference and improve satellite performance.

0080Through the use of a satellite beacon a satellite operator may control the earth-based transmitters used to send signals up to satellite <b>10</b>, but they provide little ability to control the transmitter power level on board a satellite <b>10</b>. On spot-beam satellite <b>10</b>, the communications link from satellite <b>10</b> down to a gateway earth station <b>20</b> may consist of hundreds or thousands of subscriber signals. By controlling the power level of a satellite-to-gateway transmitter the performance of satellite <b>10</b> may be improved.

0081In certain embodiments, the power level of a satellite-to-gateway transmitter may be controlled through the use of an earth-based beacon transmitter. This earth-to-space beacon signal may be received at satellite <b>10</b> and transmitter power on satellite <b>10</b> may be dynamically and/or automatically adjusted based on the beacon signal power received. In certain embodiments, the use of dynamic and/or automatically adjusted transmitter power may allow a transmitter to be operated at low power in low-loss conditions and then operated at increased power levels only when the loss along the propagation path increases. In certain embodiments, the use of dynamic and/or automatically adjusted transmitter power may allow for (1) lower average power consumption on the satellite; (2) less self-generated interference or distortion in low-loss conditions; and (3) ability to rapidly increase satellite transmitter power when the loss along the propagation path increases to reduce outages.

0082<figref idref="DRAWINGS">FIG. 11</figref> illustrates example components that may be used to control transmitter power level on board satellite <b>10</b>. <figref idref="DRAWINGS">FIG. 11</figref> is intended to illustrate only those components which may be included in payload <b>80</b> to implement an earth-based power control beacon, according to certain embodiments. In various embodiments, the components illustrated in <figref idref="DRAWINGS">FIG. 11</figref> may be used together with some or all of the components illustrated in <figref idref="DRAWINGS">FIG. 4</figref>, <b>5</b>, or <b>6</b>A through <b>6</b>B. In the embodiment shown in <figref idref="DRAWINGS">FIG. 11</figref>, an earth-based beacon signal may be received through feed horn <b>266</b> and directed to beacon receiver <b>268</b>. Beacon receiver <b>268</b> is coupled to controller <b>260</b> and information or signals from beacon receiver <b>268</b> may be used as input to controller <b>260</b> which controls the power level for transmitter <b>262</b>. In this way, the earth-based beacon may be used to control the signal power transmitted through beam <b>60</b> to gateway <b>20</b> within gateway region <b>50</b>. In the embodiment shown, feed horn <b>266</b> is focused toward gateway region <b>50</b> to receive a beacon signal from an earth-based beacon located within gateway region <b>50</b>. In this embodiment, both the earth-based beacon and gateway <b>20</b> would be co-located within the same gateway region <b>50</b>. By locating the earth-based beacon in proximity to gateway <b>20</b>, any signal loss along the propagation path from the earth-based beacon to satellite <b>10</b> could be used to approximate the correlating signal loss between satellite <b>10</b> and gateway <b>20</b>. However, in alternative embodiments, one or more earth-based beacons may be located outside gateway region <b>50</b>.

0083<figref idref="DRAWINGS">FIG. 12</figref> illustrates an example method <b>300</b> for use in controlling transmitter power level on board satellite <b>10</b>. At step <b>302</b>, satellite <b>10</b> receives a beacon signal having an amplitude (R). At step <b>304</b>, the amplitude of the received beacon signal (R) is compared to a target amplitude (T). At step <b>306</b>, if the amplitude of the received beacon signal (R) minus target amplitude (T) is greater than zero, then at step <b>308</b> the gain for the signal transmitter is decreased. If at step <b>310</b>, the amplitude of received beacon signal (R) minus target amplitude (T) is less than zero, then the gain for the transmitter is increased. As shown in <figref idref="DRAWINGS">FIG. 12</figref>, according to certain embodiments, if the amplitude of received beacon signal (R) is equal to target amplitude (T), then no change is made to the transmitter gain. Through the use of method <b>300</b>, the transmitter power level for satellite <b>10</b> may be controlled by comparing the amplitude of a received beacon signal to a target amplitude.

Distortion Based Power Control

0084In some satellite transmitters, particularly satellite transmitters used to amplify multiple simultaneous signals distributed across the bandwidth of interest, the power levels at which the transmitter provides acceptable performance may be half or less than half of the transmitter's maximum power. One way to control the power level of a satellite transmitter is to perform an automatic level control (ALC) function for the signal prior to the input to the transmitter, such that fluctuations in the input signal level are effectively negated and the transmitter is maintained at a selected operating point relative to the transmitter's maximum power.

0085On a spot-beam satellite, the number of upstream signals, the power levels of those signals, and therefore the total signal power at the input to the satellite-to-gateway transmitter on the satellite may be determined by end-user loading. During off-peak periods, the number of signals at the input to the satellite transmitter may be nearly zero; while during peak periods, the number of signals at the input to the satellite transmitter may be hundreds or thousands. The use of ALC techniques may be insufficient when the variation in the number of signals and signal power at the transmitter input is large. For example, even under a fixed gain approach, the satellite amplifier power level may vary considerably as a function of the number of signals present.

0086In certain embodiments, a satellite transmitter may be maintained at a constant or substantially constant distortion level. In particular embodiments, constant distortion level may be achieved by injecting a reference signal into the transmitter input and monitoring the resulting distortion associated with that reference signal. In these embodiments, total input power to the transmitter may be adjusted up or down to maintain the distortion at a constant or substantially constant level. In certain embodiments, a reference signal may be injected into the transmitter input, at the edge of the band or in a particular band reserved for such purposes. For example, the reference signal may be selected to be in a range intended to cause little or no interference with the satellite-to-gateway signals. In certain embodiments, the use of distortion based power control may allow the satellite transmitter to operate efficiently at its maximum allowable power level (relative to acceptable distortion of the satellite-to-gateway signals) across a very wide range of variation in number and power levels of input signals.

0087<figref idref="DRAWINGS">FIG. 13</figref> illustrates example components that may be used to control signal power based on distortion. <figref idref="DRAWINGS">FIG. 13</figref> is intended to illustrate only those components which may be included in payload <b>80</b> to control signal power based on distortion. In various embodiments, the components illustrated in <figref idref="DRAWINGS">FIG. 13</figref> may be used together with some or all of the components illustrated in <figref idref="DRAWINGS">FIG. 4</figref>, <b>5</b>, or <b>6</b>A through <b>6</b>B. As shown in <figref idref="DRAWINGS">FIG. 13</figref>, test signal source <b>270</b> generates test signal <b>314</b> that is coupled to an input signal through directional coupler <b>272</b>. The test signal <b>314</b>, together with the input signal, is directed through controller <b>280</b> and to transmitter <b>282</b>. After passing through transmitter <b>282</b>, which amplifies the input signal and test signal <b>314</b>, a portion of the output signal (identified as distorted signal <b>316</b>) is extracted using directional coupler <b>272</b> and passed to filter <b>274</b>. Filtered signal <b>318</b> leaves filter <b>274</b> and is used as an input to controller <b>280</b>. Controller <b>280</b> operates to adjust the gain for transmitter <b>282</b>.

0088<figref idref="DRAWINGS">FIG. 14</figref> illustrates an example method <b>320</b> for distortion based control of signal power. At step <b>322</b>, a test signal is generated. At step <b>324</b>, the test signal is coupled to a communications signal. At step <b>326</b>, the communications signal and the test signal are amplified at an established gain level (G). At step <b>328</b>, the amplified signals are filtered to isolate distortion associated with the test signal. At step <b>330</b>, the amplitude of the isolated distortion (D) is compared to a target distortion level (T). If, at step <b>332</b>, the isolated distortion (D) minus the target distortion level (T) is greater than zero, then at step <b>334</b>, the gain is decreased. If at step <b>336</b>, the isolated distortion (D) minus the target distortion level (T) is less than zero, then at step <b>338</b>, the gain is increased. Through the use of example method <b>320</b>, the signal power transmitted by satellite <b>10</b> may be controlled based on distortion levels.

0089<figref idref="DRAWINGS">FIGS. 15A through 15C</figref> illustrate example signals associated with distortion based control of signal power. According to a particular embodiment, as shown in <figref idref="DRAWINGS">FIG. 15A</figref>, two narrowband tones of approximately equal power may be injected (along with the other transmitter input signals) into a satellite transmitter. A small sample of the transmitter output signal may be collected and the relative power level of the intermodulation product between these two tones may be monitored. The power level of the intermodulation product is a measure of the distortion being caused by the satellite transmitter. If the relative power level of the intermodulation product is less than the specified target, the gain prior to the transmitter is increased such that the input signal level increases causing the output power of the transmitter to increase. Similarly, if the relative power level of the intermodulation product is greater than the specified target, the gain prior to the transmitter is decreased such that the input signal level decreases causing the output power of the transmitter to decrease. This process is designed to maintain the power level of the intermodulation product at or near the specified target, ensuring that the transmitter operates at the highest possible power level that does not cause an unacceptable level of distortion.

0090Variations on this approach may include (1) monitoring the distortion of the actual transmitted signals rather than injecting a test signal; and (2) creating a narrowband notch in the bandwidth of the signal at the input to the transmitter, either in the transmitted bandwidth or just outside the transmitted bandwidth, and measuring transmitter distortion by monitoring to what extent the notch is filled by the transmitter.

0091Although the present invention has been described with several embodiments, a plenitude of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, variations, alterations, transformations, and modifications as fall within the scope of the appended claims.