Patent Publication Number: US-2022225111-A1

Title: Architecture for Simultaneous Spectrum Usage by Air-to-Ground and Terrestrial Networks

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 17/067,120 filed on Oct. 9, 2020, which is a continuation of U.S. application Ser. No. 16/271,082 filed Feb. 8, 2019, which is a continuation of U.S. application Ser. No. 16/039,843 filed on Jul. 19, 2018, which is a continuation of U.S. application Ser. No. 15/637,460 filed Jun. 29, 2017, which is a continuation of U.S. application Ser. No. 15/287,914 filed Oct. 7, 2016 (which issued on Aug. 8, 2017 as U.S. Pat. No. 9,730,077), which is a continuation of U.S. application Ser. No. 14/595,512 filed Jan. 13, 2015 (which issued on Nov. 8, 2016 as U.S. Pat. No. 9,491,635), the entire contents of which are hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Example embodiments generally relate to wireless communications and, more particularly, relate to techniques for enabling dual usage of spectrum by wireless air-to-ground (ATG) networks and terrestrial networks in the same geographic area. 
     BACKGROUND 
     High speed data communications and the devices that enable such communications have become ubiquitous in modern society. These devices make many users capable of maintaining nearly continuous connectivity to the Internet and other communication networks. Although these high speed data connections are available through telephone lines, cable modems or other such devices that have a physical wired connection, wireless connections have revolutionized our ability to stay connected without sacrificing mobility. 
     However, in spite of the familiarity that people have with remaining continuously connected to networks while on the ground, people generally understand that easy and/or cheap connectivity will tend to stop once an aircraft is boarded. Aviation platforms have still not become easily and cheaply connected to communication networks, at least for the passengers onboard. Attempts to stay connected in the air are typically costly and have bandwidth limitations or high latency problems. Moreover, passengers willing to deal with the expense and issues presented by aircraft communication capabilities are often limited to very specific communication modes that are supported by the rigid communication architecture provided on the aircraft. 
     As improvements are made to network infrastructures to enable better communications with in-flight receiving devices of various kinds, one prospect that may be considered is the dedication of some amount of radio frequency (RF) spectrum to in-flight communication. However, RF spectrum is extremely expensive due to the massive demands on this relatively limited resource. Accordingly, alternatives to the exclusive designation of a portion of RF spectrum to in-flight communication may be of interest. 
     BRIEF SUMMARY OF SOME EXAMPLES 
     The continuous advancement of wireless technologies offers new opportunities to provide wireless coverage for aircraft in-flight without dedicating RF spectrum to such coverage. In this regard, for example, by employing various interference mitigation strategies, spectrum reuse may be employed. Some example embodiments may provide interference mitigation techniques that may allow spectrum reuse within a given area so that both terrestrial networks and air-to-ground (ATG) networks can coexist in the same geographical area and employ the same spectrum. 
     In one example embodiment, a network for providing air-to-ground (ATG) wireless communication in various communication volumes or cells is provided. The network may include an in-flight aircraft including an antenna assembly, a plurality of ATG base stations, and a plurality of terrestrial base stations. Each of the ATG base stations defines a corresponding radiation pattern, and the ATG base stations are spaced apart from each other to define at least partially overlapping coverage areas to communicate with the antenna assembly in an ATG communication layer defined between a first altitude and a second altitude. The terrestrial base stations are configured to communicate primarily in a ground communication layer below the first altitude to provide services independently of or in cooperation with the ATG base stations. The terrestrial base stations and the ATG base stations are each configured to communicate using the same radio frequency (RF) spectrum in the ground communication layer and ATG communication layer, respectively. 
     In another example embodiment, a method of selecting antenna elements of an antenna assembly for communicating in an ATG network and compensating for aircraft movement (e.g., pitch and roll) is provided. The method may include determining an expected relative position of an ATG base station relative to an in-flight aircraft, selecting an antenna element to employ for communication with the ATG base station based on the expected relative position, receiving an indication of a change to the dynamic position information (e.g., where the change is indicative of at least a change in the pitch or roll of the aircraft), and adjusting the selected antenna element to compensate for the change to the dynamic position information. 
     In another example embodiment, an antenna assembly for an aircraft is provided. The antenna assembly may be capable of communicating with ATG base stations of an ATG wireless communication network. The antenna assembly may include a plurality of antenna elements, at least one of which is tiltable to maintain the antenna assembly oriented toward a focus region responsive to in-flight maneuvering of the aircraft. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1  illustrates a top view of an example network deployment providing air-to-ground (ATG) wireless communication coverage areas in accordance with an example embodiment; 
         FIG. 2  illustrates an aspect of an example network deployment of base stations providing overlapping cell coverage areas to achieve coverage up to a predetermined altitude in accordance with an example embodiment; 
         FIG. 3  illustrates a side view of a layered approach to providing wireless communication to in-flight aircraft while minimizing interference between the layers in accordance with an example embodiment; 
         FIG. 4  illustrates a side panel element disposed on an in-flight aircraft in accordance with an example embodiment; 
         FIG. 5  illustrates a functional block diagram of antenna elements of an example embodiment; 
         FIG. 6  illustrates a panel antenna vertical pattern in accordance with an example embodiment; 
         FIG. 7  illustrates a functional block diagram of a controller for selecting antenna elements and compensating for aircraft movement to keep antenna elements oriented toward a focus region in accordance with an example embodiment; 
         FIG. 8  illustrates a block diagram of a method of communicating in an ATG network in accordance with an example embodiment; 
         FIG. 9  illustrates a side view of a layered approach to providing wireless communication to in-flight aircraft including a high altitude service layer in accordance with an example embodiment; 
         FIG. 10  illustrates a full duplex radio architecture in accordance with a first example; 
       and 
         FIG. 11  illustrates a full duplex radio architecture in accordance with a second option. 
     
    
    
     DETAILED DESCRIPTION 
     Some example embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all example embodiments are shown. Indeed, the examples described and pictured herein should not be construed as being limiting as to the scope, applicability or configuration of the present disclosure. Rather, these example embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals may be used to refer to like elements throughout. Furthermore, as used herein, the term “or” is to be interpreted as a logical operator that results in true whenever one or more of its operands are true. 
     Some example embodiments described herein provide architectures for improved air-to-ground (ATG) wireless communication performance. In this regard, some example embodiments may provide for the use of base stations on the ground having antenna structures configured to generate a wedge-shaped cell inside which directional beams may be focused. The wedge shaped cells may be spaced apart from each other and arranged to overlap each other in altitude bands to provide coverage over a wide area and up to the cruising altitudes of in-flight aircraft. The wedge shaped cells may therefore form overlapping wedges that extend out toward and just above the horizon. Thus, the size of the wedge shaped cells is characterized by increasing altitude band width (or increasing vertical span in altitude) as distance from the base station increases. Meanwhile, the in-flight aircraft may employ antennas that are capable of focusing toward the horizon and just below the horizon such that the aircraft generally communicate with distant base stations instead of base stations that may be immediately below or otherwise proximal (e.g., nearest) the aircraft. In fact, for example, an aircraft directly above a base station would instead be served by a more distant base station as the aircraft antennas focus near the horizon, and the base station antennas focus above the horizon. This leaves the aircraft essentially unaffected by the communication transmitters that may be immediately below the aircraft. Thus, for example, the same RF spectrum, and even the same specific frequencies the aircraft is using to communicate with a distally located base station may be reused by terrestrial networks immediately below the aircraft. As a result, spectrum reuse can be practiced relative to terrestrial wireless communication networks and ATG wireless communication networks in the same geographic area. 
     A plurality of base stations may be distributed to provide a corresponding plurality of adjacent wedge shaped cell coverage areas. Each wedge shaped cell may define a coverage area that extends between an upper and lower altitude limit and the upper and lower altitude limits may increase (substantially linearly) as distance from the transmitters forming the wedge shaped cell increases. Thus, the coverage areas may be defined between altitude bands that increase in size and altitude as they proceed away from the transmission site. A plurality of sectors within each wedge shaped cell may combine to form the wedge shaped cell. In some cases, six sectors may be employed to cover about 30 degrees each for a total of 180 degrees of azimuth coverage provided by each wedge shaped cell. The cell coverage area may therefore be substantially semicircular in the horizontal plane, and can be provided by multiple antennas each providing a wedge shaped sector over corresponding portions of the semicircular azimuth. The base stations can be deployed as substantially aligned in a first direction while offset in a second direction. For example, the base stations can also be deployed in the first direction at a first distance to provide coverage overlapping in elevation to achieve coverage over the predetermined altitude, and within a second distance in the second direction based on an achievable coverage area distance of the sectors. In some embodiments, any number of sectors may be employed for as much as  360  degrees of coverage. 
       FIG. 1  illustrates a top view of a network  100  of deployed base stations for providing ATG wireless communication coverage as described above. Network  100  includes various base stations providing substantially semicircular cell coverage areas. The cell coverage areas are each depicted in two portions. For example, the cell coverage area for a first base station is shown as similarly patterned portions  102  and  104 . The portions  102  and  104  represent a single continuous cell coverage area over a horizontal plane; however,  FIG. 1  depicts intervening portion  108  of another cell coverage area as providing overlapping coverage to achieve continuous coverage up to a predetermined altitude, as described further herein. Portion  102  is shown to represent the initial cell coverage area from the location of the corresponding base station out to an arbitrary distance for illustrative purposes; it is to be appreciated that this portion  102  also includes the overlapping coverage of portion  108  of another cell coverage area to achieve coverage at the predetermined altitude. Moreover, the coverage area represented by portions  106  and  108  may extend beyond boundary  130  of coverage area portion  104 ; the coverage areas are limited in the depiction to illustrate at least one point where the bordering coverage areas are able to provide ATG wireless communication coverage at the predetermined altitude. Further, the base stations are not depicted for ease of explanation, but it is to be appreciated that the base stations can be located such to provide the cell coverage area indicated by portions  102  and  104 , portions  106  and  108 , portions  110  and  112 , etc. 
     The cell coverage areas  102 / 104  and  106 / 108  can be provided by respective base stations in a first base station array, where the base stations of one or more base station arrays are substantially aligned in a first direction  120  (as depicted by the representative cell coverage areas). As shown, cell coverage areas  102 / 104  and  106 / 108  project a directional radiation pattern that is oriented in the first direction, and are aligned front to back along the first direction. Such alignment can be achieved by substantially aligning base stations in the base station array to provide the substantially aligned cell coverage areas, antenna rotation to achieve alignment in the cell coverage areas in the first direction  120 , and/or the like. As described, in this regard, a first base station that provides cell coverage area  102 / 104  can be overlapped by at least a cell coverage area  106 / 108  of a second base station in front of the first base station in the first direction  120 . For example, a base station, or antennas thereof, can provide wedge shaped cell coverage areas defined by multiple elevation angles employed by antennas transmitting signals to achieve a predetermined altitude by a certain distance from the base station. Thus, overlapping the cell coverage areas in the first direction  120  allows cell coverage area  106 / 108  to achieve the predetermined altitude for at least the certain distance between the base station providing cell coverage area  102 / 104  and a point along line  130  where the cell coverage area  102 / 104  achieves the predetermined altitude. 
     In addition, base stations in the first base station array providing cell coverage areas  102 / 104  and  106 / 108  can be spaced apart (i.e., located at random, fixed or predetermined intervals) in a second direction  122  from base stations of a second base station array, which can provide additional cell coverage areas  110 / 112 ,  114 / 116 , etc., aligned in the first direction  120 . The first and second base station arrays can extend substantially parallel to each other in the first direction  120 . In addition, base stations of the second base station array can be offset from base stations of the first base station array in the first direction  120  (as depicted by the representative cell coverage areas). The second direction  122  can be substantially perpendicular to the first direction  120  in one example. In this example, the first and second base station arrays can be offset to provide the offsetting of respective cell coverage areas (e.g., the offset shown between cell coverage areas  102 / 104  and  110 / 112 ), and any other coverage areas of the base station arrays aligned in the first direction  120 . 
     The first and second base station arrays can be spaced apart at a greater distance in the second direction  122  than base stations within the respective arrays spaced apart in the first direction  120 . For example, the base stations can be spaced in the second direction  122  according to an achievable coverage distance of the base station providing the cell coverage areas. Because the base stations providing cell coverage areas  102 / 104  and  106 / 108  in the first base station array are aligned in the first direction  120  such that cell coverage area  106 / 108  provides overlapping coverage to cell coverage area  102 / 104  to achieve the predetermined altitude, the base station arrays themselves can be separated based on the achievable distance of the respective cell coverage areas  102 / 104  and  110 / 112 . In this regard, no substantial overlapping is needed between the boundaries of cell coverage areas  102 / 104  and  110 / 112  provided by base stations of adjacent base station arrays to reach the predetermined altitude since the altitude deficiencies near the respective base stations are covered by cell coverage areas of base stations in the base station array aligned in the first direction  120 . 
     Moreover, offsetting the base stations providing the various cell coverage areas over the second direction  122  can allow for further spacing in the first direction  120  and/or second direction  122  as the end portions of one cell coverage area in the horizontal plane can abut to a middle portion of another cell coverage area from a base station in an adjacent base station array to maximize the distance allowed between the cell coverage areas while maintaining continuous coverage, which can lower the number of base stations necessary to provide coverage over a given area. In one example, the spacing in the second direction  122  can be more than twice the spacing in the first direction  120 , depending on the coverage distance of the cell coverage areas and the distance over which it takes a cell coverage area to reach the predetermined altitude. 
     As depicted, the spacing of a first distance between base stations in a given base station array can be indicated as distance  140  in the first direction  120 . The spacing of a second distance between base station arrays in the second direction  122  can be indicated as distance  142 . Moreover, the offset between the base station arrays can be indicated as a third distance  144 . In one specific example, the distance  140  can be near 100 kilometers (km), where distance  142  between the base stations providing cell coverage area  102 / 104  can be 300 km or more. In this example, the achievable cell coverage areas can be at least 200 km from the corresponding base station in the direction of the transmitted signals that form the coverage areas or related sectors thereof, as a slant distance from a base station within one array to the intersecting coverage from a base station in the second array. Moreover, in this example, the distance  144  can be around 75 km. 
     In an example, the base stations providing cell coverage areas  102 / 104 ,  106 / 108 ,  110 / 112 , etc. can each include respective antenna arrays defining a directional radiation pattern oriented in the first direction. The respective antenna arrays can include multiple antennas providing a sector portion of the radiation pattern resulting in a coverage area that is wedge shaped in the vertical plane. For example, the cell coverage area provided by each antenna can have first and second elevation angles that exhibit an increasing vertical beam width, or span, in the vertical plane, and fills a portion of an azimuth in the horizontal plane. Using more concentrated signals that provide smaller portions of the azimuth can allow for achieving further distance and/or increased elevation angles without increasing transmission power. In the depicted example, the cell coverage areas defined by the antenna arrays include six substantially 30 degree azimuth sectors that are substantially adjacent to form a directional radiation pattern extending substantially 180 degrees in azimuth centered on the first direction to define the semicircular coverage area. Each sector can be provided by an antenna at the corresponding base station, for example. Moreover, in one example, the base station can have a radio per antenna, a less number of radios with one or more switches to switch between the antennas to conserve radio resources, and/or the like, as described further herein. It is to be appreciated that additional or a less number of sectors can be provided. In addition, the sectors can have an azimuth more or less than 30 degrees and/or can form a larger or smaller total cell coverage area azimuth than the depicted semicircular cell coverage area. 
     In yet other examples, the network  100  can implement frequency reuse of one, three, four, seven, or other suitable configurations (e.g., using formula N=i{circumflex over ( )}2+j{circumflex over ( )}2+ij where i=# cells over from the original cell and j=# cells down from the original cell) such that nearby base stations can use the same channels in providing the cell coverage areas. For example, a base station providing cell coverage areas  102 / 104  can use a first channel, a base station providing cell coverage area  106 / 108  in the same base station array can use a second channel, and a base station providing cell coverage area  114 / 116  can use a third channel. Similarly, an adjacent group of three base stations providing cell coverage areas in a different base station array can use the same channels, etc. It is to be appreciated that other frequency reuse patterns and/or number of reuse factors can be utilized in this scheme to provide frequency diversity between adjacent cell coverage areas. 
     In a further example, a non-traditional frequency reuse scheme of two may be employed by the system. The wedge shape of the base station coverage areas in combination with the directional aircraft antennas effectively achieve a reuse of four with only two channel sets. In this example, an array of base stations alternate channel assignment between two channels in the array, with Channel A on a first base station, Channel B on a second base station, Channel A on a third, etc. The second array similarly alternates between the two channels, with Channel A offset from the similar Channel A base station in the first array. The overlap area between the two arrays will occasionally present the same co-channel frequency within the overlap area, but the angular directions of arrival from the two co-channel base stations are sufficiently distinct such that the aircraft antenna will focus on the closer base station, resulting in an aircraft antenna null in the direction of the second, weaker base station. Thus, a non-traditional frequency reuse is achieved through the design of the wedge-shaped base station coverage and the design of the directional aircraft antennas. 
     Furthermore, in an example deployment of network  100 , the first direction  120  and/or second direction  122  can be, or be near, a cardinal direction (e.g., north, south, east, or west), an intermediate direction (e.g., northeast, northwest, southeast, southwest, north-northeast, east-northeast, etc.), and/or the like on a horizontal plane. In addition, the network  100  can be deployed within boundaries of a country, boundaries of an air corridor across one or more countries, and/or the like. In one example, cell coverage area  106 / 108  can be provided by an initial base station at a border of a country or air corridor. In this example, a base station providing cell coverage area  106 / 108 ,  110 / 112 , and/or additional cell coverage areas at the border, can include one or more patch antennas to provide coverage at the predetermined altitude from the distance between the base station to the point where the respective cell coverage area  106 / 108 ,  110 / 112 , etc. reaches the predetermined altitude. For example, the one or more patch antennas can be present behind the cell coverage areas  106 / 108 ,  110 / 112 , etc., and/or on the base stations thereof (e.g., as one or more antennas angled at an uptilt and/or parallel to the horizon) to provide cell coverage up to the predetermined altitude. 
       FIG. 2  illustrates an example network  200  for providing overlapping cells (e.g., in the vertical direction) to facilitate ATG wireless communication coverage at least at a predetermined altitude. Network  200  includes base stations  202 ,  204 , and  206  that transmit signals for providing the ATG wireless communications. Base stations  202 ,  204 , and  206  can each transmit signals that exhibit a radiation pattern defined by a first and second elevation angle such to achieve a predetermined altitude. In this example, base stations  202 ,  204 , and  206  provide respective wedge shaped cell coverage areas  212 ,  214 , and  216  that are offset in origin and overlap in the vertical direction. The base stations  202 ,  204 , and  206  can be deployed as substantially aligned in a first direction  120  as part of the same base station array, as described above, or to otherwise allow for aligning the cell coverage areas  212 ,  214 , and  216  in the first direction, such that cell coverage area  212  can overlap cell coverage area  214  (and/or  216  at a different altitude range in the vertical plane), cell coverage area  214  can overlap cell coverage area  216 , and so on. This can allow the cell coverage areas  212 ,  214 , and  216  to achieve at least a predetermined altitude (e.g., 45,000 feet (ft)) for a distance defined by the various aligned base stations  202 ,  204 ,  206 , etc. 
     As depicted, base station  202  can provide cell coverage area  212  that overlaps cell coverage area  214  of base station  204  to facilitate providing cell coverage up to 45,000 ft near base station  204  for a distance until signals transmitted by base station  204  reach the predetermined altitude of 45,000 ft (e.g., near point  130 ), in this example. In this example, base station  204  can be deployed at a position corresponding to the distance between which it takes cell coverage area  214  of base station  204  to reach the predetermined altitude subtracted from the achievable distance of cell coverage area  212  of base station  202 . In this regard, there can be substantially any number of overlapping cell coverage areas of different base stations to reach the predetermined altitude based on the elevation angles, the distance it takes to achieve a vertical beam width at the predetermined altitude based on the elevation angles, the distance between the base stations, etc. 
     In one specific example, the base stations  202 ,  204 , and  206  can be spaced apart by a first distance  140 , as described. The first distance  140  can be substantially 100 km along the first direction  120 , such that base station  204  is around 100 km from base station  202 , and base station  206  is around 200 km from base station  202 . Further, in an example, an aircraft flying between base station  206  and  204  may be covered by base station  202  depending on its altitude, and in one example, altitude can be used in determining whether and/or when to handover a device on the aircraft to another base station or cell provided by the base station to provide for uninterrupted handover of receivers on an aircraft. 
     Moreover, as described in some examples, base stations  202 ,  204  and  206  can include an antenna array providing a directional radiation pattern oriented along the first direction  120 , as shown in  FIG. 1 , where the directional radiation pattern extends over a predetermined range in azimuth centered on the first direction  120 , and extends between the first elevation angle and the second elevation angle of the respective coverage areas  212 ,  214 , and  216  over at least a predetermined distance to define the substantially wedge shaped radiation pattern. In this regard,  FIG. 2  depicts a side view of a vertical plane of the base stations  202 ,  204 , and  206 , and associated coverage areas  212 ,  214 , and  216 . Thus, in one example, base station  202  can provide a cell coverage area  212  that is similar to cell coverage area  106 / 108  in  FIG. 1  in a horizontal plane, and base station  204  can provide a cell coverage area  214  similar to cell coverage area  102 / 104  in  FIG. 1 . Moreover, as described, direction  120  can correlate to a cardinal direction, intermediate direction, and/or the like. In addition, in a deployment of network  200 , additional base stations can be provided in front of base station  206  along direction  120  until a desired coverage area is provided (e.g., until an edge of a border or air corridor is reached). 
     As mentioned above, the establishment of an ATG network with base stations deployed and configured in the manner described in  FIGS. 1 and 2  provides the ability to create a layered approach to covering a given area, in which the layers define altitude bands in which distally located base stations provide coverage for aircraft with fore/aft and side looking antenna arrays that are essentially shielded from potentially interfering transmitters directly below them. Accordingly, for example, a bottom layer (i.e., closest to the ground) may reuse radio spectrum already employed in the altitude bands defined in the layer or layers above. Frequency reuse can therefore be employed for a given region in distinct altitude bands. 
       FIG. 3  illustrates an example network architecture for providing overlapping cells with layered altitude bands to facilitate ATG wireless communication coverage with RF spectrum that can be reused by a terrestrial network.  FIG. 3  shows only two dimensions (e.g., an X direction in the horizontal plane and a Z direction in the vertical plane), however it should be appreciated that the wedge architecture of the ATG network may be structured to extend coverage also in directions into and out of the page (i.e., in the Y direction). Although  FIG. 3  is not drawn to scale, it should be appreciated that the wedge shaped cells generated by the base stations for the ATG portion of the network architecture are configured to have a much longer horizontal component than vertical component. In this regard, the wedge shaped cells may have a horizontal range on the order of dozens to nearly or more than 100 miles. Meanwhile, the vertical component expands with distance from the base stations, but is in any case typically less than about 8 miles (e.g., about 45,000 ft). 
     As shown in  FIG. 3 , a terrestrial network component of the architecture may include one or more terrestrial base stations  300 . The terrestrial base stations  300  may generally transmit terrestrial network emissions  310  to serve various fixed or mobile communication nodes (e.g., UEs) and other wireless communication devices dispersed on the ground. The terrestrial base stations  300  may be operably coupled to terrestrial backhaul and network control components  315 , which may coordinate and/or control operation of the terrestrial network. The terrestrial backhaul and network control components  315  may generally control allocation of RF spectrum and system resources, and provide routing and control services to enable the UEs and other wireless communication devices of the terrestrial network to communicate with each other and/or with a wide area network (WAN) such as the Internet. 
     The UEs of the terrestrial network may also transmit their own terrestrial network emissions, which may create the possibility for generation of a substantial amount of communication traffic in a ground communication layer  320  extending from the ground to a predetermined minimum altitude  325  above which only receivers on in-flight aircraft  330  are present. The in-flight aircraft  330  may operate in an ATG communication layer  335  that may extend from one or two miles in altitude up (e.g., the predetermined minimum altitude  325 ) to as far as about 8 miles in altitude (e.g., a predetermined maximum altitude  340 ). While, the predetermined minimum altitude  325  and predetermined maximum altitude  340  may bound a single ATG communication layer or, in the case where multiple ATG wedge shaped cells overlap, multiple ATG communication layers. 
     The architecture may also employ a first ATG base station  350  and a second ATG base station  355 , which are examples of base stations employed as described in the examples of  FIGS. 1 and 2 . Thus, for example, the first ATG base station  350  may be deployed substantially in-line with the second ATG base station  355  along the X axis and may generate a first wedge shaped cell  360  that may be layered on top of a second wedge shaped cell  365  generated by the second ATG base station  355 . When the in-flight aircraft  330  is exclusively in the first wedge shaped cell  360 , the in-flight aircraft  330  may communicate with the first ATG base station  350  using assigned RF spectrum and when the in-flight aircraft  330  is exclusively in the second wedge shaped cell  365 , the in-flight aircraft  330  may communicate with the second ATG base station  355  using assigned RF spectrum. An area of overlap between the first wedge shaped cell  360  and the second wedge shaped cell  365  may provide the opportunity for handover of the in-flight aircraft  330  between the first ATG base station  350  and the second ATG base station  355 , respectively. Accordingly, uninterrupted handover of receivers on the in-flight aircraft  330  may be provided while passing between coverage areas of base stations having overlapping coverage areas as described herein. 
     In an example embodiment, ATG backhaul and network control components  370  may be operably coupled to the first and second ATG base stations  350  and  355 . The ATG backhaul and network control components  370  may generally control allocation of RF spectrum and system resources, and provide routing and control services to enable the in-flight aircraft and any UEs and other wireless communication devices thereon to communicate with each other and/or with a wide area network (WAN) such as the Internet. 
     Given the curvature of the earth and the distances between base stations of the ATG network, the layering of the wedge shaped cells can be enhanced. Additionally, the first ATG base station  350  and the second ATG base station  355  may be configured to communicate with the in-flight aircraft  330  using relatively small, directed beams that are generated using beamforming techniques. The beamforming techniques employed may include the generation of relatively narrow and focused beams. Thus, the generation of side lobes (e.g., radiation emissions in directions other than in the direction of the main beam) that may cause interference with communications in the ground communication layer  320  may be reduced. In some cases, the terrestrial base stations  300 , which are generally only required to transmit in a relatively narrow layer close to the ground, may also be configured to employ antennas and/or arrays that employ side lobe suppression techniques aimed at reducing the amount of potential interference transmitted out of the ground communication layer  320  and into the ATG communication layer  335 . 
     Accordingly, the network architecture itself may help to reduce the amount of cross-layer interference. In this regard, the wedge shaped cell structure focuses energy just above the horizon and leaves a layer on the ground that is usable for terrestrial network operations without significant interference from the ATG base stations, and create a separate higher altitude layer for ATG network communications. Additionally, the use of directional antennas with beamsteering by the ATG base stations, and antennas with side lobe suppression, reduces the amount of interference across these layers. However, as will be described in greater detail below, since all of the equipment in the ATG communication layer  335  with which communication is desired will be on the in-flight aircraft  330 , some embodiments may employ further interference mitigation techniques associated with the antenna assembly  375  provided on the in-flight aircraft  330 . Accordingly, for example, the UEs or other wireless communication devices on or associated with the in-flight aircraft  330  may be communicatively coupled with the first ATG base station  350  or the second ATG base station  355  via the antenna assembly  375  of the in-flight aircraft  330 . In this regard, for example, the antenna assembly  375  may be strategically mounted on the in-flight aircraft  330  and/or the antenna assembly  375  may be operated or controlled in a manner that facilitates interference mitigation as described in greater detail below. 
     By generally minimizing cross-layer interference, the same RF spectrum can be reused in both the ground communication layer  320  and the ATG communication layer  335 . As such, the network architecture of an example embodiment may effectively act as a frequency spectrum doubler in that spectrum that is used in the terrestrial network may be reused by the ATG network with minimal interference therebetween. The base stations serving each respective layer may be distally located relative to each other such that, for example, a serving ATG base station in communication with the in-flight aircraft  330  is geographically located outside a coverage area of each of the terrestrial base stations in a portion of the ground communication layer  320  above which the in-flight aircraft  330  is located. The substantially horizontally focused nature of the ATG base stations ( 350  and  355 ) enables them to be positioned far outside of the region below which the in-flight aircraft  330  is located. The antenna assembly  375  can therefore “look” or otherwise focus its communication efforts away from potentially interfering sources directly below the in-flight aircraft  330 . 
     As mentioned above, cross-layer interference mitigation may be accomplished on the in-flight aircraft  330  by strategic positioning of the antenna assembly  375 . For example, when the antenna assembly  375  is positioned on a vertical stabilizer of the in-flight aircraft  330 , the antenna assembly  375  may generally have a narrow aspect relative to the ground and any transmissions directed from the ground, while providing excellent control of the vertical antenna pattern. Additionally, for certain side mountings of the antenna assembly on the body of the in-flight aircraft  330 , part of the airframe may shield the antenna assembly  375  from terrestrial network emissions  310  generated by terrestrial base stations  300  below the in-flight aircraft  330 . Such shielding may be even more pronounced if, for example, the antenna assembly  375  is positioned on the top or roof of the in-flight aircraft  330 . In these examples, the metal airframe of the in-flight aircraft  330  may act as an extended groundplane. The antenna assembly  375  in either (or both) of these locations may therefore have limited ability to receive transmissions that are not directed from locations with a substantially greater vertical component of distance from the in-flight aircraft  330  than the horizontal component of such distance. In other words, the antenna assembly  375  is shielded from transmitters that are not near the horizon. These locations (e.g., on sides or tops of aircraft) are therefore advantageous for further mitigating cross-layer interference. However, such locations may generally be better for communication with transmitters off to the side of the in-flight aircraft  330 , rather than in front of or behind the in-flight aircraft  330 . For better coverage in front of and behind the in-flight aircraft  330 , positioning of the antenna assembly  375  (or portions or components of the antenna assembly  375 ) on the bottom of the in-flight aircraft  330  may be employed. Thus, fewer antenna elements (e.g., only those on the bottom of the in-flight aircraft  330 ) may need to have sophisticated side lobe suppression techniques employed thereon to facilitate reduction of cross-layer interference. 
     In accordance with the general strategic positioning of the antenna assembly  375  described above, the antenna assembly  375  can be shielded (at least partially) from cross-layer interference by avoiding exposure to transmitters below the in-flight aircraft  330 . However, such strategy implies that the antenna assembly  375  should instead look to transmitters closer to the horizon. This horizon-focused paradigm actually fits quite well with the corresponding layered network architecture described above since the ATG base stations are generally configured to form wedge shaped cells that are focused just above the horizon. Thus, both the ground transmitters and the antenna assembly  375  of an example embodiment are mutually optimized for focusing substantially more energy in the horizontal plane than in the vertical plane. This enhances the ability to maximize spacing between ATG base stations (thereby reducing ATG base station count and network build cost), and simplifies the architecture of the antenna assembly  375  (since natural shielding of the airframe can be employed in some cases). As a result, corresponding ATG base stations focusing energy above the horizon and airborne antenna assemblies focusing energy just below the horizon are mutually optimized to communicate with each other with substantially less interference to worry about from terrestrial network base stations directly (or nearly directly) below the in-flight aircraft  330  even when the same spectrum used by the terrestrial network is reused by the ATG network. 
     In an example embodiment, the antenna assembly  375  may be configured to focus energy in an area from the horizon to about 10 or 15 degrees below the horizon (from the perspective of the in-flight aircraft  330 ).  FIG. 4  illustrates an example of the in-flight aircraft  330  having a side panel element  400  as a portion of the antenna assembly  375 . The side panel element  400  is positioned on the vertical stabilizer, but could alternatively be positioned on a side, top, bottom or other portion of the aircraft. Of note, the side panel element  400  may, in some cases, be embodied in a form other than as a flat array (e.g., as a blade antenna element, a conformal array and/or the like). As can be appreciated from the example of  FIG. 4 , by focusing mainly on areas between the horizon and 10 or 15 degrees below the horizon, the subset of ATG base stations with which communication can be established is somewhat limited. Accordingly, the side panel element  400  may need to be stabilized for ensuring that it remains oriented toward the horizon and just below the horizon even when the aircraft pitches (i.e., moves its head up and down as shown by arrow  410 ) or rolls (i.e., turns side to side as shown by arrow  420 ). 
     In some cases, the amount of pitch and roll that the in-flight aircraft  330  may encounter may be limited based on certain restrictions that are dependent upon altitude, speed and passenger comfort. For example, pitch (i.e., the angle of ascent or descent) may be limited to about 7 degrees above 10,000 ft in altitude. Meanwhile, for example, roll (i.e., the angle of bank right or left during a turn) may be limited to less than 20 degrees above 10,000 ft in altitude and to less than 15 degrees above 20,000 ft in altitude. Accordingly, not only may it be desirable to provide compensation and/or stabilization of the antenna assembly  375  (e.g., the side panel element  400 ), but such compensation and/or stabilization may be dependent upon altitude or other environmental factors. 
     In embodiments in which the antenna assembly  375  is embodied as or includes a panel antenna (e.g., side panel element  400 ), which may include a plurality of sector antennas. In some cases, the panel antenna may be mechanically and/or electrically steered or tilted to provide the compensation and/or stabilization described above. As such, the panel antenna may also be referred to as a steerable matrix antenna.  FIG. 5  shows a block diagram of system components that may be employed in connection with controlling an antenna assembly of an example embodiment. As shown in  FIG. 5 , the antenna assembly  375  may include a left side panel element  402  and a right side panel element  404 . The antenna assembly may also include one or more blade, monopole or other antenna elements such as antenna elements  406  and  408 . In an example embodiment, element  408  may be a blade antenna configured for fore/aft reception. Meanwhile, the right and left side panel elements  404  and  402  may be receive elements for respective sides of the airplane. Antenna element  406  may be a blade antenna with four or more transmission elements, and may have selectable directivity. In some embodiments, such as for large airframes, the receive elements may optionally each be coupled to a remote radio head  430  via one or multiple cables. However, if no remote radio head is employed, the radio itself could perform functions described herein in association with the remote radio head. In some cases, the remote radio head  430  may be distributed in more than one physical location (as shown by distributed elements (DEs)  432  and  434 . The remote radio head  430  may then be coupled (e.g., via fiber optic or other cables) to a base radio  440  at which typical modulation, demodulation and other radio functions are conducted. The transmit element  406  may also be coupled to the base radio  440 . 
     In an example embodiment, the remote radio head  430  may provide for switching among the receive antennas. In examples in which vertical beam steering of the array panels is conducted, four or more cables may be used to connect each of the left side panel element  402  and the right side panel element  404  to the remote radio head  430 . The remote radio head  430  may include one or more cavity filters corresponding to the number of antenna outputs provided to the remote radio head  430 . In cases in which vertical beam steering is conducted with a mechanical device adjusting the electrical tilt of the arrays, only one cable and cavity filter, bulk acoustic wave (BAW) filter, surface acoustic wave (SAW) filter, circulator or any other suitable filter may be employed for each array. In some cases, the remote radio head  430  could be eliminated and filters, low noise amplifier (LNA) and switching components may be integrated into antenna housings or in other housings proximate to the antennas. Switching components (whether part of or external to the remote radio head  430 ) would be used to select the best antenna for receipt or transmission of any given signal based on location of the target or source, the signal strength of the ATG base stations, and the level of interference from surrounding base stations or terrestrial stations. The antenna selection, then, has multiple triggers designed to maximize the signal to interference plus noise ratio. 
       FIG. 6  illustrates a panel antenna vertical pattern. When mounted on an aircraft such that the panel is focused generally perpendicular to the direction of travel, compensation for aircraft rolling maneuvers may be needed. As can be appreciated from  FIG. 6 , when the in-flight aircraft  330  (which is generally communicating with ATG base stations at and slightly below the horizon) is rolling toward a ground station, the upper portion of the antenna pattern rolls toward the ground station. Meanwhile, when rolling away from the ground station, the antenna pattern provides less gain toward the ground station. Thus, beam steering may be needed (or at least helpful) to focus the antenna gain on the ground station by tilting the antenna assembly to compensate for the aircraft roll. For the panel elements, mechanical or electrical steering may be employed. 
     Accordingly, in some embodiments, the antenna assembly  375  may further be in communication with a control element that may be configured to interface with various aircraft sensors to determine the amount of compensation to apply to compensate for aircraft maneuvering.  FIG. 7  illustrates a block diagram of components that may be employed for control of antenna assembly components (e.g., the side panels). As shown in  FIG. 7 , side panel element  400  may be operably coupled to a steering assembly  500 . The steering assembly  500  may be configured to mechanically or electrically tilt at least a portion of the antenna assembly  375  (e.g., the side panels (individually or collectively) of the side panel element  400 ) to maintain the side panels oriented to communicate with ATG base stations proximate to the horizon (e.g., within about 15 degrees below the horizon). A controller  505  may be provided in communication with the steering assembly  500  to provide control over the steering assembly  500 . The controller  505  may include processing circuitry  510  configured to provide control outputs for steering of the side panel element  400  based on, for example, knowledge of base station location and the relative position and orientation of the in-flight aircraft  330 . The processing circuitry  510  may be configured to perform data processing, control function execution and/or other processing and management services according to an example embodiment of the present invention. In some embodiments, the processing circuitry  510  may be embodied as a chip or chip set. In other words, the processing circuitry  510  may comprise one or more physical packages (e.g., chips) including materials, components and/or wires on a structural assembly (e.g., a baseboard). The structural assembly may provide physical strength, conservation of size, and/or limitation of electrical interaction for component circuitry included thereon. The processing circuitry  510  may therefore, in some cases, be configured to implement an embodiment of the present invention on a single chip or as a single “system on a chip.” As such, in some cases, a chip or chipset may constitute means for performing one or more operations for providing the functionalities described herein. 
     In an example embodiment, the processing circuitry  510  may include one or more instances of a processor  512  and memory  514  that may be in communication with or otherwise control a device interface  520  and, in some cases, a user interface  530 . As such, the processing circuitry  510  may be embodied as a circuit chip (e.g., an integrated circuit chip) configured (e.g., with hardware, software or a combination of hardware and software) to perform operations described herein. However, in some embodiments, the processing circuitry  510  may be embodied as a portion of an on-board computer. In some embodiments, the processing circuitry  510  may communicate with various components, entities and/or sensors of the in-flight aircraft  330 . Thus, for example, the processing circuitry  510  may communicate with a sensor network  518  of the in-flight aircraft  330  to receive altitude information, location information (e.g., GPS coordinates, latitude/longitude, etc.), pitch and roll information, and/or the like. 
     The device interface  520  may include one or more interface mechanisms for enabling communication with other devices (e.g., modules, entities, sensors and/or other components of the in-flight aircraft  330 ). In some cases, the device interface  520  may be any means such as a device or circuitry embodied in either hardware, or a combination of hardware and software that is configured to receive and/or transmit data from/to modules, entities, sensors and/or other components of the in-flight aircraft  330  that are in communication with the processing circuitry  510 . 
     The processor  512  may be embodied in a number of different ways. For example, the processor  512  may be embodied as various processing means such as one or more of a microprocessor or other processing element, a coprocessor, a controller or various other computing or processing devices including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), or the like. In an example embodiment, the processor  512  may be configured to execute instructions stored in the memory  514  or otherwise accessible to the processor  512 . As such, whether configured by hardware or by a combination of hardware and software, the processor  512  may represent an entity (e.g., physically embodied in circuitry—in the form of processing circuitry  510 ) capable of performing operations according to embodiments of the present invention while configured accordingly. Thus, for example, when the processor  512  is embodied as an ASIC, FPGA or the like, the processor  512  may be specifically configured hardware for conducting the operations described herein. Alternatively, as another example, when the processor  512  is embodied as an executor of software instructions, the instructions may specifically configure the processor  512  to perform the operations described herein. 
     In an example embodiment, the processor  512  (or the processing circuitry  510 ) may be embodied as, include or otherwise control the operation of the steering assembly  500  based on inputs received by the processing circuitry  510  indicative of ATG base station location and/or aircraft maneuvering or position information. As such, in some embodiments, the processor  512  (or the processing circuitry  510 ) may be said to cause each of the operations described in connection with the steering assembly  500  in relation to adjustments to be made to antenna arrays to undertake the corresponding functionalities relating to array compensation/stabilization based on execution of instructions or algorithms configuring the processor  512  (or processing circuitry  510 ) accordingly. In particular, the instructions may include instructions for processing 3D position information the in-flight aircraft  330  (including orientation) along with position information of fixed transmission sites in order to instruct an antenna array to tilt or otherwise orient in a direction that will facilitate establishing a communication link between the antenna array and one of the fixed transmission stations. 
     In an exemplary embodiment, the memory  514  may include one or more non-transitory memory devices such as, for example, volatile and/or non-volatile memory that may be either fixed or removable. The memory  514  may be configured to store information, data, applications, instructions or the like for enabling the processing circuitry  510  to carry out various functions in accordance with exemplary embodiments of the present invention. For example, the memory  514  could be configured to buffer input data for processing by the processor  512 . Additionally or alternatively, the memory  514  could be configured to store instructions for execution by the processor  512 . As yet another alternative, the memory  514  may include one or more databases that may store a variety of data sets responsive to input sensors and components. Among the contents of the memory  514 , applications and/or instructions may be stored for execution by the processor  512  in order to carry out the functionality associated with each respective application/instruction. In some cases, the applications may include instructions for providing inputs to control operation of the steering assembly  500  as described herein. In an example embodiment, the memory  514  may store fixed position information indicative of a fixed geographic location of ATG base stations. 
     The processing circuitry  510  may also be configured to receive dynamic position information indicative of a three dimensional position and orientation of the in-flight aircraft  330  to compute an adjustment to be applied (if needed) to the orientation of the side panel element  400  based on in-flight aircraft  330  dynamic position. The antenna assembly  375  may therefore be positioned optimally for engaging in continued communication with the corresponding ATG base station currently being used. The antenna assembly  375  can also be optimally positioned to anticipate handover to a next ATG base station based on a predicted future in-flight aircraft  330  location and the known locations of the ATG base stations. 
     A further embodiment of the aircraft antenna may be as a long blade mounted on the aircraft, with multiple antenna elements within the blade. The multiple elements are employed for beamforming that generally provides a horizon focused beam pattern. However, by using the long blade design, the horizon focused beam pattern can be achieved with a more narrow horizontal (azimuth) pattern (relative to that of the panel antenna) to focus gain toward the desired base station and reduce gain in other interfering directions. The blade results in a wider vertical antenna pattern (relative to the panel antenna), which obviates the need for beam steering in the vertical direction to account for pitch or roll. The more narrow horizontal pattern in combination with the wider vertical pattern delivers a smaller interference profile than the panel antenna, because less interference “surface area” is captured by the antenna pattern. However, the general horizon focus is maintained, and interference from the ground communication layer  320  below the aircraft is substantially avoided. 
     The network  100  and its corresponding ATG base stations employing the wedge shaped cell architecture described above in reference to  FIGS. 1 and 2  may be employed to provide coverage for communication with receivers on aircraft over a very large geographical area, or even an entire country. Moreover, using such architecture may substantially reduce or even minimize the number of ATG base stations that are needed to construct the network  100  since relatively large distances may be provided between ATG base stations. Beamforming techniques (which may also be referred to as beam steering techniques) and frequency reuse may be employed to further improve the ability of the network  100  to provide quality service to multiple targets without interference. Moreover, by providing a movable or steerable antenna array (e.g., antenna array  375 ) on the in-flight aircraft  330 , particularly for an array that is shielded relative to transmissions directly (or nearly directly) below the in-flight aircraft  330  or is otherwise configurable to have less gain anywhere other than near the horizon, both the ATG base stations and the antenna array  375  may be configured to avoid interference below the in-flight aircraft  330 . This may permit spectrum reuse of, for example, ISM band frequencies (e.g., 2.4 GHz and/or 5.8 GHz) that may be unlicensed, or even licensed band frequencies at any desirable frequency range. 
     If airborne interference from ground transmitters such as, for example, ground based WiFi transmitters were relatively low over the entirety of the geographic area to be covered, it could be expected that the wedge architecture of the network  100  of  FIGS. 1-2  could provide robust and cost effective coverage without any further modification even though ground transmitters (e.g., terrestrial base stations  300 ) may use omni-directional antennas that are at least partially oriented to transmit upward using the same frequency. 
     As mentioned above, the ATG base stations ( 350  and  355 ) may employ beamforming (e.g., via a beamforming control module that may employ both 2D knowledge of fixed base station location and 3D knowledge of position information regarding the in-flight aircraft  330  to assist in application of beamforming techniques). Likewise, beamforming and/or beamsteering may be employed on the antenna array  375  of the in-flight aircraft  330  to use knowledge of ATG base station location and aircraft maneuvering (e.g., turns or pitch and roll) to maintain the antenna array  375  in an advantageous orientation to communicate with the ATG base stations when the in-flight aircraft  330  maneuvers. The antenna array  375  may therefore be adjusted in a compensatory manner responsive to maneuvering of the in-flight aircraft  330 . The compensation employed may involve switching between antenna elements that are best positioned for the orientation of the aircraft relative to the location of a serving ATG base station and/or tilting of the antenna array  375  to maintain the array in an advantageous position relative to the focus region of the array. 
     Although not every element of every possible embodiment of the ATG network  100  is shown and described herein, it should be appreciated that the communication equipment on the aircraft  330  may be coupled to one or more of any of a number of different networks through the ATG network  100 . In this regard, the network(s) can be capable of supporting communication in accordance with any one or more of a number of first-generation (1G), second-generation (2G), third-generation (3G), fourth-generation (4G) and/or future mobile communication protocols or the like. In some cases, the communication supported may employ communication links defined using unlicensed band frequencies such as 2.4 GHz or 5.8 GHz. Example embodiments may employ time division duplex (TDD), frequency division duplex (FDD), or any other suitable mechanisms for enabling two way communication within the system. 
     As indicated above, a beamforming control module may be employed on wireless communication equipment at either or both of the network side or the aircraft side in example embodiments. Moreover, in some embodiments, the communications received at the aircraft side may be distributed to equipment on the aircraft (e.g., such as telephone handsets or UEs via a WiFi router or other wireless access point, or aircraft communication equipment). In some embodiments, information distributed from the wireless access point may be provided to passenger devices or other aircraft communications equipment with or without intermediate storage. 
     In an example embodiment, the processing circuitry  510  may be configured to conduct switching to select an antenna element among the antenna assembly for communication with an optimal or otherwise selected one of the ATG base stations. This switching may be performed to select a particular antenna element (or sector) in a panel element or to select between panel elements and/or other antenna elements (e.g., the blade antenna) based on the location of the selected one of the ATG base stations relative to the in-flight aircraft  330 . As mentioned above, the switching may be performed using switch devices within the remote radio head  430  or at another location. In some embodiments, the particular antenna element that is selected may additionally or alternatively be tilted electrically or otherwise positionally adjusted to compensate or stabilize the particular antenna element responsive to maneuvering of the in-flight aircraft. Thus, for example, the processing circuitry  510  may initially receive information indicative of dynamic position information of the in-flight aircraft  330 , which may include a 3D position and/or orientation information (e.g., pitch and roll) and/or an estimated future position. The processing circuitry  510  may determine an expected relative position of a first network node (e.g., one of the ATG base stations) relative to the aircraft (e.g., based on the fixed position information indicating ATG base station location and the dynamic position information). Tracking algorithms may be employed to track dynamic position changes and/or calculate future positions (relative or geographic) based on current location and rate and direction of movement. After an expected relative position is determined, the processing circuitry  510  may be configured to provide instructions to select an antenna element to communicate with the first network node in the focus region based on the expected relative position. Thereafter, any changes in dynamic position information, particularly related to pitch and roll, may be compensated for by steering of the antenna element (e.g., mechanically or electrically). 
       FIG. 8  illustrates a block diagram of one method that may be associated with an example embodiment as described above. From a technical perspective, the processing circuitry  510  described above may be used to support some or all of the operations described in  FIG. 8 . As such, the platform described in  FIG. 7  may be used to facilitate the implementation of several computer program and/or network communication based interactions. As an example,  FIG. 8  is a flowchart of a method and program product according to an example embodiment of the invention. It will be understood that each block of the flowchart, and combinations of blocks in the flowchart, may be implemented by various means, such as hardware, firmware, processor, circuitry and/or other device associated with execution of software including one or more computer program instructions. For example, one or more of the procedures described above may be embodied by computer program instructions. In this regard, the computer program instructions which embody the procedures described above may be stored by a memory device of a device (e.g., the controller  505 , and/or the like) and executed by a processor in the device. As will be appreciated, any such computer program instructions may be loaded onto a computer or other programmable apparatus (e.g., hardware) to produce a machine, such that the instructions which execute on the computer or other programmable apparatus create means for implementing the functions specified in the flowchart block(s). These computer program instructions may also be stored in a computer-readable memory that may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture which implements the functions specified in the flowchart block(s). The computer program instructions may also be loaded onto a computer or other programmable apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus implement the functions specified in the flowchart block(s). 
     Accordingly, blocks of the flowchart support combinations of means for performing the specified functions and combinations of operations for performing the specified functions. It will also be understood that one or more blocks of the flowchart, and combinations of blocks in the flowchart, can be implemented by special purpose hardware-based computer systems which perform the specified functions, or combinations of special purpose hardware and computer instructions. 
     In this regard, a method according to one embodiment of the invention, as shown in  FIG. 8 , may include determining an expected relative position of an ATG base station relative to an in-flight aircraft at operation  800 . The expected relative position may be determined based on information indicative of aircraft location and information indicative of the known fixed positions of ATG base stations. However, in some cases, the ATG base station location may be discovered based on detection of a pilot signal or other transmissions from the ATG base station. The method may further include selecting an antenna element to employ for communication with the ATG base station based on the expected relative position at operation  810 . The selected antenna element may be an element of an antenna assembly on the aircraft. The antenna assembly may include transmission and receive components, and may include blade antennas, panel antennas and/or the like. Thus, a selected antenna element could be a particular panel antenna or blade antenna, or could be a particular sector of a panel antenna. The selected antenna element could be chosen based on signal strength measured or estimated, or other factors for base stations within a focus region (e.g., horizon to about 15 degrees below the horizon) relative to the aircraft. At operation  820 , an indication of a change to the dynamic position information may be received, and the change may be indicative of at least a change in the pitch or roll of the aircraft. The selected antenna element may then be adjusted (e.g., by mechanical or electrical tilting) to compensate for the change to the dynamic position information at operation  830  (e.g., to keep the selected antenna element substantially oriented toward the focus region based on the change to the dynamic position information). 
     In an example embodiment, the layered approach described above could be augmented to include an additional layer above the ATG communication layer. The layer above the ATG communication layer may be a high altitude service layer. The high altitude service layer may be populated with high altitude service craft such as drones or other devices capable of flying (or orbiting) at high altitude. The high altitude service craft may be in communication with ground stations receiving communication signal from ATG base stations (or satellites) and relaying such communications on to the in-flight aircraft. However, the high altitude service craft with which the in-flight aircraft communicate may be located proximate to the horizon. The communication with high altitude service craft proximate to the horizon allows the same vertical beam steering antennas described above to be employed except the vertical beam steering antennas are steered to maintain the focus area just above the horizon to locate distant high altitude service craft instead of being steered to maintain the focus area just below the horizon. The additional altitude may extend the spacing between service stations (e.g., drones and/or ATG stations) that can be provided to give continuous coverage. Coverage can therefore be provided over sparsely populated areas and/or oceans. 
     As shown in  FIG. 9 , the network of  FIG. 3  may be provided with one or more high altitude service craft  900  in a high altitude service layer  910 . The high altitude service layer  910  may extend above the ATG communication layer  335  (e.g., above the predetermined maximum altitude  340 ) to high altitudes including low earth orbit and beyond. In some examples, drones or balloons acting as high altitude service craft  900  may loiter or otherwise operate as high as (or higher than) 50,000 ft to 75,000 ft. However, it should be noted that the specific example altitudes described herein may change over time as aircraft capabilities change. The high altitude service craft  900  may communicate with the ATG base stations ( 350  and  355 ) via an ATG link  920 , with the in-flight aircraft  330  via an aircraft link  930  and/or with a satellite via a satellite link  940 . Accordingly, the high altitude service craft  900  may be enabled to service the in-flight aircraft  330  over vast distances and in different communication environments. 
     Accordingly, uninterrupted handover of receivers on the in-flight aircraft  330  may be provided while passing between coverage areas of ATG base stations and high altitude service craft having overlapping coverage areas as described herein. When employed in a network that includes a high altitude service layer  910 , the antenna assembly  375  may be configured to focus energy in an area from the horizon to about 10 or 15 degrees above the horizon (from the perspective of the in-flight aircraft  330 ) to communicate with the high altitude service craft  900 . Moreover, the antenna assembly  375  can be vertically steered to shift between being serviced by ATG base stations or high altitude service craft based on signal strength or other such factors in association with a handover managed between the ATG base stations and high altitude service craft (or vice versa). The high altitude service craft  900  may also include antennas focused toward the horizon (e.g., focusing energy in an area from the horizon to about 10 or 15 degrees below the horizon (from the perspective of the high altitude service craft  900 ) and the service craft antenna assembly may also be vertically steerable to account for turning or banking of the high altitude service craft  900  in similar fashion to the way the antenna assembly  375  of the in-flight aircraft  330  is steerable (as described above). Thus, the high altitude service craft  900  may also use horizon-focused antenna assemblies for communication with aircraft, other drones and/or with the ground. Moreover, the same frequencies can be used for each of these links, and it may also be the same frequency used in the ground communication layer  320  given that the beams for such communication are steerable (e.g., employing spatial filtering and vertical beamsteering) to extend substantially parallel to the surface of the earth and avoid interference with communications in the ground communication layer  320 . In some cases, however, the high altitude service craft  900  may use a first frequency to communicate to aircraft and ground stations, and the aircraft (where it does not use high altitude service craft  900  for connectivity) may use a second frequency to communicate from the aircraft to ground and ground to ground. 
     The employment of the high altitude service layer  910  may effectively create a sandwich mesh architecture. High altitude service craft  900  may link to other high altitude service craft to provide a GB/s wireless backhaul network that may only selectively touch or access ground stations or satellites in a handful of places. The high altitude service craft  900  may therefore generally be above the weather and connections to the ground may be selectively made in areas that have good weather to minimize negative impacts of weather on communications at higher frequencies, whether RF or optical. Furthermore, at high altitudes, physics may enable ready use of free space optics or high frequency RF to further enhance network performance. Meanwhile, the antenna assembly  375  of the in-flight aircraft  330  is steerable +/−10 to 15 degrees from the horizon to selectively communicate with the ATG base stations ( 350  and  355 ), with other in-flight aircraft  330  and/or with the high altitude service craft  900 . 
     As an alternative to the architecture of  FIG. 5 , in which separate receive and transmit elements are provided, some embodiments may employ a single steerable antenna element (or panel) that handles both transmit and receive functions by employing duplexing. By employing an antenna element that can handle both transmit and receive functions, the size, weight, number and cost of antenna elements employed may be reduced. Maximal ratio combining may also be employed. With employment of full duplexing, receiver filtering becomes important to allow signals to be differentiated. BAW filters, in-line cavity filters or a BAW duplexer may therefore be employed. A BAW duplexer may be a relatively straightforward option for such a full duplex solution. 
       FIG. 10  illustrates a full duplex radio architecture in accordance with a first option. In this regard,  FIG. 10  shows an architecture for a relatively long blade antenna  1000  that may be provided in some embodiments. The antenna  1000  may include one or more elements  1010  (e.g.,  10  in some cases) that may provide signals to a Butler combiner  1020 , which may be operably coupled to a multi-pole throw switch  1030  (e.g., a ten pole switch). The switch  1030  may be operably coupled to a circulator  1040 . The circulator  1040  may isolate signals among ports so that signals on port  1  go to port  2 , signals on port  2  go to port  3 , etc. The circulator  1040  may provide as much as 18 dB of isolation port-to-port with a relatively low insertion loss of 0.6 dB. The circulator  1040  may be operably coupled to a receive filter  1050  and ultimately to receiver circuitry  1060  via a low noise amplifier (LNA)  1054  and a switch  1058 . In this architecture, the receive filter  1050  is in front of the LNA  1054  for enhanced receiver overload protection (e.g., for a transmit signal level at the LNA input of −34 dBm, overall noise figure may be 7.9 dB). The circulator  1040  is also operably coupled to transmitter circuitry  1070  through a switch  1072 , a cavity filter  1080  and a power amplifier  1090 . 
       FIG. 11  illustrates a full duplex radio architecture in accordance with a second option. In this regard,  FIG. 11  shows an architecture for a relatively long blade antenna  1100  that may be provided in some embodiments. The antenna  1100  may include one or more elements  1110  (e.g.,  10  in some cases) that may provide signals to a Butler combiner  1120 , which may be operably coupled to a multi-pole throw switch  1130  (e.g., a ten pole switch). The switch  1130  may be operably coupled to a circulator  1140 . The circulator  1140  may isolate signals among ports so that signals on port  1  go to port  2 , signals on port  2  go to port  3 , etc. The circulator  1140  may provide as much as 18 dB of isolation port-to-port with a relatively low insertion loss of 0.6 dB, as described above. However, in this example, an LNA  1154  is provided prior to a receive filter  1150 . The receive filter  1150  is then operably coupled to the receiver circuitry  1160  via switch  1158 . In this architecture, the receive filter  1150  is behind the LNA  1154  for reduced noise figure, but higher transmit signal level at the LNA  1154  (e.g., for a transmit signal level at the LNA input of +6 dBm, overall noise figure may be 6.1 dB). The circulator  1140  is also operably coupled to transmitter circuitry  1170  through a switch  1172 , a cavity filter  1180  and a power amplifier  1190 . In some alternative embodiments, either the architecture of  FIG. 10  or the architecture of  FIG. 11  could be duplicated with two duplexer elements replacing the circulators of each respective figure for an alternative approach. 
     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe exemplary embodiments in the context of certain exemplary combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. In cases where advantages, benefits or solutions to problems are described herein, it should be appreciated that such advantages, benefits and/or solutions may be applicable to some example embodiments, but not necessarily all example embodiments. Thus, any advantages, benefits or solutions described herein should not be thought of as being critical, required or essential to all embodiments or to that which is claimed herein. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.