Abstract:
Systems and methods are enclosed for processing antenna position information. The systems and methods involve positioning at least one sensor in proximity to an antenna for measuring alignment of the antenna; at a ground station in proximity to a tower holding the antenna, periodically receiving antenna alignment information from the at least one sensor; and transmitting the alignment information to a control station for determination whether the alignment of the antenna complies with antenna specifications.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims benefit under 35 USC 119(e) to U.S. Provisional Application No. 61/140,723, filed Dec. 24, 2008, the disclosure of which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of wireless communications, and more particularly, to the application of telemetry to improve the robustness of wireless communications infrastructures. 
     BACKGROUND OF THE INVENTION 
     An essential part of a wireless service provider&#39;s business is its ability to provide adequate communication capabilities to its customers. In order to provide such capabilities, wireless service providers deploy communication antennas on towers, rooftops, buildings, and other tall structures. The height of such structures allows the radio signal from each communication antenna to travel several miles, establishing a geographic area within which service may be provided to customers. Wireless service providers typically install several directional communication antennas per site as multiple directional communication antennas are needed for increased capacity and reception. 
     In order to provide the required radio signal throughout a defined area, each directional antenna is intended to face a specific direction (referred to as “azimuth”) relative to true north, to be inclined at a specific downward angle with respect to the horizontal in the plane of the azimuth (referred to as “downtilt”) and to be vertically aligned with respect to the horizontal (referred to as “skew”). Undesired changes in azimuth, downtilt, and skew will detrimentally affect the coverage of a directional antenna. These alignments may be likened to the axes commonly used to describe the attitude of an aircraft: Azimuth corresponds to the yaw of an aircraft about a vertical axis; skew corresponds to the roll of an aircraft about its longitudinal axis; and downtilt corresponds to the pitch of the nose of an aircraft above or below a horizontal plane (or about a lateral axis extending horizontally through the aircraft at right angles to the longitudinal axis). In general, the more accurate the installation, the better the network performance that may be achieved within the area served by the antenna. Directional antenna installations are performed by tower companies who use certified tower climbers to carryout such installations. 
     An antenna&#39;s azimuth, downtilt and/or skew can change over time, due to the presence of high winds, corrosion, poor initial installation, vibration, hurricanes, tornadoes, earthquakes, or other factors. It is common for wireless service providers to conduct periodic audits of their communication antennas to ensure that each antenna has not deviated significantly from its desired azimuth, downtilt and/or skew. Wireless service providers frequently hire third party tower companies to perform audits and to make any necessary adjustments to maintain the desired azimuth, downtilt and skew. Such audits, however, may be labor intensive and dangerous, frequently requiring certified tower climbers to physically inspect each antenna, and to take appropriate measurements to determine any deviance from the desired positioning. This task can become even more time consuming if many towers are affected as a result of a hurricane or storm, in which case it could take between two to four months to figure out which towers have been affected, as the antennas have to be checked one by one. 
     Given the present state of the art, there is a need in the art for means for remote and continuous monitoring to determine whether and to what extent the desired physical positioning of an antenna has been altered. 
     SUMMARY OF THE INVENTION 
     The present invention includes an autonomous wireless antenna sensor system that provides wireless service providers with an alternative to periodic audits or spot checks following events that may have changed an antenna&#39;s positioning. The autonomous wireless antenna sensor system of this invention measures physical changes in the azimuth, downtilt, or skew of a communication antenna. The system of the present invention may initiate an alert to a wireless service provider, for example, when it detects is a change in the azimuth, downtilt or skew of a communication antenna sufficient to require realignment of the antenna, or when it detects a tilt that is unacceptable. 
     The autonomous wireless antenna system of the present invention may include three subsystems: a wireless antenna sensor, a remote sensor control station, and a remote graphical user interface (“GUI”). The system may also include a repeater or relay device, used to retransmit sensor signals to the remote sensor control station. In one embodiment of the present invention, a wireless antenna sensor measures changes in antenna azimuth downtilt and skew by using a gyroscope microchip and an accelerometer microchip, or a combination of both. Information regarding changes in antenna alignment can be relayed from the wireless antenna sensor attached to the communication antenna to the remote sensor control station located near the wireless service provider&#39;s base station at the foot of an antenna tower, using any low power wireless communication medium, such as Zigbee IEEE 802.15.4, Bluetooth, or WiFi. If desired, a wired connection, such as one following AISG Standards, may also be used for this purpose. 
     It is an object of this invention to provide a method for remotely monitoring changes in the positioning of antennas mounted on towers or other difficult-to-access locations so that appropriate and timely corrections may be applied. 
     It is another object of the invention to provide a user interface that is remote from a number of antenna sites, whereby changes in the positions of one or more antennas may be detected, and appropriate remedial treatment may be applied. 
     It is a further object of the invention to provide electrical power to microchips on antennas without a requirement for running an electrical wire from a ground-based power grid to the antennas. 
     It is yet another object of the invention to provide a method for remotely measuring the degree of misalignment of an antenna so that appropriate corrective measures may be taken without the need to conduct full re-alignment procedures. 
     These and other objects of the invention will become apparent in the following descriptions of the drawings and of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic drawing illustrating an antenna tower and antennas used in an autonomous wireless antenna sensor system in accordance with at least one embodiment of the present invention; 
         FIG. 2  is a schematic drawing illustrating the mounting of wireless antenna sensors to antennas in accordance with one embodiment of the present invention; 
         FIG. 3  is a schematic drawing illustrating the components and communications media for an autonomous wireless antenna sensor system in accordance with one embodiment of the present invention; and 
         FIG. 4  is a schematic drawing illustrating a first method for obtaining antenna alignment information in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention together with the aforesaid objects and advantages is best understood from the following detailed description of the preferred embodiments of the invention. The autonomous wireless antenna system of the present invention may include three subsystems: a wireless antenna sensor, a remote sensor control station, and a remote graphical user interface (“GUI”). The system may also include a repeater or relay device, used to retransmit sensor signals to the remote sensor control station. In one embodiment of the present invention, a wireless antenna sensor measures changes in antenna azimuth downtilt and skew by using a gyroscope microchip and an accelerometer microchip, or a combination of both. In one embodiment of the present invention, a gyroscope microchip may be used to measure variations in azimuth, and an accelerometer microchip may be used to measure changes in downtilt and skew. In embodiments where such microchips feature high precision and sensitivity, signals from both sensors may be used as inputs to a processor whose output combines and processes the sensor information to provide a more accurate means for determining and measuring changes of an antenna&#39;s azimuth, downtilt, and skew. Variations in antenna alignment that can be false alarms may be reduced or eliminated though signal processing, for example, by cross referencing instantaneous accelerometer information against longer term gyroscopic information. 
     The remote sensor control station of the present station may relay antenna alignment data via a wired or wireless communications link. In this manner, the remote sensor control station can provide antenna alignment information to a remotely-located user viewing a graphical user interface. In one embodiment, software for monitoring and recording alignment information and changes provide a baseline for determining when sufficient misalignment has occurred to require a wireless service provider to take corrective action (e.g., by contracting an antenna maintenance company to properly align antenna). 
     In one embodiment of the present invention, the wireless antenna sensor and its wireless communications system may function with low power requirements which can be satisfied in any of a number of ways. For example, Radio Frequency (“RF”) energy may be harvested from the RF signal emitted by the antenna site itself to provide power to run the wireless antenna sensor and its wireless communication system. Alternatively, solar power, wind power, or piezo electric power (e.g., generated from mechanical stress as the tower is moved by the wind), coupled with a battery or storage capacitor, may produce power sufficient to run the system. If desired, electrical power from a base station may be provided through a new or existing electrical wire on the tower. The wired option, which may follow AISG Standards, may require additional electrical wire to be run up the tower. 
     As wireless antenna sensors used on the antennas may have unique electronic serial numbers, the system of this invention is not limited to only indicating when an antenna becomes misaligned, but may also specifically identify the antenna from which the measurements are taken. Wireless service providers can use the antenna identification information to accurately manage antenna assets. Thus, one of the advantages of the present invention is that maintenance or replacement can more easily and accurately be achieved than is currently possible through the haphazard antenna maintenance procedures currently used by most third party tower maintenance companies. 
     Once the components of the system of the present invention are installed, a wireless service provider would no longer need to hire third party tower companies to verify antenna azimuth, downtilt or skew through visual observation or manual field measurements. Use of the present invention allows sensing of antenna positioning as changes in the positioning occur, such as for example, a change in the attitude of the sensors attached to the antenna. The antenna position changes may be relayed to a remote sensor control station, and also the wireless service provider may be notified of any undesired changes via a Remote GUI, for example. 
       FIG. 1  illustrates two embodiments of the wireless antenna system of the invention. The wireless antenna system may be retrofitted on a tower  10  supporting multiple antennas  30 ,  31  receiving and radiating electromagnetic energy in the RF range  40 . The antennas  30 ,  31  may also radiate in other frequency bands. 
       FIG. 1  shows at the base of the tower  10  a base transceiver station  80  which may also house and electrically support a remote receiver control unit  20 . Cables  50  may conduct communication signals to and from antennas  30 ,  31 , and may be part of the original antenna installation. 
       FIG. 2  illustrates another aspect of the invention where antennas  30 ,  31  are attached to the antenna tower  10 , and include microchip sensors  60 ,  61 , and  70 ,  71  secured directly to the antennas. For each antenna, one microchip ( 70 ,  71 ) may serve as an accelerometer to measure antenna movement in two directions, as along X and Y axes, such as tilt and skew, and a second microchip ( 60 ,  61 ) may serve as a gyroscope to measure angular movement, such as variations in azimuth. In an alternative embodiment, a combination of signals from microchips attached to the antennas, when processed by a CPU, may also provide precise information regarding changes in antenna positioning without triggering false alarms. 
       FIG. 3  is a schematic depiction of the operation of the system in accordance with one embodiment of the present invention in which two antennas  30 ,  31  are being monitored for movement away from a desired orientation. As is shown in  FIG. 3 , movement sensors  60 ,  61 ,  70 ,  71  generate signals that are fed to and transmitted by smaller antennas  150 ,  151  to receiving antenna  110  at ground station  20 . In an alternative embodiment, the signals transmitted by antennas  150  and  151  are received by a repeater  21  ( FIG. 1 ) which in turn may retransmit these signals at the same or a different frequency to the antenna  110 . The repeater may be positioned anywhere within the coverage of the antennas  150  and  151 . 
     A sensor (e.g.,  60 ,  61 ,  70 , or  71 ) may powered by one or more RF energy harvesting  90  and storage devices  100  located on the tower  10  in the vicinity of the antennas. In one embodiment, the wireless antenna sensors may be located within a housing to prevent moisture buildup. The sensors may be attached to the antenna using any conventional attachment method. Alternatively, industrial strength adhesive tape may be used for attaching the wireless antenna sensors to their respective communication antennas  30 ,  31 . 
     The sensors and/or the wireless antennas may have a unique electronic serial numbers which may serve to identify a specific antenna or sensor. The wireless antenna sensors may transmit the measured antenna alignment information (e.g., change in azimuth, tilt or skew) to remote sensor control station  20  or the relay station  21  together with antenna or sensor identification information. In one embodiment, the wireless antenna sensor, through its corresponding antenna (e.g.,  150  or  151 ), communicates over the air with remote sensor control station  20  via Zigbee IEEE 802.15.4 Wireless Standard or its equivalent. 
     The remote sensor control station  20  may be installed in or around the wireless service provider&#39;s base transceiver station  80  that is conventionally located on or near the ground level. In one embodiment of the present invention, at least one remote sensor control station  20  may be present at each site. A remote sensor control station may have a unique address, such as a MAC or IP address. 
     The remote sensor control station  20  may periodically request or receive measurement results from the wireless antenna sensors  60 ,  61 ,  70 ,  71 . The intervals for which the measurements are taken may be user defined. Measurement records may be date and time stamped. The remote sensor control station may assign a user defined name to each wireless antenna sensor and data from the sensors may be processed and placed on a lookup table. An antenna name may reference a particular antenna being measured by each wireless antenna sensor. The remote sensor control station may be programmed to report only defined wireless antenna sensors in order to ensure that only the desired antenna(s) are being monitored. Measurement reports may be stored in the remote sensor control station&#39;s memory or on a hard storage device  120 . Once measurements are stored, they may be retrieved from the remote sensor control station either locally using a PC and a data cable (USB or other suitable connector) or remotely, such as via a Telco (i.e., T1) or mobile communication device/data card (such as, for example, GSM/CDMA/IDEN/SATELITE). 
     Information stored, and management functions of the autonomous wireless antenna sensor system, may be remotely controlled via a local area network (“LAN”) or Internet connection  130  by a remote user GUI  140 . The remote user GUI may be web based and may require a user name and password in order to access it. The remote user GUI can be hosted on either the Internet or the user&#39;s intranet. The remote user GUI&#39;s functions include retrieving the data from online remote sensor control stations and storing the data on a database which may be an online database. Once the data is imported, the user can upload the desired/target measurements for azimuth, tilt and skew which determine the specifications to which the antennas should adhere. The most recent measurement results may be displayed by date, time, site name, and antenna name. The user may request that the difference in measurement from a desired/target position for each antenna be provided in a report generated by the system. The user may also define the maximum difference measurement that will be allowed and request that the remote user GUI produce an alarm log that will display all out-of-specification antennas. The user may also require that the remote user GUI notify him or her, via e-mail or other communication means, of any out-of-specification antennas, at which time the user may reposition the specific antenna. By correcting the orientation of out-of-specification antennas as adverse conditions develop, needless testing and periodic third party audits may be avoided. 
       FIG. 4  illustrates a first method for obtaining antenna alignment information in accordance with one embodiment of the present invention. In this embodiment, the remote system  80  is active and remains in low power mode when no event occurs. An event may be defined as a change in antenna positioning that deviates from acceptable antenna specification. In step  401  the remote system  80  is powered and an application running in an end-user&#39;s computer, for example, is started. This application may be used in conjunction with the GUI  140  to interface with and control certain functions of the remote site  80 . In step  403  the end-user computer, which may also be referred herein as the remote system base, gathers data indicative of the status of the remote system  80  and optionally sends calibration commands to the remote station  80 . 
     In step  405  the remote station  80  determines whether an event has occurred. If no event is detected, the remote system  80  enters in a wait mode. After a time out period (which may be changed by the system operator) elapses, the remote system  80  captures data ( 409 ) provided by antenna sensors, which may include temperature, sensor battery level, and the antenna alignment information (e.g., yaw, pitch, or roll). In step  411  the captured data may be sent to the remote base system together with control data from the remote site  80 . 
     Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.