Patent Description:
Cellular reception in or on moving vehicles such as cars, buses, trams, train and ships is often poor because the vehicles are moving through areas which are served by different transmission installations and because the vehicles are predominantly metallic structures which act as Faraday cages and therefore further attenuate cellular signals.

Moving vessels at sea encounter weak reception of mobile communication signals because, in addition to the above, base station antennas are primarily planned, positioned and installed on land in order to serve mainland hotspots. The sea routes along which vessels travel are not usually located in main radiation areas of base station antennas and are generally a long distance away from cellular towers, resulting in significant pathloss.

In order to address weak or poor reception, cellular repeater systems are often used. A cellular repeater (also known as cell phone signal booster or amplifier), is a system used for boosting the cell phone reception in confined or remote areas such as buildings, tunnels, ships and the like. Cellular repeater systems generally comprise three main functional units: a donor external antenna, a signal bi-directional amplifier, and an internal rebroadcast antenna or distributed antenna system.

Due to the translational movement of a vessel along a sea route, the cellular tower providing the best signal for use by the vessel will change; indeed, the direction from which the best serving donor signal is received may be at any azimuth direction - i.e. anywhere <NUM>° around the vessel's horizon. Omnidirectional antennas radiate power uniformly in all directions in one plane, and are therefore selected for in-ship cellular repeater applications. However, omnidirectional donor antennas have extremely low gain (usually 0dBi compared to the significantly higher gain offered by a typical directional antenna) as a result of the received power based on very low radio link budget between the donor cellular tower and the cellular repeater system (the radio link budget accounts for all of the gains and losses between the transmitter and the receiver). This affects the effectiveness and efficiency of such cellular repeater systems.

<CIT> discloses a repeater installed in a moving object in which a link antenna module has a plurality of fixed antennas which are configured to detect a propagation environment. A controller selects a link antenna that receives the best signal from a serving base transceiver station.

It is an aim of the present invention to mitigate at least some of the above mentioned drawbacks of the prior art.

According to a first aspect of the invention, there is provided a repeater antenna system according to claim <NUM>.

Preferably the controller is configured to control operation of the second azimuth alignment device by instructing the azimuth alignment device to steer the donor antenna to the at least first azimuth heading value or second azimuth heading value.

Preferably the controller is configured to control operation of the first azimuth alignment device to move the scanning antenna from the at least first azimuth heading value to the second azimuth heading value after a predetermined time period.

Preferably the controller is configured to control operation of the first azimuth alignment device according to a sequencing operation, wherein the sequencing operation comprises operating the scanning antenna at the at least first azimuth heading value for a predetermined time period, moving the scanning antenna to the at least second azimuth heading value upon expiry of the predetermined time period and operating the scanning antenna system at the second azimuth heading value for a predetermined time period.

Preferably the sequencing operation comprises operating the scanning antenna at a predefined number of azimuth heading values.

Preferably the controller is configured to control operation of the second azimuth alignment device to move the donor antenna to one of the predefined number of azimuth heading values that provides optimal network and signal parameters according to predefined criteria upon expiry of a complete sequencing operation.

Preferably the first and second antenna alignment devices each comprise a motor and an antenna mounting bracket, wherein the motor is configured to move the antenna mounting bracket and lock the antenna mounting bracket in position.

Preferably the donor and scanning antenna each comprise a GPS module, and wherein the first and second antenna alignment device each comprise an optical encoder and/or electrical potentiometer.

Preferably the at least first azimuth heading value and the second azimuth heading value are predefined with respect to a direction of travel.

Preferably, the collected data comprises base station cell identification and received signal strength, and the predefined criteria preferably comprises signal strength, quality and available capacity.

According to a second aspect of the invention, there is provided a method for operating a mobile vehicle antenna system according to claim <NUM>.

According to a third aspect of the invention, there is provided a machine readable medium storing executable instructions that, when executed by a data processing system, cause the system to perform a method of the second aspect.

A preferred embodiment of the invention will be described with reference to the appended drawings in which:.

<FIG> illustrates a prior art antenna system in a vessel. An outdoor omnidirectional antenna <NUM> is connected to a four-port repeater <NUM>. The four-port repeater <NUM> is powered via power supply <NUM> and is connected to one or more line amplifiers <NUM> which in turn are connected to one or more panel internal antennas <NUM>. The omnidirectional antenna <NUM> acts as a donor antenna which receive donor signal coverage from base station and tower signals from land. The signals are passed to the repeater <NUM> which amplifies the signals before they are split between line amplifiers <NUM>. The line amplifiers <NUM> further amplifier the signals before they are split and passed to panel antenna <NUM> which are located internally in the vessel.

The torus-shaped radiation pattern <NUM> of an omnidirectional antenna <NUM>, is shown in <FIG> (side view) and <FIG> (top view). Radial distance from the centre indicates the power radiated (which reaches a maximum in the horizontal, or azimuth plane and drops to zero directly above and below the antenna. Antenna <NUM> radiates power equally in all directions in the azimuth plane.

<FIG> shows an omnidirectional antenna <NUM>, a bi-directional amplifier <NUM> and three rebroadcast panel antennas <NUM>. The signals collected by omnidirectional antenna <NUM> are directed to the bi-directional amplifier for amplification and distribution to the rebroadcast antennas. Since the donor external is omnidirectional antenna, signals emanating from all azimuth directions (including background noise) will be collected passed to the bi-directional amplifier <NUM> and amplified equally. Existing bi-directional amplifiers are high-power and offer maximum gains of around 100dB. However, signals from particular cellular towers cannot be filtered from the background noise, and as such a bi-directional amplifier of high gain will still fail to compensate for the low gain of the omnidirectional antenna.

The present invention utilises one or more directional antennas. An example of a radiation pattern <NUM> created by three equally spaced directional antennas is shown in <FIG> (side view) and <FIG> (top view). Although separate directional antennas used together are discussed, it will be appreciated that a single antenna have multiple directional beams or lobes can also be used. The radiation pattern <NUM> comprises three separate patterns, each occupying an azimuth range centred on the azimuth heading value of the directional beams of each of the three directional antennas. Although the radiation pattern of each antenna is identical in <FIG>, the patterns could be different. The radiation pattern for each separate antenna beam of the <NUM> -beam directional external antenna systems should have at least 3dBi gain.

<FIG> shows, schematically, the components of an antenna system <NUM> of the present invention. System <NUM> comprises a scanning antenna system <NUM> comprising three directional scanning antennas or a multidirectional antenna having three beams) which is connected to an RF network scanning analyser <NUM>. Both the RF network scanning analyser <NUM> and the scanning antenna system <NUM> are in communication with a controller <NUM>. Controller <NUM> is also in communication with donor antenna system <NUM> which comprises three directional donor antennas (or a multidirectional antenna having three beams). The donor antenna system <NUM> is in communication with a bi-directional amplifier <NUM> which in turn is connected to three internal antennas <NUM>.

Each of the scanning antennas in scanning antenna system <NUM> is positioned such that the azimuth heading (i.e. the direction of the main beam) is equally spaced from the azimuth heading of the other two antennas. Thus, for three scanning antennas or beams, the azimuth headings will be separated by <NUM> degrees. The scanning antennas are configured to receive data indicative of mobile communication signal and network parameters, which may comprise, for example, signal strength, available networks, coverage and capacity indicators, bandwidth, etc. The signals and networks data received are those from cellular tower transmitters and base station on the coastline or in nearby land.

The direction of the main beam of each of the donor antennas/lobes in donor antenna system <NUM> are also equally spaced. In an embodiment where the number of scanning antenna/beams equals the number of donor antenna/beams, the azimuth heading directions of, for example, the first, second and third scanning antennas/beams is the same as the azimuth heading directions of the first, second and third donor antennas/beam - i.e. the two antenna systems are 'aligned' such that their respective antennas/beams are directed to the same azimuth value. This is shown in <FIG> - scanning antenna system <NUM> is aligned with donor antenna system <NUM> on ship <NUM>.

The signals donated by nearby cellular tower are automatically analyzed by the RF network scanning analyser <NUM> which determines, preferably, at least the Cell-Id and the received signal strength. As will be discussed further below, each of the scanning antennas (or beams of a multidirectional scanning antenna) operate according to a timed sequence pattern. The signal information is determined by the RF network scanning analyser <NUM>. Information is passed from the RF network scanning analyser <NUM> to controller <NUM>.

Controller <NUM> controls operation of the scanning antenna system <NUM> according to defined criteria, such that only one of the three scanning antennas/beams are operating and therefore receiving signal and network data at any one time. Operation of the scanning antenna system <NUM> is sequenced such that a first scanning antenna/beam is operating for a set time period, and, on expiry of the set time period, a second scanning antenna/beam is operational for the same set time period, and, on expiry of that time period, a third scanning antenna/beam is operational for the same set time period. The sequenced operation of the scanning antenna system <NUM> then begins again such that the sequenced operation is continuous.

Only a single feeding line per antenna/beam (for both the scanning and donor antenna systems) is required. Both the donor and scanning antenna system are connected to multiple individual coaxial cables each - one per antenna or beam. Power feed to each of the scanning antennas/beams is by a RF power switch circuitry (not shown, but disposed between the network analyser and the scanning antennas) comprising a timer. The timer of the switching circuitry is synchronized with the controller <NUM> such that the controller is able to 'match' information received from the RF network scanning analyser <NUM> to a particular scanning antenna/beam.

At the end of the first complete sequence pattern (i.e. after each of the three scanning antennas/beams has been operational for, for example, <NUM> seconds), the controller <NUM> analyses and compares the data received from the RF network scanning analyser <NUM> relating to the signals received from each antenna/beam to determine from which of the three antennas/beams the 'best' data was received. Determining which data is 'best' is based on predefined criteria. The criteria will depend on the specific circumstances of each implementation and the controller can be reconfigured accordingly. For example, the predefined criteria could comprise, solely, signal strength. The 'best' data will therefore be the strongest signal. The best data may be determine by an algorithm to take account of coverage, signal strength, available networks, etc..

Optimum donor signals for retransmission are those that satisfy minimum coverage and capacity requirements. Their maximum retransmission distance should be less than the technology allows (after adding radio propagation delays due to amplification and filtration). For example, a donor cell signal could be of better coverage at the location of retransmission interest but of limited capacity (i.e. the donor cell is serving high traffic on mainland hotspots). Such signals are generally undesirable for use in cellular repeater applications.

Once the best data (and the particular scanning antenna/beam which provided that best data) has been determined, the controller <NUM> controls operation of the donor antenna <NUM> based on the known direction of the scanning antenna which provided the best data. Three donor antennas/beams are depicted in <FIG>. The azimuth heading value of each donor antenna is, similarly to the scanning antenna, equally separated from each of the other antenna by <NUM> degrees.

RF power switch circuitry is also connected to the donor antenna system <NUM>, disposed between the bi-directional amplifier and the donor antennas. After the selection process is completed, controller <NUM> instructs the second RF power switch module to operate a donor antenna/beam which is equivalently orientated (in terms of azimuth heading value) to the scanning antenna/beam which provided the optimum donor signals (as determined by controller <NUM>). The RF feeding to the bi-directional amplifier is changed accordingly. It will be appreciated that the analysis and determination by the controller <NUM> will occur while the second sequenced pattern is underway. At the end of every complete sequence of operation of the scanning antenna system <NUM> (e.g. after <NUM> seconds (<NUM> seconds scanning for each scanning antenna/beam)), the controller determines the particular donor antenna/beam which is to be in operation until the current sequence of operation of the scanning antenna system <NUM> is complete (after which the controller <NUM> again determines which donor antenna/beam to switch on). In one embodiment, there may be a period of time (shorter than a complete sequence of operation of the scanning antenna system) immediately following the end of a complete sequence during which the earlier, existing donor antenna/beam is active as well as the new donor antenna/beam - i.e. there is an overlap in donor antenna/beam operation to facilitate base station handover.

In an alternative embodiment, the scanning antenna system and donor antenna system are combined by use of dual polarization antennas. In this configuration, a single triple-sector dual-polarization multi-band antenna system (such as, for example, a Galtronics Extent T5622 or a Kathrein <NUM>/<NUM> or similar), housed under a single radome, operates as both the scanning and donor antenna systems. Each antenna/sector has a dual polarisation (such that each antenna/sector operates as a pair of antennas) e.g. cross polarisation at +<NUM> degrees and -<NUM> degrees. A single polarisation acts as a single scanning or donor antenna. Each antenna/sector (i.e. each pair) has a donor and scanning feeding line (a coaxial cable). A controller therefore receives <NUM> feeding lines to RF ports of the controller. A high power RF switch PCB comprises the repeater system driver connection (while also serving as the physical connection to the donor antenna system). The controller controls operation of the scanning antennas in a similar manner to that described above. The controller collects the received mobile signals from the scanning antenna systems, analyses and compares the information received from each scanning antenna (in real or near- real time) and outputs an operational instruction to the high power RF switch. The high power RF switch PCB connects the repeater system with the respective donor antenna system according to the determination (as discussed above), by the controller, of which scanning antenna provides optimal signals. Use of a dual polarisation antenna system saves space (particularly relevant on a vehicle) and cost.

In alternative embodiments, there may be more or less than three scanning antennas/beams. The higher the number of beams that can be provided from the multi-beam directional external antenna systems (donor and receiving) in the azimuth plane, the higher the retransmission gain (donor) and the positioning accuracy (receiving) of the donor cell tower signals.

Different RF power switch configurations, e.g. <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM> RF power switch modules, for different time patterns, e.g. <NUM>, <NUM>, <NUM> seconds time periods and for different multi-beam directional external antenna receivers, e.g. four, eight, sixteen beams, may be employed.

A single directional scanning antenna is re-positioned at set time intervals by a motorised azimuth alignment device in order to scan <NUM> degrees of the azimuth plane in a specified time period.

A single directional donor antenna is also be re-positioned by a motorised azimuth alignment device in accordance with the controller determination regarding optimum received signals. In this embodiment, a motorised azimuth alignment device re-position the scanning antenna and/or the donor antenna, the antennas comprise a built-in GPS module. An azimuth alignment device, under control of the controller, steers the scanning and donor antenna <NUM>° in the horizontal plane. The scanning antenna is readjusted at pre-defined time intervals by a pre-defined angle. The time intervals and extent of movement about the azimuth plane after each time interval will depend on the specific circumstances such as coverage, speed of movement, etc. Synchronisation of the antenna and controller timers and operation of the RF network analyser is similar to that discussed above. After the scanning antenna has collected signal information at equally spaced angles about the azimuth plane for a time period (preferably equal for each antenna) sufficient to collect a sufficient amount of data for the network analyser to analyse the signals, the controller determines the direction from which the optimal signals were received and instructs an azimuth alignment device to re-position the single directional donor antenna such that the direction of the main beam is the same as the direction of the main beam of the scanning antenna at which the optimum signals were received.

Both the scanning and donor azimuth alignment device have a build-in GPS module, a differential GPS module (D-GPS), and/or a gyroscopic compass such that the azimuth alignment device can accurately determine the direction of the antenna with respect to a particular reference, such as grid or true North.

The main beam azimuth direction of both the scanning and donor directional antennas are aligned initially (i.e. when installed) to the vessel's bow, or at a known offset from the bow. Preferably, the antenna is re-positioned with respect to the vessel's bow. Since the direction of the antenna with respect to North can be determined, and the initial position of the antenna with respect to the bow is known, it is possible to determine the direction of the antenna (when not in the initial position) relative to the bow (and therefore the direction of movement of the vessel). A build-in optical encoder and/or an electrical potentiometer module enable the azimuth alignment device to align the antenna relative to the vessel's direction of movement which in turn is relative to North.

Preferably, the azimuth alignment device is able to re-position the antenna heading by a maximum of <NUM>° at any one time. Given the relative narrow vertical plane radiation of directional antennas, the relatively low movement speeds of vessels and relative high long between the ship and donor cell towers, the azimuth alignment device attached to the selected directional donor external antenna readjusts the donor antenna to a high accuracy. In some embodiments, a control system of the azimuth alignment device receives an antenna movement command from an external triggering module. A motor of the alignment device moves an antenna mounting bracket and locks the antenna bracket in the desired position.

Azimuth alignment devices are discussed in the applicant's prior published patent applications <CIT> and <CIT>.

A single directional scanning antenna may be used with a single directional donor antenna. A single directional scanning antenna could be used with a multidirectional donor antenna system comprising multiple antennas/beams and similarly a multidirectional scanning antenna system comprising one or more scanning antenna/beams could be used with a single directional donor antenna.

Claim 1:
A mobile vehicle antenna system (<NUM>), comprising:
a scanning antenna system (<NUM>) comprising a scanning antenna configured to receive from base stations, for at least a first azimuth heading value and a second azimuth heading value, data comprising mobile communication signals and network parameters, wherein the scanning antenna system comprises a first azimuth alignment device configured to steer the scanning antenna <NUM> degrees in the azimuth plane;
a donor antenna system (<NUM>) comprising a donor antenna configured to receive and transmit mobile communication signals to and from a base station, wherein the donor antenna system comprises a second azimuth alignment device configured to steer the donor antenna <NUM> degrees in the azimuth plane,
a controller (<NUM>) connected to the scanning antenna system and the donor antenna system, wherein the controller is configured to:
receive, process and compare the data comprising received mobile communication signals and network parameters for the at least first azimuth heading value and the second azimuth heading value;
determine whether the first azimuth heading value or the second azimuth heading value provides optimal mobile communication signals and network parameters according to predefined criteria; and
control operation of the second azimuth alignment device in accordance with the determination to position the donor antenna such that the direction of a main beam of the donor antenna is the same as the direction of a main beam of the scanning antenna at which the optimal mobile communication signals and network parameters were received.