Patent Publication Number: US-2012026040-A1

Title: Method, Apparatus, Computer Program and a Computer Readable Storage Medium

Description:
FIELD OF THE INVENTION 
     Embodiments of the present invention relate to a method, apparatus, computer program and a computer readable storage medium. In particular, they relate to a method, apparatus, computer program and a computer readable storage medium in a base station. 
     BACKGROUND TO THE INVENTION 
     Apparatus, such as base stations, usually include a transceiver and an antenna array for communicating with other apparatus, such as mobile cellular telephones. The antenna array includes a plurality of antennas which, through constructive and destructive interference, form a radiation pattern having one or more main lobes. 
     When the base station is initially set up, it may require calibration so that it may accurately orient the main lobe towards another apparatus and thereby efficiently transmit signals to, and/or receive signals from the other apparatus. Usually, base stations are calibrated using dedicated hardware which is relatively expensive. 
     It would therefore be desirable to provide an alternative apparatus. 
     BRIEF DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION 
     According to various, but not necessarily all, embodiments of the invention there is provided a method comprising: calculating a parameter for controlling a main lobe of a radiation pattern of an antenna array, the calculation using a direction of a location relative to the antenna array, the direction determined from information including a position of the location; determining a parameter for controlling the main lobe of the radiation pattern of the antenna array from a signal received at the antenna array from the location; and determining an offset using the parameter calculated from the determined direction and the parameter determined from the received signal. 
     The method may further comprise calibrating an apparatus using the determined offset. 
     The method may be for calibrating a receiver and/or a transmitter of an apparatus. 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus comprising: a processor configured to: calculate a parameter, for controlling a main lobe of a radiation pattern of an antenna array, using a direction of a location relative to the antenna array, the direction determined from information including a position of the location; to determine a parameter for controlling the main lobe of the radiation pattern of the antenna array from a signal received at the antenna array from the location; and to determine an offset using the parameter calculated from the determined direction and the parameter determined from the received signal. 
     The apparatus may be for wireless communication. 
     The processor may be configured to calibrate the apparatus using the determined offset. 
     According to various, but not necessarily all, embodiments of the invention there is provided a module comprising an apparatus as described in the above paragraph. 
     According to various, but not necessarily all, embodiments of the invention there is provided an electronic device comprising an apparatus as described in the above paragraph. 
     According to various, but not necessarily all, embodiments of the invention there is provided a computer program that, when run on a computer, performs: calculating a parameter for controlling a main lobe of a radiation pattern of an antenna array, the calculation using a direction of a location relative to the antenna array, the direction determined from information including a position of the location; determining a parameter for controlling the main lobe of the radiation pattern of the antenna array from a signal received at the antenna array from the location; and determining an offset using the parameter calculated from the determined direction and the parameter determined from the received signal. 
     The computer program may perform, when run on a computer, calibrating an apparatus using the determined offset. 
     According to various, but not necessarily all, embodiments of the invention there is provided a computer program that, when run on a computer, performs the method described in the above paragraph. 
     According to various, but not necessarily all, embodiments of the invention there is provided a computer readable storage medium encoded with instructions that, when executed by a processor, perform: calculating a parameter for controlling a main lobe of a radiation pattern of an antenna array, the calculation using a direction of a location relative to the antenna array, the direction determined from information including a position of the location; determining a parameter for controlling the main lobe of the radiation pattern of the antenna array from a signal received at the antenna array from the location; and determining an offset using the parameter calculated from the determined direction and the parameter determined from the received signal. 
     The computer readable storage medium may be encoded with instructions that, when executed by a processor perform calibrating an apparatus using the determined offset. 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus comprising: means for calculating a parameter for controlling a main lobe of a radiation pattern of an antenna array, the calculation using a direction of a location relative to the antenna array, the direction determined from information including a position of the location; means for determining a parameter for controlling the main lobe of the radiation pattern of the antenna array from a signal received at the antenna array from the location; and means for determining an offset using the parameter calculated from the determined direction and the parameter determined from the received signal. 
     According to various, but not necessarily all, embodiments of the invention there is provided a method comprising: determining a direction of a location relative to an antenna array, using information including a position of the location; and controlling a main lobe of a radiation pattern of the antenna array using the determined direction. 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus comprising a processor configured to determine a direction of a location relative to an antenna array, using information including a position of the location; and controlling a main lobe of a radiation pattern of the antenna array using the determined direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of various examples of embodiments of the present invention reference will now be made by way of example only to the accompanying drawings in which: 
         FIG. 1  illustrates a schematic diagram of an apparatus according to various embodiments of the present invention and a further apparatus; 
         FIG. 2  illustrates a flow diagram of a method of calibrating a receiver according to various embodiments of the present invention; 
         FIG. 3  illustrates a flow diagram of a method of calibrating a transmitter according to various embodiments of the present invention; 
         FIG. 4  illustrates a schematic diagram of a system including an apparatus according to various embodiments of the present invention; 
         FIG. 5  illustrates a schematic diagram of another system including an apparatus according to various embodiments of the present invention; and 
         FIG. 6  illustrates a schematic diagram of a further system including an apparatus according to various embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION 
       FIGS. 2 and 3  illustrate a method comprising: calculating a parameter for controlling a main lobe  32  of a radiation pattern  30  of an antenna array  18 , the calculation using a direction of a location relative to the antenna array  18 , the direction determined from information  28  including a position of the location; determining a parameter for controlling the main lobe  32  of the radiation pattern  30  of the antenna array  18  from a signal received at the antenna array  18  from the location; and determining an offset using the parameter calculated from the determined direction and the parameter determined from the received signal. 
       FIG. 1  illustrates a schematic diagram of an apparatus  10  according to various embodiments of the present invention. The apparatus  10  includes a processor  12 , a memory  14 , a transceiver  16  and an antenna array  18 . 
     In the following description, the wording ‘connect’ and ‘couple’ and their derivatives mean operationally connected/coupled. It should be appreciated that any number or combination of intervening components can exist (including no intervening elements). Additionally, it should be appreciated that the connection/coupling may be a physical galvanic connection and/or an electromagnetic connection. 
     The apparatus  10  may be any electronic device and may be a base station for a cellular network (also referred to as a radio base station (RBS) or a base transceiver station (BTS) in the art) or a module for such a device. As used here, ‘module’ refers to a unit or apparatus that excludes certain parts/components that would be added by an end manufacturer or a user. For example, a module may not include the antenna array  18 . 
     The electronic components that provide the processor  12 , the memory  14 , and the transceiver  16  may be interconnected via a printed wiring board (PWB). In various embodiments, the printed wiring board  22  may be a flexible printed wiring board. 
     The implementation of the processor  12  can be in hardware alone (e.g. a circuit etc), have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware). The processor  12  may be any suitable processor and may include a microprocessor  12   1  and memory  12   2 . The processor  12  may be implemented using instructions that enable hardware functionality, for example, by using executable computer program instructions in a general-purpose or special-purpose processor that may be stored on a computer readable storage medium (e.g. disk, memory etc) to be executed by such a processor. 
     The processor  12  is configured to read from and write to the memory  14 . The processor  12  may also comprise an output interface  20  via which data and/or commands are output by the processor  12  and an input interface  22  via which data and/or commands are input to the processor  12 . 
     The memory  14  may be any suitable memory and may, for example be permanent built-in memory such as flash memory or it may be a removable memory such as a hard disk, secure digital (SD) card or a micro-drive. The memory  14  stores a computer program  24  comprising computer program instructions that control the operation of the apparatus  10  when loaded into the processor  12 . The computer program instructions  24  provide the logic and routines that enables the apparatus  10  to perform the methods illustrated in  FIGS. 2 and 3 . The processor  12  by reading the memory  14  is able to load and execute the computer program  24 . 
     The computer program instructions  24  provide: computer readable program means for calculating a parameter for controlling a main lobe of a radiation pattern of an antenna array, the calculation using a direction of a location relative to the antenna array, the direction determined from information including a position of the location; computer readable program means for determining a parameter for controlling the main lobe of the radiation pattern of the antenna array from a signal received at the antenna array from the location; and computer readable program means for determining an offset using the parameter calculated from the determined direction and the parameter determined from the received signal. 
     The computer program  24  may arrive at the apparatus  10  via any suitable delivery mechanism  26 . The delivery mechanism  26  may be, for example, a computer-readable storage medium, a computer program product, a memory device, a record medium such as a CD-ROM, DVD or Blu-Ray Disc, an article of manufacture that tangibly embodies the computer program  24 . The delivery mechanism may be a signal configured to reliably transfer the computer program  24 . The apparatus  10  may propagate or transmit the computer program  24  as a computer data signal. 
     Although the memory  14  is illustrated as a single component it may be implemented as one or more separate components some or all of which may be integrated/removable and/or may provide permanent/semi-permanent/dynamic/cached storage. 
     References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single /multi-processor architectures and sequential (e.g. Von Neumann)/parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other devices. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc. 
     The memory  14  also stores information  28  relating to locations, objects, topography and other apparatus within communication range of the antenna array  18  (i.e. within the ‘cell’ of the apparatus  10 ). In particular, the information  28  may include the position (latitude, longitude and height above sea level), size and distance of objects such as buildings and elevated terrain (e.g. hills) within communication range of the antenna array  18 . The information  28  may also include the position (latitude, longitude and height above sea level) and distance of locations which are in ‘line of sight’ (LOS) of the antenna array  18 . It should be appreciated that other apparatus such as base stations and repeaters may be located at a location which is in ‘line of sight’ of the antenna array  18 . Additionally, the information  28  may include propagation channel data for propagation channels formed from topography and objects (such as buildings) in the communication range of the antenna array  18 . Furthermore, the information  28  may include the position (latitude, longitude and height above sea level) of the antenna array  18 . 
     The transceiver  16  may be a single unit that provides the functionality of a receiver and/or a transmitter. Alternatively, the transceiver  16  may be a separate receiver and a separate transmitter. 
     The processor  12  is configured to provide signals to the transceiver  16 . The transceiver  16  is configured to receive and encode the signals from the processor  12  and provide them to the antenna array  18  for transmission. The transceiver  16  is also operable to receive and decode signals from the antenna array  18  and then provide them to the processor  12  for processing. 
     The antenna array  18  may be any antenna array which is suitable for operation in an apparatus such as a base station and includes a plurality of antennas  18   1 ,  18   2 ,  18   3 ,  18   4 . It should be appreciated that the antenna array  18  may include any number of antennas and should not be limited to the number of antennas illustrated in  FIG. 1 . Furthermore, the apparatus  10  may include a plurality of antenna arrays. 
     The antenna array  18  may have matching components between one or more feeds of the antennas  18   1 ,  18   2 ,  18   3 ,  18   4  and the transceiver  16 . These matching components may be lumped components (e.g. inductors and capacitors) or transmission lines, or a combination of both. The antenna array  18  is operable in at least one operational resonant frequency band and may also be operable in a plurality of different radio frequency bands and/or protocols. For example, the different frequency bands and protocols may include (but are not limited to) LTE 700 (US) (698.0-716.0 MHz, 728.0-746.0 MHz), LTE 1500 (Japan) (1427.9-1452.9 MHz, 1475.9-1500.9 MHz), LTE 2600 (Europe) (2500-2570 MHz, 2620-2690 MHz), AM radio (0.535-1.705 MHz); FM radio (76-108 MHz); Bluetooth (2400-2483.5 MHz); WLAN (2400-2483.5 MHz); HLAN (5150-5850 MHz); GPS (1570.42-1580.42 MHz); US-GSM 850 (824-894 MHz); EGSM 900 (880-960 MHz); EU-WCDMA 900 (880-960 MHz); PCN/DCS 1800 (1710-1880 MHz); US-WCDMA 1900 (1850-1990 MHz); WCDMA 2100 (Tx: 1920-1980 MHz Rx: 2110-2180 MHz); PCS1900 (1850-1990 MHz); UWB Lower (3100-4900 MHz); UWB Upper (6000-10600 MHz); DVB-H (470-702 MHz); DVB-H US (1670-1675 MHz); DRM (0.15-30 MHz); Wi Max (2300-2400 MHz, 2305-2360 MHz, 2496-2690 MHz, 3300-3400 MHz, 3400-3800 MHz, 5250-5875 MHz); DAB (174.928-239.2 MHz, 1452.96-1490.62 MHz); RFID LF (0.125-0.134 MHz); RFID HF (13.56-13.56 MHz); RFID UHF (433 MHz, 865-956 MHz, 2450 MHz). An operational frequency band is a frequency range over which an antenna/antenna array can efficiently operate. Efficient operation occurs, for example, when the antenna&#39;s/antenna array&#39;s insertion loss S 11  is greater than an operational threshold such as 4 dB or 6 dB. 
     When in operation, the antenna array  18  has a radiation pattern  30  having a main lobe  32 . The radiation pattern  30  indicates the directional efficiency of the antenna array  18  in receiving and/or transmitting electromagnetic signals. The radiation pattern  30  is formed through constructive and destructive interference from the combination of the plurality of antennas  18   1 ,  18   2 ,  18   3 ,  18   4 . In order to maintain the clarity of  FIG. 1 , the radiation pattern  30  is illustrated as being two dimensional. However, it should be appreciated that the radiation pattern  30  of an antenna array  18  is usually three dimensional. 
     The main lobe  32  of the radiation pattern  30  is the portion of the radiation pattern  30  having the greatest efficiency for receiving and/or transmitting electromagnetic signals. In some embodiments, the radiation pattern  30  may have a single main lobe and in other embodiments, the radiation pattern  30  may have more than one main lobe. The use of a main lobe to transmit signals to, and receive signals from another apparatus, is usually called ‘beam forming’ in the art of radio frequency communications. 
     The orientation and size of the main lobe  32  of the radiation pattern  30  may be controlled, at least partially, by changing at least one parameter. The orientation of the main lobe  32  may be changed by changing the phase coefficient at the transceiver  16  (the phase coefficient sets the phase difference applied to signals received from/provided to each of the plurality of antennas  18   1 ,  18   2 ,  18   3 ,  18   4 ). The size of the main lobe  32  may be changed by changing the amplitude coefficient at the transceiver  16  (the amplitude coefficient sets the amplitude of signals received from/provided to each of the plurality of antennas  18   1 ,  18   2 ,  18   3 ,  18   4 ). 
       FIG. 1  also illustrates another apparatus  34  which may be any wireless communication apparatus such as a base station, a repeater or a portable electronic device (e.g. a mobile cellular telephone). The apparatus  34  may have the same electronic components as, or similar electronic components to, the apparatus  10 . The apparatus  34  is located at a location which is in ‘line of sight’ of the antenna array  18  and has a bearing of θ from the antenna array  18 . 
     The information  28  stored in the memory  14  includes the position (latitude, longitude and height above sea level) of the apparatus  34  and may also include the distance of the apparatus  34  from the antenna array  18 . The information  28  for the apparatus  34  may be pre-stored in the memory  14  or may be provided to the apparatus  10  via a computer readable storage medium or may be included in a signal transmitted from the apparatus  34  itself. 
     The processor  12  may use the information  28  to calibrate the transceiver  16  and thereby increase the efficiency of transmission/reception at the apparatus  10 . This will be explained in more detail in the following paragraphs with reference to  FIGS. 2 and 3 . 
       FIG. 2  illustrates a flow diagram of a method of calibrating a receiver  16  according to various embodiments of the present invention. The method is described with reference to  FIG. 1 . However, it should be appreciated that the method may be applied to other arrangements of apparatus (such as those illustrated in  FIGS. 4 ,  5  and  6 ). 
     At block  36 , the processor  12  determines a direction of the apparatus  34  relative to the antenna array  18  using the information  28 , stored in the memory  14 , for the apparatus  34 . In  FIG. 1 , the direction of the apparatus  34  from the antenna array  18  is at a bearing  8  (azimuth angle in a spherical polar coordinate system). Since the apparatus  34  may be at a different height above sea level to the antenna array  18 , the subsequent angle between them arising from their different heights (zenith angle in a spherical polar coordinate system) is also determined for the direction. In the art of radio communication, the above mentioned direction is usually referred to as the ‘direction of arrival’ (DoA). 
     At block  38 , the processor  12  calculates one or more parameters for controlling the main lobe  32  of the radiation pattern  30 , the calculation using the direction determined in block  36 . In more detail, the processor  12  calculates phase coefficients for the receiver  16  that would, if applied at the receiver  16 , substantially orient the main lobe  32  along the direction determined in block  36 . In various embodiments, the processor  12  may also determine amplitude coefficients using information  28  for the distance of the apparatus  34  from the antenna array  18 . It should be appreciated that the phase and amplitude coefficients calculated in block  38  represent expected or theoretical coefficients that are calculated using the information  28  stored in the memory  14 . 
     At block  40 , the processor  12  determines phase coefficients for the receiver  16  from a signal received at the antenna array  18  and transmitted from the apparatus  34 . The processor  12  may also determine amplitude coefficients for the receiver  16  from the signal received at the antenna array  18 . It should be appreciated that the phase and amplitude coefficients determined in block  40  are coefficients that are measured from a received signal. 
     At block  42 , the processor  12  determines an offset by comparing the coefficients calculated in block  38  with the coefficients measured in block  40 . The determined offset may represent the difference between the expected/theoretical coefficients (e.g. expected/theoretical phase and amplitude coefficients) and the measured coefficients (e.g. measured phase and amplitude coefficients). The determined offset may also represent systematic errors that are introduced to the received signal from the receiver  16  and/or the antenna array  18 . If the antenna array  18  response is known, the processor  12  may determine the offset introduced to the signal by the receiver  16  using the determined offset. 
     At block  44 , the processor  12  calibrates the receiver  16  using the offset determined in block  42 . For example, in subsequent communications the processor  12  may apply the determined offset to calculated coefficients to improve the reception of a received signal. 
       FIG. 3  illustrates a flow diagram of a method of calibrating a transmitter  16  according to various embodiments of the present invention. The method is described with reference to  FIG. 1 . However, it should be appreciated that the method may be applied to other arrangements of apparatus (such as those illustrated in  FIGS. 4 ,  5  and  6 ). 
     At block  46 , the processor  12  determines a direction of the apparatus  34  relative to the antenna array  18  (the ‘direction of arrival’) using the information  28 , stored in the memory  14 , for the apparatus  34 . 
     At block  48 , the processor  12  calculates one or more parameters for controlling the main lobe  32  of the radiation pattern  30 , the calculation using the direction determined in block  36 . In more detail, the processor  12  calculates phase coefficients for the transmitter  16  that would, if applied to the transmitter  16 , substantially orient the main lobe  32  along the direction determined in block  36 . In various embodiments, the processor  12  may also determine amplitude coefficients using information  28  for the distance of the apparatus  34  from the antenna array  18 . It should be appreciated that the phase and amplitude coefficients calculated in block  38  represent expected or theoretical coefficients that are calculated using the information  28  stored in the memory  18 . 
     At block  50 , the processor  12  directs the main lobe  32  of the radiation pattern  30  in a plurality of directions during transmission of a signal to the apparatus  34 . 
     The apparatus  34  receives the signal transmitted from the antenna array  18  and then transmits a signal in reply which includes information indicating received signal strength at the apparatus  34  for substantially each of the plurality of directions. In various embodiments, the apparatus  10  may transmit a signal to the apparatus  34  requesting the apparatus  34  to transmit the received signal strength information. 
     At block  52 , the processor  12  determines phase coefficients for the transmitter  16  using the signal transmitted from the apparatus  34 . In particular, the processor  12  determines which direction of the plurality of directions has the highest received signal strength and then calculates phase coefficients for that direction. The processor  12  may also determine amplitude coefficients for the transmitter  16  from the signal received at the antenna array  18 . 
     At block  54 , the processor  12  determines an offset by comparing the coefficients calculated in block  48  (e.g. expected/theoretical phase and amplitude coefficients) with the coefficients measured in block  52  (e.g. measured phase and amplitude coefficients). The determined offset may represent the difference between the expected/theoretical coefficients and the measured coefficients. The determined offset may also represent systematic errors that are introduced to the transmitted signal from the transmitter  16  and/or the antenna array  18 . If the antenna array  18  response is known, the processor  12  may determine the offset introduced to the signal by the transmitter  16  using the determined offset. 
     At block  56 , the processor  12  calibrates the transmitter  16  using the offset determined in block  54 . For example, in subsequent communications the processor  12  may apply the determined offset to calculated coefficients to improve the transmission of a signal. 
     Embodiments of the present invention may provide an advantage in that they enable a transceiver to be calibrated without requiring dedicated calibration hardware. Since dedicated calibration hardware is relatively expensive, embodiments of the present invention may reduce the cost of calibrating a transceiver. 
     Furthermore, embodiments of the present invention may provide an advantage by improving the transmission and/or reception efficiency of the apparatus  10 . Additionally, embodiments of the present invention may reduce interference within the communication range (i.e. the cell) of the apparatus  10  since the main lobe  32  of the apparatus  10  may be more accurately oriented in a particular direction. 
     The methods described above with reference to  FIGS. 2 and 3  may be used to in an initial calibration of the apparatus  10  and may also be used in a subsequent fine tuning calibration. 
     In one embodiment, for an initial calibration one or more of the methods described with reference to  FIGS. 2 and 3  may be performed for a subset of adjacent antennas (e.g. two adjacent antennas such as antennas  18   1  and  18   2 ) in the antenna array  18 . Then, one or more of the methods may be performed for a different subset of adjacent antennas (e.g. two different adjacent antennas such as antennas  18   3  and  18   4 ) of the antenna array  18 . Optionally, one or more of the methods may be performed to calibrate the combination of the subsets of the antenna array. The one or more methods are repeated until they have been performed for substantially all antennas in the antenna array  18 . The determined offsets for each antenna may then be used to initially calibrate the transceiver  16 . 
     In another embodiment, for an initial calibration one or more of the methods described with reference to  FIGS. 2 and 3  may be performed for a subset of adjacent antennas (e.g. two adjacent antennas such as antennas  18   1  and  18   2 ) in the antenna array  18  to determine their offset. Then, one or more of the methods may be performed for the previously selected subset of antennas (i.e. antennas  18   1  and  18   2 ) and an additional subset of adjacent antennas (which may be one or more antennas such as antenna  18   3 ) to determine an offset for the additional subset of adjacent antennas. Then, one or more of the methods may be performed for the previously selected subset of antennas (i.e. antennas  18   1 ,  18   2 ,  18   3 ) and an additional adjacent subset of antennas (which may be one or more antennas such as antenna  18   4 ) to determine an offset for the additional subset of adjacent antennas. The methods are repeated until they have been performed for substantially all of the antennas in the antenna array  18 . 
     The above initial calibration methods may provide a number of advantages. For example, they may be less computationally intensive for the processor  12  than calibrating all antennas in the antenna array simultaneously. 
     In one embodiment for fine tuning the calibration of the antenna array  18  (with reference to  FIGS. 2 and 3 ), the processor  12  directs the main lobe  32  in a plurality of directions that are centred on the direction determined in blocks  36  and  46  for transmission/reception of a signal in blocks  40  and  50 . For example, if the processor  12  determines in blocks  36  and  46  that the direction of the apparatus  34  is 70°, the processor  12  in blocks  40  and  50  may direct the main lobe  32  in the directions 68°, 69°, 70°, 71° and 72°. 
       FIG. 4  illustrates a schematic diagram of a system  58  including an apparatus  10  according to various embodiments of the present invention and a further apparatus  60 . The further apparatus  60  may be any electronic communication device and may be a base station, a repeater or a portable electronic device such as a mobile cellular telephone. A plurality of buildings  62  are positioned within the communication range of the antenna array  18  of the apparatus  10 . A further building is located at a location  64  which may act as a location of reflection for radio frequency signals. 
     The buildings  62  are located between the apparatus  10  and the further apparatus  60  and consequently, the apparatus  60  is not in the ‘line of sight’ of the antenna array  18  of the apparatus  10 . However, the apparatus  10  and the further apparatus  60  are able to communicate with one another by transmitting signals toward the building at the location  64  which reflects the signal onwards to the destination apparatus. 
     In this example, the memory  14  of the apparatus  10  stores information regarding the position of the location  64  and the processor  12  may calibrate the transceiver  16  by transmitting signals to, and receiving signals from the location  64  and following the methods described above with reference to  FIGS. 2 and 3 . 
       FIG. 5  illustrates a schematic diagram of another system  66  including an apparatus  10  according to various embodiments of the present invention and a further apparatus  68 . The further apparatus  68  may be any portable electronic communication device such as a mobile cellular telephone that includes a location sensor (for example, a GPS receiver). 
     Buildings  70 ,  72  are positioned within the communication range of the antenna array  18  (i.e. the cell of the apparatus  10 ) and consequently restrict the ‘line of sight’ of the antenna array  18 . The buildings  70 ,  72  define an area  74  (denoted by a dotted line in  FIG. 5 ) that is in the ‘line of sight’ of the antenna array  18 . 
     The apparatus  68  is configured to transmit a signal to the apparatus  10  including information regarding the position of the apparatus  68  (obtained via the location sensor). When the apparatus  10  receives the signal from the apparatus  68 , the processor  12  of the apparatus  10  compares the information received from the apparatus  68  with the information  28  stored in the memory  14  and determines whether the apparatus  68  is in the ‘line of sight’ of the antenna array  18  (i.e. whether it is located in the area  74 ). If the apparatus  68  is in the ‘line of sight’ of the antenna array  18 , the processor  12  may calibrate the transceiver  16  using the methods described above with reference to  FIGS. 2 and 3 . 
       FIG. 6  illustrates a schematic diagram of another system  76  including an apparatus  10  according to various embodiments of the present invention and a further apparatus  78 . The further apparatus  78  may be any portable electronic communication device such as a mobile cellular telephone. The system  76  also includes an access point  80  that is installed at a location that is in the line of sight of the antenna array  18  of the apparatus  10 . The access point  80  and/or the further apparatus  78  are configured to determine when the further apparatus  78  is in relatively close proximity to the access point  80 , and then transmit a signal to the apparatus  10  including information indicating that a signal is receivable at the access point  80  and that the processor  12  may calibrate the transceiver  16  using the methods described above with reference to  FIGS. 2 and 3 . 
     For example, the access point  80  may include a radio frequency identification (RFID) reader which is configured to recognize portable electronic devices that are equipped with RFID tags and inform the apparatus  10  accordingly for calibration (e.g. via a landline connection). Alternatively, the access point  80  may include an RFID tag and the further apparatus  78  may include an RFID reader. In this embodiment, the further apparatus  78  informs the apparatus  10  that calibration may commence. In another example, the access point  80  may recognize the further apparatus  78  using a low powered radio frequency network such as Bluetooth and the access point  80  and/or the further apparatus  78  may inform the apparatus  10  that calibration may commence. In yet another example, the access point  80  may recognize the further apparatus  78  using a wireless computer network such as Wireless LAN or WiMax and the access point and/or the further apparatus  78  may inform the apparatus  10  that calibration may commence. 
     The blocks illustrated in the  FIGS. 2 and 3  may represent steps in a method and/or sections of code in the computer program  28 . The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some steps to be omitted. 
     Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. For example, the information  28  relating to another apparatus may not be pre-stored in the memory  14 , but may instead be transmitted from the other apparatus. In these embodiments, the method blocks of determining a direction of a location and then determining a parameter from the determined direction may be performed after the block of determining a parameter from a received signal. For example, in  FIG. 2 , blocks  36  and  38  may be performed after block  40  and in  FIG. 3 , blocks  46  and  48  may be performed after block  52 . 
     In various embodiments, the antenna array  18  may be positioned remote from a base station and may be connected to the base station via a communication link (e.g. optical cables). In these embodiments, the processor  12  may be located at the antenna array  18  and/or at the base station. 
     During initial calibration, the methods described with reference to  FIGS. 2 and 3  may be carried out for antennas which are not adjacent and which may be irregularly spaced relative to one another. 
     Features described in the preceding description may be used in combinations other than the combinations explicitly described. 
     Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. 
     Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. 
     Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon. 
     I/We claim: