PATENT DOCUMENT

Abstract:
A device ( 110 ) receives consecutive negative acknowledgments (NACKs) ( 540 ), measures a downlink channel quality ( 530 ) associated with the device ( 110 ), and triggers autonomous retransmission ( 430 ) when power is limited in the device ( 110 ), when the device ( 110 ) is using a minimum usable enhanced dedicated channel (E-DCH) transport format combination (ETFC), and when one of a number of consecutive NACKs ( 540 ) is greater than a predefined number, or the measured downlink channel quality ( 530 ) is less than a predefined threshold.

Full Description:
TECHNICAL FIELD 
     Embodiments described herein relate generally to wireless communication systems, and more particularly, to automatic detection of erroneous connections between antenna ports and radio frequency (RF) paths. 
     BACKGROUND 
     Smart antennas (also known as adaptive array antennas, a multi-antenna system, multiple antennas, and multiple input, multiple output (MIMO) antennas) may be used with wireless communication devices, such as base stations (also referred to as “Node Bs”). Smart antennas are antenna arrays with smart signal processing algorithms that are used to identify spatial signal information (e.g., a direction of arrival (DOA) of the signal) and to calculate beamforming vectors. The beamforming vectors are used to track and locate an antenna beam associated with a target user equipment (e.g., a mobile telephone). 
     Smart antennas have two main functions—DOA estimation and beamforming. During generation of a beam, each smart antenna uses weights for beamforming. Different antennas may have different weights and may transmit different data. Current time division-synchronous code division multiple access (TD-SCDMA) based devices (e.g., base stations) may include four to eight antennas. Each antenna is connected, via a cable, to the base station (e.g., a radio base station (RBS) or a remote radio unit (RRU)). In such an arrangement, if a cable is connected to an incorrect antenna, an incorrect beam is generated and performance is decreased. However, manually checking incorrect or erroneous connections is time consuming and tedious. 
     One proposed solution to this problem is to automatically detect an incorrect connection between an antenna port and a RF path. In the proposed solution, an uplink-received signal is collected and a channel is detected. The channel can be detected with the uplink-received signal. The uplink-received signal is used to detect a maximum energy by traveling in all possible orders of an antenna array vector and in all possible spatial directions. Specifically, the uplink-received signal is used to calculate a correlation matrix, and all possible arrangements of an antenna weighting factor sequence are traversed to obtain a weighting factor matrix. After searching through all directions of space, a maximum value of different weighting factor arrangements is determined, and an arrangement corresponding to the maximum received power is chosen to be a current connection order. However, the proposed solution requires an uplink signal, which means that the proposed solution can only be used with an operational wireless communication network or with extra equipment that generates the uplink signal. 
     SUMMARY 
     It is an object of the invention to overcome at least some of the above disadvantages and to automatically detect a connection error with a base station (or a RRU) without the need for an operational wireless communication network or extra equipment that generates an uplink signal. 
     Embodiments described herein may automatically detect a connection error in a smart antenna (e.g., of a base station or a RRU) by measuring an amplitude and/or a phase between antenna ports of the smart antenna. In one embodiment, for example, in order to transmit and receive signals accurately, every antenna element, RF cable, and transceiver making up the smart antenna may need to operate identically. This means that every transmitting and receiving link may need to have the same amplitude and phase response. The base station may automatically implement a smart antenna calibration procedure that includes compensating the amplitude and phase of each transmitting and receiving link. 
     During antenna calibration, the base station (or the RRU) may measure amplitude and phase of an impulse response of a circuit between an antenna port and a calibration port. The base station (or the RRU) may also measure the amplitude and phase between any two antenna ports. A smart antenna vendor may provide a table that includes amplitude and phase information between any two antenna ports of the smart antenna. The base station (or the RRU) may compare the values provided in the antenna vendor&#39;s table with the measured amplitude and phase between two antenna ports. If there is a large difference between the table values and the measured values, the base station (or the RRU) may determine that there is an antenna connection error. 
     In an exemplary embodiment, a base station may determine an amplitude and/or phase between antenna elements of the base station, and may measure, based on the determined amplitude/phase, an amplitude/phase between corresponding antenna ports of the base station. The base station may compare the measured amplitude/phase with an expected amplitude/phase of the antenna ports to determine an error, and may compare the determined error to a threshold. The base station may determine an erroneous antenna port connection when the error exceeds the threshold, and may determine a correct antenna port connection when the error is less than or equal to the threshold. 
     In another exemplary embodiment, the base station may determine a squared error between the measured amplitude/phase and the expected amplitude/phase, and may compare the squared error to the threshold to determine whether the squared error is greater than the threshold and zero or whether the squared error is less than or equal to the threshold. 
     In another exemplary embodiment, the base station may receive antenna port permutations for multiple antenna ports of the base station, and may receive expected value information associated with the multiple antenna ports. The base station may calculate expected values for different antenna port permutations based on the received information, and may acquire measured values associated with the different antenna port permutations. The base station may compare the expected values for the different antenna port permutations with the measured values for the different antenna port permutations to determine errors for the different antenna port permutations, and may determine an optimal antenna port permutation to be one of the different antenna port permutations with the smallest determined error. 
     Such an arrangement may ensure that connection errors are automatically and easily detected, and that performance issues, due to connection errors, are minimized. The arrangement may not require an uplink signal, and thus may not require an operational wireless communication network or extra equipment to generate an uplink signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a diagram of an exemplary network in which systems and/or methods described herein may be implemented; 
         FIG. 2  illustrates a diagram of exemplary components of a base station depicted  FIG. 1 ; 
         FIGS. 3A and 3B  depict diagrams of further exemplary components of the base station illustrated in  FIG. 1 ; 
         FIG. 4  depicts a diagram of exemplary components of an antenna bank illustrated in  FIGS. 3A and 3B ; 
         FIG. 5  illustrates a diagram of exemplary interactions among exemplary components of a portion of the antenna bank depicted in  FIG. 4 ; 
         FIG. 6  illustrates a diagram of additional exemplary components of the base station depicted  FIG. 1 ; 
         FIGS. 7 and 8  depict diagrams of exemplary functional components of the base station illustrated in  FIG. 1 ; 
         FIGS. 9 and 10  illustrate flow charts of an exemplary process for automatically detecting a connection error in a smart antenna according to embodiments described herein; and 
         FIG. 11  depicts a flow chart of an exemplary process for determining an optimal antenna port permutation in a smart antenna according to embodiments described herein. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. Also, the following detailed description does not limit the invention. 
     Embodiments described herein may automatically detect a connection error in a smart antenna (e.g., of a base station or a RRU) by measuring an amplitude and/or a phase between antenna ports of the smart antenna and by comparing the measured amplitude/phase to an expected amplitude/phase. The automatic detection techniques described herein may be used to quickly and easily detect connection errors in a smart antenna, and may prevent performance problems due to connection errors. 
       FIG. 1  depicts a diagram of an exemplary network  100  in which systems and/or methods described herein may be implemented. As shown, network  100  may include two user equipment (UEs)  110 - 1  and  110 - 2  (referred to collectively, and in some instances individually, as “user equipment  110 ”) and a base station  120 . Two pieces of user equipment  110  and a single base station  120  have been illustrated in  FIG. 1  for simplicity. In practice, there may be more UEs  110  and/or base stations  120 . Also, in some instances, a component in network  100  (e.g., one or more of user equipment  110  and/or base station  120 ) may perform one or more functions described as being performed by another component or group of components in network  100 . 
     User equipment  110  may include one or more devices capable of sending/receiving voice and/or data to/from base station  120 . In one embodiment, user equipment  110  may include, for example, a wireless telephone, a personal digital assistant (PDA), a laptop computer, etc. User equipment  110  may receive information from base station  120 , and may generate and provide information to base station  120 . 
     In one embodiment, base station  120  (also referred to as a “Node B”) may be associated with a radio access network (RAN) (not shown). The RAN may include one or more devices for transmitting voice and/or data to user equipment  110  and a core network (not shown). The RAN may include a group of base stations  120  and a group of radio network controllers (RNCs). The RNCs may include one or more devices that control and manage base station  120 . The RNCs may also include devices that perform data processing to manage utilization of radio network services. The RNCs may transmit/receive voice and data to/from base station  120 , other RNCs, and/or the core network. 
     A RNC may act as a controlling radio network controller (CRNC), a drift radio network controller (DRNC), or a serving radio network controller (SRNC). A CRNC may be responsible for controlling the resources of base station  120 . On the other hand, an SRNC may serve particular user equipment  110  and may manage connections towards that user equipment  110 . Likewise, a DRNC may fulfill a similar role to the SRNC (e.g., may route traffic between a SRNC and particular user equipment  110 ). 
     Base station  120  may include one or more devices that receive voice and/or data from the RNCs (not shown) and transmit that voice and/or data to user equipment  110  via an air interface. Base station  120  may also include one or more devices that receive voice and/or data from user equipment  110  over an air interface and transmit that voice and/or data to the RNCs or other user equipment  110 . 
     In one embodiment, base station  120  may determine an amplitude and/or phase between antenna elements of base station  120 , and may measure, based on the determined amplitude/phase, an amplitude/phase between corresponding antenna ports of base station  120 . Base station  120  may compare the measured amplitude/phase with an expected amplitude/phase of the antenna ports to determine an error, and may compare the deter mined error to a threshold. Base station  120  may determine an erroneous antenna port connection when the error exceeds the threshold, and may determine a correct antenna port connection when the error is less than or equal to the threshold. 
     In another embodiment, base station  120  may receive antenna port permutations for multiple antenna ports of base station  120 , and may receive expected information associated with the multiple antenna ports. Base station  120  may calculate expected values for different antenna port permutations based on the received information, and may acquire measured values associated with the different antenna port permutations. Base station  120  may compare the expected values for the different antenna port permutations with the measured values for the different antenna port permutations to determine errors for the different antenna port permutations, and may determine an optimal antenna port permutation to be one of the different antenna port permutations with the smallest determined error. 
       FIG. 2  illustrates a diagram of exemplary components of base station  120 . As shown in  FIG. 2 , base station  120  may include a group of antennas  210 - 1  through  210 - 8  (referred to collectively as “antennas  210 ” and in some instances, individually as “antenna  210 ”), a group of transceivers (TX/RX)  220 - 1  through  220 - 8  (referred to collectively as “transceivers  220 ” and in some instances, individually as “transceiver  220 ”), a processing system/RRU  230 , and an Iub interface (I/F)  240 . 
     Antennas  210  may include one or more directional and/or omni-directional antennas. In one embodiment, antennas  210  may be associated with a smart antenna of base station  120 . Although eight antennas  210  are shown in  FIG. 2 , in other embodiments, base station  120  may include more or less than eight antennas  210 . 
     Transceivers  220  may be associated with corresponding antennas  210  and may include transceiver circuitry for transmitting and/or receiving symbol sequences in a network, such as network  100 , via antennas  210 . 
     Processing system/RRU  230  may control the operation of base station  120 . Processing system/RRU  230  may also process information received via transceivers  220  and Iub interface  240 . Processing system/RRU  230  may further measure quality and strength of connection, may determine the frame error rate (FER), and may transmit this information to a RNC (not shown). In one embodiment, processing system  230  may be part of a RRU that is associated with base station  120 . As illustrated, processing system/RRU  230  may include a processing unit  232  and a memory  234  (e.g., that includes an expected value table  236 ). 
     Processing unit  232  may include one or more processors, microprocessors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or the like. Processing unit  232  may process information received via transceivers  220  and Iub interface  240 . The processing may include, for example, data conversion, forward error correction (FEC), rate adaptation, Wideband Code Division Multiple Access (WCDMA) spreading/dispreading, quadrature phase shift keying (QPSK) modulation, etc. In addition, processing unit  232  may generate control messages and/or data messages, and may cause those control messages and/or data messages to be transmitted via transceivers  220  and/or Iub interface  240 . Processing unit  232  may also process control messages and/or data messages received from transceivers  220  and/or Iub interface  240 . 
     Memory  234  may include a random access memory (RAM), a read-only memory (ROM), and/or another type of memory to store data and instructions that may be used by processing unit  232 . As further shown in  FIG. 2 , memory  234  may include an expected value table  236 . Expected value table  236  may be a table (e.g., provided by a vendor or a manufacturer of base station  120 ) that includes amplitude and/or phase information between any two antenna ports of base station  120 . As shown in an exemplary embodiment of expected value table  236  (provided below), the amplitude between two antennas (e.g., two of antennas  210 ) may be different. Amplitude may be provided in decibels (dB) and phase may be provided in degrees (deg). Parameter “S12” may represent antenna port “ 1 ” as an input port and antenna port “ 2 ” as an output port. Base station  120  may measure amplitude/phase between two particular antennas and may compare the measured values with corresponding values provided in expected value table  236  (e.g., for the two particular antennas). If there is a large difference (e.g., greater than a particular threshold) between the measured values and the values provided in expected value table  236 , base station  120  may determine that there is an antenna connection error. 
     
       
         
               
             
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Expected Value Table 
               
             
          
           
               
                   
                 Frequency 
               
             
          
           
               
                 Parameter 
                 1880 
                 1900 
                 1920 
                 2010 
                 2018 
                 2025 
               
               
                   
               
             
          
           
               
                 S11 
                 Amplitude[dB] 
                 32.42 
                 27.73 
                 21.2 
                 20.49 
                 19.89 
                 19.95 
               
               
                   
                 Phase[deg] 
                 60.44 
                 17.67 
                 −148.27 
                 6.51 
                 −19.83 
                 −53.81 
               
               
                 S12 
                 Amplitude[dB] 
                 20.73 
                 20.99 
                 21.26 
                 21.62 
                 21.66 
                 21.64 
               
               
                   
                 Phase[deg] 
                 −90.77 
                 151.7 
                 34.94 
                 −126.48 
                 −174.91 
                 143.09 
               
               
                 S13 
                 Amplitude[dB] 
                 27.8 
                 29.71 
                 30.43 
                 29.75 
                 29.91 
                 30.25 
               
               
                   
                 Phase[deg] 
                 73.64 
                 −43.67 
                 −166.86 
                 22.2 
                 −27.41 
                 −69.84 
               
               
                 S14 
                 Amplitude[dB] 
                 35.38 
                 33.61 
                 34.32 
                 35.9 
                 38.18 
                 40.83 
               
               
                   
                 Phase[deg] 
                 −127.64 
                 106.61 
                 7.69 
                 177.5 
                 132.83 
                 88.39 
               
               
                 S15 
                 Amplitude[dB] 
                 32.97 
                 34.53 
                 36.41 
                 36.92 
                 38.17 
                 39.6 
               
               
                   
                 Phase[deg] 
                 −81.33 
                 174.69 
                 53.5 
                 −83.76 
                 −123.12 
                 −160.59 
               
               
                 S16 
                 Amplitude[dB] 
                 34.1 
                 32.46 
                 31.41 
                 29.63 
                 30.33 
                 31.21 
               
               
                   
                 Phase[deg] 
                 68.84 
                 −50.64 
                 −145.01 
                 40.11 
                 −4.94 
                 −46.26 
               
               
                 S17 
                 Amplitude[dB] 
                 34.1 
                 35.06 
                 39.57 
                 39.79 
                 39.8 
                 38.83 
               
               
                   
                 Phase[deg] 
                 110.02 
                 5.61 
                 −135.61 
                 75.77 
                 15.1 
                 −34.45 
               
               
                 S18 
                 Amplitude[dB] 
                 32.75 
                 32.57 
                 32.82 
                 34.31 
                 34.59 
                 34.94 
               
               
                   
                 Phase[deg] 
                 −107.36 
                 126.67 
                 9.76 
                 −175.88 
                 136.23 
                 93.41 
               
               
                 S1cal 
                 Amplitude[dB] 
                 26.03 
                 25.99 
                 25.95 
                 25.58 
                 25.51 
                 25.41 
               
               
                   
                 Phase[deg] 
                 134.94 
                 115.65 
                 96.72 
                 12.53 
                 5.2 
                 −1.44 
               
               
                 S22 
                 Amplitude[dB] 
                 28.94 
                 26.21 
                 17.56 
                 17.06 
                 18.78 
                 21.24 
               
               
                   
                 Phase[deg] 
                 83.67 
                 −62.23 
                 −147.6 
                 105.45 
                 64.93 
                 18.2 
               
               
                 S23 
                 Amplitude[dB] 
                 21.49 
                 21.56 
                 21.74 
                 22.64 
                 22.75 
                 22.87 
               
               
                   
                 Phase[deg] 
                 −73.63 
                 165.77 
                 49.22 
                 −118.43 
                 −165.95 
                 152.11 
               
               
                 S24 
                 Amplitude[dB] 
                 27.89 
                 29.38 
                 30.06 
                 30.3 
                 30.29 
                 30.48 
               
               
                   
                 Phase[deg] 
                 60.22 
                 −62.74 
                 166.26 
                 −7.96 
                 −56.5 
                 −99.25 
               
               
                 S25 
                 Amplitude[dB] 
                 31.61 
                 31.68 
                 31.76 
                 33.08 
                 33.33 
                 33.59 
               
               
                   
                 Phase[deg] 
                 115.27 
                 −66.65 
                 −115.9 
                 62.5 
                 15.88 
                 −25.2 
               
               
                 S26 
                 Amplitude[dB] 
                 26.71 
                 28.25 
                 28.63 
                 26.6 
                 26.82 
                 26.89 
               
               
                   
                 Phase[deg] 
                 −59.76 
                 170.94 
                 40.38 
                 −124.01 
                 −174.69 
                 141.46 
               
               
                 S27 
                 Amplitude[dB] 
                 28.33 
                 29.73 
                 31.28 
                 28.78 
                 29.27 
                 29.9 
               
               
                   
                 Phase[deg] 
                 88.08 
                 −37.85 
                 −152.45 
                 42.32 
                 −7.34 
                 −47.57 
               
               
                 S28 
                 Amplitude[dB] 
                 35.99 
                 36.3 
                 36.51 
                 36.9 
                 36.59 
                 36.16 
               
               
                   
                 Phase[deg] 
                 93.27 
                 −20.23 
                 −146.15 
                 60.79 
                 15.59 
                 −24.07 
               
               
                 S2cal 
                 Amplitude[dB] 
                 26.3 
                 26.26 
                 26.14 
                 25.32 
                 25.26 
                 25.3 
               
               
                   
                 Phase[deg] 
                 137.11 
                 116.41 
                 98.33 
                 12.91 
                 4.61 
                 −2.33 
               
               
                 S33 
                 Amplitude[dB] 
                 16.47 
                 20 
                 28.62 
                 24.77 
                 27.31 
                 33.8 
               
               
                   
                 Phase[deg] 
                 −129.33 
                 161.77 
                 −171.52 
                 113.47 
                 80.98 
                 26.54 
               
               
                 S34 
                 Amplitude[dB] 
                 21.09 
                 21.14 
                 21.37 
                 21.89 
                 21.89 
                 21.84 
               
               
                   
                 Phase[deg] 
                 −97.45 
                 144.5 
                 24.71 
                 −141.86 
                 168.66 
                 125.85 
               
               
                 S35 
                 Amplitude[dB] 
                 36.5 
                 36.56 
                 36.92 
                 38.47 
                 38.2 
                 38.14 
               
               
                   
                 Phase[deg] 
                 64.79 
                 −53.85 
                 −174.55 
                 34.34 
                 −9.47 
                 −47.73 
               
               
                 S36 
                 Amplitude[dB] 
                 29.97 
                 30.37 
                 32.47 
                 32.05 
                 31.94 
                 32 
               
               
                   
                 Phase[deg] 
                 129.78 
                 18.06 
                 −108.25 
                 82.51 
                 33.59 
                 −8.47 
               
               
                 S37 
                 Amplitude[dB] 
                 25.66 
                 26.42 
                 27.65 
                 29.64 
                 30.88 
                 32 
               
               
                   
                 Phase[deg] 
                 −78.74 
                 169.76 
                 50.16 
                 −98.08 
                 −146.41 
                 169.01 
               
               
                 S38 
                 Amplitude[dB] 
                 31.71 
                 31.44 
                 31.51 
                 29.22 
                 29.36 
                 29.67 
               
               
                   
                 Phase[deg] 
                 78.9 
                 −36.28 
                 −150.27 
                 42 
                 −4.52 
                 −45.92 
               
               
                   
               
             
          
         
       
     
     Iub interface  240  may include one or more line cards that allow base station  120  to transmit data to and receive data from a RNC. 
     As described herein, base station  120  may perform certain operations in response to processing unit  232  executing software instructions of an application contained in a computer-readable medium, such as memory  234 . In one example, a computer-readable medium may be defined as a physical or logical memory device. A logical memory device may include memory space within a single physical memory device or spread across multiple physical memory devices. The software instructions may be read into memory  234  from another computer-readable medium or from another device via antennas  210  and transceivers  220 . The software instructions contained in memory  234  may cause processing unit  232  to perform processes described herein. Alternatively, hardwired circuitry may be used in place of or in combination with software instructions to implement processes described herein. Thus, embodiments described herein are not limited to any specific combination of hardware circuitry and software. 
     Although  FIG. 2  shows exemplary components of base station  120 , in other embodiments, base station  120  may contain fewer, different, differently arranged, or additional components than depicted in  FIG. 2 . In still other embodiments, one or more components of base station  120  may perform one or more other tasks described as being performed by one or more other components of base station  120 . 
       FIGS. 3A and 3B  depict diagrams of further exemplary components of base station  120 . As shown in  FIG. 3A , base station  120  may include an antenna bank  300  that includes eight ports  310 - 1  through  310 - 8  (referred to collectively as “ports  310 ” and in some instances, individually as “port  310 ”) connected to corresponding antennas  210 - 1  through  210 - 8 , and a calibration port  310 -CAL. Antennas  210  may include the features described above in connection with, for example,  FIG. 2 . 
     Antenna bank  300  may include a device that enables antennas  210  to connect to transceivers  220  ( FIG. 2 ) of base station  120 , via cables. In one embodiment, antenna bank  300  may include an antenna bank for a dual-polarized eight antenna system, as shown in  FIG. 3A . In another embodiment, antenna bank  300  may include an antenna bank for a normal eight antenna system. 
     Each of ports  310 - 1  through  310 - 8  may include a port capable of connecting one of antennas  210  to one of transceivers  220  ( FIG. 2 ), via a cable. Each of ports  310 - 1  through  310 - 8  may be capable of connecting to a variety of cable connector types, including male connectors, female connectors, optical connectors, electrical connectors, SubMiniature version A (SMA) connectors, threaded Neill-Concelman (TNC) connectors, Bayonet Neill-Concelman (BNC) connectors, etc. 
     Calibration port  310 -CAL may include a port capable of connecting antenna port  300  to one of transceivers  220  ( FIG. 2 ), via a cable. Calibration port  310 -CAL may be capable of connecting to a variety of cable connector types, including male connectors, female connectors, optical connectors, electrical connectors, SMA connectors, TNC connectors, BNC connectors, etc. 
     As shown in  FIG. 3B , antenna bank  300  may connect antennas  210  (omitted from  FIG. 3B  for clarity) to corresponding transceivers  220 , via ports  310  and RF cables  320 . Transceivers  220  may communicate with processing system/RRU  230 . Transceivers  220  and processing system/RRU  230  may include the features described above in connection with, for example,  FIG. 2 . Antenna bank  300  and ports  310  may include the features described above in connection with, for example,  FIG. 3A . 
     Each of RF cables  320  may include a cable that transmits high frequency signals. RF cables  320  may include cables capable of connecting ports  310  to corresponding transceivers  220 . RF cables  320  may include a variety of cable connector types, including male connectors, female connectors, optical connectors, electrical connectors, SMA connectors, TNC connectors, BNC connectors, etc. 
     As further shown in  FIG. 3B , port  310 - 1  (and antenna  210 - 1 ) may connect to transceiver  220 - 1  via one of RF cables  320 , port  310 - 2  (and antenna  210 - 2 ) may connect to transceiver  220 - 2  via one of RF cables  320 , port  310 - 3  (and antenna  210 - 3 ) may connect to transceiver  220 - 3  via one of RF cables  320 , port  310 - 4  (and antenna  210 - 4 ) may connect to transceiver  220 - 4  via one of RF cables  320 , port  310 - 5  (and antenna  210 - 5 ) may connect to transceiver  220 - 5  via one of RF cables  320 , port  310 - 6  (and antenna  210 - 6 ) may connect to transceiver  220 - 6  via one of RF cables  320 , port  310 - 7  (and antenna  210 - 7 ) may connect to transceiver  220 - 7  via one of RF cables  320 , port  310 - 8  (and antenna  210 - 8 ) may connect to transceiver  220 - 8  via one of RF cables  320 , and port  310 -CAL may connect to transceiver  220 -CAL via one of RF cables  320 . In such an arrangement there is a possibility that one of RF cables  320  may be incorrectly connected to one of ports  310  (e.g., one of antennas  210 ), which may generate an incorrect beam and may decrease performance of base station  120 . Embodiments described automatically detect and enable correction of such connection errors. 
     Although  FIGS. 3A and 3B  show exemplary components of base station  120 , in other embodiments, base station  120  may contain fewer, different, differently arranged, or additional components than depicted in  FIGS. 3A and 3B . In still other embodiments, one or more components of base station  120  may perform one or more other tasks described as being performed by one or more other components of base station  120 . 
       FIG. 4  depicts a diagram of exemplary components of antenna bank  300 . As shown, antenna bank  300  may include antennas  210 , ports  310 , calibration port  310 -CAL, loads  400 , directional couplers  410 , and power splitters  420 . Antennas  210  may include the features described above in connection with, for example,  FIG. 2 . Ports  310  and calibration port  310 -CAL may include the features described above in connection with, for example,  FIGS. 3A and 3B .  FIG. 4  shows multiple loads  400 , directional couplers  410 , and power splitters  420 , although only a few of them are labeled (for clarity). 
     Each of loads  400  may include a device connected to an output (e.g., one of ports  310 ) of a circuit. In one embodiment, each of loads  400  may include a device where power is consumed. 
     Each of directional couplers  410  may include a passive device that couples a portion of transmission power in a transmission line (e.g., a line connected to antenna  210 - 1 ) by a particular amount out through another port. In one embodiment, each of directional couplers  410  may use two transmission lines set close enough together such that energy passing through one transmission line (e.g., a line connected to antenna  210 - 1 ) is coupled to the other transmission line (e.g., a line connecting two loads  400 ). 
     Each of power splitters  420  may include a passive device that receives an input signal and generates multiple output signals with specific phase and amplitude characteristics. In one embodiment, each of power splitters  420  may include a “T” connection, which has one input and two outputs. If the “T” connection is mechanically symmetrical, a signal applied to the input may be divided into two output signals, equal in amplitude and phase. 
     Although  FIG. 4  shows exemplary components of antenna bank  300 , in other embodiments, antenna bank  300  may contain fewer, different, differently arranged, or additional components than depicted in  FIG. 4 . In still other embodiments, one or more components of antenna bank  300  may perform one or more other tasks described as being performed by one or more other components of antenna bank  300 . 
       FIG. 5  illustrates a diagram of exemplary interactions among exemplary components of a portion  500  of antenna port  300 . As shown, portion  500  of antenna bank  300  may include antennas  210 - 1  and  210 - 2 , ports  310 - 1  and  310 - 2 , loads  400 , and directional couplers  410 . Antennas  210 - 1  and  210 - 2  may include the features described above in connection with, for example,  FIG. 2 . Ports  310 - 1  and  310 - 2  may include the features described above in connection with, for example,  FIGS. 3A and 4B . Loads  400  and directional couplers  410  may include the features described above in connection with, for example,  FIG. 4 . 
     As further shown in  FIG. 5 , antennas  210 - 1  and  210 - 2  may be internally coupled together via a circuit that includes loads  400  and directional couplers  410 . For example, an input signal  510  may be input at port  310 - 1 , may travel through the circuit, and may be received as an output signal  520  at port  310 - 2 . Antennas  210 - 1  and  210 - 2  may be externally coupled together via wireless wave propagation between antennas  210 - 1  and  210 - 2 . For example, input signal  510  may cause antenna  210 - 1  to transmit a wireless signal  530  that may be received by antenna  210 - 2  and provided to port  310 - 2 . The external coupling of antennas  210 - 1  and  210 - 2  may depend on a physical environment (e.g., a very site specific environment) of base station  120  and antennas  210 - 1  and  210 - 2 . In one embodiment, a filter may be provided (e.g., with antennas  210 - 1  and  210 - 2 ) that filters out surrounding objects of the physical environment. 
     Base station  120  may use signals  510 - 530  to measure an amplitude and/or a phase between antennas  210 - 1  and  210 - 2  (and ports  310 - 1  and  310 - 2 ). Base station  120  may compare the values provided in expected value table  236  ( FIG. 2 ) with the measured amplitude and/or measured phase between antennas  210 - 1  and  210 - 2  (and ports  310 - 1  and  310 - 2 ). If there is a large difference (e.g., greater than a particular threshold (e.g., +/−ten percent)) between the table values and the measured amplitude and/or phase, base station  120  may determine that there is an antenna connection error. 
     Although  FIG. 5  shows exemplary interactions among components of antenna bank  300 , in other embodiments, components of antenna bank  300  may perform fewer, different, or additional interactions than depicted in  FIG. 5 . 
       FIG. 6  illustrates a diagram of additional exemplary components of base station  120 . As shown base station  120  may include a first transceiver  220 - 1  that includes digital-to-analog converter (DAC) circuitry  600 , a power amplifier  605 , and a filter unit (FU)  610 ; a second transceiver  220 - 2  that includes a filter unit  615  and analog-to-digital converter (ADC) circuitry  620 ; and processing unit  232 . Transceivers  220 - 1  and  220 - 2  and processing unit  232  may include the features described above in connection with, for example,  FIG. 2 . 
     DAC circuitry  600  may include a device or circuitry that converts a digital signal (e.g., binary code or numbers) to an analog signal (e.g., current, voltage, or electric charge). In one embodiment, DAC circuitry  600  may include one or more of a pulse width modulator DAC, an oversampling DAC, an interpolating DAC, a binary weighted DAC, etc. 
     Power amplifier  605  may include a device that changes (e.g., increases) an amplitude of a signal (e.g., a voltage, a current, etc.). In one embodiment, power amplifier  605  may include one or more of a transistor amplifier, an operational amplifier, a fully differential amplifier, etc. 
     Each of filter units  610  and  615  may include an electronic circuit that performs signal processing functions to remove unwanted frequency components from a signal, to enhance desired frequency components in the signal, or both. In one embodiment, each of filter units  610  and  615  may include one or more of a passive filter unit, an active filter unit, an analog filter unit, a digital filter unit, a high-pass filter unit, a low-pass filter unit, a bandpass filter unit, band-reject filter unit, an all-pass filter unit, a discrete-time filter unit, a continuous-time filter unit, a linear filter unit, a non-linear filter unit, an infinite impulse response filter unit, a finite impulse response filter unit, etc. 
     ADC circuitry  620  may include a device or circuitry that converts an analog signal (e.g., current, voltage, or electric charge) to a digital signal (e.g., binary code or numbers). In one embodiment, ADC circuitry  620  may include one or more of a linear ADC, a non-linear ADC, a direct conversion ADC, a successive-approximation ADC, a ramp-compare ADC, etc. 
     As further shown in  FIG. 6 , in order to calibrate antennas  210  associated with transceivers  220 - 1  and  220 - 2 , processing unit  232  may provide a digital transmission (TX) signal  625  to transceiver  220 - 1 , and DAC circuitry  600  may receive digital TX signal  625 . DAC circuitry  600  may convert digital TX signal  625  to an analog TX signal  630 , and may provide analog TX signal  630  to power amplifier  605 . Power amplifier  605  may amplify analog TX signal  630  to produce an amplified, analog TX signal  635 , and may provide amplified, analog TX signal  635  to filter unit  610 . Filter unit  610  may filter amplified, analog TX signal  635  to produce a signal  640  (e.g., which is a filtered, amplified, and analog TX signal), and may provide signal  640  to a coupling network. The coupling network may include, for example, the internally and externally coupled antennas  210 - 1  and  210 - 2  and ports  310 - 1  and  310 - 2  shown in  FIG. 5 . 
     Signal  640  may be input to port  310 - 1  as input signal  510  ( FIG. 5 ), and may travel through the coupling network until it reaches port  310 - 2  as output signal  520  ( FIG. 5 ). Output signal  520  may be provided to transceiver  220 - 2  as an analog reception (RX) signal  645 , and filter unit  615  may receive analog RX signal  645 . Filter unit  615  may filter analog RX signal  645  to produce a filtered, analog RX signal  650 , and may provide filtered, analog RX signal  650  to ADC circuitry  620 . ADC circuitry  620  may convert filtered, analog RX signal  650  to a digital RX signal  655 , and may provide digital RX signal  655  to processing unit  232 . 
     Processing unit  232  may compare digital TX signal  625  and digital RX signal  655  to determine a measured value (e.g., a difference between digital TX signal  625  and digital RX signal  655 ) of amplitude and/or phase. Since the amplitude and phase provided by transceivers  220 - 1  and  220 - 2  may be known, processing unit  232  may calculate an amplitude and/or phase between antenna ports (e.g., ports  310 - 1  and  310 - 2 , which are associated with antennas  210 - 1  and  210 - 2 ) based on the measured value and the known amplitude and phase provided by transceivers  220 - 1  and  220 - 2 . Processing unit  232  may compare the values provided in expected value table  236  ( FIG. 2 ) with the measured amplitude and/or phase between the antenna ports (e.g., ports  310 - 1  and  310 - 2 ). If there is a large difference (e.g., greater than a particular threshold (e.g., +/−ten percent)) between the table values and the measured amplitude and/or phase, processing unit  232  may determine that there is an antenna connection error. 
     Although  FIG. 6  shows exemplary components of base station  120 , in other embodiments, base station  120  may contain fewer, different, differently arranged, or additional components than depicted in  FIG. 6 . In still other embodiments, one or more components of base station  120  may perform one or more other tasks described as being performed by one or more other components of base station  120 . 
       FIG. 7  depicts a diagram of exemplary functional components of base station  120 . As shown, base station  120  may include a measured value determiner  700 , a measured/expected value comparer  710 , and an error/threshold comparer  720 . In one embodiment, the functions described in connection with  FIG. 7  may be performed by processing unit  232  ( FIG. 2 ). 
     Measured value determiner  700  may include any hardware, software, or combination of hardware and software that may receive digital TX signal  625  and digital RX signal  655 . Measured value determiner  700  may compare digital TX signal  625  and digital RX signal  655  to determine a difference between the amplitude and/or the phase of digital TX signal  625  and digital RX signal  655 . Since the amplitude and phase provided by transceivers  220  may be known, measured value determiner  700  may calculate a measured value (S measured )  730  (e.g., an amplitude and/or phase between two antenna ports  310 ) based on the determined difference and the known amplitude and phase provided by transceivers  220 . Measured value determiner  700  may provide measured value  730  to measure/expected value comparer  710 . 
     Measured/expected value comparer  710  may include any hardware, software, or combination of hardware and software that may receive measured value  730  from measured value determiner  700 , and may receive an expected value (S expected )  740  from expected value table  236 . Measured/expected value comparer  710  may compare measured value (S measured )  730  and expected value (S expected )  740 . In one embodiment, measured/expected value comparer  710  may determine a difference between measured value (S measured )  730  and expected value (S expected )  740  (i.e., S measured −S expected ) to be an error (ε)  750 , and may square error (ε)  750  according to the following squared matrix norm (e.g., the squared Frobenius norm):
 
ε 2   =∥S   measured   −S   expected ∥ F   2 ,
 
where S measured  and S expected  may denote measured and expected complex value S-matrices. A complex S-matrix may contain all the S-parameters (e.g., an (i, j) element of the S-matrix may contain a parameter (Sij), which may represent an amplitude and phase between ports i and j in complex form).
 
     Error/threshold comparer  720  may include any hardware, software, or combination of hardware and software that may receive error (ε)  750  from measured/expected value comparer  710 , and may compare the squared error  750  to a threshold (δ THRESH ). Since a measurement error may always be present, a few decibels (e.g., one to five decibels) or few degree (e.g., one to five degrees) margin may be added as the threshold. Error/threshold comparer  720  may determine that a port connection (e.g., in base station  120 ) is erroneous (as indicated by reference number  760 ) if the squared error  750  is greater than the threshold (e.g., ε 2 &gt;δ THRESH &gt;0). Error/threshold comparer  720  may determine that a port connection (e.g., in base station  120 ) is correct (as indicated by reference number  770 ) if the squared error  750  is less than or equal to the threshold (e.g., ε 2 ≦δ THRESH ). 
     Although  FIG. 7  shows exemplary functional components of base station  120 , in other embodiments, base station  120  may contain fewer, different, differently arranged, or additional functional components than depicted in  FIG. 7 . In still other embodiments, one or more functional components of base station  120  may perform one or more other tasks described as being performed by one or more other functional components of base station  120 . 
       FIG. 8  illustrates a diagram of exemplary functional components of base station  120 . As shown, base station  120  may include an expected values calculator  800  and a measured/expected values comparer  810 . In one embodiment, the functions described in connection with  FIG. 8  may be performed by processing unit  232  ( FIG. 2 ). 
     Expected values calculator  800  may include any hardware, software, or combination of hardware and software that may receive port permutations  820  (e.g., different combinations of antennas  210 , ports  310 , and RF cables  320 ) for multiple antenna ports  310  of base station  120 , and may receive table information  830  (e.g., expected values from expected value table  236  ( FIG. 2 )) associated with the multiple antenna ports  310 . Expected values calculator  800  may calculate expected values  840  (e.g., S-matrices) for different antenna port permutations based on port permutations  820  and table information  830 . Expected values calculator  800  may provide expected values  840  to measured/expected values comparer  810 . 
     Measured/expected values comparer  810  may include any hardware, software, or combination of hardware and software that may receive expected values  840  from expected values calculator  800 , and may acquire measured values  850  associated with the different antenna port permutations. Measured/expected values comparer  810  may compare expected values  840  with measured values  850  to determine errors for the different antenna port permutations. Measured/expected values comparer  810  may determine an optimal antenna port permutation (i.e., a correct port order  860 ) to be one of the different antenna port permutations with a smallest determined error  870  (e.g., as determined by: ε 2 =∥S measured −S expected ∥ F   2 ). 
     Although  FIG. 8  shows exemplary functional components of base station  120 , in other embodiments, base station  120  may contain fewer, different, differently arranged, or additional functional components than depicted in  FIG. 8 . In still other embodiments, one or more functional components of base station  120  may perform one or more other tasks described as being performed by one or more other functional components of base station  120 . 
       FIGS. 9 and 10  illustrate flow charts of an exemplary process  900  for automatically detecting a connection error in a smart antenna according to embodiments described herein. In one embodiment, process  900  may be performed by base station  120 . In other embodiments, some or all of process  900  may be performed by base station  120  in combination with another device (e.g., a RRU) or group of devices (e.g., communicating with base station  120 ). 
     As illustrated in  FIG. 9 , process  900  may include determining an amplitude/phase between antenna elements of a base station (block  910 ), and measuring, based on the determined amplitude/phase, an amplitude/phase (S measured ) between corresponding antenna ports of the base station (block  920 ). For example, in embodiments described above in connection with  FIG. 7 , measured value determiner  700  of base station  120  may receive digital TX signal  625  and digital RX signal  655 . Measured value determiner  700  may compare digital TX signal  625  and digital RX signal  655  to determine a difference between the amplitude and/or the phase of digital TX signal  625  and digital RX signal  655 . Since the amplitude and the phase provided by transceivers  220  may be known, measured value determiner  700  may calculate measured value (S measured )  730  (e.g., an amplitude and/or phase between two antenna ports  310 ) based on the determined difference and the known amplitude and phase provided by transceivers  220 . 
     Returning to  FIG. 9 , the measured amplitude/phase (S measured ) may be compared with an expected amplitude/phase (S expected ) of the antenna ports to determine an error (block  930 ), and the determined error may be compared to a threshold (block  940 ). For example, in embodiments described above in connection with  FIG. 7 , measured/expected value comparer  710  of base station  120  may receive measured value  730  from measured value determiner  700 , and may receive expected value (S expected )  740  from expected value table  236 . Measured/expected value comparer  710  may compare measured value (S measured )  730  and expected value (S expected )  740 . In one example, measured/expected value comparer  710  may determine a difference between measured value (S measured )  730  and expected value (S expected )  740  (i.e., S measured −S expected ) to be an error (ε)  750 . Error/threshold comparer  720  of base station  120  may receive error (ε)  750  from measured/expected value comparer  710 , and may compare the squared error  750  to a threshold (δ THRESH ). In one example, the threshold (e.g., for the amplitude and phase values) may be set equal to a product of a particular percentage (e.g., ten percent) and the amplitude and phase values provided in expected value table  236 . 
     As further shown in  FIG. 9 , an erroneous antenna port connection may be determined when the error exceeds the threshold (block  950 ), and a correct antenna port connection may be determined when the error is less than or equal to the threshold (block  960 ). For example, in embodiments described above in connection with  FIG. 7 , error/threshold comparer  720  of base station  120  may determine that a port connection (e.g., in base station  120 ) is erroneous (as indicated by reference number  760 ) if the squared error  750  exceeds the threshold (δ THRESH ). Error/threshold comparer  720  may determine that a port connection (e.g., in base station  120 ) is correct (as indicated by reference number  770 ) if the squared error  750  is less than or equal to the threshold (δ THRESH ). 
     Process blocks  930  and  940  may include the process blocks depicted in  FIG. 10 . As shown in  FIG. 10 , process blocks  930  and  940  may include determining a squared error (ε 2 ) between the measured amplitude/phase (S measured ) and the expected amplitude/phase (S expected ) according to ε 2 =∥S measured −S expected ∥ F   2  (block  1000 ), and comparing the squared error (ε 2 ) to the threshold (δ THRESH ) to determine whether ε 2 &gt;δ THRESH &gt;0 or ε 2 ≦δ THRESH  (block  1010 ). For example, in embodiments described above in connection with  FIG. 7 , measured/expected value comparer  710  of base station  120  may determine a difference between measured value (S measured )  730  and expected value (S expected )  740  (i.e., S measured −S expected ) to be error (ε)  750 , and may square error (ε)  750  according to the following squared matrix norm (e.g., the squared Frobenius norm): ε 2 =∥S measured −S expected ∥ F   2 . Error/threshold comparer  720  of base station may compare the squared error  750  to a threshold (δ THRESH ). Error/threshold comparer  720  may determine that a port connection (e.g., in base station  120 ) is erroneous (as indicated by reference number  760 ) if the squared error  750  greater than the threshold (e.g., ε 2 &gt;δ THRESH &gt;0). Error/threshold comparer  720  may determine that a port connection (e.g., in base station  120 ) is correct (as indicated by reference number  770 ) if the squared error  750  is less than or equal to the threshold (e.g., ε 2 ≦δ THRESH ). 
       FIG. 11  illustrates a flow chart of another exemplary process  1100  for determining an optimal antenna port permutation in a smart antenna according to embodiments described herein. In one embodiment, process  1100  may be performed by base station  120 . In other embodiments, some or all of process  1100  may be performed by base station  120  in combination with another device (e.g., a RRU) or group of devices (e.g., communicating with base station  120 ). 
     As illustrated in  FIG. 11 , process  1100  may include receiving antenna port permutations and amplitudes/phases for antenna ports of a base station (block  1110 ), and calculating expected amplitudes/phases for different antenna port permutations based on the received information (block  1120 ). For example, in embodiments described above in connection with  FIG. 8 , expected values calculator  800  of base station  120  may receive port permutations  820  (e.g., different combinations of antennas  210 , ports  310 , and RF cables  320 ) for multiple antenna ports  310  of base station  120 , and may receive table information  830  (e.g., expected values from expected value table  236  ( FIG. 2 )) associated with the multiple antenna ports  310 . Expected values calculator  800  may calculate expected values  840  (e.g., S-matrices) for different antenna port permutations based on port permutations  820  and table information  830 . 
     As further shown in  FIG. 11 , measured amplitudes/phases associated with the antenna port permutations may be acquired (block  1130 ), the expected amplitudes/phases may be compared with the measured amplitudes/phases to determine errors (block  1140 ), and an optimal antenna port permutation may be determined to be a permutation with the smallest error (block  1150 ). For example, in embodiments described above in connection with  FIG. 8 , measured/expected values comparer  810  of base station  120  may acquire measured values  850  associated with the different antenna port permutations, and may compare expected values  840  with measured values  850  to determine errors for the different antenna port permutations. Measured/expected values comparer  810  may determine an optimal antenna port permutation (i.e., a correct port order  860 ) to be one of the different antenna port permutations with a smallest determined error  870  (e.g., as determined by: ε 2 =∥S measured −S expected ∥ F   2 ). 
     Embodiments described herein may automatically detect a connection error in a smart antenna (e.g., of a base station or RRU) by measuring an amplitude and/or a phase between antenna ports of the smart antenna. In one embodiment, for example, in order to transmit and receive signals accurately, every antenna element, RF cable, and transceiver making up the smart antenna may need to operate identically. This means that every transmitting and receiving link may need to have the same amplitude and phase response. The base station may automatically implement a smart antenna calibration procedure that includes compensating the amplitude and phase of each transmitting and receiving link. 
     Such an arrangement may ensure that connection errors are automatically and easily detected, and that performance issues due to connection errors are minimized. The arrangement may not require an uplink signal, and thus may not require an operational wireless communication network or extra equipment to generate an uplink signal. 
     Embodiments described herein provide illustration and description, but are not intended to be exhaustive or to limit the implementations to the precise form disclosed. Modifications and variations are possible in light of the above teachings, or may be acquired from practice of the implementations. For example, while series of blocks have been described with regard to  FIGS. 9-11 , the order of the blocks may be modified in other embodiments. Further, non-dependent blocks may be performed in parallel. In another example, although the systems and/or methods described herein have been implemented in base station  120 , in other embodiments, the systems and/or methods may be implemented in any device that uses antenna bank  300 . 
     The exemplary embodiments, as described above, may be implemented in many different forms of software, firmware, and hardware in the implementations illustrated in the figures. The actual software code or specialized control hardware used to implement the exemplary embodiments described herein is not limiting of the invention. Thus, the operation and behavior of the exemplary embodiments were described without reference to the specific software code—it being understood that one would be able to design software and control hardware to implement the exemplary embodiments based on the description herein. 
     Further, certain portions of the invention may be implemented as “logic” that performs one or more functions. This logic may include hardware, such as an application specific integrated circuit, a field programmable gate array, a processor, or a microprocessor, or a combination of hardware and software. 
     Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the invention. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. 
     It should be emphasized that the terms “comprises/comprising” when used in the this specification are taken to specify the presence of stated features, integers, steps, or components, but do not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. 
     No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Where only one item is intended, the terns “one” or similar language is used. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.