JP5701791B2 - Antenna array calibration for wireless communication systems - Google Patents

Description

Priority Claims Under 35 USC 119 and 120 This application is entitled "ANTENNA ARRAY CALIBRATION FOR WIRELESS", the title of the invention filed on November 2, 2005. COMMUNICATION SYSTEMS) ”from US Provisional Patent Application No. 60 / 733,022 under US Patent Act 119 (e), and the name of the invention filed on April 4, 2006 is“ Wireless Both claims claiming benefit under US Patent Act No. 120 to US Patent Application No. 11 / 398,077, “ANTENNA ARRAY CALIBRATION FOR WIRELESS COMMUNICATION SYSTEMS” Is assigned to the assignee of the present application and is expressly incorporated herein by reference.

  The following description relates generally to wireless communications, and more particularly to calibrating an antenna array over-the-air.

  Wireless networking systems have become a common means by which many people around the world communicate. Wireless communication devices have become smaller and higher performance to satisfy consumer needs and to improve portability and convenience. Improvements in processing power in mobile devices such as mobile phones have resulted in increased demand for wireless network transmission systems. Such systems are generally not as easily updated as cellular equipment that communicates through such systems. As mobile device capabilities expand, it may be difficult to maintain older wireless network systems to help fully exploit the capabilities of new and improved wireless devices.

  More specifically, frequency division based techniques generally divide the spectrum into separate channels by dividing the spectrum into uniform chunk bandwidths, eg, frequencies allocated to wireless cellular communications. The division of bandwidth can be divided into channels, each of which can carry voice conversation data or, in the case of a digital service, carry digital data. Each channel can be assigned to only one user at a time. One commonly used variant is an orthogonal frequency division technique that efficiently partitions the entire system bandwidth into multiple orthogonal subcarriers. These subcarriers are also referred to as tones, carriers, bins, and / or frequency channels. Using techniques based on time division, the bandwidth is divided into successive time slices or time slots with respect to time. Each user of the channel is given a time slice to send and receive information in a round robin manner. For example, at any given time t, the user is given access to the channel for a short burst. The access is then switched to another user, who is given a short burst of time to send and receive information. The “alternating” cycle follows, and as a result, each user is given multiple transmission and reception bursts.

  Code division based techniques generally transmit data on several frequencies available at any time within a range. Typically, the data is digitized and spread over the entire available bandwidth, multiple users can be multiplexed on the channel, and a unique code sequence can be assigned to each user. Users can transmit in the same wide-band chunk of spectrum, and each user's signal is spread across the bandwidth by its own unique spreading code. This technique can provide sharing and one or more users can transmit and receive simultaneously. Such sharing can be achieved by spread spectrum digital modulation, where the user bitstream is encoded and spread pseudo-randomly across a very wide channel. The receiver is designed to recognize the associated unique code sequence and undo the randomization in order to collect the bits of a particular user coherently.

  A typical wireless communication network (e.g., using frequency division, time division, and code division techniques) transmits and transmits data within one or more base stations that provide the coverage area and One or more mobile (eg, wireless) terminals capable of receiving. A typical base station may transmit multiple data streams simultaneously for broadcast, multicast, and / or unicast services. A data stream is a stream of individually received data that is of interest to a mobile terminal. Mobile terminals within the coverage area of the base station may be interested in receiving one data stream, two or more data streams, or all data streams carried by a composite stream. . Similarly, a mobile terminal can transmit data to the base station or another mobile terminal. Such communication between the base station and the mobile terminal may be degraded due to channel variations and / or interference power variations. For example, the aforementioned variations may affect base station scheduling, power control, and / or rate prediction for one or more mobile terminals.

  When antenna arrays and / or base stations are used with time domain duplexed (TDD) channel transmission techniques, very large gains can be achieved. An important premise when achieving these gains is that due to the nature of transmit and receive TDD, both the forward link (FL) and reverse link (RL) have similar physics corresponding to a common carrier frequency. Is to observe the dynamic propagation channel. In practice, however, the overall transmit and receive chains that can include analog front ends, digital sampling transmitters and receivers, as well as physical cabling and antenna architectures, are the overall obtainable at the receiver. Contributes to channel response. In other words, the receiver observes the overall or equivalent channel between the input of the transmitter's digital-to-analog converter (DAC) and the output of the receiver's analog-to-digital converter (ADC) and Can comprise an analog chain of transmitters, a physical propagation channel, a physical antenna array structure (including cable connections), an analog receiver chain.

  In view of at least the foregoing, there is a need in the art for systems and / or methods for calibrating antenna arrays used in wireless communication devices.

  In order to provide a basic understanding of one or more embodiments, a simplified overview of such embodiments is presented below. This summary is not an extensive overview of all possible embodiments and is not intended to identify key or critical elements of all embodiments or to delineate the scope of any or all embodiments . Its sole purpose is to briefly present some concepts of one or more embodiments as a prelude to the more detailed description that is presented below.

  According to one aspect, a method for calibrating an antenna array in a wireless network is based on determining calibration based on at least first and second calibration techniques, and then based on one of those techniques. Selecting calibration.

  According to another aspect, a wireless communications apparatus includes at least two antennas and a processor coupled to the at least two antennas. The processor is configured to determine a calibration for communication including at least two antenna calibrations based on at least a first and a second calibration technique and then select a calibration based on one of those techniques. ing.

  According to yet another aspect, the apparatus can comprise means for determining a calibration based at least on the first and second calibration techniques and then selecting a calibration based on one of those techniques.

  To the accomplishment of the above and related ends, one or more embodiments comprise the features fully described below, particularly those recited in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the one or more embodiments. These aspects, however, illustrate only some of the various ways in which the principles of the various embodiments may be used, and the described embodiments include all such aspects and their equivalents. Is intended to be.

FIG. 1 illustrates an aspect of a multiple access wireless communication system. FIG. 2 illustrates an antenna configuration with a receiver chain and a transmitter chain in accordance with various aspects described herein. FIG. 3 shows a timing aspect of the calibration operation. FIG. 4 illustrates aspects of logic that helps calibrate the antenna array to compensate for gain mismatch. FIG. 5 illustrates an aspect of logic that helps calibrate the antenna array to compensate for gain mismatch. FIG. 6 illustrates an aspect of a method for calibrating an antenna array. FIG. 7 illustrates an aspect of a method for calibrating an antenna array. FIG. 8 shows aspects of a receiver and a transmitter in a wireless communication system. FIG. 9 shows an aspect of the access point. FIG. 10 illustrates an aspect of a method for determining the type of calibration to apply.

Detailed description

  Various embodiments are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. However, it will be apparent that such embodiments may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to assist in describing one or more embodiments.

  As used in this application, the terms “component”, “system”, etc. refer to a computer-related entity that is either hardware, a combination of hardware and software, software, or running software. Is intended. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and / or a computer. One or more components may reside in a thread of processing and / or execution, the components may be locally located on one computer, and / or two or more computers It may be distributed on top. In addition, these components can execute from various computer readable media having various data structures stored thereon. The components may communicate by local and / or remote processing, eg, according to a signal having one or more data packets (eg, data from one component is transmitted to the other component in local and distributed systems) And / or interact with the other system via signals over a network such as the Internet).

  Moreover, various embodiments are described herein in connection with a subscriber station. A subscriber station can also be called a system, a subscriber unit, mobile station, mobile, remote station, access point, base station, remote terminal, access terminal, user terminal, user agent, user equipment, and so on. A subscriber station can be a mobile phone, a cordless phone, a Session Initiation Protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device with wireless connectivity, or a wireless modem Other processing devices connected to the computer may be used.

  Moreover, various aspects or features described herein may be implemented as a method, apparatus, or article of manufacture using standard programming and / or engineering techniques. The term “article of manufacture” as used herein is intended to encompass a computer program that can be accessed from any computer-readable device, carrier, or media. For example, computer readable media include, but are not limited to, magnetic storage devices (eg, hard disks, floppy disks, magnetic strips, etc.), optical disks (eg, compact disks (CDs), digital versatile disks (DVDs). ), Etc.), smart cards, flash memory devices (eg, cards, sticks, key drives, etc.), and integrated circuits such as read only memory, programmable read only memory, electrically erasable programmable read only memory Can be included.

  Referring to FIG. 1, a multiple access wireless communication system according to one embodiment is shown. The multiple access wireless communication system 1 includes a plurality of cells, for example, cells 2, 4, and 6. In FIG. 1, each cell 2, 4, and 6 may include an access point that includes multiple sectors. The plurality of sectors is constituted by a group of antennas, and each antenna is involved in communication with an access terminal existing in a part of the cell. In cell 2, antenna groups 12, 14, and 16 each correspond to a different sector. In cell 4, antenna groups 18, 20, and 22 each correspond to a different sector. In cell 6, antenna groups 24, 26, and 28 each correspond to a different sector.

  Each cell includes a number of access terminals that communicate with one or more sectors of each access point. For example, access terminals 30 and 32 communicate with access point base 42, access terminals 34 and 36 communicate with access point 44, and access terminals 38 and 40 communicate with access point 46.

  Controller 50 is coupled to each of cells 2, 4, and 6. The controller 50 can include one or more connections to a plurality of networks, such as, for example, the Internet, other packet-based networks, or circuit switched voice networks, which are connected to the multiple access wireless communication system 1. Information to and from access terminals that communicate with other cells. The controller 50 includes or is coupled to a scheduler that schedules transmissions from and to the access terminal. In another embodiment, the scheduler may reside in each individual cell, each sector of the cell, or a combination thereof.

  To help calibrate transmissions to the access terminal, it is beneficial to calibrate the access point gain calibration loop to address mismatches due to the access point's transmit and receive chains. However, due to noise in the channel, calibration estimates based on signals received at the access terminal on the forward link and signals transmitted from the access terminal on the reverse link may include noise and other channel variations. , May wonder the estimates provided. In order to overcome the effects of channel noise, multiple calibrations for both the forward and reverse links are utilized for multiple access terminals. In certain aspects, multiple transmissions to and from each access terminal are taken into account to perform calibration for a given sector.

  In certain aspects, either the access point transmit chain or the access point receive chain may be calibrated. This is done, for example, by using a calibration ratio to calibrate the access point's receive chain to its transmit chain, or to calibrate its transmit chain to its receive chain. Also good.

  As used herein, an access point may be a fixed station used to communicate with a terminal and may be referred to as a base station, Node B, or some other terminology, May include some or all of the functions. An access terminal may also be called a user equipment (UE), a wireless communication device, a terminal, a mobile station, or some other terminology and may include some or all of their functionality.

  Note that FIG. 1 shows physical sectors, ie, having different antenna groups for different sectors, but other approaches may be utilized. For example, multiple fixed “beams” where each “beam” covers a different area of the cell in frequency space may be utilized instead of or in combination with physical sectors. Such an approach is described and disclosed in co-pending US Patent Application No. 11 / 260,895, whose title is “Adaptive Sectorization In Cellular System”. Patent application No. 11 / 260,895 is incorporated herein.

  With reference to FIG. 2, antenna configuration 100 comprises a receiver chain 102 and a transmitter chain 104 in accordance with various aspects described herein. The receiver chain 102 includes a downconverter component 106 that downconverts to baseband when a signal is received. The downconverter component 106 is operatively connected to an automatic gain control (AGC) function 108 that evaluates the received signal strength and automatically determines the gain applied to the received signal. To maintain the receiver chain 102 within its associated linear operating range and provide a constant signal strength to output through the transmitter chain 104. It will be appreciated that the AGC 108 may be an option for some embodiments described herein (eg, automatic gain control may not necessarily be performed in connection with all embodiments). ). The AGC 108 is operably coupled to an analog-to-digital (A / D) converter 110, which converts the received signal to digital form, after which the signal is digitally low. Smoothed by a pass-pass filter (LPF) 112, the LPF 112 can reduce short-term oscillations in the received signal. Finally, the receiver chain 102 may comprise a receiver processor 114 that may process the received signal and communicate this signal to one or more components of the transmitter chain 104. it can.

  The transmitter chain 104 may comprise a transmitter processor 116 that receives a signal from the receiver chain 102 (eg, the transmitter receives the signal and the signal is received by the receiver chain 102). And various processing related to the components of the receiver chain 102). Transmitter processor 116 is operatively coupled to pulse shaper 118, which can assist in manipulating the transmitted signal, thereby being within a bandwidth limited range. Thus shaping the signal while reducing and / or eliminating intersymbol interference. Once shaped, the signal is subjected to digital-to-analog (D / A) conversion by the D / A converter 120, after which it is operatively associated with the low-frequency band in the transmitter chain 104 for smoothing. A pass filter (LPF) 122 is provided. A pulse amplifier (PA) component 124 can amplify the pulse / signal and then be upconverted to baseband by the upconverter 126.

  An antenna array 100 may exist for each antenna of both the access point and the access terminal. As such, large differences may be observed between the transmission characteristics of the transmitter chain 104 and the receiver chain 102 and / or between samples thereof, and the variation of equivalent channel and / or transmitter / receiver variations. There may be cases where interrelationships cannot be assumed. When calibrating the antenna array 100, the magnitude of the variation in the signal propagated along the transmitter and receiver chains is known in terms of effects on phase and / or amplitude, and the accuracy of the assumed correlation Understanding these effects may be used to assist the calibration process. Furthermore, in the case of an antenna array, each antenna 100 typically has a transmitter chain 104 and a receiver chain 102 that are different from the other antennas. Thus, each different transmitter chain 104 may have a different effect on phase and / or amplitude than any other transmitter chain. The same is true for the receiver chain 102 of each antenna 100.

  The mismatch in impact may be due to the physical structure of the antenna 100, component differences, or some other factor. Such mismatches may include, for example, interconnection effects, tower effects, poor knowledge of component placement, amplitude and / or phase mismatches due to antenna cabling, etc. . Further, the mismatch may be due to hardware components in the transmitter chain 104 and / or receiver chain 102 of each antenna 100. For example, such mismatches may be related to analog filters, I and Q imbalance, low noise or pulse amplifier phase and / or gain mismatches in the chain, various non-linear effects, and the like.

  In an access point, calibrating each transmit chain independently with respect to a corresponding receive chain (ie, a receive chain corresponding to the same antenna) requires complex and potentially tedious processing. Further, at a given access terminal, specific feedback for the forward link transmission or pilot used for the reverse link transmission is subject to noise for that user. Thus, there is some error introduced by channel variations and noise at a given calibration ratio estimated based on both the forward and reverse links. Thus, in some aspects, one or an estimated one or several estimated for several different access terminals to obtain one calibration ratio used by the access point to transmit to one or all access terminals. Multiple calibration ratios are combined. In certain aspects, the combination may be an average of all calibration ratios for each access terminal communicating with the access point, or an average of some predetermined subset. In another aspect, the combination may be in the form of joint optimization, combining channel measurements from and to each access terminal to gain gain for each access terminal. One calibration ratio, which is a matching combination, is estimated without calculating an individual calibration ratio for each access terminal.

  For any given access terminal, the access point uses not only the reverse link channel estimate of this access terminal, but also the forward link channel estimate. Forward link channel estimation is performed at the access terminal and fed back to the access point to estimate or calculate a calibration ratio based on the access terminal.

Forward link channel estimates

Is estimated at the access terminal for transmission from the i th transmit antenna of the access point. However, any channel estimate has a component related to channel noise, along with any gain or distortion generated by the access point transmit chain and the access terminal receive chain. Thus, the channel estimate for the forward link can be written as:

In equation (1), the channel estimates are the gain mismatch β _AT of the receiver chain of the access terminal, the gain mismatch of the transmitter chain of the access point

, A physical channel h _i between the two antennas to be measured, and a function of the channel noise n _i that is part of the channel estimate.

For reverse link transmission, channel estimate at i th receive antenna of access point due to transmission from AT

Is basically the inverse of equation (1). This can be shown in the following equation (2).

In equation (2), this channel estimate is the gain mismatch α _AT of the access terminal transmit chain, the gain mismatch of the access point receiver chain,

, The physical channel h _i between the two antennas to be measured, and the function of the channel noise υ _i that is part of the channel estimate.

In order to calibrate the antenna array, the mismatch error between the receiver chain 102 and the transmitter chain 104 of the antenna 100 is shown in the following equation (3). It should be noted that other methods and mathematical relationships may be used to achieve array calibration in conjunction with or instead of the methods and mathematical relationships described herein.

In Equation (3), c _i is the total mismatch ratio between the reverse link transmission and the forward link transmission, and γ is the gain mismatch ratio between the transmission chain and the reception chain of the access terminal. , Η _i is the mismatch ratio between the receive chain and the transmit chain for the i-th antenna at the access point. Note that γ is substantially constant for each antenna pair at the access point. In a certain aspect, equation (3) is idealized because no noise estimate is included in equation (3).

i = 1,. . . , M, where M is the number of antennas in the antenna array of the access point, and the calibration ratio c _i is one vector for each access terminal

This vector may be referred to as a “calibration vector”.

In equation (4), a vector

This component corresponds to the estimated value of each antenna of the access point for one access terminal. vector

Are complex numbers including amplitude and phase mismatches for each transmit and receive chain of the access point antenna array and common mismatches corresponding to the transmit and receive mismatches of the access terminal transmit and receive chains Note that it may be. Note that equation (4) describes a vector with entries for one access terminal antenna, but may include entries for multiple access terminals.

  The noise vector n includes channel measurement error (MSE) effects and channel measurement uncorrelated effects. This is because gain measurements are performed at different times, which can cause channel variations over time, temperature variations, and other variations that affect the measurement.

Estimated calibration vector corresponding to access terminal u

May be determined as shown in equation (5) below.

Here, γ _u is a gain mismatch corresponding to the transmission chain and the reception chain of the access terminal, and η is a mismatch vector corresponding to the transmission chain and the reception chain of the antenna array of the access point. vector

Is determined for all antennas in the antenna array of the access point.

  In the above, it should be noted that there are several ways to combine different calibration vector estimates (corresponding to measurements from different access terminals) to produce an overall or combined calibration vector. One way to perform this combination is to average all calibration vector estimates to obtain one estimate.

In this approach, each calibration vector estimate includes a different multiplicative factor γ _u for different access terminals. If one or more access terminals have a very large gain mismatch γ _u , the simple average may result in a skewed result s for the access terminal having the largest gain mismatch γ _u .

In another aspect, each calibration vector estimate corresponding to a particular access terminal is normalized based on vector elements. This may provide for minimization if one or more access terminals have a large gain mismatch γ _u . This process is expressed by the following equation (6).

In certain aspects, as long as the element to normalize is the same element for each calibration vector estimate, that element can be any element of the calibration vector, for example, the first element. Note that you may. Next, the sum of the normalized elements is a vector

Divided by the total number of elements U.

Another approach that may be used to combine different calibration vector estimates may be based on combining estimated vectors as a matrix. For example, in certain aspects, each calibration vector estimate is a rotated and scaled version of the same vector η, and the rotation and scaling may be due to different access terminal mismatches γ _u . One way to remove this scaling and rotation is to first normalize each calibration vector to have a unit norm. Next, a matrix Q whose columns are normalized calibration vector estimates may be constructed from the calibration vectors. One estimate for the calibration vector is obtained by performing matrix decomposition, eg, singular value decomposition for matrix Q. For example, as shown in equation (7), the eigenvector corresponding to the largest singular value may be used as the total calibration vector estimate.

  As illustrated in the three approaches described above, the calibration ratio is generally estimated in two steps. Initially, values corresponding to elements of the calibration vector are calculated for the individual access terminals, for the antenna array, or for the antenna of interest. The calibration vectors are then combined based on one or more mathematical processes.

An alternative to calculating multiple calibration vectors is to use a joint optimization procedure with multiple access points and access measurements as follows. In some cases, access terminals and access points may generate their channel estimates at different time instants for different frequency tones. Further, at time k, there may be a time error of τ _{k, u} between the access point and the u th access terminal. In such a case, the forward link channel vector estimate g _{i, k, u} measured at the access terminal is associated with the reverse link channel vector estimate h _{i, k, u} measured at the access point. May be. One approach that utilizes the calibration vector η and the access terminal mismatch γ _u is expressed in equation (8) below.

In Equation (8), Z _{i, k, u} is a diagonal matrix whose diagonal elements are elements of the reverse link channel vector estimate h _{i, k, u} ,

It is. The subscripts i, k, and u are the tone, time, and user indices, respectively. In the above equation, the unknown is the calibration vector η and the mismatch γ _{i, k, u} inherent to the access terminal. The feature of equation (8) is that the access terminal mismatch includes the effect of time mismatch between the access point and the access terminal, along with the gain mismatch due to the access terminal's transmit and receive chains. . One way to obtain solutions for η and γ _{i, k, u} utilizes a minimum mean square error (MMSE) approach, as shown in equation (9).

The solution of η and γ _{i, k, u} can be obtained by the following equation (10).

Here, the orthogonal projection operator is applied to the vector x.

Is

May be defined as follows.

  To compensate for mismatch, use the calibration ratio to change the gain of the access point's transmitter chain with respect to phase and / or amplitude to match it to the receiver chain, or the like In addition, the gain of the access point's receive chain may be changed to match it to the transmit chain.

In certain aspects, it may be desirable to calibrate the gain with respect to phase alone or with respect to both phase and amplitude. This is because, in certain cases, some calibration technique can exacerbate amplitude mismatch. This can be easily understood by considering the extreme case where there is only an amplitude mismatch without a phase mismatch in the gain mismatch. In this case, the gain of beamforming with calibration is worse than the gain of beamforming without calibration, which means here that the amplitude mismatch is worse. The improved method uses only phase calibration for beamforming instead of calibration using both amplitude and phase for the calculation of calibration weights. In this case, the calibrated weight beamforming is calculated for phase only. An aspect of this approach to MRC beamforming is expressed by the following equation ( 12 ):

For MRC

here,

  Although FIG. 2 shows and describes one embodiment of the receiver chain 102 and transmitter chain 104, other arrangements and structures may be used. For example, a different number of components may be used in both receiver chain 102 and transmitter chain 104. In addition, different devices and structures may be substituted.

  FIG. 3 illustrates a time cycle for calibration from one access terminal, where a TDD system having one forward link frame or burst adjacent to one reverse link frame or burst is utilized. As can be seen, one or more pilots transmitted on the reverse link are measured at the access point. The measurement period is a function of the decoding time of the access point. During this decoding period, one or more pilots are transmitted on the forward link to the access terminal. The access terminal then measures the pilot and estimates the forward link channel. As with the reverse link estimate, there is some decoding delay. The decoded forward link estimate must be sent back to the access point to generate a calibration ratio. Thus, it can be seen that there is a maximum amount of access terminal speed that can maintain calibration without some minimum amount of time, i.e., drift, which is a strong or substantial interfering factor.

  As can be seen from FIG. 3, if multiple channel estimates from multiple access terminals are utilized, the associated noise and drift may be reduced or at least sampled in the receive chain over a range of times. unknown.

  FIG. 4 illustrates aspects of logic that helps calibrate the antenna array to compensate for gain mismatch. The system 300 includes a calibration component 302 that utilizes a plurality of calibration techniques and a mismatch estimation component 304 that analyzes the model receiver chain output signal and / or compares the receiver chain output signal. For example, use vector η to generate calibration weights for different types of calibration, and then select one type of calibration based on the magnitude of the mismatch obtained using different types of calibration And a calibration calculation and determination unit 306. In certain aspects, this may be done using only phase estimates to calculate calibration weights, or using phase and amplitude estimates to calculate calibration weights.

  FIG. 5 illustrates an aspect of a system that helps calibrate the antenna array to compensate for gain mismatch. System 400 includes a processor 402 operably coupled to an antenna array 404. The processor 402 can determine calibration weights based on a plurality of calibration techniques. The processor 402 further comprises a calibration component 406, which selects one calibration type based on the magnitude of the mismatch obtained using different types of calibration.

  The system 400 can further comprise a memory 408 that is operatively coupled to the processor 402 and selects array calibration, ratio generation, different types of calibration techniques, different types of calibration techniques. Information about the reference to be performed, and any other suitable information about calibrating the antenna array 404. The processor 402 may be a processor dedicated to analyzing and / or generating information received by the processor 402, a processor controlling one or more components of the system 400, and / or information received by the processor 402. It should be understood that the processor may be parsed and generated to control one or more components of system 400.

  Memory 408 can further store protocols, mismatch estimates, etc. associated with generating signal copies and models / representations, such that system 400 can store stored protocols and / or algorithms. Can be used to achieve antenna calibration, technology selection, and / or mismatch compensation as described herein. It will be appreciated that the data storage (eg, memory) component described herein may be either volatile memory or nonvolatile memory, or may include both volatile and nonvolatile memory. By way of example, and not limitation, non-volatile memory may include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable ROM (EEPROM), or flash memory. it can. Volatile memory can include random access memory (RAM), which acts as external cache memory. By way of example, and not limitation, RAM can be synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), sync link DRAM (SLDRAM), Also, it can be used in many forms such as a direct Rambus RAM (DR RAM). The subject system and method memory 408 is intended to comprise, but is not limited to, these and any other suitable type of memory.

  Referring to FIG. 6, a method related to generating supplemental system resource assignments is shown. For example, the method may relate to antenna array calibration in a TDMA environment, an OFDM environment, an OFDMA environment, a CDMA environment, or some other suitable wireless environment. For clarity of explanation, these methods are shown and described as a series of operations, but according to one or more embodiments, some operations are in the order shown and described herein. It should be understood and appreciated that the method is not limited by the order of operations, as it may be performed in a different order and / or concurrently with other operations. For example, those skilled in the art will understand and appreciate that a method could alternatively be represented as a series of interrelated states or events, such as in a state transition diagram. Moreover, not all illustrated acts may be required to implement a methodology in accordance with one or more embodiments.

In certain aspects, the memory 408 includes a calibration vector for each state of AGC, ie, the amplification level.

Can be stored. In such an aspect, for each transmission, processor 402 may perform calibration vectors for AGC states without performing calibration.

You may access Perform further calibration or previous calibration vector for a given transmission

To determine whether to access the calibration vector for the AGC state

May be based on the duration or number of transmissions from when the is obtained. This may be a system parameter or may vary based on channel conditions, eg, channel loading.

  FIG. 6 illustrates a method for calibrating an antenna array for transmission. At block 500, a forward link channel estimate is received from an access terminal. As described above, these channel estimates may be generated from forward link pilots transmitted by the access point. In block 502, reverse link information, eg, channel estimates for the reverse link channel pilot, are generated by the access point.

  After both the forward link channel estimate and the reverse link channel estimate are collected, a calibration ratio for each access terminal antenna and access point antenna may be determined at block 504. In certain aspects, the forward link channel estimate and the reverse link channel estimate that are most recent in time are used to generate a calibration ratio. In such cases, multiple estimates for a given access terminal may be performed based on a pair of consecutive channel estimates consisting of forward link estimates and reverse link estimates.

  As described with reference to FIG. 3, some time delay may exist between various calculations and transmissions. Further, the functions of blocks 500 and 502 may be performed substantially simultaneously or at different times for the same or different access terminals. Thus, the calibration ratio may be determined for a given access terminal based on channel estimates of forward and reverse link transmissions that may or may not be continuous in time. Good.

  Next, at block 506, the calibration ratios are combined to produce a calibration estimate between the multiple access terminals. This combined calibration ratio may include calibration ratios for some or all of the access terminals in a given sector or cell, and is equal for each access terminal from which one or more calibration ratios are obtained. Or it may have an unequal number of calibration ratios.

  The combined calibration ratio can be obtained by simply averaging the calibration ratios, or other approaches described with reference to FIG. 2, such as the approach described with reference to equation (5) or (7). It can be obtained by using it.

  Next, each transmission from each transmission chain of the access point is weighted with a weight based on the combined calibration ratio for that transmission chain. Further, a combination or combination of calibration weights may be utilized for one or more transmission chains of the access point. Instead, this combined calibration ratio or a calibration instruction based on the combined calibration ratio may be sent to one or more access terminals. The access terminal then applies a weight based on the combined calibration ratio to decoding transmissions received at the access terminal.

  Further, in certain aspects, calibration weights are utilized for certain AGC states and not other AGC states. As such, block 508 applies only to the AGC state in block 500.

  FIG. 7 illustrates another method of calibrating an antenna array for transmission. At block 600, channel estimates for the forward link are received from the access terminal. As described above, these channel estimates may be generated from forward link pilots transmitted by the access point. Further, at block 602, reverse link information, eg, channel estimates for reverse link channel pilots, are generated by the access point.

  After both forward link channel estimates and reverse link channel estimates are collected, at block 604, the calibration ratio utilizes multiple channel estimates for multiple access terminals. In certain aspects, the forward link channel estimate and the reverse link channel estimate that are most recent in time are utilized. In such cases, multiple estimates for a given access terminal may be performed based on a pair of consecutive channel estimates consisting of forward link estimates and reverse link estimates.

  As described with reference to FIG. 3, some time delay may exist between various calculations and transmissions. Further, the functions of blocks 600 and 602 may be performed for the same or different access terminals substantially simultaneously or at different times. Thus, channel estimates are determined for a given access terminal based on channel estimates for forward and reverse link transmissions that may or may not be continuous in time. Also good.

  The joint calibration ratio can be obtained by utilizing a joint optimization process as described with reference to FIG. 2, for example, Equation (8).

  Next, each transmission from each transmission chain of the access point is weighted by a weight based on the joint calibration ratio for that transmission chain. Further, a combination or combination of calibration weights may be utilized for one or more transmission chains of the access point. Instead, this joint calibration ratio, or a calibration instruction based on the joint calibration ratio, may be sent to one or more access terminals. The access terminal then applies a weight based on the joint calibration ratio to decode the transmission received at the access terminal.

  Also, in some aspects, calibration weights are used for specific AGC states and not other AGC states. Then, as such, block 608 applies only to its AGC state in block 600.

  FIG. 8 shows an exemplary wireless communication system 1300. Wireless communication system 1300 depicts one base station and one terminal for sake of brevity. However, it is to be understood that the system may include more than one base station and / or more than one terminal, additional base stations and / or terminals being exemplary described below. The base station and terminal may be substantially similar or different. Further, the base stations and / or terminals can use the systems (FIGS. 1-5) and / or methods (FIGS. 6-7, or 10) described herein to facilitate wireless communication between them. It should be understood that it can be used.

Referring now to FIG. 8, in forward link transmission, at access point 1305, a transmit (TX) data processor 1310 receives, formats, encodes, interleaves, and modulates (or symbols) traffic data. Mapping), modulation symbols ("data symbols"). A symbol modulator 1315 receives and processes the data symbols and pilot symbols and provides a stream of symbols. A symbol modulator 1315 multiplexes data and pilot symbols on the appropriate subcarriers and provides a signal value of zero for unused subcarriers, for N transmit symbols for N subcarriers in each symbol period. Get a pair. Each transmission symbol may be a data symbol, a pilot symbol, or a signal value of zero. The pilot symbols may be transmitted continuously in each symbol period. It will be appreciated that the pilot symbols can be time division multiplexed (TDM), frequency division multiplexed (FDM), orthogonal frequency division multiplexed (OFDM), code division multiplexed (CDM), and so on. Symbol modulator 1315 may convert each set of N transmitted symbols to the time domain using N-point IFFT to obtain a “transformed” symbol that includes N time-domain chips. Symbol modulator 1315 typically repeats a portion of each transformed symbol to obtain a corresponding symbol. The repeated portion is known as a cyclic prefix and is used to deal with delay spread in the radio channel.

A transmitter unit (TMTR) 1320 receives the stream of symbols, converts it to one or more analog signals, and further adjusts the analog signals (eg, amplification, filtering, and frequency upconversion), A forward link signal suitable for transmission over a wireless channel is generated. The forward link signal is then transmitted to the terminal via antenna 1325. At terminal 1330, antenna 1335 receives the forward link signal and provides the received signal to a receiver unit (RCVR) 1340. Receiver unit 1340 adjusts the received signal (eg, filtering, amplification, and frequency down-conversion) and digitizes the adjusted signal to obtain samples. The symbol demodulator 1345 removes the cyclic prefix added to each symbol, converts each received and transformed symbol to the frequency domain using an N-point FFT, and outputs N for each symbol period. N received symbols for the number of subcarriers are obtained, and the received pilot symbols are provided to processor 1350 for channel estimation. Symbol demodulator 1345 further receives a frequency response estimate for the forward link from processor 1350, performs data demodulation on the received data symbols, and provides data symbol estimates (estimates of transmitted data symbols). ) And provide data symbol estimates to RX data processor 1355, which demodulates the data symbol estimates (eg, symbol demapping), deinterleaves, decodes, and transmits traffic Recover data. The processing by symbol demodulator 1345 and RX data processor 1355 is complementary to the processing by symbol modulator 1315 and TX data processor 1310 at access point 1305 , respectively.

On the reverse link, TX data processor 1360 processes traffic data and provides data symbols. A symbol modulator 1365 receives the data symbols, multiplexes with the pilot symbols, performs modulation, and provides a stream of symbols. The pilot symbols may be transmitted on subcarriers assigned to terminal 1330 to transmit pilots, and the number of reverse link pilot subcarriers is the same as the number of forward link pilot subcarriers. Or it may be different. Transmitter unit 1370 then receives and processes the stream of symbols to generate a reverse link signal, which is transmitted by antenna 1335 to access point 1305 .

At access point 1305 , the reverse link signal from terminal 1330 is received by antenna 1325 and processed by receiver unit 1375 to obtain a sample. A symbol demodulator 1380 then processes the samples and provides received pilot symbols and data symbol estimates for the reverse link. RX data processor 1385 processes the data symbol estimates and recovers traffic data transmitted by terminal 1330 . A processor 1390 performs channel estimation for active terminals transmitting on the reverse link.

  The processor 1390 may also use a plurality of calibration techniques to calculate calibration weights, as described with reference to FIGS. 2 and 10, and calculate the weights calculated according to one configuration technique. It may be configured to select.

Processors 1390 and 1350 direct the operation at access point 1305 and terminal 1330 , respectively (eg, control, coordination, management, etc.). Respective processors 1390 and 1350 may be associated with memory units (not shown) that store program codes and data. Processors 1390 and 1350 can also perform computations to obtain frequency and impulse response estimates for the reverse link and forward link, respectively.

Referring to FIG. 9, the access point 1400 may include a main unit (MU) 1450 and a radio unit (RU) 1475. MU 1450 includes the digital baseband component of access point 1400 . For example, the MU 1450 may include a baseband component 1405 and a digital intermediate frequency (IF) processing unit 1410. Digital IF processing unit 1410 digitally processes radio channel data at intermediate frequencies by performing functions such as filtering, channelization, modulation, and the like. RU 1475 includes the analog radio portion of access point 1400 . As used herein, a wireless unit is an analog wireless portion of an access point or other type of transceiver station that is directly or indirectly connected to a mobile switching center or corresponding device. A wireless unit typically serves as a particular sector in a communication system. For example, the RU 1475 may include one or more receivers 1430 connected to one or more antennas 1435a-1435t for receiving wireless communications from mobile subscriber units. In one aspect, one or more power amplifiers 1482a through 1482t are coupled to one or more antennas 1435a through 1435t. An analog / digital (A / D) converter 1425 is connected to the receiver 1430. The A / D converter 1425 converts the analog wireless communication received by the receiver 1430 into a digital input for transmission to the baseband component 1405 via the digital IF processing unit 1410. The RU 1475 may also include one or more transmitters 1420 that are connected to the same or different antennas 1435 for transmitting wireless communications to the access terminal. Connected to the transmitter 1420 is a digital to analog (D / A) converter 1415. The D / A converter 1415 converts the digital communication received from the baseband component 1405 via the digital IF processing unit 1410 into an analog output for transmission to the mobile subscriber unit. In an aspect, the multiplexer 1484 multiplexes a plurality of channel signals and various signals including voice signals and data signals. Central processor 1480 is coupled to main unit 1450 and RU 1475 to control various processes including the processing of audio or data signals.

  FIG. 10 illustrates an aspect of a method for determining the type of calibration to apply. At block 1500, determining the calibration weight for the approach is performed using the phase only mismatch information and at block 1502 using the phase and amplitude mismatch information. The phase only information may include phase only calibration vectors, channel estimates, etc. to calculate calibration weights. The phase and amplitude information may include calibration vector phase and amplitude information, channel estimates, etc. to calculate calibration weights. Calibration weights may be calculated based on information from multiple access terminals, as described with reference to FIGS. Alternatively, calibration weights may be calculated from information for one access terminal.

Next, in block 1504, a set of weights to be applied is selected. This determination may be made after utilizing calibration weights that can be calculated at the access point based on whether the amplitude mismatch is now worse than without calibration. In some embodiments, this may be based on the following equation (13):

In equation (13), σ _α represents the amplitude difference between the uncalibrated weight for the access point antenna transmit chain and the calibrated weight, and σ _β is calibrated for the access point antenna receive chain. It represents the amplitude difference between the missing weight and the calibrated weight. It may then be determined whether these amplitude differences exceed some threshold for their relationship. For example, coefficient maximum value has been calculated some predetermined, or system, for example, may be determined whether greater than just the minimum value 3. In another case, it may be determined whether one or both of σ _α and σ _β exceeds some predetermined threshold. In yet another case, various measurements, thresholds, or relationships of calibration mismatch may be utilized. Next, at block 1506, the selected weights are applied.

  For multiple access systems (eg, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, etc.), multiple The terminal may transmit simultaneously on the reverse link. For such a system, the pilot subcarrier can be shared between different terminals. Channel estimation techniques may be used when the pilot subcarriers for each terminal span the entire operating band (possibly excluding band edges). Such a pilot subcarrier structure is desirable to obtain frequency diversity for each terminal. The techniques described herein may be implemented by various means. For example, these techniques may be implemented in hardware, software, or a combination thereof. When implemented in hardware, the processing units used for channel estimation include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices ( PLD), field programmable gate array (FPGA), processor, controller, microcontroller, microprocessor, other electronic units designed to perform the functions described herein, or combinations thereof . In the case of software, it may be implemented by modules (eg, procedures, functions, etc.) that perform the functions described herein. Software code may be stored in a memory unit and executed by processors 1390 and 1350.

What has been described above includes examples of one or more embodiments. Of course, it is not possible to describe every possible combination of components or methods to describe the above-described embodiments, but those skilled in the art will be able to make many further combinations and substitutions of the various embodiments. You will see that there is. Accordingly, the described embodiments are intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the claims herein. Further, so long as the term “include” is used in the detailed description or claims, such terms are to be interpreted when “comprising” is used as a transition term in the claims. As such, it is intended to be included in the same manner as the term “comprising”.
The description corresponding to claim 1-27 at the time of filing of the present application is shown as appendix 1-27 below.

Appendix 1
A method for calibrating an antenna array, comprising:
Determining calibration weights for the antenna array based on a first calibration technique;
Determining calibration weights for the antenna array based on a second calibration technique that is a different calibration technique;
Determining whether to apply the calibration weight from one of the first calibration technique or the second calibration technique;
A method comprising:

Appendix 2
The method of claim 1, wherein the step of determining based on the first calibration technique comprises the step of determining based on phase-only information.

Appendix 3
The method of claim 2, wherein the step of determining based on the second calibration technique comprises the step of determining based on phase and amplitude information.

Appendix 4
The method according to appendix 2, wherein the phase-only information includes channel estimation information.

Appendix 5
The method of claim 2, wherein the phase only information comprises a component of a calibration vector that includes both phase and amplitude information.

Appendix 6
The method of claim 1, wherein the determining step comprises determining based on a ratio of the output provided by the first calibration technique to the output provided by the second calibration technique.

Appendix 7
The determining step determines a difference between an amplitude mismatch between an uncalibrated transmission and the output of the first calibration technique and an amplitude mismatch between an uncalibrated transmission and the output of the second calibration technique. The method according to claim 1, further comprising the step of:

Appendix 8
The determining step includes: a minimum amplitude mismatch between the uncalibrated transmission and the output of the first calibration technique and a minimum amplitude mismatch between the uncalibrated transmission and the output of the second calibration technique. And the difference in amplitude between the uncalibrated transmission and the output of the first calibration technique and the amplitude mismatch between the uncalibrated transmission and the output of the second calibration technique. The method according to claim 1, further comprising the step of determining a difference from a ratio of the difference from the maximum value.

Appendix 9
The method of claim 1, wherein the step of determining based on the first calibration technique and the step of determining based on the second calibration technique comprise a step of determining based only on information from one access terminal.

Appendix 10
The method of claim 1, wherein the step of determining based on the first calibration technique and the step of determining based on the second calibration technique comprise determining based on information from only a plurality of access terminals.

Appendix 11
The method of claim 1, wherein the step of determining based on the first calibration technique comprises the step of determining based on phase and amplitude information.

Appendix 12
At least two antennas;
A wireless communication device comprising: a processor coupled to the at least two antennas;
The processor is configured to determine a calibration type to apply from at least two calibration types to communicate with the two antennas;
Wireless communication device.

Appendix 13
The wireless communication device according to appendix 12, wherein one calibration type includes calibration based on phase-only information.

Appendix 14
The wireless communication device according to appendix 13, wherein the other calibration type includes calibration based on phase and amplitude information.

Appendix 15
13. The wireless communication of clause 12, wherein the processor is configured to determine the calibration type based on a ratio of an output provided by the first calibration technique to an output provided by a second calibration technique. apparatus.

Appendix 16
Based on the difference between the amplitude mismatch between the uncalibrated transmission and the output of the first calibration technique and the amplitude mismatch between the uncalibrated transmission and the output of the second calibration technique, the processor Item 13. The wireless communication device of appendix 12, configured to determine a calibration type.

Addendum 17
The processor determines the difference between the minimum amplitude mismatch between the uncalibrated transmission and the output of the first calibration technique and the minimum amplitude mismatch between the uncalibrated transmission and the output of the second calibration technique. The maximum amplitude mismatch between the uncalibrated transmission and the output of the first calibration technique and the maximum amplitude mismatch between the uncalibrated transmission and the output of the second calibration technique. The wireless communication device according to appendix 12, wherein the wireless communication device is configured to determine the calibration type based on a difference from a difference ratio.

Addendum 18
The wireless communications apparatus of appendix 12, wherein the processor is configured to determine the calibration type based on information from only one access terminal.

Addendum 19
The wireless communication apparatus according to appendix 12, wherein the processor is configured to determine the calibration type based on information from only a plurality of access terminals.

Appendix 20
An apparatus for calibrating an antenna array,
Means for determining calibration weights for the antenna array based on a first calibration technique;
Means for determining calibration weights for the antenna array based on a second calibration technique that is a different calibration technique;
Means for determining whether to apply the calibration weight from one of the first calibration technique or the second calibration technique;
A device comprising:

Appendix 21
The apparatus of claim 20, wherein the means for determining based on the first calibration technique comprises means for determining based on phase only information.

Appendix 22
The apparatus of claim 21, wherein the means for determining based on the second calibration technique comprises means for determining based on phase and amplitude information.

Appendix 23
The apparatus of claim 20, wherein the means for determining whether to apply comprises means for determining based on a ratio of an output provided by the first calibration technique to an output provided by the second calibration technique. .

Appendix 24
The means for determining whether to apply is an amplitude mismatch between an uncalibrated transmission and the output of the first calibration technique, and an amplitude mismatch between an uncalibrated transmission and the output of the second calibration technique. The apparatus of claim 20 comprising means for determining a difference from the alignment.

Appendix 25
The means for determining whether to apply the minimum amplitude mismatch between the uncalibrated transmission and the output of the first calibration technique and the uncalibrated transmission and the output of the second calibration technique. The ratio of the difference from the minimum amplitude mismatch, the maximum amplitude mismatch between the uncalibrated transmission and the output of the first calibration technique, the uncalibrated transmission and the output of the second calibration technique. 21. The apparatus according to appendix 20, comprising means for determining a difference from a ratio of a difference from a maximum value of amplitude mismatch with respect to.

Addendum 26
The apparatus of claim 20, wherein the means for determining based on the first calibration technique comprises means for determining based on phase and amplitude information.

Addendum 27
Processor readable instructions stored on a processor readable medium, determining calibration weights for the antenna array based on a first calibration technique;
Determining calibration weights for the antenna array based on a second calibration technique, which is a different calibration technique;
Determining whether to apply the calibration weight from one of the first technique or the second technique;
Processor readable instructions that cause the processor to execute.

Claims (14)

At least two antennas;
A wireless communication device comprising: a processor coupled to the at least two antennas;
A first calibration technique comprising calibration based on phase-only information, and first and second calibration weights applied to communicate with the at least two antennas; and phase and amplitude; Is configured to determine from at least two calibration techniques based on a second calibration technique comprising a calibration based on the information of: and (a) by utilizing the first calibration weight Communicate with the at least two antennas based on the provided output, (b) the output provided by utilizing the second calibration weight, or (c) both (a) and (b) To determine whether to apply calibration weights from one of the first calibration technique or the second calibration technique, the processor further comprises: Based on the ratio of the output provided by the first calibration technique to the output provided by the second calibration technique, the calibration weight is configured to determine the calibration array. A wireless communication device used for the purpose.   Based on the difference between the amplitude mismatch between the uncalibrated transmission and the output of the first calibration technique and the amplitude mismatch between the uncalibrated transmission and the output of the second calibration technique, the processor The wireless communications apparatus of claim 1, configured to determine a calibration technique. The processor is calibrated with a minimum value of an amplitude mismatch between the uncalibrated transmission and the output of the first calibration technique and an amplitude mismatch between the uncalibrated transmission and the output of the second calibration technique. not sending the amplitude mismatch between the output of the first calibration technique, based on the difference between the maximum value of the amplitude mismatch between transmission uncalibrated output of the second calibration technique The wireless communication device of claim 1, wherein the wireless communication device is configured to determine the calibration technique.   The wireless communications apparatus of claim 1, wherein the processor is configured to determine the calibration technique based on information from only one access terminal.   The wireless communication apparatus of claim 1, wherein the processor is configured to determine the calibration technique based on information from a plurality of access terminals. An apparatus for calibrating an antenna array,
Means for determining a first calibration weight for the antenna array based on a first calibration technique, wherein the means for determining based on the first calibration technique is based on phase-only information Means comprising:
Means for determining a second calibration weight for the antenna array based on a second calibration technique that is a different calibration technique, wherein the means for determining based on the second calibration technique comprises phase and amplitude information Means for determining based on:
(A) an output provided by utilizing the first calibration weight, (b) the second calibration weight, from one of the first calibration technique or the second calibration technique. Or (c) means for determining whether to apply to the antenna array based on both (a) and (b),
With
The means for determining whether to apply comprises means for determining based on a ratio of the output provided by the first calibration technique to the output provided by the second calibration technique, wherein the calibration weight comprises: A device used to calibrate an antenna array.   The means for determining whether to apply is an amplitude mismatch between an uncalibrated transmission and the output of the first calibration technique, and an amplitude mismatch between an uncalibrated transmission and the output of the second calibration technique. The apparatus of claim 6, comprising means for determining a difference from the alignment. The means for determining whether to apply is an amplitude mismatch between an uncalibrated transmission and the output of the first calibration technique, and an amplitude mismatch between an uncalibrated transmission and the output of the second calibration technique. A minimum of matching , an amplitude mismatch between an uncalibrated transmission and the output of the first calibration technique, and a maximum of an amplitude mismatch between an uncalibrated transmission and the output of the second calibration technique The apparatus of claim 6, comprising means for determining a difference between the values .   The apparatus of claim 6, wherein the means for determining based on the first calibration technique comprises means for determining based on phase and amplitude information. Determining a first calibration weight for the antenna array based on a first calibration technique comprising calibration based on phase-only information;
Determining a second calibration weight for the antenna array based on a different calibration technique, a second calibration technique with a configuration based on phase and amplitude information;
(A) an output provided by utilizing the first calibration weight, (b) the second calibration weight, from one of the first calibration technique or the second calibration technique. Or (c) determining whether to apply to the antenna array based on both (a) and (b), wherein the calibration weight is the antenna A procedure used to calibrate the array;
Determining a calibration technique based on a ratio of an output provided by the first calibration technique to an output provided by the second calibration technique;
A program that causes a computer to execute.   The calibration technique is determined based on the difference between the amplitude mismatch between the uncalibrated transmission and the output of the first calibration technique and the amplitude mismatch between the uncalibrated transmission and the output of the second calibration technique. The program according to claim 10, further comprising: The amplitude mismatch between the uncalibrated transmission and the output of the first calibration technique, the minimum of the amplitude mismatch between the uncalibrated transmission and the output of the second calibration technique, and the uncalibrated transmission; wherein the amplitude mismatch between the output of the first calibration technique, based on the difference between the maximum value of the amplitude mismatch between transmission uncalibrated output of the second calibration technique, the calibration technique The program according to claim 10, further comprising a procedure for determining.   The program according to claim 10, further comprising determining the calibration technique based on information from only one access terminal.   The program according to claim 10, further comprising a step of determining the calibration technique based on information from a plurality of access terminals.

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