RU2386223C2 - Calibration of antenna array for systems of wireless communication - Google Patents

Abstract

FIELD: information technologies.

SUBSTANCE: calibration is realised for transmission channel of device that transmits information to multiple devices along lines of wireless communication, and channels of reception of multiple devices that receive information along one of wireless communication lines, using multiple estimates of direct communication line channel, received from at least some of multiple devices, and multiple estimates of reverse communication line channel from multiple devices.

EFFECT: provision of antenna array calibration used in wireless communication devices.

27 cl, 10 dwg

Description

This application claims the priority of provisional patent application US No. 60/674190, entitled "ANTENNA ARRAY CALIBRATION FOR WIRELESS COMMUNICATION SYSTEM", filed April 22, 2005, provisional patent application US No. 60/691458, entitled "A METHOD FOR OVER THE AIR CALIBRATION OF TDD MULTI ANTENNA SYSTEMS "filed June 16, 2005 and provisional patent application US No. 60/733020, entitled" ANTENNA ARRAY CALIBRATION FOR WIRELESS COMMUNICATION SYSTEMS "filed November 2, 2005, which are incorporated herein by reference throughout its fullness.

BACKGROUND

I. Technical Field

The following description relates mainly to wireless communications and, among other things, to radio antenna calibration.

II. State of the art

Wireless networking systems have become the dominant means by which most people around the world communicate. Wireless devices have become smaller and more powerful to meet consumer needs and improve portability and convenience. The increase in computing power in mobile devices, such as cell phones, has increased the demands on wireless transmission systems. Such systems are usually not as easily upgraded as cellular devices that communicate in these systems. As the capabilities of mobile devices expand, it can be difficult to support an older wireless network system in a way that encourages full use of the new and improved capabilities of wireless devices.

More specifically, methods based on frequency division of channels usually divide the spectrum into separate channels, dividing it into even sections of the frequency band; for example, a dedicated frequency band assigned for wireless communication using cell phones can be divided into channels, each of which can transmit voice conversation or, using a digital service, transmit digital data. Each channel can be assigned to only one user at a time. One commonly used option is the orthogonal frequency division multiplexing method, which effectively partitions the frequency band of the entire system into multiple orthogonal subcarriers. These subcarriers are also referred to as tones, carriers, bins (resolution elements) and / or frequency channels. With methods based on time division of channels, the band is divided in time into consecutive time intervals or channel intervals. Each channel user can be provided with a time interval for transmitting and receiving information in a circular queue. For example, at any given time t, the user is granted access to the channel for a short send. Then, access is switched to another user who is provided with a short temporary package for transmitting and receiving information. The cycle "in turn" continues, and, in the end, each user is provided with many sending and receiving packages.

Code division multiplexing techniques usually transmit data at several frequencies available at any given time in a range. In general terms, data is digitized and expanded over an available frequency band, with many users sharing a channel and a unique sequence code can be assigned to corresponding users. Users can transmit in the same broadband section of the spectrum, and the signal of each user is expanded over the entire frequency band using the corresponding unique extension code. This method may involve sharing, in which one or more users can simultaneously transmit and receive. Such sharing can be achieved by spread spectrum digital modulation, in which the user bitstream is encoded and expanded in a very wide channel in a pseudo-random manner. The receiver is configured to recognize the associated unique sequence code and eliminate randomization in order to receive bits for a particular user in a consistent manner.

A typical wireless communication network (e.g., using frequency, time and code division multiplexing techniques) includes one or more base stations that provide coverage, and one or more mobile (e.g., wireless) terminals that can transmit and receive data within the coverage area. A typical base station can simultaneously transmit multiple data streams for broadcast, multicast (multicast) and / or unicast services, the data stream being a data stream that can be independently designed to be received by a mobile terminal. A mobile terminal within the coverage area of this base station may be interested in receiving one, more than one or all of the data streams carried by the composite stream. Similarly, a mobile terminal may transmit data to a base station or another mobile terminal. Such communication between the base station and the mobile terminal or between the mobile terminals may be degraded due to changes in the channel and / or changes in the interference power. For example, the above changes may affect base station scheduling, power control, and / or transmission rate prediction for one or more mobile terminals.

When antenna arrays and / or base stations are used in conjunction with the time domain duplex transmission method (TDD), a very large gain can be realized. The key assumption in realizing this gain is that due to the nature of transmission and reception in TDD mode, both the forward link (PLC) and the reverse link (OLS) perceive physical channels with similar propagation characteristics corresponding to the total carrier frequency. However, in practice, common transmission and reception channels, which may include analog input stages and digitally sampled transmitters and receivers, as well as the architecture of the physical cable system and antennas, contribute to the overall channel response received by the receiver. In other words, the receiver will perceive a common or equivalent channel between the input of the digital-to-analog converter (DAC) of the transmitter and the output of the analog-to-digital converter (ADC) of the receiver, which may contain the analog channel of the transmitter, the physical propagation channel, the physical structure of the antenna array (including the cable system ) and the analog channel of the receiver.

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

SUMMARY OF THE INVENTION

A simplified summary of one or more embodiments is set forth in order to provide a basic understanding of such embodiments. This summary is not an extensive overview of all considered embodiments, and is not intended to identify key or critical elements of all embodiments, nor to schematically represent the scope of any or all embodiments. Its sole purpose is to present some principles of one or more embodiments in a simplified form 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 comprises receiving estimates for the first communication lines to establish communication with the at least two terminals from the terminals and determining estimates of the second communication lines from the at least two terminals. Then, the calibration relation is determined based on the estimates of the first and second communication lines.

According to another aspect, a wireless communication device comprises at least two antennas and a processor coupled to at least two antennas. The processor is configured to determine a calibration relationship based on a plurality of forward link channel estimates and reverse link channel estimates from a plurality of access terminals.

According to yet another aspect, an apparatus may comprise means for receiving first channel estimation information corresponding to transmissions of at least two access terminals, means for determining second channel estimation information corresponding to transmissions of at least two access terminals, and means to determine the calibration relationship based on the first and second channel estimation information.

Another aspect relates to a processor readable medium having instructions stored thereon for use by the processor. The instructions include instructions for determining a plurality of reverse link channel estimates for a plurality of access terminals and determining a calibration relationship based on a plurality of forward link channel estimates received from at least some of the plurality of access terminals and a plurality of reverse link channel estimates communication from multiple access terminals.

In further aspects, a method is provided that determines a transmission interval for the last calibration for a particular state of automatic gain control (AGC). A determination is then made, based on the transmission interval after the last calibration, whether to perform another calibration for the AGC state or to read the vector of the previous calibration or weights from the memory for the AGC state in order to calibrate the current transmission for the AGC state.

In another aspect, a wireless communication device includes a processor configured to determine, based on a transmission interval after a last calibration, whether to perform another calibration for the AGC state or to read a previous calibration vector or memory weights for the AGC state to calibrate the current transmission for AGC states. The processor is connected to the memory.

In yet another aspect, the wireless communications apparatus includes means for determining, based on a transmission interval after the last calibration, whether to perform another calibration for the AGC state or to read a vector of the previous calibration or memory weights for the AGC state in order to calibrate the current transmission for the AGC state . The wireless communication device may also include means for reading the weights, or calibration vector, from a memory for calibrating the current transmission if the transmission interval is less than some criteria, and means for performing another calibration operation to be used for the current transmission if the interval transmission exceeds the criteria.

To the accomplishment of the foregoing and related ends, one or more embodiments comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of one or more embodiments. These aspects, however, indicate only a few ways in which the principles of the various embodiments can be used, and it is intended that the described embodiments include all such aspects and their equivalents.

Brief Description of the Drawings

Figure 1 illustrates aspects of a wireless multiple-access communication system.

2 illustrates an antenna device comprising a receiver channel and a transmitter channel according to various aspects described herein.

Figure 3 illustrates aspects of time matching for calibration operations.

4 illustrates aspects of a logic that facilitates calibration of an antenna array to compensate for gain mismatch.

5 illustrates aspects of a system that facilitates calibrating an antenna array to compensate for gain mismatch.

6 illustrates aspects of a method for calibrating an antenna array.

7 illustrates aspects of a method for calibrating an antenna array.

8 illustrates aspects of a receiver and a transmitter in a wireless communication system.

9 illustrates aspects of an access node.

10 illustrates aspects of a method for calibrating an antenna array.

Detailed description

Various embodiments are described below with reference to the drawings, in which like reference numerals are used to refer to like elements throughout the drawings. 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. It may be obvious, however, that such an embodiment (s) of implementation can be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more embodiments.

As used in this application, the terms “component”, “system” and the like are intended to refer to computer related objects made on the basis of hardware, a combination of hardware and software, or software or software in execution. For example, a component may be, but is not limited to, a process running on a processor, a processor, an object, an executable file, a control flow, a program, and / or a computer. One or more components may be in the process and / or control flow, and the component may be localized on one computer and / or distributed across two or more computers. Also, these components can be executed from various computer-readable media having various data structures stored thereon. Components can be transmitted using local and / or remote processes, for example, in accordance with a signal having one or more data packets (for example, data from one component interacts with another component in a local system, distributed system and / or over a network, such as Internet, with other systems via signal).

In addition, various embodiments are described herein in connection with a subscriber station. A subscriber station may also be called a system, subscriber unit, mobile station, mobile device, remote station, access node, base station, remote terminal, access terminal, user terminal, user agent, user equipment, etc. The subscriber station may be a cellular telephone, a cordless telephone, a SIP protocol telephone, a wireless subscriber line station (WLL), a personal digital assistant (PDA), a portable device having wireless connectivity, or another processing device connected to wireless modem.

In addition, various aspects or features described herein may be implemented as a method, device, or product using standard programming and / or design methods. The term “product,” as used herein, is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. For example, computer-readable media may include, but are not limited to, magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips ...), optical disks (e.g., compact disc (CD), digital multifunction disk ( DVD) ...), smart cards, flash memory devices (for example, in the form of cards, sticks, storage keys ...), integrated circuits such as read-only memory, programmable read-only memory and electrically erasable programmable read-only memorizing guides device.

1 illustrates a multiple access wireless communication system according to one embodiment. A multiple access wireless communication system 1 includes a plurality of cells, for example, cells 2, 104 and 106. In FIG. 1, each cell 2, 4 and 6 may include an access node that includes multiple sectors. Many sectors are formed by groups of antennas, each of which is responsible for communication with access terminals in the cell part. In cell 2, each group of 12, 14, and 16 antennas corresponds to a different sector. In cell 4, each group of antennas 18, 20 and 22 corresponds to a different sector. In cell 6, each group of antennas 24, 26 and 28 corresponds to a different sector.

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

A controller 50 is associated with each cell 2, 4, and 6. The controller 50 may comprise one or more connections to multiple networks, such as the Internet, other packet based, or circuit switched voice networks that provide information to and from access terminals in communication with cells of a multiple access wireless communication system 1. The controller 50 comprises or is connected to a scheduler that schedules transmission from and to access terminals. In other embodiments, the scheduler may reside in each individual cell, each sector of a cell, or a combination thereof.

To facilitate the calibration of transmissions to access terminals, it is useful to calibrate the gain calibration loop of the access node to solve the mismatch problem due to transmission and reception channels of the access node. However, due to noise in the channel, any calibration estimate based on the signals received at the access terminals (forward link) and transmitted from the access terminals (reverse link) may contain noise and other changes in the channels that may cast doubt on the estimates presented. used to provide calibration. To compensate for the effect of noise in the channel, a plurality of calibrations of both the forward link and reverse link are used for multiple access terminals. In some aspects, multiple transmissions to and from each access terminal are taken into account to calibrate a given sector.

In some aspects, either the transmission channel of the access node or the reception channel of the access node may be calibrated. This can be accomplished, for example, by using a calibration relationship to calibrate the receive channel of the access node to its transmit channel or calibrate its transmit channel to its receive channel. The calibration relationship can then be used to calibrate the transmission channel of the access node or the reception channel of the access node.

As used herein, the access node may be a fixed station used to communicate with the terminals, and may also be mentioned and include some or all of the functionality of the base station of node B or defined by some other terms. An access terminal may also be referred to and include some or all of the functionality of a user equipment (UE), wireless device, terminal, mobile station, or defined by some other terms.

It should be noted that, although FIG. 1 describes physical sectors, i.e. having different antenna groups for different sectors, other approaches may be used. For example, the use of multiple fixed "beams", each of which covers different areas of the cell in the frequency space, can be used instead of or in combination with physical sectors. Such an approach is described and disclosed in US Patent Application Serial No. 11/260895, entitled "Adaptive Sectorization In Cellular System", which is incorporated herein by reference.

2, an antenna device 100 is shown comprising a receiver channel 102 and a transmitter channel 104 in accordance with various aspects described herein. The receiver channel 102 comprises a down-converter component 106, which down-converts the signal into a baseband frequency upon reception. The down-converter component 106 is connected to an automatic gain control (AGC) unit 108, which determines the intensity of the received signal and automatically adjusts the gain applied to the received signal to maintain the receiver channel 102 within its associated linear mode range and to maintain a constant signal intensity for output through channel 104 of the transmitter. It will be appreciated that AGC 108 may not be necessary for some of the embodiments described herein (for example, automatic gain control need not be performed in each embodiment). The AGC 108 is connected to an analog-to-digital (A / D) converter 110, which converts the received signal to digital format before the signal is smoothed by a digital low-pass filter (LPF) 112, which can attenuate short-term fluctuations in the received signal. Finally, receiver channel 102 may include a receiver processor 114 that processes the received signal and may transmit the signal to one or more components of the transmitter channel 104.

Transmitter channel 104 may include a transmitter processor 116 that receives a signal from receiver channel 102 (for example, a transmitter receives a signal that was originally received by receiver channel 102 and underwent various processes associated with its components, ...). The processor 116 of the transmitter is coupled to a pulse shaper 118 that manipulates the signal to be transmitted, so that the signal can be shaped to fit within the limits of the frequency band while weakening and / or eliminating intersymbol interference. If the signal is shaped, it can undergo digital-to-analog (D / A) conversion in the D / A converter 120 before it is exposed to the associated low-pass filter (LPF) in the channel 104 of the smoothing transmitter. Component 124 of a pulse amplifier (DUT) can amplify the pulse / signal before converting with increasing frequency into the band of modulating frequencies through the Converter 126 with increasing frequency.

An antenna array 100 may exist for each antenna of both the access node and the access terminal. Essentially, there may be a noticeable difference observed between the transfer response of the transmitter channel 104 and the receiver channel 102 and / or their samples, and the mutuality of the equivalent channel and / or transmitter / receiver cannot be assumed. When calibrating the antenna array 100, an understanding of the magnitude of the changes based on the effect on the phase and / or amplitude of the signals propagating through the channels of the transmitter and receiver and their influence on the accuracy of the reciprocity assumption can be used to facilitate the calibration process. In addition, in the case of an antenna array, basically, each antenna 100 has a different transmitter channel 104 and a receiver channel 102 different from the channels of each other antenna. Therefore, each other transmitter channel 104 may have different effects, based on phase and / or amplitude, like any other transmitter channel 104, respectively. The same may be true for receiver channels 102 of each antenna 100.

The mismatch in the effect may be due to the physical design of the antenna 100, differences in components, or a number of other factors. Such mismatches may include, for example, mutual coupling effects, tower effects, imperfect positional information, amplitude and / or phase mismatches due to the antenna cable system, and the like. In addition, the mismatch may be due to hardware elements in the transmitter channel 104 and / or the receiver channel 102 of each antenna 100. For example, such mismatches may be associated with analog filters, imbalance of the I and Q signals, phase mismatch and / or amplification of the low noise amplifier or amplifier in channels, various non-linear effects, etc.

For an access node, calibrating each transmission channel over its corresponding receive channel (i.e., the receive channel corresponding to the same antenna) will independently require a complex and potentially cumbersome process. Further, any particular feedback for forward link transmission or pilot signals used for reverse link transmission for any given access terminal is subject to noise for this user. Therefore, for any given calibration relationship, estimated on the basis of both the forward and reverse links, there is some error introduced by the change and noise in the channel. Therefore, in several aspects, one or more calibration relationships evaluated for several different access terminals are summed to obtain a single calibration relationship to be used by the access point for transmission to one or all access terminals. In some aspects, the summation may average all, or some predefined subset, of the calibration relationships for each access terminal that establishes communication with the access node. In another aspect, the summation can be performed by the joint optimization method, where channel measurements from and for each access terminal are summed to estimate a single calibration relationship, which is a combination of gain mismatches for each access terminal, without calculating an individual calibration relationship for each access terminal.

For any given access terminal, the access node uses the relative reverse link channel estimates and the forward link channel estimates that are performed on the access terminal and fed back to the access node to evaluate or calculate a calibration relationship based on this access terminal.

канала прямой линии связи может оцениваться на терминале доступа для передач с i-ой передающей антенны узла доступа. Однако любая оценка канала будет иметь компоненты, относящиеся к шуму канала, вместе с любым усилением или искажением, вызванным каналом передачи узлов доступа и каналом приема терминалов доступа. Оценка канала прямой линии связи тогда может быть записана как:Rating

the forward link channel may be evaluated at the access terminal for transmissions from the i-th transmit antenna of the access node. However, any channel estimate will have channel noise related components, together with any gain or distortion caused by the transmission channel of the access nodes and the reception channel of the access terminals. The forward link channel estimate can then be written as:

усиления канала передатчика узла доступа, h_i, который представляет собой физический канал между двумя измеряемыми антеннами, и шума n_i канала, который представляет собой часть оценки канала.In equation (1), the channel estimate is a mismatch function β _AT channel gain of the access terminal receiver, the mismatch

the gain of the transmitter channel of the access node, h _i , which is the physical channel between the two measured antennas, and the channel noise n _i , which is part of the channel estimate.

, по существу, представляет собой инверсию уравнения (1). Это можно видеть в уравнении (2) ниже:In the case of transmissions on the reverse link, channel estimation at the i-th receiving antenna of the access node due to transmission from the AP

essentially represents an inverse of equation (1). This can be seen in equation (2) below:

усиления канала приемника узла доступа, h_i, который представляет собой физический канал между двумя измеряемыми антеннами, и шума υ_i канала, который представляет собой часть оценки канала.In equation (2), this channel estimate is a mismatch function α _{AT of a} gain of a transmission channel of an access terminal, a mismatch

the gain of the receiver channel of the access node, h _i , which is the physical channel between the two measured antennas, and the noise υ _{i of the} channel, which is part of the channel estimate.

To calibrate the antenna array, the mismatch errors between the receiver channels 102 and the transmitter channels 104 of the antennas 100 therein are shown below in equation (3). It should be noted that other methodologies and mathematical dependencies can be used to implement lattice calibration jointly or instead of the methods and mathematical dependencies described in this document.

In equation (3), c _i represents the general mismatch relationship between reverse link transmissions and forward link transmissions, γ represents the gain mismatch between the transmit and receive channels of the access terminal, and η _i represents the mismatch ratio of the receive and transmit channels for the i-th antenna in the access node. It should be noted that γ is essentially constant for each pair of antennas in the access node. Also, in some respects, equation (3) is idealized, since the noise estimate is not included in it.

для каждого терминала доступа, который может быть назван «вектором калибровки».The calibration relations c _i , i = 1, ... M, where M represents the number of antennas in the antenna array of the access node, can be grouped into one vector

for each access terminal, which may be called a “calibration vector”.

соответствуют оценкам для каждой антенны узла доступа в отношении единственного терминала доступа. Необходимо отметить, что элементы вектора

могут быть комплексными числами, включающими в себя как амплитудное, так и фазовое рассогласование для каждого канала передачи и приема антенной решетки узла доступа, а также общее рассогласование, соответствующее рассогласованию передачи и приема каналов передачи и приема терминала доступа.In equation (4), the elements of the vector

correspond to the estimates for each antenna of the access node with respect to a single access terminal. It should be noted that the elements of the vector

can be complex numbers, including both amplitude and phase mismatch for each channel of transmission and reception of the antenna array of the access node, as well as the total mismatch corresponding to the mismatch of the transmission and reception of transmission and reception channels of the access terminal.

The noise vector n includes the influence of channel measurement errors (standard error (RMS)) and also the effect of decorrelation of the channel measurement, since gain measurements are performed at different points in time, thus allowing changes in the channel over time, as well as temperature and other changes influence on the measurement.

калибровки, соответствующий терминалу u доступа, может определяться так, как показано ниже в уравнении (5).Rated vector

the calibration corresponding to the access terminal u can be determined as shown below in equation (5).

определяется для всех антенн антенной решетки узла доступа.where γ _u is the gain mismatch corresponding to the transmission and reception channels of the access terminal, and η is the mismatch vector corresponding to the transmission and reception channels of the antenna array of the access node. Vector

determined for all antennas of the antenna array of the access node.

In the above, it should be noted that there are several ways to summarize different calibration estimates (corresponding to measurements from different access terminals) to generate common or summarized calibration estimates. One way to do this summation is to average all calibration estimates to get one estimate.

In this approach, each calibration vector estimate includes a multiplier γ _u , which is different for different access terminals. In the case where one or more access terminals have a very large gain mismatch γ _u , simple averaging can lead to results that bias the average towards the access terminals having the largest gain mismatch y _u .

In another aspect, each calibration vector estimate corresponding to a particular access terminal is normalized in accordance with the vector element. This can provide minimization in cases where one or more access terminals have a large gain mismatch γ _u . This process is depicted in equation (6) below.

.It should be noted that in some aspects, the normalizing element can be any element of the calibration vector, provided that it is the same element for each estimate of the calibration vector, for example, the first element or another element. The sum of the normalized elements is then divided by the total number of elements U of the vector

.

Another approach that can be used to summarize various estimates of the calibration vector can be based on the summation of the estimated vectors in the matrix. For example, in some aspects, each calibration vector estimate may be a rotated and scaled version of the same vector η, the rotation and scaling being due to different mismatches γ _{u of} the access terminal. One way to get rid of this scaling and rotation is to first normalize each calibration vector so that it has a unit norm. Then the matrix Q, the columns of which are normalized estimates of the calibration vector, can be formed from the calibration vectors. The only estimate for the calibration vector is obtained by expanding the matrix, for example, expanding into singular numbers of the matrix Q. The eigenvector corresponding to the maximum singular number can be used as a general estimate of the calibration vector, for example, as shown in equation (7) below.

As shown as an example in the three approaches above, the calibration ratio is mainly evaluated in two steps. First, the values corresponding to the elements of the calibration vectors are calculated for the antenna array, or these antennas of interest, with respect to the individual access terminals. Calibration vectors are then summed according to one or more different mathematical processes.

An alternative to calculating multiple calibration vectors is to use a joint optimization procedure using multiple measurements of access nodes and access terminals as follows. In some cases, the access terminal and the access node may generate their channel estimates for different frequency tones and at different points in time. In addition, there may be a temporary error τ _{k, u} between the access node and the u-th access terminal at time k. In this case, the estimate g _{i, k, u} of the forward link channel vector measured at the access terminal may be related to the estimate h _{i, k, u} of the reverse link channel vector measured at the access node. One approach using the calibration vector η and the mismatch γ _{u of} the access terminal is depicted in equation (8) below.

. Нижние индексы i,k,u представляют собой индексы тона, времени и пользователя, соответственно. В вышеупомянутом уравнении неизвестными являются вектор η калибровки и конкретное рассогласование γ_i,k,u терминала доступа. Особенность уравнения (8) заключается в том, что рассогласование терминала доступа включает в себя эффект временного рассогласования между узлом доступа и терминалом доступа в дополнение к рассогласованию усиления из-за каналов передачи и приема терминала доступа. Одним путем получения решения для η и γ_i,k,u является использование подхода минимальной среднеквадратической ошибки (МСКО), как показано в уравнении (9).In equation (8), Z _{i, k, u} is a diagonal matrix, the diagonal elements of which are elements of the estimate h _{i, k, u} of the reverse link channel vector and

. The subscripts i, k, u are the indices of tone, time, and user, respectively. In the above equation, the calibration vector η and the specific mismatch γ _{i, k, u of} the access terminal are unknown. A feature of equation (8) is that the mismatch of the access terminal includes the effect of a temporary mismatch between the access node and the access terminal in addition to the gain mismatch due to the transmission and reception channels of the access terminal. One way to obtain a solution for η and γ _{i, k, u} is to use the minimum mean square error (ISCED) approach, as shown in equation (9).

Solutions for η and γ _{i, k, u} can be given by equation (10) below.

может быть определен какwhere for the vector x the orthogonal projective operator

can be defined as

To compensate for mismatches, calibration relationships can be used to change the gain, based on both, or one of two, the phase and amplitude of the transmitter channel of the access node to match it with its receiver channel, or, equivalently, to change the gain of the reception channel of the access node to match it with its transmission channel.

In some aspects, the access node may use beamforming by summing differentially weighted signals (SDCS, MRC), beamforming by linear summing of equal power signals (CCPM, EGC), or any other spatial preprocessing technique for transmission to any access terminal. Those. if the reverse link channel vector is h, the access node uses the following preprocessing weights for transmission:

With an estimate η of the calibration vector, the access node can use the following pre-processing weighting coefficients to compensate for its mismatch between the transmission and reception channels:

where diag (η _ϕ ) = diag (□ η).

Although FIG. 2 depicts and describes one embodiment of a receiver channel 102 and a transmitter channel 104, other arrangements and designs may be used. For example, a different number of components can be used in both the receiver channel 102 and the transmitter channel 104. In addition, other devices and structures may also be replaced.

FIG. 3 illustrates a time alignment cycle for calibration from a single access terminal using an ADT system having one frame or forward link next to one frame or reverse link. As you can see, one or more pilot signals transmitted on the reverse link is measured (measured) at the access node. The measurement time period is a function of the decoding time of the access node. During this decoding period, one or more pilot signals are transmitted on the forward link to the access terminal. The access terminal then measures the pilot signals in order to estimate the forward link channel. As with reverse link estimates, there is some decoding lag. The decoded forward link estimates must be transmitted back to the access node in order to generate a calibration relation. Therefore, it can be seen that there is a certain minimum amount of time, and therefore the maximum speed of the access terminal, for which calibration can be maintained without drift, is a strong or essentially interfering factor.

As can be seen in FIG. 3, if multiple channel estimates are used from multiple access terminals, the associated noise and drift can be reduced, or at least can be selected over a range of time points and reception channels, thereby adopting an overall calibration gain.

, и объединяет их для использования, используя один из способов, описанных выше для суммирования различных измерений от различных терминалов доступа.4 illustrates aspects of a logic that facilitates calibrating an antenna array to compensate for gain mismatch. The system 300 includes a calibration component 302, which includes a mismatch estimation component 304 that analyzes the output from the receiver channel of the models and / or the comparison between the output signals from the receiver channel, and a relationship combining calculator 306 that calculates the relationships that are used to generate the vector

, and combines them for use, using one of the methods described above to summarize different measurements from different access terminals.

.5 illustrates aspects of a system that facilitates calibrating an antenna array to compensate for gain mismatch. System 400 includes a processor 402 that is coupled to an antenna array 404. Processor 402 can determine gain mismatches for individual antenna combinations at the access terminal and access node using calibration component 406. The processor 402 further comprises a calibration component 406 that determines a calibration relationship and then generates and uses a vector

.

System 400 may further comprise a memory 408 that is coupled to processor 402 and which stores information related to calibrating the array, generating and using a relationship, generating calibration data, etc., and any other suitable information related to calibrating the antenna array 404. It is understood that processor 402 may be a processor dedicated to analyzing and / or generating information received by processor 402, a processor that controls one or more components of the system 400, and / or a processor that both analyzes and generates information received by the processor 402, and controls one or more components of the system 400.

Memory 408 may further store protocols associated with generating copies of the signal and models / representations, mismatch estimates, etc., so that system 400 can use stored protocols and / or algorithms to perform antenna calibration and / or mismatch compensation, as described in this document. It is understood that the storage components (eg, memory) of the data described herein can be either volatile memory or non-volatile memory, or they can include both volatile and non-volatile memory. By way of illustration, but not limitation, non-volatile memory may include read-only memory (ROM), programmable ROM (EPROM), electrically programmable ROM (EEPROM), electrically erasable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM), which acts as an external cache. As an illustration, but not limitation, RAM is available in many forms, such as synchronous RAM (RAM), dynamic RAM (DOS), synchronous DOSE (DLC), DLC with a doubled data rate (DLC USOD), advanced DOS (USAGE) , DOS with synchronous communication (DOS SS) and RAM with direct resident access bus (BBA RAM). The memory 408 of the systems and methods in question is believed to comprise, without being limited to, these and any other suitable types of memory.

калибровки для каждого состояния, т.е. уровня усиления, АРУ. В таких аспектах, для каждой передачи процессор 402 может обращаться к вектору

калибровки для состояния АРУ без выполнения калибровки. Решение в отношение того, выполнять ли дополнительную калибровку или обращение к предыдущему вектору

калибровки для данной передачи, может основываться на периоде времени или количестве передач, с момента получения вектора

калибровки для состояния АРУ. Это может быть системный параметр, или он может изменяться, основываясь на условиях канала, например, загрузки канала.In some aspects, memory 408 may store vectors

calibrations for each state, i.e. gain level, AGC. In such aspects, for each transmission, processor 402 may refer to a vector

calibrations for AGC state without performing calibration. Decision as to whether to perform additional calibration or referring to the previous vector

calibration for a given transmission can be based on the period of time or the number of transfers since the receipt of the vector

calibration for the state of AGC. This may be a system parameter, or it may vary based on channel conditions, such as channel loading.

6 illustrates a method for calibrating an antenna array for transmission. Channel estimates for the forward link are received from access terminals (block 500). As described above, these channel estimates may be generated from forward link pilots transmitted by the access node. In addition, channel estimates for reverse link information, for example, reverse link channel pilot signals, are generated by the access node (block 502).

After the channel estimates of both the forward link and the reverse link are collected, calibration relationships for each antenna of the access terminal and access node can be determined (block 504). In some aspects, the most recent estimate of the forward link channel and the reverse link in relation to each other over time is used to form a calibration relationship. In such cases, a plurality of estimates for a given access terminal may be performed based on successive pairs of channel estimates of the forward link and reverse link estimates.

As described with respect to FIG. 3, there may be some time lag between different calculations and transfers. Further, the functionality of blocks 500 and 502 can take place substantially simultaneously or at different points in time for the same or different access terminals. Therefore, a calibration relation can be determined for a given access terminal based on estimates of the forward link and reverse link transmission channel, which may or may not be sequential in time.

The calibration relationships are then summed to form a calibration estimate for the plurality of access terminals (block 506). This summarized calibration relationship may include calibration relationships for some or all of the access terminals in a given sector or cell, and may have an unequal or equal number of calibration relationships for each access terminal for which one or more calibration relationships are obtained.

The summed calibration relationship can be obtained by simply averaging the calibration relationships or using other approaches discussed in relation to FIG. 2, for example, approaches discussed in relation to equations (5) or (7).

Each transmission from each transmission channel of the access node is then weighted with weights based on the summed calibration relation for that transmission channel (block 508). Also, a combined or joint set of calibration weights can be used for one or more access channel transmission channels. Alternatively, this summed calibration relationship or calibration instruction based on the summed calibration relationship can be transmitted to one or more access terminals. The access terminals will then apply weights based on the summed calibration relationship to decode the transmissions received at the access terminal.

Also in some aspects, calibration weights are used for a particular AGC state, but not for other AGC states. As such, the processing according to block 508 then only applies to the AGC state corresponding to block 500.

7 illustrates another method for calibrating an antenna array for transmission. Channel estimates for the forward link are received from access terminals (block 600). As described above, these channel estimates may be generated from forward link pilots transmitted by the access node. In addition, channel estimates for reverse link information, for example, reverse link channel pilot signals, are generated by the access node (block 602).

After the estimates of both the forward link and the reverse link are collected, a calibration relation is determined that uses multiple channel estimates for multiple access terminals (block 604). In some aspects, the most recent estimate of the forward link channel and reverse link channel is used with respect to each other over time. In such cases, a plurality of estimates for a given access terminal may be performed based on successive pairs of channel estimates from the forward link and reverse link estimates.

As described with respect to FIG. 3, there may be some time lag between different calculations and transfers. Further, functionality for blocks 600 and 602 can take place substantially simultaneously or at different points in time for the same or different access terminals. Therefore, channel estimates may be determined for a given access terminal based on channel estimates of the forward link and reverse link transmissions, which may or may not be sequential in time.

The co-calibration relationship can be obtained by using the co-optimization process, as described in relation to FIG. 2, for example, equation (8).

Each transmission from each transmission channel of the access node is then weighted with weights based on the co-calibration relationship for that transmission channel (608). Also, a combined or joint set of calibration weights can be used for one or more access channel transmission channels. Alternatively, this co-calibration relationship or calibration instruction based on the co-calibration relationship can be transmitted to one or more access terminals. The access terminals then apply weights based on the co-calibration relationship to decoding transmissions received at the access terminal.

Also in some aspects, calibration weights are used for a particular AGC state, but not for other AGC states. As such, the processing of block 608 is then applied only to the state of the AGC corresponding to block 600.

FIG. 8 illustrates an example wireless communication system 1300. The wireless communication system 1300 describes one base station and one terminal for short. However, it should be understood that the system may include more than one base station and / or more than one terminal, wherein additional base stations and / or terminals may be substantially similar or different from the exemplary base station and terminal described below. In addition, it is necessary to understand that the base station and / or terminal can use the systems (FIGS. 1-5) and / or methods (FIGS. 6-7 and 10) described herein to facilitate wireless communication between them.

As shown in FIG. 8, in a forward link transmission at an access node 1305, a transmit (TX) data processor 1310 receives, formats, encodes, interleaves, and modulates (or displays symbols) traffic data and provides modulation symbols (“data symbols”) . A symbol modulator 1315 receives and processes data symbols and pilot symbols and provides a symbol stream. A symbol modulator 1320 multiplexes the data symbols and pilot symbols on the appropriate subcarriers, provides a signal value of zero for each unused subcarrier, and obtains a set of N transmission symbols for N subcarriers for each symbol period. Each transmission symbol may be a data symbol, a pilot symbol, or a signal value of zero. Pilot symbols can be sent continuously in each symbol period. It is understood that pilot symbols can be time division multiplexed (TDMC), frequency division multiplexed (OFDM), orthogonal frequency division multiplexed (OFDM), code division multiplexed (IFRC), etc. A symbol modulator 1320 may transform each set of N transmission symbols into a time domain using an N-point inverse fast Fourier transform (IFFT) to obtain a “transformed” symbol that contains N time-domain code elements. A symbol modulator 1320 typically repeats a portion of each transformed symbol to obtain a corresponding symbol. The repeatable part is known as the cyclic prefix and is used to counteract the delay spread in the wireless channel.

Transmitter unit 1320 (TMTR) receives and converts the symbol stream into one or more analog signals and additionally brings to a certain state (for example, amplifies, filters, and upconverts) the analog signals to generate a forward link signal suitable for transmission over a wireless channel . The forward link signal is then transmitted via antenna 1325 to the terminals. At terminal 1330, antenna 1335 receives a forward link signal and provides a received signal to receiver unit 1340 (RCVR). The receiver unit 1340 brings to a certain state (for example, filters, amplifies, and downconverts) the received signal and digitizes the signal brought to a certain state to obtain samples. A symbol demodulator 1345 removes a cyclic prefix attached to each symbol, converts each received transformed symbol to a frequency domain using an N-point fast Fourier transform (FFT), obtains N received symbols for N subcarriers for each symbol period, and provides received pilot symbols for processor 1350 for channel estimation. The symbol demodulator 1345 further receives a frequency response estimate for the forward link from the processor 1350, performs data demodulation on the received data symbols to obtain data symbol estimates (which are estimates of the transmitted data symbols), and provides data symbol estimates for the RX data processor 1355, which demodulates (for example, performs symbol mappings), eliminates interleaving, and decodes data symbol estimates to recover the transmitted traffic data. The processing by the symbol demodulator 1345 and the RX data processor 1355 is complementary to the processing by the symbol modulator 1315 and TX data processor 1310, respectively, in the access node 1300.

On the reverse link, TX data processor 1360 processes the traffic data and provides data symbols. A symbol modulator 1365 receives and multiplexes data symbols with pilot symbols, performs modulation, and provides a stream of symbols. Pilot symbols may be transmitted on subcarriers that have been assigned to terminal 1330 for pilot transmission, where the number of pilot subcarriers for the reverse link may be the same or different from the number of pilot subcarriers for the forward link. The transmitter unit 1370 then receives and processes the symbol stream to generate a reverse link signal, which is transmitted by the antenna 1335 at the access node 1310.

At access node 1310, a reverse link signal from terminal 1330 is received by antenna 1325 and processed by receiver unit 1375 to obtain samples. A symbol demodulator 1380 then processes the samples and provides received pilot symbols and data symbol estimates for the reverse link. An RX data processor 1385 processes data symbol estimates to recover traffic data transmitted by terminal 1335. A processor 1390 performs channel estimation for each active terminal transmitting on the reverse link.

The processor 1390 may also be configured to generate a calibration relationship and a co-calibration relationship, or a co-calibration relationship, as described in relation to FIGS. 2, 6 and 7, respectively.

Processors 1390 and 1350 direct (e.g., manage, coordinate, organize, etc.) processing at access node 1310 and terminal 1335, respectively. The respective processors 1390 and 1350 can be connected to memory units (not shown) that store program codes and data. Processors 1390 and 1350 can also perform calculations to derive frequency and impulse response estimates for the reverse link and forward link, respectively.

As shown in FIG. 9, the access node may comprise a main unit (OB) 1450 and a radio unit (RB) 1475. The OB 1450 includes digital baseband components of the access node. For example, OB 1450 may include a baseband component 1405 and an intermediate frequency (IF) digital processing unit 1410. The IF digital processing unit 1410 digitally processes the data of the radio channel at an intermediate frequency by performing functions such as filtering, channelization, modulation, and the like. RB 1475 includes analog radio subsystems of the access node. As used in this document, the radio unit is an analog radio subsystem of the access node or a transceiver station of another type with direct or indirect connection to a mobile switching center or corresponding device. A radio unit typically serves a particular sector in a communication system. For example, RB 1475 may include one or more receivers 1430 connected to one or more antennas 1435a-t for receiving radio communications from mobile subscriber units. In one aspect, one or more power amplifiers 1482a-t are coupled to one or more antennas 1435a-t. An analog-to-digital (A / D) converter 1425 is connected to the receiver 14. The A / D converter 1425 converts the analog radio signals received by the receiver 1430 into a digital input signal for transmission to the baseband component 1405 via an IF digital processing unit 1410. RB 1475 may also include one or more transmitters 120 connected to the same or different antennas 1435 for transmitting radio signals to access terminals. A digital-to-analog (D / A) converter 1415 is connected to the transmitter 1420. The D / A converter 1415 converts the digital communication signals received from the baseband component 1405 through an IF digital processing unit 1410 into an analog output signal for transmission to mobile subscriber units. In some aspects, a multiplexer 1484 for multiplexing multi-channel signals and multiplexing a plurality of signals including a speech signal and a data signal. The central processor 1480 is connected to the main unit 1450 and the radio unit to control various processing, which includes the processing of a speech signal or data.

For multiple access systems (e.g., frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDM), code division multiple access (CDMA), time division multiple access (TDMA) ), etc.) many terminals can simultaneously transmit on the reverse link. For such a system, pilot subcarriers may be shared between different terminals. Channel estimation techniques can be used in cases where the pilot subcarriers for each terminal cover the entire operational range (possibly with the exception of the edges of the range). Such a pilot subcarrier structure would be desirable to obtain frequency spacing for each terminal. The methods described herein can be implemented by various means. For example, these methods may be implemented in hardware, software, or a combination thereof. To implement hardware, the processing units used for channel estimation can be implemented in one or more specialized integrated circuits (specialized ICs), digital signal processing processors (DSP), digital signal processing devices (DSP), programmable logic devices (PLU), programmable gate arrays (FDA), processors, controllers, microcontrollers, microprocessors, other electronic units designed to perform the functions described in this document those, or combinations thereof. With software, implementation can be performed using modules (e.g., procedures, functions, etc.) that perform the functions described in this document. Software codes may be stored in a memory unit and executed by processors 1390 and 1350.

10 illustrates an additional method for calibrating an antenna array for transmission. A determination is made regarding the transmission interval after the last calibration for the current state of the AGC to be used for transmission (block 1500). In some cases, this interval may be a function of elapsed time, in others it may be a function of the number of transmissions, on the forward link, on the reverse link, or both, after the last calibration for the AGC state. This determination is based on a threshold T, which can be predefined or changed based on conditions, for example, loading.

If the transmission interval is greater than T, then another calibration operation is performed in which channel estimates for the forward link are received from access terminals (block 1502) and channel estimates for the reverse link are generated by the access node (block 1504). After the channel estimates for both the forward link and the reverse link are collected, a calibration relationship is determined that uses the multiple channel estimates for the multiple access terminals (block 1506).

After the channel estimates for both the forward link and the reverse link are collected, a calibration relationship is determined that uses the multiple channel estimates for the multiple access terminals (block 1512). Each transmission for the AGC state from each transmission channel of the access node is then weighted, and weighting factors based on the joint calibration relation for this transmission channel are used for the AGC state (1510).

If the transmission interval is greater than τ, then the calibration vector, for example, weighting factors, for a particular state of the AGC, is selected from the memory (block 1512). Each transmission for the AGC state from each transmission channel of the access node is then weighted with weighting factors based on memory weights for the AGC state (1510).

The above describes examples of one or more embodiments. Of course, it is not possible to describe any possible combination of components or methods for the purpose of describing the aforementioned embodiments, but it will be understood by one skilled in the art that numerous additional combinations and variations of various embodiments are possible. Therefore, it is intended that the described embodiments cover all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. In addition, to the extent that the term “includes” is used in the detailed description or in the claims, such a term is meant to include in a sense similar to the term “comprising” used in the claims.

Claims (27)

1. A method for calibrating an antenna array in a wireless network, comprising:
receiving first channel estimation information corresponding to transmissions to the first access terminal;
determining second channel estimation information corresponding to transmissions from the first access terminal;
receiving third channel estimation information corresponding to transmissions to the second access terminal;
determining fourth channel estimation information corresponding to transmissions from the second access terminal; and
determining a calibration relationship based on the first, second, third and fourth channel estimation information for at least the first and second access terminals,
wherein the definition of the calibration relationship contains:
determining a first calibration relationship based on the first and second channel estimation information;
determining a second calibration relationship based on the third and fourth channel estimation information; and
determining a calibration relationship based on combining the first and second calibration relationships. 2. The method of claim 1, wherein the combination comprises averaging the first and second calibration relationships. 3. The method according to claim 1, in which the first and second calibration relationships contain many elements, each of which corresponds to at least one antenna of the access node communicating with the first and second access terminals,
moreover, the association contains:
normalization of the first calibration relationship;
normalization of the second calibration relationship; and
determining a calibration relationship based on a matrix including a first and second calibration relationship. 4. The method according to claim 3, in which the determination of the calibration relationship, based on the matrix, contains the expansion of the matrix using the expansion in singular values. 5. A method for calibrating an antenna array in a wireless network, comprising:
receiving first channel estimation information corresponding to transmissions to the first access terminal;
determining second channel estimation information corresponding to transmissions from the first access terminal;
receiving third channel estimation information corresponding to transmissions to the second access terminal;
determining fourth channel estimation information corresponding to transmissions from the second access terminal; and
determining a calibration relationship based on the first, second, third and fourth channel estimation information for at least the first and second access terminal,
wherein the definition of the calibration relation contains a solution to the equation:

where Z _{i, k, u} is a diagonal matrix, the diagonal elements of which are elements of the estimate h _{i, k, u} ,

reverse link channel vectors, and subscripts i, k, u are tone, time, and user indices, respectively. 6. The method according to claim 5, in which the solution comprises using the method of minimum mean square error (ISCED) to solve the equation. 7. A method for calibrating an antenna array in a wireless network, comprising:
receiving first channel estimation information corresponding to transmissions to the first access terminal;
determining second channel estimation information corresponding to transmissions from the first access terminal;
receiving third channel estimation information corresponding to transmissions to the second access terminal;
determining fourth channel estimation information corresponding to transmissions from the second access terminal;
determining a calibration relationship based on the first, second, third and fourth channel estimation information for at least the first and second access terminal;
receiving fifth channel estimation information corresponding to transmissions to the third access terminal;
determining sixth channel estimation information corresponding to transmissions from the third access terminal; and
determining a calibration relationship based on the first, second, third, fourth, fifth, and sixth channel estimation information for at least the first, second, and third access terminal. 8. A wireless communication device comprising:
at least two antennas; and
a processor coupled to at least two antennas, the processor being configured to determine a calibration relationship for communicating with each of the plurality of access terminals, wherein the processor acts to
receiving first channel estimation information corresponding to transmissions to the first access terminal;
determining second channel estimation information corresponding to transmissions from the first access terminal;
receiving third channel estimation information corresponding to transmissions to the second access terminal;
determining fourth channel estimation information corresponding to transmissions from the second access terminal;
determining a calibration relationship based on the first, second, third and fourth channel estimation information for at least the first and second access terminal,
wherein the definition of the calibration relationship contains:
determining a first calibration relationship based on the first and second channel estimation information;
determining a second calibration relationship based on the third and fourth channel estimation information; and
determining a calibration relationship based on combining the first and second calibration relationships. 9. The wireless communications apparatus of claim 8, wherein the processor is configured to combine the relationships by averaging the first and second calibration relationships. 10. The wireless communications apparatus of claim 8, wherein the first and second calibration relationships comprise a plurality of elements, each of which corresponds to at least one of said antennas, wherein the processor is configured to combine the relationships by normalizing the first calibration relationship, normalizing the second calibration relationships; and determining a calibration relationship based on a matrix including the first and second calibration relationships. 11. The wireless communications apparatus of claim 10, wherein the processor is configured to use singular value decomposition to decompose the matrix to obtain a calibration relationship. 12. A wireless communications device, comprising:
at least two antennas; and
a processor coupled to at least two antennas, the processor being configured to determine a calibration relationship based on a plurality of forward link channel estimates and reverse link channel estimates from a plurality of access terminals, for communication with each of a plurality of access terminals,
the processor is configured to determine the calibration relationship by solving the equation:

where Z _{i, k, u} is a diagonal matrix, the diagonal elements of which are elements of the estimate h _{i, k, u} ,

reverse link channel vectors, and subscripts i, k, u are tone, time, and user indices, respectively. 13. The wireless communications apparatus of claim 12, wherein the processor is configured to solve the equation using the ISCED method. 14. A wireless communication device, comprising:
means for receiving first channel estimation information corresponding to transmissions to the first access terminal;
means for determining second channel estimation information corresponding to transmissions from the first access terminal;
means for receiving third channel estimation information corresponding to transmissions to the second access terminal;
means for determining fourth channel estimation information corresponding to transmissions from the second access terminal;
means for determining a calibration relationship based on the first, second, third, and fourth channel estimation information for at least the first and second access terminals;
means for determining a first calibration relationship based on the first and second channel estimation information;
means for determining a second calibration relationship based on the third and fourth channel estimation information; and
means for determining a calibration relationship based on combining the first and second calibration relationships. 15. The device according to 14, in which the means for determining the calibration relationship based on the combination contains a means for averaging the various calibration relationships. 16. The device according to 14, in which the first and second calibration relationships contain many elements, each of which corresponds to at least one antenna of the access node communicating with the first and second access terminals, and the means for determining contains:
means for normalizing the first calibration relationship;
means for normalizing the second calibration relationship; and means for determining a calibration relationship based on a matrix including a first and second calibration relationship. 17. A carrier-readable medium having instructions stored thereon for use by the processor, the processor performing the following actions when accessing these instructions:
receiving first channel estimation information corresponding to transmissions to the first access terminal;
determining second channel estimation information corresponding to transmissions from the first access terminal;
receiving third channel estimation information corresponding to transmissions to the second access terminal;
determining fourth channel estimation information corresponding to transmissions from the second access terminal;
determining a calibration relationship based on the first, second, third and fourth channel estimation information for at least the first and second access terminal; determining a first calibration relationship based on the first and second channel estimation information;
determining a second calibration relationship based on the third and fourth channel estimation information; and
determining a calibration relationship based on combining the first and second calibration relationships. 18. The processor-readable medium of claim 17, wherein said instructions further comprise instructions for averaging the first and second calibration ratios. 19. The processor-readable medium of claim 17, wherein the first and second calibration relationships comprise a plurality of elements, each of which corresponds to at least one antenna of an access node communicating with the first and second access terminals, said instructions for combining the relationships calibrations contain instructions for normalizing the first calibration relationship;
normalization of the second calibration relationship; and
determining a calibration relationship based on a matrix including the first and second calibration relationships. 20. The processor-readable medium of claim 17, wherein said instructions for determining a matrix-based calibration relationship include instructions for decomposing the matrix using decomposition in singular values. 21. A wireless communication device, comprising:
at least two antennas and
a processor coupled to at least two antennas, the processor being configured to determine a calibration relationship for communicating with each of the plurality of access terminals, wherein the processor acts to receive first channel estimation information corresponding to transmissions to the first access terminal;
determining second channel estimation information corresponding to transmissions from the first access terminal;
receiving third channel estimation information corresponding to transmissions to the second access terminal;
determining fourth channel estimation information corresponding to transmissions from the second access terminal;
determining a calibration relationship based on the first, second, third and fourth channel estimation information for at least the first and second access terminals;
receiving fifth channel estimation information corresponding to transmissions to the third access terminal;
determining sixth channel estimation information corresponding to transmissions from the third access terminal; and
determining a calibration relationship based on the first, second, third, fourth, fifth, and sixth channel estimation information for at least the first, second, and third access terminals. 22. A wireless communication device comprising
means for receiving first channel estimation information corresponding to transmissions to the first access terminal;
means for determining second channel estimation information corresponding to transmissions from the first access terminal;
means for receiving third channel estimation information corresponding to transmissions to the second access terminal;
means for determining fourth channel estimation information corresponding to transmissions from the second access terminal;
and
means for determining a calibration relationship based on the first, second, third and fourth channel estimation information for at least the first and second access terminals, wherein the determination of the calibration relationship contains a solution to the equation:

where Z _{i, k, u} is a diagonal matrix, the diagonal elements of which are elements of the estimate h _{i, k, u} ,

reverse link channel vectors, and subscripts i, k, u are tone, time, and user indices, respectively. 23. The device according to item 22, in which the said means for solving contains means for using the ISCED method to solve the equation. 24. A wireless communication device, comprising:
means for receiving first channel estimation information corresponding to transmissions to the first access terminal;
means for determining second channel estimation information corresponding to transmissions from the first access terminal;
means for receiving third channel estimation information corresponding to transmissions to the second access terminal;
means for determining fourth channel estimation information corresponding to transmissions from the second access terminal;
means for determining a calibration relationship based on the first, second, third, and fourth channel estimation information for at least the first and second access terminals;
means for receiving fifth channel estimation information corresponding to transmissions to the third access terminal;
means for determining sixth channel estimation information corresponding to transmissions from the third access terminal; and
means for determining a calibration relationship based on the first, second, third, fourth, fifth, and sixth channel estimation information for at least the first, second, and third access terminals. 25. Media read by the processor, having instructions stored on it for use by the processor, the processor performing the following actions when accessing these instructions:
receiving first channel estimation information corresponding to transmissions to the first access terminal;
determining second channel estimation information corresponding to transmissions from the first access terminal;
receiving third channel estimation information corresponding to transmissions to the second access terminal;
determining fourth channel estimation information corresponding to transmissions from the second access terminal; and
determining a calibration relationship based on the first, second, third and fourth channel estimation information for at least the first and second access terminals, wherein said instructions for determining the calibration relationship contain instructions for solving the equation:

where Z _{i, k, u} is a diagonal matrix, the diagonal elements of which are elements of the estimate h _{i, k, u} ,

reverse link channel vectors, and subscripts i, k, u are tone, time, and user indices, respectively. 26. The processor-readable medium of claim 25, wherein said solution instructions comprise instructions for using the ISCED method to solve the equation. 27. Media readable by the processor, having instructions stored on it for use by the processor, the processor, when accessing these instructions, performs the following actions:
receiving first channel estimation information corresponding to transmissions to the first access terminal;
determining second channel estimation information corresponding to transmissions from the first access terminal;
receiving third channel estimation information corresponding to transmissions to the second access terminal;
determining fourth channel estimation information corresponding to transmissions from the second access terminal;
determining a calibration relationship based on the first, second, third and fourth channel estimation information for at least the first and second access terminals;
receiving fifth channel estimation information corresponding to transmissions to the third access terminal;
determining sixth channel estimation information corresponding to transmissions from the third access terminal; and
determining a calibration relationship based on the first, second, third, fourth, fifth, and sixth channel estimation information for at least the first, second, and third access terminals.

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