HK1116941A - Radiated power control for a multi-antenna transmission - Google Patents

Description

Radiated power control for multi-antenna transmission

Background

1. Field of the invention

The present invention relates generally to communications, and more particularly to techniques for controlling radiated power for multi-antenna transmission.

2. Background of the invention

Wireless communication networks are widely deployed to provide various communication services such as data, voice, video, and so on. These networks include Wireless Wide Area Networks (WWANs) that provide communication coverage for large geographic areas (e.g., cities), Wireless Local Area Networks (WLANs) that provide communication coverage for medium-sized geographic areas (e.g., buildings and campuses), and Wireless Personal Area Networks (WPANs) that provide communication coverage for small geographic areas (e.g., homes). A wireless network generally includes one or more access points (or base stations) that support communication for one or more user terminals (or wireless devices).

Wireless communication networks typically operate in designated frequency bands. In the united states, the Federal Communications Commission (FCC) is a regulatory agency that limits radiated power levels for various frequency bands to facilitate efficient use of these frequency bands and to avoid excessive RF interference. For example, IEEE 802.11 WLANs typically operate in U-NII bands covering 5.15 to 5.35 gigahertz (GHz) and 5.725 to 5.825 GHz. Although the U-NII band is unlimited, the wireless station (which may be an access point or a user terminal) needs to limit its radiated power in any spatial direction to within FCC-approved levels to meet the requirements for operation in the U-NII band.

In general, it is desirable to use as much transmit power as possible to improve the signal-to-noise-and-interference ratio (SNR) for data transmission and/or to extend the operating range. A higher SNR may support a higher data rate and/or improve the reliability of the data transmission. The radiated power in a given direction is determined by the amount of transmit power applied to the antenna at the wireless station and the antenna pattern formed by the antenna. If a wireless station is equipped with multiple antennas, these antennas can be used to synthesize an antenna pattern that increases the radiated power in a particular direction, e.g., toward the receiving station. In general, the antenna pattern is not easy to determine because it depends on various factors such as physical properties of each antenna, arrangement and arrangement of antennas, and the like. If the antenna pattern is unknown, the wireless station may assume the maximum possible gain for the antenna pattern and may set the transmit power level accordingly to meet regulatory limits. However, in many cases, no maximum gain for any spatial direction is obtained, and setting the transmit power level based on this maximum gain results in a lower SNR and/or reduced range, both of which are undesirable.

There is therefore a need in the art for techniques for controlling radiated power for multi-antenna transmission.

Disclosure of Invention

Techniques for controlling radiated power with respect to data transmissions sent from multiple antennas to meet radiated power limits are described herein.

According to one aspect of the invention, a method of controlling radiated power for data transmission is described, wherein an array gain is estimated based on a synthesized antenna pattern for data transmission, and transmit power for data transmission is limited based on the array gain and a radiated power limit.

According to another aspect of the invention, an apparatus in a wireless communication network is described that includes a controller that estimates an array gain based on a composite antenna pattern for data transmission and a control unit that limits transmit power for data transmission based on the array gain and a radiated power limit.

According to yet another aspect of the invention, an apparatus is described that includes means for estimating an array gain based on a synthetic antenna pattern for data transmission and means for limiting transmit power for the data transmission based on the array gain and a radiated power limit.

Aspects and embodiments of the invention are described in further detail below.

Brief Description of Drawings

Fig. 1 shows a transmitting station and a receiving station.

Fig. 2 shows the result of eigenvalue decomposition for a plurality of subbands.

Fig. 3 shows a process for controlling the radiation power for data transmission.

Fig. 4 shows a block diagram of a transmitting station and a receiving station.

Detailed Description

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

Fig. 1 shows a wireless communication network 110 having a transmitting station 110 equipped with multiple (T) antennas 114a through 114T and a receiving station 150 equipped with multiple (R) antennas 152a through 152R. The antenna may also be referred to as an antenna element, a radiating element, etc. For simplicity, fig. 1 shows the symbol i for each antenna with a single complex gain g by multiplier 112_iTransmit stations 110 that multiply for spatial processing. In general, spatial processing is more complex, as described below. The outputs of multipliers 112a through 112T are further processed and transmitted from T transmit antennas 114a through 114T, respectively.

The radiation power of the transmit antenna array typically has different intensities in different spatial directions. The time-averaged power density of the power radiated from the transmit antenna array may be given by the real part of the Poynting vector. The following were used:

where ρ (θ, φ) is the time-averaged power density of the transmit antenna array;

h is the magnetic field strength of the transmit antenna array;

η is the impedance of free space, which equals 120 π; and

E_total(θ, φ) is the total electric field strength of the transmit antenna array.

Total electric field intensity E_total(theta, phi) and the time-averaged power density ρ (theta, phi) can be expressed as a function of spatial direction, theta being the angle of azimuth (or horizontal rotation) and phi being the angle of elevation (vertical rotation). For a single antenna, the electric field E (θ, φ) depends on the design of the transmit antenna. For example, different electric field patterns are obtained for dipole antennas, whip antennas, planar antennas, and the like. For an antenna array with multiple radiating elements for transmission, the total electric field E_total(theta, phi) is the complex electric field strength from each radiating elementDegree E_iThe sum of (theta, phi).

The Total Radiated Power (TRP) from the antenna array can be obtained by integrating the total time-averaged power density over the reference sphere as follows:

the total radiated power represents the total power radiated from the T-transmit antenna in all spatial directions.

The Effective Isotropic Radiated Power (EIRP) from the antenna array can be calculated as follows:

where ρ is_maxIs the maximum value of the total time-averaged power density ρ (θ, φ) over the entire range of θ and φ. EIRP is the power required for an isotropic antenna (radiating the same power in all spatial directions) to generate the same field in all directions as the maximum field from the antenna array.

The maximum directivity D of the antenna array can be expressed as:

maximum gain of the antenna array, also referred to as total array gain G_totalCan be expressed as:

where ε is the efficiency of the antenna array and P_txIs the total transmit power fed into all elements of the transmit antenna array.

The FCC defines specific limits for EIRP for wireless stations operating in the U-NII band. If the total array gain G_totalIs known or can be calculated, the total transmit power P can be adjusted_txSo that the wireless station meets the EIRP limits imposed by the FCC. However, as shown in equations (1) through (5), the total array gain is not easily calculated or determined.

The EIRP of an antenna array depends on the maximum value or rho of the total time-averaged power density rho (theta, phi)_maxWhich in turn depends on the total electric field E_totalMaximum value of (theta, phi). From equation (1), ρ_maxCan be expressed as:

wherein E_maxIs E_totalMaximum value of (theta, phi). E_maxDependent on the complex gain g_iAnd an electric field pattern K for each of the T transmit antennas in the array_i(θ, φ) and may be expressed as:

wherein k is₀Is a free space wave vector;

R_iis the vector pointing from the phase reference point to the transmit antenna i; and

U_iis a unit vector pointing from the phase reference point to the far field point.

For simplicity, it may be assumed that all radiating elements in the antenna array have the same radiation pattern, such that fori＝1，...，T K_i(θ, Φ) ═ K (θ, Φ). In this case, E may be_maxThe estimation is as follows:

item(s)Corresponding to the gain of the antenna array (or array gain), which may be denoted as G_array. The array gain may also be referred to as an array factor, steering gain (steering gain), etc. The term max (K (θ, φ)) corresponds to the gain of the individual radiating element (or element gain), which may be denoted as G_ant。

Element gain G_antIndicating how well a given transmit antenna increases the effective radiated power in a particular spatial direction compared to an isotropic antenna. Total array gain G_totalCan be estimated using equation (8) as follows:

G_total≤G_array·G_ant (9)

to ensure that the EIRP limit for a given operating scenario is met, the total array gain can be conservatively estimated as follows:

G_total，dB≈10·log₁₀(T)+G_ant，dBi (10)

wherein G is_ant，dBiThe gain of an antenna element given in decibel units (dBi); and

G_total，dBis the total array gain given in dB.

dBi is equal to 10 times the logarithm (base 10) of the electric field strength of the transmitting antenna divided by the electric field strength of the isotropic antenna at the same distance. For T-4, the array gain may be given as G_array，dB＝10log₁₀(T) 6.02 dB. The element gain may not be known. In this case, an assumption can be made about the element gain. For example, a component gain of 2dBi may be assumed for an omni-directional antenna. Thus, G_total，dBIn the above example where T is 4, it is 8 dB.

The transmit power may be limited as follows:

P_tx，dBm≤EIRP_limit，dBm-G_total，dB＝EIRP_limit，dBm-10·log₁₀(T)-G_ant，dBi (11)

wherein EIRP_limit，dBmEIRP limits given in dBm units; and

P_tx，dBmis the total transmit power applied to the transmit antenna array, also given in dBm units. dBm is a logarithm of power units, and 0dBm equals 1 milliwatt (mW).

Equation (11) indicates that the total transmit power applied to the antenna array may be determined by the total array gain G_total，dBReduced to ensure that the EIRP limit is met. In many cases, the total array gain estimated by equation (10) is not achieved. This implies that limiting the transmit power as shown in equation (11) is a conservative strategy that may result in a reduced range and/or data rate. Improved performance may be achieved by estimating the total array gain in a more accurate manner (e.g., based on the integrated antenna pattern) and reducing the amount of transmit power in proportion to the total array gain. Such adaptive strategies may operate wireless stations closer to EIRP limits, which may improve range and/or data rate.

In network 100, a multiple-input multiple-output (MIMO) channel formed by T transmit antennas and R receive antennas may be formed by an R T channel response matrixHAnd (5) characterizing. The matrix can be given as:

wherein item H_j，iR and T, which represent the coupling or complex channel gain between the transmit antenna i and the receive antenna j.

Can convert the channel response momentMatrix ofHDiagonalization to obtainHWherein S is ≦ min { T, R }. The profiles may be considered orthogonal spatial channels of a MIMO channel. Diagonalization can be performed byHSingular value decomposition ofHIs performed by eigenvalue decomposition of the correlation matrix. The eigenvalue decomposition can be expressed as:

R＝H ^H·H＝E·Λ·E ^H (13)

whereinRIs thatHThe T × T correlation matrix of (1);

Eis a unitary matrix of T x T, whose columns areRThe feature vector of (2);

Λis thatRA T × T diagonal matrix of eigenvalues of (a); and

“^H"denotes conjugate transpose.

Unitary matrixEBy properties ofE ^H·E＝ICharacterization, whereinIIs an identity matrix. The columns of the unitary matrix are orthogonal to each other, and each column has a unit power. Diagonal matrixΛIncluding possible non-0 values along the diagonal and 0 values at other locations.ΛIs that the diagonal element ofRAnd represents the characteristic value ofHPower gain of the S-profile of (1). The eigenvalues may be ordered or sorted such that λ₁≥λ₂≥...≥λ_SWherein λ is₁Is the largest eigenvalue and λ_SIs the smallest eigenvalue. Maximum eigenvalue λ₁Also called principal eigenvalue lambda_pemTo correspond to λ₁Is referred to as a main signature. When the characteristic values are ordered, the characteristic values are,Eare correspondingly ordered so thatEIs associated with the maximum eigenvalue andEis associated with the minimum eigenvalue.

For a Time Division Duplex (TDD) network, the downlink (or forward link) and uplink (or reverse link), which are the communication links between the access point and the user terminals, share the same frequency band. In this case, calibration is performed to solveThe downlink and uplink channel responses may be assumed to correspond to each other after accounting for the differences in the transmit and receive chains at the access point and user end. I.e., ifHRepresenting the channel response matrix from antenna array A to antenna array B, the corresponding channel represents the coupled channel from array B to array AH ^TIs given inH ^TTo representHThe transposing of (1). For a TDD network, a transmitting station may estimate based on pilots received from a receiving stationHAnd can be combined withHDecomposing to obtainEAndΛ. For Frequency Division Duplex (FDD) networks, the downlink and uplink are allocated different frequency bands and the downlink channel response matrix may not correlate well with the uplink channel response matrix. For an FDD network, the receiving station may estimate based on the pilot received from the transmitting stationHWill beHDecomposing to obtainEAndΛand will beEAndΛor equivalent information, is sent back to the transmitting station.

The transmitting station may utilize eigen steering (eigen steering) to transmit data to improve performance. Guided by features, transmitter station utilizationEIn the transmitting vector ofHWhich generally provides better performance than simply transmitting data from the T transmit antennas without any spatial processing. Receiver station utilizationEReceive the feature vector ofHData transmission on the profile of (1). Table 1 shows spatial processing by a transmitting station, symbols received at a receiving station, and spatial processing by the receiving station for feature steering.

TABLE 1 feature guidance

Spatial processing at a transmitting station	Received vector	Spatial processing at a receiving station
			x es＝E·s	r es＝H·x es+n	* es＝Λ -1·E H·H H·r es

In the context of table 1, the following,sis a T x 1 vector with S data symbols corresponding to those transmitted on the S-characteristic pattern,x _esis a T x 1 vector with T transmit symbols sent from T transmit antennas,r _esis an R x 1 vector with R received symbols obtained from R receive antennas,nis an R × 1 noise vector, an* _esIs a T x 1 vector having symbols corresponding to the S detected data symbols, which issWherein estimates of the data symbols are transmitted.

If only the dominant profile is used for data transmission, it may be based on the eigenvalues λ for the dominant profile_pemThe array gain is estimated as follows:

G_pem，dB＝10·log₁₀(λpem) (14)

wherein G is_pem，dBThe array gain for the main signature is given in dB. Principal eigenvalue λ_pemGenerally less than the number of transmitting antennas, or lambda_pem< T. The array gain may be limited to a predetermined value, e.g., G_pem，dB4dB or some other value.

The total transmit power may then be limited using equations (11) and (14) as follows:

P_tx，dBm≤EIRP_limit，dBm-G_pem，dB-G_ant，dBi (15)

if multiple signatures are used for data transmission, the transmit power radiates in different spatial directions determined by the eigenvectors associated with the signatures. The array gain may be estimated based on eigenvalues of the signature for data transmission, as follows:

where M is the number of signatures used for data transmission; and

G_mem，dBarray gain is given in dB units for the multi-profile.

The total transmit power may be limited as follows:

P_tx，dBm≤EIRP_limit，dBm-G_mem，dB-G_ant，dBi (17)

equation (17) is similar to equation (15) while having an array gain G for the multi-feature type_mem，dBReplacing array gain G for main features_pem，dB. Equations (11), (15) and (17) are compared, because G is often the case_pem，dB＜G_mem，dB＜10·log₁₀(T), higher transmit power may be used for data transmission over one or more profiles to achieve better system performance.

Network 100 may utilize multi-carrier modulation techniques such as Orthogonal Frequency Division Multiplexing (OFDM). OFDM effectively partitions the overall system bandwidth into multiple (K) orthogonal frequency sub-bands, which are also referred to as tones, sub-carriers, frequency bins, and frequency channels. With OFDM, each subband is associated with a respective subcarrier that may be modulated with data.

For a MIMO network utilizing OFDM (or a MIMO-OFDM network), a channel response matrix for each subband k may be obtainedH(k) And may be decomposed to obtain a matrix of eigenvectors for the subbandsE(k) And a matrix of eigenvaluesΛ(k) In that respect The eigenvalues for each subband may be ranked from maximum to minimum and the eigenvectors for that subband may be ranked accordingly.

Fig. 2 illustrates the result of eigenvalue decomposition for K subbands in a MIMO-OFDM network. A set of K diagonal matricesΛ(k) K, is shown along an axis 210 representing a frequency range. Each matrixΛ(k) S eigenvalue λ of_m(k) M 1.., S, located on the diagonal of the matrix. Axis 212 along each matrixΛ(k) And represents a spatial extent. The wideband profile m is formed by the profiles m for all K subbands. Broadband signature m and a set of K eigenvalues λ_m(k) K, which is associated with the frequency response over K subbands of the entire wideband signature. A main wideband signature and a maximum eigenvalue λ for each of the K subbands₁(k) And (4) associating. A set of eigenvalues for each wideband signature is shown by the shaded box along the dashed line 214. For each wideband signature that experiences frequency selective fading, the eigenvalues of the wideband signature are different for different values of k.

For a MIMI-OFDM network, the transmitting and receiving stations may perform the spatial processing shown in table 1 for each sub-band used for data transmission.

If only the primary wideband signature is used for data transmission, the array gain may be estimated based on the maximum eigenvalue for all K subbands of the primary wideband signature as follows:

wherein G is_pwem，dBIs about the array gain of the main broadband signature. Or the array gain may be estimated based on the average of the K eigenvalues for the main wideband signature as follows:

the total transmit power may then be limited as shown in equation (15), but with an array gain G for the dominant wideband profile_pwem，dBReplacing array gain G for dominant features_pem，dB。

If multiple wideband signatures are used for data transmission, the transmit power radiates in different spatial directions determined by the eigenvectors for these wideband signatures. The array gain may be estimated based on eigenvalues of a wideband signature for data transmission, as follows:

wherein G is_mwem，dBIs about the array gain of the multi-wideband profile. The transmit power may then be limited as shown in equation (17), but with array gain G for multiple wideband profiles_mwem，dBReplacing array gain G for multiple features_mem，dB。

The transmitting station may also transmit data using spatial spreading to improve diversity. Spatial spreading refers to the simultaneous transmission of symbols from multiple transmit antennas, possibly with different amplitudes and/or phases determined by the steering vector used for the symbols. Spatial spreading is also known as pilot diversity, transmit steering, pseudo-random transmit steering (pseudo-random transmit), and the like. Table 2 shows spatial processing by a transmitting station, received symbols at a receiving station, and spatial processing by a receiving station for spatial spreading.

TABLE 2 spatial expansion

Spatial processing at a transmitting station	Received vector	Spatial processing at a receiving station
			x es＝V·s	r ss＝H·x ss+n	* ss＝D x·M x·r ss

In the context of table 2, the following,sis a T x 1 vector of data,x _ssis a tx 1 transmit vector and is,r _ssis an R x 1 received vector and,* _ssis a T x 1 detection vector that is,Vis a T x T steering matrix for spatial spreading,M _xis a T x R spatial filter matrix,D _xis a T x T diagonal matrix. Matrix arrayM _xAndD _xmay be derived using, for example, a Minimum Mean Square Error (MMSE) technique or a Channel Correlation Matrix Inversion (CCMI) technique. For the MMSE technique, the frequency of the MMSE technique,andD _mmse＝[diag[M _mmse·H _eff]]^-1whereinH _eff＝H·VAnd σ_n ²Is noiseThe variance of (c). In the case of the CCMI technique,and isD _ccmi＝I。

Using spatial spreading, the transmitting station steers the matrix differently over the entire time and/or frequency rangeVSpatial processing is performed such that the data transmission follows the ensemble of effective channels. The steering matrix may be a pseudo-random matrix, a matrix generated from a different synthesis of a base matrix (e.g., a Walsh matrix or a Fourier matrix) and scalars (e.g., 1, -1, + j, and-j) for rows of the base matrix, or other matrices.

For data transmission with spatial spreading, the array gain can be estimated asOr may be set to some other value. The transmit power may then be defined as shown in equation (15), but with array gain G for spatial spreading_array，dB ^ssReplacing array gain G for dominant features_pem，dB。

Fig. 3 illustrates a process 300 for controlling radiated power with respect to a data transmission sent from a multiple transmit antenna. A synthetic antenna pattern is determined based on at least one steering vector for spatial processing of the data transmission (block 312). Different spatial processing modes or techniques have different integrated antenna modes. For example, the features direct the generation of a synthetic antenna pattern directed to the receiving station, while the spatial extension generates a spatially extended synthetic antenna pattern. In any case, the array gain is estimated based on the synthetic antenna pattern (block 314). The array gain may be estimated based on the spatial processing mode used for data transmission and the parameters (e.g., eigenvalues) applicable for that mode. For feature steering, the array gain may be estimated based on eigenvalues for the dominant signature, maximum or average eigenvalues for the dominant wideband signature, multiple eigenvalues for multiple subbands of at least one wideband signature, and so on. For spatial spreading, the array gain may be set to a predetermined value (e.g., 0 dB). The array gain can also be set to different predetermined values for different spatial spreading patterns. For example, proficiency in directing the features depending on the used feature sets the array gain to a first value (e.g., from 0 to 4dB) and sets the array gain to a second value (e.g., 0dB) for spatial spreading. The element gain for each transmit antenna used for data transmission may also be determined or estimated (block 316). The transmit power for the data transmission is then defined based on the array gain, the element gain, and the radiated power limit (e.g., the EIRP limit) (block 318).

Fig. 4 shows a block diagram of transmitting station 110 and receiving station 150 in network 100. Transmitting station 110 may be an access point or a user terminal. Receiving station 150 may also be an access point or a user terminal.

At transmitting station 110, a Transmit (TX) data processor 420 receives traffic data from a data source 412 and processes (e.g., encodes, interleaves, and symbol maps) the traffic data to generate data symbols, which are modulation symbols for data. TX spatial processor 422 receives data symbols from TX data processor 420, multiplexes into pilot symbols, and performs spatial processing (e.g., as illustrated in tables 1 and 2 for feature steering and spatial spreading, respectively)Not shown) and provides T streams of transmit symbols to TX gain control unit 424. Unit 424 scales the transmit symbols such that the total transmit power P_tx，dBmEnsuring compliance with EIRP Limit EIRP_limit，dBmFor example, as shown in equations (11), (15) or (17). Unit 424 provides the T scaled transmit symbol streams to T transmitter units (TMTR)426a through 426T. Each transmitter unit 426 performs OFDM modulation (if applicable) to generate data chips, which are further processed (e.g., converted to analog, amplified, filtered, and frequency upconverted) to generate a modulated signal. Transmitter units 426a through 426T provide T modulated signals for transmission from T antennas 114a through 114T, respectively.

At receiving station 150, R antennas 152a through 152R receive the T transmitted signals and each antenna 152 provides a received signal to a respective receiver unit (RCVR) 454. Each receive unit 454 processes its received signal and provides a stream of received symbols to a Receive (RX) spatial processor 456. An RX spatial processor 456 performs receiver spatial processing (or spatial matched filtering) on the received symbols from all R receive units 454 (e.g., as shown in tables 1 and 2) and provides detected data symbols. RX processor 460 then processes (e.g., demaps, deinterleaves, and decodes) the detected data symbols and provides decoded data to a data receiver 462.

Controllers 430 and 470 control the operation of the processing units at transmitting station 110 and receiving station 150, respectively. Memory units 432 and 472 store data and/or program codes used by control controllers 430 and 470, respectively.

For a TDD network, receiving station 150 may transmit a pilot to transmitting station 110. Transmitting station 110 may derive a channel response matrix for each subband of the data transmission and decompose each channel response matrix to obtain eigenvalues and eigenvectors for the subband. Transmitting station 110 may perform (1) spatial processing for eigen-steering based on the eigenvectors, (2) spatial processing for spatial expansion based on the steering matrix, or (3) no spatial processing. The controller 430 may perform the process of fig. 3, determine a synthetic antenna pattern based on the steering vectors for spatial processing, estimate an array gain based on the synthetic antenna pattern, estimate an element gain for each transmit antenna, and limit transmit power based on the array gain, the element gain, and the EIRP limit.

The techniques described herein enable a transmitting station to estimate an array gain based on a synthetic antenna pattern formed from steering vectors used for data transmission. The transmit power for the data transmission is then limited (e.g., by scaling the steering vector and/or adjusting the transmit power applied to each antenna) to ensure that the EIRP limit is met regardless of the channel characteristics.

The radiation power control techniques described herein may be implemented by various means. For example, these techniques may be implemented in hardware, software, or a combination thereof. For a hardware implementation, the processing units used to control the radiated power may be implemented within one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.

For a software implementation, the radiant power control technique may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a memory unit (e.g., memory unit 432 in fig. 4) and executed by a processor (e.g., controller 430). The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (23)

1. A method of controlling radiated power for data transmission, comprising:

estimating an array gain based on a synthetic antenna pattern for data transmission; and

defining a transmit power for data transmission based on the array gain and radiated power limits.

2. The method of claim 1, further comprising:

determining the synthetic antenna pattern based on at least one steering vector for spatial processing of data transmission.

3. The method of claim 1, wherein estimating an array gain based on the synthetic antenna pattern comprises:

determining characteristic values of spatial channels for said data transmission, an

Deriving the array gain based on the eigenvalues.

4. The method of claim 1, wherein estimating an array gain based on the synthetic antenna pattern comprises:

determining a plurality of eigenvalues of a plurality of spatial channels for said data transmission, an

Deriving the array gain based on the plurality of eigenvalues.

5. The method of claim 1, wherein estimating an array gain based on the synthetic antenna pattern comprises:

determining a plurality of eigenvalues of a plurality of subbands of at least one wideband spatial channel used for said data transmission, an

Deriving the array gain based on the plurality of eigenvalues.

6. The method of claim 1, wherein estimating an array gain based on the synthetic antenna pattern comprises:

determining a plurality of eigenvalues of a plurality of subbands of a wideband spatial channel used for said data transmission, an

Deriving the array gain based on a largest eigenvalue of the plurality of eigenvalues.

7. The method of claim 1, wherein estimating an array gain based on the synthetic antenna pattern comprises:

determining a plurality of eigenvalues of a plurality of subbands of a wideband spatial channel used for said data transmission, an

Deriving the array gain based on an average of the plurality of eigenvalues.

8. The method of claim 1, wherein estimating an array gain based on the synthetic antenna pattern comprises:

setting the array gain to a predetermined value if the integrated antenna mode is a spatially extended integrated antenna mode.

9. The method of claim 1, wherein estimating an array gain based on the synthetic antenna pattern comprises:

determining a spatial processing mode for said data transmission, an

Setting an array gain of a spatial processing mode for the data transmission to a predetermined value.

10. The method of claim 1, further comprising:

estimating an element gain for each of a plurality of antennas used for the data transmission, and wherein a transmit power for the data transmission is defined based further on the element gain.

11. The method of claim 1, wherein the radiated power limit is an Effective Isotropic Radiated Power (EIRP) limit.

12. An apparatus in a wireless communication network, comprising:

a controller that estimates an array gain based on the integrated antenna pattern for data transmission; and

a control unit to define a transmit power for data transmission based on the array gain and the radiated power limit.

13. The device of claim 12, wherein the controller determines an integrated antenna pattern based on at least one steering vector for spatial processing of the data transmission.

14. The apparatus of claim 12, wherein the controller determines at least one eigenvalue of at least one spatial channel for the data transmission and derives the array gain based on the at least one eigenvalue.

15. The apparatus of claim 12, wherein the controller determines a plurality of eigenvalues for a plurality of subbands of at least one wideband spatial channel for the data transmission and derives the array gain based on the plurality of eigenvalues.

16. The apparatus of claim 12, wherein the controller sets the array gain to a predetermined value if the integrated antenna mode is a spatially extended integrated antenna mode.

17. The apparatus of claim 12, wherein the controller estimates an element gain for each of a plurality of antennas used for the data transmission, and wherein processor defines the transmit power for the data transmission further based on the element gain.

18. An apparatus in a wireless communication network, comprising:

means for estimating an array gain based on a synthetic antenna pattern for data transmission; and

means for defining a transmit power for the data transmission based on the array gain and a radiated power limit.

19. The apparatus as recited in claim 18, further comprising:

means for determining the synthetic antenna pattern based on at least one steering vector for spatial processing of the data transmission.

20. The apparatus of claim 18, wherein the means for estimating the array gain based on the synthesized antenna pattern comprises:

means for determining at least one characteristic value of at least one spatial channel used for said data transmission, an

Means for deriving the array gain based on the at least one characteristic value.

21. The apparatus of claim 18, wherein the means for estimating the array gain based on the synthesized antenna pattern comprises:

means for determining a plurality of characteristic values for a plurality of frequency subbands of at least one wideband spatial channel used for said data transmission, and

means for deriving the array gain based on the plurality of eigenvalues.

22. The apparatus of claim 18, wherein the means for estimating the array gain based on the synthesized antenna pattern comprises:

means for setting the array gain to a predetermined value if the integrated antenna mode is a spatially extended integrated antenna mode.

23. The apparatus as recited in claim 18, further comprising:

means for estimating a component gain for each of a plurality of antennas used for the data transmission, and wherein transmit power for the data transmission is defined further based on the component gain.