WO2014106343A1

WO2014106343A1 - Method and apparatus for selecting transmit antennas in wireless system

Info

Publication number: WO2014106343A1
Application number: PCT/CN2013/070152
Authority: WO
Inventors: Dalin Zhu; Ming Lei; Hui Li; Lingyang Song
Original assignee: Nec (China) Co., Ltd.
Priority date: 2013-01-07
Filing date: 2013-01-07
Publication date: 2014-07-10
Also published as: CN104904133B; CN104904133A

Abstract

Embodiments of the disclosure provide a method and apparatus for selecting transmit antennas in a wireless system. The method may comprise steps of determining a target number for transmit antennas in the wireless system to maximize energy efficiency; and selecting a target number of transmit antennas associated with a maximized energy efficiency from all transmit antennas in the wireless system.

Description

METHOD AND APPARATUS FOR SELECTING TRANSMIT ANTENNAS IN

WIRELESS SYSTEM

FIELD OF THE INVENTION

[0001] Embodiments of the present invention generally relate to communication techniques. More particularly, embodiments of the present invention relate to a method and apparatus for selecting transmit antennas in a wireless system.

BACKGROUND OF THE INVENTION

[0002] With growing energy demand and increasing energy price, a great deal of attentions has been attached to energy efficiency (EE) in development of wireless systems.

[0003] With respect to large scale antenna systems, which are allowed to use much more antennas (e.g., 100 antennas or more) than in conventional wireless systems, energy efficiency is becoming increasingly important. One disadvantage of employing large-scale antennas in a wireless system is the associated complexity, which results from separate radio frequency chains for employed transmit antennas. As such, in the case that all the transmit antennas are employed, the corresponding energy efficiency may not be the optimal.

[0004] In view of the foregoing problems, there is a need to employ transmit antennas selection in a wireless system, e.g., a MIMO system comprising large-scale multiple antennas, so as to effectively and efficiently improve energy efficiency of the wireless system. SUMMARY OF THE INVENTION

[0005] The present invention proposes a solution which selects transmit antennas to be employed in a wireless system. Specifically, embodiments of the present invention provide methods and apparatuses for selecting transmit antennas in a wireless system, which can effectively improve energy efficiency of the wireless system.

[0006] According to a first aspect of the present invention, embodiments of the invention provide a method for selecting transmit antennas in a wireless system. The method may comprise: determining a target number for transmit antennas in the wireless system to maximize energy efficiency; and selecting a target number of transmit antennas associated with a maximized energy efficiency from all transmit antennas in the wireless system.

[0007] According to a second aspect of the present invention, embodiments of the invention provide an apparatus for selecting transmit antennas in a wireless system. The apparatus may comprise: a determiner configured to determine a target number for transmit antennas in the wireless system to maximize energy efficiency; and a selector configured to select a target number of transmit antennas associated with a maximized energy efficiency from all transmit antennas in the wireless system.

[0008] Other features and advantages of the embodiments of the present invention will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Embodiments of the invention are presented in the sense of examples and their advantages are explained in greater detail below, with reference to the accompanying drawings, where

[0010] FIG. 1 illustrates a flow chart of a method 100 selecting transmit antennas in a wireless system according to an embodiment of the invention;

[0011] FIG. 2 illustrates a flow chart of a method 200 for determining a target number for transmit antennas in the wireless system to maximize energy efficiency according to another embodiment of the invention;

[0012] FIG. 3 illustrates a flow chart of a method 300 for determining a target number for transmit antennas in the wireless system to maximize energy efficiency according to yet another embodiment of the invention; and

[0013] FIG. 4 illustrates a block diagram of an apparatus 400 for selecting transmit antennas in a wireless system according to embodiments of the invention.

[0014] Throughout the figures, same or similar reference numbers indicate same or similar elements. DETAILED DESCRIPTION OF EMBODIMENTS

[0015] Various embodiments of the present invention are described in detail with reference to the drawings. The flowcharts and block diagrams in the figures illustrate the apparatus, method, as well as architecture, functions and operations executable by a computer program product according to the embodiments of the present invention. In this regard, each block in the flowcharts or block may represent a module, a program, or a part of code, which contains one or more executable instructions for performing specified logic functions. It should be noted that in some alternatives, functions indicated in blocks may occur in an order differing from the order as illustrated in the figures. For example, two blocks illustrated consecutively may be actually performed in parallel substantially or in an inverse order, which depends on related functions. It should also be noted that block diagrams and/or each block in the flowcharts and a combination of thereof may be implemented by a dedicated hardware-based system for performing specified functions/operations or by a combination of dedicated hardware and computer instructions.

[0016] Reference is first made to FIG. 1, which illustrates a flow chart of a method 100 selecting transmit antennas in a wireless system according to an embodiment of the invention. In accordance with embodiments of the present invention, method 100 may be carried out by, for example, a base station (BS), a base station controller (BSC), a radio network controller (RNC), a gateway, a relay, a server, or any other applicable device.

[0017] After method 100 starts, at step S101, a target number for transmit antennas in the wireless system is determined to maximize energy efficiency.

[0018] With respect to a multiple antenna system, such as a Multiple Input Multiple Output (MIMO) system or a Multiple Input Single Output (MISO) system, there may be to a plurality of transmit antennas in the system. Therefore, the total number of all transmit antennas may be obtained, for example, according to existing solutions known by those skilled in the art.

[0019] In accordance with embodiments of the present invention, wherein the target number for transmit antennas may be determined in several ways. In an embodiment, first, at least one energy efficiency associated with at least one testing number for the transmit antennas may be calculated; the largest energy efficiency may be selected from the at least one energy efficiency; and then, the testing number associated with the largest energy efficiency may be determined as the target number. According to embodiments of the present invention, the testing number is less than or equal to RF chain number (i.e., the number of RF chains) in the wireless system. Further details may be found in descriptions with respect to the embodiment illustrated in FIG. 2.

[0020] In another embodiment, one or more candidate numbers for the transmit antennas may be first determined based on at least one energy efficiency; occupation probabilities for the one or more candidate numbers may be calculated; and then, a candidate number having largest occupation probability may be determined from the one or more candidate numbers as the target number based on the calculated occupation probabilities. According to embodiments of the present invention, the one or more candidate numbers may be determined by: setting a plurality of testing numbers for the transmit antennas, wherein each of the plurality of testing numbers is less than or equal to the number of RF chains in the wireless system; calculating a plurality of groups of energy efficiencies associated with the plurality of testing numbers; and determining the one or more candidate numbers based on the plurality of groups of energy efficiencies, wherein each candidate number is associated with the largest energy efficiency in each group of energy efficiencies. Further details may be found in descriptions with respect to the embodiment illustrated in FIG. 3.

[0021] In accordance with embodiments of the present invention, the energy efficiency may be obtained based on spectral efficiency, transmission power and circuit consumption power at transmitting side. For example, the energy efficiency may be calculated by equation (1)

wherein η indicates the energy efficiency, N indicates the total number of the transmit antennas, L indicates a testing number for the transmit antennas, p is Signal to Noise Ratio (SNR) at the transmitting side, P_t is transmission power at the transmitting side, and P_c is the total circuit power consumption of the wireless system .

[0022] According to embodiments of the present invention, the circuit consumption power refers to the total power consumed at the transmitting side. The circuit consumption power P_c may be obtained based on the consumption powers of a

Digital to Analog Converter (DAC), a mixer, active filters at the transmitting side, a frequency synthesizer, a low noise amplifier, an intermediate frequency amplifier, active filters at receiving side, and an Analog to Digital Converter (ADC), etc., respectively. In an embodiment, the circuit consumption power may be calculated by equation (2):

P_c = M_t (P_DAC + P_mix + P_filt ) + 2P_syn + M_r (P_WA + P_mix + PlFA + Pfilr + P ) (2) wherein P_DAC indicates the consumption power of the DAC, P_mix indicates the consumption power of the mixer, P_filt indicates the consumption powers of the active filters at the transmitting side, P_syn indicates the consumption power of the frequency synthesizer, P _A indicates the consumption power of the low noise amplifier, P_IFA indicates the consumption power of the intermediate frequency amplifier, P_filr indicates the consumption powers of the active filters at receiving side, P_ADC indicates the consumption power of the ADC, M_t indicates the number of transmit antennas and M_r indicates the number of receiving antennas.

[0023] With respect to a MIMO system, M_t and M_r both may be an integer larger than 1. Further, for a MISO system, M_r may be equal to 1.

[0024] It is to be noted that, for specific wireless systems, different equations may be applied to calculate the energy efficiency. The above equation (1) is only an example for purpose of illustration, rather than limitation. Likewise, the illustrated equation (2) is also only an example. Those skilled in the art will readily appreciate that other suitable algorithms may be also applicable to embodiments of the present invention.

[0025] At step SI 02, a target number of transmit antennas associated with a maximized energy efficiency are selected from all transmit antennas in the wireless system.

[0026] According to an embodiment of the present invention, multiple channel quality values for multiple groups of transmit antennas may be first calculated, wherein each group comprises a target number of transmit antennas; and then a group of transmit antennas having the largest channel quality value may be selected from the multiple groups according to the multiple channel quality values.

[0027] It is to be noted that, in addition to the embodiment illustrated above, there are other ways to select a target number of transmit antennas, and those skilled in the art will choose a suitable way when implementing embodiments of the present invention.

[0028] Reference is now made to FIG. 2, which illustrates a flow chart of a method 200 for selecting transmit antennas in a wireless system according to another embodiment of the invention. Method 200 may be considered as an embodiment of step S101 of method 100 described above with reference to FIG. 1. In the following description of method 200, at least one testing number for transmit antennas is used to calculate energy efficiency and the testing number associated with the largest energy efficiency is determined as the target number. However, it is noted that this is only for the purpose of illustrating the principles of the present invention, rather than limiting the scope thereof.

[0029] After method 200 starts, at step S201, at least one energy efficiency associated with at least one testing number for the transmit antennas is calculated.

[0030] In accordance with embodiments of the present invention, a testing number may be less than or equal to RF chain number in the wireless system. In some embodiments the RF chain number may be less than or equal to the total number of transmit antennas. For example, for a MIMO system having 100 transmit antennas and 50 RF chains, thus the total number is 100 and the RF chain number is 50, and the testing number may be any integer from 1 to 50. According to the embodiment illustrated with FIG. 2, there is at least one testing number, in other words, one or more testing numbers are employed to find the target number which is associated with the optimal energy efficiency. The one or more testing numbers may have different values in the range of 1 to 50.

[0031] According to embodiments of the present invention, there are 30 testing numbers (e.g., each testing number is a value in the range of 41 to 70), thus 30 energy efficiencies may be calculated according to appropriate algorithms for obtaining the energy efficiency, e.g., by equation (1). Specifically, when the testing number is 41, 42, 43, ..., 69 or 70, the parameter L in the equation (1) is also 41, 42, 43, ..., 69 or 70.

[0032] At step S202, the largest energy efficiency is selected from the at least one energy efficiency.

[0033] Considering the above embodiments, with respect to the calculated 30 energy efficiencies, the largest one may be selected therefrom.

[0034] At step S203, the testing number associated with the largest energy efficiency is determined as the target number.

[0035] Once the largest energy efficiency is selected from the calculated 30 energy efficiencies, the testing number associated with the largest energy efficiency may be determined. According to embodiments, this testing number may be as the target number. In other words, the target number of transmit antennas is a set of transmit antennas which has optimal energy efficiency among the total number of transmit antennas in the wireless system. In some embodiments of the present invention, the target number is equal to the total number. In some other embodiments, the target number is less than the total number; that is, in this case, employing all transmit antennas during transmission will not obtain the optimal energy efficiency.

[0036] FIG. 3 illustrates a flow chart of a method 300 for selecting transmit antennas in a wireless system according to yet another embodiment of the invention. Method 300 may be considered as an embodiment of step S101 of method 100 described above with reference to FIG. 1. In the following description of method 300, one or more candidate numbers are first determined based on energy efficiency, and a target number is then determined from the one ore more candidate numbers based on occupation probabilities of these candidate numbers. In this way, the target number of the transmit antennas may be determined efficiently. However, it is noted that this is only for the purpose of illustrating the principles of the present invention, rather than limiting the scope thereof.

[0037] After method 300 starts, at step S301, a plurality of testing numbers are set for the transmit antennas.

[0038] According to embodiments of the present invention, the testing numbers may be set or defined randomly or according to preference of a skilled in the art. For example, 50 testing numbers may be set, wherein each may be defined as a value in the range from 1 to 50 and different from each other.

[0039] In accordance with embodiments of the present invention, each of the plurality of testing numbers is less than or equal to the number of RF chains in the wireless system.

[0040] According to embodiments of the present invention, the number of the plurality of testing numbers may be predefined, for example by the operator or by those skilled in the art. It is to be noted that, if this number is larger, i.e., there are more testing numbers, the result is more accurate but takes more time; on the other hand, if this number is small, i.e., there are less testing numbers, the accuracy of the result may be reduced to some extent but takes less time.

[0041] At step S302, a plurality of groups of energy efficiencies associated with the plurality of testing numbers are calculated.

[0042] According to embodiments of the present invention, with respect to one testing number, one group of energy efficiencies may be calculated. Thus, one testing number is associated with a group of energy efficiencies.

[0043] According to embodiments of the present invention, the testing number may be less than or equal to the number of RF chains in the wireless system. In an embodiment, when there are 50 testing numbers, 50 groups of energy efficiencies may be calculated, wherein one group of energy efficiencies may be calculated according to equation (1) with respect to one of the 50 testing numbers. For example, when a testing number is M, a group of M energy efficiencies may be calculated, wherein an energy efficiency is calculated with respect to one of M numbers.

[0044] At step S303, one or more candidate numbers are determined based on the plurality of groups of energy efficiencies.

[0045] According to embodiments of the present invention, regarding one group of energy efficiencies, a largest energy efficiency may be obtained from the energy efficiencies in the group. Accordingly, the i^th number associated with the largest in the group of energy efficiencies may be determined as a candidate number, wherein is less than or equal to the current testing number, i.e., i≤M .

[0046] In some embodiments, L testing numbers are set at step S301, thus, L groups of energy efficiencies associated with the L testing numbers are calculated at step S302. Then, at step S303, L candidate numbers may be determined based on the L groups of energy efficiencies.

[0047] At step S304, occupation probabilities for the candidate numbers are calculated. [0048] According to embodiments of the present invention, an occupation probability may be calculated with respect to a candidate number. For example, assuming there are L testing numbers set at step S301 and L=10, thus there are L candidate numbers obtained at step S303, which are 51, 62, 43, 51, 37, 51, 50, 68, 62, and 75, respectively. It may be determined that the candidate number 51 occurs three times, the candidate number 62 occurs twice, and other candidate number (such as 43, 37, 50, 68, and 75) each just occurs once. In some embodiments, the occupation probability of each candidate number may be calculated as the ratio of its occurrence times and total number of the candidate numbers L. Thus, the occupation probability of candidate number 51 is 30%, the occupation probability of candidate number 62 is 20%, and the occupation probability of each of other candidate numbers is 10%.

[0049] At step S305, a candidate number having largest occupation probability is determined as the target number based on the calculated occupation probabilities.

[0050] According to the occupation probabilities of the candidate numbers calculated at step S304, the largest occupation probability may be determined from the calculated occupation probabilities. For example, 30%. Accordingly, the candidate number corresponding to the largest occupation probability may be determined. In the above embodiment, since the candidate number 51 has the largest occupation probability, 30%, it may be determined that the target number is 51.

[0051] According to embodiments of the present invention, method 300 may be implemented with an iteration process as follows.

Initialization:

n=0

select initial number /ⁱ⁵ e L randomly

set p , ^} ] = i and _p [o, /] = 0 for all i≠ I^<5!

Start Iteration:

choose another number _e χ / uniformly

(a) seket Hie optimal of current iteration

if η\ η,Ι * \ > η\ n,V^*~^y \

^L /<^»> = 7<->

/^{, !: !} = /^<- ^h

(c) seiect the optimal after the n iterations

' ^¾ = '^:'^"'

else end if

end for

[0052] In the above,

n denotes the number of iteration;

l ^n> denotes the selected testing number at the n^th iteration; p[n, I] denotes the probability of selecting / antennas after n iterations;

L denotes the set of testing numbers;

η[η,1] denotes the energy efficiency calculated by using / antennas at the n^th iteration; and

D[n,l] indicates that at the n^th iteration, if is selected, then D[n, ] = l and D[n, l≠f ] = 0 .

[0053] At initialization, a testing number /⁽⁰⁾ may be determined randomly. Further, the occupation probability may be initialized as p[n, l⁽⁰⁾ ] = l and p[n, l≠l^(0> ] = 0.

[0054] At each iteration n, another number / ⁽ⁿ⁾ is chosen uniformly and it is different from the previous best choice /^(n_1) . [0055] Next, the objective functions are compared with the newly chosen number / ⁽ⁿ⁾ and the previous one , if the new one performs better, it will set / ⁽ⁿ⁾ as the best choice at iteration n, i.e. l⁽ⁿ⁾ = 1 ⁽ⁿ⁾ , otherwise it keeps the previous result l⁽ⁿ⁾ = /⁽"^_1) . For notational simplicity, the selected number is mapped to the sequence D[n] . If is selected, then D[n, l^*] = l and D[n, /≠/^*] = 0 . D[n] is used to update the occupation probability in the next step.

[0056] Further, the occupation probability p[n] is updated. If M ^(n>[l] is denoted for each / e L as a counter of the number of times / has been selected as the ation probability may be denoted as

That is to say, the algorithm chooses the number which has been selected the most often so far.

[0057] Still further, the occupation probability of the best choice at iteration n, l⁽ⁿ⁾ , is compared with the optimal value after (n-1) iterations, ί^(η_1) . Thus, the optimal value / ⁽ⁿ⁾ may be updated according to the comparison results. As illustrated above, if the occupation probability obtained at the n^th iteration, p[n,l⁽ⁿ⁾ ] , is larger than the occupation probability obtained at the (η-1)^Λ iteration, p[n ^(n~r> ] , then / ^(n> is updated with l^(n> ; otherwise, l ^(n> is updated with f ^(B_1 .

[0058] In this way, the number / ⁽ⁿ⁾ corresponding to the largest energy efficiency is determined as may be determined as a candidate number, and the candidate number / ⁽ⁿ⁾ having the largest occupation probability may be determined as the target number. As such, after perform the iteration process as illustrated above, the target number may be obtained.

[0059] For the purpose of illustrating spirit and principle of the present invention, some specific embodiments thereof have been described above. It will be appreciated by a person skilled in the art that embodiments of the present invention may be varied or modified without departing from the scope of the present invention.

[0060] Reference is now made to FIG. 4, which illustrates a block diagram of an apparatus 400 for selecting transmit antennas in a wireless system according to embodiments of the invention. As shown, the apparatus 400 comprises: a determiner 410 configured to determine a target number for transmit antennas in the wireless system to maximize energy efficiency; and a selector 420 configured to select a target number of transmit antennas associated with a maximized energy efficiency from all transmit antennas in the wireless system.

[0061] In accordance with embodiments of the present invention, the determiner 410 may comprise: a first calculating unit configured to calculate at least one energy efficiency associated with at least one testing number for the transmit antennas, wherein the testing number is less than or equal to the number of RF chains in the wireless system; a first selecting unit configured to select the largest energy efficiency from the at least one energy efficiency; and a first determining unit configured to determine the testing number associated with the largest energy efficiency as the target number.

[0062] In accordance with embodiments of the present invention, the determiner 410 may comprise: a second determining unit configured to determine one or more candidate numbers for the transmit antennas based on at least one energy efficiency; and a first calculating unit configured to calculate occupation probabilities for the one or more candidate numbers; and a third determining unit configured to determine, as the target number, a candidate number having largest occupation probability from the one or more candidate numbers based on the calculated occupation probabilities.

[0063] In some embodiments, the second determining unit of the determiner

410 may comprise: a setting unit configured to set a plurality of testing numbers for the transmit antennas, wherein each of the plurality of testing numbers is less than or equal to the number of RF chains in the wireless system; a second calculating unit configured to calculate a plurality of groups of energy efficiencies associated with the plurality of testing numbers; and a fourth determining unit configured to determine the one or more candidate numbers based on the plurality of groups of energy efficiencies, wherein each candidate number is associated with the largest energy efficiency in each group of energy efficiencies.

[0064] In some embodiments, the selector 420 may comprise: a third calculating unit configured to calculate multiple channel quality values for multiple groups of transmit antennas, wherein each group comprises a target number of transmit antennas; and a second selecting unit configured to select a group of transmit antennas having the largest channel quality value from the multiple groups according to the multiple channel quality values.

[0065] In accordance with embodiments of the present invention, the energy efficiency may be obtained based on spectral efficiency, transmission power and circuit consumption power at transmitting side.

[0066] In some embodiments, the energy efficiency may be calculated by

wherein η indicates the energy efficiency, N indicates the total number of the transmit antennas, L indicates a testing number for the transmit antennas, p is SNR at the transmitting side, P_t is transmission power at the transmitting side, and P_c is total circuit power consumption of the wireless system.

[0067] It is to be noted that the apparatus 400 may be implemented in a RNC, a BS, a BSC, a gateway, a relay, a server, or any other applicable device, and the apparatus 400 may be applied in several communication networks, such as a GSM, CDMA, UMTS and LTE network. It is also to be noted that the obtainer 410 and determiner 420 may be implemented by any suitable technique either known at present or developed in the future. Further, a single device shown in FIG. 4 may be alternatively implemented in multiple devices separately, and multiple separated devices may be implemented in a single device. The scope of the present invention is not limited in these regards.

[0068] It is noted that, in some embodiment of the present disclosure, the apparatus 400 may be configured to implement functionalities as described with reference to FIGs. 1-3. Therefore, the features discussed with respect to any of methods 100 to 400 may apply to the corresponding components of the apparatus 400. It is further noted that the components of the apparatus 400 may be embodied in hardware, software, firmware, and/or any combination thereof. For example, the components of the apparatus 400 may be respectively implemented by a circuit, a processor or any other appropriate selection device. Those skilled in the art will appreciate that the aforesaid examples are only for illustration not limitation.

[0069] In some embodiment of the present disclosure, the apparatus 400 comprises at least one processor. The at least one processor suitable for use with embodiments of the present disclosure may include, by way of example, both general and special purpose processors already known or developed in the future. The apparatus 400 further comprises at least one memory. The at least one memory may include, for example, semiconductor memory devices, e.g., RAM, ROM, EPROM, EEPROM, and flash memory devices. The at least one memory may be used to store program of computer executable instructions. The program can be written in any high-level and/or low-level compilable or interpretable programming languages. In accordance with embodiments, the computer executable instructions may be configured, with the at least one processor, to cause the apparatus 400 to at least perform according to method 100 as discussed above.

[0070] In some embodiment of the present disclosure, the apparatus 400 comprises at least one processor. The at least one processor suitable for use with embodiments of the present disclosure may include, by way of example, both general and special purpose processors already known or developed in the future. The apparatus 400 further comprises at least one memory. The at least one memory may include, for example, semiconductor memory devices, e.g., RAM, ROM, EPROM, EEPROM, and flash memory devices. The at least one memory may be used to store program of computer executable instructions. The program can be written in any high-level and/or low-level compilable or interpretable programming languages. In accordance with embodiments, the computer executable instructions may be configured, with the at least one processor, to cause the apparatus 400 to at least perform according to method 100, 200 or 300 as discussed above.

[0071] Based on the above description, the skilled in the art would appreciate that the present disclosure may be embodied in an apparatus, a method, or a computer program product. In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the exemplary embodiments of this disclosure may be illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0072] The various blocks shown in FIGs. 1 to 3 may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). At least some aspects of the exemplary embodiments of the disclosures may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments of this disclosure may be realized in an apparatus that is embodied as an integrated circuit, FPGA or ASIC that is configurable to operate in accordance with the exemplary embodiments of the present disclosure.

[0073] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any disclosure or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular disclosures. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0074] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[0075] Various modifications, adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. Any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure. Furthermore, other embodiments of the disclosures set forth herein will come to mind to one skilled in the art to which these embodiments of the disclosure pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings.

[0076] Therefore, it is to be understood that the embodiments of the disclosure are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are used herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

WHAT IS CLAIMED IS:

1. A method for selecting transmit antennas in a wireless system, comprising:

determining a target number for transmit antennas in the wireless system to maximize energy efficiency; and

selecting a target number of transmit antennas associated with a maximized energy efficiency from all transmit antennas in the wireless system.

2. The method of Claim 1, wherein determining a target number for transmit antennas in the wireless system to maximize energy efficiency comprises:

determining one or more candidate numbers for the transmit antennas based on at least one energy efficiency;

calculating occupation probabilities for the one or more candidate numbers; and determining, as the target number, a candidate number having largest occupation probability from the one or more candidate numbers based on the calculated occupation probabilities.

3. The method of Claim 2, wherein determining one or more candidate numbers for the transmit antennas based on at least one energy efficiency comprises:

setting a plurality of testing numbers for the transmit antennas, wherein each of the plurality of testing numbers is less than or equal to the number of RF chains in the wireless system;

calculating a plurality of groups of energy efficiencies associated with the plurality of testing numbers; and

detennining the one or more candidate numbers based on the plurality of groups of energy efficiencies, wherein each candidate number is associated with the largest energy efficiency in each group of energy efficiencies.

4. The method of Claim 1, wherein determining a target number for transmit antem as in the wireless system to maximize energy efficiency comprises:

calculating at least one energy efficiency associated with at least one testing number for the transmit antennas, wherein the testing number is less than or equal to the number of RF chains in the wireless system;

selecting the largest energy efficiency from the at least one energy efficiency; and determining the testing number associated with the largest energy efficiency as the target number.

5. The method of any of Claims 1-4, wherein selecting a target number of transmit antennas associated with a maximized energy efficiency from all transmit antennas in the wireless system comprises:

calculating multiple channel quality values for multiple groups of transmit antennas, wherein each group comprises a target number of transmit antennas; and

selecting a group of transmit antennas having the largest channel quality value from the multiple groups according to the multiple channel quality values.

6. The method of any of Claims 1-5, wherein the energy efficiency is obtained based on spectral efficiency, transmission power and circuit consumption power at transmitting side.

7. The method of Claim 6, wherein the energy efficiency is calculated by

wherein η indicates the energy efficiency, N indicates the total number of the transmit antennas, L indicates a testing number for the transmit antennas, p is Signal to Noise Ratio (SNR) at the transmitting side, P_t is transmission power at the transmitting side, and P_c is total circuit power consumption of the wireless system.

8. An apparatus for selecting transmit antennas in a wireless system, comprising: a determiner configured to determine a target number for transmit antennas in the wireless system to maximize energy efficiency; and

a selector configured to select a target number of transmit antennas associated with a maximized energy efficiency from all transmit antennas in the wireless system.

9. The apparatus of Claim 8, wherein the determiner comprises:

a second determining unit configured to determine one or more candidate numbers for the transmit antennas based on at least one energy efficiency; and

a first calculating unit configured to calculate occupation probabilities for the one or more candidate numbers; and

a third determining unit configured to determine, as the target number, a candidate number having largest occupation probability from the one or more candidate numbers based on the calculated occupation probabilities.

10. The apparatus of Claim 9 wherein the second determining unit comprises: a setting unit configured to set a plurality of testing numbers for the transmit antennas, wherein each of the plurality of testing numbers is less than or equal to the number of RF chains in the wireless system;

a second calculating unit configured to calculate a plurality of groups of energy efficiencies associated with the plurality of testing numbers; and

a fourth determining unit configured to determine the one or more candidate numbers based on the plurality of groups of energy efficiencies, wherein each candidate number is associated with the largest energy efficiency in each group of energy efficiencies.

11. The apparatus of Claim 8, wherein the determiner comprises:

a first calculating unit configured to calculate at least one energy efficiency associated with at least one testing number for the transmit antennas, wherein the testing number is less than or equal to the number of RF chains in the wireless system;

a first selecting unit configured to select the largest energy efficiency from the at least one energy efficiency; and

a first determining unit configured to determine the testing number associated with the largest energy efficiency as the target number.

12. The apparatus of any of Claims 8-11 , wherein the selector comprises:

a third calculating unit configured to calculate multiple channel quality values for multiple groups of transmit antennas, wherein each group comprises a target number of transmit antennas; and

a second selecting unit configured to select a group of transmit antennas having the largest channel quality value from the multiple groups according to the multiple channel quality values.

13. The apparatus of any of Claims 8-12, wherein the energy efficiency is obtained based on spectral efficiency, transmission power and circuit consumption power at transmitting side.

14. The apparatus of Claim 13, wherein the energy efficiency is calculated by