JP2005136492A - Antenna device and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna device capable of switching between an adaptive antenna and an MIMO system, depending on a propagation environment. <P>SOLUTION: The purpose is attained by an antenna device provided with a propagation environment measuring means for measuring the status of arriving waves of radio waves arriving to a plurality of antenna elements; an application region determining value calculating means for calculating an application region determining value for determining application region of beam transmission for forming directivity by all antenna elements to transmit signals, and diversity transmission for forming directivity for each sub-array to transmit different signals, on the basis of the relation between the status of the arriving waves measured by the propagation environment measuring means and beam width capable of being formed by the plurality of antenna elements; and a transmission system switching means for switching to any one of the beam transmission and the diversity transmission on the basis of the application region determining value calculated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an antenna device capable of switching a radio wave transmission method according to a propagation environment and a control method thereof.

  Adaptive antennas (for example, see Non-Patent Document 1) and MIMO (Multiple Input Multiple Output) systems (for example, see Non-Patent Document 2) as methods for realizing further increase in capacity of third generation mobile communication systems and wireless LAN systems. The technology of this is being actively studied.

  As shown in FIG. 23, the adaptive antenna is an antenna radiation pattern by appropriately controlling the feeding amplitude / phase (weight 1 to weight K) to each of the antennas # 1 to #K by a signal processing (adaptive processor) 200. The maximum signal strength is given to a desired terminal, and radio waves are not radiated as much as possible to the interference terminal.

  On the other hand, the MIMO system is a system that uses array antennas for both transmission and reception signals. In a multi-propagation environment, the transmission status between each antenna and a terminal in a plurality of antennas is different. It is intended to increase the transmission capacity by transmitting different signals and multiplexing them. As described above, the MIMO scheme is a scheme that prepares a plurality of transmission / reception antennas and realizes an increase in transmission capacity, but there are roughly two types in the implementation method. One is an STC type MIMO system that applies transmission diversity technology, and the other is an SDM type MIMO system that uses SDM technology.

  FIG. 24 is a diagram illustrating the concept of the STC type MIMO scheme. As shown in the figure, on the transmission side of the STC type MIMO system, different transmission data is encoded by a space-time coding unit (STC: Space-Time coding) 310 and sent in parallel, and transmission by a plurality of channels is performed. (Refer to non-patent document 4 for STC). The reception side receives a reception signal in which a plurality of channels are mixed, and performs a space-time coding process in STC 320 to decode the reception signal.

On the other hand, FIG. 25 is a diagram showing a concept of an SDM (Space Division Multiplexing) type MIMO system. As shown in the figure, on the transmission side of the SDM MIMO scheme, one transmission data is serial-parallel converted by S / P 350, and a plurality of transmissions are performed by applying complex weights in channel encoders 360 _{1 to} 360 _M. A series is generated. The plurality of transmission sequences generated in this way are transmitted simultaneously from the respective antenna elements 1 to M (see, for example, Non-Patent Document 2). The reception side receives signals transmitted from the antenna elements 1 to M on the transmission side, and performs decoding processing in the channel decoding units 370 _{1 to} 370 _N to separate them into respective series.

  The adaptive antenna and the MIMO system described above are epoch-making technologies for realizing high quality and large capacity in the wireless communication system, but both have been proposed separately, and their application range depends on the situation of incoming waves. Depending on. For example, if the angular spread of the incoming wave is large, the effect of fading is large, and transmission quality is significantly degraded, signal transmission can be compensated by fading by performing diversity transmission using the MIMO method. It becomes. On the other hand, when the angle spread of the incoming wave is small, the direction of arrival of the incoming wave can be accurately estimated, so by performing beam transmission (directional transmission) that forms a beam pattern in any direction, the direction of arrival It is possible to eliminate interference with different terminals. That is, the area where the effect can be obtained is different between the adaptive antenna and the MIMO system.

By the way, as a new technology that supports broadband wireless access, development of a wireless device that can change or add functions such as frequency and communication method by simply rewriting software, that is, a so-called software wireless device (for example, see Non-Patent Document 3) is currently being developed. It is being advanced. For example, as shown in FIG. 26, this software defined radio receives radio waves from antennas # 1 to #n and a receiver (not shown), and receives A / D (A / D converters) 410 _{1 to} 410 _n . High-speed A / D conversion is performed, and the result is processed by software in the digital circuit 420 to extract a signal and output to the input / output device 430. That is, the software defined radio implements a system including modulation / demodulation by software signal processing in order to cope with any communication system. In such a software defined radio, the adaptive antenna and MIMO system functions are realized by software, so it is considered that they can be installed in the same radio and used separately.

In addition, in a radio base station apparatus using an adaptive antenna as described above, a technique that can perform radio communication with good communication quality even when fading correlation is small is disclosed (for example, Patent Documents). 1). According to this technique, fading correlation is monitored, and radio transmission processing is performed by switching between beam transmission and diversity transmission according to the monitoring result, so even if the correlation of fading is small, the communication quality is good. It is described that wireless communication can be performed.
JP 2002-16534 A Nobuyoshi Kikuma, “Adaptive signal processing by array antenna,” Science and Technology Publishing, 1998 Eiichi Murata, “MIMO channel transmission technology for wireless communication,” IEICE Journal, Vol. 86, no. 3, pp. 215-217, March, 2003 Yasuo Suzuki, Junmichi Araki, “Software Radios and Their Development Status in Japan,” IEICE Transactions B, VoLJ84-B, No. 7, pp. 1120-1131, July, 2001 Vahid Tarokh, et. A1., "Space-Time Codes for High Data Rate Wireless Communication: Performance Criterion and Code Construction," IEEE Trans. Information Theory, Vol. 44, No.2, March, 1998

  As described above, the adaptive antenna and the MIMO scheme differ in the area of effect obtained depending on the radio wave propagation situation between the transmitting terminal and the receiving terminal used in the wireless communication system. For this reason, in order to use the adaptive antenna and the MIMO system properly, it is necessary to grasp the radio wave propagation situation and determine which is more appropriate.

  However, the adaptive antenna and the MIMO scheme are independent technologies, and no method has been established for measuring and judging the propagation state in order to use them appropriately. For this reason, at present, it is difficult to implement a different method of the adaptive antenna and the MIMO method in the same wireless device, or to realize both methods by software rewriting that supports software rewriting.

  The present invention has been made in view of the above-described problems, and the object of the present invention is to provide an antenna device capable of switching between an adaptive antenna and a MIMO system according to a propagation environment, and a control method thereof. It is.

  In order to solve the above problems, an antenna device comprising an array antenna composed of a plurality of antenna elements and a control device for controlling the array antenna is used to measure the situation of incoming waves of radio waves arriving at the plurality of antenna elements. Based on the relationship between the propagation environment measurement means that performs the measurement and the state of the arriving wave measured by the propagation environment measurement means and the beam width that can be formed by the plurality of antenna elements. Application region determination value calculating means for calculating an application region determination value for determining an application region of diversity transmission for transmitting different signals by forming directivity for each sub-array and beam transmission for transmitting, and the calculated application region Transmission method switching means for switching to either beam transmission or diversity transmission based on a determination value. It is.

According to claim 2 of the present invention, in the antenna device, the application area determination value calculation means includes:
T = AS / BW
T: Applicable region judgment value AS: Angular spread of incoming wave [°]
BW: Beam width [°]
The application area determination value is calculated according to the above.

  Further, according to claim 3 of the present invention, the antenna device includes a table associating the application area determination value calculated by the application area determination value calculation means, the received power, and the correlation between the antennas, The transmission method switching means obtains a value corresponding to the application area determination value calculated by the application area determination value calculation means based on the received signal from the table, and based on the obtained value, the beam transmission or An application area determination unit that determines an application area of the diversity transmission is provided.

  According to claim 4 of the present invention, in the antenna apparatus, the transmission method switching means switches to the beam transmission when the value obtained from the table is less than a first predetermined value, and obtains the obtained value. When the measured value is greater than or equal to the first predetermined value, it is determined to switch to the diversity transmission.

  According to claim 5 of the present invention, in the antenna device, when diversity transmission is selected by the transmission method switching means, the plurality of antenna elements are divided into an arbitrary set of subarrays, and each subarray And sub-array beam forming means for forming a beam.

  According to claim 6 of the present invention, in the antenna apparatus, when the value obtained from the table is within a predetermined range greater than or equal to a second predetermined value, the transmission method switching means The element is divided into M sets (M is an integer of 2 or more) subarrays, and it is determined to switch to diversity transmission with M branch equal gain or M branch unequal gain.

  According to claim 7 of the present invention, in the antenna device, when diversity transmission is selected by the transmission method switching means, known signal transmitting means for transmitting a known signal to a receiving terminal, and the known signal Feedback information receiving means for receiving feedback information transmitted from the receiving terminal based on the above, and phase control transmitting means for transmitting the transmission signal transmitted from the subarray with a phase difference based on the feedback information. It is a feature.

  According to the present invention, it is possible to appropriately determine whether to apply beam transmission and diversity transmission by obtaining the relationship between the state of the incoming wave and the beam width of the antenna. As a result, switching between beam transmission and diversity transmission according to the propagation environment can be realized, and maximum transmission quality and capacity can always be obtained in any propagation environment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing the configuration of the antenna device according to the present embodiment.

  In the figure, the antenna device 1 includes an array antenna composed of a plurality of antenna elements # 1 to #n, and a control device 10 that controls the array antenna. The antenna device 1 according to the present embodiment is, for example, a device provided in a radio base station of a mobile communication system, and receives a signal transmitted from a terminal (eg, mobile station) with an array antenna, The propagation environment is judged using the static radiation pattern characteristics of the antenna. Based on the determination result, switching can be performed between beam transmission for transmitting signals by forming directivity with all antenna elements, or diversity transmission for transmitting different signals by forming directivity for each subarray. The signal is wirelessly transmitted to the terminal using the transmission method.

  The control device 10 includes an arrival wave estimation unit 11 that implements a DOA (Direction Of Arrival) algorithm for estimating the state of an incoming wave, a beam transmission processing unit 12 that implements a beam transmission algorithm in software, and a diversity. A diversity transmission processing unit 13 that implements a transmission algorithm in software, a beam transmission / diversity transmission switching control unit 14 that performs switching control of beam transmission or diversity transmission, and an application area that is referred to when switching between beam transmission and diversity transmission And an application area table storage unit 15 for storing a table.

  In the present embodiment, the beam transmission / diversity transmission switching control unit 14 uses the estimation result of the arrival wave state estimated by the arrival wave estimation unit 11 and the application region table stored in the application region table storage unit 15. Thus, the transmission method (beam transmission or diversity transmission) optimum for transmission is determined and switched. Details will be described below.

  FIG. 2 is an application area table used for determining application areas of beam transmission and diversity transmission stored in the application area table storage unit 15. This application area table is created based on the relationship between the angle spread (AS) indicating the spread of incoming radio waves and the antenna beam width (BW). Before explaining the details of the creation method, first, FIG. 3 will be used. The operation outline of beam transmission and diversity transmission will be described.

  FIG. 3A is a diagram for explaining beam transmission, and FIG. 3B is a diagram for explaining diversity transmission.

  In the beam transmission, a sharp beam is formed by using all the antennas (antenna elements # 1 to # 16) of the array antenna as shown in FIG. Then, the direction is toward the terminal 100. In the case of beam transmission, the same signal is transmitted from the transmitter TXa20 connected to the array antenna.

  On the other hand, as shown in FIG. 4B, diversity transmission divides the antenna elements # 1 to # 16 of the array antenna in half from the middle (# 1 to # 8, # 9 to # 16), Different signals are transmitted to the subarray and synthesized on the terminal 100 side. That is, different signals are transmitted from the transmitter TXa20 connected to the antenna elements # 1 to # 8 and the transmitter TXb30 connected to the antenna elements # 9 to # 16. In this example, the signal sequence a is transmitted from the transmitter TXa20 and the signal sequence b is transmitted from the transmitter Txb30 at a certain time t1. Similarly, the case where the signal sequence a is transmitted from the transmitter TXa20 and the signal sequence of -b obtained by inverting the phase of the signal sequence b is transmitted from the transmitter TXab30 at the next time t2.

  The beam transmission described above is classified as an adaptive antenna because a signal is transmitted by adaptively forming directivity in an arbitrary direction, and diversity transmission is performed for each transmission antenna (# 1 to # 8, # 8). 9 to # 16), since different information is transmitted, it is classified as a MIMO system. The MIMO (Multi Input Multi Output) system generally refers to a system that performs multiplex communication via a plurality of spatial paths having the same frequency and the same time slot.

  Next, returning to FIG. 2, an application area table for determining application areas of beam transmission and diversity transmission will be described. In the figure, the horizontal axis T of the application area table represents a determination value used for determining the application area, and the vertical axis represents the correlation coefficient (0 to 1) and the power reached to the terminal (= received power deterioration). Quantity [dB]). The correlation wave means a wave having a correlation coefficient with a reference signal close to 1, and the non-correlation wave means a wave with a correlation coefficient with a reference signal close to 0.

  In the present embodiment, T is defined by the following formula.

T = AS / BW (1)
= (SW-BW) / BW
here,
T is an application area determination value,
AS is the angular spread [°] of the incoming wave,
BW is the beam width [°] of the antenna.
The AS is a value that represents the spread of the incoming radio wave. As shown in FIG. 4A, this value rotates the antenna beam (BP: Beam Pattern) of the array antenna in all directions. It can be roughly estimated by searching for a direction in which the output power of the array increases. A method of estimating the state of the incoming wave in this way is called a beam former method (BF). In this embodiment, as an example, the case where the beamformer method is used for estimating the state of the incoming wave is illustrated, but the present invention is not limited to the beamformer method, and other methods such as the Capon method and the maximum entropy are used. Linear Prediction (LP: Linear Prediction), minimum norm method (Min-Norm) based on eigen expansion of correlation matrix of array input, MUSIC (MUltiple SIgnal Classication), ESPRIT (Estimation of Signal Parameters via Rotational Invariance) Techniques) may be used.

  FIG. 4B is a BF spectrum (Pt (θ)) representing a function of the angle and the reception level obtained by scanning the beam as described above. This Pt (θ) is considered to represent the arrival wave distribution with the accuracy of the beam width (BW) of the antenna beam (BP). When the incoming wave arrives with a certain spread, the AS, as shown in FIG. 4B, the measured spread SW of Pt (θ) becomes AS + BW. That is, AS can be estimated by measuring Pt (θ), and the value of AS is SW−BW.

  In the present embodiment, using the above equation (1), a determination value T for use in determining the application area is calculated from the AS estimated from the BF spectrum and the beam width (BW) of the antenna beam (BP). The T calculated in this way, the arrival power reaching the terminal, and the correlation coefficient of the array antenna are associated and created as an application area table.

  In the application area table created in this way, appropriate application areas for AS, BW, beam transmission, and diversity transmission are shown. In this example, the case where the area (a) is set as an application area for beam transmission and the area (b) is set as an application area for diversity transmission is shown.

  Next, an application area determination method for beam transmission and diversity transmission will be described.

  As described above, AS is represented by SW-BW. Therefore, as shown in the above equation (1), when T = (SW-BW) / BW, application areas of beam transmission and diversity transmission are as follows. Can be determined as follows.

  1. Beam transmission is appropriate when T is less than 1.5, and diversity transmission is appropriate when T is greater than 1.5.

  Therefore, in order to prove this, in the present embodiment, simulations and outdoor experiments were performed to determine application areas for beam transmission and diversity transmission. The results of the simulation and outdoor experiment will be described below.

  First, as shown in FIG. 5B, the simulation conditions were such that the incoming wave and the antenna beam were approximated by a square, and the widths thereof were AS and BW, respectively. The incoming waves are considered as a set of 50 waves, and 50 plane waves are uniformly arranged in the AS, the amplitudes are all the same, and the phases are random. In addition, the power of the incoming wave is constant regardless of the AS. In the simulation, this trial was repeated 1000 times, each received power was recorded, and the average power and the correlation coefficient were obtained. FIG. 5A is an antenna pattern illustrating the above simulation conditions. In addition to AS and BW, the total antenna reception power (A), the total arrival wave power (T), and the acquired power (S) are shown. Is illustrated.

Moreover, FIG. 6 is a figure which shows the conditions of an outdoor experiment. In the figure, (a) shows a line-of-sight, and (b) shows a non-line-of-sight situation. A radio signal is transmitted from one transmission antenna (TX), and a 16-channel vector receiver is used as a 16-element array antenna. Recieved.
In the outdoor experiment, the reception characteristics were measured several times while changing the distance and angle between transmission and reception, and the received power was calculated from the measured data. In the line-of-sight situation, the distance between transmission and reception was 20 m, 30 m, the angle X [deg] was 0 °, 5 °, 10 °, 15 °, 20 °, and the number of measurements was 3 times each. Further, in an out-of-sight situation, the distance between transmission and reception was only 30 m, the angle X [deg] was 0 °, 5 °, 10 °, 15 °, 20 °, and the number of measurements was 5 times each.

  Next, simulation results and outdoor experiment results will be described.

  FIG. 7 is a diagram showing simulation results and outdoor experiment results showing the relationship between the number of antenna elements (ports) and the reached power. In the figure, the horizontal axis represents the number of antenna elements that receive radio waves, and the vertical axis represents the relative power from the value at which the maximum power was obtained in line of sight. In the figure, “Sim” represents the simulation result, and “Exp” represents the outdoor experiment result.

  As shown in the figure, it can be seen that the results of the outdoor experiment match the simulation results. Obviously, it can be seen that the received power increases as the number of antenna elements to be received increases, and is proportional to the ratio of the number N of antenna elements (N / 16), that is, the increase in directivity gain. On the other hand, outside the line of sight, it can be seen that the power does not increase above a certain value even if the number of antenna elements is increased. In this case, AS = 10 degrees, and even if it is increased from about 8 elements, an increase in power proportional to the antenna directivity gain cannot be obtained.

  FIG. 8 is a diagram showing the BF spectrum Pt (θ) and the beam pattern BP in a situation where the power does not increase. In both figures, the horizontal axis represents angle [deg] and the vertical axis represents amplitude [dBmV].

  In FIG. 8, the BF spectrum Pt (θ) shown in FIG. 8A is considered to indicate the state of the incoming wave, and it can be seen from FIG. 8 that the incoming wave clearly spreads from the beam. Therefore, the received power does not increase even if a sharp beam is directed there.

  This is summarized in FIG. 9 and FIG. 10 for a specific antenna. FIG. 9 shows a case where element antennas having 16 elements and a beam pattern of 60 degrees are arranged linearly at intervals of 0.7 wavelength, and FIG. 10 shows a case where element antennas of a 120 degree beam pattern are arranged at intervals of 0.5 wavelength. 9 and 10 show simulation results showing AS, received power, and correlation coefficient when a beam is formed by using all 16 elements and when an 8-element sub-array is formed from the middle.

  9 and 10, it can be seen that as the AS becomes wider, the difference in power between 16-element transmission and 8-element transmission becomes smaller. This shows that the received power reaches a peak even when the number of elements is increased as in FIG.

  On the other hand, when the array is divided into two from the middle, the correlation coefficient between the subarrays rapidly decreases as the AS becomes wider. That is, if AS is 10 degrees, the correlation coefficient is very low, 0.2 or less, so if diversity transmission can be performed to increase 3 dB received power (black square mark in the figure), all 16 elements It is possible to transmit higher power than in the case of performing transmission using. This tendency is the same as in FIGS.

  Therefore, in order to clarify general properties, the number of antenna elements is changed to 4, 8, 16, and 32, and in each case, the relationship between AS, power, and correlation coefficient of the full array and the half subarray is simulated. And shown in FIGS. Each figure also shows each BW. The following can be said from these simulation results.

From FIG. 11, the received power is
BW> AS: almost constant (value close to -2 dB when plane wave arrives)
BW <AS: Decreasing in proportion to the magnitude of AS From FIG. 12, the correlation coefficient is
BW> AS: 0.75 or more BW <AS <2 BW: 0.3 to 0.9 (decrease inversely proportional to AS)
2BW <AS: 0.33 or less These results show that the received power and the correlation coefficient are determined by the relationship between the BW of the antenna and the AS of the incoming wave. Thus, FIG. 13 (FIG. 1) shows this relationship organized and reflected in the application area table. In the figure, AS can be represented by SW-BW as already described.

  In summary, in an actual antenna, the following can be said.

  “There is a wireless communication system in which an array antenna consisting of N elements operates as a transmitting antenna and transmits information to a terminal. A radiation pattern BP is formed by multiplying an arbitrary antenna weight Wi, and the BP is rotated in the circumferential direction. The function of received power and angle obtained in this way is defined as a spectrum Pt (θ) (θ is an angle), a radiation pattern BPm when the beam peak is directed to the maximum value direction angle θm of Pt (θ), and a spectrum Pt ( The above equation (1) is defined with the angular widths of two points that are 3 dB lower than the maximum values of θ) as BW and SW.

In the above formula (1),
1. When T is less than about 1.5, all the weights Wi of the antenna element N are controlled so that the radiation pattern has the maximum gain at the angle θm, and communication is performed by forming a beam pattern.
2. When T is approximately 1.5 or more, the antenna elements are divided into two sets of approximately the same number (N / 2) of subarrays, and each of the weights Wi1 and Wi2 of each subarray has a maximum gain at an angle θm. , And perform communication by performing diversity transmission in each sub-array. "
That is, by examining the above-described conditions 1 and 2, it is possible to selectively use beam transmission that operates as an adaptive antenna and diversity transmission that operates as a MIMO system. In the present embodiment, a value of T of about 1.5 indicating the boundary of the adaptive region is set as the first predetermined value.

  The organized result is created as an application area table and held in the application area table storage unit 15. When wirelessly transmitting a signal to a terminal as a communication partner, the control device 10 refers to the application area table and determines whether to perform beam transmission or diversity transmission. FIG. 14 is a flowchart showing a processing procedure for switching control between beam transmission and diversity transmission performed by the control device 10.

  In the figure, in step S1, the incoming wave estimation unit 11 estimates the AS. This estimation result is sent to the beam transmission / diversity transmission switching control unit 14. In step S2, the beam transmission / diversity transmission switching control unit 14 calculates the application region determination value T from the AS estimation result received from the arrival wave estimation unit 11 and the BW. Thereafter, the beam transmission / diversity transmission switching control unit 14 refers to the application storage table stored in the application region table storage 15 unit, and the calculated T is approximately less than 1.5 or approximately 1.5. Whether it is the above or not is determined (step S3), and when T is determined to be less than about 1.5, an instruction signal for performing beam transmission is generated and output to the beam transmission processing unit 12. In the beam transmission processing unit 12, a process of forming a beam pattern and performing communication (step S4) is performed.

  On the other hand, if it is determined in the above determination (step S3) that it is approximately 1.5 or more, an instruction signal for performing diversity transmission is generated and output to the diversity transmission processing unit 13. The diversity transmission processing unit 13 performs processing (step S5) for performing communication by performing diversity transmission in each sub-array.

Thus, according to the present embodiment, the application area determination value for performing application determination of beam transmission and diversity transmission is calculated from the relationship between the state of the incoming wave and the beam width of the antenna, and the calculated application area Since application determination of beam transmission and diversity transmission is performed based on the determination value, switching between beam transmission and diversity transmission can be realized appropriately.
In addition, based on the results of simulations and outdoor experiments, the application area table used in the above application determination is created and managed, so that switching between beam transmission and diversity transmission in a form close to the actual propagation environment is realized. The maximum transmission quality and capacity can always be obtained in any propagation environment.

  Furthermore, since the beam transmission and the diversity transmission are switched by switching the function implemented in the beam transmission processing unit 12 and the function implemented in the diversity transmission processing unit 13, the adaptive antenna and the MIMO according to the propagation environment are configured. Switching between methods can be realized with a software defined radio.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the first embodiment, only two types, ie, one full array and two half sub-arrays, are exemplified as the proper use of beam transmission and diversity transmission. However, the antenna device 1 according to the present embodiment is in the case of diversity transmission (MIMO method). , Diversity transmission is performed by any two sets. For example, as shown in FIG. 15, transmission is performed with the number of antenna elements n (in this example, antenna elements # 1 to #n) sufficient to maximize the reached power, and the remaining elements (in this example, antenna element # n + 1). ˜ # 16) are used as diversity (unequal gain) because the correlation with the body element (#n) is low.

  In the present embodiment, simulations shown in FIGS. 16 to 20 were performed in order to prove this. 16 to 20 are diagrams showing simulation results showing the relationship between AS, power, and correlation in an arbitrary n: 16-n element sub-array in the case of a 16-element array.

  16 to 20, the horizontal axis represents the number of sub-elements (n), the left side of the vertical axis represents the correlation coefficient (voltage) between the antenna sets TXa20 and TXb30, and the right side represents the received power deterioration amount (dB). 16 is AS = 1 degree, FIG. 17 is AS = 3 degrees, FIG. 18 is AS = 6 degrees, FIG. 19 is AS = 10 degrees, and FIG. 20 is AS = 20 degrees. It is a simulation result.

  As shown in the simulation results of FIGS. 16 to 20, the correlation coefficient changes depending on the AS, while a difference appears in the received power ratio between each received power and the subarrays depending on the number of subarrays n. It is possible to determine from the simulation results which subarray configuration is appropriate in which case by diversity transmission (MIMO method). That is, also in this case, an application area as shown in FIG. 21 can be shown. For example, when T is 1.2 (T = C21) or less, beam transmission is performed, and when 1.3 <T <1.7 (T = C22), the unequal gain diversity described in this example (in this example, 2) The sub-array unequal gain diversity is performed, and equal gain diversity (in this example, two sub-array equal gain diversity) is performed when T is 1.7 or more. In particular, in unequal gain diversity, an appropriate number n of sub-array elements in that case can also be defined.

  As already explained, the point at which beam transmission, equal gain / unequal gain diversity is switched depends on the method, so each region cannot be clearly defined here, but such an application region table is created. In addition, if C21 and C22 which are boundaries between the respective regions are clarified by identifying the optimum region in the method, beam transmission and diversity transmission (MIMO) can be easily performed according to the same principle as in the first embodiment. Communication (equal gain / unequal gain branch type) can be used properly, that is, beam transmission and diversity transmission (MIMO communication (equal gain / unequal gain)) must be determined in detail in response to changes in AS. By properly using these, the maximum transmission quality and capacity can always be obtained in any propagation environment.

(Third embodiment)
Next, a third embodiment of the present invention will be described. In the first embodiment and the second embodiment, the case where the full array is divided into two and transmitted by diversity is exemplified.
In the present embodiment, the full array is divided into four to provide 4-branch diversity.

  Also in this embodiment, the same examination as in the first embodiment is performed, the power and the correlation coefficient are clarified by simulation or the like, and the application area can be divided by T. Further, in this case as well, if the same examination as in the second embodiment is performed and the relationship between the power and the correlation is clarified by simulation or the like for T and the number of constituent elements of the four subarrays, the gain equal to T is obtained. / The application area of unequal gain 4-branch diversity becomes clear.

  Therefore, as shown in FIG. 21, if C41 and C42 are further clarified, the application area from all array beam transmission to equal gain / unequal gain diversity transmission of 2, 4 branches can be clarified. In other words, it is possible to determine whether to apply beam transmission and diversity transmission (MIMO method: equal gain / unequal gain of two or four branches), even in the case of a very wide AS. Accordingly, by properly using these, it is possible to always obtain the maximum transmission quality and capacity in any propagation environment.

  In the present embodiment, in FIG. 21, the value of T = C21 represents the second predetermined value. Further, the range from C21 to C22, the range from C22 to C41, the range from C41 to C42, the range from C42 to a certain upper limit value, and these ranges correspond to the predetermined range described in claim 6.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. FIG. 22 is an embodiment showing a case where only phase information is fed back from terminal 100 as a diversity transmission method. In the MIMO scheme, it is common to use STC that transmits different signals in each branch (TXa20, TXb30) and improves communication quality. However, in this embodiment, a known signal is transmitted to the terminal 100 in advance from the TXa 20 and the TXb 30, and the phase difference is fed back to the terminal 100. As a result, terminal 100 can perform in-phase synthesis of the electric field vector of the received signal, and can positively increase the received power.

  Specifically, TXa20 and TXb30 insert and transmit a known signal (replica) XY at the beginning of the signal sequence, and then add information on the XY phase difference fed back from terminal 100 to the transmitted information. To send. The terminal 100 calculates the phase difference α between the two propagation paths from the received XY signals and feeds back to the transmission side. Here, the information to be fed back may be only the phase. Because the two sub-arrays are originally close to each other because they are one full array halved from the middle. For this reason, it is considered that the amplitude of the transmission path is relatively small. Of course, if α is a complex number and phase and amplitude information, that is, a complex signal difference is fed back, the effect is further enhanced.

  In addition, this embodiment can be applied to the first to third embodiments described above, and in this case, the first to third embodiments are different only in that the power can be improved. The same effect as described in the embodiment can be obtained.

(Modification)
Although the embodiments of the present invention have been described above, the above embodiments are merely examples, and various modifications can be made to the above embodiments without departing from the spirit of the present invention. For example, the following modifications can be considered.

  (1) In the above-described embodiment, the case where the beam transmission processing unit 12 and the diversity transmission processing unit 13 are provided independently is illustrated, but the beam transmission processing function and the diversity transmission processing function are implemented in one transmission processing unit. It may be a mode. Note that the beam transmission processing function and the diversity transmission processing function can be upgraded as appropriate by remote download of software by wireless or wire.

  (2) In the above embodiment, the sub-array in which the N-element array antenna is divided into two at equal ratios or the sub-array in which the ratio of the N-element array antenna is changed into two is illustrated. However, the sub-arrays are overlapped at equal intervals. Arrangement is also possible. In this case, the condition is that the elements can be regarded as uncorrelated.

  (3) In each of the above embodiments, a case where the control apparatus 10 is applied to a base station is illustrated as a preferred example. However, even when the control apparatus 10 is applied to a terminal, good transmission characteristics can be realized.

It is a block diagram which shows the structure of the antenna apparatus which concerns on this embodiment. It is an application area | region table | surface used in order to judge the application area | region of beam transmission and diversity transmission. It is a figure for demonstrating the operation | movement outline | summary of beam transmission and diversity transmission. It is a figure for demonstrating a beam former method (BF) and a BF spectrum. It is a figure for demonstrating simulation conditions. It is a figure which shows the conditions of an outdoor experiment. It is a figure which shows the simulation result and the outdoor experiment result which show the relationship between the number of antenna elements (ports) and reach | attainment power. It is a figure which shows BF spectrum Pt ((theta)) and the beam pattern BP in the condition where electric power does not rise. It is a figure which shows the simulation result (0.7 wavelength interval, 60 degree beam) which shows the relationship between the arrival power at the time of 8 element x2 group division | segmentation transmission in a 16 element array, and a correlation coefficient. It is a figure which shows the simulation result (0.5 wavelength space | interval, 120 degree | times beam) which shows the relationship between the arrival power at the time of 8 element x 2 group division | segmentation transmission in a 16 element array, and a correlation coefficient. It is a simulation result which shows the relationship between the angle spread by the number of array elements, and arrival power. It is a simulation result which shows the relationship between the angle spread by the number of array elements, and a correlation coefficient. It is an application area | region table | surface which shows the relationship between an antenna beam width, an incoming wave angle spread, arrival power, and a correlation coefficient, and is used in order to judge the application area | region of beam transmission and diversity transmission. It is a flowchart which shows the process sequence of the switching control of the beam transmission and diversity transmission which are performed with a control apparatus. It is a figure for demonstrating the operation | movement outline | summary of the unequal gain diversity transmission in the 2nd Embodiment of this invention. It is the simulation result (AS = 1 degree) which shows the relationship between the arrival power at the time of 2 division | segmentation transmission of n and 16-n elements in a 16 element array, and a correlation coefficient. It is a simulation result (AS = 3 degree | times) which shows the relationship between the arrival power at the time of 2 group division | segmentation transmission of n and 16-n elements in a 16 element array, and a correlation coefficient. It is a simulation result (AS = 6 degree | times) which shows the relationship between the arrival power at the time of 2 sets division | segmentation transmission of n and 16-n elements in a 16 element array, and a correlation coefficient. It is a simulation result (AS = 10 degree | times) which shows the relationship between the arrival power at the time of 2 group division | segmentation transmission of n and 16-n elements in a 16 element array, and a correlation coefficient. It is a simulation result (AS = 20 degree | times) which shows the relationship between the arrival power at the time of 2 division | segmentation transmission of n and 16-n element in a 16 element array, and a correlation coefficient. It is an application area | region table | surface used in order to judge the application area | region of beam transmission and equal / unequal gain diversity transmission in the 3rd Embodiment of this invention. It is a figure for demonstrating the case where only phase information is fed back from a receiving terminal as a diversity transmission method in the 4th Embodiment of this invention. It is a figure which shows the structural example of an adaptive antenna. It is a figure which shows the concept of STC type MIMO system. It is a figure which shows the concept of a SDM type MIMO system. It is a figure which shows the structural example of a software defined radio.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna apparatus 10 Control apparatus 11 Arrival wave estimation part 12 Beam transmission process part 13 Diversity transmission process part 14 Beam transmission / diversity transmission switching control part 15 Application area | region table memory | storage part 100 Terminal (mobile station)
200 Adaptive processor 210 Adder 310, 320 STC (space-time coding unit)
350 S / P (series-parallel converter)
360 _{1 to} 360 _M channel encoder 370 _{1 to} 370 _N channel decoder 380 P / S (parallel serial converter)
410 _{1 to} 410 _n A / D (A / D converter)
420 Digital circuit 430 Input / output device # 1 to #n, # 1 to #K, # 1 to #M, # 1 to #N Antenna element

Claims (8)

In an antenna device comprising an array antenna composed of a plurality of antenna elements and a control device for controlling the array antenna,
Propagation environment measuring means for measuring the situation of incoming waves of radio waves arriving at the plurality of antenna elements;
Based on the relationship between the state of the incoming wave measured by the propagation environment measuring means and the beam width that can be formed by the plurality of antenna elements, beam transmission and sub-array for transmitting a signal with directivity formed by all antenna elements An application area determination value calculating means for calculating an application area determination value for determining an application area of diversity transmission for forming different directivities and transmitting different signals;
Based on the calculated application area determination value, transmission method switching means for switching to either the beam transmission or the diversity transmission;
An antenna device comprising: The antenna device according to claim 1,
The application area determination value calculation means includes:
T = AS / BW
T: Applicable region judgment value AS: Angular spread of incoming wave [°]
BW: Beam width [°]
In accordance with the antenna device, the application area determination value is calculated. In the antenna device according to claim 1 or 2,
A table associating the application area determination value calculated by the application area determination value calculating means, the received power, and the correlation between the antennas;
The transmission method switching means obtains a value corresponding to the application area determination value calculated by the application area determination value calculation means based on the received signal from the table, and based on the obtained value, the beam transmission or An antenna apparatus comprising: an application area determination unit that determines an application area of the diversity transmission. The antenna device according to claim 3, wherein
The transmission method switching means switches to the beam transmission when the value obtained from the table is less than a first predetermined value, and when the obtained value is greater than or equal to the first predetermined value, An antenna device characterized by determining to switch to transmission. The antenna device according to any one of claims 1 to 4,
An antenna comprising: sub-array beam forming means for dividing the plurality of antenna elements into an arbitrary set of sub-arrays and forming a beam in each sub-array when diversity transmission is selected by the transmission method switching means. apparatus. The antenna device according to any one of claims 1 to 4,
The transmission method switching means divides the plurality of antenna elements into M sets (M is an integer of 2 or more) subarrays when the value obtained from the table is within a predetermined range of a second predetermined value or more, An antenna device characterized by switching to diversity transmission of M branch equal gain or M branch unequal gain. The antenna device according to any one of claims 1 to 4,
Known signal transmitting means for transmitting a known signal to a receiving terminal when diversity transmission is selected by the transmission method switching means;
Feedback information receiving means for receiving feedback information transmitted from the receiving terminal based on the known signal;
Based on the feedback information, phase control transmission means for transmitting a transmission signal transmitted from the subarray with a phase difference;
An antenna device comprising: In a control method of an antenna device composed of a plurality of antenna elements,
Measure the state of incoming waves of radio waves arriving at the plurality of antenna elements,
Based on the relationship between the measured state of incoming waves and the beam width that can be formed by the plurality of antenna elements, directivity is formed by all antenna elements and signal transmission is performed and directivity is formed for each subarray. And calculating an application area determination value for determining an application area of diversity transmission for transmitting different signals,
A method for controlling an antenna apparatus, comprising: switching to either beam transmission or diversity transmission based on the calculated application area determination value.

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