Abstract:
The present invention relates to communication using multiple antennas, and more particularly, to an apparatus and method for adaptively adjusting, based on a channel environment, an interval and direction of multiple antennas each of a transmitter and a receiver. A communication method according to the present invention may include verifying information about a channel state based on a pilot signal transmitted for each antenna of a transmitter, adjusting intervals among antennas of a receiver based on the information about a channel state, calculating transmission capacity values according to the adjusted intervals among antennas, and setting an antenna to an antenna interval corresponding to a transmission capacity having a highest value among the transmission capacity values calculated.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2010-0133384, filed on Dec. 23, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to communication using multiple antennas, and more particularly, to an apparatus and method for adaptively adjusting, based on a channel environment, an interval and direction of multiple antennas each of a transmitter and a receiver. 
     2. Description of the Related Art 
     A wireless mobile communication market is growing continuously, and various multimedia services are being used in a wireless environment. Recently, a high capacity of data is being transmitted and a high speed of a data transmission is performed to provide a multimedia service. In turn, this leads to research being conducted on a multi-antenna system for using limited frequency resources effectively. 
     When an interval between antennas is insufficient, a correlation may occur between antennas that may not receive a signal independently. The correlation between antennas at a reception end may deteriorate a degree of freedom of a channel, thereby decreasing a communication capacity of an entire system. 
     SUMMARY 
     An aspect of the present invention provides an apparatus and method for adaptively adjusting an optimal structure of multiple antennas of a transmitter and a receiver based on a channel state that varies over time to obtain a maximum transmission capacity. 
     Another aspect of the present invention also provides an apparatus and method for adjusting directions of multiple antennas of a transmitter and directions of multiple antennas of a receiver based on a channel state. 
     According to an aspect of the present invention, there is provided a communication method using adaptive multiple antennas, the communication method including verifying information about a channel state based on a pilot signal transmitted for each antenna of a transmitter, adjusting intervals among antennas of a receiver based on the information about a channel state, calculating transmission capacity values according to the adjusted intervals among antennas, and setting an antenna to an antenna interval corresponding to a transmission capacity having a highest value among the transmission capacity values calculated. 
     The receiving of the information about a channel state may be verified for each predetermined period. 
     Pilot signals received from each antenna of the transmitter may be received using different time-slots or subcarriers so as to avoid collisions. 
     The adjusting may include calculating a transmission capacity of a received pilot signal while increasing the antenna interval by a predetermined interval. 
     The information about a channel state may include information about a signal to noise ratio (SNR) of a signal received by the receiver. 
     According to another aspect of the present invention, there is provided a communication device using adaptive multiple antennas, the communication device including a channel state information receiver to receive pilot signals from antennas of a transmitter, and to verify information about a channel state based on the pilot signals, a location adjustment unit to adjust locations of the antennas by referring to the information about a channel state based on the pilot signals received from the antennas of the transmitter, and a transmission capacity calculator to calculate transmission capacity values according to the adjusted locations, and to compute a transmission capacity value having a highest value among the transmission capacity values calculated. 
     The channel state information receiver may verify channel states of the pilot signals received from the antennas of the transmitter for each predetermined period. 
     The channel state information receiver may receive the pilot signals received from each antenna of the transmitter using different time-slots or subcarriers so as to avoid collisions. 
     The location adjustment unit may calculate transmission capacity values of received pilot signals while increasing an antenna interval by a predetermined interval. 
     The location adjustment unit may adjust an interval, a location, and a direction of antennas so that the transmission capacity values calculated reach a maximum value. 
     According to still another aspect of the present invention, there is provided a communication method using adaptive multiple antennas, the communication method including transmitting pilot signals so as to correspond to antennas of a receiver, receiving transmission capacity values according to information about a channel state in the receiver, and setting antennas of a transmitter to antenna intervals corresponding to a transmission capacity having a highest value among the received transmission capacity values. 
     The transmission capacity values based on the information about a channel state received in the receiver may be received as response signals when a pilot signal is transmitted in a state in which an antenna setting is changed in an antenna of a transmitter. 
     According to yet another aspect of the present invention, there is provided a communication device using adaptive multiple antennas, the communication device including a pilot signal transmitter to transmit pilot signals corresponding to antennas of a receiver, and a location adjustment unit to adjust locations of antennas by receiving, from the receiver, information about a channel state based on transmission of the pilot signals. 
     The location adjustment unit may set antennas to a location at which a transmission capacity value corresponds to a highest value by verifying the transmission capacity value based on the information about a channel state received from the receiver in response to a change of antenna settings. 
     According to an embodiment of the present invention, it is possible to enhance a transmission capacity by adjusting an interval of a transmission antenna or a reception antenna to be appropriate to a given channel state. 
     According to another embodiment of the present invention, it is possible to enhance a transmission capacity by adjusting a direction of a transmission antenna or a reception antenna to be appropriate to a given channel state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects, features, and advantages of the invention will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a block diagram illustrating a signal transceiver according to embodiments of the present invention; 
         FIG. 2  is a block diagram illustrating a configuration of a receiver according to embodiments of the present invention; 
         FIG. 3  is a diagram illustrating an example of including a transmitter having two antennas and a receiver having two antennas according to embodiments of the present invention; 
         FIG. 4  is a graph illustrating a channel capacity with respect to an antenna interval of  FIG. 3 ; 
         FIG. 5  is a graph illustrating a change of a channel capacity with respect to an antenna interval when locations of a receiver and a transmitter of  FIG. 4  are changed; 
         FIG. 6  is a diagram illustrating an example in which directions of multiple transmitting antennas and multiple receiving antennas are rotated according to embodiments of the present invention; and 
         FIG. 7  is a graph illustrating a change of a channel capacity when directions of multiple receiving antennas are changed according to embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. Exemplary embodiments are described below to explain the present invention by referring to the figures. 
       FIG. 1  is a block diagram illustrating a signal transceiver according to embodiments of the present invention. 
     Referring to  FIG. 1 , a signal transceiver according to embodiments of the present invention may include a transmitter  100  having multiple antennas and a receiver  200  having at least one antenna. 
       FIG. 2  is a block diagram illustrating a configuration of a receiver according to embodiments of the present invention. 
     Referring to  FIG. 2 , a receiver according to embodiments of the present invention may include a channel state information receiver  202 , a location adjustment unit  204 , and a transmission capacity calculator  206 . 
     The channel state information receiver  202  may receive pilot signals from antennas of the transmitter  100  of  FIG. 1 , and may verify information about a channel state based on the pilot signals. 
     The channel state information receiver  202  may verify channel states of the pilot signals received from the antennas of the transmitter  100  for each predetermined period. The channel state information receiver  202  may receive the pilot signals received from each antenna of the transmitter  100  using different time-slots or subcarriers so as to avoid collisions. The information about a channel state may include information about a signal to noise ratio (SNR) of a signal received by the receiver. 
     The location adjustment unit  204  may adjust locations of the antennas by referring to the information about a channel state based on the pilot signals received from the antennas of the transmitter  100 . The location adjustment unit  204  may adjust, based on the information about a channel state, an angle and a direction of receiving a signal for antennas of the receiver  200  of  FIG. 1 , and an interval between antennas of the transmitter  100 . 
     The transmitter  100  may include a location adjustment unit, and may adjust an angle and a direction of the transmitter  100  based on an adjustment of antennas of the receiver  200 . 
     Antennas of the transmitter  100  and the receiver  200  may be adjusted either concurrently or individually. 
     The transmission capacity calculator  206  may calculate transmission capacity values according to the adjusted locations, and may compute a transmission capacity value having a highest value among the transmission capacity values calculated. In particular, transmission capacity calculator  206  may verify a channel state of pilot signals received from the transmitter  100 , and may calculate transmission capacity values that are changed according to an adjusted antenna. 
       FIG. 3  is a diagram illustrating an example of including a transmitter having two antennas and a receiver having two antennas according to embodiments of the present invention. 
       FIG. 3  illustrates a transmitter having two antennas and a receiver having two antennas placed on a table in an indoor conference room. 
     The transmitter  100  and the receiver  200  are spaced apart from each other by about a distance of L. 
     The two antennas of the transmitter  100  are spaced apart from each other by about a distance of d TX , and the two antennas of the receiver  200  are spaced apart from each other by about a distance of d RX . 
       FIG. 4  is a graph illustrating a channel capacity with respect to an antenna interval of  FIG. 3 . 
     The transmitter  100  and the receiver  200  are spaced apart from each other by about a distance L, corresponding to about 3 m, and the transmitter  100  and the receiver  200  are disposed at a location corresponding to coordinates of about 4.5 m and 4 m of a horizontal axis and a vertical axis, respectively. 
     The graph of  FIG. 4  depicts a channel capacity with respect to an antenna interval of the transmitter  100  and an antenna interval of the receiver  200  when the transmitter  100  and the receiver  200  are disposed at a center of a space, an SNR corresponds to about 20 decibels (dB), and a signal having a frequency of about 60 gigahertz (GHz) is used. 
     That is, the graph of  FIG. 4  illustrates that a transmission capacity is relatively superior when an antenna interval corresponds to distances of about 3 millimeters (mm), 8.5 mm, and 15.5 mm. 
       FIG. 5  is a graph illustrating change of a channel capacity with respect to an antenna interval when locations of a receiver and a transmitter of  FIG. 4  are changed. 
     The graph of  FIG. 5  has a similar measuring environment to the graph of  FIG. 4 , and illustrates a changed transmission capacity when the transmitter  100  and the receiver  200  are disposed at a location about 0.3 m along a vertical axis. 
     Referring to the graphs of  FIG. 4  and  FIG. 5 , an optimal antenna interval varies depending on locations of the transmitter  100  and the receiver  200 . 
     Thus, a channel may be changed depending on locations of the transmitter  100  and the receiver  200 , and the location adjustment unit  204  of  FIG. 2  may adjust an antenna interval to be appropriate to a changed channel. 
       FIG. 6  is a diagram illustrating an example in which directions of multiple transmitting antennas and multiple receiving antennas are rotated according to embodiments of the present invention. 
       FIG. 6  illustrates the multiple transmitting antennas having a direction rotated by a value of about θ TX , and the multiple receiving antennas has a direction rotated by a value of about θ RX . 
       FIG. 7  is a graph illustrating change of a channel capacity when directions of multiple receiving antennas are changed according to embodiments of the present invention. 
     In a measuring environment of a transmission capacity of  FIG. 7 , the transmitter  100  and the receiver  200  are disposed at a center of a space for measuring a transmission capacity. The transmitter  100  and the receiver  200  are spaced apart from each other by a distance L, corresponding to about 3 m. Antennas of the transmitter  100  and antennas of the receiver  200  are spaced apart from each other by distances d TX  and d RX , about 5 mm apart, respectively. 
     When a direction of a transmitting antenna corresponds to θ TX =0 degrees in a different measuring environment, a transmission capacity may vary depending on a direction of a receiving antenna θ RX  as illustrated in  FIG. 7  that depicts a transmission capacity with respect to a direction of the receiving antenna. 
     That is, a transmission capacity may vary depending on a direction as well as an interval between antennas of the transmitter  100  or the receiver  200 . 
     The location adjustment unit  204  may set antennas so that data may be received with a relatively high transmission capacity by adjusting an interval of the transmitter  100  and the receiver  200  and by adjusting a direction of antennas. 
     Embodiments of the present invention have been described with an example of changing a setting of antennas at the receiver  200 . However, a setting of antennas based on a channel state may be changed at the transmitter  100  as well as at the receiver  200 . 
     The transmitter  100  may include a pilot signal transmitter to transmit pilot signals to the receiver  200 . The receiver  200  may calculate a transmission capacity value based on a channel state according to pilot signals transmitted from the pilot signal transmitter to the receiver  200 . The transmitter  100  may receive the calculated transmission capacity from the receiver  200  each time a location, an angle, an interval, and the like corresponding to a setting of antennas of the transmitter  100  are adjusted. The transmitter  100  may set antennas to be in a state of receiving a transmission capacity value having a relatively high value based on a result of receiving the transmission capacity value. Accordingly, it is possible to easily receive a signal of a relatively high quality by adjusting an antenna state in at least one of the transmitter  100  and the receiver  200 . 
     The above-described exemplary embodiments of the present invention may be recorded in non-transitory computer-readable media including program instructions to implement various operations embodied by a computer. The media may also include, alone or in combination with the program instructions, data files, data structures, and the like. Examples of non-transitory computer-readable media include magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD ROM discs and DVDs; magneto-optical media such as optical discs; and hardware devices that are specially configured to store and perform program instructions, such as read-only memory (ROM), random access memory (RAM), flash memory, and the like. Examples of program instructions include both machine code, such as produced by a compiler, and files containing higher level code that may be executed by the computer using an interpreter. The described hardware devices may be configured to act as one or more software modules in order to perform the operations of the above-described exemplary embodiments of the present invention, or vice versa. 
     Although a few exemplary embodiments of the present invention have been shown and described, the present invention is not limited to the described exemplary embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.