Abstract:
A probe apparatus for ultrasound diagnostic imaging associates with a mmWave-based Personal Basic Service Set (PBSS), performs pairing with an ultrasonic imaging apparatus, and transmits an echo signal received via a transducer portion of the probe, to the ultrasonic imaging apparatus using a signal channel in a 60 GHz frequency band, thereby obviating the need for a data transmission cable and greatly reducing operator inconvenience.

Description:
CLAIM OF PRIORITY 
       [0001]    This application claims priority under 35 U.S.C. §119(a) of the earlier filing date of Korean Patent Application No. 10-2011-0073773, filed on Jul. 25, 2011, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method in which a probe apparatus for ultrasound diagnosis transmits an echo signal to an ultrasonic imaging apparatus, and an apparatus for performing the method. 
         [0004]    2. Description of the Related Art 
         [0005]    Ultrasound diagnostic imaging systems transmit ultrasonic signals from the surface of a human body toward a predetermined region inside the human body and acquire tomographic images of soft-tissue or blood flow by using information obtained from an ultrasonic signal reflected by liquids or tissue inside the human body. Advantages of an ultrasound system are its relatively small size, low cost, real-time display, and the fact that the subject is not exposed to ionizing radiation (e.g., X-rays). Therefore, ultrasound imaging systems are widely used along with other types of image diagnostic devices, such as an X-ray diagnostic device, a computerized tomography (CT) scanner, a magnetic resonance imaging (MRI) device, a nuclear medicine (gamma camera) diagnostic device, etc. 
         [0006]      FIG. 1  illustrates a typical ultrasound diagnostic imaging system  150  as currently in use today, which diagnostic includes a probe  110  for transceiving ultrasonic signals, and an ultrasound diagnostic imaging system body  100 , namely, an ultrasonic imaging apparatus  100 , to which the probe  110  is connected via a cable  120 . However, the cable  120  causes much inconvenience to a person using the ultrasound imaging system  150  to perform an ultrasound test, due to the length (usually 1-2 m), thickness and weight of the cable  120 . 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a method and apparatus for wirelessly transmitting an echo signal to an ultrasonic imaging apparatus without loss. 
         [0008]    According to an aspect of the present invention, there is provided a probe apparatus for ultrasound diagnostic imaging, the probe apparatus comprising: an association performing unit which performs a procedure for associating the probe apparatus with a mmWave-based wireless network; a frame generation unit which generates a data frame with a format suitable for the mmWave-based wireless network, by using an echo signal received via a transducer; and a wireless communication unit which transmits the data frame to an ultrasonic imaging apparatus using a signal channel in a 60 GHz frequency band via the mmWave-based wireless network. 
         [0009]    The mmWave-based wireless network may be a Personal Basic Service Set (PBSS) that follows the WiGig standard of the Wireless Gigabit Alliance (WGA), and the ultrasonic imaging apparatus operates as a PBSS control point (PCP) of the PBSS. 
         [0010]    The probe apparatus may further include a beam forming unit which performs mmWave beamforming of the signal in the 60 GHz frequency band in order to transmit the data frame to the ultrasonic imaging apparatus. 
         [0011]    According to another aspect of the present invention, there is provided a probe apparatus for ultrasound diagnostic imaging, the probe apparatus comprising: a beacon monitoring unit which monitors for the reception of a mmWave beacon from an ultrasonic imaging apparatus of a Personal Basic Service Set (PBSS) with which the probe apparatus is not yet associated, when a user command for making a pairing request is received; a peer determination unit which detects an ultrasonic imaging apparatus which is to be paired with the probe apparatus by using first pairing information included in a received mmWave beacon; an association performing unit which performs a procedure for associating the probe apparatus with a PBSS of the ultrasonic imaging apparatus by using a basic service set ID (BSSID) included in the received mmWave beacon; and a pairing request unit which transmits second pairing information to the ultrasonic imaging apparatus via the PBSS, wherein the first pairing information represents that the ultrasonic imaging apparatus has been requested by a user to perform pairing, and the second pairing information represents that the probe apparatus has been requested by the user to perform pairing. 
         [0012]    The first pairing information may comprise a medium access control (MAC) address of the ultrasonic imaging apparatus and push button configuration (PBC) information representing that a button for requesting pairing by using a PBC technique has been pressed in the ultrasonic imaging apparatus, and the second pairing information comprises a MAC address of the probe apparatus and PBC information representing that a button for requesting pairing by using the PBC technique has been pressed in the probe apparatus. 
         [0013]    The probe apparatus may further comprise a wireless communication unit which transmits an echo signal received via a transducer portion of the probe, to the ultrasonic imaging apparatus via a signal channel in a 60 GHz frequency band via the PBSS of the ultrasonic imaging apparatus. 
         [0014]    The probe apparatus may further comprise a beam forming unit which performs mmWave beamforming with the ultrasonic imaging apparatus. 
         [0015]    According to another aspect of the present invention, there is provided a probe apparatus for ultrasound diagnostic imaging, the probe apparatus comprising: a link formation unit which forms a communication link with an ultrasonic imaging apparatus in a PBSS that uses mmWaves; a margin information processing unit which extracts information about a link margin of the communication link from a link margin response frame received from the ultrasonic imaging apparatus; and a margin control unit which controls the probe apparatus to perform at least one of a change in transmission power of an echo signal, a change in a modulation and coding scheme (MCS) to be applied to the echo signal, a change in beam forming with the ultrasonic imaging apparatus, and a change in channel frequency within a 60 GHz frequency band based on the information. 
         [0016]    The margin information processing unit may transmit a link margin request frame requesting information about the link margin to the ultrasonic imaging apparatus, and the link margin response frame may be received in response to the link margin request frame. 
         [0017]    The link margin request frame may comprise at least one of a category field indicating what kind of frame the link margin request frame belongs to, an action field indicating that the link margin response frame is a link margin request frame from among frames categorized into the kind of frame determined by the category field, and a transmission number field representing the number of times the link margin request frame is transmitted. 
         [0018]    The link margin response frame may comprise a preferred action field that comprises information that indicates a request for one operation from among the change in the transmission power, the change in the MCS, the change in beam forming, and the change in channels, to be performed. 
         [0019]    According to another aspect of the present invention, there is provided an ultrasound diagnostic system comprising: a probe apparatus which is associated with a mmWave-based wireless network, which probe apparatus transmits an echo signal received via a transducer portion of the probe apparatus to an ultrasonic imaging apparatus using a signal channel in a 60 GHz frequency band via the mmWave-based wireless network; and the ultrasonic imaging apparatus which generates an ultrasonic image by using the echo signal received in the 60 GHz frequency band via the mmWave-based wireless network. 
         [0020]    The mmWave-based wireless network may be a personal basic service set (PBSS) that follows the WiGig standard of the Wireless Gigabit Alliance (WGA), and the ultrasonic imaging apparatus operates as a PBSS control point (PCP) of the PBSS. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
           [0022]      FIG. 1  illustrates a prior art ultrasound diagnostic imaging system; 
           [0023]      FIG. 2  illustrates an ultrasound diagnostic imaging system according to an embodiment of the present invention; 
           [0024]      FIG. 3  is a flowchart illustrating a communication process of a probe, according to an embodiment of the present invention; 
           [0025]      FIG. 4  is a flowchart illustrating a process in which the probe performs pairing with an ultrasonic imaging apparatus, according to an embodiment of the present invention; 
           [0026]      FIG. 5  is a flowchart illustrating a pairing process according to an embodiment of the present invention; 
           [0027]      FIG. 6  is a flowchart illustrating a pairing process according to another embodiment of the present invention; 
           [0028]      FIG. 7  is a flowchart illustrating a pairing process according to another embodiment of the present invention; 
           [0029]      FIG. 8  is a flowchart illustrating a pairing process according to another embodiment of the present invention; 
           [0030]      FIG. 9  is a flowchart illustrating a pairing process according to another embodiment of the present invention; 
           [0031]      FIG. 10  is a flowchart illustrating a process of controlling a link margin, according to an embodiment of the present invention; 
           [0032]      FIG. 11  illustrates a format illustrating a link margin response frame according to an embodiment of the present invention; and 
           [0033]      FIG. 12  is a block diagram illustrating a structure of a probe apparatus according to an embodiment of the present invention. 
       
    
    
       [0034]    Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features and structures. 
       DETAILED DESCRIPTION 
       [0035]    The following description, with reference to the accompanying drawings, is provided to assist a person of ordinary skill in the art with a comprehensive understanding of exemplary embodiments of the invention. The description includes various specific details to assist in that understanding but these details are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the exemplary embodiments described herein can be made without departing from the spirit of the invention and the scope of the appended claims. Also, descriptions of well-known functions and constructions may be omitted for clarity and simplicity so as not to obscure appreciation of the present invention by a person of ordinary skill with such well-known functions and constructions. 
         [0036]    The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purposes only and not for the purpose of limiting the invention as defined by the appended claims. 
         [0037]    Expressions such as “at least one of,” when preceding a list of elements, refers to at least one of the entire list of elements and is not intended to be limited individual elements of the list. 
         [0038]    It is to be understood that the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” typically includes reference to one or more of such surfaces. 
         [0039]    Finally, the term “substantially” typically means that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those skilled in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide. 
         [0040]      FIG. 2  illustrates an ultrasound diagnostic imaging system  200  according to an embodiment of the present invention, which diagnostic includes an ultrasonic imaging apparatus  210  and a probe  220  including an ultrasonic wave transducer. The probe  220  and the ultrasonic imaging apparatus  210  are associated with a same mmWave (millimeter Wave)-based wireless network, and the probe  220  transmits an echo signal received via the transducer portion of the probe, to the ultrasonic imaging apparatus  210  using one or more signal channels in the 60 GHz frequency band. The ultrasonic imaging apparatus  210  generates ultrasonic images in various modes, such as B-mode, color flow, and Doppler, by using the ultrasound echo signal transmitted thereto using the 60 GHz frequency band signal channel, and displays the ultrasonic images. 
         [0041]    The probe  220  generates an ultrasonic signal by applying one or more pulses to an ultrasonic oscillator of a transducer. Once generated, the ultrasonic signal is reflected by a target (such as structures in a human body) and is received as an echo signal by the transducer. The transducer converts the echo signal into an electrical signal, and then requires a high bandwidth communication channel on the order of multiple gigabytes, to wirelessly transmit the electrical signal, and also so as to not interfere with other wireless electronic apparatuses during wireless transmission of the echo signal. 
         [0042]    To this end, according to embodiments of the present invention, an echo signal is wirelessly transmitted via a wireless network that uses millimeter waves. For example, a wireless communication technique based on the WiGig standard of the Wireless Gigabit Alliance (WGA) may be used. 
         [0043]    The WiGig standard is sufficient to transmit an echo signal that has been converted into digital data because the WiGig standard supports data transmission rates up to 7 Gbps, and may steer a signal direction by using the directionality of beams to minimize interference with other systems. The WiGig standard as a local-distance wireless communication standard is also generally suitable for ultrasonic test environments where a probe and an ultrasonic imaging apparatus are close to each other, and using the WiGig standard consumes less power than other wireless communication standards and thus may minimize the weight and size of battery which is to be built into the probe. The dashed line circle in  FIG. 2  enclosing probe  220  and the ultrasonic imaging apparatus  210  denotes a wireless communication network with which the probe and imaging apparatus communicate with each other, and may be a personal basic service set (PBSS) of the WiGig standard, as explained in more detail below. 
         [0044]      FIG. 3  is a flowchart of a communication process performed by a probe, according to an embodiment of the present invention. 
         [0045]    In operation  301 , the probe performs a procedure in order to become associated with a PBSS mmWave-based wireless network. In the PBSS, at least one station needs to operate as a PBSS control point (PCP) that manages the PBSS. However, the probe is limited in its size and weight, and thus it may be preferred that the ultrasonic imaging apparatus  210  may operate as the PCP. Alternatively, both the ultrasonic imaging apparatus and the probe may operate as a station, and another device may operate as the PCP in the PBSS. 
         [0046]    In operation  302 , the probe generates a data frame with a format suitable for the mmWave-based wireless network, by using an echo signal received via the transducer. 
         [0047]    In operation  303 , the probe transmits the data frame to the ultrasonic imaging apparatus using a signal in a 60 GHz frequency band. The ultrasonic imaging apparatus (such as  210  of  FIG. 2 ) receives the data frame, generates therefrom an ultrasonic image via signal processing, and displays the ultrasonic image. 
         [0048]      FIG. 4  is a flowchart of a process in which the probe performs pairing with the ultrasonic imaging apparatus, according to an embodiment of the present invention. 
         [0049]    The PBSS is an ad-hoc structure that performs direct communication between stations without passing through a PCP. Accordingly, the probe and the ultrasonic imaging apparatus need to be subjected to a process of recognizing themselves as peer devices and setting a communication protocol to perform mutual communication. This process is referred to as pairing. A push button configuration (PBC) method may be used to perform pairing between the probe and the ultrasonic imaging apparatus. In other words, when a user pushes pairing buttons included in the probe and the ultrasonic imaging apparatus simultaneously (or within a short time interval therebetween), the probe and the ultrasonic imaging apparatus are paired. 
         [0050]    In operation  401 , when a user command for making a pairing request is input, that is, when a pairing button is pressed, the probe receives a mmWave beacon frame (hereinafter, referred to as a beacon frame) of the PBSS not yet associated. Before the user command for making a pairing request is input, the probe is not associated with the PBSS of the ultrasonic imaging apparatus, and thus does not parse a beacon frame broadcast from the PBSS to which the ultrasonic imaging apparatus belongs, but discards it. However, when a user presses the pairing buttons, the probe starts monitoring an externally received beacon frame. 
         [0051]    In operation  402 , the probe detects the ultrasonic imaging apparatus which is to be paired with the probe by using first pairing information included in the beacon frame. It is assumed that the ultrasonic imaging apparatus has already belonged to the PBSS, and the ultrasonic imaging apparatus may operate as a PCP or a general station rather than the PCP in the PBSS. When a user presses the pairing button included in the ultrasonic imaging apparatus to perform pairing, the PCP of the PBSS broadcasts the first pairing information, representing that the ultrasonic imaging apparatus has requested pairing, via a beacon frame. The first pairing information may include PBC information representing that the pairing button of the ultrasonic imaging apparatus has been pressed, and a medium access control (MAC) address of the ultrasonic imaging apparatus. 
         [0052]    In operation  403 , the probe is associated with the PBSS of the ultrasonic imaging apparatus by using Basic Service Set ID (BSSID) included in the beacon frame. Although the probe is associated with the PBSS after determining a peer device (operation  402 ) in the present embodiment, operation  403  may be performed before operation  402 . 
         [0053]    In operation  404 , the probe transmits second pairing information to the ultrasonic imaging apparatus. The second pairing information represents that the probe has requested pairing, and may include PBC information representing that the pairing button of the probe has been pressed, and a MAC address of the probe. 
         [0054]      FIG. 5  is a flowchart of a pairing process according to another embodiment of the present invention where it is assumed that both an ultrasonic imaging apparatus  510  and a probe  520  are initially driven, that is, the ultrasonic imaging apparatus  510  did not yet generate any PBSSs and the probe  520  is not yet associated with any PBSSs. 
         [0055]    In a first operation, a pairing button included in the ultrasonic imaging apparatus  510  is pressed by a user. 
         [0056]    In a second operation, the ultrasonic imaging apparatus  510 , in response to the user pressing the pairing button, generates a PBSS and becomes operational so as to serve as a PCP of the PBSS. 
         [0057]    In a third operation, the ultrasonic imaging apparatus  510  broadcasts a beacon frame including first pairing information PI 1 . The first pairing information PI 1  may include PBC information representing that the pairing button included in the ultrasonic imaging apparatus  510  has been pressed, and a MAC address of the ultrasonic imaging apparatus  510 . 
         [0058]    At this time, even when the probe  520  is turned on and is physically located at a distance capable of receiving a beacon of the ultrasonic imaging apparatus  510 , the probe  520  does not parse the beacon frame but discards it because the probe  520  is not yet associated with the PBSS of the ultrasonic imaging apparatus  510 . Accordingly, the probe  520  does not react to the beacon frame received in the third operation. 
         [0059]    Although the first pairing information PI 1  is broadcast via the beacon frame in a beacon section in the present embodiment, the ultrasonic imaging apparatus  510  may broadcast the first pairing information PI 1  in a time section other than the beacon section. 
         [0060]    In a fourth operation, a pairing button included in the probe  520  is pressed by the user. Accordingly, the probe  520  starts monitoring externally received beacon frames without discarding them. 
         [0061]    In a fifth operation, the ultrasonic imaging apparatus  510  re-broadcasts the beacon frame including the first pairing information PI 1 . 
         [0062]    In a sixth operation, the probe  520  recognizes the ultrasonic imaging apparatus  510  as a peer device. 
         [0063]    In a seventh operation, the probe  520  transmits an association request frame requesting association with the PBSS to the ultrasonic imaging apparatus  510 . 
         [0064]    In an eighth operation, the ultrasonic imaging apparatus  510  transmits to the probe  520  an association response frame approving the association request of the probe  520 . 
         [0065]    In a ninth operation, the probe  520  transmits the first pairing information PI 1  and second pairing information PI 2  to the ultrasonic imaging apparatus  510 . The second pairing information PI 2  may include PBC information representing that the pairing button included in the probe  520  has been pressed, and a MAC address of the probe  520 . 
         [0066]    In a tenth operation, the ultrasonic imaging apparatus  510  recognizes the probe  520  as a peer device by analyzing the second pairing information PI 2 . 
         [0067]      FIG. 6  is a flowchart of a pairing process according to another embodiment of the present invention where, as in the embodiment of  FIG. 5 , it is assumed that both an ultrasonic imaging apparatus  610  and a probe  620  are initially driven. 
         [0068]    In a first operation, a pairing button included in the ultrasonic imaging apparatus  610  is pressed by a user. 
         [0069]    In a second operation, the ultrasonic imaging apparatus  610  generates a PBSS and serves as a PCP of the PBSS. 
         [0070]    In a third operation, the ultrasonic imaging apparatus  610  broadcasts a beacon frame including first pairing information PI 1 . The first pairing information PI 1  may include PBC information representing that the pairing button included in the ultrasonic imaging apparatus  610  has been pressed, and a MAC address of the ultrasonic imaging apparatus  610 . 
         [0071]    At this time, even when the probe  620  is turned on and is physically located at a distance capable of receiving a beacon of the ultrasonic imaging apparatus  610 , the probe  620  does not parse the beacon frame but discards it because the probe  620  is not yet associated with the PBSS of the ultrasonic imaging apparatus  610 . Accordingly, the probe  620  does not react to the beacon frame received in the third operation. 
         [0072]    In a fourth operation, a pairing button included in the probe  620  is pressed by the user. Accordingly, the probe  620  starts monitoring externally received beacon frames without discarding them. 
         [0073]    In a fifth operation, the ultrasonic imaging apparatus  610  re-broadcasts the beacon frame including the first pairing information PI 1 . 
         [0074]    In a sixth operation, the probe  620  recognizes the ultrasonic imaging apparatus  610  as a peer device. 
         [0075]    In a seventh operation, the probe  620  transmits the first pairing information PI 1  and second pairing information PI 2  to the ultrasonic imaging apparatus  610 . The second pairing information PI 2  may include PBC information representing that the pairing button included in the probe  620  has been pressed, and a MAC address of the probe  620 . 
         [0076]    In an eighth operation, the ultrasonic imaging apparatus  610  recognizes the probe  620  as a peer device by analyzing the second pairing information PI 2 . 
         [0077]    In a ninth operation, the probe  620  transmits an association request frame requesting association with the PBSS to the ultrasonic imaging apparatus  610 . 
         [0078]    In a tenth operation, the ultrasonic imaging apparatus  610  transmits to the probe  620  an association response frame approving the association request of the probe  620 . 
         [0079]    As such, in the embodiment of  FIG. 6 , in contrast with the embodiment of  FIG. 5 , the probe  620  is associated with the PBSS after transmitting the second pairing information PI 2  to the ultrasonic imaging apparatus  610 . 
         [0080]      FIG. 7  is a flowchart of a pairing process according to another embodiment of the present invention where it is assumed that, while an ultrasonic imaging apparatus  710  is operating as a PCP of a PBSS, a probe  720  is initially driven. 
         [0081]    In a first operation, a pairing button included in the ultrasonic imaging apparatus  710  is pressed by a user. 
         [0082]    In a second operation, the ultrasonic imaging apparatus  710  broadcasts a beacon frame including first pairing information PI 1 . The first pairing information PI 1  may include PBC information representing that the pairing button included in the ultrasonic imaging apparatus  710  has been pressed, and a MAC address of the ultrasonic imaging apparatus  710 . 
         [0083]    At this time, even when the probe  720  is turned on and is physically located at a distance capable of receiving a beacon frame of the ultrasonic imaging apparatus  710 , the probe  720  does not parse the beacon frame but discards it because the probe  620  is not yet associated with the PBSS of the ultrasonic imaging apparatus  710 . Accordingly, the probe  720  does not react to the beacon frame received in the second operation. 
         [0084]    In a third operation, a pairing button included in the probe  720  is pressed by the user. Accordingly, the probe  720  starts monitoring externally received beacon frames without discarding them. 
         [0085]    In a fourth operation, the ultrasonic imaging apparatus  710  re-broadcasts the beacon frame including the first pairing information PI 1 . 
         [0086]    In a fifth operation, the probe  720  recognizes the ultrasonic imaging apparatus  710  as a peer device. 
         [0087]    In a sixth operation, the probe  520  is associated with the PBSS of the ultrasonic imaging apparatus  710 . 
         [0088]    In a seventh operation, the probe  520  transmits second pairing information PI 2  to the ultrasonic imaging apparatus  710 . The second pairing information PI 2  may include PBC information representing that the pairing button included in the probe  720  has been pressed, and a MAC address of the probe  720 . 
         [0089]    In an eighth operation, the ultrasonic imaging apparatus  710  recognizes the probe  720  as a peer device by analyzing the second pairing information PI 2 . 
         [0090]      FIG. 8  is a flowchart of a pairing process according to another embodiment of the present invention where, similar to the embodiment of  FIG. 7 , it is assumed that while an ultrasonic imaging apparatus  810  is already operating as a PCP of a PBSS, a probe  820  is initially driven. 
         [0091]    In a first operation, a pairing button included in the ultrasonic imaging apparatus  810  is pressed by a user. 
         [0092]    In a second operation, the ultrasonic imaging apparatus  810  broadcasts a beacon frame including first pairing information PI 1 . The first pairing information PI 1  may include PBC information representing that the pairing button included in the ultrasonic imaging apparatus  810  has been pressed, and a MAC address of the ultrasonic imaging apparatus  810 . 
         [0093]    At this time, even when the probe  820  is turned on and is physically located at a distance capable of receiving a beacon frame of the ultrasonic imaging apparatus  810 , the probe  820  does not parse the beacon frame but discards it because the probe  820  is not yet associated with the PBSS of the ultrasonic imaging apparatus  810 . Accordingly, the probe  820  does not react to the beacon frame received in the second operation. 
         [0094]    In a third operation, a pairing button included in the probe  820  is pressed by the user. Accordingly, the probe  820  starts monitoring externally received beacon frames without discarding them. 
         [0095]    In a fourth operation, the ultrasonic imaging apparatus  810  re-broadcasts the beacon frame including the first pairing information PI 1 . 
         [0096]    In a fifth operation, the probe  820  recognizes the ultrasonic imaging apparatus  810  as a peer device. 
         [0097]    In a sixth operation, the probe  820  is associated with the PBSS of the ultrasonic imaging apparatus  810  and at the same time transmits second pairing information PI 2  to the ultrasonic imaging apparatus  810 . In other words, the probe  820  carries the second pairing information PI 2  in an association request frame and transmits the association request frame including the second pairing information PI 2  to the ultrasonic imaging apparatus  810 . 
         [0098]    In a seventh operation, the ultrasonic imaging apparatus  810  recognizes the probe  820  as a peer device by analyzing the second pairing information PI 2 . 
         [0099]      FIG. 9  is a flowchart of a pairing process according to another embodiment of the present invention. In the embodiment of  FIG. 9 , it is assumed that an ultrasonic imaging apparatus  910  is operating as a general station rather than a PCP  920  of a PBSS even when the ultrasonic imaging apparatus  910  already belongs to the PBSS, and that a probe  930  is initially driven. 
         [0100]    In a first operation, a pairing button included in the ultrasonic imaging apparatus  910  is pressed by a user. 
         [0101]    In a second operation, the ultrasonic imaging apparatus  910  transmits to a PCP  920  first pairing information PI 1  representing that the ultrasonic imaging apparatus  910  needs to perform pairing. The first pairing information PI 1  may include PBC information representing that the pairing button included in the ultrasonic imaging apparatus  910  has been pressed, and a MAC address of the ultrasonic imaging apparatus  910 . 
         [0102]    In a third operation, the PCP  920  broadcasts a beacon frame including the first pairing information PI 1 . Since the probe  930  is not yet associated with the PBSS, the probe  930  does not parse the beacon frame but discards the same. As described above, the PCP  920  may broadcast the first pairing information PI 1  in a time section other than the beacon section. 
         [0103]    In a fourth operation, a pairing button included in the probe  930  is pressed by the user. Accordingly, the probe  930  starts monitoring externally received beacon frames. 
         [0104]    In a fifth operation, the PCP  920  re-broadcasts the beacon frame including the first pairing information PI 1 . 
         [0105]    In a sixth operation, the probe  930  recognizes the ultrasonic imaging apparatus  910  as a peer device of the probe  930  by referring to the first pairing information PI 1 . 
         [0106]    In a seventh operation, the probe  930  is associated with the PBSS of the PCP  920 . 
         [0107]    In an eighth operation, the probe  930  transmits to the PCP  920  second pairing information PI 2  representing that the probe  930  itself is requested by the user to perform pairing. The second pairing information PI 2  may be included in an association request frame that the probe  930  transmits to the PCP  920  while the probe  930  is being associated with the PBSS. 
         [0108]    In a ninth operation, the PCP  920  broadcasts a beacon frame including the first pairing information PI 1  and the second pairing information PI 2 . 
         [0109]    In a tenth operation, in response to the beacon frame including the first pairing information PI 1  and the second pairing information PI 2 , the ultrasonic imaging apparatus  910  recognizes the probe  930  as a peer device of the ultrasonic imaging apparatus  910 . 
         [0110]    As such, according to the embodiments of the present invention, pairing between an ultrasonic imaging apparatus and a probe is performed by a user simply pressing buttons included in an ultrasonic imaging apparatus and a probe. Thus the probe portion of an ultrasound imaging system may be simply and easily replaced, if necessary, while the existing ultrasonic imaging apparatus is being used. 
         [0111]      FIG. 10  is a flowchart of a process of controlling a link margin, according to an embodiment of the present invention. 
         [0112]    The link margin is information used to determine a status of the communication link, and denotes a power level of a reception signal that is required by a current modulation technique. When the value of the link margin is positive, the power of the reception signal is more than necessary. When the value of the link margin is negative, the power of the reception signal is insufficient. 
         [0113]    In operation  1010 , a probe forms a communication link with an ultrasonic imaging apparatus via a PBSS. The formation of the communication link denotes completion of preparations for a communication with a peer device, including pairing. 
         [0114]    In operation  1020 , the probe receives a link margin response frame including information about the link margin (hereinafter, also referred to as link margin information) from the ultrasonic imaging apparatus, and extracts the link margin information from the link margin response frame. A format of the link margin response frame will be described later with reference to  FIG. 11 . 
         [0115]    The ultrasonic imaging apparatus calculates the link margin information based on a data frame that the probe transmits in the 60 GHz band, and then informs the probe of the calculated link margin. The link margin response frame may be received every time the probe requests the link margin response frame, or may be transmitted by the ultrasonic imaging apparatus periodically without special requests or whenever the state of a link degrades. 
         [0116]    In operation  1030 , the probe adjusts the link margin based on the link margin information. To adjust the link margin, the probe may perform at least one of a change in transmission power, a change in a modulation and coding scheme (MCS), a change in beam forming, and a change in channel frequency within the 60 GHz band. 
         [0117]      FIG. 11  illustrates a format of a link margin response frame  1100  according to an embodiment of the present invention. 
         [0118]    As illustrated in  FIG. 11 , the link margin response frame  1100  includes a category field  1101 , an action field  1102 , a transmission number field  1103 , a preferred action field  1104 , a link margin element field  1105 , an unsolicited field  1106 , and a data frame ID field  1107 . 
         [0119]    The category field  1101  represents what kind of frame the link margin response frame  1100  belongs to. According to the present embodiment, the category field  1101  may indicate that the link margin response frame  1100  is a control frame. 
         [0120]    The action field  1102  indicates that the link margin response frame  1100  is a link margin response frame categorized into a control frame which is the frame type determined by the category field  1101 . 
         [0121]    The transmission number field  1103  indicates the number of times the link margin response frame  1100  is transmitted from an ultrasonic imaging apparatus to a probe. 
         [0122]    The preferred action field  1104  indicates one operation that the ultrasonic imaging apparatus requests from among a change in transmission power, a change in MCS, beam forming, and a channel frequency change. When the link margin response frame  1100  including the preferred action field  1104  is received, the probe may perform the operation indicated by the preferred action field  1104  or may perform an operation for margin adjustment independently without respect to the preferred action field  1104 . Although the preferred action field  1104  is illustrated as an independent field of the link margin response frame  1100  in  FIG. 11 , the preferred action field  1104  may be a subfield of the link margin element field  1105 . 
         [0123]    The link margin element field  1105  includes the link margin information and is divided into an element ID field  1108 , a length field  1109 , a MCS field  1110 , and a link margin field  1111 . 
         [0124]    The element ID field  1108  indicates that the link margin element field  1105  is a field including the link margin information. 
         [0125]    The length field  1109  indicates a length of the link margin element field  1105 . 
         [0126]    The MCS field  1110  indicates an index representing an MCS which is to be changed, when the preferred action field  1104  indicates that the ultrasonic imaging apparatus requests a change in the MCS. 
         [0127]    The link margin field  1111  records information about the link margin calculated by the ultrasonic imaging apparatus. 
         [0128]    The unsolicited field  1106  represents whether the link margin response frame  1100  is received in response to a request frame of the probe. For example, when the link margin response frame  1100  is received in response to a request of the probe, the unsolicited field  1106  may record 0, and otherwise, the unsolicited field  1106  may record a value other than 0. If the probe transmits a link margin request frame (not shown) to the ultrasonic imaging apparatus to request the link margin response frame  1100 , the link margin request frame may include at least one of a category field indicating the kind of frame, an action field indicating that the link margin response frame  1100  is a link margin request frame from among frames categorized into the kind of frame indicated by the category field, and a transmission number field representing the number of times the link margin request frame is transmitted. 
         [0129]    The data frame ID field  1107  includes a sequence number of a data frame used when the ultrasonic imaging apparatus calculates the link margin. Through these pieces of information, the probe can recognize a time for calculating the link margin, and thus may adequately control the state of a communication link. 
         [0130]      FIG. 12  is a block diagram of a structure of a probe apparatus  1200  according to another embodiment of the present invention. 
         [0131]    As illustrated in  FIG. 12 , the probe apparatus  1200  includes a transducer  1201 , a receiver beam former  1202 , a user interface  1203 , and a wireless transceiver module  1250 . 
         [0132]    The wireless transceiver module  1250  includes an association performing unit  1251 , a frame generation unit  1252 , a margin information processing unit  1253 , a margin control unit  1254 , a beam forming unit  1255 , a wireless communication unit  1256 , and a link formation unit  1260 . The link formation unit  1260  includes a pairing request unit  1261 , a peer determination unit  1262 , and a beacon monitoring unit  1263 . The wireless transceiver module  1250  may further include other various components such as a battery, an analog to digital converter (ADC), and a low noise amplifier (LNA). This will be apparent to one of ordinary skill in the art, thus no further descriptions thereof are provided. 
         [0133]    The transducer  1201  converts an ultrasonic echo signal received from a test target into an electrical signal, and the receiver beam former  1202  gathers multiple channels of echo signals (more specifically, digital data into which the echo signals are converted) received from oscillators arranged in an array or matrix form in the transducer  1201 . 
         [0134]    The wireless transceiver module  1250  performs procedures necessary for transmitting an echo signal to an ultrasonic imaging apparatus  1280  in the 60 GHz frequency band. The association performing unit  1251  performs a procedure for associating the probe apparatus  1200  using a mmWave-based wireless network. As described above, the mmWave-based wireless network may be a PBSS that follows the WiGig standard of WGA. When the probe  1200  and the ultrasonic imaging apparatus  1280  perform communications via the PBSS, the ultrasonic imaging apparatus  1280  may operate as a PCP instead of the probe  1200 , in order that the size and weight of the probe  1200  can be kept low by not including the components therein which would be necessary to allow the probe to be a PCP. 
         [0135]    The frame generation unit  1252  generates a data frame with a format suitable for the mmWave-based wireless network, by using the echo signal received via the transducer  1201 . 
         [0136]    The wireless communication unit  1256  transmits the data frame generated by the frame generation unit  1252  to the ultrasonic imaging apparatus  1280  via the 60 GHz frequency band. 
         [0137]    The beam forming unit  1255  performs mmWave beamforming together with the ultrasonic imaging apparatus  1280 . In other words, the beam forming unit  1255  performs procedures necessary for efficiently transmitting and receiving data to and from the ultrasonic imaging apparatus  1280  by using mmWaves, such as by using sector level sweeping and beam refinement techniques, well known to those of ordinary skill in the art. 
         [0138]    The link formation unit  1260  forms a link with the ultrasonic imaging apparatus  1280 . When a user command for making a pairing request is received via the user interface  1203 , the beacon monitoring unit  1263  receives a mmWave beacon of the PBSS to which the ultrasonic imaging apparatus  1280  belongs. The reception of the user command for making a pairing request denotes not only physical reception but also requests an operation of parsing and analyzing a received beacon frame. 
         [0139]    Accordingly, the peer determination unit  1262  detects the ultrasonic imaging apparatus  1280  which is to be paired with the probe  1200  by using first pairing information included in the mmWave beacon. The first pairing information represents that the ultrasonic imaging apparatus  1280  has been requested by a user to perform pairing, and may include the MAC address of the ultrasonic imaging apparatus  1280  and PBC information representing that a PBC-type pairing button included in the ultrasonic imaging apparatus  1280  has been pressed. 
         [0140]    The pairing request unit  1261  transmits second pairing information representing that the probe  1200  requests pairing, to the ultrasonic imaging apparatus  1280  via the PBSS. The second pairing information may include the MAC address of the probe  1200  and PBC information representing that a PBC-type pairing button included in the probe  1200  has been pressed. 
         [0141]    The margin information processing unit  1253  extracts information about a link margin of a communication link from the ultrasonic imaging apparatus  1280 . The link margin information may be included in a link margin response frame that the ultrasonic imaging apparatus  1280  transmits to the probe  1200  in response to a request of the probe  1200  or periodically without requests or when the state of the communication link degrades. 
         [0142]    The margin control unit  1254  controls the link margin based on the link margin response frame. More specifically, the margin control unit  1254  may adjust the link margin by performing at least one of a change in transmission power, a change in a MCS, a change in beam forming, and a change in a channel frequency within the 60 GHz frequency band. 
         [0143]    The above-described method and apparatus embodiments of the present invention can be realized in hardware or as software or computer code that can be stored in a recording medium such as a CD ROM, an RAM, a floppy disk, a hard disk, a DVD or a magneto-optical disk or downloaded over a network, so that the methods described herein can be rendered in such software using a general purpose computer, or a special processor or in programmable or dedicated hardware, such as an ASIC or FPGA. As would be understood in the art, the computer, the processor or the programmable hardware include memory components, e.g., RAM, ROM, Flash, etc. that may store or receive software or computer code that when accessed and executed by the computer, processor or hardware implement the processing methods described herein. 
         [0144]    While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents.